Interferometer

Abstract

An interferometer provided by the invention is provided with a moving mirror that has sufficient permissibility for jitter during movement while suppressing an increase in size of a drive unit. The interferometer is characterized by being provided with: an analysis optical system that has a retroreflection unit that reflects analysis light, and a first light-receiving element that receives the analysis light and outputs a first light-receiving signal, the analysis optical system irradiating the sample with the analysis light and interfering with the analysis light; and a length measurement optical system that includes a laser light source that emits the laser light, an optical modulator that modulates the frequency of the laser light using a resonator element and adds a modulation component, and a second light receiving element that receives the laser light including the length measurement component and the modulation component and outputs a second light receiving signal, and that interferes with the laser light. The length measurement component is generated by irradiating the laser light to the retroreflection part; and a drive unit that changes the position of the retroreflective unit.

Description

Technical Field

[0001] The present invention relates to interferometers. Background Art

[0002] Patent document 1 discloses an optical module used in spectroscopic analysis, which obtains spectral information of light radiated or absorbed by a sample and analyzes the components in the sample based on the spectral information. The optical module includes a reflector unit, a beam splitter unit, a light incident portion, a first light detector, a second light source, and a second light detector. The reflector unit includes a movable reflector that moves in a specified direction and a fixed reflector whose position is fixed. In such an optical module, the beam splitter unit, the movable reflector, and the fixed reflector constitute an interference optical system into which the measurement light and the laser light are incident respectively.

[0003] The measurement light incident from the first light source via the measurement object is split in the beam splitter unit through the light incident portion. A portion of the split measurement light is reflected by the movable reflector and returns to the beam splitter unit. The remaining portion of the split measurement light is reflected by the fixed reflector and returns to the beam splitter unit. The portion of the measurement light returned to the beam splitter unit and the remaining portion are detected as interference light by the first light detector.

[0004] On the other hand, the laser light emitted from the second light source is split in the beam splitter unit. A portion of the split laser light is reflected by the movable reflector and returns to the beam splitter unit. The remaining portion of the split laser light is reflected by the fixed reflector and returns to the beam splitter unit. A portion of the laser light returned to the beam splitter unit and the remaining portion are detected as interference light by the second photodetector.

[0005] In such an optical module, the position of the movable reflector is measured based on the detection result of the interference light of the laser. Moreover, it is possible to perform a spectroscopic analysis on the measurement object based on the measurement result of the position of the movable reflector and the detection result of the interference light of the measurement light. Specifically, by finding the intensity of the measurement light at each position of the movable reflector, a waveform called an interference pattern can be obtained. By performing Fourier transform on the interference pattern, spectral information on the measurement object can be obtained. Therefore, the optical module described in Patent Document 1 is used for FTIR (Fourier transform infrared spectrometer).

[0006] Patent Document 1: International Publication No. 2019 / 009404

[0007] In the optical module described in Patent Document 1, the movable reflector is driven by an electrostatic actuator. In order to achieve high precision of the acquired spectral information, it is important that the light incident on the movable reflector and the light emitted do not shift in a direction orthogonal to the propagation direction as the movable reflector is driven, in other words, the jitter is small. Therefore, it is required to improve the translational performance of the movable reflector. However, in the optical module described in Patent Document 1, the translational performance of the movable reflector is not fully considered, and there is still room for research.

[0008] On the other hand, ensuring sufficient movement of the movable mirror is important for improving the wavelength resolution (wave number resolution) of the acquired spectral information. However, in order to improve the translational performance of the movable mirror and ensure sufficient movement, the drive unit that drives the movable mirror needs to be enlarged.

[0009] Therefore, it is a problem to realize an interferometer including a moving mirror having a sufficient tolerance for vibration during movement while suppressing an increase in the size of a driving unit. Summary of the invention

[0010] The interferometer involved in the application example of the present invention comprises: an analysis optical system, having a retroreflection part that reflects analysis light and a first light receiving element, the analysis optical system irradiates the analysis light with respect to a sample and interferes with the analysis light, the first light receiving element receives the analysis light and outputs a first light receiving signal; a length measurement optical system, having a laser light source, a light modulator and a second light receiving element, and performing laser interference, the laser light source emits the laser light, the light modulator modulates the frequency of the laser light using a vibration element and adds a modulation component, the second light receiving element receives the laser light including the length measurement component and the modulation component, and outputs a second light receiving signal, the length measurement component is generated by irradiating the laser light to the retroreflection part; and a drive part that changes the position of the retroreflection part. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a diagram schematically showing the configuration of a spectroscopic device as an interferometer according to the first embodiment.

[0012] Figure 2 Yes means Figure 1 A schematic diagram showing the main components of the analysis unit, length measurement unit, periodic signal generation unit and calculation unit.

[0013] Figure 3 Yes means Figure 1 A perspective view of a structural example of a vibration element shown.

[0014] Figure 4 Yes means Figure 1 A perspective view of another configuration example of a vibration element shown.

[0015] Figure 5 It means to use Figure 1 FIG. 1 is a diagram showing an example of a first light receiving signal F(t) and a movable mirror position signal X(t) acquired by the spectroscopy device shown.

[0016] Figure 6 It is a diagram showing an example of the interference pattern F(x).

[0017] Figure 7 This is an example of a spectrum pattern SP0 obtained by spectroscopically analyzing a sample.

[0018] Figure 8 Yes means Figure 1 A side view of an example of a corner cube prism.

[0019] Fig. 9 It is overlooking Figure 8 Top view of the retroreflective surface.

[0020] Fig.10 This is a side view showing a retroreflector provided as a movable reflector according to a modification of the first embodiment.

[0021] Fig.11 It is a side view showing a corner cube provided as a movable reflecting mirror according to the second embodiment.

[0022] Fig.12 This is a side view showing a retroreflector provided as a movable reflector according to a modification of the second embodiment.

[0023] Fig.13 It is a diagram schematically showing the configuration of a spectroscopic apparatus as an interferometer according to the third embodiment.

[0024] Fig.14 FIG. 1 is a diagram schematically showing the configuration of a shape measuring device as an interferometer according to a fourth embodiment.

[0025] Fig.15 Yes means Fig.14 A schematic diagram showing the main components of the analysis unit, length measurement unit, periodic signal generation unit and calculation unit.

[0026] Description of Reference Numerals

[0027] 3…Analysis optical system, 4…Length measuring optical system, 6…Periodic signal generating unit, 7…Calculation unit, 8…Drive unit, 9…Sample, 12…Light modulator, 30…Vibration element, 32…Beam splitter, 33…Moving mirror, 34…Fixed mirror, 35…Condenser lens, 36…First light receiving element, 37…Condenser lens, 41…Second light source, 42…Beam splitter, 45…Second light receiving element, 46…1 / 2 wavelength plate, 47…1 / 2 wavelength plate, 48…1 / 4 wavelength plate, 49…Analyzer, 51…First light source, 54…Beam splitter, 55…Condenser lens, 56…Extinction filter, 62…Oscillator circuit, 64…Rectangular wave generating circuit , 72…movable reflector position calculation unit, 74…light intensity calculation unit, 76…Fourier transform unit, 78…shape calculation unit, 82…reflector drive signal generation unit, 100…spectrometer, 200…shape measurement device, 300…analyzer, 330…corner cube, 330A…corner cube, 330B…corner cube, 331…corner cube reflector, 331A…corner cube reflector, 331B…corner cube reflector, 332…incident surface, 333…anti-reflection film, 334…retro-reflection surface, 334A…analysis light reflection surface, 334B…laser reflection surface, 335…surface, 335a…area, 335b…area, 336…surface, 337…area, 338…area, 339…surface, 340…area, 341…area, 342…surface, 343…area, 344…area, 345…surface, 346…surface, 347…area, 348…area, 349…surface, 350…area, 351…area, 352…surface, 353…area, 354…area, 355…area, 356…surface, 357…area, 358…area, 359…surface, 360…surface, 361…surface, 362…surface, 363…surface, 364…surface, 365…surface, 366…surface, 367…surface, 368…surface, 369…surface, 370…surface, 37 6a...area, 336b...area, 337...surface, 337a...area, 337b...area, 338...carrying portion, 341...flat reflector, 342...flat reflector, 400...length measuring portion, 401...base, 402...first vibration arm, 403...second vibration arm, 404...electrode, 405...electrode, 406...light reflecting surface, 431...vibrating plate, 432...groove, 433...pad, 434...diffraction grating, 435...pad, 436...vibration direction, 441...optical path changing reflector, 442...optical path changing reflector, 443...optical path changing reflector, 444...optical path changing reflector, 445...beam splitter, 7 22…preprocessing unit, 724…demodulation processing unit, 726…movable reflector position signal output unit, 862…power conversion unit, 4311…surface, 4312…back side, F(x)…interference pattern, F(t)…first light receiving signal, L1…analysis light, L1a…analysis light, L1b…analysis light, L2…length measuring light, L2a…length measuring light, L2b…length measuring light, LP1…optical path, LP2…optical path, M…motor, S2…second light receiving signal, SP0…spectral pattern, Sd…element driving signal, Sm…mirror driving signal, Sp…pulse signal, Ss…reference signal, X(t)…movable reflector position signal, X9…absorption peak. DETAILED DESCRIPTION

[0028] Hereinafter, the interferometer of the present invention will be described in detail based on the embodiments shown in the drawings.

[0029] 1. First Implementation

[0030] First, the interferometer according to the first embodiment will be described.

[0031] Figure 1 1 is a diagram schematically showing the configuration of a spectroscopic apparatus 100 as an interferometer according to the first embodiment. Figure 2 Yes means Figure 1 A schematic diagram of the main components of the analysis unit 300, the length measurement unit 400, the periodic signal generation unit 6 and the calculation unit 7.

[0032] exist Figure 1 In the spectral device 100 shown, incident analysis light L1 is irradiated onto a sample 9 as a test object, and analysis light L1 emitted from sample 9 is passed through a Michelson interference optical system. Furthermore, while moving a movable reflector to change the optical path length inside the interference optical system, the intensity change of the obtained interference light is detected, and the result is calculated to obtain an interference pattern. By Fourier transforming the obtained interference pattern, a spectral pattern (spectral information) containing information from sample 9 is obtained. By selecting the wavelength of analysis light L1, Figure 1 The spectroscopic device 100 shown can be applied to, for example, FT-IR (Fourier infrared spectroscopy), FT-NIR (Fourier near infrared spectroscopy), FT-VIS (Fourier visible spectroscopy), FT-UV (Fourier ultraviolet spectroscopy), FT-THz (Fourier terahertz spectroscopy), etc. for sample 9.

[0033] like Figure 1 As shown, the spectroscopic device 100 includes an analysis unit 300 , a length measuring unit 400 , a periodic signal generating unit 6 , and a computing unit 7 . The analysis unit 300 includes an analysis optical system 3 and a driving unit 8 , and the length measuring unit 400 includes a length measuring optical system 4 .

[0034] The analysis optical system 3 irradiates the analysis light L1 to the sample 9, changes the optical path length of the analysis light L1 to extract the sample-derived component from the sample 9 from the analysis light L1, and divides and mixes the analysis light L1 to generate interference. In the length measurement optical system 4, the change in the optical path length of the analysis light L1 is measured using the length measurement light L2 as a laser.

[0035] The periodic signal generating unit 6 outputs the reference signal Ss to the computing unit 7. The computing unit 7 obtains a waveform representing the intensity of the interference light relative to the optical path length, that is, the aforementioned interference pattern, based on the signal representing the intensity of the interference light output from the analyzing optical system 3 and the signal representing the change in the optical path length output from the length measuring optical system 4. In addition, the computing unit 7 performs Fourier transform on the interference pattern to obtain a spectrum pattern.

[0036] 1.1. Analysis of optical system

[0037] The analysis optical system 3 includes a first light source 51, a beam splitter 54, a condenser lens 55, and an extinction filter 56. In addition, in the analysis optical system 3, some of these optical elements may be omitted, other optical elements may be included, or these optical elements may be replaced with other optical elements.

[0038] The first light source 51 is a light source that emits, for example, white light, that is, light obtained by converging wide-wavelength light, as analysis light L1. The wavelength band of the analysis light L1, that is, the type of the first light source 51, is appropriately selected according to the purpose of the spectroscopic analysis of the sample 9. In the case of infrared spectroscopic analysis, as the first light source 51, for example, a halogen lamp, an infrared lamp, a tungsten lamp, etc. can be cited. In the case of visible spectroscopic analysis, as the first light source 51, for example, a halogen lamp can be cited. In the case of ultraviolet spectroscopic analysis, as the first light source 51, for example, a deuterium lamp, a UV-LED (ultraviolet light emitting diode), etc. can be cited.

[0039] Furthermore, by selecting a wavelength of 100 nm or more and less than 760 nm as the wavelength of the analysis light L1, a spectroscopic device 100 capable of ultraviolet spectroscopic analysis or visible spectroscopic analysis can be realized. Furthermore, by selecting a wavelength of 760 nm or more and less than 20 μm as the wavelength of the analysis light L1, a spectroscopic device 100 capable of infrared spectroscopic analysis or near-infrared spectroscopic analysis can be realized. Furthermore, by selecting a wavelength of 30 μm or more and less than 3 mm as the wavelength of the analysis light L1, a spectroscopic device 100 capable of terahertz wave spectroscopic analysis can be realized.

[0040] In addition, the first light source 51 may be provided outside the spectroscopic device 100. In this case, the analysis light L1 emitted from the first light source 51 provided outside only needs to be introduced into the spectroscopic device 100. On the other hand, by providing the spectroscopic device 100 with the first light source 51 as in the present embodiment, the alignment accuracy between the first light source 51 and the beam splitter 54 can be particularly improved, and the loss of the analysis light L1 caused by poor alignment can be suppressed to a minimum.

[0041] In addition, the first light source 51 may also be a laser light source that emits laser light. By using a laser light source as the first light source 51, a spectral device 100 that can realize laser excitation spectroscopic analysis such as Fourier Raman spectroscopic analysis and Fourier fluorescence spectroscopic analysis for the sample 9 can be obtained. In addition, in this case, the structure of the analysis optical system 3 can be changed from the above structure. In this case, as the laser light source, a known light source used in Raman spectrometry and fluorescence spectrometry is used.

[0042] The analysis light L1 passes through the beam splitter 54, is focused by the focusing lens 55, and then irradiates the sample 9. The analysis light L1 is reflected in the sample 9 and returns to the beam splitter 54. Thus, it is possible to perform spectroscopic analysis based on the reflected light emitted from the sample 9, that is, to perform analysis by reflection spectroscopy. In addition, by changing the optical path of the analysis optical system 3, it is possible to perform analysis by transmission spectroscopy.

[0043] For example, a non-polarization beam splitter is used as the beam splitter 54 , but a polarization beam splitter may be used. In this case, necessary wavelength plates may be appropriately added.

[0044] The condenser lens 55 condenses the analysis light L1 to reduce the spot size of the analysis light L1 irradiated to the sample 9. In addition, the condenser lens 55 condenses the diffused light emitted from the sample 9. This enables local analysis. If local analysis is not required, the condenser lens 55 may be omitted.

[0045] The analysis light L1 emitted from the sample 9 includes a sample-derived component generated by the action with the sample 9. The sample-derived component is a component generated by the action of the analysis light L1 on the sample 9, and the absorption, reflection, scattering, and luminescence of light of a specific wavelength by the sample 9 can be cited as the form of action. The analysis light L1 passes through the focusing lens 55, is reflected by the beam splitter 54, and passes through the extinction filter 56. The extinction filter 56 selectively attenuates light of a specified wavelength. As a result, the S / N ratio (signal-to-noise ratio) of the sample-derived component can be improved, so that spectroscopic analysis can be performed with higher accuracy. As the extinction filter 56, for example, a notch filter with an optical density (OD value) of 6.0 or more can be cited.

[0046] The analysis optical system 3 includes a beam splitter 32 (light dividing section), a movable reflector 33 (retroreflector), a fixed reflector 34 (fixed reflector), a condenser lens 35, and a first light receiving element 36, which constitute a Michelson interference optical system. In addition, in the analysis optical system 3, some of these optical elements may be omitted, optical elements other than these may be included, and these optical elements may be replaced by other optical elements.

[0047] The beam splitter 32 is a non-polarization beam splitter that splits the analysis light L1 into two analysis lights L1a and L1b. Specifically, the beam splitter 32 reflects a portion of the analysis light L1 as analysis light L1a toward the movable reflector 33 and transmits another portion of the analysis light L1 as analysis light L1b toward the fixed reflector 34, thereby splitting the analysis light L1 into two.

[0048] As the type of the beam splitter 32, for example, Figure 1In addition to the prism-type element (cube-type element) shown, plate-type elements, stacked elements, etc. can also be cited. When a plate-type beam splitter 32 is used, wavelength dispersion occurs in the analysis light L1a and the analysis light L1b, so a wavelength dispersion compensation plate can be configured between the beam splitter 32 and the fixed reflector 34 as needed. The wavelength dispersion compensation plate is an optical element that compensates for the wavelength dispersion caused by the optical path length difference of the glass material. In this embodiment, a prism-type element is used as the beam splitter 32, so the wavelength dispersion compensation plate is not required. The prism-type element is an element in the form of an optical film sandwiched between prisms. In addition, the stacked element is an element in the form of an optical film sandwiched between two transparent flat plates. The stacked element can also be similar to the prism-type element without the need for a wavelength dispersion compensation plate. In addition, in the prism-type element or the stacked element, the optical film will not be exposed, so the long-term reliability of the beam splitter 32 can be improved.

[0049] The beam splitter 32 transmits the analysis light L1a reflected by the movable mirror 33 toward the first light receiving element 36, and reflects the analysis light L1b reflected by the fixed mirror 34 toward the first light receiving element 36. Therefore, the beam splitter 32 mixes the split analysis lights L1a and L1b.

[0050] The movable reflecting mirror 33 is a reflecting mirror that moves in the incident direction of the analysis light L1a relative to the beam splitter 32 and reflects the analysis light L1a. The movable reflecting mirror 33 is moved in a reciprocating manner in the incident direction of the aforementioned analysis light L1a by the driving unit 8. The phase of the analysis light L1a reflected by the movable reflecting mirror 33 changes according to the position of the movable reflecting mirror 33. Thus, the movable reflecting mirror 33 adds phase information derived from the position of the movable reflecting mirror 33 to the analysis light L1a. The phase information derived from the position of the movable reflecting mirror 33 is a change in the phase of the analysis light L1a added according to the position of the movable reflecting mirror 33.

[0051] The movable reflector 33 (retroreflective portion) has a corner cube prism 330. The corner cube prism 330 is also called a retroreflective prism, and has a function of retroreflecting light incident at an incident angle within a specified range and returning it to the incident direction. In this specification, such a function is referred to as "retroreflectivity". By using an optical element with retroreflectivity as the movable reflector 33, the tolerance of the jitter generated when the movable reflector 33 moves can be expanded compared to the case of using a flat reflector. In other words, even if an angular deviation (deflection angle) is generated when the movable reflector 33 moves accompanied by jitter, the influence of the angular deviation can be reduced, and the influence on the analysis result can be suppressed. In addition, when a flat reflector is used, retroreflection occurs only when the incident angle is 0°, but in an optical element with retroreflectivity such as the corner cube prism 330, retroreflection occurs even when the incident angle exceeds 0°.

[0052] The corner cube 330 reflects the analysis light L1a in reverse and returns it to the beam splitter 32 in an emission path parallel to the incident path. In addition, due to the retroreflectivity, even if the movable reflector 33 vibrates when it moves, the emission path does not change. By utilizing this characteristic, the mixed state of the analysis lights L1a and L1b in the beam splitter 32 can be maintained constant. As a result, the S / N ratio of the interference signal of the analysis lights L1a and L1b can be suppressed from decreasing due to the vibration of the movable reflector 33 when it moves, and the influence on the analysis result can be suppressed. The corner cube 330 will be described in detail later.

[0053] In addition, the tolerance of the vibration generated when the movable reflector 33 moves can be increased, so that the priority of the driving accuracy of the drive unit 8 can be reduced. Therefore, even when the moving amount of the movable reflector 33 by the drive unit 8 is sufficiently ensured, a small drive unit 8 can be used. Thus, the spectral device 100 can be miniaturized, lightweight, and low-cost.

[0054] The fixed reflector 34 is a reflector that is fixed in position relative to the beam splitter 32 and reflects the analysis light L1b. The analysis light L1b reflected by the fixed reflector 34 is mixed with the analysis light L1a in the beam splitter 32 and is received by the first light receiving element 36 as interference light. In the analysis optical system 3, an optical path difference is generated between the optical path of the analysis light L1a and the optical path of the analysis light L1b according to the position of the movable reflector 33. The fixed reflector 34 may be a flat reflector, a corner cube prism, or a corner cube reflector. Figure 1 The fixed reflector 34 shown is composed of a toroidal reflector formed by combining two flat reflectors 341 and 342. By using a retro-reflective corner cube prism, a corner cube reflector, a toroidal reflector, etc. in the fixed reflector 34, it is possible to suppress the decrease in the S / N ratio of the interference signal due to the angular deviation (deflection angle) of the configuration of the fixed reflector 34, and to suppress the influence on the analysis result.

[0055] The condenser lens 35 condenses the interference light, that is, the mixed analysis light L1a, L1b, at the first light receiving element 36. Depending on the area of ​​the light receiving portion of the first light receiving element 36, the condenser lens 35 may be omitted.

[0056] The first light receiving element 36 receives the interference light and obtains its intensity. Furthermore, a signal indicating the time variation of the intensity is output as a first light receiving signal F(t). The first light receiving signal F(t) includes a sample-derived component generated by the interaction between the analysis light L1 and the sample 9 and phase information derived from the position of the aforementioned movable reflector 33.

[0057] Examples of the first light receiving element 36 include photodiodes, phototransistors, photomultiplier tubes (PMTs), etc. Examples of the photodiodes include InGaAs-based photodiodes, Si-based photodiodes, and avalanche photodiodes.

[0058] 1.2. Length measurement optical system

[0059] The length measuring optical system 4 is a Michelson type interference optical system, and includes a second light source 41, a beam splitter 42, an optical modulator 12, a second light receiving element 45, a 1 / 2 wavelength plate 46, a 1 / 2 wavelength plate 47, a 1 / 4 wavelength plate 48, an analyzer 49, optical path changing mirrors 441, 442, 443, 444, and a beam splitter 445. In addition, in the length measuring optical system 4, some of these optical elements may be omitted, optical elements other than these may be included, and these optical elements may be replaced by other optical elements. The length measuring optical system 4 outputs phase information derived from the position of the moving mirror 33 and frequency information derived from the moving speed to the calculation unit 7 by optical heterodyne interferometry. In this specification, these information are referred to as "length measuring components".

[0060] The second light source 41 is preferably a light source that emits light with a narrow spectral line width. Examples of the second light source 41 include gas lasers such as He-Ne lasers and Ar lasers, semiconductor laser elements such as DFB-LD (Distributed FeedBack-LaserDiode), FBG-LD (Fiber Bragg Grating-Laser Diode), VCSEL (Vertical Cavity Surface Emitting Laser), FP-LD (Fabry-Perot Laser Diode), and crystal lasers such as YAG (Yttrium Aluminum Garnet).

[0061] The second light source 41 is preferably a semiconductor laser element. Thus, the spectroscopy device 100 can be made smaller, lighter, and have lower power consumption.

[0062] The beam splitter 42 is a polarization beam splitter that transmits P polarized light and reflects S polarized light. The 1 / 2 wavelength plate 46 is arranged in a state where its optical axis is rotated relative to the polarization axis of the length measurement light L2. As a result, the length measurement light L2 becomes linearly polarized light including P polarized light and S polarized light when passing through the 1 / 2 wavelength plate 46, and is split into two by the beam splitter 422, namely, P polarized light and S polarized light.

[0063] The length measurement light L2a, which is S polarized light, is converted into circularly polarized light by the 1 / 4 wavelength plate 48 and enters the optical modulator 12. The optical modulator 12 adds a modulation component to the length measurement light L2a by reflecting the length measurement light L2a. The modulation component is a change in frequency caused by the reflection of the length measurement light L2a by the vibration element 30. The reflected length measurement light L2a returns to the beam splitter 42. At this time, the length measurement light L2a is converted into P polarized light by the 1 / 4 wavelength plate 48.

[0064] On the other hand, the length measurement light L2b, which is P polarized light, is converted into S polarized light by the 1 / 2 wavelength plate 47, and enters the movable mirror 33 via the optical path changing mirrors 441 and 442. The length measurement light L2b is incident on the same incident surface of the movable mirror 33 as the analysis light L1a under the guidance of the optical path changing mirrors 441 and 442. The movable mirror 33 reflects the length measurement light L2b. As a result, the phase of the length measurement light L2b changes according to the position of the movable mirror 33. The length measurement light L2b reflected by the movable mirror 33 enters the beam splitter 445 via the optical path changing mirrors 443 and 444.

[0065] In this embodiment, as described above, the analysis light L1a and the length measurement light L2b are incident on the same incident surface of the movable reflector 33. In this case, the phase information added to the analysis light L1a and the phase information added to the measurement light L2b are information derived from the position of the same reflection surface of the movable reflector 33. Therefore, the correlation between the phase information of both parties can be further improved, and the accuracy of the analysis result finally obtained can be improved.

[0066] In addition, the beam splitter 42 allows the length measurement light L2a returned from the optical modulator 12 to pass toward the beam splitter 445. The beam splitter 445 is a polarization beam splitter, and mixes the length measurement light L2a emitted from the beam splitter 42 and the length measurement light L2b reflected by the movable reflector 33. The mixed length measurement lights L2a and L2b pass through the analyzer 49 and enter the second light receiving element 45.

[0067] As the optical modulator 12, for example, the optical modulator disclosed in Japanese Patent Publication No. 2022-38156 can be cited. In this embodiment, the optical modulator 12 has a vibration element 30. The vibration element 30 vibrates according to the element driving signal Sd and reflects the length measurement light L2a. As a result, the optical modulator 12 superimposes a modulation component on the length measurement light L2a.

[0068] As the vibration element 30, for example, a crystal vibrator, a silicon vibrator, a ceramic vibrator, etc. can be cited. These vibrators are vibrators that utilize the mechanical resonance phenomenon, so the Q value is high and the natural vibration frequency can be easily stabilized. As a result, the S / N ratio of the modulation component applied by the optical modulator 12 to the length measurement light L2a can be improved, and the accuracy of the reference signal Ss can be improved. As a result, the position of the movable reflector 33 can be obtained with high accuracy, and finally the spectrum device 100 that can generate a spectrum pattern with high accuracy of the wavelength axis (wave number axis) can be realized.

[0069] Examples of the crystal oscillator include an AT-cut crystal oscillator, an SC-cut crystal oscillator, a tuning fork-type crystal oscillator, and a crystal surface acoustic wave device. The oscillation frequency of the crystal oscillator is, for example, about 1 kHz to several hundred MHz.

[0070] A silicon vibrator is a vibrator having a single crystal silicon wafer and a piezoelectric film. The single crystal silicon wafer is manufactured from a single crystal silicon substrate using MEMS technology. MEMS (Micro Electro Mechanical Systems) is a micro-electromechanical system. As the shape of the single crystal silicon wafer, for example, a two-legged tuning fork type, a three-legged tuning fork type, a single support beam shape, a double support beam shape, etc. can be cited. The oscillation frequency of the silicon vibrator is, for example, about 1kHz to hundreds of MHz.

[0071] A ceramic vibrator is a vibrator having a piezoelectric ceramic sheet and electrodes. The piezoelectric ceramic sheet is manufactured by sintering and solidifying a piezoelectric ceramic. Examples of piezoelectric ceramics include lead zirconate titanate (PZT) and barium titanate (BTO). The oscillation frequency of a ceramic vibrator is, for example, about hundreds of kHz to tens of MHz.

[0072] Figure 3 Yes means Figure 1 A perspective view of a configuration example of the vibration element 30 shown.

[0073] Figure 3 The illustrated vibration element 30 includes a plate-shaped vibration piece 431 and a diffraction grating 434 provided on the vibration piece 431 .

[0074] The vibrating piece 431 is made of a material that repeatedly performs a mode of vibrating so as to be distorted in a direction along the surface when a potential is applied. Figure 3 The vibration piece 431 shown is an AT-cut crystal vibrator that performs thickness shear vibration in a high frequency region of the MHz band along a vibration direction 436. In addition, a diffraction grating 434 is provided on the surface of the vibration piece 431. The diffraction grating 434 has grooves 432, that is, a plurality of linear grooves 432 extending in a direction intersecting the vibration direction 436, and the grooves 432 have a component intersecting the vibration direction 436.

[0075] The vibrating piece 431 has a front surface 4311 and a back surface 4312 which are in a front-back relationship with each other. A diffraction grating 434 is arranged on the front surface 4311. In addition, a pad 433 for applying a potential to the vibrating piece 431 is provided on the front surface 4311. On the other hand, a pad 435 for applying a potential to the vibrating piece 431 is also provided on the back surface 4312.

[0076] The vibration piece 431 has a size of, for example, a long side of about 0.50 mm to about 10.0 mm. The thickness of the vibration piece 431 is, for example, about 0.10 mm to about 2.0 mm. For example, the vibration piece 431 is in the shape of a square with a side of 1.6 mm and a thickness of 0.35 mm.

[0077] The size of the diffraction grating 434 is, for example, about 0.20 mm or more and 3.0 mm or less in length. The thickness of the diffraction grating 434 is, for example, about 0.003 mm or more and 0.5 mm or less.

[0078] In this embodiment, the vibration piece 431 performs thickness shear vibration, but Figure 3 As shown in FIG. 4 as the vibration direction 436, this vibration is in-plane vibration, so even if light is incident perpendicularly on the surface of the vibration piece 431, light modulation cannot be performed. Therefore, in the vibration element 30, by providing the diffraction grating 434 on the vibration piece 431, light modulation can be performed.

[0079] As an example, Figure 3 The diffraction grating 434 shown is a blazed diffraction grating. A blazed diffraction grating is a grating whose cross-sectional shape is a step-shaped grating. In addition, the shape of the diffraction grating 434 is not limited to this.

[0080] Figure 4 Yes means Figure 1 30 is a perspective view of another configuration example of the vibration element 30 shown in FIG. Figure 4 In the diagram, the A-axis, B-axis, and C-axis are set as three mutually orthogonal axes and are indicated by arrows. The tip side of the arrow is set as "positive", and the base side of the arrow is set as "negative". In addition, for example, the two directions of the positive side and the negative side of the A-axis are called "A-axis directions". The B-axis direction and the C-axis direction are also the same.

[0081] Figure 4 The vibration element 30 shown is a tuning fork type crystal vibrator. Figure 4The vibration element 30 shown has a vibration substrate having a base 401 and a first vibration arm 402 and a second vibration arm 403. Such a tuning fork type crystal vibrator can be easily obtained because the manufacturing technology has been established, and the oscillation is also stable. Therefore, the tuning fork type crystal vibrator is suitable as the vibration element 30. In addition, the vibration element 30 has electrodes 404, 405 and a light reflecting surface 406 provided on the vibration substrate.

[0082] The base 401 extends along the A axis. The first vibration arm 402 extends from the end of the base 401 on the negative side of the A axis toward the positive side of the B axis. The second vibration arm 403 extends from the end of the base 401 on the positive side of the A axis toward the positive side of the B axis.

[0083] The electrode 404 is a conductive film provided on the side surface parallel to the AB plane in the first vibration arm 402 and the second vibration arm 403. Figure 4 Although not shown in the figure, the electrodes 404 are provided on the side surfaces facing each other, and the first vibration arm 402 and the second vibration arm 403 are driven by applying voltages with different polarities.

[0084] The electrode 405 is a conductive film provided on the side surface of the first vibration arm 402 and the second vibration arm 403 intersecting with the AB plane. Figure 4 Although not shown in the figure, the electrodes 405 are also provided on the side surfaces facing each other, and the first vibration arm 402 and the second vibration arm 403 are driven by applying voltages with different polarities.

[0085] The light reflecting surface 406 is set on the side surface of the first vibration arm 402 and the second vibration arm 403 that intersects the AB plane and has the function of reflecting the length measuring light L2a. The side surface refers to a surface extending along the extending direction of the first vibration arm 402 and the second vibration arm 403. Figure 4 The light reflecting surface 406 shown is set on the side surface of the first vibrating arm 402, especially on the surface of the electrode 405. The electrode 405 provided on the first vibrating arm 402 also functions as the light reflecting surface 406. In addition, a light reflecting film (not shown) may be provided separately from the electrode 405.

[0086] The tuning fork type crystal oscillator uses a crystal piece cut from a crystal substrate. As the crystal substrate used to manufacture the tuning fork type crystal oscillator, for example, a Z-cut crystal plate can be cited. Figure 4In the embodiment, an X-axis parallel to the A-axis, a Y'-axis parallel to the B-axis, and a Z'-axis parallel to the C-axis are set. A Z-cut crystal flat plate is, for example, a substrate cut from a single crystal of crystal in such a way that the X-axis becomes the electrical axis, the Y'-axis becomes the mechanical axis, and the Z'-axis becomes the optical axis. Specifically, a substrate is cut from a single crystal of crystal and suitably used as a crystal substrate, the substrate having a main surface in which an X-Y' plane formed by the X-axis and the Y'-axis is tilted counterclockwise about the X-axis by about 1° to 5° in an orthogonal coordinate system formed by the X-axis, the Y'-axis, and the Z'-axis. Moreover, by etching such a crystal substrate, a Figure 4 The crystal piece shown is used in the vibration element 30. The etching may be wet etching or dry etching.

[0087] On the other hand, the light reflecting surface 406 may be set on the surface of the electrode 404. In this case, the signal applied to each electrode is adjusted so that the tuning fork type crystal resonator vibrates out of plane, specifically, excites the out of plane vibration mode (including the unnecessary wave component).

[0088] The second light receiving element 45 receives the mixed length measuring lights L2a and L2b as interference light and obtains its intensity, and outputs a signal indicating the time variation of the intensity as a second light receiving signal S2. The second light receiving signal S2 includes a length measuring component derived from the position of the moving reflector 33.

[0089] Examples of the second light receiving element 45 include a photodiode and a phototransistor.

[0090] In the above, the optical elements included in each optical system are described, but it is preferable to perform anti-reflection processing on the optical elements into which light needs to be incident. This can improve the S / N ratio of the first light receiving signal F(t) and the second light receiving signal S2.

[0091] 1.3. Periodic signal generation unit

[0092] Figure 2 The signal generating unit 6 shown generates a periodic signal and outputs it as a reference signal Ss. In the present embodiment, the periodic signal generating unit 6 includes an oscillation circuit 62 .

[0093] As the oscillation circuit 62, for example, the oscillation circuit disclosed in Japanese Patent Gazette No. 2022-38156 can be cited. The oscillation circuit 62 operates the vibration element 30 as a signal source to generate a high-precision periodic signal. As a result, the oscillation circuit 62 outputs a high-precision element drive signal Sd and a reference signal Ss. As a result, the element drive signal Sd and the reference signal Ss are affected in the same way when they are interfered with. As a result, the modulation component added by the vibration element 30 driven by the element drive signal Sd and the reference signal Ss are also affected in the same way. Therefore, when the second light receiving signal S2 and the reference signal Ss are provided for the operation in the operation unit 7, the effects of the interference contained in both parties can be offset or reduced during the operation. As a result, in the operation unit 7, even if interfered with, the position of the movable reflector 33 can be obtained with high precision.

[0094] Furthermore, the oscillation circuit disclosed in the above publication uses an inverter IC, but a Colpitts oscillation circuit may be used instead.

[0095] 1.4.Driver

[0096] Figure 1 The driving unit 8 shown in the figure has a motor M and a power conversion unit 862. The motor M generates a rotation output, and the power conversion unit 862 converts the rotation output into a linear motion to drive the moving mirror 33.

[0097] The motor M generates a rotation output in a predetermined rotation direction and rotation speed. Examples of the motor M include a stepping motor, a brushless motor, and an ultrasonic (piezoelectric) motor.

[0098] The power conversion unit 862 converts the rotational output into linear motion. In addition, in the case where the motor M generates a linear output, the power conversion unit 862 can also be omitted. As the power conversion unit 862, for example, a mechanism having various gears and linear guides can be cited. Such a mechanism can easily increase the amount of movement compared to a MEMS (Micro Electro Mechanical Systems) mechanism, for example. Therefore, the wavelength resolution (wave number resolution) of the spectral pattern that can be obtained can be easily improved. In addition, by using a linear guide, the translational performance of the movable reflector 33 can be improved. Translational performance refers to the characteristic of moving in a straight line without changing the posture of the movable reflector 33 as much as possible.

[0099] 1.5. Operation unit

[0100] Figure 2The computing unit 7 shown has a moving mirror position computing unit 72, a light intensity computing unit 74, and a Fourier transform unit 76. The functions performed by these functional units are realized by hardware including a processor, a memory, an external interface, an input unit, a display unit, etc. Specifically, the functions are realized by the processor reading out and executing the program stored in the memory. In addition, these components can communicate with each other through an external bus.

[0101] Examples of the processor include a CPU (Central Processing Unit), a DSP (Digital Signal Processor), etc. In addition, instead of executing software using these processors, a method of implementing the above functions using an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) may be used.

[0102] Examples of the memory include a HDD (Hard Disk Drive), an SSD (Solid State Drive), an EEPROM (Electrically Erasable Programmable Read-Only Memory), a ROM (Read-Only Memory), and a RAM (Random Access Memory).

[0103] Examples of the external interface include a digital input / output port such as a USB (Universal Serial Bus) port and an Ethernet (registered trademark) port.

[0104] As the input unit, for example, various input devices such as a keyboard, a mouse, a touch panel, and a touch pad can be cited. As the display unit, for example, a liquid crystal display panel, an organic EL (Electro Luminescence) display panel can be cited. In addition, the input unit and the display unit can be provided as needed, and can also be omitted.

[0105] 1.5.1. Mobile mirror position calculation unit

[0106] Figure 2The moving mirror position calculation unit 72 shown determines the position of the moving mirror 33 by using the optical heterodyne interferometry, and generates the moving mirror position signal X(t) based on the result. Specifically, by providing the length measurement optical system 4 with the optical modulator 12, a modulation component can be added to the length measurement light L2a. Moreover, when the length measurement lights L2a and L2b are interfered, the length measurement component derived from the position of the moving mirror 33 can be obtained with high accuracy from the obtained interference light. Moreover, the calculation unit 7 can obtain the moving mirror position signal X(t) with high accuracy based on the length measurement component. According to the optical heterodyne interferometry, when extracting the length measurement component, it is not easily affected by interference, especially the influence of stray light of the frequency that becomes noise, and high robustness can be given.

[0107] Figure 2 The moving mirror position calculation unit 72 shown includes a preprocessing unit 722, a demodulation processing unit 724, and a moving mirror position signal output unit 726. The preprocessing unit 722 and the demodulation processing unit 724 may be the preprocessing unit and the demodulation unit disclosed in Japanese Patent Application Laid-Open No. 2022-38156, for example.

[0108] The preprocessing unit 722 preprocesses the second light receiving signal S2 according to the reference signal Ss. The demodulation processing unit 724 demodulates the length measurement component derived from the position of the movable reflector 33 according to the preprocessed signal output from the preprocessing unit 722 according to the reference signal Ss. That is, the demodulation processing unit 724 demodulates the length measurement component according to the reference signal Ss, which is the periodic signal generated by the periodic signal generating unit 6, and the second light receiving signal S2.

[0109] The moving mirror position signal output unit 726 generates and outputs the moving mirror position signal X(t) based on the length measurement component from the moving mirror 33 demodulated by the demodulation processing unit 724. The moving mirror position signal X(t) obtained by this method is a signal indicating the position of the moving mirror 33 that changes with time, and captures the displacement of the moving mirror 33 at intervals much smaller than the wavelength of the length measurement light L2. For example, when the wavelength of the length measurement light L2 is several hundred nanometers, the position resolution of the moving mirror position signal X(t) can be less than 10 nanometers. Therefore, in the light intensity calculation unit 74, high-precision digital data of the interference pattern F(x) can be generated.

[0110] Figure 5 It means to use Figure 1 FIG. 1 is a diagram showing an example of a first light receiving signal F(t) and a movable mirror position signal X(t) acquired by the spectroscopic apparatus 100 . Figure 5 The horizontal axis represents time t, and the vertical axis represents the intensity of the interference light incident on the first light receiving element 36 or the position of the moving reflection mirror 33 .

[0111] Figure 5The moving mirror position signal X(t) shown is a signal that continuously detects the change in the position of the moving mirror 33 and achieves high position resolution. Therefore, by generating an interference pattern F(x) based on the moving mirror position signal X(t), an interference pattern F(x) with more data points can be obtained. A large number of data points means that the sampling interval of the interference pattern F(x) is short and the accuracy is high. Therefore, by using the interference pattern F(x) obtained in this way, a spectral pattern with high wavelength resolution (wave number resolution) can be finally obtained.

[0112] In addition, since the sampling interval can be shortened, an interference pattern F(x) with a sufficient number of data points can be obtained even when using analysis light L1 with a shorter wavelength (larger wavenumber). As a result, a spectral pattern with a wider wavelength range (wider wavenumber range), that is, a spectral pattern with a wider bandwidth, can be obtained.

[0113] 1.5.2. Light intensity calculation unit

[0114] The light intensity calculation unit 74 generates a waveform (interference pattern F(x)) indicating the intensity of interference light with respect to the position of the movable mirror 33 based on the first light reception signal F(t) and the movable mirror position signal X(t).

[0115] As described above, the first light receiving signal F(t) contains a sample-derived component and phase information from the movable reflector 33. In the light intensity calculation unit 74, the intensity of the first light receiving signal F(t) is extracted based on the movable reflector position signal X(t). Moreover, the light intensity calculation unit 74 generates an interference pattern F(x) based on the position of the movable reflector 33 obtained from the movable reflector position signal X(t) and the intensity of the first light receiving signal F(t). In addition, the interference pattern F(x) is represented by a function of an optical path difference and the intensity of the interference light received by the first light receiving element 36 (the intensity of the first light receiving signal F(t)), wherein the optical path difference is the optical path difference between the reflected light of the movable reflector 33 and the reflected light of the fixed reflector 34 in the analysis optical system 3.

[0116] Figure 6 It is a diagram showing an example of the interference pattern F(x). Figure 6 The horizontal axis is the optical path difference of the analysis optical system 3, and the vertical axis is the intensity of the interference light. In addition, the optical path difference of the analysis optical system 3 refers to the difference between the optical path length between the beam splitter 32 and the movable reflector 33 and the optical path length between the beam splitter 32 and the fixed reflector 34. Figure 6 In the diagram, the optical path difference is zero and is taken as the origin of the horizontal axis.

[0117] 1.5.3. Fourier Transform Section

[0118] The Fourier transform unit 76 performs Fourier transform on the interference pattern F(x), thereby acquiring a spectrum pattern including information specific to the sample 9 .

[0119] Figure 7 This is an example of a spectrum pattern SP0 obtained by spectroscopically analyzing the sample 9. The spectrum pattern SP0 is an example of a reflection spectrum of the sample 9.

[0120] exist Figure 7 In the spectral pattern SP0 shown, the sample-derived component generated by the analytical light L1 acting on the sample 9 is reflected as the absorption peak X9. According to the spectroscopic device 100, the characteristics of the sample 9, such as the material, structure, and component amount, can be analyzed based on the spectral pattern SP0.

[0121] The spectrum pattern SP0 is generated by Fourier transforming the interference pattern F(x). The interference pattern F(x) is an electric field amplitude waveform obtained by taking the position of the movable reflector 33 as a parameter, and therefore the spectrum pattern SP0 obtained by Fourier transforming it has wavelength information. The position of the movable reflector 33 is directly related to the wave number accuracy of the spectrum pattern SP0. Therefore, according to the spectrum device 100 involved in this embodiment, the position of the movable reflector 33 can be more accurately obtained, so that the spectrum pattern SP0 with high accuracy of the wavelength axis (wave number axis) can be generated. In addition, according to this embodiment, the S / N ratio of the interference signal of the analysis light L1a and L1b can be suppressed from decreasing due to the jitter of the movable reflector 33 when the movable reflector 33 moves, so the influence of the jitter of the movable reflector 33 can be suppressed in the spectrum pattern SP0.

[0122] 1.6. Corner Cube Prism

[0123] Figure 8 Yes means Figure 1 A side view of an example of a corner cube prism 330. Fig. 9 It is overlooking Figure 8 A top view of the retroreflective surface 334 is obtained. Figure 8 and Fig. 9 In the figure, arrows are used to indicate the path of the incident light. Fig. 9 The light paths shown are simplified for ease of illustration.

[0124] Figure 8 The corner cube prism 330 shown has an incident surface 332 and a retroreflective surface 334. The incident surface 332 faces the beam splitter 32 and is composed of a flat surface. When light is incident on the incident surface 332, it enters the corner cube prism 330, is reflected by the retroreflective surface 334, and is emitted from the incident surface 332 again. The retroreflective surface 334 includes Fig. 9 The three faces 335, 336, and 337 are shown. These three faces 335, 336, and 337 form the corners of a cube, generating three internal reflections. Thus, the light emitted from the incident face 332 can be returned in the same direction as the incident direction.

[0125] Such a corner cube prism 330 has retroreflectivity not only when the incident angle of light relative to the incident surface 332 is 0°, but also when the incident angle exceeds 0°. In addition, retroreflectivity can be achieved by a single component in the corner cube prism 330. Therefore, by using the corner cube prism 330, simplification, miniaturization, lightness, and cost reduction of the movable reflector 33 can be easily achieved.

[0126] When considering the optical path formed inside the corner cube prism 330, Fig. 9 The three surfaces 335, 336, and 337 shown are respectively divided into two areas. The surface 335 has areas 335a and 335b, the surface 336 has areas 336a and 336b, and the surface 337 has areas 337a and 337b. The light incident on the corner cube 330 is reflected by three of the six areas and emitted. Therefore, three different optical paths are formed in the corner cube 330. For example, after the analysis light L1a is incident from the incident surface 332, it is reflected by the area 335a, the area 336b, and the area 337b, respectively, and passes through the optical path LP1 emitted from the incident surface 332. In addition, after the length measurement light L2b is incident from the incident surface 332, it is reflected by the area 335b, the area 337a, and the area 336a, respectively, and passes through the optical path LP2 emitted from the incident surface 332. By making the analysis light L1a and the length measurement light L2b enter in a manner that they travel along different optical paths, even when both are reflected by the same retroreflective surface 334, the position where the analysis light L1a is reflected can be made different from the position where the length measurement light L2b is reflected. Therefore, it is possible to suppress the analysis light L1a and the length measurement light L2b from being accidentally mixed (mutual leakage of signals). As a result, it is possible to suppress the reduction in the S / N ratio of the interference signal.

[0127] In addition, it is preferred that an anti-reflection film 333 is provided on the incident surface 332 of the corner cube prism 330. As a result, the incident efficiency of the light (analysis light L1a and length measurement light L2b) incident on the incident surface 332 can be improved. In addition, the emission efficiency of the light (analysis light L1a and length measurement light L2b) emitted from the incident surface 332 can also be improved. Furthermore, the generation of reflected stray light in the incident surface 332 can be suppressed, and the generation of noise due to the reflected stray light incident on the first light receiving element 36 can be suppressed. As a result, the reduction in the S / N ratio of the interference signal can be suppressed. As the anti-reflection film 333, for example, a dielectric multilayer film can be cited.

[0128] Corner cube prism 330 may also be configured so that light is totally internally reflected at retroreflective surface 334. Specifically, retroreflective surface 334 may be configured to form an interface with a low refractive index medium such as air so that total internal reflection occurs. Thus, the reflectivity of retroreflective surface 334 may be sufficiently close to 100%, thereby improving the reflection efficiency of corner cube prism 330.

[0129] The corner cube prism 330 may also be configured so that light is specularly reflected at the retroreflective surface 334. Specifically, the retroreflective surface 334 may be configured to be an interface with a high refractive index medium such as a metal so that specular reflection occurs. Thus, the reflectivity can be increased regardless of the incident angle relative to the retroreflective surface 334. In addition, in specular reflection, since there is no polarization dependence of the reflectivity, the loss associated with the polarization dependence of the reflectivity can be suppressed. As the high refractive index medium, metals such as Al, Au, and Ag can be cited, for example.

[0130] Furthermore, the movable mirror 33 has a mounting portion 338 on which the corner cube prism 330 is mounted. Figure 8 The mounting portion 338 shown supports the corner cube prism 330 and is driven by the driving portion 8. That is, the mounting portion 338 only needs to have a function as a slider linearly driven by a linear guide provided in the driving portion 8, and a function as a housing for holding the corner cube prism 330 in the same posture. According to the configuration having such a mounting portion 338, by providing a linear guide of a required length in the driving portion 8, it is possible to ensure that the moving distance of the movable reflector 33 is sufficiently long. As a result, the wavelength resolution (wave number resolution) of the spectrum pattern that can be obtained can be easily improved.

[0131] In the present embodiment, the retroreflective surface 334 is configured to reflect both the analysis light L1a and the length measurement light L2b, but the length measurement light L2b may be reflected by a reflective surface that is provided separately from the retroreflective surface 334 and has no retroreflectivity.

[0132] 2. Modification of the First Embodiment

[0133] Next, a modification of the first embodiment will be described.

[0134] Fig.10 It is a side view showing a retroreflector 331 provided as the movable reflector 33 according to a modification of the first embodiment.

[0135] Hereinafter, a modified example of the first embodiment will be described. However, in the following description, the differences from the first embodiment will be mainly described, and the description of the same matters will be omitted. Fig.10 In the present invention, the same reference numerals are given to the same structures as those in the first embodiment.

[0136] The modification example of the first embodiment is the same as the first embodiment except that a corner reflector 331 is provided instead of the corner cube prism 330 .

[0137] Fig.10The movable reflector 33 shown has a corner reflector 331. The corner reflector 331 is also called a hollow retroreflector and has the same retroreflectivity as the corner cube 330.

[0138] Fig.10 The illustrated corner reflector 331 also has a retroreflective surface 334. The retroreflective surface 334 includes three faces. These three faces form the corners of a cube, generating three-fold specular reflection. Thus, light incident on the retroreflective surface 334 can be returned in the same direction as the incident direction.

[0139] In addition, since there is no incident surface in the corner reflector 331, the loss at the time of incidence and emission can be suppressed. Furthermore, since the light is specularly reflected on the retroreflective surface 334 of the corner reflector 331, there is no polarization dependence of the reflectivity, and the loss accompanying the polarization dependence of the reflectivity can be suppressed. Therefore, by using the corner reflector 331, the reduction of the S / N ratio of the interference signal can be further suppressed.

[0140] The retroreflector 331 may be of a mounted type in which three reflectors are fixed to a mounting member, or a replica type in which a reflector material such as a metal is formed on a replica member having three mutually orthogonal surfaces.

[0141] In the above-described modified examples as well, the same effects as those of the first embodiment can be obtained.

[0142] 3. Second Implementation

[0143] Next, an interferometer according to a second embodiment will be described.

[0144] Fig.11 It is a side view showing corner cubes 330A and 330B provided as the movable reflecting mirror 33 according to the second embodiment.

[0145] The second embodiment will be described below, but in the following description, the differences from the first embodiment will be mainly described, and the description of the same matters will be omitted. Fig.11 In the present invention, the same reference numerals are given to the same items as those in the first embodiment.

[0146] The second embodiment is except Fig.11 Except for the configuration of the movable reflective mirror 33 shown, the present invention is the same as the first embodiment.

[0147] Fig.11 The movable reflector 33 shown has two corner cubes 330A and 330B. The corner cubes 330A and 330B are the same optical elements as the corner cube 330 described above, and have an incident surface 332 and a retroreflective surface 334, respectively.

[0148] The two corner cubes 330A and 330B are arranged along the moving axis of the moving mirror 33 .

[0149] The retroreflective surface 334 of the corner cube prism 330A is also referred to as the "analysis light reflection surface 334A". The analysis light reflection surface 334A is different from the retroreflective surface 334 in the first embodiment, and reflects only the analysis light L1a. In addition, the retroreflective surface 334 of the corner cube prism 330B is also referred to as the "laser reflection surface 334B". The laser reflection surface 334B reflects only the length measurement light L2b. Therefore, in Fig.11 In the movable reflector 33 shown, the optical path of the analysis light L1a and the optical path of the length measurement light L2b are separated, so that the analysis light L1a and the length measurement light L2b can be prevented from being accidentally mixed. In addition, since the optical path adjustment for preventing the analysis light L1a and the length measurement light L2b from mixing is not required, the difficulty of assembling the analysis optical system 3 can be reduced.

[0150] In addition, Fig.11 In the movable reflector 33 shown, the analysis light reflecting surface 334A and the laser light reflecting surface 334B are arranged so as to face opposite directions to each other, and are placed on the placing portion 338. Thus, even without an optical element for making the length measuring light L2b detour, specifically, the optical path changing reflectors 441 to 444 of the first embodiment, the length measuring light L2b can be reasonably incident on the movable reflector 33. As a result, the configuration of the spectroscopic device 100 can be easily simplified.

[0151] Fig.11 The mounting portion 338 shown includes a component that integrates the corner cube prisms 330A and 330B. Thus, the corner cube prisms 330A and 330B can be driven in an integrated manner. As a result, the movement of the corner cube prism 330A can be detected with high accuracy by the reflection of the length measurement light L2b in the corner cube prism 330B, thereby further improving the accuracy of the final analysis result.

[0152] In the second embodiment as described above, the same effects as those of the first embodiment can be obtained.

[0153] In addition, in the present embodiment, the laser reflection surface 334B has retroreflectivity, but the laser reflection surface 334B does not need to have retroreflectivity. In this case, the above-mentioned effect can also be obtained in the analysis optical system 3. On the other hand, by making the laser reflection surface 334B retroreflective as in the present embodiment, the S / N ratio of the interference signal of the length measuring light L2a and L2b can be suppressed from decreasing due to the jitter when the movable reflection mirror 33 moves. As a result, the position of the movable reflection mirror 33 can be detected with higher accuracy.

[0154] 4. Modification of the Second Embodiment

[0155] Next, a modification of the second embodiment will be described.

[0156] Fig.12 It is a side view showing retroreflectors 331A and 331B provided as the movable reflector 33 according to a modification of the second embodiment.

[0157] Hereinafter, a modified example of the second embodiment will be described. However, in the following description, the differences from the second embodiment will be mainly described, and the description of the same matters will be omitted. Fig.12 In the present invention, the same components as those of the second embodiment are denoted by the same reference numerals.

[0158] The modification example of the second embodiment is the same as the second embodiment except that corner reflectors 331A and 331B are provided instead of the corner cube prisms 330A and 330B.

[0159] Fig.12 The movable reflector 33 shown has corner reflectors 331A and 331B, which also have retroreflective surfaces 334. Light incident on each retroreflective surface 334 can be returned in the same direction as the incident direction.

[0160] Since there is no incident surface in the corner reflectors 331A and 331B, the loss at the time of incidence and emission can be suppressed. Furthermore, since the light is specularly reflected on each retroreflective surface 334, there is no polarization dependence of the reflectivity, and the loss accompanying the polarization dependence of the reflectivity can be suppressed. Therefore, by using the corner reflectors 331A and 331B, the accidental interference between the analysis light L1a and the length measurement light L2b can be further suppressed.

[0161] Furthermore, the retroreflectors 331A and 331B may be of a mounting type, a replica type, or the like.

[0162] In the above-described modified examples as well, the same effects as those of the second embodiment can be obtained.

[0163] 5. Third Implementation

[0164] Next, an interferometer according to a third embodiment will be described.

[0165] Fig.13 1 is a diagram schematically showing the configuration of a spectroscopic apparatus 100 as an interferometer according to the third embodiment.

[0166] The third embodiment will be described below. However, in the following description, the differences from the first embodiment will be mainly described, and the description of the same matters will be omitted. Fig.13In the present invention, the same reference numerals are given to the same structures as those in the first embodiment.

[0167] The third embodiment is the same as the first embodiment except that the periodic signal generating unit 6 and the driving unit 8 have different structures. Specifically, in the third embodiment, the periodic signal generating unit 6 outputs not only the reference signal Ss but also the reflector driving signal Sm (reflector driving signal) for driving the motor M of the driving unit 8. Thus, there is no need to generate the periodic signal generating unit required for the reflector driving signal Sm. In other words, the vibration element 30 is used not only as the signal source of the reference signal Ss but also as the signal source of the reflector driving signal Sm. As a result, the structure can be simplified, and the spectral device 100 can be miniaturized, lightweight, low-power, and low-cost.

[0168] Fig.13 The periodic signal generating unit 6 shown has an oscillating circuit 62 and a rectangular wave generating circuit 64. The rectangular wave generating circuit 64 converts the reference signal Ss, which is an analog signal, output from the oscillating circuit 62, into a pulse signal Sp, which is a digital signal. As the rectangular wave generating circuit 64, for example, an analog / digital conversion circuit using a comparator can be cited.

[0169] Fig.13 The driving unit 8 shown in the figure has a motor M, a power conversion unit 862, and a mirror drive signal generating unit 82. The mirror drive signal generating unit 82 generates a mirror drive signal Sm of a target drive frequency according to the pulse signal Sp input from the periodic signal generating unit 6. Then, the mirror drive signal Sm is output to the stepping motor SPM to drive the moving mirror 33 via the power conversion unit 862.

[0170] In the third embodiment as described above, the same effects as those of the first embodiment can be obtained.

[0171] 6. Fourth Implementation

[0172] Next, an interferometer according to a fourth embodiment will be described.

[0173] Fig.14 1 is a diagram schematically showing the configuration of a spectroscopic device 200 as an interferometer according to the fourth embodiment. Fig.15 Yes means Fig.14 A schematic diagram of the main components of the analysis unit 300, the length measurement unit 400, the periodic signal generation unit 6 and the calculation unit 7.

[0174] The fourth embodiment will be described below. However, in the following description, the differences from the first embodiment will be mainly described, and the description of the same matters will be omitted. Fig.14 and Fig.15In the present invention, the same reference numerals are given to the same items as those in the first embodiment.

[0175] The spectroscopic device 100 according to the first embodiment is a device for irradiating the sample 9 with the analysis light L1 emitted from the first light source 51 to perform spectroscopic analysis of the sample 9. In contrast, the shape measuring device 200 according to the fourth embodiment is a device for irradiating the sample 9 with the analysis light L1 to perform shape measurement of the surface or the inside of the sample 9. In addition to the difference in the configuration of the analysis optical system 3, Fig.14 The shape measuring device 200 shown is Figure 1 The spectroscopy devices 100 shown are identical.

[0176] Fig.14 The illustrated analysis optical system 3 includes a first light source 51 , a beam splitter 32 , a movable mirror 33 , a condenser lens 35 , a condenser lens 37 , and a first light receiving element 36 .

[0177] Fig.14 The first light source 51 shown may be a white light source such as SLD (Super Luminescent Diode) or LED (Light Emitting Diode), a wavelength scanning light source, or various lamps listed in the first embodiment. A broadband light source called a low coherence light source is preferably used.

[0178] The analysis light L1 emitted from the first light source 51 is split into two by the beam splitter 32 . Fig.14 The beam splitter 32 reflects part of the analysis light L1 as analysis light L1a toward the movable mirror 33 and transmits the other part of the analysis light L1 as analysis light L1b toward the sample 9. The analysis light L1b is condensed by the condenser lens 37 and irradiated onto the sample 9.

[0179] The beam splitter 32 transmits the analysis light L1a reflected by the movable mirror 33 toward the first light receiving element 36, and reflects the analysis light L1b reflected by the sample 9 toward the first light receiving element 36. Therefore, the beam splitter 32 mixes the split analysis lights L1a and L1b to form interference light.

[0180] The first light receiving element 36 receives the interference light and obtains its intensity. Furthermore, a signal indicating the time variation of the intensity is output as a first light receiving signal F(t). The first light receiving signal F(t) includes a sample-derived component generated by the interaction between the analysis light L1b and the sample 9 and phase information derived from the aforementioned moving reflector 33. The sample-derived component is, for example, a change in the phase of the analysis light L1b added to the surface shape of the sample 9.

[0181] As the first light receiving element 36, for example, in addition to a photodiode, a phototransistor, etc., an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) can also be cited. By using an image sensor, a two-dimensional distribution of the first light receiving signal F(t) can be obtained. Thus, the surface shape of the sample 9 can be measured two-dimensionally.

[0182] Fig.14 The length measuring optical system 4, the periodic signal generating unit 6 and the driving unit 8 are shown in FIG. Figure 1 same. Fig.15 The calculation unit 7 shown includes a moving mirror position calculation unit 72 , a light intensity calculation unit 74 , and a shape calculation unit 78 .

[0183] Fig.15 The light intensity calculation unit 74 shown generates a waveform (interference pattern F(x)) indicating the intensity of the first light reception signal F(t) at each position of the movable mirror 33 based on the first light reception signal F(t) and the movable mirror position signal X(t), similarly to the first embodiment. Fig.15 The shape calculation unit 78 shown calculates the surface shape of the sample 9 based on the waveform. Specific analysis methods are known by names such as white interferometry and time-domain OCT (Optical Coherence Tomography).

[0184] In addition, Fig.14 , the sample 9 reflects the analysis light L1b, but when the sample 9 transmits the analysis light L1b, Fig.14 The shape measuring device 200 shown can measure the internal shape (internal structure) of the sample 9. A specific analysis method is known by the name of optical coherence tomography, etc.

[0185] In the fourth embodiment as described above, the same effects as those of the first embodiment can be obtained.

[0186] 7. Effects achieved by the above-mentioned embodiments

[0187] The interferometer (spectroscopy device 100 or shape measurement device 200) involved in each of the above-mentioned embodiments includes an analysis optical system 3, a length measurement optical system 4, and a drive unit 8. The analysis optical system 3 includes a movable reflector 33 (retroreflection unit) and a first light receiving element 36. The movable reflector 33 reflects the length measurement light L1a. The first light receiving element 36 receives the analysis lights L1a and L1b and outputs a first light receiving signal. In addition, the analysis optical system 3 irradiates the sample 9 with the analysis light L1 and interferes with the analysis lights L1a and L1b. The length measurement optical system 4 includes a second light source 41 (laser light source), an optical modulator 12, and a second light receiving element 45. The second light source 41 emits the length measurement light L2 (laser). The optical modulator 12 modulates the frequency of the length measurement light L2a using the vibration element 30 and adds a modulation component. The second light receiving element 45 receives the length measuring light L2a and L2b including the length measuring component and the modulation component, and outputs a second light receiving signal S2, wherein the length measuring component is generated by irradiating the length measuring light L2b to the movable reflector 33. The length measuring optical system 4 performs interference of the length measuring light L2a and L2b. The driving unit 8 changes the position of the movable reflector 33.

[0188] According to such a configuration, since the movable reflector 33 has retroreflectivity, it is possible to suppress the S / N ratio of the interference signal of the analysis lights L1a and L1b from decreasing due to the jitter when the movable reflector 33 moves (changes position). In addition, by making the movable reflector 33 retroreflective, it is possible to increase the tolerance of the jitter generated when the movable reflector 33 moves, so that even if the driving accuracy of the driving unit 8 decreases, it is easy to suppress the decrease in the S / N ratio of the interference signal. As a result, it is possible to suppress the enlargement of the driving unit 8, thereby achieving miniaturization, lightness, and cost reduction of the interferometer.

[0189] In the interferometer (spectroscopy device 100 or shape measurement device 200) according to each of the above embodiments, the movable reflector 33 (retroreflection unit) has a retroreflection surface 334 and a placement unit 338. The retroreflection surface 334 has retroreflectivity and reflects the analysis light L1a and the length measurement light L2b (laser light). The placement unit 338 places the retroreflection surface 334 and is driven by the drive unit 8.

[0190] According to such a configuration, it is possible to ensure that the moving distance of the movable reflection mirror 33 is sufficiently long, and thus it is possible to easily improve the wavelength resolution (wave number resolution) of the spectral pattern that can be acquired.

[0191] In the interferometer (spectroscopy device 100 or shape measurement device 200 ) according to each of the above-described embodiments, the position at which the analysis light L1 a is reflected and the position at which the length measurement light L2 b (laser light) is reflected on the retroreflective surface 334 are different.

[0192] According to such a configuration, the interference between the analysis light L1a and the length measurement light L2b can be suppressed. As a result, the decrease in the S / N ratio in the length measurement component and the sample-derived component can be suppressed.

[0193] In the interferometer (spectroscopy device 100 or shape measurement device 200) according to each of the above embodiments, the movable reflector 33 (retroreflection unit) includes an analysis light reflection surface 334A, a laser reflection surface 334B, and a mounting unit 338. The analysis light reflection surface 334A has retroreflectivity and reflects the analysis light L1a. The laser reflection surface 334B reflects the length measurement light L2b (laser). The mounting unit 338 mounts the analysis light reflection surface 334A and the laser reflection surface 334B, and is driven by the driving unit 8.

[0194] According to such a configuration, since the analysis light reflecting surface 334A reflects only the analysis light L1a and the laser reflecting surface 334B reflects only the length measuring light L2b, the optical path of the analysis light L1a and the optical path of the length measuring light L2b can be separated, thereby preventing the analysis light L1a and the length measuring light L2b from being accidentally mixed.

[0195] In the interferometer (spectroscopy device 100 or shape measurement device 200 ) according to each of the above-described embodiments, the laser light reflecting surface 334B has retroreflectivity.

[0196] According to such a configuration, it is possible to suppress a decrease in the S / N ratio of the interference signal of the length measuring lights L2 a and L2 b due to vibration when the movable reflective mirror 33 moves (changes its position).

[0197] In the interferometer (spectroscopy device 100 or shape measurement device 200 ) according to each of the above-described embodiments, the analysis light reflecting surface 334A and the laser light reflecting surface 334B face opposite directions to each other.

[0198] According to such a configuration, even without an optical element for making the length measuring light L2b detour, the length measuring light L2b can be reasonably incident on the moving mirror 33. As a result, the configuration of the interferometer can be easily simplified.

[0199] In the interferometer (spectroscopy device 100 or shape measurement device 200) according to the above embodiments, the driving unit 8 drives the movable mirror 33 (retroreflection unit) according to the mirror driving signal Sm (reflection unit driving signal). In this case, the vibration element 30 may also be the signal source of the mirror driving signal Sm.

[0200] According to such a configuration, the configuration of the interferometer can be simplified, and the size, weight, power consumption, and cost of the interferometer can be reduced.

[0201] In the interferometer (spectroscopy device 100 or shape measurement device 200) involved in each of the above embodiments, the analysis optical system 3 includes a beam splitter 32 (light splitting unit), a movable mirror 33 (retroreflection unit), and a fixed mirror 34 (fixed reflection unit). The beam splitter 32 splits the analysis light L1 into two and mixes the split analysis lights L1a and L1b. The movable mirror 33 reflects one side (analysis light L1a) of the split analysis light L1 toward the beam splitter 32. The fixed mirror 34 reflects the other side (analysis light L1b) of the split analysis light L1 toward the beam splitter 32. In addition, the fixed mirror 34 may also have retroreflectivity.

[0202] According to such a configuration, it is possible to suppress a decrease in the S / N ratio of the interference signal due to an angular deviation (deflection angle) in the arrangement of the fixed reflection mirror 34 .

[0203] In the interferometer (spectroscopy device 100 or shape measurement device 200 ) according to each of the above-described embodiments, the movable mirror 33 (retroreflection unit) may include a corner cube 330 .

[0204] According to such a configuration, retroreflectivity can be imparted to the movable mirror 33 by using one component (corner cube 330 ), and therefore, simplification, miniaturization, weight reduction, and cost reduction of the movable mirror 33 can be easily achieved.

[0205] In the interferometer (spectroscopy device 100 or shape measurement device 200 ) according to each of the above-described embodiments, the movable mirror 33 (retroreflection unit) may include an antireflection film 333 provided on the incident surface 332 of the corner cube 330 .

[0206] According to such a configuration, the incident efficiency of the light (analysis light L1a and length measurement light L2b) incident on the incident surface 332 can be improved. In addition, the emission efficiency of the light (analysis light L1a and length measurement light L2b) emitted from the incident surface 332 can also be improved. Furthermore, the generation of reflected stray light in the incident surface 332 can be suppressed, and the generation of noise due to the reflected stray light incident on the first light receiving element 36 can be suppressed. As a result, the reduction in the S / N ratio of the length measurement component and the sample-derived component can be suppressed.

[0207] In the interferometer (spectroscopy device 100 or shape measurement device 200 ) according to each of the above-described embodiments, the movable mirror 33 (retroreflecting unit) may include a retroreflector 331 .

[0208] According to such a configuration, since the corner reflector 331 does not have an incident surface, the loss during the incident and emission can be suppressed. In addition, since the light is specularly reflected on the retroreflective surface 334 of the corner reflector 331, there is no polarization dependence of the reflectivity, and the loss associated with the polarization dependence of the reflectivity can be suppressed.

[0209] The interferometer of the present invention has been described above based on the illustrated embodiments. However, the interferometer of the present invention is not limited to the above embodiments. The configuration of each part may be replaced by an arbitrary configuration, and any other arbitrary configuration may be added.

[0210] In addition, the interferometer of the present invention may include two or more of the above-mentioned embodiments and their modifications. Furthermore, each functional unit of the interferometer of the present invention may be divided into a plurality of elements, or a plurality of functional units may be integrated into one.

[0211] Furthermore, in each of the above-described embodiments, a Michelson interference optical system is used, but another type of interference optical system may also be used.

[0212] Furthermore, the arrangement of the sample is not limited to the arrangement shown in the figure. The sample-derived component is generated by causing the analysis light to act on the sample, so the sample can be arranged at any position as long as the analysis light emitted from the sample can enter the first light receiving element.

Claims

1. An interferometer, characterized in that: have: An analysis optical system having a retroreflection portion for reflecting analysis light and a first light receiving element, wherein the analysis optical system irradiates the sample with the analysis light and interferes with the analysis light, and the first light receiving element receives the analysis light and outputs a first light receiving signal; A length measuring optical system comprising a laser light source, a light modulator, and a second light receiving element, and performing interference of laser light, wherein the laser light source emits the laser light, the light modulator modulates the frequency of the laser light using a vibration element and adds a modulation component, and the second light receiving element receives the laser light including the length measuring component and the modulation component, and outputs a second light receiving signal, wherein the length measuring component is generated by irradiating the laser light to the retroreflective portion; as well as The driving unit changes the position of the retroreflective unit.

2. The interferometer according to claim 1, wherein: The retroreflective portion has: a retroreflective surface having retroreflectivity and reflecting the analysis light and the laser light; and The placing section places the retroreflective surface and is driven by the driving section.

3. The interferometer according to claim 2, wherein: In the retroreflective surface, a position at which the analysis light is reflected is different from a position at which the laser light is reflected.

4. The interferometer according to claim 1, wherein: The retroreflective portion has: An analysis light reflecting surface having retroreflectivity and reflecting the analysis light; a laser reflecting surface for reflecting the laser; and The placing section places the analysis light reflecting surface and the laser light reflecting surface, and is driven by the driving section.

5. The interferometer according to claim 4, wherein: The laser reflecting surface has retro-reflectivity.

6. The interferometer according to claim 4 or 5, wherein: The analysis light reflecting surface and the laser light reflecting surface face in opposite directions.

7. The interferometer according to claim 1, wherein: The driving unit drives the retro-reflecting unit according to the reflecting unit driving signal, The vibration element is a signal source of the reflection portion driving signal.

8. The interferometer according to claim 1, wherein: The analytical optical system comprises: a light splitting unit that splits the analysis light into two and mixes the split analysis light; The retroreflecting unit reflects one of the divided analysis lights toward the light dividing unit; as well as The reflecting unit is fixed so that the other part of the split analysis light is reflected toward the light splitting unit, The fixed reflective portion has retroreflectivity.

9. The interferometer according to claim 1, wherein: The retroreflective portion includes a corner cube prism.

10. The interferometer according to claim 9, wherein: The retroreflective portion includes an antireflection film provided on an incident surface of the corner cube prism.

11. The interferometer according to claim 1, wherein: The retroreflective portion includes a retroreflector.

Images