JP2010008061A - Physical quantity sensor and physical quantity measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend a measurement range, improve a resolution, stabilize the measurement accuracy, and easily extract a signal. <P>SOLUTION: A physical quantity sensor includes: a wavelength variable mechanism for controlling an oscillation wavelength by adjusting a length of a resonator in response to a diaphragm control signal; a wavelength variable semiconductor laser 1 for irradiating an object 11 with a laser light; a photodiode 2 for converting an optical output from the semiconductor laser 1 into an electrical signal; a laser driver 4 for supplying a drive current to the semiconductor laser 1; a current-voltage conversion amplifier 5 for converting an output current from the photodiode 2 into a voltage, and amplifying it; a count section 7 for counting the number of interference waveforms included in an output voltage from a filter circuit 6; a calculation section 8 for calculating a distance between the object 11 and a speed of the object 11 from the number of the interference waveforms; and a diaphragm driver 10 for modulating the oscillation wavelength of the semiconductor laser 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a physical quantity sensor and a physical quantity measurement method for measuring a physical quantity such as a distance to an object and a speed of an object from information on interference caused by a self-coupling effect between laser light emitted from a semiconductor laser and return light from the object. Is.

  There are two types of laser sensors using the self-coupling effect (self-mixing effect) of a semiconductor laser, a fixed wavelength type and a wavelength modulation type. A fixed wavelength sensor is disclosed in, for example, Patent Document 1, and a wavelength modulation sensor is disclosed in, for example, Patent Document 2.

  In the fixed wavelength type sensor, the external interference length between the active layer end face or reflective surface of the laser element and the reflective surface of the object changes with the displacement of the object to be measured. By taking out the generated interference as a self-coupling signal, for example, the displacement of the object is measured. However, such a fixed wavelength type sensor has a problem that it is very difficult to separate the fluctuation or disturbance light of the laser light applied to the object from the self-coupled signal.

  On the other hand, a wavelength modulation type sensor can generate a self-coupled signal by changing the external interference state even when the object to be measured is stationary by modulating the laser oscillation wavelength. Since regularity can be given to the generation period, the self-coupled signal and the disturbance can be easily separated. More specifically, the case where the oscillation wavelength is modulated will be described. When the laser oscillation wavelength is changed while irradiating the laser beam from the laser to the object, the oscillation wavelength changes from the minimum oscillation wavelength to the maximum oscillation wavelength (or The displacement of the object during the change from the maximum oscillation wavelength to the minimum oscillation wavelength is reflected in the number of self-coupled signals. For example, if the distance to the object is L1 and the number of self-coupling signals is 10, the number of self-coupling signals is 5 at half the distance L2. That is, when the laser oscillation wavelength is changed for a certain time, the number of self-coupled signals changes in proportion to the measurement distance. Therefore, the distance can be easily measured by converting the optical output of the laser into an electrical signal and extracting the self-coupled signal from the electrical signal.

Japanese Patent No. 3282746 Japanese Patent No. 2733990

  In a wavelength modulation type sensor, an injection current is modulated to cause a change in interference length due to linear expansion of the laser element, thereby modulating the oscillation wavelength. Therefore, in the wavelength modulation type sensor, in the distance measurement in which the wavelength change amount is proportional to the distance resolution, the change in the laser light output due to the injection current modulation becomes large, and a small self-coupled signal can be extracted from the change in the light output. Since it is not easy, there is a problem in that the distance resolution and the self-coupled signal extraction characteristic conflict. Furthermore, in the wavelength modulation type sensor, the change in the light output of the laser causes the change in the intensity of the return light from the object, which adversely affects the stability of the intensity of the self-coupled signal. was there.

  The present invention has been made to solve the above-described problem, and a physical quantity sensor and a physical quantity measuring method capable of realizing a long measurement range, high resolution, stable measurement accuracy, and ease of signal extraction. The purpose is to provide.

  The physical quantity sensor of the present invention includes a wavelength tunable mechanism capable of controlling the oscillation wavelength by adjusting the resonator length according to the control signal, and a wavelength tunable semiconductor laser that emits a laser beam to a measurement target, and is driven by this semiconductor laser. A laser driver for supplying current to oscillate the semiconductor laser; oscillation wavelength modulating means for supplying the control signal to the semiconductor laser to modulate the oscillation wavelength of the semiconductor laser; and laser light emitted from the semiconductor laser Detection means for detecting an electrical signal including an interference waveform caused by a self-coupling effect between the measurement light and the return light from the measurement target, and the physical quantity of the measurement target from the information of the interference waveform included in the output signal of the detection means And a measuring means for measuring.

Further, in one configuration example of the physical quantity sensor of the present invention, the oscillation wavelength modulation means includes a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and a period in which the oscillation wavelength continuously decreases monotonously. The semiconductor laser is operated so that at least the second oscillation period including at least alternately exists, and the measuring means determines the number of the interference waveforms included in the output signal of the detecting means as the number of the semiconductor laser. A signal extracting means for counting each of the counting period on the oscillation wavelength increasing side and the counting period on the decreasing side of the oscillation wavelength, and an arithmetic means for calculating the physical quantity of the measurement object from the counting result of the signal extracting means. It is a feature.
Also, in one configuration example of the physical quantity sensor of the present invention, the signal extraction unit calculates the number of the interference waveforms included in the output signal of the detection unit, the counting period on the increase side of the oscillation wavelength of the semiconductor laser, and the oscillation Counting means for counting each of the counting periods on the wavelength decreasing side, and a period measuring means for measuring the period of the interference waveform during the counting period in which the counting means counts the number of interference waveforms each time the interference waveform is input; Frequency distribution creating means for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of the period measuring means, and representative value calculating means for calculating a representative value of the period distribution of the interference waveform from the frequency distribution From the frequency distribution, a total sum Ns of class frequencies that is less than or equal to a first predetermined number times the representative value and a total frequency Nw of class frequencies that are greater than or equal to the second predetermined number times the representative value are obtained. ,these The counting result of the counting means is corrected on the basis of the frequencies Ns and Nw, and is characterized in that comprising a correction value calculation means for outputting a count result after correction.
In one configuration example of the physical quantity sensor of the present invention, the physical quantity of the measurement target is at least one of a distance from the measurement target and a speed of the measurement target.
In one configuration example of the physical quantity sensor of the present invention, the laser driver supplies the pulsed drive current to the semiconductor laser to cause the semiconductor laser to emit light in pulses.

In addition, one configuration example of the physical quantity sensor of the present invention further includes a return light detection light receiver that receives the return light from the measurement target and converts it into an electrical signal, and an output signal of the return light detection light receiver. And an object detection means for determining whether or not a measurement target exists in the radiation direction of the laser light.
In addition, one configuration example of the physical quantity sensor of the present invention further includes light output control means for controlling a drive current supplied from the laser driver to the semiconductor laser so that the light output of the semiconductor laser becomes constant. It is characterized by this.
Further, in one configuration example of the physical quantity sensor of the present invention, the drive current supplied from the laser driver to the semiconductor laser is further controlled so that the optical output of the semiconductor laser becomes an appropriate value according to the ambient temperature. And a light output control means.
In addition, one configuration example of the physical quantity sensor of the present invention further includes a return light detection light receiver that receives return light from the measurement target and converts it into an electrical signal, and an output signal of the return light detection light receiver. And a light output control means for controlling a drive current supplied from the laser driver to the semiconductor laser so that the amount of light returned from the measurement object is constant.

In addition, one configuration example of the physical quantity sensor of the present invention further includes a reference signal generating unit that generates a reference signal, a voltage controlled oscillation unit that generates a modulation signal, and a modulation included in the outputs of the reference signal and the detecting unit. A phase control means for controlling the voltage-controlled oscillation means so that the phase of the modulation signal is synchronized with the reference signal or the phase difference between the modulation signal and the reference signal is constant. The laser driver modulates the drive current with a modulation signal output from the voltage controlled oscillation means, and the oscillation wavelength modulation means synchronizes the control signal with the reference signal.
Further, in one configuration example of the physical quantity sensor of the present invention, the interference waveform included in the output signal of the detection unit is further averaged over a plurality of counting periods on the oscillation wavelength increasing side and the oscillation wavelength An averaging processing unit that averages a plurality of counting periods on the decreasing side is provided, and the oscillation wavelength modulation unit includes a first oscillation period that includes at least a period in which the oscillation wavelength continuously increases monotonously and the oscillation wavelength continuously. The semiconductor laser is operated so that second oscillation periods including at least a monotonically decreasing period alternately exist, and the measuring means includes the number of the interference waveforms included in the output signal of the detecting means. Is output from the signal extraction means for counting each of the counting period on the increase side of the oscillation wavelength and the counting period on the decrease side of the oscillation wavelength, and the averaging processing means. A calculation means for calculating the physical quantity of the measurement object from the numerical results, the averaging processing means, the averaging calculation means for performing the averaging, and the number of interference waveforms after the averaging, When the count result after the averaging process for counting each of the counting period on the oscillation wavelength increasing side and the counting period on the decreasing side of the oscillation wavelength, and the change in the counting result output from the signal extraction means are within a predetermined range, The counting result output from the counting means after the averaging process is output to the arithmetic means, and when the change in the counting result output from the signal extraction means exceeds a predetermined range, the count output from the signal extraction means It comprises state determination means for outputting the result to the calculation means.

  Also, in one configuration example of the physical quantity sensor of the present invention, the signal extraction unit calculates the number of the interference waveforms included in the output signal of the detection unit, the counting period on the increase side of the oscillation wavelength of the semiconductor laser, and the oscillation Each time the interference waveform is input, the pre-averaging counting means for counting each of the counting periods on the wavelength decreasing side, and the period of the interference waveform in the counting period during which the pre-averaging counting means counts the number of interference waveforms A period measurement means for measuring the frequency, a frequency distribution creation means for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of the period measurement means, and a representative distribution of the period of the interference waveform from the frequency distribution A representative value calculating means for calculating a value; a sum Ns of frequencies of a class that is equal to or less than a first predetermined number times the representative value; and a class that is equal to or greater than a second predetermined number times the representative value from the frequency distribution. Of frequency A correction value calculating means for obtaining a sum Nw, correcting the counting result of the pre-averaging processing means based on these frequencies Ns and Nw, and outputting the corrected counting result to the averaging processing means. The state determination means observes a change in the representative value of the period distribution calculated by the signal extraction means instead of observing a change in the counting result output from the signal extraction means, and changes the representative value. Is output from the signal extraction means when the change in the representative value exceeds a predetermined range. It comprises state determination means for outputting the counting result to the calculation means.

Further, in one configuration example of the physical quantity sensor of the present invention, the phase change of the interference waveform included in the output signal of the detection means is further detected so that the rate of change of the oscillation wavelength of the semiconductor laser becomes constant. And a phase detecting means for controlling a control signal supplied from the oscillation wavelength modulating means to the semiconductor laser.
In one configuration example of the physical quantity sensor of the present invention, the post-averaging counting unit counts the interference waveform after the averaging in units of decimals.
In one configuration example of the physical quantity sensor of the present invention, the laser driver supplies the semiconductor laser with the driving current in the vicinity of a threshold current of laser oscillation.

  In addition, the physical quantity measurement method of the present invention includes a wavelength variable mechanism capable of controlling the oscillation wavelength by adjusting the resonator length according to the control signal, and supplies a drive current to the wavelength variable semiconductor laser that emits laser light to the measurement target. An oscillation procedure for supplying and oscillating the semiconductor laser; an oscillation wavelength modulation procedure for supplying the control signal to the semiconductor laser to modulate an oscillation wavelength of the semiconductor laser; a laser beam emitted from the semiconductor laser; From the detection procedure for detecting an electrical signal including an interference waveform caused by the self-coupling effect with the return light from the measurement target, and the information on the interference waveform included in the output signal obtained by this detection procedure, the physical quantity of the measurement target And a measurement procedure for measuring.

  According to the present invention, the optical output and the oscillation wavelength can be controlled independently by using a wavelength tunable semiconductor laser as the semiconductor laser. As a result, in the present invention, it is possible to maintain a constant high light output while keeping the driving current constant while modulating the oscillation wavelength of the semiconductor laser, so that the measurement range can be extended. Further, in the present invention, since the oscillation wavelength change amount does not depend on the drive current amplitude, the oscillation wavelength change amount can be increased, and the distance resolution can be improved as compared with a sensor using a conventional drive current modulation type VCSEL. Can do. In the present invention, since the optical output of the semiconductor laser is constant, a minute interference waveform superimposed on the optical output of the semiconductor laser can be easily extracted. In the present invention, since the change in the optical output of the semiconductor laser is small, instability of the intensity of the interference waveform due to the change in the optical output can be avoided, and the measurement accuracy can be stabilized.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a physical quantity sensor according to the first embodiment of the present invention. The physical quantity sensor in FIG. 1 is a semiconductor laser 1 that emits laser light to an object 11 to be measured, and a light receiver that is disposed in or near the semiconductor laser 1 and converts the optical output of the semiconductor laser 1 into an electrical signal. And a lens 3 for condensing the light from the semiconductor laser 1 and irradiating the object 11, condensing the return light from the object 11 and entering the semiconductor laser 1, and the semiconductor laser 1. A laser driver 4 that supplies a drive current, a current-voltage conversion amplifier 5 that converts and amplifies the output current of the photodiode 2 into a voltage, and a mode that is a self-coupled signal included in the output voltage of the current-voltage conversion amplifier 5 A signal extraction unit 7 that counts the number of hop pulses (hereinafter referred to as MHP), a calculation unit 8 that calculates the distance to the object 11 and the speed of the object 11 from the number of MHPs, and a calculation unit Having a display device 9 for displaying the result of calculation, and a diaphragm driver 10 is an oscillation wavelength modulation means for modulating the oscillation wavelength of the semiconductor laser 1.

  The photodiode 2 and the current-voltage conversion amplifier 5 constitute detection means. The signal extraction unit 7 and the calculation unit 8 constitute a measuring unit.

  FIG. 2 is a cross-sectional view showing the principal part of the semiconductor laser 1 according to the present embodiment. The semiconductor laser 1 is a type of vertical cavity surface emitting laser (VCSEL) and is a MEMS wavelength tunable device having a vertical cavity wavelength tunable mechanism manufactured using MEMS (Micro Electro Mechanical System) technology. It is a semiconductor laser. This vertical resonator wavelength variable mechanism changes the oscillation wavelength of the laser by controlling the distance (resonator length) between two mirrors constituting the resonator by electrostatic force. In the example of FIG. 2, the mirror layer 1013, the active layer 1014, the electrodes 1015 and 1023, the diaphragm 1022, the optical thin film 1019, and the SOI substrate 1017 constitute a wavelength variable mechanism.

  In FIG. 2, an SOI (Silicon On Insulator) substrate 1017 includes a silicon substrate 1017a, an oxide film 1017b on the silicon substrate 1017a, and a silicon film 1017c on the oxide film 1017b. An electrode 1023 is formed on the lower surface of the silicon substrate 1017a. In the central portion of the oxide film 1017b, an electrostatic drive gap 1021 that is a cavity is formed by etching the oxide film 1017b. This electrostatic drive gap 1021 is formed by sacrificial layer etching of the oxide film 1017b.

  A concave surface portion 1018 is formed on the upper surface of the central portion of the silicon film 1017c. The concave surface portion 1018 is formed by selective polishing of silicon. A portion of the silicon film 1017 c that is thinned by the concave surface portion 1018 constitutes the diaphragm 1022. An optical thin film 1019 made of a dielectric multilayer film is formed on the concave surface portion 1018. The optical thin film 1019 functions as a mirror. An electrode 1015 is formed on the silicon film 1017 c around the concave surface portion 1018. An InP substrate 1012 is provided on the upper surface of the electrode 1015. A gap 1016 is formed at the center of the electrode 1015 so that the concave surface 1018 and the optical thin film 1019 are exposed. The gap 1016 constitutes an optical resonance gap.

  The electrode 1011 is formed on the upper surface of the InP substrate 1012. The mirror layer 1013 is formed inside the InP substrate 1012. This mirror layer 1013 is made of an InP compound. Further, an opening 1121 reaching the mirror layer 1013 is formed on the upper surface of the InP substrate 1012. The opening 1121 becomes a laser beam emission hole. The active layer 1014 is formed on the lower surface of the InP substrate 1012 so as to be in contact with the mirror layer 1013. The above-described gap portion 1016 is formed so that the lower surface of the central portion of the active layer 1014 is exposed.

  In the semiconductor laser 1 as described above, the optical resonator has a structure in which an InP active layer 1014 and a gap 1016 exist between two mirrors composed of a mirror layer 1013 and an optical thin film 1019. .

  The operation of the semiconductor laser 1 will be described. By applying a voltage between the electrode 1011 and the electrode 1015, current is injected into the active layer 1014, atoms included in the active layer 1014 are excited, and light is emitted. This light is reflected between the mirror layer 1013 and the optical thin film 1019, thereby causing laser oscillation. The laser light emitted from the mirror layer 1013 is emitted from the opening 1121 to the outside of the semiconductor laser 1 without passing through the InP substrate 1012.

The oscillation wavelength of the emitted laser light is determined by the distance between the mirror layer 1013 and the optical thin film 1019. By applying a voltage between the electrode 1015 and the electrode 1023, an electrostatic force is generated between the silicon diaphragm 1022 and the silicon substrate 1017a, and the diaphragm 1022 moves toward the silicon substrate 1017a. The distance to the thin film 1019 is increased, and the laser oscillation wavelength is shifted to the longer wavelength side. Such an operation makes it possible to change the oscillation wavelength of the laser.
The details of the semiconductor laser 1 as described above are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2005-223111 and 2007-173550.

  In the present embodiment, the photodiode 2 is provided inside the semiconductor laser 1. That is, the photodiode 2 is provided on the upper surface of the central portion of the silicon substrate 1017a so that the light receiving surface is exposed in the electrostatic drive gap 1021. Laser light emitted from the mirror layer 1013 is applied to the object 11. On the other hand, the laser beam emitted from the optical thin film 1019 enters the photodiode 2 through the electrostatic drive gap 1021. Therefore, since the return light or disturbance light from the object 11 does not enter the photodiode 2, the SN ratio (Signal to Noise Ratio) can be improved.

The output of the laser driver 4 is connected to the electrodes 1011 and 1015 of the semiconductor laser 1. The laser driver 4 supplies a constant driving current to the active layer 1014 of the semiconductor laser 1 through the electrodes 1011 and 1015.
The diaphragm driver 10 applies a diaphragm control signal between the electrode 1015 and the electrode 1023 of the semiconductor laser 1. By changing the voltage of the diaphragm control signal, the oscillation wavelength of the semiconductor laser 1 can be changed.

  The diaphragm driver 10 applies a triangular wave diaphragm control signal to the semiconductor laser 1 that repeats voltage increase and decrease at a constant change rate with respect to time. As a result, the semiconductor laser 1 has a first oscillation period P1 in which the oscillation wavelength continuously increases at a constant rate of change in proportion to the magnitude of the diaphragm control signal, and the oscillation wavelength continuously decreases at a constant rate of change. The second oscillation period P2 to be operated is alternately repeated.

  3A is a diagram showing a diaphragm control signal supplied from the diaphragm driver 10 to the semiconductor laser 1, and FIG. 3B is a diagram showing a time change of the oscillation wavelength of the semiconductor laser 1 according to the diaphragm control signal. 3 (C) is a diagram showing a drive current supplied from the laser driver 4 to the semiconductor laser 1, and FIG. 3 (D) is a diagram showing an optical output of the semiconductor laser 1 according to the drive current. In FIG. 3C, the diaphragm control signal is indicated by a broken line 30 in order to facilitate comparison with the diaphragm control signal. In FIG. 3D, the oscillation wavelength is indicated by a broken line 31 for easy comparison with the oscillation wavelength change of the semiconductor laser 1.

  3A to 3D, λa is the minimum value of the oscillation wavelength of the semiconductor laser 1, λb is the maximum value of the oscillation wavelength, and T is the period of the triangular wave. In the present embodiment, the maximum value λb of the oscillation wavelength and the minimum value λa of the oscillation wavelength are always constant, and the difference λb−λa is also always constant.

Laser light emitted from the semiconductor laser 1 is collected by the lens 3 and enters the object 11. The light of the semiconductor laser 1 reflected by the object 11 is collected by the lens 3 and enters the semiconductor laser 1.
The photodiode 2 is disposed in the semiconductor laser 1 or in the vicinity thereof, and converts the optical output of the semiconductor laser 1 into a current.

  The current-voltage conversion amplifier 5 converts the output current of the photodiode 2 into a voltage and amplifies it.

  The signal extraction unit 7 counts the number of MHPs included in the output voltage of the current-voltage conversion amplifier 5 for each of the first counting period Q1 and the second counting period Q2. The signal extraction unit 7 may use a counter composed of logic gates, or may measure the frequency of MHP (that is, the number of MHPs per unit time) using FFT (Fast Fourier Transform). Note that the signal extraction unit 7 may include a band-pass filter for signal extraction or the like as needed, and extract MHP from the output voltage of the current-voltage conversion amplifier 5.

The first counting period Q1 is the same period as the first oscillation period P1, or is included in the first oscillation period P1 and starts after a predetermined time from the start point of the first oscillation period P1. Similarly, the second counting period Q2 is the same period as the second oscillation period P2 or a period that is included in the second oscillation period P2 and starts after a predetermined time from the start time of the second oscillation period P2. is there. The first counting period Q1 and the second counting period Q2 are preferably set so as to exclude the timing of the maximum value and the minimum value of the output voltage of the current-voltage conversion amplifier 5. In this case, the lengths of the first counting period Q1 and the second counting period Q2 are shorter than T / 2.
Since the diaphragm driver 10 notifies whether the current time is the first oscillation period P1 or the second oscillation period P2, the signal extraction unit 7 determines whether the current time is the first counting period Q1 or the second counting period Q2. Can be recognized.

Here, the MHP that is a self-coupled signal will be described. As shown in FIG. 4, when the distance from the mirror layer 1013 to the object 11 is L and the oscillation wavelength of the laser is λ, the return light from the object 11 and the optical resonance of the semiconductor laser 1 are satisfied when the following resonance conditions are satisfied. The laser light in the chamber strengthens and the laser output increases slightly.
L = qλ / 2 (1)
In Formula (1), q is an integer. This phenomenon can be sufficiently observed even when the scattered light from the object 11 is very weak, because the apparent reflectance in the resonator 101 of the semiconductor laser increases, causing an amplification effect.

  FIG. 5 is a diagram showing the relationship between the oscillation wavelength and the output waveform of the photodiode 2 when the oscillation wavelength of the semiconductor laser 1 is changed at a certain rate. When L = qλ / 2 shown in Expression (1) is satisfied, the phase difference between the return light and the laser light in the optical resonator becomes 0 ° (the same phase), and the return light and the optical resonator The laser beam is the most intense, and when L = qλ / 2 + λ / 4, the phase difference is 180 ° (reverse phase), and the return light and the laser beam in the optical resonator are most weakened. Therefore, when the oscillation wavelength of the semiconductor laser 1 is changed, a place where the laser output becomes strong and a place where the laser output becomes weak alternately appear repeatedly. When the laser output at this time is detected by the photodiode 2, as shown in FIG. A stepped waveform with a constant period can be obtained. Such a waveform is generally called an interference fringe. Each stepped waveform, that is, each interference fringe is MHP. As described above, when the oscillation wavelength of the semiconductor laser 1 is changed for a certain period of time, the number of MHPs changes in proportion to the measurement distance.

  Next, the calculation unit 8 calculates the distance to the object 11 and the speed of the object 11 based on the minimum oscillation wavelength λa and the maximum oscillation wavelength λb of the semiconductor laser 1 and the number of MHPs counted by the signal extraction unit 7. FIG. 6 is a block diagram showing an example of the configuration of the calculation unit 8, and FIG. 7 is a flowchart showing the operation of the calculation unit 8. The calculation unit 8 calculates a distance / speed calculation unit that calculates a candidate value for the distance to the object 11 and a candidate value for the speed of the object 11 based on the minimum oscillation wavelength λa, the maximum oscillation wavelength λb, and the number of MHPs of the semiconductor laser 1. 80, a history displacement calculation unit 81 that calculates a history displacement that is a difference between the distance candidate value calculated by the distance / speed calculation unit 80 and the distance candidate value calculated immediately before, and a distance / speed calculation unit 80 A storage unit 82 that stores the calculation results of the history displacement calculation unit 81, a state determination unit 83 that determines the state of the object 11 based on the calculation results of the distance / speed calculation unit 80 and the history displacement calculation unit 81, and a state determination And a distance / speed determination unit 84 for determining the distance to the object 11 and the speed of the object 11 based on the determination result of the unit 83.

  In the present embodiment, it is assumed that the state of the object 11 is either a minute displacement state that satisfies a predetermined condition or a displacement state in which the movement is larger than the minute displacement state. When the average displacement of the object 11 per half cycle of the oscillation waveform of the semiconductor laser 1 is V, the minute displacement state is a state satisfying (λb−λa) / λb> V / Lb (where Lb is the time t The displacement state is a state satisfying (λb−λa) / λb ≦ V / Lb.

First, the distance / speed calculation unit 80 of the calculation unit 8 calculates the distance candidate values Lα (t) and Lβ (t) and the speed candidate values Vα (t) and Vβ (t) at the current time t as follows: And stored in the storage unit 82 (step S10 in FIG. 7).
Lα (t) = λa × λb × (MHP (t−1) + MHP (t))
/ {4 × (λb−λa)} (2)
Lβ (t) = λa × λb × (| MHP (t−1) −MHP (t) |)
/ {4 × (λb−λa)} (3)
Vα (t) = (MHP (t−1) −MHP (t)) × λb / 4 (4)
Vβ (t) = (MHP (t−1) + MHP (t)) × λb / 4 (5)

  In Expressions (2) to (5), MHP (t) is the number of MHPs calculated at the current time t, and MHP (t−1) is the number of MHPs calculated one time before MHP (t). is there. For example, if MHP (t) is the counting result of the first counting period Q1, MHP (t-1) is the counting result of the second counting period Q2, and conversely, MHP (t) is the second counting period. MHP (t−1) is the counting result of the first counting period Q1.

  The candidate values Lα (t) and Vα (t) are values calculated on the assumption that the object 11 is in a minute displacement state, and the candidate values Lβ (t) and Vβ (t) are obtained when the object 11 is in a displacement state. This is a calculated value. The calculation unit 8 performs calculations of Expressions (2) to (5) at each time (every counting period) when the number of MHPs is measured by the signal extraction unit 7.

Subsequently, the history displacement calculation unit 81 of the calculation unit 8 for each of the minute displacement state and the displacement state, the distance candidate value at the current time t and the distance candidate value at the previous time stored in the storage unit 82. The history displacement, which is the difference between the two, is calculated by the following equation and stored in the storage unit 82 (step S11 in FIG. 7). In the equations (6) and (7), the distance candidate values calculated one time before the current time t are Lα (t−1) and Lβ (t−1).
Vcalα (t) = Lα (t) −Lα (t−1) (6)
Vcalβ (t) = Lβ (t) −Lβ (t−1) (7)

The history displacement Vcalα (t) is a value calculated on the assumption that the object 11 is in a minute displacement state, and the history displacement Vcalβ (t) is a value calculated on the assumption that the object 11 is in a displacement state. The calculation unit 8 performs the calculations of Expressions (6) to (7) at each time when the number of MHPs is measured by the signal extraction unit 7. In the equations (4) to (7), the direction in which the object 11 approaches the physical quantity sensor of the present embodiment is defined as a positive velocity, and the direction in which the object 11 moves away is defined as a negative velocity.
Next, the state determination unit 83 of the calculation unit 8 determines the state of the object 11 using the calculation results of the expressions (2) to (7) stored in the storage unit 82 (step S12 in FIG. 7).

  As described in Japanese Patent Application Laid-Open No. 2006-31080, when the object 11 moves in a minute displacement state (constant velocity motion), the history displacement Vcalα (t calculated by assuming that the object 11 is in a minute displacement state ) Is constant, and the velocity candidate value Vα (t) calculated on the assumption that the object 11 is in a minute displacement state is equal to the average absolute value of the history displacement Vcalα (t). In addition, when the object 11 is moving at a constant speed in a minute displacement state, the sign of the history displacement Vcalβ (t) calculated on the assumption that the object 11 is in the displacement state is inverted every time the number of MHPs is measured. .

  Therefore, the state determination unit 83 calculates the speed calculated assuming that the sign of the history displacement Vcalα (t) calculated on the assumption that the object 11 is in the minute displacement state is constant and that the object 11 is in the minute displacement state. Is equal to the average value of the absolute values of the history displacement Vcalα (t), it is determined that the object 11 is moving at a constant speed in a minute displacement state.

  As described in Japanese Patent Application Laid-Open No. 2006-31080, when the object 11 moves in a displaced state (constant velocity motion), the history displacement Vcalβ (t) calculated assuming that the object 11 is in the displaced state The sign is constant, and the velocity candidate value Vβ (t) calculated on the assumption that the object 11 is in the displacement state is equal to the average value of the absolute values of the history displacement Vcalβ (t). In addition, when the object 11 is moving at a constant speed in a displaced state, the sign of the history displacement Vcalα (t) calculated on the assumption that the object 11 is in a minutely displaced state is inverted every time the number of MHPs is measured.

  Therefore, the state determination unit 83 has a constant sign of the history displacement Vcalβ (t) calculated on the assumption that the object 11 is in the displacement state, and a speed candidate calculated on the assumption that the object 11 is in the displacement state. When the value Vβ (t) and the average value of the absolute values of the history displacement Vcalβ (t) are equal, it is determined that the object 11 is moving at a constant speed in the displaced state.

  As described in Japanese Patent Application Laid-Open No. 2006-31080, when the object 11 is in a minute displacement state and is moving other than a constant velocity motion, the velocity candidates calculated assuming that the object 11 is in a minute displacement state The value Vα (t) and the average value of the absolute values of the history displacement Vcalα (t) calculated on the assumption that the object 11 is in a minute displacement state do not match. Similarly, the average value of the absolute values of the velocity candidate value Vβ (t) calculated assuming that the object 11 is in the displacement state and the history displacement Vcalβ (t) calculated assuming that the object 11 is in the displacement state do not match.

  Further, when the object 11 is in a minute displacement state and is moving other than a constant velocity motion, the sign of the history displacement Vcalα (t) calculated on the assumption that the object 11 is in a minute displacement state is the number of MHPs. The history displacement Vcalβ (t) calculated by assuming that the object 11 is in a displaced state is inverted at each time, but the change is not at every time when the number of MHPs is measured.

  Therefore, the state determination unit 83 reverses the sign of the history displacement Vcalα (t) calculated on the assumption that the object 11 is in a minute displacement state every time the number of MHPs is measured, and the object 11 is minutely displaced. When the velocity candidate value Vα (t) calculated on the assumption that the state is in the state does not coincide with the average value of the absolute values of the history displacement Vcalα (t), the object 11 performs a motion other than the uniform velocity motion in a minute displacement state. It is determined that

  Focusing on the velocity candidate value Vβ (t), the absolute value of Vβ (t) is a constant, and this value is equal to the wavelength change rate (λb−λa) / λb of the semiconductor laser 1. Therefore, the state determination unit 83 assumes that the absolute value of the velocity candidate value Vβ (t) calculated on the assumption that the object 11 is in the displacement state is equal to the wavelength change rate, and that the object 11 is in the minute displacement state. If the velocity candidate value Vα (t) calculated in this way and the average value of the absolute values of the history displacement Vcalα (t) do not match, it is determined that the object 11 is moving in a minute displacement state other than the constant velocity motion. May be.

  As described in Japanese Patent Application Laid-Open No. 2006-31080, when the object 11 is in a displacement state and is moving other than a constant velocity motion, a velocity candidate value calculated assuming that the object 11 is in a minute displacement state Vα (t) and the average value of the absolute value of the history displacement Vcalα (t) calculated on the assumption that the object 11 is in the minute displacement state do not coincide with each other, and the velocity candidate value calculated on the assumption that the object 11 is in the displacement state The average value of the absolute values of the history displacement Vcalβ (t) calculated on the assumption that Vβ (t) and the object 11 are in the displaced state do not match.

  In addition, when the object 11 is in a displacement state and is moving other than a constant velocity movement, the sign of the history displacement Vcalβ (t) calculated on the assumption that the object 11 is in a displacement state is the time at which the number of MHPs is measured. In the history displacement Vcalα (t) calculated on the assumption that the object 11 is in a minute displacement state, the change is not at every time when the number of MHPs is measured.

  Therefore, the state determination unit 83 reverses the sign of the history displacement Vcalβ (t) calculated on the assumption that the object 11 is in the displaced state at each time when the number of MHPs is measured, and the object 11 is in the displaced state. If the velocity candidate value Vβ (t) calculated on the assumption that there is no coincidence with the average value of the absolute values of the history displacement Vcalβ (t), the object 11 moves in a displaced state other than the uniform velocity motion. Is determined.

  When attention is paid to the velocity candidate value Vα (t), the absolute value of Vα (t) is a constant, and this value is equal to the wavelength change rate (λb−λa) / λb of the semiconductor laser 1. Therefore, the state determination unit 83 assumes that the absolute value of the velocity candidate value Vα (t) calculated on the assumption that the object 11 is in the minute displacement state is equal to the wavelength change rate, and that the object 11 is in the displacement state. If the calculated velocity candidate value Vβ (t) and the average value of the absolute values of the history displacement Vcalβ (t) do not match, it is determined that the object 11 is moving in a displacement state other than the uniform velocity motion. May be.

The distance / speed determination unit 84 of the calculation unit 8 determines the speed of the object 11 and the distance to the object 11 based on the determination result of the state determination unit 83 (step S13 in FIG. 7).
That is, when it is determined that the object 11 is moving at a constant speed in a minute displacement state, the distance / speed determining unit 84 sets the speed candidate value Vα (t) as the speed of the object 11 and uses the distance candidate value Lα ( t) is a distance from the object 11, and it is determined that the object 11 is moving at a constant speed in a displaced state, the speed candidate value Vβ (t) is the speed of the object 11, and the distance candidate value Lβ (t ) Is the distance to the object 11.

  Further, when it is determined that the object 11 is moving in a minute displacement state other than the constant velocity motion, the distance / speed determination unit 84 sets the speed candidate value Vα (t) as the speed of the object 11 and sets the distance The candidate value Lα (t) is set as the distance from the object 11. However, the actual distance is an average value of the distance candidate values Lα (t). Further, when it is determined that the object 11 is moving in a displacement state other than the uniform velocity motion, the distance / velocity determination unit 84 sets the velocity candidate value Vβ (t) as the velocity of the object 11 and sets the distance candidate. The value Lβ (t) is the distance from the object 11. However, the actual distance is an average value of the distance candidate values Lβ (t).

  Note that Vβ (t) is always a positive value and Vα (t) is either a positive or negative value due to the magnitude relationship between MHP (t−1) and MHP (t). It is not a representation of 11 speed directions. When the number of MHPs of the semiconductor laser whose oscillation wavelength is increasing is larger than the number of MHPs of the semiconductor laser whose oscillation wavelength is decreasing, the speed of the object 11 is positive (direction approaching the laser). )

The calculation unit 8 performs the processes of steps S <b> 10 to S <b> 13 every time (every counting period) when the number of MHPs is measured by the signal extraction unit 7.
The display device 9 displays a physical quantity calculated by the calculation unit 8 such as a distance from the object 11.

  As described above, in the present embodiment, the optical output and the oscillation wavelength can be controlled independently by using the MEMS wavelength tunable semiconductor laser as the semiconductor laser 1. As a result, in the present embodiment, the driving current is made constant while modulating the oscillation wavelength of the semiconductor laser 1 as shown in FIG. 3B, and a constant high light output is obtained as shown in FIG. Since the distance can be maintained, the measurement range can be extended.

  In the self-coupled rangefinder, the distance resolution is proportional to the oscillation wavelength change amount. Therefore, in the case of a sensor using a conventional drive current modulation type VCSEL, in order to improve the distance resolution, it is necessary to increase the change amount of the drive current supplied to the VCSEL, and the increase or decrease of the laser output is accordingly increased. As a result, when the drive current becomes small, there is a problem that the return light from the object is less than the light intensity sufficient to obtain the self-coupling effect.

  On the other hand, in this Embodiment, the change of the optical output in the period which extracts MHP can be made small. Since the self-coupling effect occurs with a small amount of return light, MHP can be obtained without depending on the reflectance and distance of the object 11 as compared with a sensor of a type that detects return light with a light receiving element. However, since the MHP itself is small with respect to the light output, the effect of sensing while maintaining a high light output with respect to the low-reflectance object 11 existing at a long distance is great. In this embodiment, since the oscillation wavelength change amount does not depend on the drive current amplitude, the oscillation wavelength change amount can be increased, and the distance resolution is improved as compared with a sensor using a conventional drive current modulation type VCSEL. Can be made.

  In the present embodiment, since the optical output of the semiconductor laser 1 is constant, that is, the output voltage of the current-voltage conversion amplifier 5 is substantially constant, the microscopic value superimposed on the output voltage of the current-voltage conversion amplifier 5 is small. MHP can be easily extracted. Therefore, it is not essential to provide a filter inside the signal extraction unit 7. If a filter is necessary to remove noise, a simple bandpass filter may be provided.

  In the present embodiment, since the change in the optical output of the semiconductor laser 1 is small, instability of the intensity of the MHP due to the change in the optical output can be avoided, and the measurement accuracy can be stabilized.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 8 is a cross-sectional view of the main part of the semiconductor laser 1 according to the second embodiment of the present invention. The same components as those in FIG. This embodiment shows an example in which the photodiode 2 is provided outside the semiconductor laser 1.

A through-hole 1024 that penetrates the silicon substrate 1017 a and the electrode 1023 is formed at the center of the silicon substrate 1017 a and the electrode 1023. Laser light emitted from the optical thin film 1019 enters the photodiode 2 through the electrostatic drive gap 1021 and the through hole 1024.
Other configurations of the physical quantity sensor are the same as those in the first embodiment.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. Also in the present embodiment, the configuration of the physical quantity sensor is the same as that of the first embodiment and the second embodiment, and will be described using the reference numerals in FIG.

  Laser outputs are classified from the viewpoint of safety. In general, a technique for reducing the average light output by pulsed light emission is known as a technique for increasing the safety of a laser. However, even if a pulsed drive current is supplied to a conventional drive current modulation type VCSEL to cause the VCSEL to emit light in a pulsed manner, the change in the oscillation wavelength is caused by the thermal expansion / contraction caused by the change in the drive current. There is a delay in shrinkage, and it is difficult to perform desired oscillation wavelength modulation.

  FIG. 9A is a diagram showing a drive current supplied to a conventional drive current modulation type VCSEL, and FIG. 9B is a diagram showing a time change of the oscillation wavelength of the VCSEL according to the drive current. In the example of FIG. 9A, a pulsed light is emitted from the VCSEL, and in order to modulate the oscillation wavelength of the VCSEL during the light emission period, a driving current having a triangular wave at the top is supplied to the VCSEL. With respect to this drive current, the expected change in the oscillation wavelength of the VCSEL has a waveform as shown by a broken line 90 in FIG. However, in practice, the waveform is as shown by 91 in FIG. 9B due to the delay in the expansion and contraction of the laser. According to FIG. 10 in which FIG. 9B is enlarged, it can be seen that the actual oscillation wavelength change 91 is deviated from the expected oscillation wavelength change 90 of the VCSEL. As shown in FIG. 10, when the rate of change in the oscillation wavelength of the VCSEL is not constant, the MHP cycle varies, resulting in errors in distance and speed measurement.

  In contrast, in the present embodiment, by using a MEMS wavelength tunable semiconductor laser as the semiconductor laser 1, the optical output and the oscillation wavelength can be controlled independently as described in the first embodiment. . Wavelength modulation in a MEMS wavelength tunable semiconductor laser using electrostatic drive does not have a large nonlinearity like wavelength change using thermal expansion / contraction due to drive current, and therefore oscillation when the semiconductor laser 1 emits pulses. The nonlinearity of the wavelength change can be improved.

  The control of the oscillation wavelength of this embodiment will be described with reference to FIGS. 11A is a diagram showing a diaphragm control signal supplied from the diaphragm driver 10 to the semiconductor laser 1, and FIG. 11B is a diagram showing a time change of the oscillation wavelength of the semiconductor laser 1 according to the diaphragm control signal. 11 (C) is a diagram showing a drive current supplied from the laser driver 4 to the semiconductor laser 1, and FIG. 11 (D) is a diagram showing an optical output of the semiconductor laser 1 according to the drive current. In FIG. 11C, the diaphragm control signal is indicated by a broken line 110 in order to facilitate comparison with the diaphragm control signal. In FIG. 11D, the oscillation wavelength is indicated by a broken line 111 in order to facilitate comparison with the oscillation wavelength change of the semiconductor laser 1. P1 is the first oscillation period, P2 is the second oscillation period, λa is the minimum value of the oscillation wavelength, λb is the maximum value of the oscillation wavelength, and TL is the period of pulse emission.

  Other configurations of the physical quantity sensor are the same as those in the first and second embodiments. However, in the first and second embodiments, since the first oscillation period P1 and the second oscillation period P2 appear alternately without interruption, the distance to the object 11 and the speed of the object 11 are continuously measured. However, in the present embodiment, since the first oscillation period P1 and the second oscillation period P2 appear intermittently, it goes without saying that the distance and speed are also measured intermittently.

  As described above, in the present embodiment, the pulsed drive current is intermittently supplied to the semiconductor laser 1 as shown in FIG. Since pulse light can be emitted and the average light output can be reduced, safety for humans can be ensured.

  Further, in this embodiment, by supplying a diaphragm control signal whose voltage changes in a triangular wave shape to the semiconductor laser 1 as shown in FIG. 11A within at least the period of pulse emission, FIG. As shown, a first oscillation period P1 in which the oscillation wavelength continuously increases at a constant change rate and a second oscillation period P2 in which the oscillation wavelength continuously decreases at a constant change rate are within the pulse emission period. The oscillation wavelength can be modulated to appear. At this time, the oscillation wavelength of the semiconductor laser 1 changes according to the diaphragm control signal without being affected by the change of the drive current, so that the nonlinearity of the oscillation wavelength change when the semiconductor laser 1 emits pulses is improved. be able to. As a result, in the present embodiment, the number of MHPs does not change regardless of the distance to the object 11, so the distance compared to the case where pulsed emission is performed using a conventional drive current modulation type VCSEL. And speed measurement error can be improved.

  In the present embodiment, it is assumed that the drive current and the oscillation wavelength of the semiconductor laser 1 are independent, but strictly speaking, the distance between the optical thin film 1019 and the active layer 1014 on the diaphragm 1022 slightly changes. Therefore, the drive current and the oscillation wavelength are not completely independent. However, since the diaphragm control signal for controlling the oscillation wavelength is independent of the drive current, the influence of the change in the drive current can be easily corrected by the diaphragm control signal. More specifically, the waveform of the diaphragm control signal may be set in advance so that the oscillation wavelength of the semiconductor laser 1 increases at a constant change rate or decreases at a constant change rate.

  In order to generate such a diaphragm control signal, for example, a digital value of the diaphragm control signal is set in advance in a memory (not shown) in the diaphragm driver 10, and this digital value is converted by a D / A converter (not shown). It may be converted into an analog signal and output from the diaphragm driver 10.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. FIG. 12 is a block diagram showing a configuration of a physical quantity sensor according to the fourth embodiment of the present invention. The physical quantity sensor of FIG. 12 uses the beam splitter 12, the photodiode 13 as a return light detection light receiver, and the output current of the photodiode 13 as a voltage compared to the physical quantity sensors of the first and second embodiments. A current-voltage conversion amplifier 14 that converts and amplifies, and an object detection unit 15 that determines whether an object is present in the laser light emission direction based on the output voltage of the current-voltage conversion amplifier 14 is added. is there.

  Diaphragm control signal supplied from the diaphragm driver 10 to the semiconductor laser 1, the oscillation wavelength of the semiconductor laser 1 according to the diaphragm control signal, the drive current supplied from the laser driver 4 to the semiconductor laser 1, and the semiconductor laser according to the drive current The light output of No. 1 is as shown in FIGS. 11 (A) to 11 (D).

Laser light emitted from the semiconductor laser 1 passes through the beam splitter 12, is condensed by the lens 3, and enters the object 11. The return light from the object 11 is collected by the lens 3, a part of the return light is reflected by the beam splitter 12 and enters the photodiode 13, and the rest of the return light passes through the beam splitter 12 and passes through the semiconductor laser 1. Is incident on.
The current-voltage conversion amplifier 14 converts the output current of the photodiode 13 into a voltage and amplifies it.

  The object detection unit 15 determines whether the object 11 exists in the radiation direction of the semiconductor laser 1 based on the output voltage of the current-voltage conversion amplifier 14. When the object 11 does not exist in the radiation direction of the semiconductor laser 1, the amount of light incident on the photodiode 13 is lost or reduced. The object detection unit 15 determines that the object 11 does not exist in the radiation direction of the semiconductor laser 1 when the output voltage of the current-voltage conversion amplifier 14 is, for example, a predetermined threshold value or less.

Further, when the output voltage of the current-voltage conversion amplifier 14 exceeds a predetermined threshold value, the object detection unit 15 determines that the object 11 exists in the radiation direction of the semiconductor laser 1 and indicates that the object 11 has been detected. Outputs an object detection signal. In response to the output of the object detection signal, the display device 9 displays that the object 11 has been detected.
Other configurations of the physical quantity sensor are the same as those in the first and second embodiments.

  Note that the object detection unit 15 determines that the object 11 is present in the radiation direction of the semiconductor laser 1 when the output voltage of the current-voltage conversion amplifier 14 exceeds the threshold value for each pulse emission period TL of the semiconductor laser 1. You may do it. As described above, whether or not the output voltage of the current-voltage conversion amplifier 14 exceeds the threshold value for each period TL of the pulse light emission over a plurality of periods eliminates the influence of disturbance light incident on the photodiode 13. This is because the presence or absence of the object 11 is correctly determined.

  Thus, in this embodiment mode, by monitoring the pulsed return light, the same function as the reflective photoelectric switch can be added, and an object detection function can be realized. Further, similarly to a general pulse light emission type photoelectric switch, it is possible to realize a disturbance light removal function and a mutual interference prevention function of a plurality of sensors.

  Since the self-coupled laser sensor uses the principle of external interference between irradiation light and return light, the MHP and noise cannot be separated when the object is moving randomly, and the physical quantity of the object is reduced. Measurement may not be possible. From the viewpoint of safety, when an object detection function is to be added, even in a sensor using a conventional drive current modulation type VCSEL, a pulsed laser beam is emitted from a general photoelectric sensor by causing the VCSEL to emit light in pulses. It can be used as a light source for a switch.

  However, as described in the third embodiment, it is difficult to perform a desired oscillation wavelength modulation even if a conventional drive current modulation type VCSEL is caused to emit pulses. Therefore, in a sensor using a conventional drive current modulation type VCSEL, if an object detection function is to be added, it is necessary to separate a laser drive method for object detection and a laser drive method at the time of measurement after object detection.

  On the other hand, in this embodiment, the pulse modulation of the optical output for the function as the photoelectric switch and the modulation of the oscillation wavelength for the function as the physical quantity sensor can be performed simultaneously, and the configuration is simple. An object detection function can be added.

In the third and fourth embodiments, the diaphragm control signal whose voltage changes in a triangular wave shape during the pulse emission period is used. However, if the drive current and the triangular wave are synchronized, the diaphragm control signal is continuous. A triangular wave diaphragm control signal may be used. FIG. 13A shows the diaphragm control signal in this case, and FIG. 13B shows the time variation of the oscillation wavelength of the semiconductor laser 1 in accordance with the diaphragm control signal. Note that in FIG. 13A, the drive current is indicated by a broken line 130 for easy comparison with the drive current. In FIG. 13B, the light output is indicated by a broken line 131 for easy comparison with the light output of the semiconductor laser 1.
In the fourth embodiment, the beam splitter 12 is used. However, the beam splitter 12 is not an essential component as long as the return light from the object 11 can be detected.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. FIG. 14 is a block diagram showing a configuration of a physical quantity sensor according to the fifth embodiment of the invention. The physical quantity sensor of FIG. 14 is obtained by adding a light output control unit 16 to the physical quantity sensor of the first and second embodiments.

The light output controller 16 controls the drive current supplied from the laser driver 4 to the semiconductor laser 1 so that the output current of the photodiode 2 becomes constant. More specifically, the light output control unit 16 controls the drive current so that the output voltage of the current-voltage conversion amplifier 5 becomes a predetermined reference value. Other configurations of the physical quantity sensor are the same as those in the first and second embodiments.
Thus, in the present embodiment, the optical output of the semiconductor laser 1 can be made constant, and the life of the semiconductor laser 1 can be extended.

  The drive current-optical output characteristics of a laser device have temperature dependence. FIG. 15 is a diagram showing an example of the drive current-light output characteristics of the semiconductor laser 1. C0, C10, C20, C30, C40, and C50 have characteristics of 0 ° C., 10 ° C., 20 ° C., 30 ° C., 40 ° C., and 50 ° C., respectively. When the object to be measured is a low-reflectance object at a long distance, maintaining a high light output is effective, but a high ambient temperature and a high drive current cause a shortened lifetime of the laser device.

  In the case of a sensor using a conventional drive current modulation type VCSEL, feedback can be applied by changing the oscillation wavelength by the drive current, but it is necessary to give the drive current an amplitude in order to change the oscillation wavelength. This makes it difficult to achieve both a change in wavelength and a lifetime. On the other hand, in the present embodiment, since the light output and the oscillation wavelength can be controlled independently, the light output control considering the life of the semiconductor laser 1 can be performed. That is, in the present embodiment, an appropriate drive current is selected by detecting the output voltage of the current-voltage conversion amplifier 5 corresponding to the light output amount and feeding back a signal based on the detection result to the laser driver 4. Thus, the life of the semiconductor laser 1 can be extended.

  From the viewpoint of the life of the semiconductor laser 1, it is necessary to limit the temperature of the semiconductor laser 1, and it is necessary to determine the maximum drive current when the ambient temperature is high. Since the light output of the semiconductor laser 1 decreases as the ambient temperature increases, the light output amount (for example, 1 mW in the example of FIG. 15) at the maximum drive current at the maximum ambient temperature where the physical quantity sensor is assumed to be used is the reference light. As the output amount, the output voltage of the current-voltage conversion amplifier 5 when the reference light output amount is output from the semiconductor laser 1 may be set in advance in the light output control unit 16 as a reference value.

  As described in the first embodiment, MHP is superimposed on the output voltage of the current-voltage conversion amplifier 5, but the magnitude of MHP is much higher than the output voltage of the current-voltage conversion amplifier 5. Therefore, the MHP does not affect the control of the light output.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described. FIG. 16 is a block diagram showing a configuration of a physical quantity sensor according to the sixth embodiment of the present invention. The physical quantity sensor of FIG. 16 is obtained by adding a light output control unit 17 to the physical quantity sensor of the first and second embodiments.

  The light output controller 17 controls the drive current supplied from the laser driver 4 to the semiconductor laser 1 so that the light output of the semiconductor laser 1 becomes an appropriate value according to the ambient temperature. Other configurations of the physical quantity sensor are the same as those in the first and second embodiments.

  In the method of the fifth embodiment in which the light output amount of the semiconductor laser 1 matches the reference light output amount when the ambient temperature is high, the temperature of the semiconductor laser 1 has a margin when the ambient temperature is low. Depending on the case, it may be desired to increase the light output. In this case, a method of changing the light output depending on the ambient temperature is more suitable than outputting an excessive light output at a low temperature with a constant driving current.

  The light output control unit 17 changes the drive current in accordance with the ambient temperature, and specifically includes a resistor whose temperature characteristics are defined in advance. The temperature characteristic is defined so that the product of the drive current and the light output is always constant even when the ambient temperature changes, for example, as indicated by a circle 150 in FIG.

In this way, in this embodiment, the optical output of the semiconductor laser 1 can be changed according to the ambient temperature, and the ambient temperature is low and the temperature of the semiconductor laser 1 is marginal while realizing a longer life of the semiconductor laser 1. If there is, it is possible to increase the optical output and realize a long measurement range.
As shown in FIG. 14, the output voltage of the current-voltage conversion amplifier 5 is fed back to the optical output control unit 17, and the optical output control unit 17 outputs the optical output and the drive current represented by the output voltage of the current-voltage conversion amplifier 5. The drive current may be controlled so that the product of

[Seventh Embodiment]
Next, a seventh embodiment of the present invention will be described. FIG. 17 is a block diagram showing a configuration of a physical quantity sensor according to the seventh embodiment of the present invention. The physical quantity sensor of FIG. 17 is different from the physical quantity sensors of the first and second embodiments in that the beam splitter 12, the photodiode 13 that is a return light detection light receiver, the current-voltage conversion amplifier 14, the light An output control unit 18 is added.

As described in the fourth embodiment, the laser light emitted from the semiconductor laser 1 passes through the beam splitter 12, is condensed by the lens 3, and enters the object 11. The return light from the object 11 is collected by the lens 3, a part of the return light is reflected by the beam splitter 12 and enters the photodiode 13, and the rest of the return light passes through the beam splitter 12 and passes through the semiconductor laser 1. Is incident on.
The current-voltage conversion amplifier 14 converts the output current of the photodiode 13 into a voltage and amplifies it.

  The optical output controller 18 controls the drive current supplied from the laser driver 4 to the semiconductor laser 1 so that the output current of the photodiode 13 is constant. More specifically, the light output control unit 18 controls the drive current so that the output voltage of the current-voltage conversion amplifier 14 becomes a predetermined reference value. Other configurations of the physical quantity sensor are the same as those in the first and second embodiments. Thus, in this embodiment, the amount of light returned from the object 11 can be made constant.

  In order to stably extract MHP from the light output of the semiconductor laser 1 without depending on the distance to the object 11 and the reflectance of the object 11, the amount of return light is appropriately controlled so as to obtain a self-coupling effect. Is preferred. As a specific target, a laser oscillation state in which MHP is maximized or a laser oscillation state in which MHP is stably generated may be maintained. Therefore, the current-voltage conversion amplifier when the photodiode 13 receives the reference return light amount, with the return light amount that can obtain a laser oscillation state in which MHP is maximized or a laser oscillation state in which MHP is stably generated as a reference return light amount. The output voltage of 14 may be set in advance in the light output control unit 18 as a reference value.

Thus, in the present embodiment, MHP can be stably extracted, so that the measurement accuracy of the physical quantity of the object 11 and the measurement reliability can be improved. In the present embodiment, since the light output is controlled so that the return light amount from the object 11 is constant, the light output is reduced when a return light amount sufficient for MHP extraction is obtained. Become. Therefore, according to the present embodiment, the lifetime of the semiconductor laser 1 can be increased.
Further, although the beam splitter 12 is used in the present embodiment, the beam splitter 12 is not an essential configuration as long as the return light from the object 11 can be detected.

[Eighth Embodiment]
Next, an eighth embodiment of the present invention will be described. The present embodiment shows another configuration example of the signal extraction unit. FIG. 18 is a block diagram showing an example of the configuration of the signal extraction unit 7a of the present embodiment. The signal extraction unit 7 a includes a determination unit 71, an AND operation unit (AND) 72, a counter 73, a counting result correction unit 74, and a storage unit 75.
FIG. 19 is a block diagram showing an example of the configuration of the counting result correction unit 74. The counting result correction unit 74 includes a period measurement unit 740, a frequency distribution creation unit 741, a representative value calculation unit 742, and a correction value calculation unit 743.

  20A to 20F are diagrams for explaining the operation of the signal extraction unit 7a. FIG. 20A shows the waveform of the output voltage of the current-voltage conversion amplifier 5, that is, the waveform of MHP. FIG. 20B is a diagram schematically illustrating the output of the determination unit 71 corresponding to FIG. 20A, and FIG. 20C is a diagram illustrating the gate signal GS input to the signal extraction unit 7a. 20D is a diagram showing the counting result of the counter 73 corresponding to FIG. 20B, FIG. 20E is a diagram showing the clock signal CLK input to the signal extraction unit 7a, and FIG. It is a figure which shows the measurement result of the period measurement part 740 corresponding to FIG. 20 (B).

  First, the determination unit 71 of the signal extraction unit 7a determines whether the output voltage of the current-voltage conversion amplifier 5 shown in FIG. 20A is high level (H) or low level (L), and FIG. ) Is output. At this time, the determination unit 71 determines that the output voltage of the current-voltage conversion amplifier 5 is high when the output voltage of the current-voltage conversion amplifier 5 rises to the threshold value TH1 or more, and the output voltage of the current-voltage conversion amplifier 5 decreases. The output of the current-voltage conversion amplifier 5 is binarized by determining a low level when the threshold value TH2 (TH2 <TH1) or less.

  The AND 72 outputs a logical product operation result of the output of the determination unit 71 and the gate signal GS as shown in FIG. 20C, and the counter 73 counts the rise of the output of the AND 72 (FIG. 20D). . Here, the gate signal GS is a signal that rises at the beginning of the counting period (in the present embodiment, the first oscillation period or the second oscillation period) and falls at the end of the counting period. Therefore, the counter 73 counts the number of rising edges of the output of the AND 72 during the counting period (that is, the number of rising edges of MHP).

On the other hand, the period measuring unit 740 of the counting result correcting unit 74 measures the period of the rising edge of the output of the AND 72 during the counting period (that is, the MHP period) every time a rising edge occurs. At this time, the period measurement unit 740 measures the MHP period with the period of the clock signal CLK shown in FIG. In the example of FIG. 20F, the period measurement unit 740 sequentially measures Tα, Tβ, and Tγ as MHP periods. As is clear from FIGS. 20E and 20F, the magnitudes of the periods Tα, Tβ, and Tγ are 5 clocks, 4 clocks, and 2 clocks, respectively. The frequency of the clock signal CLK is assumed to be sufficiently higher than the highest frequency that the MHP can take.
The storage unit 75 stores the count result of the counter 73 and the measurement result of the period measurement unit 740.

After the gate signal GS falls and the counting period ends, the frequency distribution creation unit 741 of the counting result correction unit 74 creates a frequency distribution of the MHP period during the counting period from the measurement result stored in the storage unit 75. .
Subsequently, the representative value calculation unit 742 of the counting result correction unit 74 calculates the median value (median) T0 of the MHP cycle from the frequency distribution created by the frequency distribution creation unit 741.

From the frequency distribution created by the frequency distribution creation unit 741, the correction value calculation unit 743 of the count result correction unit 74 calculates the sum Ns of the frequencies of the class that is 0.5 times or less the median value T0 of the cycle and the median value of the cycle. A total sum Nw of class frequencies that is 1.5 times or more of T0 is obtained, and the count result of the counter 73 is corrected as shown in the following equation.
N ′ = N + Nw−Ns (8)
In Equation (8), N is the number of MHPs that are the counting result of the counter 73, and N ′ is the corrected counting result.

  FIG. 21 shows an example of the frequency distribution. In FIG. 21, Ts is a class value 0.5 times the median value T0 of the period, and Tw is a class value 1.5 times the median value T0. It goes without saying that the class in FIG. 21 is a representative value of the MHP cycle. In FIG. 21, the frequency distribution between the median values T0 and Ts and between the median values T0 and Tw is omitted in order to simplify the description.

FIG. 22 is a diagram for explaining the correction principle of the counting result of the counter 73. FIG. 22A is a diagram schematically showing the waveform of the output voltage of the current-voltage conversion amplifier 5, that is, the waveform of MHP. 22 (B) is a diagram showing the counting result of the counter 73 corresponding to FIG. 22 (A).
Originally, the MHP cycle varies depending on the distance to the measurement target 12, but if the distance to the measurement target 12 remains unchanged, the MHP appears in the same cycle. However, due to noise, the MHP waveform may be missing or a waveform that should not be counted as a signal may be generated, resulting in an error in the number of MHPs.

  When signal loss occurs, the MHP cycle Tw at the location where the loss occurs is approximately twice the original cycle. That is, when the MHP cycle is approximately twice or more the median value T0, it can be determined that the signal is missing. Accordingly, the total frequency Nw of the classes having the period Tw or more is regarded as the number of missing signals, and the missing signal can be corrected by adding this Nw to the counting result N of the counter 73.

  Further, the MHP cycle Ts at the location where noise is counted is approximately 0.5 times the original cycle. That is, when the MHP cycle is about 0.5 times or less of the median value, it can be determined that the signals are excessively counted. Accordingly, the sum Ns of the frequencies of the class having a period of Ts or less is regarded as the number of times that the signal is excessively counted, and the Ns is subtracted from the count result N of the counter 73, thereby correcting the erroneously counted noise. The above is the correction principle of the counting result shown in Expression (8).

  The correction value calculation unit 743 outputs the value of the corrected count result N ′ calculated by Expression (8) to the calculation unit 8. The signal extraction unit 7a performs the above processing for each of the first counting period Q1 and the second counting period Q2. In the present embodiment, the median value is used as the representative value of the MHP cycle, but the mode value may be used as the representative value of the cycle.

As described above, the signal extraction unit 7a described in the present embodiment can be used in place of the signal extraction unit 7 in the first to seventh embodiments.
According to the signal extraction unit 7a, the MHP cycle during the counting period is measured, a frequency distribution of the MHP cycle during the counting period is created from the measurement result, and the median of the MHP cycle is calculated from the frequency distribution. From the frequency distribution, a sum Ns of class frequencies that is 0.5 times or less of the median value and a sum Nw of class frequencies that are 1.5 times or more of the median value are obtained, and based on these frequencies Ns and Nw By correcting the counting result of the counter, the MHP counting error can be corrected, so that the physical quantity measurement accuracy can be improved.

[Ninth Embodiment]
Next, a ninth embodiment of the present invention will be described. FIG. 23 is a block diagram showing a configuration of a physical quantity sensor according to the ninth embodiment of the present invention. The physical quantity sensor of FIG. 23 includes a semiconductor laser 1, a photodiode 2, a lens 3, a laser driver 4a that supplies a driving current modulated by a modulation signal to the semiconductor laser 1, a current-voltage conversion amplifier 5, a signal Extraction unit 7, calculation unit 8, display device 9, diaphragm driver 10 a that supplies a diaphragm control signal synchronized with the reference signal to semiconductor laser 1, reference signal generation circuit 19 that generates the reference signal, and voltage-controlled oscillator A PLL (Phase Locked Loop) circuit 20 that is a phase control means for controlling the voltage, a voltage controlled oscillator (VCO) 21 that generates a modulation signal, and an MHP waveform included in the output voltage of the current-voltage conversion amplifier 5 And an averaging processing unit 22 for averaging.

The reference signal generation circuit 19 generates a sinusoidal reference signal. The frequency of this reference signal is set to a value lower than the lowest frequency assumed for MHP.
The diaphragm driver 10a supplies the semiconductor laser 1 with a triangular wave diaphragm control signal that repeatedly increases and decreases the voltage at a constant rate of change with respect to time, like the diaphragm driver 10 of the first embodiment. However, the diaphragm driver 10 a outputs the diaphragm control signal in synchronization with the reference signal output from the reference signal generation circuit 19.

  The VCO 21 generates a sinusoidal modulation signal. The laser driver 4 a modulates the amplitude of the drive current with the modulation signal output from the VCO 21 and supplies the modulated drive current to the semiconductor laser 1. At this time, the amplitude of the modulation signal superimposed on the drive current is set to a value smaller than the magnitude of the drive current.

  The PLL circuit 20 compares the phase of the reference signal output from the reference signal generation circuit 19 and the modulation signal included in the output voltage of the current-voltage conversion amplifier 5, and the frequency of the modulation signal is equal to the frequency of the reference signal. The VCO 21 is controlled so that the modulation signal is synchronized with the reference signal or the phase difference between the modulation signal and the reference signal is constant.

  In the measurement of physical quantities using a wavelength modulation type sensor, a value obtained by directly counting MHP is often used, but MHP may have a frequency that is three digits or more faster than a carrier wave (diaphragm control signal) for oscillation wavelength modulation. In order to improve the repeatability of the count value, the timing for starting the MHP counting and the length of the counting time are increased so that the timing is synchronized with the oscillation wavelength modulation carrier wave or the timing of a certain phase difference. It is necessary to control the accuracy.

  FIG. 24A is a diagram showing diaphragm control signals supplied from the diaphragm driver 10 to the semiconductor laser 1 in the first and second embodiments, and FIGS. 24B and 24C are current-voltage conversions. It is a figure which shows MHP extracted from the output of the amplifier 5. FIG. However, FIG. 24B shows the MHP at the same time as the diaphragm control signal of FIG. 24A, and FIG. 24C shows the MHP starting from the counting start time.

  When the oscillation wavelength of the semiconductor laser 1 is modulated by the diaphragm control signal as in the first and second embodiments, the timing of the diaphragm control signal is used as a reference as shown in FIGS. 24 (A) and 24 (B). The period during which MHP is counted can be controlled to some extent, and variations in the MHP count value can be reduced. However, as shown in FIG. 24C, the variation in the MHP counting start timing decreases the correlation between the time starting from the counting start time and the extracted MHP, and the average of the MHPs using the synchronization signal. Noise elimination and other methods cannot be performed. In other words, since the MHP timing is shifted every time counting is performed and the repetition accuracy is poor, a method of averaging MHP over a plurality of counting periods cannot be used.

  In contrast, in the present embodiment, by using the PLL circuit 20, the diaphragm control signal and the modulation signal included in the optical output of the semiconductor laser 1 are synchronized or modulated so as to have a constant phase difference. Since the phase of the signal can be controlled and the optical output can be modulated in synchronization with the diaphragm control signal, the timing of the MHP counting period can be controlled with high accuracy, and the counting start time is the starting point. Correlation (repetition accuracy) between time and MHP can be increased, and noise removal techniques such as averaging can be used. That is, when the state of the object 11 does not change, the MHP does not shift in position with respect to the diaphragm control signal and always appears at the same position. Therefore, the MHP is triggered by the diaphragm control signal and averaged. As a result, MHP noise can be removed.

The configuration and operation of the signal extraction unit 7 are the same as those in the first embodiment, but here, the signal extraction unit 7 outputs the MHP counting result to the averaging processing unit 22.
Further, instead of the signal extraction unit 7, the signal extraction unit 7a described in the eighth embodiment can be used. In this case, the correction value calculation unit 743 of the signal extraction unit 7a averages the corrected count result N ′ calculated by the equation (8) and the representative value (median value or mode value) of the MHP cycle. Output to.

  FIG. 25 is a block diagram showing an example of the configuration of the averaging processing unit 22. The averaging processing unit 22 includes an A / D converter (ADC) 220, a memory 221, an averaging calculation unit 222, a counting unit 223, and a state determination unit 224.

The ADC 220 converts the output of the current-voltage conversion amplifier 5 into a digital signal. The memory 221 stores the digital signal output from the ADC 220.
The averaging calculation unit 222 averages the digital signals stored in the memory 221 for a plurality of first counting periods Q1 and averages for a plurality of second counting periods Q2.

  The first counting period Q1 is the same period as the first oscillation period P1, or is included in the first oscillation period P1 and starts after a predetermined time from the start point of the first oscillation period P1. Similarly, the second counting period Q2 is the same period as the second oscillation period P2 or a period that is included in the second oscillation period P2 and starts after a predetermined time from the start time of the second oscillation period P2. is there. Since the diaphragm driver 10a notifies whether the current time is the first oscillation period P1 or the second oscillation period P2, the averaging calculator 222 determines whether the current time is the first counting period Q1 or the second counting period Q2. Can be recognized.

  26A to 26C are diagrams for explaining the operation of the averaging calculation unit 222. FIG. 26A illustrates the MHP in the latest first counting period Q1 stored in the memory 221. FIG. 26B shows the MHP in the first counting period Q1 i times before the latest (i is an integer), and FIG. 26C is averaged over a plurality of first counting periods Q1. MHP is shown. The averaging calculation unit 222 processes a digital signal. In FIGS. 26A to 26C, the MHP is simply shown as an analog signal.

The averaging calculation unit 222 obtains the latest sample value sampled by the ADC 220 at the timing of the elapsed time t from the start time of the counting period, At (n), and at the same elapsed time t in the counting period i times before the latest. Assuming that the sampled sample value is At (n−i), the average value Atav of the sample values in m times (for example, m = 10) is calculated as follows.
Atav = {At (n) + At (n−1) +... + A (n−m−1)} / m
... (9)

  The averaging calculation unit 222 performs the averaging as described above for each timing at which the elapsed time from the start time of each counting period is the same for a plurality of first counting periods Q1 and a plurality of second countings. In the counting periods Q2, the elapsed time from the start time of each counting period is performed at the same timing. Note that the interval at which the averaging calculation unit 222 performs the calculation (interval between times t and t + 1 in FIGS. 26A to 26C) is the sampling interval of the ADC 220. As described above, the averaging calculation unit 222 can average the MHP.

  The counting unit 223 counts the number of MHPs included in the output of the averaging calculation unit 222 for each of the first counting period Q1 and the second counting period Q2. The counting unit 223 may use a counter or may use an FFT.

  Next, the state determination unit 224 determines the state of the object 11 based on the count result output from the signal extraction units 7 and 7a and the representative value (median value or mode value) of the MHP cycle, and performs signal extraction. It is determined which of the counting results output from the units 7 and 7a and the counting results output from the counting unit 223 is to be output to the arithmetic unit 8.

  The state determination unit 224 compares the current count result output from the signal extraction unit 7 with the count result output from the signal extraction unit 7 before T (T is a triangular wave period) time, and the change is within a predetermined range. If it is within the range, it is determined that the state of the object 11 has not changed, and the current counting result output from the counting unit 223 is output to the calculation unit 8. Further, the state determination unit 224 compares the current counting result output from the signal extraction unit 7 with the counting result output from the signal extraction unit 7 before T time, and when the change exceeds a predetermined range, It is determined that the state of the object 11 has changed, and the current counting result output from the signal extraction unit 7 is output to the calculation unit 8. Note that comparing the current value with the value before T time means comparing the value of the first counting period Q1 with the value of the first counting period Q1 one time before and the value of the second counting period Q2. Is compared with the value of the second counting period Q2 one time before.

  When the signal extraction unit 7a is used instead of the signal extraction unit 7, the state determination unit 224 performs the following operation. That is, the state determination unit 224 uses the representative value of the current MHP cycle output from the correction value calculation unit 743 of the signal extraction unit 7a as the representative value of the MHP cycle output from the correction value calculation unit 743 T time ago. If the change is within a predetermined range, it is determined that the state of the object 11 has not changed, and the current count result output from the counting unit 223 is output to the calculation unit 8. In addition, the state determination unit 224 compares the representative value of the current MHP cycle output from the correction value calculation unit 743 with the representative value of the MHP cycle output from the correction value calculation unit 743 T time before, When the change exceeds a predetermined range, it is determined that the state of the object 11 has changed, and the current count result output from the correction value calculation unit 743 is output to the calculation unit 8.

Further, the state determination unit 224 compares the current count result output from the correction value calculation unit 743 with the count result output from the correction value calculation unit 743 before time T, and the change in the count result is within a predetermined range. If the change of the counting result exceeds a predetermined range, the current counting result output from the correction value calculating unit 743 is calculated. You may make it output to the part 8. FIG. In addition, when comparing the count results, in any case of comparing the representative values of the periods, the comparison may be made with an average value within a certain range.
The averaging processing unit 22 performs the above processing for each of the first counting period Q1 and the second counting period Q2.

  Based on the minimum oscillation wavelength λa and the maximum oscillation wavelength λb of the semiconductor laser 1 and the counting result output from the averaging processing unit 22, the arithmetic unit 8 determines whether or not the object 11 is connected to the object 11 as described in the first embodiment. The distance and the speed of the object 11 may be calculated. Other configurations of the physical quantity sensor are the same as those in the first and second embodiments.

  As described above, in this embodiment, by modulating the optical output of the semiconductor laser 1 in synchronization with the diaphragm control signal, it is possible to remove the variation in the timing of the MHP counting period with respect to the diaphragm control signal. The measurement accuracy of 11 physical quantities can be improved. In the present embodiment, noise can be removed by averaging MHP over a plurality of counting periods using a diaphragm control signal as a trigger, and noise and MHP separation performance can be improved. Measurement accuracy can be further improved. The averaging processing unit 22 is not an essential configuration. When the averaging processing unit 22 is not used, the count result of the signal extraction unit 7 or 7a may be directly input to the calculation unit 8 as in the other embodiments.

  Since the modulation of the optical output in the present embodiment is for triggering to synchronize the MHP, a very small modulation amount is sufficient. That is, the modulation amount of the drive current in the present embodiment is greatly different from the modulation amount of the drive current for ensuring the distance resolution in the conventional drive current modulation type sensor. Therefore, in the present embodiment, it can be said that the light output is substantially constant, so the configuration of the present embodiment does not impair the effects described in the first embodiment.

[Tenth embodiment]
Next, a tenth embodiment of the present invention will be described. FIG. 27 is a block diagram showing the configuration of the physical quantity sensor according to the tenth embodiment of the invention. The physical quantity sensor of FIG. 27 is obtained by adding a phase detection unit 23 to the physical quantity sensor of the ninth embodiment.

  As described in the ninth embodiment, when the timing of the MHP counting period with respect to the diaphragm control signal is controlled with high accuracy, when the laser beam is irradiated to the stationary reference surface, the diaphragm control signal MHP occurs at the same timing every time. When the correlation between the drive current and the diaphragm control signal is high, a change in oscillation wavelength caused by a change in ambient temperature or the like appears as a phase change in MHP. For example, when the rate of change of the oscillation wavelength of the semiconductor laser 1 increases due to a change in ambient temperature, the number of MHPs per unit distance increases, so the MHP cycle when the reference plane is irradiated with laser light is shortened.

Therefore, the measurement error due to the ambient temperature change can be reduced by feeding back the phase change of the MHP to the drive current.
That is, when the phase detection unit 23 checks the phase of the MHP included in the output of the current-voltage conversion amplifier 5 for a plurality of first counting periods Q1, if there is a phase change, the phase detection unit 23 performs a plurality of times. The amplitude of the diaphragm control signal supplied from the diaphragm driver 10a to the semiconductor laser 1 is controlled so that the phase of the MHP coincides for one counting period Q1, that is, the rate of change of the oscillation wavelength of the semiconductor laser 1 is constant. To do.

  Other configurations of the physical quantity sensor are the same as those in the ninth embodiment. As described in the ninth embodiment, the signal extraction unit 7 a may be used instead of the signal extraction unit 7. In the above description, only the first counting period Q1 has been described. However, the phase detection unit 23 controls the diaphragm control signal a plurality of first counting periods Q1 and a plurality of second counting periods Q2. For each of the above.

  Thus, in this embodiment, even if the ambient temperature changes, the oscillation wavelength change rate of the semiconductor laser 1 can be made constant, and the measurement error due to the ambient temperature change can be reduced. This embodiment is effective only when a stationary reference plane is observed. As the reference surface, for example, there is a reflective wall surface facing the semiconductor laser 1 across a space where the object 11 is to enter. When the object 11 does not exist in the radiation direction of the semiconductor laser 1, the light from the reflection wall surface returns to the semiconductor laser 1.

In addition, any one of the inner and outer surfaces of the transparent cover that protects the semiconductor laser 1 that is not subjected to the antireflection treatment can be used as the reference surface. FIG. 28 is a diagram showing a schematic configuration of a main part of an incident / exit part of the semiconductor laser 1. In FIG. 28, 140 is a sealed case that houses the semiconductor laser 1, 141 is a transparent cover (transparent body) such as glass provided on the front surface of the semiconductor laser 1 to protect the semiconductor laser 1, and 142 is on the surface of the transparent cover 141. An antireflection film (AR coating) is provided.
The transparent cover 141 is provided by being fitted into the window portion of the sealed case 140. The semiconductor laser 1 is assembled in the sealed case 140 with the laser light incident / exit surface as the front surface facing the transparent cover 141.

  When laser light is input / output through a transparent body such as glass, the laser light is reflected slightly at the interface between the transparent body and air. In order to prevent such reflection, the surface of the transparent body is exclusively coated with a filler in which a low refractive index material is dispersed to form an antireflection film. Also in the present embodiment, an antireflection film 142 is provided on the surface of the transparent cover 141 in order to suppress unnecessary reflection on the transparent cover 141 serving as a laser light incident / exit surface. At this time, the inner surface of the transparent cover 141 is provided. Only the antireflection film 142 is provided, and the antireflection film is not formed on the outer surface thereof, so that the laser beam is reflected on the outer surface of the transparent cover 141. A part of the laser light output from the semiconductor laser 1 is reflected by the outer surface of the transparent cover 141 and returned to the semiconductor laser 1.

  Of course, the outer surface of the transparent cover 141 is not subjected to the antireflection treatment, but the semiconductor laser 1 is intentionally subjected to a treatment necessary for obtaining a reflected light having an intensity causing a self-coupling effect. May be. Specifically, the outer surface of the transparent cover 141 can be mirror-polished, or an optical film having a certain degree of reflectance can be formed. According to the configuration shown in FIG. 28, when the object 11 is not present in the radiation direction of the semiconductor laser 1, a part of the laser light emitted from the semiconductor laser 1 is reflected by the outer surface of the transparent cover 141. Return to.

[Eleventh embodiment]
Next, an eleventh embodiment of the present invention will be described. Also in the present embodiment, the configuration of the physical quantity sensor is the same as that of the ninth embodiment, and therefore will be described using the reference numerals in FIG.
In the ninth embodiment, the signal extraction unit 7 counts the number of MHPs included in the output of the averaging processing unit 22 in integer units. However, as described in the ninth embodiment, when the timing of the MHP counting period with respect to the diaphragm control signal is controlled with high precision and the MHP is averaged over a plurality of counting periods, the counting of the averaging processing unit 22 is performed. The unit 223 can count the MHP from the beginning to the end of the counting period in units after the decimal point.

  In this way, in the present embodiment, MHP can be counted in units of decimals, and the number of decimals can be substituted for the number of MHPs in equations (2) to (5). The resolution can be improved.

[Twelfth embodiment]
In the first to eleventh embodiments, the photodiode 2 and the current-voltage conversion amplifier 5 are used as detection means for detecting an electric signal including an MHP waveform. However, the MHP waveform is extracted without using the photodiode. It is also possible to do. FIG. 29 is a block diagram showing a configuration of a physical quantity sensor according to the twelfth embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIG. The physical quantity sensor of the present embodiment uses a voltage detection circuit 24 as detection means instead of the photodiode 2 and the current-voltage conversion amplifier 5 of the first and second embodiments.

  The voltage detection circuit 24 detects and amplifies the voltage between the terminals of the semiconductor laser 1, that is, the anode-cathode voltage. When interference occurs between the laser light emitted from the semiconductor laser 1 and the return light from the object 11, an MHP waveform appears in the voltage between the terminals of the semiconductor laser 1. Therefore, it is possible to extract the MHP waveform from the voltage between the terminals of the semiconductor laser 1.

  The signal extraction unit 7 counts the number of MHPs included in the output voltage of the voltage detection circuit 24 for each of the first counting period Q1 and the second counting period Q2. Other configurations of the physical quantity sensor are the same as those in the first and second embodiments. Similarly to the other embodiments, the signal extraction unit 7 a may be used instead of the signal extraction unit 7.

  Thus, in this embodiment, an MHP waveform can be extracted without using a photodiode, and the physical quantity sensor components can be reduced as compared with the first to eleventh embodiments. The cost can be reduced. In this embodiment, since no photodiode is used, the influence of disturbance light can be eliminated.

  In the present embodiment, it is preferable that the drive current supplied from the laser driver 4 to the semiconductor laser 1 is controlled near the laser oscillation threshold current. Thereby, it becomes easy to extract MHP from the voltage between the terminals of the semiconductor laser 1.

  In the first to twelfth embodiments, at least the signal extraction unit 7 and the calculation unit 8 can be realized by, for example, a computer including a CPU, a storage device, and an interface, and a program for controlling these hardware resources. it can. A program for operating such a computer is provided in a state of being recorded on a recording medium such as a flexible disk, a CD-ROM, a DVD-ROM, or a memory card. The CPU writes the read program into the storage device, and executes the processing described in the embodiment in accordance with this program.

  In the first to twelfth embodiments, the distance / speed meter is described as an example of the physical quantity sensor. However, the present invention is not limited to this, and a distance meter may be used. It may be a sensor that measures other physical quantities.

  The present invention can be applied to a technique for measuring a physical quantity of an object from information on interference caused by a self-coupling effect between laser light emitted from a semiconductor laser and return light from the object.

It is a block diagram which shows the structure of the physical quantity sensor which concerns on the 1st Embodiment of this invention. It is principal part structure sectional drawing of the semiconductor laser in the 1st Embodiment of this invention. In the first embodiment of the present invention, a diaphragm control signal supplied from the diaphragm driver to the semiconductor laser, a temporal change in the oscillation wavelength of the semiconductor laser, a drive current supplied from the laser driver to the semiconductor laser, and an optical output of the semiconductor laser FIG. It is a figure for demonstrating a mode hop pulse. It is a figure which shows the relationship between the oscillation wavelength of a semiconductor laser, and the output waveform of a photodiode. It is a block diagram which shows an example of a structure of the calculating part in the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the calculating part in the 1st Embodiment of this invention. It is principal part structure sectional drawing of the semiconductor laser in the 2nd Embodiment of this invention. It is a figure which shows the time change of the drive current at the time of making it emit light using the conventional drive current modulation type semiconductor laser, and the oscillation wavelength of a semiconductor laser. It is the figure which expanded the time change of the oscillation wavelength of the semiconductor laser of FIG. In the third embodiment of the present invention, the diaphragm control signal supplied from the diaphragm driver to the semiconductor laser, the time variation of the oscillation wavelength of the semiconductor laser, the drive current supplied from the laser driver to the semiconductor laser, and the optical output of the semiconductor laser FIG. It is a block diagram which shows the structure of the physical quantity sensor which concerns on the 4th Embodiment of this invention. It is a figure which shows another example of the diaphragm control signal supplied to the semiconductor laser from the diaphragm driver in the 3rd Embodiment of this invention, and 4th Embodiment, and the time change of the oscillation wavelength of a semiconductor laser. It is a block diagram which shows the structure of the physical quantity sensor which concerns on the 5th Embodiment of this invention. It is a figure which shows one example of the drive current-light output characteristic of a semiconductor laser. It is a block diagram which shows the structure of the physical quantity sensor which concerns on the 6th Embodiment of this invention. It is a block diagram which shows the structure of the physical quantity sensor which concerns on the 7th Embodiment of this invention. It is a block diagram which shows one example of a structure of the signal extraction part in the 8th Embodiment of this invention. It is a block diagram which shows one example of a structure of the count result correction | amendment part in the signal extraction part of FIG. It is a figure for demonstrating operation | movement of the signal extraction part of FIG. It is a figure which shows one example of the frequency distribution of the period in the 8th Embodiment of this invention. It is a figure for demonstrating the correction principle of the count result of the counter in the 8th Embodiment of this invention. It is a block diagram which shows the structure of the physical quantity sensor which concerns on the 9th Embodiment of this invention. It is a figure which shows the diaphragm control signal and mode hop pulse which are supplied to a semiconductor laser from a diaphragm driver. It is a block diagram which shows an example of a structure of the averaging process part in the 9th Embodiment of this invention. It is a figure for demonstrating operation | movement of the averaging process part in the 9th Embodiment of this invention. It is a block diagram which shows the structure of the physical quantity sensor which concerns on the 10th Embodiment of this invention. It is a figure which shows the principal part schematic structure of the entrance / exit part of the semiconductor laser which concerns on the 10th Embodiment of this invention. It is a block diagram which shows the structure of the physical quantity sensor which concerns on the 12th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2, 13 ... Photodiode, 3 ... Lens, 4, 4a ... Laser driver, 5, 14 ... Current-voltage conversion amplifier, 7, 7a ... Signal extraction part, 8 ... Operation part, 9 ... Display apparatus DESCRIPTION OF SYMBOLS 10,10a ... Diaphragm driver, 11 ... Object, 12 ... Beam splitter, 15 ... Object detection part, 16, 17, 18 ... Light output control part, 19 ... Reference signal generation circuit, 20 ... PLL circuit, 21 ... Voltage control Oscillator, 22 ... Averaging processing unit, 23 ... Phase detection unit, 24 ... Voltage detection circuit, 71 ... Determination unit, 72 ... Logical product operation unit, 73 ... Counter, 74 ... Count result correction unit, 75 ... Storage unit, 80 ... distance / speed calculation unit, 81 ... history displacement calculation unit, 82 ... storage unit, 83 ... state determination unit, 84 ... distance / speed determination unit, 220 ... A / D converter, 221 ... memory, 222 ... averaging calculation unit , 22 ... counter, 224 ... state determination unit, 740 ... period measuring unit, 741 ... frequency distribution generator, 742 ... representative value calculating unit, 743 ... correction value calculating unit.

Claims (30)

A wavelength tunable semiconductor laser having a wavelength tunable mechanism capable of controlling the oscillation wavelength by adjusting the resonator length according to the control signal, and emitting a laser beam to the measurement target;
A laser driver for supplying a driving current to the semiconductor laser to oscillate the semiconductor laser;
Oscillation wavelength modulation means for modulating the oscillation wavelength of the semiconductor laser by supplying the control signal to the semiconductor laser;
Detection means for detecting an electrical signal including an interference waveform generated by a self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object;
A physical quantity sensor comprising: measurement means for measuring the physical quantity of the measurement target from information on the interference waveform included in the output signal of the detection means. The physical quantity sensor according to claim 1,
The oscillation wavelength modulation means alternately includes a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and a second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously. The semiconductor laser is operated as follows:
The measuring means includes
Signal extraction means for counting the number of the interference waveforms included in the output signal of the detection means for each of the counting period on the increasing side of the oscillation wavelength and the counting period on the decreasing side of the oscillation wavelength of the semiconductor laser;
A physical quantity sensor comprising: a calculation means for calculating a physical quantity of the measurement object from a counting result of the signal extraction means. The physical quantity sensor according to claim 2,
The signal extraction means includes
Counting means for counting the number of interference waveforms included in the output signal of the detection means for each of the counting period on the increase side of the oscillation wavelength and the counting period on the decrease side of the oscillation wavelength of the semiconductor laser;
A period measuring means for measuring the period of the interference waveform during the counting period in which the counting means counts the number of interference waveforms every time the interference waveform is input;
Frequency distribution creating means for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of the period measuring means,
Representative value calculating means for calculating a representative value of the distribution of the period of the interference waveform from the frequency distribution;
From the frequency distribution, the sum Ns of the frequencies of the class that is less than or equal to the first predetermined number of times of the representative value and the sum Nw of the frequencies of the class that are greater than or equal to the second predetermined number of times of the representative value are obtained, and A physical quantity sensor comprising correction value calculation means for correcting the count result of the counting means based on the frequencies Ns and Nw and outputting the corrected count result. The physical quantity sensor according to claim 2,
The physical quantity sensor according to claim 1, wherein the physical quantity of the measurement target is at least one of a distance from the measurement target and a speed of the measurement target. The physical quantity sensor according to claim 1,
The physical quantity sensor, wherein the laser driver supplies the pulsed drive current to the semiconductor laser to cause the semiconductor laser to emit light in pulses. The physical quantity sensor according to claim 5,
Furthermore, a light detector for detecting return light that receives return light from the measurement object and converts it into an electrical signal;
A physical quantity sensor comprising: object detection means for determining whether or not a measurement object exists in the laser light emission direction based on an output signal of the return light detection light receiver. The physical quantity sensor according to claim 1,
The physical quantity sensor further comprises: a light output control means for controlling a drive current supplied from the laser driver to the semiconductor laser so that the light output of the semiconductor laser becomes constant. The physical quantity sensor according to claim 1,
The physical quantity further comprises light output control means for controlling a drive current supplied from the laser driver to the semiconductor laser so that the light output of the semiconductor laser becomes an appropriate value according to an ambient temperature. Sensor. The physical quantity sensor according to claim 1,
Furthermore, a light detector for detecting return light that receives return light from the measurement object and converts it into an electrical signal;
A light output control means for controlling a drive current supplied from the laser driver to the semiconductor laser so that a return light amount from the measurement object is constant based on an output signal of the return light detecting light receiver; A physical quantity sensor comprising: The physical quantity sensor according to claim 1,
Furthermore, reference signal generating means for generating a reference signal,
Voltage-controlled oscillation means for generating a modulation signal;
The voltage of the reference signal and the modulation signal included in the output of the detection means are compared so that the modulation signal is synchronized with the reference signal or the phase difference between the modulation signal and the reference signal is constant. Phase control means for controlling the control oscillation means,
The laser driver modulates the drive current with a modulation signal output from the voltage controlled oscillation means,
The physical quantity sensor characterized in that the oscillation wavelength modulating means synchronizes the control signal with the reference signal. The physical quantity sensor according to claim 10,
Further, the interference waveform included in the output signal of the detecting means is averaged over a plurality of counting periods on the oscillation wavelength increasing side and averaged over a plurality of counting periods on the oscillation wavelength decreasing side Comprising processing means,
The oscillation wavelength modulation means alternately includes a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and a second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously. The semiconductor laser is operated as follows:
The measuring means includes
Signal extraction means for counting the number of the interference waveforms included in the output signal of the detection means for each of the counting period on the increasing side of the oscillation wavelength and the counting period on the decreasing side of the oscillation wavelength of the semiconductor laser;
Comprising calculation means for calculating the physical quantity of the measurement object from the counting result output from the averaging processing means,
The averaging processing means includes
An averaging calculation means for performing the averaging;
An averaging processing counting means for counting the number of interference waveforms after the averaging for each of the counting period on the increase side of the oscillation wavelength and the counting period on the decrease side of the oscillation wavelength of the semiconductor laser;
When the change in the counting result output from the signal extracting means is within a predetermined range, the counting result output from the averaging processing counting means is output to the calculating means, and the counting output from the signal extracting means is output. A physical quantity sensor comprising: a state determination unit that outputs a count result output from the signal extraction unit to the calculation unit when a change in the result exceeds a predetermined range. The physical quantity sensor according to claim 11,
The signal extraction means includes
Pre-averaging counting means for counting the number of interference waveforms included in the output signal of the detecting means for each of the counting period on the increasing side of the oscillation wavelength and the counting period on the decreasing side of the oscillation wavelength of the semiconductor laser;
A period measuring means for measuring the period of the interference waveform during the counting period in which the counting means before the averaging process counts the number of interference waveforms every time the interference waveform is input;
Frequency distribution creating means for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of the period measuring means,
Representative value calculating means for calculating a representative value of the distribution of the period of the interference waveform from the frequency distribution;
From the frequency distribution, the sum Ns of the frequencies of the class that is less than or equal to the first predetermined number of times of the representative value and the sum Nw of the frequencies of the class that are greater than or equal to the second predetermined number of times of the representative value are obtained, and Correction value calculation means for correcting the counting result of the pre-averaging processing means based on the frequency Ns and Nw, and outputting the corrected counting result to the averaging processing means,
Instead of observing the change in the counting result output from the signal extraction unit, the state determination unit observes a change in the representative value of the period distribution calculated by the signal extraction unit, and the change in the representative value is When within a predetermined range, the counting result output from the averaging processing counting means is output to the calculating means, and when the change in the representative value exceeds a predetermined range, the counting output from the signal extracting means A physical quantity sensor comprising: state determination means for outputting a result to the calculation means. The physical quantity sensor according to claim 11,
Further, a phase change of the interference waveform included in the output signal of the detection means is detected, and the oscillation wavelength modulation means is supplied to the semiconductor laser so that the rate of change of the oscillation wavelength of the semiconductor laser becomes constant. A physical quantity sensor comprising phase detection means for controlling a control signal. The physical quantity sensor according to claim 11,
The physical quantity sensor according to claim 1, wherein the post-averaging counting means counts the interference waveform after the averaging in units of decimals. The physical quantity sensor according to claim 7,
The physical quantity sensor according to claim 1, wherein the laser driver supplies the semiconductor laser with the drive current in the vicinity of a threshold current for laser oscillation. Oscillation that oscillates the semiconductor laser by supplying a drive current to a wavelength tunable semiconductor laser that emits laser light to the object to be measured with a wavelength tunable mechanism that can control the oscillation wavelength by adjusting the resonator length according to the control signal Procedure and
An oscillation wavelength modulation procedure for modulating the oscillation wavelength of the semiconductor laser by supplying the control signal to the semiconductor laser;
A detection procedure for detecting an electrical signal including an interference waveform caused by a self-coupling effect between the laser light emitted from the semiconductor laser and the return light from the measurement object;
A physical quantity measurement method comprising: a measurement procedure for measuring the physical quantity of the measurement target from information on the interference waveform included in the output signal obtained by the detection procedure. The physical quantity measuring method according to claim 16, wherein
In the oscillation wavelength modulation procedure, there are alternately a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and a second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously. The semiconductor laser is operated as follows:
The measurement procedure is as follows:
A signal extraction procedure for counting the number of interference waveforms included in the output signal obtained in the detection procedure for each of the counting period on the increase side of the oscillation wavelength and the counting period on the decrease side of the oscillation wavelength of the semiconductor laser;
A physical quantity measuring method comprising: an arithmetic procedure for calculating a physical quantity of the measurement object from a counting result of the signal extraction procedure. The physical quantity measuring method according to claim 17, wherein
The signal extraction procedure includes:
A counting procedure for counting the number of the interference waveforms included in the output signal obtained by the detection procedure for each of the counting period on the increasing side of the oscillation wavelength and the counting period on the decreasing side of the oscillation wavelength of the semiconductor laser;
A period measurement procedure for measuring the period of the interference waveform during the counting period for counting the number of interference waveforms in this counting procedure every time the interference waveform is input;
A frequency distribution creating procedure for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of this cycle measuring procedure,
A representative value calculation procedure for calculating a representative value of the period distribution of the interference waveform from the frequency distribution;
From the frequency distribution, the sum Ns of the frequencies of the class that is less than or equal to the first predetermined number of times of the representative value and the sum Nw of the frequencies of the class that are greater than or equal to the second predetermined number of times of the representative value are obtained, and A physical quantity measuring method comprising: a correction value calculating procedure for correcting the counting result of the counting procedure based on the frequencies Ns and Nw and outputting the corrected counting result as the counting result of the signal extraction procedure. The physical quantity measuring method according to claim 17, wherein
The physical quantity of the measurement object is at least one of a distance to the measurement object and a speed of the measurement object. The physical quantity measuring method according to claim 16, wherein
In the oscillation procedure, the pulsed drive current is supplied to the semiconductor laser to cause the semiconductor laser to emit light in pulses. The physical quantity measuring method according to claim 20, wherein
Further, a return light detection procedure for receiving return light from the measurement object and converting it into an electrical signal,
A physical quantity measurement method comprising: an object detection procedure for determining whether or not a measurement target exists in the radiation direction of the laser beam based on an output signal obtained by the return light detection procedure. The physical quantity measuring method according to claim 16, wherein
The physical quantity measurement method further comprises a light output control procedure for controlling a drive current supplied to the semiconductor laser so that the light output of the semiconductor laser becomes constant. The physical quantity measuring method according to claim 16, wherein
The physical quantity measurement method further comprises a light output control procedure for controlling a drive current supplied to the semiconductor laser so that the light output of the semiconductor laser becomes an appropriate value according to an ambient temperature. The physical quantity measuring method according to claim 16, wherein
Further, a return light detection procedure for receiving return light from the measurement object and converting it into an electrical signal,
A light output control procedure for controlling a drive current supplied to the semiconductor laser so that a return light amount from the measurement target is constant based on an output signal obtained by the return light detection procedure. Characteristic physical quantity measurement method. The physical quantity measuring method according to claim 16, wherein
Furthermore, a reference signal generation procedure for generating a reference signal;
A voltage controlled oscillation procedure for generating a modulation signal;
The voltage of the reference signal and the modulation signal included in the output of the detection procedure are compared so that the modulation signal is synchronized with the reference signal or the phase difference between the modulation signal and the reference signal is constant. A phase control procedure for controlling the controlled oscillation procedure,
The oscillation procedure modulates the drive current with a modulation signal output in the voltage controlled oscillation procedure,
In the oscillation wavelength modulation procedure, the control signal is synchronized with the reference signal. The physical quantity measuring method according to claim 25,
Further, the interference waveform included in the output signal obtained in the detection procedure is averaged for a plurality of counting periods on the oscillation wavelength increasing side and averaged for a plurality of counting periods on the oscillation wavelength decreasing side. With an averaging process procedure
In the oscillation wavelength modulation procedure, there are alternately a first oscillation period including at least a period in which the oscillation wavelength continuously increases monotonously and a second oscillation period including at least a period in which the oscillation wavelength continuously decreases monotonously. The semiconductor laser is operated as follows:
The measurement procedure is as follows:
A signal extraction procedure for counting the number of interference waveforms included in the output signal obtained in the detection procedure for each of the counting period on the increase side of the oscillation wavelength and the counting period on the decrease side of the oscillation wavelength of the semiconductor laser;
Comprising a calculation procedure for calculating the physical quantity of the measurement object from the counting result obtained in the averaging process procedure,
The averaging process procedure is as follows:
An averaging calculation procedure for performing the averaging;
A counting procedure after averaging processing for counting the number of interference waveforms after the averaging for each of the counting period on the increase side of the oscillation wavelength of the semiconductor laser and the counting period on the decrease side of the oscillation wavelength;
When the change in the count result of the signal extraction procedure is within a predetermined range, the count result of the post-averaging count procedure is used in the calculation procedure, and the change in the count result of the signal extraction procedure exceeds a predetermined range In this case, the physical quantity measuring method includes a state determination procedure for using the counting result of the signal extraction procedure in the calculation procedure. The physical quantity measuring method according to claim 26,
The signal extraction procedure includes:
A count before the averaging process that counts the number of the interference waveforms included in the output signal obtained by the detection procedure for each of the counting period on the increasing side of the oscillation wavelength and the counting period on the decreasing side of the oscillation wavelength of the semiconductor laser. Procedure and
A period measurement procedure for measuring the period of the interference waveform during the counting period in which the number of interference waveforms is counted in the counting procedure before the averaging process every time the interference waveform is input;
A frequency distribution creating procedure for creating a frequency distribution of the period of the interference waveform during the counting period from the measurement result of this cycle measuring procedure,
A representative value calculation procedure for calculating a representative value of the period distribution of the interference waveform from the frequency distribution;
From the frequency distribution, the sum Ns of the frequencies of the class that is less than or equal to the first predetermined number of times of the representative value and the sum Nw of the frequencies of the class that are greater than or equal to the second predetermined number of times of the representative value, A correction value calculating procedure for correcting the counting result of the pre-averaging counting procedure based on the frequencies Ns and Nw, and outputting the corrected counting result as the counting result of the signal extraction procedure,
Instead of observing a change in the counting result of the signal extraction procedure, the state determination procedure observes a change in the representative value of the period distribution calculated in the signal extraction procedure, and the change in the representative value is within a predetermined range. In the case where the count result of the counting procedure after the averaging process is used in the calculation procedure, and when the change of the representative value exceeds a predetermined range, the count result of the signal extraction procedure is used in the calculation procedure A physical quantity measurement method comprising a determination procedure. The physical quantity measuring method according to claim 26,
Furthermore, a control signal supplied to the semiconductor laser is detected so that the change rate of the oscillation wavelength of the semiconductor laser is constant by detecting a phase change of the interference waveform included in the output signal obtained by the detection procedure. A physical quantity measurement method comprising a phase detection procedure for controlling the phase. The physical quantity measuring method according to claim 26,
The counting procedure after the averaging process is characterized in that the interference waveform after the averaging is counted in units of decimals. The physical quantity measuring method according to claim 22,
In the oscillation procedure, the drive current in the vicinity of a laser oscillation threshold current is supplied to the semiconductor laser.

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