JP5198844B2 - Cloudiness detector and mirror-cooled dew point meter - Google Patents

Description

  The present invention relates to a fog detection device that detects fogging of glass or the like, and a mirror-cooled dew point meter that detects a dew point of a gas.

  Conventionally, as a humidity measurement method, a dew point detection method is known in which a dew point is detected by measuring the temperature when the temperature of a gas to be measured is reduced and a part of water vapor contained in the gas to be measured is condensed. ing. For example, in Patent Document 1, a mirror is cooled by using an electronic cooler or the like, a change in the intensity of reflected light on the surface of the cooled mirror is detected, and the temperature of the mirror surface at this time is measured. A mirror-cooled dew point meter that detects the dew point of moisture in a gas to be measured is disclosed. There are two types of mirror-cooled dew point meters depending on the type of reflected light used. One is a specular reflection light detection method using specular reflection light, and the other is a scattered light detection method using scattered light.

  FIG. 6 shows a main part of a conventional mirror-cooled dew point meter that employs a regular reflection light detection method. This specular cooling type dew point meter includes a chamber 101 into which a gas to be measured flows, and a thermoelectric cooling element (Peltier element) 102 provided inside the chamber 101. A bolt 104 is attached to the cooling surface of the thermoelectric cooling element 102 via a copper block 103. The upper surface of the bolt 104 attached to the copper block 103 is a mirror surface. A temperature sensor 105 made of a winding type resistance temperature detector is embedded in a side portion of the copper block 103. In addition, at the upper part of the chamber 101, a light emitting element 106 that irradiates light obliquely with respect to the upper surface (mirror surface) of the bolt 104, and a light receiving element that receives specularly reflected light emitted from the light emitting element 106 to the mirror surface An element 107 is provided.

  In this mirror-cooled dew point meter, the mirror surface of the bolt 104 is exposed to the gas to be measured flowing into the chamber 101. If there is no condensation on the mirror surface of the bolt 104, almost all of the light emitted from the light emitting element 106 is regularly reflected and received by the light receiving element 107. Therefore, when there is no condensation on the mirror surface, the intensity of the reflected light received by the light receiving element 107 is high. When the current to the thermoelectric cooling element 102 is increased and the temperature of the cooling surface of the thermoelectric cooling element 102 is lowered, water vapor contained in the gas to be measured is condensed on the mirror surface of the bolt 104, and the condensed water droplets are emitted from the light emitting element 106. Part of the irradiated light is absorbed or diffusely reflected. Thereby, the intensity of the reflected light (regular reflected light) received by the light receiving element 107 is reduced. By detecting a change in the specular reflection light on the mirror surface of the bolt 104, it is possible to know a change in the state on the mirror surface, that is, that moisture has adhered to the mirror surface. Further, by indirectly measuring the temperature of the mirror surface with the temperature sensor 105 at this time, it is possible to know the dew point of moisture in the gas to be measured.

  FIG. 7 shows a main part of a conventional mirror-cooled dew point meter adopting the scattered light detection method. This mirror-cooled dew point meter has substantially the same configuration as the mirror-cooled dew point meter shown in FIG. 6, but the mounting position of the light receiving element 107 is different. In this mirror-cooled dew point meter, the light receiving element 107 is provided at a position for receiving scattered light, not at a position for receiving regular reflection light of light emitted from the light emitting element 106 to the mirror surface of the bolt 104. .

  If there is no condensation on the mirror surface of the bolt 104, almost all of the light emitted from the light emitting element 106 is regularly reflected, and the amount of light received by the light receiving element 107 is extremely small. Therefore, when no condensation occurs on the mirror surface of the bolt 104, the intensity of the reflected light received by the light receiving element 107 is small. When the current to the thermoelectric cooling element 102 is increased and the temperature of the cooling surface of the thermoelectric cooling element 102 is lowered, water vapor contained in the gas to be measured is condensed on the mirror surface of the bolt 104, and the condensed water droplets are emitted from the light emitting element 106. Part of the irradiated light is absorbed or diffusely reflected. As a result, the intensity of irregularly reflected light (scattered light) received by the light receiving element 107 increases. By detecting the change in the scattered light on the mirror surface of the bolt 104, it is possible to know that moisture has adhered to the mirror surface. Further, by indirectly measuring the temperature of the mirror surface with the temperature sensor 105 at this time, it is possible to know the dew point of moisture in the gas to be measured.

JP 2005-283506 A

As described above, the mirror-cooled dew point meter disclosed in Patent Document 1 has a flat mirror surface for detecting dew condensation. Therefore, in order to perform accurate and high-resolution measurement, the laser beam emitted from the light emitting element is a thin beam. In addition, it is necessary to strictly adjust the optical axis of the optical component, so that there are many components and it is difficult to adjust the optical axis of the optical component.
Such a problem occurs not only in a mirror-cooled dew point meter but also in a fog detection device that detects fog on a window glass or the like.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fog detection device and a mirror-cooled dew point meter in which the configuration of the optical unit is simple and strict optical axis adjustment is unnecessary.

The fog detection device of the present invention includes an elliptic spherical reflector whose mirror surface or the back surface of the mirror surface is exposed to the gas to be measured, a laser diode that irradiates light to the elliptic spherical reflector, and the elliptic spherical reflector. the reflected light is received and a photodiode for converting into an electric signal, the laser diode is arranged so that its emitting surface is positioned at one focal point of the ellipsoid reflector, said photodiode, The incident surface is disposed so as to be positioned at the other focal point of the elliptical spherical reflecting mirror.
In addition , one configuration example of the fogging detection apparatus of the present invention is characterized in that the elliptic spherical inner wall surface of the elliptic prism is the elliptic spherical reflector.

Further, the mirror-cooled dew point meter of the present invention includes a clouding detection device, a cooling means for cooling the elliptic spherical reflector, a temperature sensor for measuring the temperature of the elliptic spherical reflector, and the reflection received by the photodiode. Detecting means for detecting dew condensation generated on the elliptical spherical reflector or the back surface thereof based on the intensity of light, and using the temperature measured by the temperature sensor when the dew condensation is detected as a dew point temperature of the gas to be measured; It is characterized by having.

  According to the present invention, the mirror surface or the ellipsoidal reflecting mirror whose back surface is exposed to the gas to be measured is provided, and the light projecting means is disposed so that the exit surface is located at one focal point of the ellipsoidal reflecting mirror. As a result, it is possible to realize a fog detection device and a mirror-cooled dew point meter that have a simple optical configuration and that do not require strict optical axis adjustment.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1A is a side sectional view of an optical part of a specular cooling type dew point meter according to the first embodiment of the present invention, and FIG. 1B is a sectional view taken along line AA in FIG. 1 (C) is a cross-sectional view taken along line BB in FIG. 1 (A).

  The mirror-cooled dew point meter of the present embodiment employs a regular reflection light detection method. The optical part of this mirror-cooled dew point meter constitutes a laser diode 1 that emits laser light, a photodiode 2 that receives the laser light and converts it into an electrical signal, and a bottom part of the container into which the gas to be measured flows. The bottom member 3, the top member 4 constituting the top surface part of the container, the side member 5 constituting the side part of the container, the holder 6 for fixing the laser diode 1 to the top member 4, and the photodiode 2 as the top member 4 A heat transfer copper block 8 provided in contact with the bottom member 3, a temperature sensor 9 made of a thin film resistance temperature detector made of, for example, platinum embedded in the copper block 8, and a cooling surface Has a Peltier element 10 serving as a cooling means provided so as to be in contact with the copper block 8, and a heat dissipation heat sink 11 provided so as to be in contact with the heating surface of the Peltier element 10.The laser diode 1 constitutes light projecting means, and the photodiode 2 constitutes light receiving means.

The bottom surface member 3 is formed with a concave ellipsoidal reflecting mirror 12 with respect to the upper surface of the container on which the laser diode 1 and the photodiode 2 are arranged. The bottom member 3 and the elliptical spherical reflecting mirror 12 are preferably made of a material having good thermal conductivity, for example, a metal.
The side member 5 fixes the top member 4 on the bottom member 3 with a predetermined distance. Further, the side member 5 is formed with a vent hole 13 serving as an inlet of the container and a vent hole 14 serving as an outlet of the container.

  The laser diode 1 is fixed to the upper surface member 4 by the holder 6, and the photodiode 2 is fixed to the upper surface member 4 by the holder 7. At this time, the laser diode 1 is fixed so that its emission surface is located at one focal point f1 of the elliptical spherical reflecting mirror 12, and the photodiode 2 has its incident surface at the other focal point f2 of the elliptical spherical reflecting mirror 12. It is fixed to be positioned. The laser diode 1 is connected to a laser driver described later via an electric wire 11, and the photodiode 2 is connected to a reflected light intensity detection unit described later via an electric wire 12.

FIG. 2 is a block diagram showing the configuration of the detection unit of the mirror-cooled dew point meter of the present embodiment. The detection unit 20 of the mirror-cooled dew point meter includes a laser driver 21, a reflected light intensity detection unit 22, a cooling control unit 23, a dew point detection unit 24, and a display unit 25.
Next, the operation of the mirror-cooled dew point meter according to the present embodiment will be described with reference to FIGS. The gas to be measured flows into the container through the vent hole 13, flows in the direction of the arrow 15 in FIG. 1A, and flows out of the container from the vent hole.

The laser driver 21 emits laser light from the laser diode 1. The laser light emitted from the laser diode 1 passes through the measurement gas atmosphere in the container, is reflected by the ellipsoidal reflecting mirror 12, passes through the measurement gas atmosphere again, and enters the photodiode 2.
The photodiode 2 converts the received reflected light into an electrical signal.

The reflected light intensity detector 22 converts the output current of the photodiode 2 into a voltage and amplifies it, obtains the intensity of the reflected light from the amplified signal, and compares the intensity of the reflected light with a predetermined threshold value.
The elliptical spherical reflecting mirror 12 is exposed to the gas to be measured. If no condensation occurs on the elliptical spherical reflecting mirror 12, almost all of the light emitted from the laser diode 1 is regularly reflected and received by the photodiode 2. Is done. Therefore, when no condensation occurs on the elliptical spherical reflecting mirror 12, the intensity of the reflected light received by the photodiode 2 is large and never falls below a predetermined threshold.

The cooling control unit 23 increases the current supplied to the Peltier element 10 when the intensity of the reflected light exceeds the threshold value as a result of the comparison between the reflected light intensity by the reflected light intensity detection unit 22 and the threshold value. As a result, the temperature of the cooling surface of the Peltier element 10 decreases.
When the temperature of the cooling surface of the Peltier element 10, that is, the temperature of the elliptical spherical reflector 12 decreases, water vapor contained in the gas to be measured condenses on the elliptical spherical reflector 12, and one of the light irradiated from the laser diode 1. Part is irregularly reflected. Thereby, the intensity | strength of the reflected light which injects into the photodiode 2 falls, and becomes below a threshold value. By comparing the intensity of the reflected light with the threshold value in this way, it is possible to detect the dew condensation that has occurred on the elliptical spherical reflecting mirror 12.

  The cooling control unit 23 reduces the current supplied to the Peltier element 10 when the intensity of the reflected light becomes equal to or less than the threshold value. Thereby, the fall of the temperature of the cooling surface of the Peltier element 10 is suppressed, and generation | occurrence | production of dew condensation is suppressed. By suppressing the dew condensation, the intensity of the reflected light incident on the photodiode 2 increases and exceeds the threshold value, and the cooling control unit 23 increases the current supplied to the Peltier element 10. As described above, by repeatedly increasing and decreasing the current supplied to the Peltier element 10, the temperature of the cooling surface of the Peltier element 10 is adjusted so that the intensity of the reflected light incident on the photodiode 2 becomes substantially equal to the threshold value.

  The dew point detection unit 24 uses the adjusted temperature, that is, the temperature measured by the temperature sensor 9 when the intensity of the reflected light is within a predetermined range centered on the threshold value, to cause the condensation on the elliptic spherical reflector 12 to occur. Is the temperature (dew point temperature) at which has reached an equilibrium state. The value of the dew point temperature is displayed on the display unit 25.

  In the mirror-cooled dew point meter as described above, even if the position and angle of the laser diode 1 vary, no geometrically returning light to the laser diode 1 is generated, and all the light emitted from the laser diode 1 is already present. It gathers in the photodiode 2 arranged at one focal point. Therefore, it is not necessary to use collimated light in order to improve the light receiving sensitivity, and it is not necessary to incline the optical component at a predetermined angle in order to prevent return light noise, so that the optical axes of the laser diode 1 and the photodiode 2 can be changed. There is no need to adjust strictly.

That is, in this embodiment, it is not necessary to use an optical component such as a lens, and it is not necessary to strictly adjust the inclination of the optical axis of the laser diode 1 (α, α ′ in FIG. 1). It is not necessary to strictly adjust the inclination of the optical axis (β in FIG. 1). Further, if the accuracy of the optical axes of the laser diode 1 and the photodiode 2 is a general machining accuracy level, there is a slight displacement (d1, d2 in FIG. 1) of the laser diode 1 and the photodiode 2 in the optical axis direction. There is no problem.
In the present embodiment, since the elliptical spherical reflecting mirror 12 has a large area, it has good resistance to noise caused by dust adhering to the elliptical spherical reflecting mirror 12.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 3A is a side sectional view of an optical part of a mirror-cooled dew point meter according to the second embodiment of the present invention, and FIG. 3B is a sectional view taken along line AA in FIG. 3 (C) is a cross-sectional view taken along line BB in FIG. 3 (A), and the same components as those in FIGS. 1 (A) to 1 (C) are denoted by the same reference numerals.

  The mirror-cooled dew point meter of the present embodiment employs a scattered light detection method, and the position of the photodiode 2a is different from that of the first embodiment. The incident surface of the photodiode 2a is fixed at a position different from the focal point f2 of the elliptical spherical reflecting mirror 12, preferably at a position near the focal point f2 (a position for receiving scattered light from the elliptical spherical reflecting mirror 12).

Since the basic configuration of the detection unit 20 of the mirror-cooled dew point meter of the present embodiment is the same as that of the first embodiment, the operation of the present embodiment will be described using the reference numerals in FIG.
If condensation does not occur in the elliptical spherical reflecting mirror 12, almost all of the light emitted from the laser diode 1 is regularly reflected, and the amount of light received by the photodiode 2a is extremely small. Therefore, when no condensation occurs on the elliptical spherical reflecting mirror 12, the intensity of the reflected light received by the photodiode 2a is small and never exceeds a predetermined threshold.

  Similar to the first embodiment, the reflected light intensity detector 22 determines the intensity of the reflected light from the output of the photodiode 2 and compares the intensity of the reflected light with a predetermined threshold. Note that the comparison threshold value in the present embodiment is for detecting scattered light, and therefore is different from the threshold value for detecting a decrease in the intensity of specularly reflected light as in the first embodiment. Needless to say.

The cooling controller 23 increases the current supplied to the Peltier element 10 when the intensity of the reflected light is below the threshold as a result of the comparison between the reflected light intensity by the reflected light intensity detector 22 and the threshold.
As a result, when the temperature of the elliptical spherical reflecting mirror 12 decreases, water vapor contained in the gas to be measured is condensed on the elliptical spherical reflecting mirror 12, and a part of the light emitted from the laser diode 1 is irregularly reflected. The intensity of the reflected light incident on 2a increases and becomes equal to or greater than the threshold value.

  The cooling control unit 23 reduces the current supplied to the Peltier element 10 when the intensity of the reflected light becomes equal to or greater than the threshold value. Thereby, the occurrence of condensation is suppressed, and the intensity of the reflected light incident on the photodiode 2a is reduced. When the intensity of the reflected light falls below the threshold value, the cooling control unit 23 increases the current supplied to the Peltier element 10. As described above, by repeatedly increasing and decreasing the current supplied to the Peltier element 10, the temperature of the cooling surface of the Peltier element 10 is adjusted so that the intensity of the reflected light incident on the photodiode 2 becomes substantially equal to the threshold value.

The dew point detection unit 24 uses the adjusted temperature, that is, the temperature measured by the temperature sensor 9 when the intensity of the reflected light is within a predetermined range centered on the threshold value, to cause the condensation on the elliptic spherical reflector 12 to occur. Is the temperature (dew point temperature) at which has reached an equilibrium state. The value of the dew point temperature is displayed on the display unit 25.
Thus, according to the present embodiment, the same effect as that of the first embodiment can be obtained in the mirror-cooled dew point meter of the scattered light detection method.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 4A is a side sectional view of an optical part of a mirror-cooled dew point meter according to the third embodiment of the present invention, and FIG. 4B is a sectional view taken along line AA in FIG. 4 (C) is a cross-sectional view taken along line BB in FIG. 4 (A), and the same components as those in FIGS. 1 (A) to 1 (C) are denoted by the same reference numerals. 4A to 4C, 30 and 31 are optical fibers, and 32 and 33 are holders. The optical fiber 30 and a laser diode (not shown) constitute a light projecting means, and the optical fiber 31 and a photodiode (not shown) constitute a light receiving means.

  In the mirror-cooled dew point meter of this embodiment, the light emitted from the laser diode is guided to the optical unit by the optical fiber 30 and the reflected light from the elliptic spherical reflector 12 is guided to the photodiode by the optical fiber 31. Yes. The optical fiber 30 is fixed to the upper surface member 4 by a holder 32, and the optical fiber 31 is fixed to the upper surface member 4 by a holder 33. At this time, the optical fiber 30 is fixed so that its exit surface is located at one focal point f1 of the elliptical spherical reflecting mirror 12, and the optical fiber 31 has its incident surface at the other focal point f2 of the elliptical spherical reflecting mirror 12. It is fixed to be positioned.

As in the first embodiment, the gas to be measured flows into the container from the vent hole 13, flows in the direction of the arrow 15 in FIG. 4A, and flows out of the container from the vent hole 14.
The light emitted from the laser diode is guided to the optical unit by the optical fiber 30, and the laser light emitted from the optical fiber 30 passes through the atmosphere of the gas to be measured in the container and is reflected by the elliptic spherical reflector 12. The light again passes through the measured gas atmosphere and enters the optical fiber 31. The optical fiber 31 guides the reflected light from the elliptic spherical reflector 12 to the photodiode.

The laser diode is connected to the laser driver 21 in FIG. 2, and the photodiode is connected to the reflected light intensity detector 22. The configuration and operation of the detection unit 20 are the same as those in the first embodiment. Thus, also in this embodiment, the same effect as that of the first embodiment can be obtained.
Needless to say, this embodiment may be applied to the second embodiment.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. FIG. 5 is a cross-sectional view of an optical part of a mirror-cooled dew point meter according to the fourth embodiment of the present invention. The same reference numerals are given to the same components as those in FIGS. 1 (A) to 1 (C). It is. In FIG. 5, 40 is an elliptic prism, and 42 and 43 are optical fibers. The optical fiber 42 and a laser diode (not shown) constitute a light projecting means, and the optical fiber 43 and a photodiode (not shown) constitute a light receiving means.

In the mirror-cooled dew point meter of the present embodiment, the elliptic prism 40 is arranged on the copper block 8 described in the first embodiment. The elliptic spherical inner wall surface of the elliptic prism 40 functions as the elliptic spherical reflector 41.
That is, the light emitted from the laser diode is guided to the optical unit by the optical fiber 42, the light is irradiated from the bottom surface of the elliptic prism 40, and the light totally reflected by the elliptic spherical reflector 41 is received by the optical fiber 43 to receive the photodiode. Lead to. The optical fiber 42 is fixed so that its exit surface is located at one focal point f1 of the elliptical spherical reflector 41, and the optical fiber 43 is such that its incident surface is located at the other focal point f2 of the elliptical spherical reflector 41. Fixed to.

The gas to be measured flows on the elliptic prism 40 in the direction of the arrow 15 in FIG. When the elliptic prism 40 is cooled by the Peltier element 10 and dew condensation occurs on the elliptic spherical outer surface of the elliptic prism 40, the intensity of the reflected light from the elliptic spherical reflector 41 decreases.
The laser diode is connected to the laser driver 21 in FIG. 2, and the photodiode is connected to the reflected light intensity detector 22. The configuration and operation of the detection unit 20 are the same as those in the first embodiment. Thus, also in this embodiment, the same effect as that of the first embodiment can be obtained.
Needless to say, the position of the incident surface of the optical fiber 43 may be shifted from the focal point f2 of the elliptical spherical reflector 41, and this embodiment may be applied to the scattered light detection method.

  Moreover, although the 1st-4th embodiment demonstrated the mirror surface cooling type dew point meter, it is also possible to apply this invention to a fog detection apparatus. In this case, the copper block 8, the temperature sensor 9, the Peltier element 10, and the heat sink 11 for heat dissipation are unnecessary, and the elliptical spherical reflectors 12 and 41 are formed on the target window glass or the like. In the case of the first to third embodiments, the air corresponding to the gas to be measured is, for example, the inside air, and the back surface of the elliptical spherical reflecting mirror 12 is exposed to the outside air. In the case of the fourth embodiment, the oval outer surface of the elliptic prism 40 is exposed to the outside air. In the case of the specular reflection light detection method, when the elliptical spherical reflectors 12 and 41 are clouded, the intensity of the reflected light incident on the photodiode 2 is reduced to be equal to or lower than the threshold value. Cloudiness of the mirrors 12 and 41 can be detected. In the case of the scattered light detection method, when the elliptical spherical reflecting mirrors 12 and 41 are clouded, the intensity of the reflected light incident on the photodiode 2a increases and exceeds the threshold value. Cloudiness of the reflecting mirrors 12 and 41 can be detected.

  In the first to fourth embodiments, a laser diode is used as a light source, but a normal LED can also be used.

  The present invention can be applied to a fog detection device and a mirror-cooled dew point meter.

It is sectional drawing of the optical part of the specular cooling type dew point meter which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the detection part of the specular cooling dew point meter which concerns on the 1st Embodiment of this invention. It is sectional drawing of the optical part of the mirror surface cooling-type dew point meter which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the optical part of the mirror surface cooling type dew point meter which concerns on the 3rd Embodiment of this invention. It is sectional drawing of the optical part of the mirror surface cooling type dew point meter which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the principal part of the conventional mirror surface cooling-type dew point meter which employ | adopted the regular reflection light detection system. It is sectional drawing which shows the principal part of the conventional mirror surface cooling type dew point meter which employ | adopted the scattered light detection system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laser diode, 2, 2a ... Photodiode, 3 ... Bottom member, 4 ... Top surface member, 5 ... Side member, 6, 7, 32, 33 ... Holder, 8 ... Copper block, 9 ... Temperature sensor, 10 ... Peltier Element, 11 ... Heat sink for heat dissipation, 12, 41 ... Elliptical spherical reflector, 13, 14 ... Vent, 20 ... Detector, 21 ... Laser driver, 22 ... Reflected light intensity detector, 23 ... Cooling controller, 24 ... Dew point detection unit, 25 ... display unit, 30, 31, 42, 43 ... optical fiber, 40 ... elliptical prism.

Claims (3)

An ellipsoidal reflecting mirror whose mirror surface or the back surface of this mirror surface is exposed to the gas to be measured;
A laser diode for irradiating the elliptical spherical reflector with light;
A photodiode that receives the reflected light from the elliptic spherical reflector and converts it into an electrical signal;
The laser diode is disposed such that its exit surface is located at one focal point of the elliptical spherical reflector ,
The fog detecting device , wherein the photodiode is disposed so that an incident surface thereof is positioned at the other focal point of the elliptical spherical reflecting mirror . The fog detection device according to claim 1,
A fog detecting device, wherein an elliptic spherical inner wall surface of the elliptic prism is the elliptic spherical reflector. The cloudiness detection device according to claim 1 or 2 ,
Cooling means for cooling the elliptical spherical reflector;
A temperature sensor for measuring the temperature of the elliptical spherical reflector;
Based on the intensity of the reflected light received by the photodiode, the condensation formed on the elliptical spherical reflector or the back surface thereof is detected, and the temperature measured by the temperature sensor when the condensation is detected is determined as the dew point of the gas to be measured. A mirror-cooled dew point meter, characterized by having a detecting means for temperature.

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