Mirror moving mechanism and interferometer

Abstract

To provide a mirror moving mechanism that can prevent the influence of blur when a mirror unit moves, is easily reduced in size, and easily ensure a large movement, and an interferometer comprising such a mirror moving mechanism.SOLUTION: A mirror moving mechanism comprises: a mirror unit that comprises a plurality of optical elements having reflective ability; and a driving unit that drives the mirror unit, which are arranged side by side along a light incident surface. The optical element has a plurality of reflection surfaces, and is configured to develop the reflective ability through a plurality of times of reflection on the reflection surfaces.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a mirror moving mechanism and an interferometer. [Background technology]

[0002] Patent Document 1 discloses an optical module used in spectroscopic analysis, which acquires spectral information about light emitted or absorbed by a sample and analyzes the components of the sample based on that information. This optical module includes a mirror unit, a beam splitter unit, a light input unit, a first photodetector, a second light source, and a second photodetector. The mirror unit includes a movable mirror that moves in a predetermined direction and a fixed mirror that is fixed in position. In this optical module, the beam splitter unit, the movable mirror, and the fixed mirror form an interference optical system into which measurement light and laser light are respectively incident.

[0003] The measurement light incident from the first light source through the measurement object passes through the light incident section and is split by the beam splitter unit. A portion of the split measurement light is reflected by the movable mirror and returns to the beam splitter unit. The remainder of the split measurement light is reflected by the fixed mirror and returns to the beam splitter unit. The portion of the measurement light that returned to the beam splitter unit and the remainder are detected by the first photodetector as interference light.

[0004] Meanwhile, the laser light emitted from the second light source is split by the beam splitter unit. A portion of the split laser light is reflected by the movable mirror and returns to the beam splitter unit. The remainder of the split laser light is reflected by the fixed mirror and returns to the beam splitter unit. The portion of the laser light that returned to the beam splitter unit and the remainder are detected by the second photodetector as interference light.

[0005] In such an optical module, the position of the movable mirror is measured based on the detection result of the interference light of the laser light. Then, spectroscopic analysis of the measurement object is possible based on the measurement result of the position of the movable mirror and the detection result of the interference light of the measurement light. Specifically, by determining the intensity of the measurement light at each position of the movable mirror, a waveform called an interferogram is obtained. By Fourier transforming this interferogram, spectral information about the measurement object can be obtained. Therefore, the optical module described in Patent Document 1 is used in an FTIR (Fourier transform infrared spectroscopic analyzer).

[0006] Patent Document 2 discloses the use of an optical microelectromechanical system (optical MEMS device) in an FTIR spectrometer. The optical MEMS device includes a movable corner cube reflector, a fixed mirror, and a MEMS actuator. The optical MEMS device can realize a large optical path delay (optical path difference), thereby expanding the resolution range of the FTIR spectrometer. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2019 / 009404 [Patent Document 2] Special Publication No. 2012-524295 Summary of the Invention [Problem to be solved by the invention]

[0008] In the optical module described in Patent Document 1, a moving mirror (movable mirror) is driven by an electrostatic actuator. To obtain highly accurate spectral information, it is important that the light incident on and emitted from the moving mirror is not displaced in a direction perpendicular to the propagation direction as the moving mirror is driven; in other words, it is important that there is little blurring. For this reason, there is a need to improve the translational movement of the moving mirror. However, the optical module described in Patent Document 1 does not fully consider the translational movement of the moving mirror, and there is room for further study.

[0009] On the other hand, ensuring a sufficient movement distance of the movable mirror is important because it allows for high wavelength resolution (wavenumber resolution) of the acquired spectral information. However, in order to ensure a sufficient movement distance while increasing the translational ability of the movable mirror, it is necessary to increase the size of the drive unit that moves the movable mirror.

[0010] The optical MEMS device described in Patent Document 2 uses a MEMS actuator. However, the MEMS actuator does not have a sufficient amount of movement. Furthermore, the movable corner cube reflector described in Patent Document 2 is composed of a combination of two moving edges and a fixed mirror. These require a large space, making miniaturization difficult.

[0011] Therefore, the realization of a mirror movement mechanism that can suppress the effects of shaking when the mirror moves, is easy to miniaturize, and can easily ensure a large amount of movement has become an issue. [Means for solving the problem]

[0012] The mirror moving mechanism according to an application example of the present invention includes: a mirror portion including a plurality of retroreflective optical elements arranged along a light incident surface; a driving unit that drives the mirror unit; Equipped with.

[0013] An interferometer according to an application example of the present invention includes: A mirror moving mechanism according to an application example of the present invention; an analytical optical system that outputs information derived from the sample by causing interference of light including light reflected by the mirror unit and light that has passed through the sample; Equipped with. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram showing a spectroscopic device as an interferometer according to a first embodiment. [Figure 2] 2 is a functional block diagram showing the main parts of an analysis unit, a length measurement unit, a periodic signal generation unit, and a calculation unit shown in FIG. 1. FIG. [Figure 3] 2 is a cross-sectional view showing the mirror moving mechanism shown in FIG. 1 (the mirror moving mechanism according to the first embodiment). FIG. [Figure 4] FIG. 4 is a partially enlarged view of FIG. [Figure 5] 4 is a schematic diagram showing the arrangement pattern of triangular pyramidal concave surfaces when the movable mirror shown in FIG. 3 is viewed from the positive side of the X axis. FIG. [Figure 6] 2 is a diagram showing an example of a first received light signal F(t) and a movable mirror position signal X(t) acquired by the spectroscopic device shown in FIG. 1. FIG. [Figure 7] FIG. 10 is a diagram showing an example of an interferogram F(x). [Figure 8] 1 is an example of a spectral pattern SP0 obtained by performing spectroscopic analysis on a sample. [Figure 9] FIG. 4 is a cross-sectional view showing a mirror moving mechanism according to a first modified example of the first embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing a mirror moving mechanism according to a second modified example of the first embodiment. [Figure 11] FIG. 10 is a perspective view showing a mirror moving mechanism according to a second embodiment. [Figure 12] FIG. 10 is a perspective view showing a mirror moving mechanism according to a third embodiment. [Figure 13] FIG. 10 is a perspective view showing a mirror moving mechanism according to a fourth embodiment. [Figure 14] FIG. 10 is a perspective view showing a mirror moving mechanism according to a fourth embodiment. [Figure 15] FIG. 10 is a cross-sectional view showing a mirror moving mechanism according to a fifth embodiment. [Figure 16] 16A and 16B are diagrams schematically showing examples of intensity distributions in a cross section of analytical light with and without the lens portion shown in FIG. 15. [Figure 17] FIG. 13 is a cross-sectional view showing a mirror moving mechanism according to a first modified example of the fifth embodiment. [Figure 18] FIG. 13 is a cross-sectional view showing a mirror moving mechanism according to a second modified example of the fifth embodiment. [Figure 19] FIG. 13 is a cross-sectional view showing a mirror moving mechanism according to a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A mirror moving mechanism and an interferometer according to the present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings.

[0016] 1. First embodiment First, the interferometer according to the first embodiment will be described.

[0017] Fig. 1 is a schematic configuration diagram showing a spectroscopic device 100 as an interferometer according to the first embodiment. Fig. 2 is a functional block diagram showing the main parts of the analyzing unit 300, the length measuring unit 400, the periodic signal generating unit 6, and the calculating unit 7 shown in Fig. 1.

[0018] In the spectroscopic device 100 shown in FIG. 1, analytical light L1 emitted from a first light source 51 is irradiated onto a sample 9, which is an object of examination, and analytical light L1 emitted from the sample 9 passes through a Michelson interference optical system. Then, a movable mirror is moved to change the optical path length inside the interference optical system, and changes in the intensity of the obtained interference light are detected. An interferogram is obtained by performing a calculation on the result. A spectral pattern (spectral information) containing information derived from the sample 9 is obtained by Fourier transforming the obtained interferogram. By selecting the wavelength of the analytical light L1, the spectroscopic device 100 shown in FIG. 1 can be applied to, for example, Fourier-transform infrared spectroscopy (FT-IR), Fourier-near-infrared spectroscopy (FT-NIR), Fourier-visible spectroscopy (FT-VIS), Fourier-ultraviolet spectroscopy (FT-UV), and Fourier-terahertz spectroscopy (FT-THz), etc., on the sample 9.

[0019] As shown in FIG. 1, the spectroscopic device 100 includes an analysis unit 300 having an analysis optical system 3 and a mirror moving mechanism 1 (a mirror moving mechanism according to the first embodiment), a length measurement unit 400 having a length measurement optical system 4, a periodic signal generating unit 6, and a calculation unit 7.

[0020] The analytical optical system 3 irradiates the sample 9 with analytical light L1, and splits and mixes the analytical light L1 to cause interference while changing the optical path length of the analytical light L1 so that sample-derived components originating from the sample 9 can be extracted from the analytical light L1. The length measurement optical system 4 measures changes in the optical path length of the analytical light L1 using measurement light L2, which is a laser beam.

[0021] The periodic signal generating unit 6 outputs a reference signal Ss to the calculating unit 7. The calculating unit 7 calculates a waveform representing the intensity of the interference light relative to the optical path length, i.e., the above-mentioned interferogram, based on the signal representing the intensity of the interference light output from the analytical optical system 3 and the signal representing the change in the optical path length output from the length measuring optical system 4. The calculating unit 7 also performs a Fourier transform on the interferogram to obtain a spectral pattern.

[0022] 1.1.Analysis optical system The analytical optical system 3 includes a first light source 51, a beam splitter 54, a condenser lens 55, and a neutral density filter 56. Note that in the analytical optical system 3, some of these optical elements may be omitted, or other optical elements may be added, or they may be replaced with other optical elements.

[0023] The first light source 51 is a light source that emits, for example, white light, i.e., light comprising a wide range of wavelengths, as the analytical light L1. The wavelength range of the analytical light L1, i.e., the type of the first light source 51, is appropriately selected depending on the purpose of the spectroscopic analysis to be performed on the sample 9. When infrared spectroscopic analysis is performed, examples of the first light source 51 include a halogen lamp, an infrared lamp, and a tungsten lamp. When visible spectroscopic analysis is performed, examples of the first light source 51 include a halogen lamp. When ultraviolet spectroscopic analysis is performed, examples of the first light source 51 include a deuterium lamp and a UV-LED (ultraviolet light-emitting diode).

[0024] By selecting a wavelength of the analytical light L1 that is equal to or greater than 100 nm and less than 760 nm, the spectroscopic device 100 can perform ultraviolet spectroscopic analysis or visible spectroscopic analysis. By selecting a wavelength of the analytical light L1 that is equal to or greater than 760 nm and less than 20 μm, the spectroscopic device 100 can perform infrared spectroscopic analysis or near-infrared spectroscopic analysis. Furthermore, by selecting a wavelength of the analytical light L1 that is equal to or greater than 30 μm and less than 3 mm, the spectroscopic device 100 can perform terahertz spectroscopic analysis.

[0025] The first light source 51 may be provided externally to the spectrometer 100. In this case, it is sufficient that the analytical light L1 emitted from the externally provided first light source 51 is introduced into the spectrometer 100. On the other hand, by providing the spectrometer 100 with the first light source 51 as in this embodiment, the alignment accuracy between the first light source 51 and the beam splitter 54 can be particularly improved, and loss of analytical light L1 due to misalignment can be minimized.

[0026] Furthermore, the first light source 51 may be a laser light source that emits laser light. By using a laser light source as the first light source 51, it is possible to obtain a spectroscopic device 100 that can perform laser excitation spectroscopic analysis of the sample 9, such as Fourier Raman spectroscopic analysis and Fourier fluorescence spectroscopic analysis. In this case, the configuration of the analytical optical system 3 may be changed from the above configuration. As the laser light source, a known light source used for Raman spectroscopy or fluorescence spectroscopy is used.

[0027] The analytical light L1 passes through the beam splitter 54, is collected by the collecting lens 55, and is then irradiated onto the sample 9. The analytical light L1 is reflected by the sample 9 and returns to the beam splitter 54. This enables spectroscopic analysis based on the reflected light emitted from the sample 9, i.e., analysis by reflection spectroscopy. Note that by changing the optical path of the analytical optical system 3, spectroscopic analysis based on the transmitted light that passes through the sample 9, i.e., analysis by transmission spectroscopy, becomes possible.

[0028] For example, a non-polarizing beam splitter is used as the beam splitter 54, but a polarizing beam splitter may also be used, in which case a necessary wave plate may be added as appropriate.

[0029] The condenser lens 55 condenses the analytical light L1 to reduce the spot size of the analytical light L1 irradiated on the sample 9. The condenser lens 55 also 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.

[0030] The analytical light L1 emitted from the sample 9 contains sample-derived components generated by interaction with the sample 9. The sample-derived components are generated by interaction of the analytical light L1 with the sample 9, and examples of such interaction include light absorption, reflection, scattering, and emission of specific wavelengths by the sample 9. The analytical light L1 passes through a condenser lens 55, is reflected by a beam splitter 54, and passes through a neutral density filter 56. The neutral density filter 56 selectively attenuates light of a specific wavelength. This increases the S / N ratio (signal-to-noise ratio) of the sample-derived components, enabling more accurate spectroscopic analysis. An example of the neutral density filter 56 is a notch filter with an optical density (OD value) of 6.0 or higher.

[0031] The analytical optical system 3 also includes a beam splitter 32 (light splitting unit), a fixed mirror 34 (fixed reflecting unit), a condenser lens 35, and a first light receiving element 36, which constitute a Michelson interference optical system. Note that the analytical optical system 3 may omit some of these optical elements, may include optical elements other than these, or may have these optical elements replaced with other optical elements.

[0032] The beam splitter 32 is a non-polarizing beam splitter that splits the analytical light L1 into two analytical lights L1a and L1b. Specifically, the beam splitter 32 splits the analytical light L1 into two by reflecting a part of the analytical light L1 as analytical light L1a toward the movable mirror 33 and transmitting the other part of the analytical light L1 as analytical light L1b toward the fixed mirror 34.

[0033] The beam splitter 32 may be of various types, such as a prism-type element (cube-type element) as shown in Fig. 1, a plate-type element, a stacked-type element, etc. When a plate-type beam splitter 32 is used, wavelength dispersion occurs between the analytical light L1a and the analytical light L1b, so a wavelength dispersion compensation plate may be disposed between the beam splitter 32 and the fixed mirror 34, if necessary.

[0034] Furthermore, the beam splitter 32 transmits the analytical light L1a reflected by the movable mirror 33 toward the first light receiving element 36, and reflects the analytical light L1b reflected by the fixed mirror 34 toward the first light receiving element 36. Thus, the beam splitter 32 mixes the split analytical light L1a and L1b.

[0035] The movable mirror 33 is a mirror that moves in the incident direction of the analytical light L1a incident from the beam splitter 32 and reflects the analytical light L1a. The movable mirror 33 is moved back and forth in the incident direction of the analytical light L1a by a driver 80. The phase of the analytical light L1a reflected by the movable mirror 33 changes depending on the position of the movable mirror 33. As a result, the movable mirror 33 adds phase information derived from the position of the movable mirror 33 to the analytical light L1a. The phase information derived from the position of the movable mirror 33 is a change in phase added to the analytical light L1a depending on the position of the movable mirror 33.

[0036] The movable mirror 33 is incorporated into the mirror moving mechanism 1. The mirror moving mechanism 1 includes the movable mirror 33 (mirror unit) that can move in the incident direction of the analytical light L1a, and a driver 80 that drives the movable mirror 33.

[0037] The movable mirror 33 includes a plurality of optical elements having retroreflectivity arranged along the light incident surface 332. Retroreflectivity refers to the property of reflecting light incident on the light incident surface 332 in a manner that follows the direction of incidence. By having such retroreflectivity, even if the movable mirror 33 shakes while moving, it is possible to suppress the occurrence of an angular deviation (angle of deviation) of the reflected analytical light L1a relative to the direction of incidence. This makes it possible to suppress a decrease in analytical accuracy due to the angular deviation.

[0038] Furthermore, the driver 80 can translate the movable mirror 33 by a desired amount of movement, thereby ensuring a large amount of movement for the movable mirror 33. As a result, a spectrometer 100 (interferometer) with high wavelength resolution (wavenumber resolution) for spectral information can be realized.

[0039] Furthermore, the mirror moving mechanism 1 does not require a large driving device to suppress the angular deviation of the analytical light L1a, and therefore can be easily made smaller. The mirror moving mechanism 1 will be described in detail later.

[0040] The fixed mirror 34 is a mirror whose position is fixed relative to the beam splitter 32 and reflects the analytical light L1b. The analytical light L1b reflected by the fixed mirror 34 is mixed with the analytical light L1a by the beam splitter 32 and received as interference light by the first light-receiving element 36. In the analytical optical system 3, an optical path difference occurs between the optical paths of the analytical light L1a and the analytical light L1b depending on the position of the movable mirror 33. The fixed mirror 34 may be a flat mirror, a corner cube prism, or a corner cube mirror. Among these, using a retroreflective corner cube prism, corner cube mirror, or the like as the fixed mirror 34 can suppress a decrease in the S / N ratio of the interference signal that occurs due to an angular deviation (angle of deviation) in the arrangement of the fixed mirror 34, thereby minimizing the impact on the analysis results.

[0041] The condenser lens 35 condenses the interference light, i.e., the mixed analytical light L1a and L1b, onto 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.

[0042] The first light receiving element 36 receives the interference light and acquires its intensity. Then, a signal indicating the change in intensity over time is output as a first light receiving signal F(t). This first light receiving signal F(t) includes a sample-derived component generated by the interaction between the analytical light L1 and the sample 9, and phase information derived from the position of the movable mirror 33 described above.

[0043] Examples of the first light receiving element 36 include a photodiode, a phototransistor, a photomultiplier tube (PMT), etc. Among these, examples of the photodiode include an InGaAs-based photodiode, a Si-based photodiode, and an avalanche photodiode.

[0044] Furthermore, by using an element capable of acquiring a two-dimensional light intensity distribution as the first light receiving element 36, the spectroscopic device 100 can also be applied to, for example, a white light interferometry measuring device, an optical coherence tomography (OCT) imaging device, and the like.

[0045] 1.2. Length measurement optical system The length measurement 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 half-wave plate 46, a quarter-wave plate 47, a quarter-wave plate 48, an analyzer 49, and optical path changing mirrors 441 and 442. Note that the length measurement optical system 4 may omit some of these optical elements, may include other optical elements, or may replace these optical elements with other optical elements. The length measurement optical system 4 uses optical heterodyne interferometry to output phase information derived from the position of the movable mirror 33 or frequency information derived from the moving speed to the calculation unit 7. In this specification, this information is referred to as a "length measurement component."

[0046] A light source that emits light with a narrow spectral linewidth is preferably used as the second light source 41. Examples of the second light source 41 include gas lasers such as He-Ne lasers and Ar lasers, semiconductor laser elements such as DFB-LDs (Distributed Feedback Laser Diodes), FBG-LDs (Fiber Bragg Grating Laser Diodes), VCSELs (Vertical Cavity Surface Emitting Lasers), and FP-LDs (Fabry-Perot Laser Diodes), and crystal lasers such as YAG (Yttrium Aluminum Garnet).

[0047] It is particularly preferable that the second light source 41 is a semiconductor laser element, which allows the spectroscopic device 100 to be made smaller, lighter, and consume less power.

[0048] The beam splitter 42 is a polarizing beam splitter that transmits P-polarized light and reflects S-polarized light. The half-wave plate 46 is positioned with its optical axis rotated with respect to the polarization axis of the measurement light L2. As a result, when the measurement light L2 passes through the half-wave plate 46, it becomes linearly polarized light containing P-polarized light and S-polarized light, and is split by the beam splitter 42 into two, P-polarized light and S-polarized light.

[0049] The S-polarized measurement light L2a is converted into circularly polarized light by the quarter-wave plate 48 and enters the optical modulator 12. The optical modulator 12 adds a modulation component to the measurement light L2a by reflecting the measurement light L2a. The modulation component is a change in frequency that occurs when the measurement light L2a is reflected by the vibration element 30. The reflected measurement light L2a returns to the beam splitter 42. At this time, the measurement light L2a is converted into P-polarized light by the quarter-wave plate 48.

[0050] On the other hand, measurement light L2b, which is P-polarized light, is converted into circularly polarized light by quarter-wave plate 47 and enters movable mirror 33 via optical path changing mirrors 441 and 442. Measurement light L2b enters the same light incident surface 332 as analytical light L1a and is reflected. As a result, the phase of measurement light L2b changes depending on the position of movable mirror 33. Measurement light L2b reflected by movable mirror 33 returns to beam splitter 42 via optical path changing mirrors 441 and 442.

[0051] In this embodiment, as described above, the analytical light L1a and the measuring light L2b are incident on the same light incident surface 332 of the movable mirror 33. In this case, the phase information added to the analytical light L1a and the phase information added to the measuring light L2b are information derived from the position of the same light incident surface 332. This makes it possible to further enhance the correlation between the two pieces of phase information, thereby improving the accuracy of the ultimately obtained analysis results.

[0052] The movable mirror 33 may be configured so that the measurement light L2b is incident on and reflected from a surface different from the light incident surface 332 on which the analytical light L1a is incident. For example, if the light incident surface 332 is set on the front surface of the movable mirror 33, the measurement light L2b may be configured to be incident on the back surface.

[0053] The beam splitter 42 mixes the measurement light L2a returned from the optical modulator 12 with the measurement light L2b reflected by the movable mirror 33. The mixed measurement light L2a and L2b pass through the analyzer 49 and enter the second light receiving element 45.

[0054] An example of the optical modulator 12 is the optical modulator disclosed in Japanese Patent Application Laid-Open No. 2022-38156. In this embodiment, the optical modulator 12 has a vibration element 30. The vibration element 30 vibrates in response to an element drive signal Sd and reflects the measurement light L2a. This causes the optical modulator 12 to superimpose a modulated component onto the measurement light L2a. Note that the optical modulator 12 may be any optical frequency shifter, and may be, for example, an AOM (acousto-optic modulator) or an EOM (electro-optic modulator).

[0055] Furthermore, when the periodic signal generating section 6 generates the reference signal Ss, the vibration element 30 functions as the vibration source.

[0056] Examples of the vibrating element 30 include a quartz crystal vibrator, a silicon vibrator, and a ceramic vibrator. These vibrators utilize the mechanical resonance phenomenon, and therefore have a high Q value, making it easy to stabilize the natural frequency. This increases the S / N ratio of the modulated component that the optical modulator 12 applies to the measurement light L2a, and also increases the accuracy of the reference signal Ss. As a result, the position of the movable mirror 33 can be determined with high accuracy, and ultimately, a spectroscopic device 100 can be realized that can generate a spectral pattern with high accuracy on the wavelength axis (wavenumber axis).

[0057] Examples of quartz crystal resonators include quartz crystal AT resonators, SC cut quartz crystal resonators, tuning fork quartz crystal resonators, quartz surface acoustic wave elements, etc. The oscillation frequency of a quartz crystal resonator is, for example, about 1 kHz to several hundred MHz.

[0058] A silicon vibrator is a vibrator that includes a single-crystal silicon piece manufactured from a single-crystal silicon substrate using MEMS technology, and a piezoelectric film. MEMS (Micro Electro Mechanical Systems) stands for microelectromechanical systems. Examples of the shape of the single-crystal silicon piece include cantilever beam shapes such as two-legged tuning fork and three-legged tuning fork, and doubly supported beam shapes. The oscillation frequency of a silicon vibrator is, for example, about 1 kHz to several hundred MHz.

[0059] A ceramic vibrator is a vibrator that includes electrodes and piezoelectric ceramic pieces manufactured by baking and hardening piezoelectric ceramics. Examples of piezoelectric ceramics include lead zirconate titanate (PZT) and barium titanate (BTO). The oscillation frequency of a ceramic vibrator is, for example, from several hundred kHz to several tens of MHz.

[0060] The second light receiving element 45 receives the mixed measurement light beams L2a and L2b as interference light, acquires its intensity, and outputs a signal indicating the change in intensity over time as a second light receiving signal S2. This second light receiving signal S2 includes a measurement component derived from the position of the movable mirror 33.

[0061] The second light receiving element 45 may be, for example, a photodiode or a phototransistor.

[0062] The optical components of each optical system have been described above, but it is preferable that the optical components that require light to be incident on are subjected to anti-reflection treatment, which can improve the S / N ratio of the first received light signal F(t) and the second received light signal S2.

[0063] 1.3. Periodic signal generation section 2 generates a periodic signal using the vibration element 30 as a source of oscillation and outputs a reference signal Ss. In this embodiment, the periodic signal generating unit 6 has an oscillation circuit 62 that causes the vibration element 30 to oscillate.

[0064] An example of the oscillator circuit 62 is the oscillator circuit disclosed in Japanese Patent Application Laid-Open Publication No. 2022-38156. The oscillator circuit 62 operates using the vibration element 30 as a signal source to generate a highly accurate periodic signal. This allows the oscillator circuit 62 to output a highly accurate element drive signal Sd and reference signal Ss. Therefore, when the element drive signal Sd and the reference signal Ss are subjected to a disturbance, they are affected in the same way. As a result, the modulation component added via 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 subjected to calculation in the calculation unit 7, the effects of the disturbances contained in both can be canceled out or reduced during the calculation process. As a result, the calculation unit 7 can accurately determine the position of the movable mirror 33 even when subjected to a disturbance.

[0065] The oscillator circuit disclosed in the above publication is a circuit using an inverter IC, but a Colpitts oscillator circuit may be used instead.

[0066] Furthermore, the periodic signal generating section 6 is not particularly limited as long as it has the function of generating a periodic signal, and may be, for example, a signal generator, a function generator, or the like.

[0067] 1.4.Mirror movement mechanism FIG. 3 is a cross-sectional view showing the mirror moving mechanism 1 shown in FIG. 1 (the mirror moving mechanism according to the first embodiment). FIG. 4 is a partially enlarged view of FIG. 3. FIG. 5 is a schematic diagram showing the arrangement pattern of the triangular pyramidal concave surface 381 when the moving mirror 33 shown in FIG. 3 is viewed from the positive side of the X axis. In each drawing of the present application, the X axis, Y axis, and Z axis are set as three mutually orthogonal axes. Each axis is represented by an arrow, with the tip of the arrow designated as "plus" and the base of the arrow designated as "minus." In the following description, for example, the "X axis direction" includes both the positive and negative directions of the X axis. The same applies to the Y axis and Z axis directions. In the following description, the positive side of the Z axis is also referred to as "upper," and the negative side of the Z axis is also referred to as "lower."

[0068] The mirror moving mechanism 1 shown in FIG. The movable mirror 33 has a base material 330 and a plurality of triangular pyramidal concave surfaces 381 (retroreflective optical elements) arranged on the base material 330 along a light incident surface 332 parallel to the YZ plane. The light incident surface 332 refers to a range of a plane intersecting the incident direction of the analytical light L1a, configured to be displaced in the incident direction of the analytical light L1a. By arranging a plurality of triangular pyramidal concave surfaces 381 in such a range, the volume of each triangular pyramidal concave surface 381 can be reduced. This allows the movable mirror 33 to be made smaller and thinner than conventional corner cube mirrors, etc.

[0069] The base material 330 has, for example, a plate shape extending along the YZ plane, and has the rigidity necessary to support the plurality of triangular pyramidal concave surfaces 381. When the base material 330 is driven by the driving unit 80, the plurality of triangular pyramidal concave surfaces 381 can be translated in the X-axis direction with high precision.

[0070] The material of the base material 330 is not particularly limited, but examples thereof include metal materials, ceramic materials, and resin materials.

[0071] 4 can be thought of as the inner surface of a cavity defined by four faces that make up the triangular pyramid. One of the four faces is set parallel to light incident surface 332 and serves as the opening face of the cavity. The remaining three faces are reflective surfaces 382 that are arranged around vertex P, which is located on the negative side of the X-axis from the opening face, to connect the opening face to vertex P.

[0072] In such a triangular pyramidal concave surface 381, the incident analytical light L1a is reflected once by each of the three reflecting surfaces 382, ​​regardless of the angle of incidence. This allows the analytical light L1a to be accurately returned (reflected) in the same direction as the incident direction. As a result, even if the movable mirror 33 is subjected to a vibration component, for example, a component rotating around the Y axis or a component rotating around the Z axis, the analytical light L1a can be reflected in the same direction as the incident direction. This makes it possible to suppress positional deviation when the reflected analytical light L1a interferes with the analytical light L1b, thereby suppressing a decrease in the S / N ratio of the first received light signal F(t).

[0073] The triangular pyramidal concave surface 381 may be replaced by a concave surface having a shape other than a triangular pyramid. Examples of such a replaceable concave surface include a concave surface having multiple reflective surfaces and configured to exhibit retroreflectivity through multiple reflections. Specific examples include concave surfaces that form a quadrangular pyramid or a polygonal pyramid with a larger shape. In this case, the number of reflections is not particularly limited.

[0074] Furthermore, the triangular pyramidal concave surfaces 381 may be formed directly on the base material 330, but in this embodiment, they are formed on the surface of a mirror array sheet 331 (retroreflective sheet) disposed on the base material 330. The mirror array sheet 331 is a sheet having a front surface on which a plurality of triangular pyramidal concave surfaces 381 (retroreflective optical elements) are disposed, and a flat back surface.

[0075] The back surface of mirror array sheet 331 is attached to base material 330. This makes it possible to easily construct movable mirror 33 in which multiple triangular pyramidal concave surfaces 381 are precisely aligned, resulting in a movable mirror 33 that is easy to manufacture. Furthermore, mirror array sheet 331 is widely used for a variety of purposes and is relatively easy to obtain, which also contributes to reducing the cost of movable mirror 33.

[0076] Examples of materials that can be used to form the mirror array sheet 331 include resin materials, silicon materials, metal materials, ceramic materials, and glass materials. Methods for forming the triangular pyramidal concave surface 381 include, for example, cutting, molding, photolithography, and etching. In particular, when a resin material is used, the triangular pyramidal concave surface 381 can be formed relatively easily by a molding method such as imprinting. Furthermore, when an etchable material is used, the triangular pyramidal concave surface 381 can be formed with high precision using photolithography and etching techniques.

[0077] A metal film 383 is formed on the reflecting surface 382. This provides the reflecting surface 382 with good light reflectivity. Examples of materials constituting the metal film 383 include aluminum, nickel, silver, gold, and the like, either as a single element or as an alloy. Furthermore, a dielectric multilayer film or a resin film may be used in combination with the metal film 383. This adds functions such as increasing the reflectivity of the metal film 383 and suppressing deterioration of the metal film 383.

[0078] Furthermore, the reflecting surface 382 described above can reflect the analytical light L1a without transmitting it through a solid such as glass or transparent resin. Therefore, even if the analytical light L1a is white light, optical path differences between wavelengths are unlikely to occur. Therefore, phase changes between wavelengths are suppressed, and the resulting decrease in the S / N ratio of the first received light signal F(t) can be suppressed.

[0079] As shown in Fig. 5, the triangular pyramidal concave surfaces 381 are arranged with almost no gaps along the YZ plane. This minimizes the area without retroreflectivity, thereby sufficiently increasing the reflection efficiency of the triangular pyramidal concave surfaces 381. Note that the arrangement pattern of the triangular pyramidal concave surfaces 381 is not limited to the pattern shown in Fig. 5 and may be any pattern.

[0080] 1 includes a motor M and a power conversion unit 862. The motor M generates a rotational force. The power conversion unit 862 converts the rotational force of the motor M into linear motion, and drives the movable mirror 33 along the incident direction (X-axis direction) of the analytical light L1a relative to the light incident surface 332. This configuration makes it possible to realize a drive unit 80 that can ensure a sufficiently large movement amount of the movable mirror 33.

[0081] The motor M generates a rotational force in a predetermined rotation direction and at a predetermined rotation speed. Examples of the motor M include a stepping motor, a DC motor, and an ultrasonic (piezo) motor.

[0082] Examples of the power conversion unit 862 include a one-axis linear stage, a piezoelectric drive device, and a microactuator using MEMS (Micro Electro Mechanical Systems) technology. In this embodiment, since the movable mirror 33 has retroreflection, the power conversion unit 862 is not required to have excessive translational properties. This allows the power conversion unit 862 to be made smaller, lighter, and less expensive.

[0083] In this embodiment, both the analytical light L1a and the measurement light L2b are incident on the light incident surface 332 of the movable mirror 33. It is preferable that the analytical light L1a and the measurement light L2b are incident at different positions on the light incident surface 332. This prevents the two types of light from being mixed together.

[0084] 1.5. Arithmetic section The calculation unit 7 shown in Figure 2 has a moving mirror position calculation unit 72, a light intensity calculation unit 74, and a Fourier transform unit 76. The functions performed by these functional units are realized by hardware including, for example, a processor, memory, an external interface, an input unit, a display unit, etc. Specifically, the functions are realized by the processor reading and executing a program stored in memory. These components are capable of communicating with each other via an external bus.

[0085] Examples of processors include a CPU (Central Processing Unit), a DSP (Digital Signal Processor), etc. Instead of using these processors to execute software, a system in which an FPGA (Field-Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), etc., realizes the above-mentioned functions may be adopted.

[0086] Examples of memory include HDD (Hard Disk Drive), SSD (Solid State Drive), EEPROM (Electrically Erasable Programmable Read-Only Memory), ROM (Read-Only Memory), and RAM (Random Access Memory).

[0087] Examples of the external interface include a digital input / output port such as a USB (Universal Serial Bus), an Ethernet (registered trademark) port, and the like.

[0088] Examples of the input unit include various input devices such as a keyboard, a mouse, a touch panel, a touch pad, etc. Examples of the display unit include a liquid crystal display panel, an organic EL (Electro Luminescence) display panel, etc. The input unit and the display unit may be provided as needed, and may be omitted.

[0089] 1.5.1. Moving mirror position calculation unit The movable mirror position calculation unit 72 shown in FIG. 2 uses optical heterodyne interferometry to determine the position of the movable mirror 33 and generates a movable mirror position signal X(t) based on the results. Specifically, the length measurement optical system 4 includes an optical modulator 12, which allows a modulation component to be added to the length measurement light L2a. When the length measurement light L2a and L2b are made to interfere with each other, the length measurement component derived from the position of the movable mirror 33 can be obtained with high accuracy from the obtained interference light. The calculation unit 7 can then calculate the movable mirror position signal X(t) with high accuracy based on the length measurement component. Optical heterodyne interferometry provides high robustness when extracting the length measurement component, being less susceptible to the influence of external disturbances, particularly stray light of frequencies that cause noise.

[0090] 2 includes a pre-processing unit 722, a demodulation processing unit 724, and a moving mirror position signal output unit 726. The pre-processing unit 722 and the demodulation processing unit 724 may be, for example, the pre-processing unit and the demodulation unit disclosed in Japanese Patent Application Laid-Open No. 2022-38156.

[0091] The pre-processing unit 722 pre-processes the second received light signal S2 based on the reference signal Ss. The demodulation processing unit 724 demodulates the length measurement component derived from the position of the movable mirror 33 based on the reference signal Ss from the pre-processed signal output from the pre-processing unit 722. In other words, the demodulation processing unit 724 demodulates the length measurement component based on the reference signal Ss, which is a periodic signal generated by the periodic signal generating unit 6, and the second received light signal S2.

[0092] The movable mirror position signal output unit 726 generates and outputs a movable mirror position signal X(t) based on the measurement component derived from the movable mirror 33 demodulated by the demodulation processing unit 724. The movable mirror position signal X(t) obtained in this manner is a signal representing the position of the movable mirror 33, which changes over time, and captures the displacement of the movable mirror 33 at intervals sufficiently narrower than the wavelength of the measurement light L2. For example, when the wavelength of the measurement light L2 is several hundred nanometers, a position resolution of less than 10 nanometers can be achieved for the movable mirror position signal X(t). This allows the light intensity calculation unit 74 to generate highly accurate digital data of the interferogram F(x).

[0093] Fig. 6 is a diagram showing an example of the first light receiving signal F(t) and the movable mirror position signal X(t) acquired by the spectroscopic device 100 shown in Fig. 1. The horizontal axis of Fig. 6 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 movable mirror 33.

[0094] The moving mirror position signal X(t) shown in FIG. 6 is an image of a signal that achieves high position resolution by continuously detecting changes in the position of the moving mirror 33. By generating an interferogram F(x) based on such a moving mirror position signal X(t), an interferogram F(x) with a larger number of data points can be obtained. A larger number of data points means that the sampling interval of the interferogram F(x) is short and the accuracy is high. Therefore, ultimately, a spectral pattern with high wavelength resolution (wavenumber resolution) can be obtained.

[0095] Furthermore, by shortening the sampling interval, it is possible to obtain an interferogram F(x) with a sufficient number of data points even when using analytical light L1 with a shorter wavelength (larger wavenumber), which makes it possible to obtain a spectral pattern over a wider wavelength range (wider wavenumber range), i.e., a broader spectral pattern.

[0096] 1.5.2. Light Intensity Calculation Unit The light intensity calculation unit 74 generates a waveform (interferogram F(x)) that represents the intensity of the interference light relative 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).

[0097] As described above, the first received light signal F(t) contains phase information derived from the sample-derived components and the movable mirror 33. The light intensity calculation unit 74 extracts the intensity of the first received light signal F(t) based on the movable mirror position signal X(t). The light intensity calculation unit 74 then generates an interferogram F(x) based on the position of the movable mirror 33 determined from the movable mirror position signal X(t) and the intensity of the first received light signal F(t). Note that the interferogram F(x) is expressed as a function of the optical path difference between the light reflected by the movable mirror 33 and the light reflected by the fixed mirror 34 in the analytical optical system 3, and the intensity of the interference light received by the first light receiving element 36 (the intensity of the first received light signal F(t)).

[0098] Fig. 7 is a diagram showing an example of an interferogram F(x). The horizontal axis of Fig. 7 represents the optical path difference of the analytical optical system 3, and the vertical axis represents the intensity of the interference light. The optical path difference of the analytical optical system 3 is the difference between the optical path length between the beam splitter 32 and the movable mirror 33 and the optical path length between the beam splitter 32 and the fixed mirror 34. In Fig. 7, the origin of the horizontal axis is set to zero optical path difference.

[0099] 1.5.3.Fourier transform section The Fourier transform unit 76 performs a Fourier transform on the interferogram F(x), thereby obtaining a spectral pattern containing information specific to the sample 9.

[0100] 8 is an example of a spectral pattern SP0 obtained by performing spectroscopic analysis on the sample 9. The spectral pattern SP0 is an example of the reflectance spectrum of the sample 9.

[0101] 8 reflects, as an absorption peak X9, components derived from the sample 9 that are generated when the analytical light L1 acts on the sample 9. The spectroscopic device 100 can analyze the characteristics of the sample 9, such as the material, structure, and amounts of components, based on the spectral pattern SP0.

[0102] This spectral pattern SP0 is generated by Fourier transforming the interferogram F(x). Because the interferogram F(x) is an electric field amplitude waveform obtained using the position of the movable mirror 33 as a parameter, the spectral pattern SP0 obtained by Fourier transforming it contains wavelength information. The position of the movable mirror 33 is directly linked to the wavenumber accuracy of the spectral pattern SP0. Therefore, the spectroscopic device 100 according to this embodiment can more accurately determine the position of the movable mirror 33, thereby generating a spectral pattern SP0 with a high accuracy in the wavelength axis (wavenumber axis). Furthermore, according to this embodiment, it is possible to suppress a decrease in the S / N ratio of the first received light signal F(t) due to shaking during movement of the movable mirror 33.

[0103] 3, the movement of movable mirror 33 includes not only the translation of the entire movable mirror 33 but also the displacement of the portions of light reflecting surface 332 that reflect analytical light L1a and measurement light L2b. Similarly, the driving of movable mirror 33 by driver 80 includes not only the translation of the entire movable mirror 33 but also the displacement of the portions of light reflecting surface 332 that reflect analytical light L1a and measurement light L2b.

[0104] 2. Modification of the First Embodiment Next, a modified example of the first embodiment will be described. In the following description, differences from the first embodiment will be mainly described, and a description of similar points will be omitted.

[0105] Fig. 9 is a cross-sectional view showing a mirror moving mechanism 1 according to a first modified example of the first embodiment. In Fig. 9, the same components as those in the first embodiment are denoted by the same reference numerals.

[0106] The first modified example is similar to the first embodiment, except that the movable mirror 33 includes a protective film 337 that covers the triangular pyramidal concave surface 381. The protective film 337 is formed so as to fill the cavity inside the triangular pyramidal concave surface 381. By providing such a protective film 337, the triangular pyramidal concave surface 381 can be protected from adhesion of foreign matter, oxidation, and the like. This makes it possible to suppress deterioration of the reflection efficiency over time.

[0107] Furthermore, the surface of the protective film 337 on the positive side of the X axis is preferably flat. This increases the incidence efficiency of light incident from the positive side of the X axis. Furthermore, the surface of the protective film 337 may be polished. Polishing suppresses scattering on the surface, further increasing the incidence efficiency.

[0108] The material of the protective film 337 is not particularly limited as long as it is a light-transmitting material, and examples thereof include resin materials and glass materials.

[0109] The protective film 337 may also function as an anti-reflection film, which can further increase the light incidence efficiency.

[0110] Fig. 10 is a cross-sectional view showing a mirror moving mechanism 1 according to a second modified example of the first embodiment. In Fig. 10, the same components as those in the first embodiment are denoted by the same reference numerals.

[0111] The second modified example is similar to the first embodiment except that the mirror array sheet 331 includes a plurality of triangular pyramidal prisms 385 (optical elements having retroreflectivity) instead of the triangular pyramidal concave surface 381 described above.

[0112] The mirror array sheet 331 shown in FIG. 10 includes triangular pyramidal prisms 385, a protective film 337, and an adhesive layer 339. The triangular pyramidal prisms 385 are triangular pyramidal prisms with four faces. One of the four faces is set parallel to the light incident surface 332. The remaining three faces are reflective surfaces 382 arranged around the vertex P. The reflective surface 382 is formed at the interface between the triangular pyramidal prisms 385 and the adhesive layer 339. At this interface, light incident on the interior of the triangular pyramidal prism 385 is internally reflected due to the difference in refractive index between the triangular pyramidal prisms 385 and the adhesive layer 339, which has a lower refractive index.

[0113] In such a triangular pyramidal prism 385, the incident analytical light L1a is internally reflected once by each of the three reflecting surfaces 382, ​​regardless of the angle of incidence. This allows the analytical light L1a to be returned (reflected) in the same direction as the incident direction.

[0114] The triangular pyramidal prism 385 may be replaced with a prism having a shape other than a triangular pyramid. Examples of suitable prisms include prisms with multiple reflective surfaces that are configured to exhibit retroreflectivity through multiple reflections. Specific examples include polygonal pyramidal prisms with a square or larger pyramid shape, and bead-shaped prisms with various spherical shapes such as perfect spheres and ellipsoids. In this case, the number of reflections is not particularly limited. However, from the perspective of retroreflectivity and reflection efficiency, polygonal pyramidal prisms, including the triangular pyramidal prism 385, are preferably used.

[0115] An air layer may be provided instead of the adhesive layer 339. In other words, when the mirror array sheet 331 is attached to the base material 330, the triangular pyramidal prisms 385 may be supported so that an air layer is formed between the triangular pyramidal prisms 385 and the base material 330.

[0116] The material of the triangular pyramidal prism 385 is not particularly limited as long as it is a light-transmitting material, and examples thereof include resin materials and glass materials. In each of the above modifications, the same effects as in the first embodiment can be obtained.

[0117] 3. Second embodiment Next, a mirror moving mechanism according to a second embodiment will be described. FIG. 11 is a perspective view showing the mirror moving mechanism 1 according to the second embodiment.

[0118] The second embodiment will be described below, focusing on the differences from the first embodiment and omitting the description of the similarities. Note that in Fig. 11, the same reference numerals are used to designate the same components as those in the first embodiment.

[0119] The second embodiment is similar to the first embodiment except that the substrate 330 has a spiral surface 333 (helical surface), a mirror array sheet 331 (retroreflective sheet) is arranged on this spiral surface 333, and the drive unit 80 is configured to rotate the movable mirror 33.

[0120] The spiral surface 333 is a spiral surface provided around a central axis AX extending in the X-axis direction. A mirror array sheet 331 is attached to the spiral surface 333.

[0121] A plurality of retroreflective optical elements (not shown) are arranged on the mirror array sheet 331. When the analytical light L1a is irradiated onto the mirror array sheet 331 while the base material 330 is rotated around the central axis AX, the irradiation position is displaced in the X-axis direction as the base material 330 rotates. This allows the optical path length of the analytical light L1a to be changed. In other words, the driver 80 shown in FIG. 11 can drive the movable mirror 33 in the X-axis direction.

[0122] Furthermore, in this embodiment, the shape of the base material 330 converts the rotational force of the motor M into a driving force that displaces the mirror array sheet 331 in the X-axis direction. With this configuration, the power conversion unit 862 can be omitted, and the driving unit 80 can be made smaller, lighter, and less expensive.

[0123] The mirror array sheet 331 is also irradiated with measurement light L2b. This allows the change in the optical path length of the analytical light L1a to be measured. In FIG. 11, for convenience of illustration, the analytical light L1a and measurement light L2b are irradiated along the same optical path, but it is preferable that they are shifted from each other. This also applies to the other figures described below.

[0124] Since the mirror array sheet 331 has retroreflectivity, it can reflect incident light even if the spiral surface 333 is curved or not perpendicular to the X-axis. This makes it possible to reduce the size of the driver 80 and suppress the accompanying decrease in the S / N ratio of the first received light signal F(t) and the second received light signal S2. In the second embodiment as described above, the same effects as in the first embodiment can be obtained.

[0125] 4. Third embodiment Next, a mirror moving mechanism according to a third embodiment will be described. FIG. 12 is a perspective view showing the mirror moving mechanism 1 according to the third embodiment.

[0126] The third embodiment will be described below, focusing on the differences from the second embodiment and omitting the description of the similarities. Note that in Fig. 12, the same reference numerals are used to designate the same components as those in the second embodiment.

[0127] The third embodiment is similar to the second embodiment except that the base material 330 has a spiral surface 334 on which a mirror array sheet 331 (retroreflective sheet) is disposed.

[0128] The spiral surface 334 spreads around a central axis AX that extends in the Y-axis direction intersecting with the X-axis direction. The spiral refers to a shape that, when viewed from above the central axis AX, spreads outward while going around the central axis AX. The mirror array sheet 331 is attached to the spiral surface 334.

[0129] When the mirror array sheet 331 is irradiated with analytical light L1a while the base material 330 is rotated around the central axis AX, the irradiation position is displaced in the X-axis direction as the base material 330 rotates. This makes it possible to change the optical path length of the analytical light L1a. In other words, the driver 80 shown in FIG. 12 can drive the movable mirror 33 in the X-axis direction.

[0130] Since the mirror array sheet 331 has retroreflectivity, it can reflect incident light even if the spiral surface 334 is curved or not perpendicular to the X-axis. This makes it possible to reduce the size of the driver 80 while suppressing the accompanying decrease in the S / N ratio of the first received light signal F(t) and the second received light signal S2. In the third embodiment as described above, the same effects as in the second embodiment can be obtained.

[0131] 5. Fourth embodiment Next, a mirror moving mechanism according to a fourth embodiment will be described. 13 and 14 are perspective views showing the mirror moving mechanism 1 according to the fourth embodiment.

[0132] The fourth embodiment will be described below, focusing on the differences from the first embodiment and omitting a description of the similarities. Note that in Figures 13 and 14, the same reference numerals are used to designate the same components as those in the first embodiment.

[0133] The fourth embodiment is similar to the first embodiment except that the base material 330 is conical and has a mirror array sheet 331 (retroreflective sheet) arranged on its side surface 335, and the drive unit 80 is configured to translate the movable mirror 33 while rotating it.

[0134] A mirror array sheet 331 (retroreflective sheet) is attached to a side surface 335 of a base material 330 shown in Fig. 13. A spiral step is provided around a central axis AX on a side surface 335 of the base material 330 shown in Fig. 14. The mirror array sheet 331 is attached to this step.

[0135] When the mirror array sheet 331 is irradiated with analytical light L1a while the substrate 330 is rotated around the central axis AX and translated along the central axis AX, the irradiation position is displaced in the X-axis direction as the substrate 330 is driven. This makes it possible to change the optical path length of the analytical light L1a. In other words, the driver 80 shown in FIGS. 13 and 14 can drive the movable mirror 33 in the X-axis direction. In the fourth embodiment as described above, the same effects as in the first embodiment can be obtained.

[0136] 6. Fifth embodiment Next, a mirror moving mechanism according to a fifth embodiment will be described. FIG. 15 is a cross-sectional view showing the mirror moving mechanism 1 according to the fifth embodiment.

[0137] The fifth embodiment will be described below, focusing on the differences from the first embodiment and omitting a description of similarities. Note that in Fig. 15, the same reference numerals are used to designate the same components as those in the first embodiment. The fifth embodiment is similar to the first embodiment except that a lens unit 39 is provided.

[0138] 15 has a beam diameter expansion lens 391 that expands the beam diameter of the analytical light L1a. The beam diameter expansion lens 391 is provided at a position facing the light incident surface 332. This allows the analytical light L1a, which has a larger beam diameter than in the first embodiment, to be incident on the mirror array sheet 331. Furthermore, the analytical light L1a reflected by the mirror array sheet 331 returns in a manner that retraces the incident direction, and is then incident on the beam diameter expansion lens 391 and converted into parallel light.

[0139] With this configuration, the analytical light L1a can be affected by a larger number of triangular pyramidal concave surfaces 381 (retroreflective optical elements), thereby reducing the influence of individual differences in the triangular pyramidal concave surfaces 381, manufacturing errors, and blurring of the base material 330 on the analytical light L1a.

[0140] FIG. 16 is a diagram schematically showing an example of the intensity distribution in the cross section of the analytical light L1a depending on whether or not the lens portion 39 shown in FIG. 15 is present.

[0141] FIG. 16(a) is a schematic diagram showing the intensity distribution of the cross section of the analytical light L1a in the absence of the lens unit 39, expressed in shades of gray. The striped lines indicate dark areas formed by the projection of the boundaries between the triangular pyramidal concave surfaces 381. The boundaries between the triangular pyramidal concave surfaces 381 have a reduced reflectance, causing these dark areas. Without the lens unit 39, the number of triangular pyramidal concave surfaces 381 acting on the analytical light L1a is small, so the influence of the dark areas is strongly reflected in the analytical light L1a. When such analytical light L1a interferes with other analytical light L1b, the influence of the fluctuation of the analytical light L1a is likely to be strongly reflected in the interference intensity, which is a problem.

[0142] On the other hand, (b) of Figure 16 is a schematic diagram showing the intensity distribution of the cross section of the analytical light L1a when the lens unit 39 is present, expressed in shading. In Figure 16(b), the lines representing dark areas are thinner than in Figure 16(a). This is because the lens unit 39 expands the light diameter, causing it to be reflected by more triangular pyramidal concave surfaces 381, thereby reducing the influence of the boundaries between the triangular pyramidal concave surfaces 381. When such analytical light L1a interferes with other analytical light L1b, the influence of the blurring of the analytical light L1a is less likely to be reflected in the interference intensity. This solves the above problem.

[0143] The shape of the light diameter expansion lens 391 is not particularly limited as long as it can achieve the function of expanding the light diameter. The lens unit 39 may be configured as a collection of multiple lenses, or may include other optical elements such as mirrors and prisms.

[0144] 15 translates the movable mirror 33 and the lens unit 39 together. This allows the distance between the movable mirror 33 and the lens unit 39 to be maintained constant. As a result, it is possible to prevent changes in the diameter expansion rate of the analytical light L1a, and to suppress the effect on the interference intensity. In the fifth embodiment as described above, the same effects as in the first embodiment can be obtained.

[0145] 7. Modification of the Fifth Embodiment Next, a modified example of the fifth embodiment will be described. In the following explanation, differences from the fifth embodiment will be mainly described, and explanations of similar matters will be omitted. In addition, in FIG. 17, the same reference numerals are used for the same configurations as the fifth embodiment.

[0146] FIG. 17 is a cross-sectional view showing a mirror moving mechanism 1 according to a first modified example of the fifth embodiment. The first modified example is similar to the fifth embodiment except that the lens unit 39 further includes a collimating lens 392 .

[0147] The collimating lens 392 is provided between the beam diameter expansion lens 391 and the movable mirror 33 (mirror portion), and converts the analytical beam L1a, whose beam diameter has been expanded by the beam diameter expansion lens 391 and which is incident on the movable mirror 33, into a collimated beam.

[0148] With this configuration, the irradiation range of the analytical light L1a can be kept constant even when the movable mirror 33 moves. Therefore, it is possible to prevent the number of triangular pyramidal concave surfaces 381 acting on the analytical light L1a from changing as the movable mirror 33 moves.

[0149] Furthermore, the above configuration allows for changes in the distance between the moving mirror 33 and the lens unit 39. Therefore, the mirror moving mechanism 1 shown in FIG. 17 includes a fixed stage 863, and the lens unit 39 is supported by this fixed stage 863.

[0150] According to this configuration, the drive unit 80 does not need to drive the lens unit 39, and therefore the structure of the drive unit 80 can be simplified, made smaller, and made less expensive.

[0151] The shape of the collimating lens 392 is not particularly limited as long as it can achieve the function of collimating the analytical light L1a. The lens unit 39 may be configured as a collection of multiple lenses, or may include other optical elements such as a mirror or a prism.

[0152] FIG. 18 is a cross-sectional view showing a mirror moving mechanism 1 according to a second modified example of the fifth embodiment. The second modified example is similar to the first modified example, except that both the analytical light L1a and the measurement light L2b are incident on the light incident surface 332.

[0153] 18, the analytical light L1a and the measurement light L2b need to be incident on different first and second regions of the light incident surface 332. This makes it possible to suppress a decrease in the S / N ratio (S / N ratio of interference intensity) of each of the first received light signal F(t) and the second received light signal S2, which is caused by the mixture of the analytical light L1a and the measurement light L2b.

[0154] In this case, the parameters such as the shape, size, and arrangement pattern of the triangular pyramidal concave surfaces 381 (retroreflective optical elements) provided in the area (first area) irradiated with the analytical light L1a and the area (second area) irradiated with the measurement light L2b may be the same or different. In the latter case, the parameters can be optimized according to the respective beam diameters of the analytical light L1a and the measurement light L2b. This can further increase the S / N ratio of the second received light signal S2. In each of the above modifications, the same effects as in the fifth embodiment can be obtained.

[0155] 8. Sixth embodiment Next, a mirror moving mechanism according to a sixth embodiment will be described. FIG. 19 is a cross-sectional view showing the mirror moving mechanism 1 according to the sixth embodiment.

[0156] The sixth embodiment will be described below, focusing on the differences from the first embodiment and omitting a description of similarities. Note that in Fig. 19, the same reference numerals are used to designate the same components as those in the first embodiment.

[0157] The sixth embodiment is similar to the first embodiment except that the moving mirror 33 includes a bending type piezoelectric actuator 388 and a mirror array sheet 331 (retroreflective sheet) disposed thereon.

[0158] The bending type piezo actuator 388 has, for example, a rectangular shape, and one end in the longitudinal direction is fixed to the fixing portion 81. In addition, the bending type piezo actuator 388 has a mirror array sheet 331 attached thereto.

[0159] The driving unit 80 has a function of applying a voltage to the bending type piezoelectric actuator 388. When a voltage is applied, the bending type piezoelectric actuator 388 is displaced in the X-axis direction, as shown in Fig. 19. Furthermore, the amount of displacement can be adjusted by adjusting the voltage.

[0160] When the analytical light L1a is irradiated onto the mirror array sheet 331 while changing the voltage applied to the bending-type piezoelectric actuator 388, the irradiation position is displaced in the X-axis direction. This makes it possible to change the optical path length of the analytical light L1a. In other words, the driver 80 shown in FIG. 19 can drive the movable mirror 33 in the X-axis direction.

[0161] In the sixth embodiment as described above, the same effects as in the first embodiment can be obtained, and the structure of the movable mirror 33 can be simplified, made smaller, and made less expensive.

[0162] 9. Effects of the above embodiments The mirror moving mechanism 1 according to each of the above-described embodiments and modifications includes a movable mirror 33 (mirror unit) and a drive unit 80 that drives the movable mirror 33. The movable mirror 33 includes a plurality of optical elements having retroreflectivity that are arranged along a light incident surface 332.

[0163] With this configuration, it is possible to suppress the influence of shaking when the moving mirror 33 moves, and it is possible to realize a mirror moving mechanism 1 that is easy to make compact and can easily ensure a large amount of movement.

[0164] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the optical element having retroreflectivity (such as the triangular pyramidal concave surface 381 or the triangular pyramidal prism 385) has multiple reflecting surfaces 382. This optical element is configured to exhibit retroreflectivity by multiple reflections on the reflecting surfaces 382.

[0165] With this configuration, it is possible to realize an optical element that accurately returns (reflects) incident light in the same direction as the incident direction.

[0166] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the optical element (triangular pyramidal concave surface 381) having retroreflective properties has a metal film 383 formed on a reflecting surface 382. This optical element is configured to reflect light on the surface of the metal film 383.

[0167] With this configuration, the reflecting surface 382 can be given good light reflectivity.

[0168] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the optical element having retroreflectivity has a plurality of triangular pyramidal prisms 385. This optical element is configured to exhibit retroreflectivity by multiple internal reflections by the triangular pyramidal prisms 385.

[0169] With this configuration, an optical element with good retroreflectivity and reflection efficiency can be realized.

[0170] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the moving mirror 33 (mirror portion) includes a protective film 337 that covers the optical element (triangular pyramidal concave surface 381) having retroreflectivity.

[0171] With this configuration, the optical elements can be protected from adhesion of foreign matter, oxidation, etc. This makes it possible to suppress deterioration of reflection efficiency over time.

[0172] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the drive unit 80 includes a motor M and a power conversion unit 862. The motor M generates a rotational force. The power conversion unit 862 converts the rotational force into linear motion and drives the moving mirror 33 (mirror unit) along the direction in which light is incident on the light incident surface 332.

[0173] With this configuration, it is possible to realize a driving section 80 that can ensure a sufficiently large amount of movement of the moving mirror 33.

[0174] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the moving mirror 33 (mirror unit) includes a base material 330 and a mirror array sheet 331 (retroreflective sheet) disposed on the base material 330. The mirror array sheet 331 has a plurality of optical elements with retroreflective properties (triangular pyramidal concave surfaces 381, triangular pyramidal prisms 385, etc.).

[0175] With this configuration, it is possible to easily construct a movable mirror 33 in which multiple triangular pyramidal concave surfaces 381 are precisely aligned, thereby realizing a movable mirror 33 that is easy to manufacture. Furthermore, since mirror array sheets 331 are widely used for a variety of purposes and are relatively easy to obtain, they also contribute to reducing the cost of movable mirror 33.

[0176] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the base material 330 has a spiral surface 333 (helical surface) that is spirally formed around the central axis AX. The mirror array sheet 331 (retroreflective sheet) is disposed on the spiral surface 333. The driver 80 rotates the moving mirror 33 (mirror unit) around the central axis AX as the rotation axis.

[0177] With this configuration, the shape of the spiral surface 333 eliminates the need for a mechanism such as the power conversion unit 862 that converts rotational force into linear motion, making it possible to realize a drive unit 80 that can move the movable mirror 33 while being smaller, lighter, and less expensive.

[0178] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the base material 330 has a spiral surface 334 that forms a spiral shape spreading outward from the central axis AX when viewed from above. The mirror array sheet 331 (retroreflective sheet) is disposed on the spiral surface 334. The driver 80 rotates the moving mirror 33 (mirror unit) around the central axis AX as the rotation axis.

[0179] With this configuration, the shape of the spiral surface 334 eliminates the need for a mechanism such as the power conversion unit 862 that converts rotational force into linear motion, making it possible to realize a drive unit 80 that can move the movable mirror 33 while being smaller, lighter, and less expensive.

[0180] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the base material 330 is conical with a central axis AX. The mirror array sheet 331 (retroreflective sheet) is disposed on a side surface 335 of the conical base material 330. The driving unit 80 rotates the moving mirror 33 about the central axis AX as a rotation axis, while translating the moving mirror 33 (mirror unit) along the central axis AX.

[0181] With this configuration, the conical shape of the side surface 335 of the base material 330 eliminates the need for a mechanism for converting rotational force into linear motion, such as the power conversion unit 862, making it possible to realize a drive unit 80 that can move the movable mirror 33 while achieving miniaturization, weight reduction, and cost reduction.

[0182] The mirror moving mechanism 1 according to each of the above-described embodiments and modifications includes a lens section 39 that is provided at a position opposite to the light incident surface 332 and expands the diameter of light incident on the light incident surface 332 .

[0183] With this configuration, more optical elements can act on the light incident on light incident surface 332. This reduces the influence of individual differences in the optical elements, manufacturing errors, blurring of base material 330, and the like on the light reflected by movable mirror 33.

[0184] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the drive unit 80 drives the moving mirror 33 (mirror unit) and the lens unit 39.

[0185] This configuration makes it possible to maintain a constant distance between the movable mirror 33 and the lens unit 39. As a result, it is possible to suppress changes in the diameter expansion rate of the analytical light L1a, and suppress the influence on the interference intensity.

[0186] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the lens unit 39 has a light diameter expansion lens 391 and a collimating lens 392. The light diameter expansion lens 391 expands the light diameter of light incident on the light incident surface 332. The collimating lens 392 is provided between the light diameter expansion lens 391 and the movable mirror 33 (mirror unit), and collimates the light whose light diameter has been expanded by the light diameter expansion lens 391.

[0187] With this configuration, the light irradiation range can be kept constant even when the movable mirror 33 moves, and therefore, it is possible to prevent the number of optical elements acting on the light from changing as the movable mirror 33 moves.

[0188] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the drive unit 80 drives the moving mirror 33 (mirror unit) but does not drive the lens unit 39.

[0189] With this configuration, the structure of the drive unit 80 can be simplified, made smaller, and made less expensive.

[0190] In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the moving mirror 33 (mirror unit) includes a bending type piezoelectric actuator 388 and a mirror array sheet 331 (retroreflective sheet). The mirror array sheet 331 is disposed on the bending type piezoelectric actuator 388 and includes a plurality of optical elements. The driving unit 80 applies a voltage to the bending type piezoelectric actuator 388.

[0191] With this configuration, the structure of the movable mirror 33 can be simplified, made smaller, and made less expensive.

[0192] The spectrometer 100 as an interferometer according to the embodiment includes a mirror moving mechanism 1 according to each of the embodiments and modifications, and an analytical optical system 3. The analytical optical system 3 outputs information derived from the sample 9 by causing interference between light including light reflected by a movable mirror 33 (mirror portion) and light that has passed through the sample 9.

[0193] This configuration makes it possible to realize a spectrometer 100 (interferometer) that is compact, lightweight, and low-cost. It also makes it possible to suppress the influence of angular deviation (deviation angle) of the movable mirror 33. This makes it possible to realize a spectrometer 100 that can perform, for example, highly accurate spectroscopic analysis.

[0194] The spectroscopic device 100 as an interferometer according to the embodiment further includes a length measurement optical system 4. The length measurement optical system 4 irradiates a movable mirror 33 (mirror portion) with length measurement light L2b (laser light) and detects the displacement of the movable mirror 33 by receiving the reflected length measurement light L2b and analyzing the intensity. The analysis optical system 3 is configured to irradiate a first region (region irradiated with analysis light L1a) of the light incident surface 332 with light, and the length measurement optical system 4 is configured to irradiate a second region (region irradiated with length measurement light L2b) different from the first region of the light incident surface 332 with laser light.

[0195] According to this configuration, it is possible to suppress a decrease in the S / N ratio of the interference intensity that occurs when the analytical light L1a and the measurement light L2b are mixed together.

[0196] The mirror moving mechanism and interferometer of the present invention have been described above based on the illustrated embodiments, but the mirror moving mechanism and interferometer of the present invention are not limited to the above-described embodiments and modifications, and the configuration of each part may be replaced with any component, or any other component may be added.

[0197] The mirror moving mechanism and interferometer of the present invention may also be a combination of two or more of the above-described embodiments and their modifications. Furthermore, each functional unit of the interferometer of the present invention may be divided into multiple elements, or multiple functional units may be integrated into one.

[0198] Furthermore, in each of the above embodiments, a Michelson type interference optical system is used, but other types of interference optical systems may also be used.

[0199] Furthermore, the sample placement is not limited to the illustrated placement. Since the sample-derived components are generated by applying analytical light to the sample, the sample can be placed at any position as long as the analytical light emitted from the sample can be incident on the first light-receiving element. [Explanation of symbols]

[0200] 1...mirror moving mechanism, 3...analysis optical system, 4...length measurement optical system, 6...periodic signal generating unit, 7...calculating unit, 9...sample, 12...optical modulator, 30...oscillating element, 32...beam splitter, 33...moving mirror, 34...fixed mirror, 35...condensing lens, 36...first light receiving element, 39...lens unit, 41...second light source, 42...beam splitter, 45...second light receiving element, 46...half wave plate, 47...quarter wave plate, 48... 1 / 4 wave plate, 49... analyzer, 51... first light source, 54... beam splitter, 55... condenser lens, 56... neutral density filter, 62... oscillator circuit, 72... moving mirror position calculation unit, 74... light intensity calculation unit, 76... Fourier transform unit, 80... drive unit, 81... fixed unit, 100... spectrometer, 300... analysis unit, 330... substrate, 331... mirror array sheet, 332... light incident surface, 333... spiral surface, 334... spiral surface, 3 35...side surface, 337...protective film, 339...adhesive layer, 381...triangular pyramidal concave surface, 382...reflective surface, 383...metal film, 385...triangular pyramidal prism, 388...bending type piezoelectric actuator, 391...light diameter expansion lens, 392...parallelizing lens, 400...length measuring unit, 441...light path changing mirror, 442...light path changing mirror, 722...preprocessing unit, 724...demodulation processing unit, 726...moving mirror position signal output unit, 862 ...power conversion unit, 863...fixed stage, AX...center axis, F(t)...first light receiving signal, F(x)...interferogram, L1...analysis light, L1a...analysis light, L1b...analysis light, L2...length measuring light, L2a...length measuring light, L2b...length measuring light, M...motor, P...vertex, S2...second light receiving signal, SP0...spectral pattern, Sd...element drive signal, Ss...reference signal, X(t)...moving mirror position signal, X9...absorption peak

Claims

1. a mirror portion including a plurality of retroreflective optical elements arranged along a light incident surface; a driving unit that drives the mirror unit; A mirror moving mechanism comprising:

2. The mirror moving mechanism according to claim 1 , wherein the optical element has a plurality of reflective surfaces, and is configured to exhibit the retroreflectivity by multiple reflections on the reflective surfaces.

3. 3. The mirror moving mechanism according to claim 2, wherein the optical element has a metal film formed on the reflecting surface, and is configured to reflect light on the surface of the metal film.

4. 2. The mirror moving mechanism according to claim 1, wherein the optical element has a plurality of prisms and is configured to exhibit the retroreflectivity by multiple internal reflections in the prisms.

5. 5. The mirror moving mechanism according to claim 2, wherein the mirror portion includes a protective film that covers the optical element.

6. The drive unit is A motor that generates rotational force; a power conversion unit that converts the rotational force into a linear motion and drives the mirror unit along the incident direction of light with respect to the light incident surface; 2. The mirror moving mechanism according to claim 1, further comprising:

7. The mirror portion is A substrate; a retroreflective sheet disposed on the substrate and having a plurality of the optical elements; The mirror moving mechanism according to claim 1 , comprising:

8. the substrate has a spiral surface that is spirally formed around a central axis, The retroreflective sheet is disposed on the spiral surface, The mirror moving mechanism according to claim 7 , wherein the drive unit rotates the mirror unit around the central axis as a rotation axis.

9. The substrate has a spiral surface that forms a spiral shape extending outward from the central axis when viewed from above the central axis, The retroreflective sheet is disposed on the spiral surface, The mirror moving mechanism according to claim 7 , wherein the drive unit rotates the mirror unit around the central axis as a rotation axis.

10. The substrate has a conical shape having a central axis, The retroreflective sheet is disposed on a side surface of the cone-shaped substrate, The mirror moving mechanism according to claim 7 , wherein the drive unit translates the mirror unit along the central axis while rotating the mirror unit around the central axis as a rotation axis.

11. 5. The mirror moving mechanism according to claim 1, further comprising a lens portion provided at a position opposite to the light incident surface, for expanding a diameter of light incident on the light incident surface.

12. The mirror moving mechanism according to claim 11 , wherein the drive unit drives the mirror unit and the lens unit.

13. The lens portion is a light diameter expansion lens that expands the light diameter of light incident on the light incident surface; a collimating lens provided between the light diameter expansion lens and the mirror portion, the collimating lens collimating the light whose diameter has been expanded by the light diameter expansion lens; The mirror moving mechanism according to claim 11 , further comprising:

14. The mirror moving mechanism according to claim 13 , wherein the drive unit drives the mirror unit but does not drive the lens unit.

15. The mirror portion is Bending piezo actuator, a retroreflective sheeting having a plurality of the optical elements and disposed on the bending type piezoelectric actuator; Equipped with The mirror moving mechanism according to claim 1 , wherein the driving unit applies a voltage to the bending type piezoelectric actuator.

16. A mirror moving mechanism according to any one of claims 1 to 4; an analytical optical system that outputs information derived from the sample by causing interference of light including light reflected by the mirror unit and light that has passed through the sample; An interferometer comprising:

17. a length measurement optical system that detects a displacement of the mirror portion by irradiating the mirror portion with a laser beam and receiving the reflected laser beam and analyzing the intensity of the reflected laser beam; the analytical optical system is configured to irradiate a first region of the light incident surface with light; 17. The interferometer according to claim 16, wherein the length measurement optical system is configured to irradiate the laser light onto a second area of ​​the light incident surface that is different from the first area.

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