JP2014228281A - Fourier transform type spectrometer and method for calibrating fourier transform type spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Fourier transform type spectrometer and a calibration method therefor capable of executing white calibration and wavelength calibration with equal frequency to each other.SOLUTION: A Fourier transform type spectrometer Da comprises: a measurement beam light source 51 for radiating a measurement beam; a wavelength calibration beam light source 54 for radiating a wavelength calibration beam; Fourier transformation spectroscope units 10, 20a, 30 and 41 for finding the spectrum of prescribed light by using Fourier transformation on the basis of an interferogram obtained by having the prescribed light interfere; a white calibration unit 415 for calibrating the white color of the Fourier transformation spectroscope units by injecting, as the prescribed light, a reflected beam of the measurement beam by a white calibration plate CP into the Fourier transformation spectroscope units; and a wavelength calibration unit 416 for calibrating the wavelength of the Fourier transformation spectroscope units by injecting, as the prescribed light, a reflected beam of the wavelength calibration beam by the white calibration plate CP into the Fourier transformation spectroscope units. The white calibration unit 415 and the wavelength calibration unit 416 perform white calibration and wavelength calibration successively in time.

Description

  The present invention relates to a Fourier transform spectrometer and a calibration method thereof, and more particularly to a Fourier transform spectrometer capable of performing white calibration and wavelength calibration, and a calibration method of a Fourier transform spectrometer.

  A spectrometer is a device that measures a spectrum representing a component (light intensity) of each wavelength (each wave number) in predetermined light (measurement light) to be measured, and one of them is a Fourier transform type using Fourier transform. Spectrometers are known. This Fourier transform spectrometer is a measuring device that measures the interference light of a predetermined light with an interferometer and obtains the spectrum of the predetermined light by Fourier transforming the measurement result. In this Fourier transform type spectrometer, the output of the interferometer is a combined waveform in which light of a plurality of wavelengths included in the predetermined light is interfered at once by the interferometer, which is called an interferogram, and this interferogram Is subjected to Fourier transform to obtain a spectrum of the predetermined light. This interferogram has a profile that has one or a plurality of steep peaks in a predetermined range and a substantially zero level in the remaining range, and the center peak of the one or more steep peaks has a center burst. Called.

  In general, a spectrometer including such a Fourier transform spectrometer requires so-called white calibration and wavelength calibration in order to obtain a predetermined measurement accuracy.

  This white calibration calibrates the deviation related to brightness, that is, the scale of the vertical axis of the spectral characteristics, and associates the measurement result of the interference light with the spectral energy of the light source at the time of measurement (which wavelength of light is This is a process for pricing how much strength it is. For example, a so-called white calibration plate (standard white plate) that can reflect the wavelength in the measurement range with a high reflectance (about 90% to about 99%) is arranged and measured at the measurement position for placing the object to be measured. As a result, white calibration is performed.

  The wavelength calibration is to calibrate the deviation related to wavelength, that is, the scale of the horizontal axis of the spectral characteristics, and associates the measurement result of the interference light with the actual wavelength (which measurement data represents the data of which wavelength value). Is a process of pricing whether or not For example, in a Fourier transform spectrometer, wavelength calibration is performed by associating a spectrum number obtained by Fourier transform with a wave number. This wavelength calibration is performed, for example, by measuring a standard sample (reference light) having a known physical property of the wavelength with a spectrometer and comparing the measurement result with the known wavelength. Such a technique relating to wavelength calibration is disclosed in, for example, Patent Document 1 and Patent Document 2. In this Patent Document 1, the reference light for wavelength calibration is narrowed by combining a neodymium-doped yttrium aluminum garnet (Nd: YAG) crystal filter and a Fabry-Perot etalon filter that absorbs at the primary spectrum peak. Has been generated by. In Patent Document 2, two distinct absorption peaks in a standardized liquid consisting of water and propanol (3.83 w / w%) are used for wavelength calibration.

Japanese Patent No. 3547771 Japanese Patent No. 3694029

  By the way, the white calibration of the Fourier transform spectrometer is performed on the user side, but the wavelength calibration is usually performed on the manufacturer side, so the user sends the Fourier transform spectrometer to the manufacturer and sends it to the manufacturer. Requests wavelength calibration. For this reason, a relatively large number of white calibrations of the Fourier transform spectrometer are performed, and the accuracy of the vertical axis of the spectral characteristics is relatively maintained, while the wavelength calibration of the Fourier transform spectrometer is performed with a comparative frequency. Therefore, the accuracy of the horizontal axis of the spectral characteristics is relatively difficult to maintain compared to the case of the vertical axis.

  The present invention has been made in view of the above circumstances, and its object is to provide a Fourier transform spectrometer and a calibration method for a Fourier transform spectrometer that can perform white calibration and wavelength calibration at the same frequency. It is to be.

  As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below. That is, the Fourier transform spectrometer according to one aspect of the present invention causes predetermined light to interfere with a measurement light source that emits measurement light for measurement, a wavelength calibration light source that emits wavelength calibration light for wavelength calibration, and the like. A Fourier transform spectroscopic unit that obtains a spectrum of the predetermined light using Fourier transform based on an interferogram obtained by the method, and reflected white calibration light obtained by reflecting the measurement light with a white calibration plate as the predetermined light. A white calibration unit that white calibrates the Fourier transform spectroscopic unit by entering the Fourier transform spectroscopic unit, and a reflected wavelength calibration light obtained by reflecting the wavelength calibration light with a white calibration plate as the predetermined light to the Fourier transform spectroscopic unit. A wavelength calibration unit that calibrates the wavelength of the Fourier transform spectroscopic unit by being incident, and the white calibration unit and the wavelength calibration unit continue in time. And performing a white calibration and wavelength calibration Te.

  Since such a Fourier transform type spectrometer performs white calibration and wavelength calibration continuously in time, white calibration and wavelength calibration can be performed at the same frequency. In addition, since such a Fourier transform spectrometer performs wavelength calibration using a white calibration plate, even if wavelength calibration light does not enter the white calibration plate with a predetermined geometry, the reflected wavelength calibration light is converted into a Fourier transform spectrometer. And wavelength calibration can be performed. In such a Fourier transform spectrometer, a white calibration plate and a wavelength are arranged by placing a white calibration plate at a measurement position (sample placement position) for placing an object to be measured (measurement sample, specimen, object to be measured). Since calibration is performed, it is possible to calibrate almost all of the deviation factors. For this reason, such a Fourier transform type spectrometer can be calibrated with higher accuracy and can obtain a measurement result with higher accuracy.

  In another aspect, in the above-described Fourier transform spectrometer, the measurement light source and the wavelength calibration light source are respectively separate light sources.

  Such a Fourier transform type spectrometer has the measurement light source and the wavelength calibration light source as separate light sources, so that a light source suitable for measurement can be employed, and a light source suitable for wavelength calibration is employed. can do. For this reason, such a Fourier transform spectrometer can be measured with a desired measurement accuracy, and wavelength calibration can be performed with a desired calibration accuracy.

  In another aspect, in the above-described Fourier transform spectrometer, the wavelength calibration light source includes a xenon lamp and flat light emission control for causing the xenon lamp to emit light at a constant light intensity within a predetermined time after light emission. And a flat light emitting xenon lamp.

  Since such a Fourier transform type spectrometer uses a flat emission xenon lamp, the wavelength can be calibrated with a stable light intensity during wavelength calibration. For this reason, such a Fourier transform spectrometer can calibrate the wavelength more accurately.

  According to another aspect, in the above-described Fourier transform spectrometer, the wavelength calibration light source is one of a light emitting diode and a laser light source, and a temperature measurement unit that measures a temperature related to the light source. And a light emission wavelength control unit that causes the light source to emit light at a predetermined wavelength based on the temperature measured by the temperature measurement unit.

  In general, light emitting diodes and laser light sources have temperature dependence on the emission wavelength. Such a Fourier transform type spectrometer uses a light emitting diode or a laser light source that controls the temperature of the emission wavelength, so that the wavelength can be calibrated more accurately.

  According to another aspect, in the above-described Fourier transform spectrometer, the Fourier transform spectroscopic unit includes a plurality of optical elements that form two optical paths between an incident position of the predetermined light and an interference position. The plurality of optical elements includes an interferometer including an optical path difference forming optical element that generates an optical path difference between the two optical paths by moving in the optical axis direction, and light of the optical path difference forming optical element A position detection monochromatic light source that emits monochromatic light for position detection for detecting a position on the axis, and a signal obtained by photoelectrically converting the interference light of the monochromatic light generated by the interferometer is predetermined. A timing output unit that outputs a cross signal at a timing that intersects the reference value of the signal, and an I / F that is measured by sampling the interferogram of the predetermined light generated by the interferometer with the zero cross signal. A terferogram measurement unit, and a spectrum calculation unit that obtains a spectrum of the predetermined light using Fourier transform based on the interferogram measured by the interferogram measurement unit, wherein the wavelength calibration light source is the position It is also used as a detection monochromatic light source, and the wavelength calibration light is a part of the position detection monochromatic light.

  In such a Fourier transform spectrometer, the position detection monochromatic light of the position detection monochromatic light source of the Fourier transform spectroscopic unit is diverted to the wavelength calibration light, so that it is not necessary to separately provide a wavelength calibration light source.

  According to another aspect, in the above-described Fourier transform spectrometer, the wavelength conversion unit further converts the wavelength of a part of the position detection monochromatic light into a wavelength that can be measured by the interferogram measurement unit. The wavelength calibration light is wavelength-converted light obtained by wavelength-converting a part of the position detection monochromatic light by the wavelength converter.

  Such a Fourier transform type spectrometer includes a wavelength converter even when the interferogram measuring unit is difficult or unable to detect the wavelength of the position detection monochromatic light. Therefore, the position detection laser beam is used as the wavelength calibration light. Can be diverted.

  According to another aspect, in the above-described Fourier transform spectrometer, the wavelength calibration unit is configured to set a measurement wavelength range of the interferogram measurement unit so that the wavelength of a part of the position detection monochromatic light can be measured. It is characterized by enlarging by oversampling.

  Such a Fourier transform spectrometer expands the measurement wavelength range of the interferogram measurement unit by oversampling so that the wavelength of the position detection monochromatic light can be measured. Can be diverted.

  In another aspect, the above-described Fourier transform spectrometer further includes a bandpass filter having a known wavelength as a transmission center wavelength and a transmission wavelength band corresponding to a bright line, and the wavelength calibration light includes the measurement It is filtered light obtained by filtering light with the band-pass filter.

  Since such a Fourier transform spectrometer includes the bandpass filter that narrows the incident light, the measurement light can be used as the wavelength calibration light.

  According to another aspect, in the above-described Fourier transform spectrometer, a monochromator unit further comprising a diffraction grating and a slit member formed with a slit that transmits only light of a predetermined order diffracted by the diffraction grating. The wavelength calibration light is monochromatic light obtained by monochromatizing the measurement light with the monochromator unit.

  Since such a Fourier transform spectrometer includes the monochromator unit that converts incident light into single wavelength light, the measurement light can be used as the wavelength calibration light.

  According to another aspect of the present invention, there is provided a method for calibrating a Fourier transform spectrometer, wherein a Fourier transform is used to obtain a spectrum of the predetermined light based on an interferogram obtained by interfering with the predetermined light. A white calibration step for white calibration of the Fourier transform spectroscopic unit by causing reflected white calibration light, which is obtained by reflecting measurement light for measurement with a white calibration plate, as the predetermined light to the conversion spectroscopic unit, and a wavelength for wavelength calibration A wavelength calibration step for calibrating the wavelength of the Fourier transform spectroscopic unit by causing the reflected wavelength calibration light obtained by reflecting the calibration light on a white calibration plate to enter the Fourier transform spectroscopic unit as the predetermined light, and the white calibration step and The wavelength calibration process is performed continuously in time.

  In such a Fourier transform spectrometer calibration method, the white calibration step and the wavelength calibration step are performed in succession, so that the white calibration and the wavelength calibration can be performed at the same frequency. In addition, since the calibration method of such a Fourier transform spectrometer performs wavelength calibration using a white calibration plate, even if wavelength calibration light does not enter the white calibration plate with a predetermined geometry, the reflected wavelength calibration light is Fourier transformed. The light can be incident on the conversion spectroscopic unit and wavelength calibration can be performed. In such a Fourier transform spectrometer calibration method, a white calibration plate and a wavelength calibration are performed by placing a white calibration plate at a sample placement position where a measurement object (measurement sample) to be measured is placed. It can be calibrated including almost all factors. For this reason, such a calibration method of the Fourier transform spectrometer can be calibrated with higher accuracy, and a more accurate measurement result can be obtained.

  The Fourier transform spectrometer and the calibration method of the Fourier transform spectrometer according to the present invention can perform white calibration and wavelength calibration with the same frequency.

It is a block diagram which shows the structure of the Fourier-transform type spectrometer in embodiment. It is a figure for demonstrating the structure of the optical system in the Fourier-transform-type spectrometer of 1st Embodiment. As an example, it is a diagram showing an emission line spectrum of emission line light of xenon (Xe) in the Fourier transform spectrometer of the first embodiment. It is a flowchart which shows the operation | movement regarding the calibration in the Fourier-transform type spectrometer of 1st Embodiment. It is a figure for demonstrating the structure of the optical system in the Fourier-transform-type spectrometer of 2nd Embodiment. It is a flowchart which shows the operation | movement regarding the calibration in the Fourier-transform-type spectrometer of 2nd Embodiment. It is a figure for demonstrating the structure of the optical system in the Fourier-transform-type spectrometer of 3rd Embodiment. It is a figure for demonstrating the structure of the optical system in the Fourier-transform-type spectrometer of 4th Embodiment. It is a flowchart which shows the operation | movement regarding the calibration in the Fourier-transform-type spectrometer of 4th Embodiment.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably. Further, in this specification, when referring generically, it is indicated by a reference symbol without a suffix, and when referring to an individual configuration, it is indicated by a reference symbol with a suffix.

(First embodiment)
FIG. 1 is a block diagram illustrating a configuration of a Fourier transform spectrometer according to the embodiment. FIG. 2 is a diagram for explaining a configuration of an optical system in the Fourier transform spectrometer according to the first embodiment. FIG. 3 is a diagram illustrating an emission line spectrum of emission line light of xenon (Xe) in the Fourier transform spectrometer of the first embodiment as an example. The horizontal axis in FIG. 3 is the wave number shown in cm ⁻¹ , and the vertical axis is the relative intensity.

  The Fourier transform spectrometer (hereinafter abbreviated as “FT spectrometer” as appropriate) Da in the first embodiment is a device that measures a spectrum of predetermined light, and measures the predetermined light with an interferometer, This is a device for obtaining the spectrum of the predetermined light by Fourier transforming the measured interference light waveform (interferogram) of the predetermined light. In the FT spectrometer Da of this embodiment, in order to improve the SN ratio and obtain a measurement result with good accuracy in the measurement of the spectrum of the measurement target object (measurement sample, sample, object to be measured) SM. In addition, an integration interferogram (synthetic interferogram) obtained by integrating a plurality of interferograms of the predetermined light generated by the interferometer is applied to a conversion target to be Fourier-transformed to obtain a spectrum of the sample SM. Gram) is used. The FT spectrometer Da in the present embodiment has a white calibration function for performing the above-described so-called white calibration and a wavelength calibration function for performing the above-described so-called wavelength calibration.

  For example, as shown in FIGS. 1 and 2, the FT spectrometer Da in the first embodiment includes a measurement calibration optical system 50a for irradiating the sample SM with measurement light and wavelength calibration light, and a predetermined calibration system 50a. An interferometer 10 that receives light and emits the interference light of the predetermined light, and a waveform (in the interference light of the predetermined light by receiving and photoelectrically converting the interference light of the predetermined light obtained by the interferometer 10 ( A light receiving processing unit 20a that outputs an electrical signal (interferogram) electrical signal (an electrical signal representing a change in light intensity in the interference light of the predetermined light), a position detection processing unit 30 that detects the position of the movable mirror 13 in the interferometer 10, and A control calculation unit 41, an input unit 42, an output unit 43, an interface unit (hereinafter abbreviated as “IF unit”) 44, and the housing 1 are provided. In the case where the spectrum of the sample SM is measured, the predetermined light is reflected light (reflected measurement light) of measurement light reflected by the sample SM. On the other hand, when white calibration is performed, the measurement light is reflected light reflected from the white calibration plate (reflected white calibration light). When wavelength calibration is performed, the wavelength calibration light for wavelength calibration is white calibrated. This is reflected light (reflected wavelength calibration light) reflected by a plate. The measurement light is light used for measuring the spectrum of the sample SM, and is light having a continuous spectrum in a predetermined wavelength band set in advance. In the present embodiment, the measurement light is also used when white calibration is performed. The wavelength calibration light is light used for wavelength calibration of the Fourier transform spectrometer Da, and includes light of a known wavelength in advance.

  The housing 1 is a box that accommodates the measurement calibration optical system 50a, the interferometer 10, the light reception processing unit 20a, the position detection processing unit 30, the control calculation unit 41, the input unit 42, the output unit 43, and the IF unit 44. On one surface thereof, a sample stage 1b for mounting a sample SM and a later-described white calibration plate CP is formed. More specifically, the housing 1 is a box having a main surface including a horizontal horizontal plane and a frustum portion formed on a part of the horizontal plane so as to protrude outward. A sample table 1b is formed on the horizontal upper surface of the frustum portion, and a plurality of input switches such as a numeric keypad are disposed on the horizontal surface, and the display surface is externally arranged. An exposed output unit 43 is disposed. Further, an IF unit 44 is disposed on one side surface of the housing 1 so that the connector unit faces the outside. An incident opening 1a for allowing the predetermined light to enter is formed in the sample table 1b so as to penetrate therethrough. The FT spectrometer Da according to this embodiment is provided with a white calibration plate CP used for white calibration. As described above, the white calibration plate CP is a plate-like member having at least one main surface formed in white so that the wavelength in the measurable region can be reflected with a high reflectance (about 90% to about 99%). Also called a standard white plate. In the present embodiment, the white calibration plate CP is arranged and used on the sample stage 1b not only when performing white calibration but also when performing wavelength calibration.

  The measurement calibration optical system 50 irradiates the sample SM with the measurement light when measuring the sample SM, irradiates the measurement light with the white calibration plate CP when performing white calibration, and applies the wavelength calibration light when performing wavelength calibration. This is an optical system that irradiates the white calibration plate CP and guides the reflected light reflected by the sample SM or the white calibration plate CP to the interferometer 10 as the predetermined light. In the measurement of the sample SM, the reflected light is reflected measurement light by the sample SM, in the white calibration, is reflected white calibration light by the white calibration plate CP of the measurement light, and in the wavelength calibration, wavelength reflected light is reflected. This is the reflected wavelength calibration light by the white calibration plate CP.

  Such a measurement calibration optical system 50 includes, for example, as shown in FIG. 2, a measurement light source 51, a first transmission light shielding mechanism 52, an illumination optical system 53, a wavelength calibration light source 54, and a first guide. And an optical optical system 60.

  The measurement light source 51 is an apparatus that is connected to the control calculation unit 41 and emits the measurement light according to the control of the control calculation unit 41. For example, in this embodiment, a halogen light source using halogen (Halogen Lamp) or the like is used. is there.

  The first transmission / light shielding mechanism unit 52 is a device that is connected to the control calculation unit 41 and transmits or blocks the measurement light emitted from the measurement light source 51 according to the control of the control calculation unit 41. The first transmission light shielding mechanism 52 has a size capable of shielding the measurement light emitted from the measurement light source 51, and a fan-shaped plate-like light shielding plate capable of shielding the measurement light emitted from the measurement light source 51; And an actuator that rotates the light shielding plate at a predetermined angle about the fan-shaped center. The first transmission light shielding mechanism 52, when shielding the measurement light emitted from the measurement light source 51 under the control of the control calculation unit 41, transmits the measurement light from the measurement light source 51 to the incident aperture 1a. The light shielding plate is moved by the actuator to a light shielding position Pa that intersects the optical axis and shields the measurement light. On the other hand, the first transmission / shielding mechanism 52 does not shield the measurement light when transmitting the measurement light emitted from the measurement light source 51 according to the control of the control calculation unit 41 (the optical path of the measurement light is not changed). The light shielding plate is moved by the actuator to the retracted position Pb.

  The illumination optical system 53 is an optical system that guides the measurement light emitted from the measurement light source 51 to the incident aperture 1a with the predetermined geometry. For example, in this embodiment, the illumination optical system 53 enters the incident aperture 1a from the measurement light source 51. And a condensing lens disposed on the optical axis of the measurement light. In the example of the 45: 0 degree geometry, the illumination optical system 53 is configured such that the measurement light is incident on the opening surface of the incident opening 1a at an incident angle of 45 degrees.

  The wavelength calibration light source 54 is an apparatus that is connected to the control calculation unit 41 and emits the wavelength calibration light according to the control of the control calculation unit 41. As described above, in this embodiment, the measurement light source 51 and the wavelength calibration light source 54 are each constituted by individual light sources. The wavelength calibration light source 54 is disposed so that the emitted wavelength calibration light is incident on the incident aperture 1a with a predetermined geometry (for example, a 45: 0 degree geometry or the like). In the 45: 0 degree geometry example, the wavelength calibration light source 54 is arranged so that the wavelength calibration light is incident on the aperture surface of the entrance aperture 1a at an incident angle of 45 degrees.

  As the wavelength calibration light source 54 that emits wavelength calibration light, any type of light source can be used as long as it is a light source including at least one light having a known wavelength in advance.

  For example, the wavelength calibration light source 54 is a light source (emission line light source) that emits light including at least one emission line light having a known wavelength. Such bright line light sources include, for example, a xenon light source (Xe Lamp) using xenon (Xe), a krypton light source (Kr Lamp) using krypton (Kr), and a neon light source (Ne Lamp) using neon (Ne). ), An argon light source (Ar Lamp) using argon (Ar), a mercury light source (Hg Lamp) using mercury (Hg), and the like. As an example, the emission line spectrum of a xenon lamp is shown in FIG. The wavelength calibration light source 54 using a xenon lamp is preferably a flat light emission xenon lamp including a xenon lamp and a flat light emission control unit that causes the xenon lamp to emit light at a constant light intensity within a predetermined time after light emission. . Such a flat light emitting xenon lamp is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-120913. More specifically, the flat light emission xenon lamp includes a xenon lamp, a capacitor that stores electric energy, and an IGBT (Insulated Gate Bipolar Transistor) that controls on / off of electric energy supplied from the capacitor to the xenon lamp. And the flash emission is controlled by repeatedly turning on and off the IGBT so that the xenon lamp emits light with a uniform amount of light. By using this flat light emitting xenon lamp, the FT spectrometer Da can calibrate the wavelength with a stable light intensity during the wavelength calibration. For this reason, such an FT spectrometer Da can perform wavelength calibration more accurately.

  Further, for example, the wavelength calibration light source 54 is one of a light emitting diode that emits light including at least one light having a known wavelength and a laser light source (for example, a surface emitting laser having a wavelength of 1550 nm). It's okay. When a light emitting diode is used, a band pass filter having a transmission wavelength band corresponding to a bright line is further provided. The wavelength calibration light source 54 using a light emitting diode or a laser light source includes a light source of any one of the light emitting diode and the laser light source, a temperature measuring unit that measures a temperature related to the light source such as a thermistor, and the temperature. Preferably, the light source is a constant wavelength light source including a light emission wavelength control unit that emits light from the light source at a predetermined wavelength based on the temperature measured by the measurement unit. The light emission wavelength control unit adjusts the temperature of the light source by the temperature adjustment unit that adjusts the temperature of the light source, such as a Peltier element, and the temperature adjustment unit based on the temperature measured by the temperature measurement unit. And a temperature controller that causes the light source to emit light at a predetermined wavelength. In general, light emitting diodes and laser light sources have a temperature dependency on the emission wavelength. By using this constant wavelength light source, such an FT spectrometer Da can be calibrated with higher accuracy.

  The first light guide optical system 60 is an optical system that guides reflected measurement light to the interferometer 10 as predetermined light for reflected measurement light for measurement, reflected white calibration light for white calibration, and reflected wavelength calibration light for wavelength calibration. . For example, in the present embodiment, the first light guide optical system 60 is in the emission direction of the predetermined geometry (for example, the 0 ° direction (the normal direction of the opening surface of the incident aperture 1a) in the 45: 0 degree geometry). A condensing lens 61, an aperture plate 62, and a collimating lens 63 are provided in this order. The aperture plate 62 is a plate-like member in which a through-opening is formed, and is arranged so that the through-opening is located at each condensing position of the condensing lens 61 and the collimating lens 63. In the first light guide optical system 60 having this configuration, the predetermined light from the incident opening 1 a is collected by the condenser lens 61, enters the collimating lens 63 through the through-opening of the aperture plate 62, and is collimated by the collimating lens 63. It becomes parallel light and enters the interferometer 10.

  Returning to FIG. 1, the interferometer 10 includes a plurality of optical elements that receive predetermined light and form two optical paths between the incident position of the predetermined light and the interference position. Is an apparatus including an optical path difference forming optical element that generates an optical path difference between the two optical paths by moving in the optical axis direction. More specifically, the interferometer 10 receives predetermined light, branches the incident predetermined light into two first and second predetermined lights, and each of the branched first and second predetermined lights. Are propagated (propagated) to the first and second optical paths, which are two different paths, and merged again. From this branch point (branch position) to the merge point (merge position, interference position) If there is an optical path difference between the first optical path and the second optical path between the two, a phase difference is generated at the time of merging, so that light is shaded by the merging. As the interferometer 10, an interferometer having various types of first and second optical paths such as a Mach-Zehnder interferometer can be used. In this embodiment, as shown in FIG. It is constituted by.

  As shown in FIG. 2, an interferometer 10 of this Michelson interferometer is a semi-transparent mirror (half mirror) 11 fixedly arranged at a predetermined position as a plurality of optical elements, and fixedly arranged at a predetermined position. The fixed mirror 12 and the movable mirror 13 whose light reflecting surface moves in the optical axis direction, and the fixed mirror 12 and the movable mirror 13 are arranged so that the normals of the mirror surfaces are orthogonal to each other, The semi-transparent mirror 11 is arranged so that the normal line of the semi-transparent mirror surface passes through the orthogonal point of each normal line in the fixed mirror 12 and the movable mirror 13 and intersects each normal line at an angle of 45 degrees. In the interferometer 10, the predetermined light incident on the interferometer 10 is branched into two first and second predetermined lights by the semi-transparent mirror 11. One branched first predetermined light is reflected by the semi-transparent mirror 11 and enters the fixed mirror 12. The first predetermined light is reflected by the fixed mirror 12 and returns to the semi-transparent mirror 11 again following the optical path that has come. On the other hand, the other branched second predetermined light passes through the semi-transparent mirror 11 and enters the movable mirror 13. The second predetermined light is reflected by the movable mirror 13 and returns to the semi-transparent mirror 11 again following the optical path that has come. The first predetermined light reflected by the fixed mirror 12 and the second predetermined light reflected by the movable mirror 13 merge with each other and interfere with each other by the semi-transparent mirror 11. In the Michelson interferometer 10 having such a configuration, the predetermined light is incident on the interferometer 10 along the normal direction on the mirror surface of the movable mirror 13, and the interference light of the predetermined light is normal on the mirror surface of the fixed mirror 12. Ejected from the interferometer 10 along the direction.

  Therefore, in the present embodiment, the first predetermined light follows the first optical path from the incident position of the predetermined light to the semitransparent mirror 11 again through the semitransparent mirror 11 and the fixed mirror 12 in this order. The second predetermined light follows a second optical path from the incident position of the predetermined light to the semitransparent mirror 11 again through the semitransparent mirror 11 and the movable mirror 13 in this order. The interferometer 10 of the FT spectrometer Da generates the intensity of light due to the optical path difference generated by the moving mirror 13.

  For example, an optical element that generates an optical path difference between the two first and second optical paths by using resonance vibration is used for the movable mirror 13. Examples of such a movable mirror 13 include a light reflecting mechanism disclosed in Japanese Unexamined Patent Application Publication No. 2011-80854 and Japanese Unexamined Patent Application Publication No. 2012-42257. The light reflecting mechanism is disposed between the first and second leaf spring portions disposed opposite to each other and the first and second leaf spring portions spaced apart from each other. The first and second supports connected to the second leaf spring portion, and the second support relative to the first support in the opposing direction of the first and second leaf spring portions. And a drive unit that translates the body. In this light reflecting mechanism, in the movement direction of the second support, the thickness of the first and second supports is thicker than that of the first and second leaf springs. A reflection film is formed on one end surface of the support body 2 perpendicular to the moving direction, and the second support body is formed with the first and second leaf spring portions so that the reflection film is exposed. It is connected. Such a light reflection mechanism reciprocates the reflection film by resonance vibration, and is manufactured by, for example, a MEMS (Micro Electro Mechanical System) technique.

  The interferometer 10 includes a phase compensation plate arranged on the reflection side of the semi-transparent mirror 11 reflected by the semi-transparent mirror 11 when the predetermined light is branched into two first and second predetermined lights by the semi-transparent mirror 11. Furthermore, you may prepare. In this case, the first predetermined light reflected by the semi-transparent mirror 11 enters the fixed mirror 12 via the phase compensation plate, and the first predetermined light reflected by the fixed mirror 12 passes through the phase compensation plate. It enters the semi-transparent mirror 11 again. The phase compensator eliminates the phase difference between the first predetermined light and the second predetermined light resulting from the difference between the number of times the first predetermined light is transmitted through the semi-transparent mirror 11 and the number of times the second predetermined light is transmitted through the semi-transparent mirror 11. It compensates for the phase difference.

  Returning to FIG. 1, the light reception processing unit 20 a includes, for example, a first light reception unit 21, an amplification unit 22, and an analog-digital conversion unit (hereinafter referred to as “AD conversion unit”) 23. . As shown in FIG. 2, the first light receiving unit 21 receives and photoelectrically converts the interference light of the predetermined light obtained by the interferometer 10, thereby generating an electrical signal corresponding to the light intensity in the interference light of the predetermined light. It is a circuit to output. The FT spectrometer Da of the present embodiment is, for example, a specification for measuring near infrared light with a wavelength of 800 nm or more, more specifically, near infrared light with a wavelength of 1200 nm to 2500 nm. Therefore, the first light receiving unit 21 is, for example, an infrared sensor configured by including an InGaAs photodiode and its peripheral circuit. The amplifying unit 22 is an amplifier that amplifies the output of the first light receiving unit 21 with a predetermined amplification factor set in advance. The AD conversion unit 23 is a circuit that converts the output of the amplification unit 22 from an analog signal to a digital signal (AD conversion). The AD conversion timing (sampling timing) is executed at the zero cross timing input from the zero cross detector 35 described later.

  The position detection processing unit 30 includes, for example, a position detection monochromatic light source 31, a second light receiving unit 34, and a zero cross detection unit 35. Then, the position detection processing unit 30 obtains the interference light of the monochromatic laser light emitted from the position detection monochromatic light source 31 with the interferometer 10, as shown in FIG. 1 optical demultiplexer 33 is further provided.

  The position detection monochromatic light source 31 is a device that emits monochromatic light for position detection for detecting the position of the movable mirror 13 on the optical axis. For example, in this embodiment, a monochromatic (single wavelength) laser beam is used. It is a laser light source which radiates. In FIG. 2, an optical multiplexer 32 is an incident optical system for causing the laser light emitted from the position detection monochromatic light source 31 to enter the interferometer 10. The optical multiplexer 32 is, for example, a dichroic mirror or a semi-transparent mirror that reflects laser light and transmits predetermined light so that the normal line intersects the normal line (optical axis) of the movable mirror 13 at 45 degrees. , Between the entrance aperture 1a and the semi-transparent mirror 11. The position detection monochromatic light source 31 is arranged at an appropriate position so that the laser beam is incident on the optical multiplexer 32 arranged in this way at an incident angle of 45 degrees. The first optical demultiplexer 33 is an emission optical system for taking out the interference light of the laser light generated by the interferometer 10 from the interferometer 10. The first optical demultiplexer 33 is, for example, a dichroic mirror or a semi-transparent mirror that reflects the interference light of the laser light and transmits the interference light of the predetermined light, and the normal line thereof is the normal line (optical axis) of the fixed mirror 12. It arrange | positions between the semi-transparent mirror 11 and the 1st light-receiving part 21 so that it may cross at 45 degree | times. The second light receiving unit 34 is arranged at an appropriate position so as to receive the interference light of the laser beam emitted at an emission angle of 45 degrees with respect to the first optical demultiplexer 33 arranged in this way.

  When the optical elements of the optical multiplexer 32 and the first optical demultiplexer 33 are arranged in this way, the monochromatic laser light emitted from the position detection monochromatic light source 31 has an optical path in the dichroic of the optical multiplexer 32. It is bent by about 90 degrees by the mirror 32 and proceeds along the optical axis of the interferometer 10 (normal direction on the mirror surface of the movable mirror 13). Therefore, this laser light travels in the interferometer 10 in the same manner as the predetermined light, and the interferometer 10 generates the interference light. Then, the interference light of this laser light is bent by about 90 degrees by the dichroic mirror 33 of the first optical demultiplexer 33, taken out from the interferometer 10, and received by the second light receiving unit 34.

  Returning to FIG. 1, the second light receiving unit 34 receives the interference light of the laser light obtained by the interferometer 10 and photoelectrically converts it, thereby outputting an electrical signal corresponding to the light intensity of the interference light of the laser light. Circuit. The second light receiving unit 34 is, for example, a light receiving sensor configured by including a silicon photodiode (SPD) and its peripheral circuits. The second light receiving unit 34 outputs an electrical signal corresponding to the light intensity of the interference light of the laser light to the zero cross detection unit 35.

  The zero-cross detection unit 35 is a circuit that detects a timing (zero-cross timing) at which the electrical signal input from the second light-receiving unit 34 becomes zero (reference value) according to the light intensity of the interference light of the laser beam. Zero cross timing is a position on the time axis at which the electrical signal becomes zero. When the movable mirror 13 of the interferometer 10 is moved in the optical axis direction, the movable mirror 13 is moved from the semi-transparent mirror 11 to the phase of the laser light that has returned from the semi-transparent mirror 11 to the semi-transparent mirror 11 through the fixed mirror 12 again. Since the phase of the laser light that has returned to the semi-transparent mirror 11 again through the angle shifts, the interference light of the laser light becomes strong and weak in a sine wave shape according to the amount of movement. Then, when the movable mirror 13 of the interferometer 10 moves by a length that is ½ of the wavelength of the laser light, the phase of the laser light that has returned from the semi-transparent mirror 11 to the semi-transparent mirror 11 again through the movable mirror 13 is shifted by this movement. 2π before and after. For this reason, the interference light of the laser light repeats the intensity in a sine wave shape as the movable mirror 13 moves. The zero cross detector 35 detects the zero cross of the electric signal that repeats the strength in a sine wave form. The zero-cross detection unit 35 outputs the detected zero-cross timing to the AD conversion unit 23, and the AD conversion unit 23 receives the interference light of the predetermined light input from the first light receiving unit 21 at the zero-cross timing. The electrical signal corresponding to the intensity is sampled and AD converted.

  In this embodiment, such a zero-cross detection unit 35 compares, for example, a reference voltage generation circuit that generates a reference voltage with the output voltage of the second light receiving unit 34 and the reference voltage, and outputs the second light receiving unit 34. A comparator that outputs a square-wave comparison result signal when the signal is equal to or higher than the reference voltage, and a rising edge and a falling edge in the square-wave comparison result signal output from the comparator are detected. As an edge detection circuit for outputting a pulse signal to the AD converter 23.

  The control calculation unit 41 controls each part of the FT spectrometer Da according to the function of each part, obtains a spectrum of predetermined light, and performs white calibration and wavelength calibration. The control arithmetic unit 41 is, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory) or an EEPROM (Electrically Erasable Programmable Read Only) that stores various programs executed by the CPU and data necessary for the execution in advance. A non-volatile memory element such as Memory), a volatile memory element such as a RAM (Random Access Memory) serving as a so-called working memory of the CPU, and a microcomputer including peripheral circuits thereof. The control calculation unit 41 may further include a relatively large capacity storage device such as a hard disk, for example, in order to store data output from the AD conversion unit 23. Then, the control calculation unit 41 is functionally controlled by executing a program, such as a control unit 411, a sampling data storage unit 412, an interferogram extraction unit 413, a spectrum calculation unit 414, a white calibration unit 415, and a wavelength calibration unit. 416 and a calibration data storage unit 417 are configured.

  The control unit 411 controls each unit of the FT spectrometer Da according to the function of each unit in order to obtain a spectrum of predetermined light or perform each calibration.

  The sampling data storage unit 412 stores measurement data regarding the interference light of the predetermined light output from the AD conversion unit 23. As described above, the measurement data is obtained by sampling the electrical signal corresponding to the light intensity in the interference light of the predetermined light by the AD conversion unit 23 at the timing of the zero cross detected by the zero cross detection unit 35. More specifically, in the measurement of the sample SM, the sampling data storage unit 412 stores measurement data related to the interference light of the light in the sample SM output from the AD conversion unit 23. In the white calibration, the sampling data storage unit Reference numeral 412 stores measurement data related to the interference light of the reflected white calibration light from the white calibration plate CP, which is output from the AD conversion unit 23. In wavelength calibration, the sampling data storage unit 412 outputs from the AD conversion unit 23. The measured data relating to the interference light of the reflected wavelength calibration light by the white calibration plate CP is stored.

  The interferogram extraction unit 413 extracts data related to the interferogram of the predetermined light generated by the interferometer 10 from the measurement data stored in the sampling data storage unit 412. More specifically, in the measurement of the sample SM, the interferogram extraction unit 413 measures the light in the sample SM a plurality of times from the measurement data stored in the sampling data storage unit 412. A plurality of interferograms obtained by doing so are integrated while positioning, and an integrated interferogram is obtained, and the obtained integrated interferogram is notified to the spectrum calculation unit 414. The alignment is performed based on, for example, the position of the center burst of the interferogram or the position of the movable mirror 13. In the white calibration, the interferogram extraction unit 413 notifies the spectrum calculation unit 414 of the interferogram in the interference light of the reflected white calibration light from the measurement data stored in the sampling data storage unit 412. In the wavelength calibration, the interferogram extraction unit 413 notifies the spectrum calculation unit 414 of the interferogram in the interference light of the reflected wavelength calibration light from the measurement data stored in the sampling data storage unit 412.

  The spectrum calculation unit 414 obtains a spectrum of predetermined light by Fourier transforming the interferogram or the integrated interferogram notified from the interferogram extraction unit 413. More specifically, in the white calibration, the spectrum calculation unit 414 Fourier-transforms the interferogram of the interference light of the reflected white calibration light obtained by the interferogram extraction unit 413 in the measurement for white calibration. The Fourier transform result is notified to the white calibration unit 415. In the wavelength calibration, the spectrum calculation unit 414 Fourier-transforms the interferogram of the interference light of the reflected wavelength calibration light obtained by the interferogram extraction unit 413 in the measurement for wavelength calibration, and wavelength-calibrates this Fourier transform result. Notification to the unit 416. In the measurement of the sample SM, the spectrum calculation unit 414 calculates the sample SM based on the white calibration data and the wavelength calibration data obtained by the white calibration unit 415 and the wavelength calibration unit 416 and stored in the calibration data storage unit 417. The integrated interferogram of the sample SM obtained by the interferogram extraction unit 413 in the measurement is subjected to Fourier transform to obtain a light spectrum in the sample SM, and the obtained spectrum is output to the output unit 43.

  The white calibration unit 415 is based on the interferogram of the interference light of the white calibration light obtained by causing the reflected white calibration light, which is the measurement light reflected by the white calibration plate CP, to enter the interferometer 10 as predetermined light. The FT spectrometer Da is calibrated in white. More specifically, the white calibration unit 415 moves the light shielding plate of the first transmission light shielding mechanism unit 52 to the retracted position Pb and radiates the measurement light from the measurement light source 51, whereby the reflected white calibration light is predetermined. The light is incident on the interferometer 10 as light. Then, the white calibration unit 415 performs white calibration for white calibration based on the Fourier transform result obtained by Fourier transforming the interferogram of the interference light of the reflected white calibration light obtained by the interferometer 10. Obtain calibration data. As described above, the white calibration calibrates the deviation related to brightness, that is, the scale of the vertical axis of the spectral characteristics, and associates the measurement result of the interference light with the spectral energy of the light source at the time of measurement (which This is a process for pricing the intensity of light of a wavelength. In the present embodiment, for example, white calibration data is obtained by associating the Fourier transform result obtained from the reflected white calibration light with the reflectance of the white calibration plate. The white calibration unit 415 stores the obtained white calibration data in the calibration data storage unit 417 and causes the calibration data storage unit 417 to store the white calibration data.

  The wavelength calibration unit 416 is an interferogram of the interference light of the reflected wavelength calibration light obtained by causing the reflected wavelength calibration light obtained by reflecting the wavelength calibration light by the white calibration plate CP to enter the interferometer 10 as the predetermined light. The wavelength calibration of the FT spectrometer Da is performed based on the above. More specifically, the wavelength calibration unit 416 moves the light shielding plate of the first transmission light shielding mechanism unit 52 to the light shielding position Pa and emits wavelength calibration light from the wavelength calibration light source 54, thereby reflecting the wavelength calibration light. Is incident on the interferometer 10 as predetermined light. Then, the wavelength calibration unit 416 uses the Fourier transform result obtained by performing the Fourier transform on the interferogram of the interference light of the reflected wavelength calibration light, so that the peak corresponding to the light of the known wavelength included in the wavelength calibration light. A position is detected, and wavelength calibration data for wavelength calibration is obtained based on the detected peak position. As described above, the wavelength calibration is to calibrate the shift with respect to the wavelength, that is, the scale of the horizontal axis of the spectral characteristics, and associates the measurement result of the interference light with the actual wavelength (which measurement data has which wavelength value). Process for pricing whether the data is represented). For example, in the present embodiment, the wavelength calibration unit 416 obtains wavelength calibration data by associating the detected peak position with an actual wavelength value, that is, the known wavelength. The wavelength calibration unit 416 stores the obtained wavelength calibration data in the calibration data storage unit 417 and causes the calibration data storage unit 417 to store the wavelength calibration data.

  The white calibration unit 415 and the wavelength calibration unit 416 perform white calibration and wavelength calibration continuously in time. The term “continuous in time” means that white calibration or wavelength calibration is performed when measuring a normal sample SM, and immediately (continuously) when the measurement is completed or after performing a predetermined process excluding the measurement, the wavelength is continued. Calibration or white calibration is performed, and after these are completed, the measurement of the normal sample SM is performed. The white calibration and the wavelength calibration that are continuously performed in this time are performed, for example, immediately after the FT spectrometer Da is activated. In addition, for example, the white calibration and the wavelength calibration that are performed in succession over time are performed each time the number of measurements of the normal sample SM reaches a predetermined number of times set in advance. Further, for example, the white calibration and the wavelength calibration that are carried out in succession over time are performed every predetermined period or every time the total operating time of the FT spectrometer Da reaches a predetermined time. Is called. For example, when the white calibration unit 415 obtains white calibration data, the white calibration unit 415 notifies the wavelength calibration unit 416 to that effect, and upon receiving this notification, the wavelength calibration unit 416 starts wavelength calibration. Further, for example, when the white calibration unit 415 obtains the white calibration data, the white calibration unit 415 notifies the control unit 411 to that effect. Upon receiving this notification, the control unit 411 instructs the wavelength calibration unit 416 to start wavelength calibration, Upon receiving this instruction, the wavelength calibration unit 416 starts wavelength calibration. Accordingly, the white calibration unit 415 and the wavelength calibration unit 416 perform white calibration and wavelength calibration continuously in time.

  The calibration data storage unit 417 stores white calibration data and wavelength calibration data (calibration data) obtained by the white calibration unit 415 and the wavelength calibration unit 416, respectively.

  The input unit 42 is connected to the control calculation unit 41, for example, when inputting various commands such as a command for instructing calibration and a command for instructing the start of measurement of the sample SM, and for example, when inputting an identifier or Fourier transform in the sample SM. A device for inputting various data necessary for measuring a spectrum such as a selection input of a window function to be used to the FT spectrometer Da, such as a keyboard and a mouse. The output unit 43 is a device that is connected to the control calculation unit 41 and outputs commands and data input from the input unit 42 and a spectrum of predetermined light measured by the FT spectrometer Da, such as a CRT display, A display device such as an LCD and an organic EL display, or a printing device such as a printer.

  A touch panel may be configured by the input unit 42 and the output unit 43. In the case of configuring the touch panel, the input unit 42 is a position input device that detects and inputs an operation position such as a resistive film method or a capacitance method, and the output unit 4 is a display device. In this touch panel, a position input device is provided on the display surface of the display device, one or more input content candidates that can be input to the display device are displayed, and the user touches the display position where the input content to be input is displayed. The position is detected by the position input device, and the display content displayed at the detected position is input to the FT spectrometer Da as the operation input content of the user. In such a touch panel, since the user can easily understand the input operation intuitively, the FT spectrometer Da that is easy for the user to handle is provided.

  The IF unit 44 is a circuit that is connected to the control arithmetic unit 41 and inputs / outputs data to / from an external device. For example, an RS-232C interface circuit that is a serial communication method, a Bluetooth (registered trademark) standard. An interface circuit that performs infrared communication such as an IrDA (Infrared Data Association) standard, an interface circuit that uses a USB (Universal Serial Bus) standard, and the like.

  In the FT spectrometer Da according to this embodiment, the interferometer 10, the light reception processing unit 20a, the position detection processing unit 30, the sampling data storage unit 412 in the control calculation unit 41, and the interferogram extraction unit. 413 and the spectrum calculation unit 414 correspond to an example of a Fourier transform spectroscopic unit, and the sampling data storage unit 412 and the interferogram extraction unit 413 in the control calculation unit 41 correspond to an example of an interferogram measurement unit. The second light receiving unit 34 and the zero cross detection unit 35 correspond to an example of a timing output unit.

  Next, the operation of this embodiment will be described. First, an operation when measuring a normal sample SM will be described, and then an operation when performing white calibration and wavelength calibration will be described.

  In the FT spectrometer Da having the above configuration, when measuring the sample SM, first, the sample SM is arranged on the sample stage 1b so as to cover the incident aperture 1a, the sample SM is set on the FT spectrometer Da, and measurement is performed. Be started. The sample SM may be accommodated in the sample petri dish SS, and the sample petri dish SS may be arranged on the sample stage 1b so as to cover the incident opening 1a. When the measurement is started, according to the control of the control unit 411, the first transmission light shielding mechanism unit 52 retracts the light shielding plate to the retracted position Pb, and the measurement light source 51 emits measurement light. In the case of a 45: 0 degree geometry, the measurement light emitted from the measurement light source 51 is incident on the sample SM at an incident angle of 45 degrees, reflected by the sample SM, and reflected light of the reflected measurement light. Is measured from the 0 degree direction. That is, the component of the reflected light reflected in the normal direction (0 degree) on the aperture surface of the incident aperture 1 a is incident on the interferometer 10 as the predetermined light via the first light guide optical system 60.

  The predetermined light incident on the interferometer 10 is received by the first light receiving unit 21 of the light receiving processing unit 20a as interference light of the predetermined light by the interferometer 10. More specifically, the predetermined light is branched into first and second predetermined light by being reflected and transmitted by the semi-transparent mirror 11 via the optical multiplexer 32. The first predetermined light branched by being reflected by the semi-transparent mirror 11 is incident on and reflected by the fixed mirror 12, and returns to the semi-transparent mirror 11 by tracing back the optical path that has come. On the other hand, the second predetermined light branched by passing through the semi-transparent mirror 11 is incident on the movable mirror 13 and reflected, and then returns to the semi-transparent mirror 11 by tracing back the optical path that has come. The first predetermined light reflected by the fixed mirror 12 and the second predetermined light reflected by the movable mirror 13 merge with each other and interfere with each other by the semi-transparent mirror 11. The interference light of the predetermined light is emitted from the interferometer 10 to the first light receiving unit 21 via the first optical demultiplexer 33. The first light receiving unit 21 photoelectrically converts the incident interference light of the predetermined light and outputs an electrical signal corresponding to the light intensity in the interference light of the predetermined light to the amplification unit 22. The amplifying unit 22 amplifies the electric signal corresponding to the interference light of the predetermined light with a predetermined amplification factor, and outputs the amplified electric signal to the AD converting unit 23.

  On the other hand, the FT spectrometer Da also captures monochromatic laser light emitted from the position detection monochromatic light source 31. The laser light is incident on the interferometer 10 via the optical multiplexer 32, interferes with the interferometer 10 in the same manner as described above, and becomes the interference light of the laser light, and then passes through the first optical demultiplexer 33. Light is received by the light receiving unit 34. The second light receiving unit 34 photoelectrically converts the incident interference light of the laser beam and outputs an electrical signal corresponding to the light intensity in the interference light of the laser beam to the zero cross detection unit 35. The zero cross detector 35 detects, as a zero cross timing, a timing at which the electrical signal corresponding to the interference light of the laser beam crosses a predetermined reference value, for example, zero, and this zero cross timing (zero cross signal) is a sampling timing (AD conversion). Timing) to the AD converter 23.

  While such predetermined light and laser light are respectively taken into the interferometer 10, the movable mirror 13 of the interferometer 10 follows the optical axis direction according to control of the control unit 411 of the control calculation unit 41 by resonance vibration. Has been moved.

  The AD conversion unit 23 samples the electrical signal corresponding to the light intensity in the interference light of the predetermined light output from the amplification unit 22 at the zero cross timing input from the zero cross detection unit 35, and converts the analog signal into a digital signal. A / D conversion is performed, and the electric signal of the digital signal subjected to the A / D conversion is output to the control calculation unit 41.

  By operating in this way, measurement data in an interferogram of predetermined light is output from the AD conversion unit 23 to the control calculation unit 41, and this measurement data is stored in the sampling data storage unit 412. Then, in order to improve the S / N ratio and obtain a result with good accuracy, the interferogram of such a predetermined light is measured in a similar manner a plurality of times in accordance with the reciprocation of the movable mirror 13, and each of these Each measurement data of the interferogram is stored in the sampling data storage unit 412. When the movable mirror 13 reciprocates once, one interferogram measurement data is obtained for each of the forward path and the return path. That is, one interferogram is data from the maximum amplitude position at one end to the maximum amplitude position at the other end via the vibration center (optical path difference 0).

  Next, the interferogram extraction part 413 calculates | requires the integration interferogram with respect to predetermined light by integrating | accumulating, aligning several interferogram of the predetermined light obtained by measuring in multiple times.

  Next, the spectrum calculation unit 414 performs Fourier transform on the integrated interferogram obtained by the interferogram extraction unit 413.

The calculation of this spectrum will be described more specifically. First, the interferogram F _m (x _i ) in the m-th measurement has an optical path difference x _i , a wave number ν _j , and a wave number ν _j spectrum. When the amplitude is B (ν _j ), the position of the optical path difference 0 is X _0, and the phase at the position of the optical path difference 0 of the wave number ν _j is φ (ν _j ), it is expressed by Expression 1. Note that m represents the measurement result of the mth measurement.

Therefore, the integrated interferogram F (x _i ) is expressed by Equation 2.

  When the integrated interferogram is obtained by the interferogram extracting unit 413 in this way, the spectrum calculating unit 414 obtains a spectrum of predetermined light by performing, for example, fast Fourier transform (FFT) on the integrated interferogram.

More specifically, in the case of fast Fourier transform, in order to reduce the occurrence of side lobes, a window function A _window (x _i ) that is symmetric about the optical path difference 0 (center burst position) is multiplied. (Expression 3), fast Fourier transform is performed to obtain the amplitude | B _window (ν _j ) | of the spectrum of the predetermined light (Expression 4).

Examples of the window function A _window (x _i ) can include various appropriate functions. For example, the window function A _window (x _i ) is a function represented by Expression 5-1 to Expression 5-3. Equation 5-1 is called a Hanning Window function, Equation 5-2 is called a Hamming Window function, and Equation 5-3 is called a Blackman Window function. .

  Then, the spectrum calculation unit 414 obtains the spectrum of the predetermined light subjected to white calibration and wavelength calibration based on the white calibration data and wavelength calibration data stored in the calibration data storage unit 417, based on the Fourier transform result of the predetermined light. . When the spectrum is obtained, the control calculation unit 41 outputs the obtained spectrum to the output unit 43.

  The FT spectrometer Da in this embodiment can measure the spectrum of predetermined light by operating in this way.

  Next, white calibration and wavelength calibration will be described. FIG. 4 is a flowchart showing an operation related to calibration in the Fourier transform spectrometer of the first embodiment.

  In the FT spectrometer Da having the above configuration, when white calibration is performed, first, the white calibration plate CP is disposed on the sample stage 1b so as to cover the entrance opening 1a, and the white calibration plate CP is set on the FT spectrometer Da. (S11). Next, the white calibration unit 415 causes the first transmission light shielding mechanism unit 52 to retract the light shielding plate to the retracted position Pb via the control unit 411 and causes the measurement light source 51 to emit measurement light via the control unit 411. (S12).

  In the case of a 45: 0 degree geometry, the measurement light emitted from the measurement light source 51 is incident on the white calibration plate CP at an incident angle of 45 degrees, reflected by the white calibration plate CP, and this reflected measurement. The reflected light is measured from the 0 degree direction. That is, the component of the reflected light (reflected white calibration light) reflected in the normal direction (0 degree) on the aperture surface of the incident aperture 1 a is incident on the interferometer 10 as the predetermined light via the first light guide optical system 60. . The reflected white calibration light is incident on the interferometer 10 via the optical multiplexer 32, interferes with the interferometer 10 in the same manner as described above, and becomes the interference light of the reflected white calibration light and passes through the first optical demultiplexer 33. The first light receiving unit 21 receives the light. The interference light of the reflected white calibration light received by the first light receiving unit 21 is photoelectrically converted by the first light receiving unit 21, amplified by the amplification unit 22, and zero-crossing detection unit 35 by the AD conversion unit 23 as described above. Are sampled at zero cross timing and output to the control calculation unit 41. The measurement data in the interferogram of the interference light of the reflected white calibration light generated thereby is stored in the sampling data storage unit 412. The white calibration unit 415 causes the spectrum calculation unit 414 to notify the spectrum calculation unit 414 of the interferogram in the interference light of the reflected white calibration light from the measurement data stored in the sampling data storage unit 412 by the interferogram extraction unit 413. In 414, the interferogram in the interference light of the reflected white calibration light is Fourier transformed. Then, the white calibration unit 415 obtains white calibration data based on the obtained Fourier transform result. When the white calibration data is obtained, the white calibration unit 415 stores the obtained white calibration data in the calibration data storage unit 417 and notifies the wavelength calibration unit 416 of the end of the white calibration (S13).

  When the white calibration is completed, the wavelength calibration unit 416 subsequently performs wavelength calibration. In this wavelength calibration, the wavelength calibration unit 416 first places the light shielding plate on the first transmission light shielding mechanism unit 52 via the control unit 411 while the white calibration plate CP is set on the FT spectrometer Da. The measurement light from the measurement light source 51 is shielded (S14). Next, the wavelength calibration unit 416 causes the wavelength calibration light source 54 to emit wavelength calibration light via the control unit 411 (S15).

  In the case of a 45: 0 degree geometry, the wavelength calibration light emitted from the wavelength calibration light source 54 enters the white calibration plate CP at an incident angle of 45 degrees, and is reflected by the white calibration plate CP. The reflected light of the wavelength calibration light is measured from the 0 degree direction. That is, the component of the reflected light (reflected wavelength calibration light) reflected in the normal direction (0 degree) on the aperture surface of the incident aperture 1 a is incident on the interferometer 10 as the predetermined light via the first light guide optical system 60. . The reflected wavelength calibration light is incident on the interferometer 10 via the optical multiplexer 32, interferes with the interferometer 10 in the same manner as described above, and becomes the interference light of the reflected wavelength calibration light and passes through the first optical demultiplexer 33. The first light receiving unit 21 receives the light. The interference light of the reflected wavelength white calibration light received by the first light receiving unit 21 is photoelectrically converted by the first light receiving unit 21, amplified by the amplification unit 22, and zero cross detection unit by the AD conversion unit 23, as described above. It is sampled at 35 zero-cross timings and output to the control calculation unit 41. The measurement data in the interferogram of the interference light of the reflected wavelength calibration light generated thereby is stored in the sampling data storage unit 412. The wavelength calibration unit 416 notifies the spectrum calculation unit 414 of the interferogram in the interference light of the reflected wavelength calibration light from the measurement data stored in the sampling data storage unit 412 by the interferogram extraction unit 413, and the spectrum calculation unit In 414, the interferogram in the interference light of the reflected wavelength calibration light is Fourier transformed. Then, the wavelength calibration unit 416 searches for the peak position corresponding to the wavelength of light set in advance as the wavelength calibration price from the obtained Fourier transform result, and the actual wavelength is found at the searched peak position. Wavelength calibration data is obtained by associating a value, that is, the known wavelength. When the wavelength calibration data is obtained, the wavelength calibration unit 416 stores the obtained wavelength calibration data in the calibration data storage unit 417 (S16).

  As described above, the FT spectrometer Da according to this embodiment performs white calibration and wavelength calibration continuously in time, so that white calibration and wavelength calibration can be performed at the same frequency. In addition, since the FT spectrometer Da performs wavelength calibration as well as white calibration using the white calibration plate CP, even if the wavelength calibration light does not enter the white calibration plate CP with a predetermined geometry, the reflected wavelength calibration light is used. Can be incident on the interferometer 10 and wavelength calibration can be performed. The FT spectrometer Da performs white calibration and wavelength calibration by placing the white calibration plate CP on the sample stage 1b, which is the measurement position for placing the sample SM. it can. For this reason, this FT type | mold spectrometer Da can be calibrated more highly accurately and can obtain a more highly accurate measurement result.

  In addition, since the FT spectrometer Da in the present embodiment includes the measurement light source 51 and the wavelength calibration light source 54 as separate light sources, as described above, a light source suitable for measurement can be employed. A light source suitable for wavelength calibration can be employed. For this reason, the FT spectrometer Da can measure with a desired measurement accuracy, and can perform wavelength calibration with a desired calibration accuracy.

  Next, another embodiment will be described.

(Second Embodiment)
FIG. 5 is a diagram for explaining a configuration of an optical system in a Fourier transform spectrometer according to the second embodiment. FIG. 6 is a flowchart showing an operation relating to calibration in the Fourier transform spectrometer of the second embodiment.

  Although the FT spectrometer Da in the first embodiment includes the measurement light source 51 and the wavelength calibration light source 54 as separate light sources, the FT spectrometer Db in the second embodiment has the wavelength calibration light source 54. Is also used as the position detection monochromatic light source 31 and a part of the position detection laser light emitted from the position detection monochromatic light source 31 is used as the wavelength calibration light.

  Such an FT spectrometer Db in the second embodiment includes, for example, a measurement calibration optical system 50b, an interferometer 10, a light reception processing unit 20b, a position detection processing unit 30, a control calculation unit 41, and an input unit. 42, an output unit 43, an IF unit 44, and the housing 1. The interferometer 10, the position detection processing unit 30, the control calculation unit 41, the input unit 42, the output unit 43, the IF unit 44, and the housing 1 in the FT spectrometer Db of the second embodiment are respectively the first embodiment. Since this is the same as the interferometer 10, the position detection processing unit 30, the control calculation unit 41, the input unit 42, the output unit 43, the IF unit 44, and the housing 1 in the FT spectrometer Da, the description thereof is omitted. Note that the optical multiplexer 32 in the position detection processing unit 30 of the second embodiment transmits not only predetermined light but also position detection laser light used as wavelength calibration light. In FIG. 5, the optical axes are shifted so that the laser light used for position detection and the laser light used as wavelength calibration light are not mixed. Thus, the laser light and the wavelength calibration light are prevented from entering the same light receiving unit. Further, the wavelength of the laser light emitted from the position detection monochromatic light source 31 is assumed to be known in the present embodiment.

  The measurement calibration optical system 50b uses the wavelength calibration light source also as the position detection monochromatic light source 31 and uses a part of the position detection laser light emitted from the position detection monochromatic light source 31 as the wavelength calibration light. When measuring the sample SM, the measurement light is irradiated to the sample SM. When white calibration is performed, the measurement light is irradiated to the white calibration plate CP. When wavelength calibration is performed, the wavelength calibration light is white calibrated. An optical system that irradiates the plate CP and guides the reflected light reflected by the sample SM or the white calibration plate CP to the interferometer 10 as the predetermined light.

  More specifically, as shown in FIG. 5, the measurement calibration optical system 50b includes a measurement light source 51, an illumination optical system 53, a first light guide optical system 60, and a second light guide optical system 70a. Prepare. The measurement light source 51, the illumination optical system 53, and the first light guide optical system 60 in the measurement calibration optical system 50b of the second embodiment are respectively the measurement light source 51 and the illumination in the measurement calibration optical system 50a of the first embodiment. Since it is the same as that of the optical system 53 and the 1st light guide optical system 60, the description is abbreviate | omitted.

  The second light guide optical system 70a is an optical system that guides part of the position detection laser light emitted from the position detection monochromatic light source 31 to the incident aperture 1a. For example, as shown in FIG. As described above, the second optical demultiplexer 71, the second transmission light shielding mechanism 72, and the reflecting mirror 73 are provided.

  The second optical demultiplexer 71 is an emission optical system for taking out a part of the laser beam emitted from the position detection monochromatic light source 31 from the position detection processing unit 30. The second optical demultiplexer 71 is, for example, a semi-transparent mirror that reflects part of the laser light and transmits the remaining laser light, and its normal is 45 degrees with respect to the optical axis of the position detection monochromatic light source 31. It arrange | positions between the position detection monochromatic light source 31 and the semi-transparent mirror 11 so that it may cross | intersect. A part of the laser light emitted at an emission angle of 45 degrees with respect to the second optical demultiplexer 71 arranged in this way is given a predetermined geometry (for example, 45: The reflecting mirror 73 is arranged at an appropriate angle and position so as to guide light with a 0 degree geometry or the like. Between the second optical demultiplexer 71 and the reflecting mirror 73, a second transmission light shielding mechanism 72 is arranged to transmit or shield part of the laser light at a timing as necessary. . The second transmissive light shielding mechanism 72 is configured in the same manner as the first transmissive light shielding mechanism 52. The second transmission light shielding mechanism 72 does not shield part of the laser light so as to transmit part of the laser light when wavelength calibration is performed according to the control of the control calculation unit 41 (see above). When the light shielding plate is moved to the retracted position Pd by the actuator and wavelength calibration is not performed, the light shielding plate is shielded at the light shielding position Pc for shielding a part of the laser light. Is moved by the actuator.

  Similarly to the light receiving processor 20a, the light receiving processor 20b receives the interference light of the predetermined light obtained by the interferometer 10 and photoelectrically converts it to output an electrical signal having a waveform in the interference light of the predetermined light. In addition, when wavelength calibration is performed, the wavelength calibration unit 416 expands the measurement wavelength range by oversampling so that the wavelength of a part of the laser beam can be measured. More specifically, the light reception processing unit 20b includes a first light reception unit 21, an amplification unit 22, and an AD conversion unit 23, as with the light reception processing unit 20a, and the AD conversion unit of the light reception processing unit 20b. 23 samples not only at the zero-cross timing of the zero-cross detector 35 but also at more timing (oversampling). From the sampling theorem, if the AD converter 23 samples only at the zero-cross timing of the position detection laser beam, a short wavelength equal to or less than the wavelength of the position detection laser beam cannot be detected. Not only sampling at the timing but also sampling at a larger number of timings makes it possible to detect a short wavelength shorter than the wavelength of the position detecting laser beam.

  The calibration operation of the FT spectrometer Db in the second embodiment will be described below. In FIG. 6, when white calibration is performed, first, the white calibration plate CP is set on the FT spectrometer Da similarly to the above-described processing S11 (S21). Next, the white calibration unit 415 causes the second transmissive light shielding mechanism unit 72 to move the light shielding plate to the light shielding position Pc via the control unit 411 and causes the measurement light source 51 to emit measurement light via the control unit 411. (S22). Thus, similarly to the first embodiment, the interference light of the reflected white calibration light is generated by the interferometer 10 from the reflected light from the white calibration plate CP in the measurement light of the measurement light source 51, and the measurement data in the interferogram is obtained. Obtained by the light reception processing unit 20b and stored in the sampling data storage unit 412. Then, the white calibration unit 415 uses the interferogram extraction unit 413 and the spectrum calculation unit 414 to Fourier-transform the interferogram in the interference light of the reflected white calibration light stored in the sampling data storage unit 412 and obtain this The white calibration data is obtained based on the Fourier transform result. When the white calibration data is obtained, the white calibration unit 415 stores the obtained white calibration data in the calibration data storage unit 417 and notifies the wavelength calibration unit 416 of the end of the white calibration (S23).

  When the white calibration is completed, the wavelength calibration unit 416 subsequently performs wavelength calibration. In this wavelength calibration, the wavelength calibration unit 416 first places the light shielding plate in the second transmission light shielding mechanism 72 via the control unit 411 while the white calibration plate CP is set on the FT spectrometer Da. And a part of the position detection laser light is made incident on the white calibration plate CP as wavelength calibration light (S24). That is, as the light shielding plate of the second transmission light shielding mechanism 72 moves to the retracted position Pd, a part of the position detection laser light branched by the second optical demultiplexer 71 is second transmitted light shielded. The light passes through the mechanism 72, is reflected by the reflecting mirror 73, and enters the white calibration plate CP. As a result, as in the first embodiment, interference light of reflected wavelength calibration light is generated by the interferometer 10 from reflected light from the white calibration plate CP in part of the laser light for position detection, and its interferogram. Is obtained by the light receiving processing unit 20b and stored in the sampling data storage unit 412. Here, the wavelength calibration unit 416 oversamples the AD conversion unit 23 as described above. Then, the wavelength calibration unit 416 uses the interferogram extraction unit 413 and the spectrum calculation unit 414 to Fourier-transform the interferogram in the interference light of the reflected wavelength calibration light stored in the sampling data storage unit 412 and obtain this From the Fourier transform result, a peak position corresponding to the wavelength of the laser beam for position detection set in advance as a wavelength calibration price is searched, and an actual wavelength value, that is, the known wavelength is calculated at the searched peak position. Wavelength calibration data is obtained by associating the wavelength of the laser beam. When the wavelength calibration data is obtained, the wavelength calibration unit 416 stores the obtained wavelength calibration data in the calibration data storage unit 417 (S16).

  In the case of measuring the sample SM, the light shielding plate of the second transmission light shielding mechanism 72 is moved to the light shielding position Pc according to the control of the control calculator 41, and the measurement light source 51 emits the measurement light. Then, the spectrum of the sample SM is measured by operating in the same manner as in the first embodiment.

  As described above, the FT spectrometer Db according to the present embodiment has the same effects as the FT spectrometer Da according to the first embodiment. Further, the measurement wavelength range is determined by oversampling, and the laser of the position detection monochromatic light source 31 is used. Since the wavelength of light is expanded so as to be measurable, the laser light of the position detection monochromatic light source 31 can be used for wavelength calibration light. The FT spectrometer Db diverts the laser light of the position detection monochromatic light source 31 to the wavelength calibration light, so that it is not necessary to separately provide a wavelength calibration light source.

  Next, another embodiment will be described.

(Third embodiment)
FIG. 7 is a diagram for explaining a configuration of an optical system in a Fourier transform spectrometer according to the third embodiment.

  The FT spectrometer Db in the second embodiment is configured to be able to detect the wavelength of the laser light of the position detection monochromatic light source 31 by oversampling of the AD conversion unit 23, and a part of the laser light of the position detection monochromatic light source 31. However, the FT spectrometer Dc according to the third embodiment converts the laser light of the position detection monochromatic light source 31 to a wavelength by converting the wavelength of the laser light of the position detection monochromatic light source 31. Are detected, and a part of the laser light of the position detection monochromatic light source 31 is used as wavelength calibration light.

  Such an FT spectrometer Dc in the third embodiment includes, for example, a measurement calibration optical system 50c, an interferometer 10, a light reception processing unit 20a, a position detection processing unit 30, a control calculation unit 41, and an input unit. 42, an output unit 43, an IF unit 44, and the housing 1. The interferometer 10, the light reception processing unit 20a, the position detection processing unit 30, the control calculation unit 41, the input unit 42, the output unit 43, the IF unit 44, and the housing 1 in the FT spectrometer Dc of the third embodiment are respectively The same as the interferometer 10, the light reception processing unit 20 a, the position detection processing unit 30, the control calculation unit 41, the input unit 42, the output unit 43, the IF unit 44 and the housing 1 in the FT spectrometer Da of the first embodiment. Since there is, explanation is omitted. In FIG. 7, the optical multiplexer 32 is the first FT spectrometer Dc in the third embodiment so that the laser light used for position detection and the laser light used as wavelength calibration light are not mixed. Although it is arranged at the same position as the FT spectrometer Da in the embodiment, as described later, a part of the position detection laser light is wavelength-converted into wavelength calibration light, so that the two laser lights are Even if they are on the same optical axis, they can be separated by setting the reflection wavelength region of the optical multiplexer 32.

  The measurement / calibration optical system 50c uses the wavelength calibration light source also as the position detection monochromatic light source 31 and converts the wavelength of part of the position detection laser light emitted from the position detection monochromatic light source 31 after wavelength conversion. It is configured to be used as light. When measuring the sample SM, the sample SM is irradiated with the measurement light. When white calibration is performed, the measurement light is irradiated onto the white calibration plate CP. When wavelength calibration is performed, the wavelength calibration is performed. This is an optical system that irradiates the white calibration plate CP with light and guides the reflected light reflected by the sample SM or the white calibration plate CP to the interferometer 10 as the predetermined light.

  More specifically, as shown in FIG. 7, the measurement calibration optical system 50c includes a measurement light source 51, an illumination optical system 53, a first light guide optical system 60, and a third light guide optical system 70b. Prepare. The measurement light source 51, the illumination optical system 53, and the first light guide optical system 60 in the measurement calibration optical system 50c of the third embodiment are respectively the measurement light source 51 and the illumination in the measurement calibration optical system 50a of the first embodiment. Since it is the same as that of the optical system 53 and the 1st light guide optical system 60, the description is abbreviate | omitted.

  The third light guide optical system 70b is an optical system that guides the light of the position detection laser light emitted from the position detection monochromatic light source 31 to the incident aperture 1a after wavelength conversion to a long wavelength. For example, as shown in FIG. 7, a second optical demultiplexer 71, a long wavelength conversion unit 74, a second transmission light shielding mechanism unit 72, and a reflecting mirror 73 are provided. The second optical demultiplexer 71, the second transmission light shielding mechanism 72, and the reflecting mirror 73 in the third light guide optical system 70b are respectively the second light guide optical system 70a in the FT spectrometer Db of the second embodiment. Since this is the same, the description thereof is omitted.

The long wavelength conversion unit 74 is arranged on the optical path from the second optical demultiplexer 71 to the incident aperture 1a, and converts part of the light in the position detection laser light emitted from the position detection monochromatic light source 31 into a long wavelength. Wavelength conversion to wavelength. The wavelength after wavelength conversion to the long wavelength is assumed to be known. Such a long wavelength conversion unit 74 includes a nonlinear optical crystal. Nonlinear optical crystals include, for example, BBO crystals (β-BaB ₂ O ₄ crystals), LBO crystals (LiB ₃ O ₅ crystals), KTP crystals (KTiOPO ₄ crystals), LiNbO ₃ crystals, MgO: LiNbO ₃ crystals, and AgGaS ₂ crystals. Etc. A part of the position detection laser beam branched by the second optical demultiplexer 71 is incident on the long wavelength conversion unit 74, and is converted into a known wavelength by the long wavelength conversion unit 74, and is stored in the retracted position Pd. The second transmission light shielding mechanism 72 is transmitted, reflected by the reflecting mirror 73, and incident on the white calibration plate CP.

  Since the configuration operation of the FT spectrometer Dc in the third embodiment is the same as the configuration operation of the FT spectrometer Db in the second embodiment except that oversampling is not performed, the description thereof is omitted.

  The FT spectrometer Dc according to the third embodiment has the same effects as the FT spectrometer Da according to the first embodiment, and further includes the long wavelength conversion unit 74. Therefore, the position detection monochromatic light source 31 is provided. Can be used as wavelength calibration light. The FT spectrometer Dc diverts the laser light from the position detection monochromatic light source 31 to the wavelength calibration light, so that it is not necessary to separately provide a wavelength calibration light source.

  Next, another embodiment will be described.

(Fourth embodiment)
FIG. 8 is a diagram for explaining a configuration of an optical system in a Fourier transform spectrometer according to the fourth embodiment. FIG. 9 is a flowchart showing an operation related to calibration in the Fourier transform spectrometer of the fourth embodiment.

  The FT spectrometers Db and Dc in the second and third embodiments use the laser light of the position detection monochromatic light source 31 as wavelength calibration light, but the FT spectrometer Dd in the fourth embodiment The measurement light from the measurement light source 51 is narrowed to a known wavelength and used as wavelength calibration light.

  Such an FT spectrometer Dd in the fourth embodiment includes, for example, a measurement calibration optical system 50d, an interferometer 10, a light reception processing unit 20a, a position detection processing unit 30, a control calculation unit 41, and an input unit. 42, an output unit 43, an IF unit 44, and the housing 1. The interferometer 10, the light reception processing unit 20a, the position detection processing unit 30, the control calculation unit 41, the input unit 42, the output unit 43, the IF unit 44, and the housing 1 in the FT spectrometer Dd of the fourth embodiment are respectively The same as the interferometer 10, the light reception processing unit 20 a, the position detection processing unit 30, the control calculation unit 41, the input unit 42, the output unit 43, the IF unit 44 and the housing 1 in the FT spectrometer Da of the first embodiment. Since there is, explanation is omitted.

  The measurement calibration optical system 50d is configured so that the wavelength calibration light source is also used as the measurement light source 51, and the measurement light emitted from the measurement light source 51 is narrowed and used as wavelength calibration light. When measuring, the measurement light is irradiated to the sample SM. When white calibration is performed, the measurement light is irradiated to the white calibration plate CP. When wavelength calibration is performed, the wavelength calibration light of the narrowed measurement light is converted into the white calibration plate CP. Is an optical system that guides the reflected light reflected by the sample SM or the white calibration plate CP to the interferometer 10 as the predetermined light.

  More specifically, as shown in FIG. 8, the measurement calibration optical system 50 dc includes a measurement light source 51, an illumination optical system 53, an optical filter insertion / extraction mechanism 81, and a first light guide optical system 60. . The measurement light source 51, the illumination optical system 53, and the first light guide optical system 60 in the measurement calibration optical system 50d of the fourth embodiment are respectively the measurement light source 51 and the illumination in the measurement calibration optical system 50a of the first embodiment. Since it is the same as that of the optical system 53 and the 1st light guide optical system 60, the description is abbreviate | omitted.

  The optical filter insertion / extraction mechanism 81 is a device that is connected to the control calculator 41 and transmits or narrows the measurement light emitted from the measurement light source 51 in accordance with the control of the control calculator 41. The optical filter insertion / extraction mechanism 81 has a size capable of shielding the measurement light emitted from the measurement light source 51, and a fan-shaped plate-like light shielding plate capable of shielding the measurement light emitted from the measurement light source 51; An optical filter fitted in a through opening formed at a predetermined position in the radial direction of the plate, and an actuator for rotating the light shielding plate at a predetermined angle about the fan-shaped center. The optical filter is a band-pass filter having a known wavelength as a transmission center wavelength and a transmission wavelength band corresponding to a bright line. When the optical filter insertion / extraction mechanism 81 narrows the measurement light emitted from the measurement light source 51 according to the control of the control calculation unit 41, the measurement light from the measurement light source 51 to the incident aperture 1a is measured. The light shielding plate is moved by the actuator to a band narrowing position Pe where the optical axis of the optical filter intersects the optical filter. As a result, the measurement light from the measurement light source 51 is filtered by the optical filter and narrowed, and then enters the incident aperture 1a as wavelength calibration light. On the other hand, the optical filter insertion / extraction mechanism 81 does not block the measurement light when transmitting the measurement light emitted from the measurement light source 51 under the control of the control calculation unit 41 (obstructs the optical path of the measurement light). No) The light shielding plate is moved to the retracted position Pf by the actuator.

  The calibration operation of the FT spectrometer Dd in the fourth embodiment will be described below. In FIG. 9, when white calibration is performed, first, the white calibration plate CP is set on the FT spectrometer Da similarly to the above-described processing S11 (S31). Next, the white calibration unit 415 causes the optical filter insertion / extraction mechanism unit 81 to move the light shielding plate to the retracted position Pf via the control unit 411 and causes the measurement light source 51 to emit measurement light via the control unit 411 ( S32). Thus, similarly to the first embodiment, the interference light of the reflected white calibration light is generated by the interferometer 10 from the reflected light from the white calibration plate CP in the measurement light of the measurement light source 51, and the measurement data in the interferogram is obtained. Obtained by the light reception processing unit 20 a and stored in the sampling data storage unit 412. Then, the white calibration unit 415 uses the interferogram extraction unit 413 and the spectrum calculation unit 414 to Fourier-transform the interferogram in the interference light of the reflected white calibration light stored in the sampling data storage unit 412 and obtain this The white calibration data is obtained based on the Fourier transform result. When the white calibration data is obtained, the white calibration unit 415 stores the obtained white calibration data in the calibration data storage unit 417 and notifies the wavelength calibration unit 416 of the end of the white calibration (S33).

  When the white calibration is completed, the wavelength calibration unit 416 subsequently performs wavelength calibration. In this wavelength calibration, the wavelength calibration unit 416 first places the light-shielding plate on the optical filter insertion / extraction mechanism unit 81 via the control unit 411 while the white calibration plate CP is set on the FT spectrometer Da. The measurement light that has been moved to Pe and narrowed by the optical filter is made incident on the white calibration plate CP as wavelength calibration light (S34). That is, when the light shielding plate of the optical filter insertion / extraction mechanism 81 is moved to the narrow band position Pe, the measurement light of the measurement light source 51 is filtered by the optical filter, narrowed and incident on the white calibration plate CP. . As in the first embodiment, the interference light of the reflected wavelength calibration light is generated by the interferometer 10 from the reflected light from the white calibration plate CP in the narrowed measurement light, and the measurement data in the interferogram is received. Obtained by the processing unit 20 a and stored in the sampling data storage unit 412. Then, the wavelength calibration unit 416 uses the interferogram extraction unit 413 and the spectrum calculation unit 414 to Fourier-transform the interferogram in the interference light of the reflected wavelength calibration light stored in the sampling data storage unit 412 and obtain this From the Fourier transform result, a peak position corresponding to the transmission center wavelength of the optical filter set in advance as a wavelength calibration price is searched, and an actual wavelength value, that is, the known optical value is detected at the searched peak position. Wavelength calibration data is obtained by associating the transmission center wavelength of the filter. When the wavelength calibration data is obtained, the wavelength calibration unit 416 stores the obtained wavelength calibration data in the calibration data storage unit 417 (S36).

  When measuring the sample SM, the light shielding plate of the optical filter insertion / extraction mechanism 81 is moved to the retracted position Pf under the control of the control calculation unit 41, and the measurement light is emitted from the measurement light source 51. Then, the spectrum of the sample SM is measured by operating in the same manner as in the first embodiment.

  The FT spectrometer Dd according to the fourth embodiment has the same effects as the FT spectrometer Da according to the first embodiment, and further includes the optical filter insertion / extraction mechanism 81. Measurement light can be used as wavelength calibration light. Since the FT spectrometer Dd diverts the measurement light from the measurement light source 51 to wavelength calibration light, it is not necessary to provide a separate wavelength calibration light source.

  In the fourth embodiment described above, in order to use the measurement light as the wavelength calibration light, the measurement light is narrowed by the optical filter insertion / extraction mechanism 81 provided with the band-pass filter, but the optical filter insertion / extraction mechanism 81 Instead, the measurement light may be narrowed by a monochromator unit including a diffraction grating and a slit member formed with a slit that transmits only light of a predetermined order diffracted by the diffraction grating. In this case, the wavelength calibration light is monochromatic light obtained by monochromating the measurement light with the monochromator unit. Even with such a configuration, the measurement light can be diverted to the wavelength calibration light.

  Further, in the FT spectrometers Da to Dd in the first to fourth embodiments described above, the peak position searched for the wavelength calibration pricing is deviated by a predetermined value or more from the peak position preset as a default, for example. In this case, for example, in order to prompt the user to perform wavelength calibration at the manufacturer, the FT spectrometers Da to Dd may be configured to warn a message to that effect. With this configuration, it is possible to notify the user of the maintenance time of the FT spectrometers Da to Dd.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. To be construed as inclusive.

Da, Db, Dc, Dd Fourier transform spectrometer 10 Interferometers 20a, 20b Light reception processing unit 30 Position detection processing unit 41 Control calculation units 50a, 50b, 50c, 50d Measurement calibration optical system 52 First transmission light shielding mechanism unit 72 2-transmission light shielding mechanism 81 Optical filter insertion / extraction mechanism 411 Control unit 412 Sampling data storage unit 413 Interferogram extraction unit 414 Spectrum calculation unit 415 White calibration unit 416 Wavelength calibration unit 417 Calibration data storage unit

Claims (10)

A measurement light source that emits measurement light for measurement; and
A wavelength calibration light source that emits wavelength calibration light for wavelength calibration;
A Fourier transform spectroscopic unit for obtaining a spectrum of the predetermined light using a Fourier transform based on an interferogram obtained by causing the predetermined light to interfere; and
A white calibration unit for white calibration of the Fourier transform spectroscopic unit by causing the reflected white calibration light reflected by the white calibration plate to reflect the measurement light as the predetermined light to the Fourier transform spectroscopic unit;
A wavelength calibration unit that calibrates the wavelength of the Fourier transform spectroscopic unit by causing the reflected wavelength calibration light reflected by the white calibration plate to be incident on the Fourier transform spectroscopic unit as the predetermined light;
The Fourier transform spectrometer, wherein the white calibration unit and the wavelength calibration unit perform white calibration and wavelength calibration successively in time. The Fourier transform spectrometer according to claim 1, wherein each of the measurement light source and the wavelength calibration light source is a separate light source. The said wavelength calibration light source is a flat light emission xenon lamp provided with a xenon lamp and the flat light emission control part which makes the said xenon lamp light-emit with fixed light intensity within predetermined time after light emission. Or a Fourier transform spectrometer according to claim 2. The wavelength calibration light source includes a light source of any one of a light emitting diode and a laser light source, a temperature measuring unit that measures a temperature related to the light source, and the light source based on a temperature measured by the temperature measuring unit. The Fourier transform spectrometer according to claim 1, wherein the Fourier transform spectrometer is a constant wavelength light source including a light emission wavelength control unit that emits light at a wavelength of 5. The Fourier transform spectroscopic unit,
A plurality of optical elements that form two optical paths between an incident position of the predetermined light and an interference position; and the plurality of optical elements move between the two optical paths by moving in an optical axis direction. An interferometer including an optical path difference forming optical element that generates an optical path difference;
A position detection monochromatic light source that emits monochromatic light for position detection for detecting a position on the optical axis of the optical path difference forming optical element;
A timing output unit that outputs a cross signal at a timing when a signal obtained by photoelectrically converting the interference light of the monochromatic light generated by the interferometer crosses a predetermined reference value;
An interferogram measuring unit for measuring the interferogram of the predetermined light generated by the interferometer by sampling with the zero-cross signal;
A spectrum calculation unit for obtaining a spectrum of the predetermined light using Fourier transform based on the interferogram measured by the interferogram measurement unit,
The wavelength calibration light source is also used as the position detection monochromatic light source, and the wavelength calibration light is a part of the position detection monochromatic light. Fourier transform spectrometer. A wavelength conversion unit that converts the wavelength of a part of the position detection monochromatic light into a wavelength that can be measured by the interferogram measurement unit;
6. The Fourier transform spectrometer according to claim 5, wherein the wavelength calibration light is wavelength converted light obtained by wavelength-converting a part of the position detection monochromatic light by the wavelength conversion unit. 6. The Fourier according to claim 5, wherein the wavelength calibration unit expands the measurement wavelength range of the interferogram measurement unit by oversampling so that the wavelength of a part of the position detection monochromatic light can be measured. Conversion spectrometer. A band pass filter having a known wavelength as the transmission center wavelength and having a transmission wavelength band equivalent to a bright line,
The Fourier transform spectrometer according to claim 1, wherein the wavelength calibration light is filtered light obtained by filtering the measurement light with the band-pass filter. A monochromator unit further comprising a diffraction grating and a slit member formed with a slit that transmits only light of a predetermined order diffracted by the diffraction grating;
The Fourier transform spectrometer according to claim 1, wherein the wavelength calibration light is monochromatic light obtained by monochromatizing the measurement light in the monochromator unit. Reflected white calibration in which measurement light for measurement is reflected by a white calibration plate to a Fourier transform spectroscopic unit that obtains a spectrum of the predetermined light using Fourier transform based on an interferogram obtained by interfering with predetermined light A white calibration step of white-calibrating the Fourier transform spectroscopic unit by making light incident as the predetermined light;
A wavelength calibration step of calibrating the wavelength of the Fourier transform spectroscopic unit by making the reflected wavelength calibration light reflected from the wavelength calibration light for wavelength calibration reflected on the white calibration plate enter the Fourier transform spectroscopic unit as the predetermined light, and
The method of calibrating a Fourier transform spectrometer, wherein the white calibration step and the wavelength calibration step are performed continuously in time.

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