Mirror moving mechanism and interferometer

Abstract

To provide a mirror moving mechanism that can suppress blurring during movement and secure a large amount of movement while achieving size reduction, and to provide an interferometer equipped with such a mirror moving mechanism.SOLUTION: A mirror moving mechanism comprises: a moving mirror including a reflection surface; an internal cylinder which supports the moving mirror on its inner surface and includes a first thread groove on its outer surface extending around a central axis; an external cylinder including a second thread groove on its inner surface that screws with the first thread groove; and a drive unit which moves the internal cylinder in the direction of the central axis by rotating and driving the internal cylinder with the central axis as a rotating axis.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a mirror movement mechanism and an interferometer.

Background Art

[0002] Patent Document 1 discloses an optical module used for spectroscopic analysis that acquires spectral information of light emitted or absorbed by a sample and analyzes components in the sample based on the acquired information. This optical module includes a mirror unit, a beam splitter unit, a light incident 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 whose position is fixed. In such an optical module, a beam splitter unit, a movable mirror, and a fixed mirror constitute an interference optical system into which measurement light and laser light are respectively incident.

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

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

[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, based on the measurement result of the position of the movable mirror and the detection result of the interference light of the measurement light, spectroscopic analysis of the measurement target becomes possible. Specifically, by obtaining the intensity of the measurement light at each position of the movable mirror, a waveform called an interferogram is obtained. By performing a Fourier transform on this interferogram, spectral information about the measurement target can be obtained. Therefore, the optical module described in Patent Document 1 is used in an FTIR (Fourier transform infrared spectrometer).

[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. Since the optical MEMS device can achieve a large optical path delay (optical path difference), the resolution range of the FTIR spectrometer can be expanded.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems 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. In order to improve the accuracy of the acquired spectral information, it is important that the light incident on and emitted from the moving mirror does not displace in a direction orthogonal to the propagation direction as the moving mirror is driven. In other words, it is important that the blur is small. For this reason, it is required to enhance the translational property of the movement of the moving mirror. However, in the optical module described in Patent Document 1, the translational property of the moving mirror has not been sufficiently considered and there is room for examination.

[0009] On the other hand, ensuring a sufficient movement amount of the moving mirror is important in terms of being able to increase the wavelength resolution (wavenumber resolution) of the acquired spectral information. However, in order to ensure a sufficient movement amount while enhancing the translational property of the moving mirror, it is necessary to increase the size of the drive unit that moves the moving mirror.

[0010] Also, in the optical MEMS device described in Patent Document 2, an MEMS actuator is used. Although the MEMS actuator is easy to miniaturize, it cannot ensure a sufficient movement amount.

[0011] Therefore, it has become an issue to realize a mirror movement mechanism that can suppress the blur during movement and ensure a large movement amount while suppressing an increase in the size of the drive unit that moves the moving mirror.

Means for Solving the Problem

[0012] The mirror movement mechanism according to an application example of the present invention includes a moving mirror having a reflecting surface, an inner cylinder that supports the moving mirror on its inner surface and has a first thread groove extending around a central axis on its outer surface, an outer cylinder that has a second thread groove engaging with the first thread groove on its inner surface, and a drive unit that moves the inner cylinder in the direction of the central axis by rotationally driving the inner cylinder with the central axis as a rotation axis. and is provided with.

[0013] The interferometer according to the application example of the present invention is a mirror moving mechanism according to the application example of the present invention that reflects the analysis light, and an analysis optical system that outputs a first light reception signal including information derived from the sample by performing interference of light including the analysis light reflected by the mirror moving mechanism and the analysis light that has passed through the sample. It is provided with.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Embodiments for Carrying Out the Invention

[0015] Hereinafter, the mirror movement mechanism and interferometer of the present invention will be described in detail based on 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 apparatus 100 as an interferometer according to the first embodiment. FIG. 2 is a functional block diagram showing each main part of the analysis unit 300, the length measurement unit 400, the periodic signal generation unit 6, and the calculation unit 7 in FIG. 1.

[0018] In the spectroscopic apparatus 100 shown in FIG. 1, the incident analysis light L1 is irradiated onto a sample 9 as a subject, and the analysis light L1 radiated from the sample 9 is passed through a Michelson interferometric optical system. Then, while moving the moving mirror to change the optical path length inside the interferometric optical system, the intensity change of the obtained interference light is detected, and an interferogram is acquired by performing an operation on the result. By performing a Fourier transform on the acquired interferogram, a spectral pattern (spectral information) including information derived from the sample 9 is obtained. By selecting the wavelength of the analysis light L1, the spectroscopic apparatus 100 shown in FIG. 1 is applicable to, for example, FT-IR (Fourier transform infrared spectroscopy), FT-NIR (Fourier transform near-infrared spectroscopy), FT-VIS (Fourier transform visible spectroscopy), FT-UV (Fourier transform ultraviolet spectroscopy), FT-THz (Fourier transform terahertz spectroscopy), etc. for the sample 9.

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

[0020] The analysis optical system 3 irradiates the analysis light L1 onto the sample 9, and while changing the optical path length of the analysis light L1, performs splitting and mixing of the analysis light L1 so as to extract a sample-derived component derived from the sample 9 from the analysis light L1, thereby causing interference. In the length measurement optical system 4, the change in the optical path length of the analysis light L1 is measured using a length measurement light L2 which is a laser beam.

[0021] The periodic signal generation unit 6 outputs a reference signal Ss toward the arithmetic unit 7. The arithmetic unit 7 obtains a waveform representing the intensity of the interference light with respect to the optical path length, that is, the interferogram described above, based on the signal representing the intensity of the interference light output from the analysis optical system 3 and the signal representing the change in the optical path length output from the length measurement optical system 4. Further, the arithmetic unit 7 performs a Fourier transform on the interferogram to obtain a spectral pattern.

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

[0023] The first light source 51 is a light source that emits, as analysis light L1, light that gathers light of a wide wavelength range, for example, white light. The wavelength range 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 performed on the sample 9. When performing infrared spectroscopic analysis, examples of the first light source 51 include a halogen lamp, an infrared lamp, a tungsten lamp, and the like. When performing visible spectroscopic analysis, examples of the first light source 51 include a halogen lamp and the like. When performing ultraviolet spectroscopic analysis, examples of the first light source 51 include a deuterium lamp, a UV-LED (ultraviolet light-emitting diode), and the like.

[0024] Note that by selecting the wavelength of the analysis light L1 to be 100 nm or more and less than 760 nm, a spectroscopic apparatus 100 capable of performing ultraviolet spectroscopic analysis or visible spectroscopic analysis can be realized. Further, by selecting the wavelength of the analysis light L1 to be 760 nm or more and 20 μm or less, a spectroscopic apparatus 100 capable of performing infrared spectroscopic analysis or near-infrared spectroscopic analysis can be realized. Furthermore, by selecting the wavelength of the analysis light L1 to be 30 μm or more and 3 mm or less, a spectroscopic apparatus 100 capable of performing terahertz spectroscopic analysis can be realized.

[0025] Note that the first light source 51 may be provided outside the spectroscopic device 100. In this case, it is sufficient that the analysis light L1 emitted from the first light source 51 provided outside is introduced into the spectroscopic device 100. On the other hand, since the spectroscopic device 100 includes 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 enhanced, and the loss of the analysis light L1 due to alignment failure can be minimized.

[0026] Further, 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, a spectroscopic device 100 capable of realizing laser-excitation spectroscopic analysis such as Fourier-type Raman spectroscopic analysis and Fourier-type fluorescence spectroscopic analysis with respect to the sample 9 can be obtained. In this case, the configuration of the analysis 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 analysis light L1 passes through the beam splitter 54, is condensed by the condenser lens 55, and irradiates the sample 9. In the sample 9, the analysis light L1 is reflected and returns to the beam splitter 54. Thereby, spectroscopic analysis based on the reflected light emitted from the sample 9, that is, analysis by reflection spectroscopy becomes possible. Note that by changing the optical path of the analysis optical system 3, spectroscopic analysis based on the transmitted light that passes through the sample 9, that is, analysis by transmission spectroscopy becomes possible.

[0028] For the beam splitter 54, for example, an unpolarized beam splitter is used, but a polarized beam splitter may be used. In this case, necessary wave plates may be appropriately added.

[0029] The condenser lens 55 condenses the analysis light L1 and reduces the spot size of the analysis light L1 that irradiates the sample 9. Further, the condenser lens 55 condenses the diffused light emitted from the sample 9. Thereby, local analysis becomes possible. If local analysis is not necessary, the condenser lens 55 may be omitted.

[0030] The analysis light L1 emitted from the sample 9 contains sample-derived components generated by the interaction with the sample 9. The sample-derived components are components generated when the analysis light L1 acts on the sample 9, and forms of the action include light absorption, reflection, scattering, luminescence, etc. of a specific wavelength by the sample 9. This analysis light L1 passes through the condenser lens 55, is reflected by the beam splitter 54, and passes through the light attenuation filter 56. The light attenuation filter 56 selectively attenuates light of a predetermined wavelength. Thereby, the S / N ratio (signal-to-noise ratio) of the sample-derived components can be increased, and spectroscopic analysis can be performed with higher accuracy. Examples of the light attenuation filter 56 include a notch filter having an optical density (OD value) of 6.0 or more.

[0031] In addition, the analysis optical system 3 includes a beam splitter 32 (light splitting unit), a fixed mirror 34 (fixed reflection unit), a condenser lens 35, and a first light receiving element 36 that constitute a Michelson interferometric optical system. Note that in the analysis optical system 3, some of these optical elements may be omitted, other optical elements may be provided, or these optical elements may be replaced by other optical elements.

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

[0033] Examples of the type of the beam splitter 32 include, for example, a prism type element (cube type element) shown in FIG. 1, a plate type element, a stacked type element, and the like. When a plate type beam splitter 32 is used, wavelength dispersion occurs between the analysis light L1a and the analysis light L1b. Therefore, a wavelength dispersion compensating plate may be disposed between the beam splitter 32 and the fixed mirror 34 as necessary. The wavelength dispersion compensating plate is an optical element that compensates for wavelength dispersion due to the optical path length difference of the glass material. In the present embodiment, since a prism type element is used as the beam splitter 32, this wavelength dispersion compensating plate is unnecessary. The prism type element is an element in which an optical thin film is sandwiched between prisms. The stacked type element is an element in which an optical thin film is sandwiched between two transparent flat plates. Also in the stacked type element, similar to the prism type element, the wavelength dispersion compensating plate can be made unnecessary. Further, in the prism type element and the stacked type element, since the optical thin film is not exposed, the long-term reliability of the beam splitter 32 can be enhanced.

[0034] 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.

[0035] The movable mirror 33 is a mirror that moves in the incident direction of the analysis light L1a with respect to the beam splitter 32 and reflects the analysis light L1a. The movable mirror 33 is moved by the drive unit 80 so as to reciprocate in the incident direction of the analysis light L1a described above. The analysis light L1a reflected by the movable mirror 33 changes in phase according to the position of the movable mirror 33. Thereby, the movable mirror 33 adds phase information derived from the position of the movable mirror 33 to the analysis light L1a. The phase information derived from the position of the movable mirror 33 is a change in the phase added to the analysis light L1a according to the position of the movable mirror 33.

[0036] The movable mirror 33 is incorporated in the mirror moving mechanism 1. The mirror moving mechanism 1 includes a movable mirror 33 having a reflecting surface 332, an inner cylinder 81 that supports the movable mirror 33, an outer cylinder 83 provided outside the inner cylinder 81, and a drive unit 80 that moves the inner cylinder 81 by rotationally driving the inner cylinder 81.

[0037] According to the mirror moving mechanism 1, the movable mirror 33 can be translated with high precision and at a target moving amount along the incident direction of the analysis light L1a. As a result, when the movable mirror 33 moves, the occurrence of an angular deviation (deflection angle) due to the vibration of the movable mirror 33 is suppressed, and a large moving amount can be ensured. As a result, it is possible to realize a spectroscopic apparatus 100 (interferometer) that can increase the wavelength resolution (wave number resolution) of the spectral information while suppressing the influence of the angular deviation on the analysis result. In addition, the mirror moving mechanism 1 is easy to miniaturize. The mirror moving mechanism 1 will be described in detail later.

[0038] The fixed mirror 34 is a mirror whose position is fixed with respect to the beam splitter 32 and reflects the analysis light L1b. The analysis light L1b reflected by the fixed mirror 34 is mixed with the analysis light L1a by the beam splitter 32 and received by the first light receiving element 36 as interference light. In the analysis optical system 3, an optical path difference occurs 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 mirror 33. The fixed mirror 34 may be a flat mirror, a corner cube prism, or a corner cube mirror. Among these, by using a corner cube prism, a corner cube mirror, etc. having retroreflectivity for the fixed mirror 34, 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 mirror 34 and suppress the influence on the analysis result.

[0039] The condensing lens 35 condenses the interference light, that is, the mixed analysis lights 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 condensing lens 35 may be omitted.

[0040] The first light-receiving element 36 receives the interference light and acquires its intensity. Then, it outputs a signal indicating the temporal change in intensity as the first light-receiving signal F(t). This 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 the phase information derived from the position of the aforementioned movable mirror 33.

[0041] 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, an avalanche photodiode, etc.

[0042] 1.2. Length Measurement Optical System The length measurement optical system 4 is a Michelson interferometric 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, a polarimeter 49, and optical path changing mirrors 441 and 442. Note that in the length measurement optical system 4, some of these optical elements may be omitted, other optical elements may be provided, or these optical elements may be replaced by other optical elements. The length measurement optical system 4 outputs the phase information derived from the position of the movable mirror 33 and the frequency information derived from the moving speed to the arithmetic unit 7 by optical heterodyne interferometry. In this specification, these information are referred to as "length measurement components".

[0043] 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 - Laser Diode), FBG-LD (Fiber Bragg Grating - Laser Diode), VCSEL (Vertical Cavity Surface Emitting Laser), and FP-LD (Fabry-Perot Laser Diode), and crystal lasers such as YAG (Yttrium Aluminum Garnet).

[0044] The second light source 41 is particularly preferably a semiconductor laser element. This makes it possible to reduce the size, weight, and power consumption of the spectroscopic apparatus 100.

[0045] 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 such that its optical axis is rotated with respect to the polarization axis of the length measurement light L2. As a result, when the length measurement light L2 passes through the 1 / 2 wavelength plate 46, it becomes linearly polarized light including P-polarized light and S-polarized light, and is split into two, P-polarized light and S-polarized light, by the beam splitter 42.

[0046] 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 that occurs when the length measurement light L2a is reflected by the vibrating 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.

[0047] On the other hand, the length measurement light L2b, which is P-polarized light, is converted into circularly polarized light by the quarter-wave plate 47 and enters the moving mirror 33 via the optical path changing mirrors 441 and 442. The length measurement light L2b enters the same reflecting surface 332 as the analysis light L1a and is reflected. As a result, the phase of the length measurement light L2b changes according to the position of the moving mirror 33. The length measurement light L2b reflected by the moving mirror 33 returns to the beam splitter 42 via the optical path changing mirrors 441 and 442.

[0048] In the present embodiment, as described above, the analysis light L1a and the length measurement light L2b enter the same reflecting surface 332 of the moving mirror 33. In this case, the phase information added to the analysis light L1a and the phase information added to the length measurement light L2b are information derived from the position of the same reflecting surface 332. Therefore, the correlation between the phase information of both can be enhanced, and the accuracy of the finally obtained analysis result can be improved.

[0049] Further, the beam splitter 42 mixes the length measurement light L2a returned from the optical modulator 12 and the length measurement light L2b reflected by the moving mirror 33. The mixed length measurement lights L2a and L2b pass through the analyzer 49 and enter the second light receiving element 45.

[0050] Examples of the optical modulator 12 include the optical modulator disclosed in Japanese Patent Application Laid-Open No. 2022-38156. In the present embodiment, the optical modulator 12 has a vibrating element 30. The vibrating element 30 vibrates by the element drive 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. Note that the optical modulator 12 may be an optical frequency shifter, for example, an AOM (acousto-optic modulator) or an EOM (electro-optic modulator).

[0051] Examples of the vibration element 30 include a crystal oscillator, a silicon oscillator, a ceramic oscillator, and the like. Since these oscillators utilize a mechanical resonance phenomenon, they have a high Q value and can easily achieve stabilization of the natural frequency. As a result, the S / N ratio of the modulation component applied to the length measurement light L2a by the optical modulator 12 can be increased, and the accuracy of the reference signal Ss can be enhanced. Consequently, the position of the moving mirror 33 can be accurately determined, and ultimately, a spectroscopic apparatus 100 capable of generating a spectral pattern with high accuracy on the wavelength axis (wavenumber axis) can be realized.

[0052] Examples of the crystal oscillator include a crystal AT oscillator, an SC-cut crystal oscillator, a tuning fork type crystal oscillator, a surface acoustic wave element of crystal, and the like. The oscillation frequency of the crystal oscillator is, for example, about 1 kHz to several hundred MHz.

[0053] The silicon oscillator is an oscillator including a single crystal silicon piece manufactured from a single crystal silicon substrate using MEMS technology and a piezoelectric film. MEMS (Micro Electro Mechanical Systems) refers to a micro electro mechanical system. Examples of the shape of the single crystal silicon piece include a cantilever shape such as a two-pronged tuning fork type or a three-pronged tuning fork type, and a double-cantilever shape. The oscillation frequency of the silicon oscillator is, for example, about 1 kHz to several hundred MHz.

[0054] The ceramic oscillator is an oscillator including a piezoelectric ceramic piece manufactured by firing a piezoelectric ceramic and an electrode. Examples of the piezoelectric ceramic include lead zirconate titanate (PZT), barium titanate (BTO), and the like. The oscillation frequency of the ceramic oscillator is, for example, about several hundred kHz to several tens of MHz.

[0055] FIG. 3 is a perspective view showing a configuration example of the vibration element 30 shown in FIG. 1. The vibration element 30 shown in FIG. 3 includes a plate-shaped vibration piece 431 and a diffraction grating 434 provided on the vibration piece 431.

[0056] The vibrating piece 431 is made of a material that repeats a mode of vibrating so as to be distorted in a direction along the surface when a potential is applied. The vibrating piece 431 shown in FIG. 3 is a crystal AT oscillator that performs thickness-shear vibration along the vibration direction 436 in a high-frequency region in the MHz band. Further, a diffraction grating 434 is provided on the surface of the vibrating piece 431. The diffraction grating 434 has grooves 432 having a component intersecting the vibration direction 436, that is, a plurality of linear grooves 432 extending in a direction intersecting the vibration direction 436.

[0057] The vibrating piece 431 has a front surface 4311 and a back surface 4312 that are in a front-back relationship with each other. The diffraction grating 434 is disposed on the front surface 4311. Further, pads 433 for applying a potential to the vibrating piece 431 are provided on the front surface 4311. On the other hand, pads 435 for applying a potential to the vibrating piece 431 are also provided on the back surface 4312.

[0058] The size of the vibrating piece 431 is, for example, such that the long side is about 0.50 mm or more and 10.0 mm or less. Further, the thickness of the vibrating piece 431 is, for example, about 0.10 mm or more and 2.0 mm or less. As an example, the shape of the vibrating piece 431 is a square with one side being 1.6 mm, and its thickness is 0.35 mm.

[0059] The size of the diffraction grating 434 is, for example, such that the long side is about 0.20 mm or more and 3.0 mm or less. Further, the thickness of the diffraction grating 434 is, for example, about 0.003 mm or more and 0.50 mm or less.

[0060] In the present embodiment, the vibrating piece 431 performs thickness-shear vibration. Since this vibration is in-plane vibration as shown by the vibration direction 436 in FIG. 3, light modulation cannot be achieved even when light is incident perpendicularly to the surface of the vibrating piece 431 alone. Therefore, in the vibration element 30, light modulation is enabled by providing the diffraction grating 434 on the vibrating piece 431.

[0061] The diffraction grating 434 shown in FIG. 3 is, as an example, a blazed diffraction grating. A blazed diffraction grating refers to one in which the cross-sectional shape of the diffraction grating is stepped. Note that the shape of the diffraction grating 434 is not limited to this.

[0062] FIG. 4 is a perspective view showing another configuration example of the vibrating element 30 shown in FIG. 1. In FIG. 4, three axes orthogonal to each other, an A-axis, a B-axis, and a C-axis, are set and indicated by arrows. The tip side of the arrow is defined as "plus", and the base side of the arrow is defined as "minus". Also, for example, both directions on the plus side and the minus side of the A-axis are referred to as the "A-axis direction". The same applies to the B-axis direction and the C-axis direction.

[0063] The vibrating element 30 shown in FIG. 4 is a tuning fork type crystal oscillator. The vibrating element 30 shown in FIG. 4 has a vibrating substrate having a base portion 401, a first vibrating arm 402, and a second vibrating arm 403. Since such a tuning fork type crystal oscillator has established manufacturing technology, it is easily available and has stable oscillation. Therefore, the tuning fork type crystal oscillator is suitable as the vibrating element 30. Further, the vibrating element 30 has electrodes 404, 405, and a light reflecting surface 406 provided on the vibrating substrate.

[0064] The base portion 401 is a portion extending along the A-axis. The first vibrating arm 402 is a portion extending from the end portion on the minus side of the A-axis of the base portion 401 toward the plus side of the B-axis. The second vibrating arm 403 is a portion extending from the end portion on the plus side of the A-axis of the base portion 401 toward the plus side of the B-axis.

[0065] The electrode 404 is a conductive film provided on the side surface parallel to the A-B plane among the first vibrating arm 402 and the second vibrating arm 403. Although not shown in FIG. 4, the electrodes 404 are provided on the side surfaces facing each other, and voltages are applied so that the polarities are different from each other to drive the first vibrating arm 402 and the second vibrating arm 403.

[0066] The electrode 405 is a conductive film provided on the side surface of the first vibrating arm 402 and the second vibrating arm 403 that intersects the A-B plane. Although not shown in FIG. 4, the electrodes 405 are also provided on the side surfaces facing each other, and by applying voltages with different polarities to each other, the first vibrating arm 402 and the second vibrating arm 403 are driven.

[0067] The light reflecting surface 406 is set on the side surface of the first vibrating arm 402 and the second vibrating arm 403 that intersects the A-B plane, and has a function of reflecting the length measuring light L2a. The side surface refers to the surface that extends along the extending direction of the first vibrating arm 402 and the second vibrating arm 403. The light reflecting surface 406 shown in FIG. 4 is set on the surface of the first vibrating arm 402, particularly on the surface of the electrode 405. The electrode 405 provided on the first vibrating arm 402 also has a function as the light reflecting surface 406. Note that, separately from the electrode 405, a light reflecting film (not shown) may be provided.

[0068] A crystal piece cut out from a crystal substrate is used for the tuning fork type crystal oscillator. Examples of the crystal substrate used for manufacturing the tuning fork type crystal oscillator include a crystal Z-cut flat plate. In FIG. 4, 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. The crystal Z-cut flat plate is a substrate cut out from a single crystal of crystal such that, for example, the X-axis is the electrical axis, the Y'-axis is the mechanical axis, and the Z'-axis is the optical axis. Specifically, in the orthogonal coordinate system composed of the X-axis, Y'-axis, and Z'-axis, a substrate having a main surface inclined counterclockwise by about 1° to 5° around the X-axis with respect to the X-Y' plane composed of the X-axis and the Y'-axis is cut out from a single crystal of crystal and preferably used as the crystal substrate. Then, by etching such a crystal substrate, the crystal piece used for the vibrating element 30 shown in FIG. 4 is obtained. The etching may be wet etching or dry etching.

[0069] On the other hand, the light reflecting surface 406 may be set on the surface of the electrode 404. In this case, specifically, the signal applied to each electrode may be adjusted so that the tuning fork type crystal oscillator vibrates out of plane, that is, so as to excite a mode of vibrating out of plane (including spurious components).

[0070] The second light receiving element 45 receives the mixed length measurement lights L2a and L2b as interference light and acquires its intensity. Then, a signal indicating the temporal change in intensity is output as the second light receiving signal S2. This second light receiving signal S2 includes a length measurement component derived from the position of the moving mirror 33.

[0071] Examples of the second light receiving element 45 include a photodiode, a phototransistor, and the like.

[0072] As described above, the optical elements included in each optical system have been explained. For the optical elements that need to have light incident thereon, it is preferable that an antireflection treatment is performed. Thereby, the signal-to-noise ratios of the first light receiving signal F(t) and the second light receiving signal S2 can be increased.

[0073] 1.3. Periodic signal generation unit The periodic signal generation unit 6 shown in FIG. 2 generates a periodic signal and outputs it as a reference signal Ss. In the present embodiment, the periodic signal generation unit 6 has an oscillation circuit 62.

[0074] Examples of the oscillation circuit 62 include the oscillation circuit disclosed in Japanese Unexamined Patent Application Publication No. 2022-38156. In the oscillation circuit 62, the vibration element 30 operates as a signal source to generate a highly accurate periodic signal. Thereby, the oscillation circuit 62 outputs a highly accurate element drive signal Sd and a reference signal Ss. Then, when the element drive signal Sd and the reference signal Ss are subject to disturbance, they are affected by the same influence. 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 by the same influence. For this reason, when the second light receiving signal S2 and the reference signal Ss are used in the calculation in the calculation unit 7, in the process of the calculation, the influence of the disturbance included in both can be canceled or reduced with each other. As a result, the calculation unit 7 can accurately obtain the position of the moving mirror 33 even when it is subject to disturbance.

[0075] The oscillation circuit disclosed in the above publication is a circuit using an inverter IC, but a Colpitts oscillation circuit may be used instead.

[0076] In addition, the periodic signal generation unit 6 is not particularly limited as long as it has a function of generating a periodic signal. For example, it may be a signal generator, a function generator, or the like.

[0077] 1.4. Mirror movement mechanism FIG. 5 is a perspective view showing the mirror movement mechanism 1 (mirror movement mechanism according to the first embodiment) shown in FIG. 1. FIG. 6 is a cross-sectional view of the mirror movement mechanism 1 shown in FIG. 5. In each figure of the present application, the X-axis, Y-axis, and Z-axis are set as three axes orthogonal to each other. Each axis is represented by an arrow, and the tip side of the arrow is “plus” and the base end side of the arrow is “minus”. In the following description, for example, the “X-axis direction” includes both the plus direction and the minus direction of the X-axis. The same applies to the Y-axis direction and the Z-axis direction. Further, in the following description, in particular, the Z-axis plus side is also referred to as “up”, and the Z-axis minus side is also referred to as “down”.

[0078] The mirror movement mechanism 1 shown in FIG. 5 includes a movable mirror 33, an inner cylinder 81, an outer cylinder 83, and a drive unit 80. The movable mirror 33 has a reflecting surface 332. As shown in FIG. 6, the inner cylinder 81 supports the movable mirror 33 on the inner surface and has a first screw groove 812 extending around the central axis AX, for example, on the whole or a part of the outer surface. The outer cylinder 83 has a second screw groove 832 on the whole or a part of the inner surface. The first screw groove 812 and the second screw groove 832 are screwed together. The drive unit 80 rotates the inner cylinder 81 with the central axis AX as the rotation axis, thereby screwing the first screw groove 812 into the second screw groove 832 and moving the inner cylinder 81 in the direction of the central axis AX.

[0079] The first thread groove 812 and the second thread groove 832 extend helically around the central axis AX. When such thread grooves are screwed together, the state where the first thread groove 812 and the second thread groove 832 are in contact is maintained over the entire circumference or most parts around the central axis AX. Also, this state is maintained even when the inner cylinder 81 is rotationally driven. Therefore, when the inner cylinder 81 is rotationally driven, the inner cylinder 81 can be moved while minimizing the play between the inner cylinder 81 and the outer cylinder 83. As a result, the translational property of the movement of the moving mirror 33 can be enhanced, and the occurrence of angular deviation (deflection angle) of the moving mirror 33 can be suppressed.

[0080] Also, according to the mirror movement mechanism 1, play during the movement of the moving mirror 33 can be suppressed without using a large guide mechanism or the like. Therefore, a mirror movement mechanism 1 that is easy to miniaturize can be realized. As a result, an interferometer that has been miniaturized, lightened, and cost-reduced can be realized.

[0081] Furthermore, according to the above configuration, for example, compared with a mirror movement mechanism using MEMS (Micro Electro Mechanical Systems), the movement amount of the moving mirror 33 can be easily increased. Therefore, the wavelength resolution (wavenumber resolution) of the spectral pattern that can be obtained in the spectroscopic device 100 (interferometer) can be easily increased.

[0082] The length of the inner cylinder 81 in the direction of the central axis AX is shorter than that of the outer cylinder 83. Therefore, even when the inner cylinder 81 is moved in the X-axis direction by the drive unit 80, the state where the first thread groove 812 and the second thread groove 832 are screwed together is likely to be maintained. Thereby, a sufficient long movement distance of the moving mirror 33 can be ensured.

[0083] Also, it is preferable that the length of the outer cylinder 83 in the direction of the central axis AX is longer than the distance by which the drive unit 80 moves the inner cylinder 81. Thereby, the first thread groove 812 and the second thread groove 832 can be screwed together over the entire range of the movement amount of the moving mirror 33. As a result, the occurrence of deflection angle can be suppressed over the entire range of the movement amount of the moving mirror 33.

[0084] The constituent materials of the inner cylinder 81 and the outer cylinder 83 are not particularly limited, and examples thereof include metal materials, ceramic materials, glass materials, resin materials, and the like. Further, a composite material containing at least one of these materials may also be used. Among these, metal materials are preferably used. Since metal materials have high rigidity and hardness, the translational property of the movement of the moving mirror 33 can be particularly enhanced. Examples of the metal material include stainless steel, aluminum alloy, titanium alloy, and the like.

[0085] The moving mirror 33 shown in FIG. 6 has a substrate 334 and a reflecting surface 332 provided on one surface of the substrate 334. Examples of the substrate 334 include a glass plate, a resin plate, and a metal plate. The reflecting surface 332 may be, for example, the surface of a metal film formed on the substrate 334 or the surface of the substrate 334 that has been mirror-polished. According to such a configuration, after the reflecting surface 332 is provided on the substrate 334 in advance, the moving mirror 33 can be manufactured by the mounting procedure, so that a reflecting surface 332 with high surface accuracy can be obtained. Note that the substrate 334 may be omitted. In that case, the surface of the wall portion 82 or the surface of a metal film or the like formed on the wall portion 82 may be the reflecting surface 332.

[0086] The method of supporting the moving mirror 33 with respect to the wall portion 82 is not particularly limited. For example, the moving mirror 33 is supported on the wall portion 82 via an adhesive or an adhesive sheet.

[0087] Further, the inner surface of the inner cylinder 81 may be subjected to stray light suppression treatment as necessary. Examples of the stray light suppression treatment include anodizing (aluminum oxide) treatment, anti-reflection sheet attachment treatment, and flocked paper attachment treatment. Thereby, the generation of stray light due to specular reflection can be suppressed. As a result, a decrease in the S / N ratio of the interference signal due to stray light can be suppressed.

[0088] The central axis AX extends along the X-axis. The inner cylinder 81 has a cylindrical shape with the central axis AX as its axis. A wall portion 82 that intersects the central axis AX is fixed to the inner surface of the inner cylinder 81. Although the position of the wall portion 82 is not particularly limited as long as it is fixed to the inner surface of the inner cylinder 81, in FIG. 6, it is provided at the middle portion of the inner cylinder 81 in the direction of the central axis AX. The movable mirror 33 is supported by this wall portion 82. According to such a configuration, even when dust is generated due to the screwing together of the first screw groove 812 and the second screw groove 832, it is difficult for the generated dust to adhere to the reflecting surface 332 of the movable mirror 33. That is, since a sufficient distance can be ensured between the end of the inner cylinder 81 in the X-axis direction and the movable mirror 33, the probability of dust generated due to screwing together adhering to the movable mirror 33 can be reduced. Further, since the wall portion 82 is provided at the middle portion of the inner cylinder 81, even if the inner cylinder 81 swings with respect to the outer cylinder 83, specifically, when the inner cylinder 81 swings with the Y-axis as the rotation axis, the unintended displacement width of the reflecting surface 332 can be suppressed. Thereby, a decrease in the S / N ratio of the interference signal due to a decrease in the reflectivity of the reflecting surface 332 or displacement of the reflecting surface 332 due to swinging can be suppressed. Note that the middle portion refers to a range from 40% to 60% of the total length from the end of the inner cylinder 81.

[0089] The outer cylinder 83 shown in FIG. 5 has a window portion 831 that penetrates the outer surface and the inner surface. The outer surface of the inner cylinder 81 can be exposed through the window portion 831.

[0090] In the present embodiment, a first linear groove 814 is provided on the outer surface of the inner cylinder 81. The first linear groove 814 intersects the first screw groove 812. More specifically, the first linear groove 814 extends parallel to the central axis AX. Note that the first linear groove 814 may be inclined with respect to the central axis AX.

[0091] The drive unit 80 shown in Fig. 1 has a motor M and a power conversion unit 862. The motor M generates a rotational output, and the power conversion unit 862 shown in Fig. 5 is composed of a worm gear 863 connected to the output shaft of the motor M, and transmits the rotational output to the inner cylinder 81. Specifically, the worm gear 863 is engaged with a first linear groove 814 exposed from the window portion 831. Thereby, the rotation of the worm gear 863 can be transmitted to the inner cylinder 81. Therefore, the moving mirror 33 can be moved by an arbitrary moving amount corresponding to the rotation amount of the worm gear 863. That is, the drive unit 80 converts the rotational output of the motor M into a translational motion of the moving mirror 33. Further, when the power conversion unit 862 is composed of the worm gear 863, the reduction ratio of the power conversion unit 862 can be increased, and the backlash can be reduced. As a result, since there is no need to add a speed reducer or the like, the drive unit 80 can be easily miniaturized, and the position accuracy of the moving mirror 33 can be easily improved.

[0092] The motor M generates a rotational output at a predetermined rotational direction and rotational speed. Examples of the motor M include a stepping motor, a DC motor, an ultrasonic (piezo) motor, and the like.

[0093] Among these, in the present embodiment, a DC motor is preferably used. Since the DC motor can generate sufficient torque even when it is small, it can contribute to the miniaturization of the mirror moving mechanism 1. Further, examples of the DC motor include a brushed DC motor and a brushless DC motor, and a brushless DC motor is preferably used. Since the rotation speed of the brushless DC motor can be easily controlled based on the applied voltage, the moving speed of the moving mirror 33 can be easily controlled.

[0094] In the present embodiment, as described above, the analysis light L1a and the length measurement light L2b are incident on the reflecting surface 332 of the moving mirror 33. It is preferable that the incident positions of the analysis light L1a and the length measurement light L2b are different from each other. Thereby, it is possible to prevent the two lights from being mixed.

[0095] Also, the incident position of the length measurement light L2b may be set at the intersection of the reflecting surface 332 and the central axis AX. This intersection is less likely to be displaced in the X-axis direction even when the inner cylinder 81 is rotationally driven. That is, even if the reflecting surface 332 is slightly inclined with respect to the central axis AX, the displacement can be suppressed to a small value in the vicinity of the intersection. Also, the length measurement light L2b continues to be irradiated at the same position on the reflecting surface 332. For this reason, compared with the case where the light is irradiated to various positions as the reflecting surface 332 rotates, the possibility that the reflectance unintentionally changes due to dirt or the like is reduced. Therefore, by setting the incident position of the length measurement light L2b at the intersection, it is possible to suppress a decrease in the S / N ratio of the length measurement component due to the displacement of the reflecting surface 332. Note that setting the incident position of the length measurement light L2b at the intersection means a state in which the intersection of the reflecting surface 332 and the central axis AX is included within the irradiation range of the length measurement light L2b.

[0096] The outer cylinder 83 has screw holes 833. The screw holes 833 are used to fix the outer cylinder 83 to a base material or the like (not shown) using screws (not shown). The number of the screw holes 833 is not particularly limited, but preferably three or more in view of stably fixing the outer cylinder 83.

[0097] Note that the configuration of the drive unit 80 is not limited to the above as long as it has a function of rotationally driving the inner cylinder 81 about the central axis AX as the rotation axis.

[0098] 1.5. Arithmetic Unit The arithmetic unit 7 shown in FIG. 2 includes a moving mirror position arithmetic unit 72, a light intensity arithmetic unit 74, and a Fourier transform unit 76. The functions exhibited by these functional units are realized by hardware including, for example, a processor, a memory, an external interface, an input unit, a display unit, and the like. Specifically, it is realized by the processor reading and executing a program stored in the memory. Note that these components can communicate with each other via an external bus.

[0099] Examples of the processor include a CPU (Central Processing Unit), a DSP (Digital Signal Processor), etc. Instead of the above-mentioned processors executing software, a method in which an FPGA (Field-Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), etc. realize the above-mentioned functions may be adopted.

[0100] Examples of the memory include an HDD (Hard Disk Drive), an SSD (Solid State Drive), an EEPROM (Electrically Erasable Programmable Read-Only Memory), a ROM (Read-Only Memory), a RAM (Random Access Memory), etc.

[0101] Examples of the external interface include digital input / output ports such as a USB (Universal Serial Bus), an Ethernet (registered trademark) port, etc.

[0102] 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. Note that the input unit and the display unit may be provided as necessary and may be omitted.

[0103] 1.5.1. Moving Mirror Position Calculation Unit The moving mirror position calculation unit 72 shown in FIG. 2 identifies the position of the moving mirror 33 by the optical heterodyne interference method, and generates a moving mirror position signal X(t) based on the result. Specifically, since the length measurement optical system 4 includes the optical modulator 12, a modulation component can be added to the length measurement light L2a. Then, 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 acquired with high accuracy from the obtained interference light. Then, the calculation unit 7 can accurately obtain the moving mirror position signal X(t) based on the length measurement component. According to the optical heterodyne interference method, when extracting the length measurement component, it is less susceptible to the influence of disturbances, particularly stray light at frequencies that become noise, and high robustness is provided.

[0104] The moving mirror position calculation unit 72 shown in FIG. 2 includes a preprocessing unit 722, a demodulation processing unit 724, and a moving mirror position signal output unit 726. For example, the preprocessing unit and the demodulation unit disclosed in Japanese Patent Application Laid-Open No. 2022-38156 can be applied to the preprocessing unit 722 and the demodulation processing unit 724.

[0105] The preprocessing unit 722 performs preprocessing on the second light reception signal S2 based on the reference signal Ss. The demodulation processing unit 724 demodulates the length measurement component derived from the position of the moving mirror 33 based on the reference signal Ss from the preprocessed signal output from the preprocessing unit 722. That is, the demodulation processing unit 724 demodulates the length measurement component based on the reference signal Ss, which is the periodic signal generated by the periodic signal generation unit 6, and the second light reception signal S2.

[0106] The moving mirror position signal output unit 726 generates and outputs a moving mirror position signal X(t) based on the length measurement component derived from the moving mirror 33 demodulated by the demodulation processing unit 724. The moving mirror position signal X(t) obtained in this way is a signal representing the position of the moving mirror 33 that changes with time, and captures the displacement of the moving mirror 33 at intervals sufficiently narrower than the wavelength of the length measurement light L2. For example, when the wavelength of the length measurement light L2 is several hundred nanometers, a position resolution of less than 10 nm can be achieved as the position resolution of the moving mirror position signal X(t). Therefore, the light intensity calculation unit 74 can generate high-precision digital data of the interferogram F(x).

[0107] FIG. 7 is a diagram showing an example of the first received light signal F(t) and the moving mirror position signal X(t) acquired by the spectroscopic apparatus 100 shown in FIG. 1. The horizontal axis in FIG. 7 is the time t, and the vertical axis is the intensity of the interference light incident on the first light receiving element 36 or the position of the moving mirror 33.

[0108] The moving mirror position signal X(t) shown in FIG. 7 is an image of a signal that continuously detects the change in the position of the moving mirror 33 and realizes high position resolution. By generating the 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. The large number of data points means that the sampling interval of the interferogram F(x) is short and the accuracy is high. Therefore, finally, a spectral pattern with high wavelength resolution (wave number resolution) can be acquired.

[0109] Also, by being able to shorten the sampling interval, even when using analysis light L1 with a shorter wavelength (higher wave number), an interferogram F(x) with a sufficient number of data points can be obtained. As a result, a spectral pattern over a wider wavelength range (wider wave number range), that is, a wider-band spectral pattern can be acquired.

[0110] 1.5.2. Light Intensity Calculation Unit Based on the first received light signal F(t) and the moving mirror position signal X(t), the light intensity calculation unit 74 generates a waveform (interferogram F(x)) representing the intensity of the interference light with respect to the position of the moving mirror 33.

[0111] As described above, the first received light signal F(t) includes phase information derived from the sample-derived component and the moving mirror 33. The light intensity calculation unit 74 extracts the intensity of the first received light signal F(t) based on the moving mirror position signal X(t). Then, the light intensity calculation unit 74 generates the interferogram F(x) based on the position of the moving mirror 33 obtained from the moving mirror position signal X(t) and the intensity of the first received light signal F(t). Note that the interferogram F(x) is represented as a function of the optical path difference between the reflected light from the moving mirror 33 and the reflected light from the fixed mirror 34 in the analysis 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)).

[0112] FIG. 8 is a diagram showing an example of the interferogram F(x). The horizontal axis in FIG. 8 is the optical path difference of the analysis optical system 3, and the vertical axis is the intensity of the interference light. Note that the optical path difference of the analysis optical system 3 is the difference between the optical path lengths of the beam splitter 32 and the moving mirror 33 and the optical path lengths of the beam splitter 32 and the fixed mirror 34. In FIG. 8, the optical path difference zero is set as the origin of the horizontal axis.

[0113] 1.5.3. Fourier transform unit The Fourier transform unit 76 performs a Fourier transform on the interferogram F(x). Thereby, a spectral pattern including information unique to the sample 9 is obtained.

[0114] FIG. 9 is an example of the spectral pattern SP0 obtained by performing spectroscopic analysis on the sample 9. The spectral pattern SP0 is an example of the reflection spectrum of the sample 9.

[0115] In the spectral pattern SP0 shown in FIG. 9, sample-derived components generated by the action of the analysis light L1 on the sample 9 are reflected as absorption peaks X9. According to the spectroscopic apparatus 100, based on the spectral pattern SP0, characteristics of the sample 9, such as material, structure, component amount, etc., can be analyzed.

[0116] This spectral pattern SP0 is generated by performing a Fourier transform on the interferogram F(x). Since the interferogram F(x) is an electric field amplitude waveform obtained using the position of the moving mirror 33 as a parameter, the spectral pattern SP0 obtained by performing a Fourier transform on this has wavelength information. The position of the moving mirror 33 is directly related to the wavenumber accuracy of the spectral pattern SP0. Therefore, according to the spectroscopic apparatus 100 according to the present embodiment, since the position of the moving mirror 33 can be determined more accurately, it is possible to generate a spectral pattern SP0 with high accuracy on the wavelength axis (wavenumber axis). Further, according to the present embodiment, since it is possible to suppress a decrease in the S / N ratio of the first received light signal F(t) and a decrease in the S / N ratio of the second received light signal S2 due to the blur during the movement of the moving mirror 33, it is possible to suppress a decrease in the accuracy of the spectral pattern SP0.

[0117] 2. Modification Example of the First Embodiment Next, a modification example of the first embodiment will be described. In the following description, the description will focus on the differences from the first embodiment, and the description of the same matters will be omitted.

[0118] FIG. 10 is a cross-sectional view showing a mirror moving mechanism 1 according to a first modification example of the first embodiment. In FIG. 10, the same components as those in the first embodiment are denoted by the same reference numerals.

[0119] The first modification example is the same as the first embodiment except that the moving mirror 33 has a corner cube prism 330 instead of the substrate 334.

[0120] The corner cube prism 330 shown in FIG. 10 has an incident surface 336 and a retroreflective surface 338. The incident surface 336 is the surface on which the analysis light L1a and the length measurement light L2b are incident, and is composed of a flat surface. When light is incident on the incident surface 336, it enters the corner cube prism 330, is reflected by the retroreflective surface 338, and is emitted again from the incident surface 336. The retroreflective surface 338 is composed of the surface of the corner of a cube, and causes three internal reflections. As a result, the light emitted from the incident surface 336 can return in the same direction as the incident direction. Therefore, even when the deflection angle is large, since the positions where the reflected analysis light L1a and length measurement light L2b return are less likely to change, the loss of light intensity due to the deflection angle can be minimized.

[0121] Such a corner cube prism 330 has retroreflectivity regardless of, for example, the incident angle of light with respect to the incident surface 336. Also, in the corner cube prism 330, retroreflectivity can be realized with one member.

[0122] Note that instead of the corner cube prism 330, a corner cube mirror may be used. The corner cube mirror is also called a hollow retroreflector and has the same retroreflectivity as the corner cube prism 330. Examples of the corner cube mirror include a mount type mirror in which three mirrors are fixed to a mount member, and a replica type mirror in which a mirror material such as metal is formed on a replica member having three mutually perpendicular surfaces.

[0123] FIG. 11 is a cross-sectional view showing a mirror moving mechanism 1 according to a second modification of the first embodiment. In FIG. 11, the same components as those in the first embodiment are denoted by the same reference numerals.

[0124] The second modification is the same as the first embodiment except that reflective surfaces 332 and 333 are provided on both surfaces of the substrate 334.

[0125] The wall portion 82 shown in Fig. 11 has a through-hole 822 that penetrates through a portion intersecting the central axis AX. As a result, light can be irradiated onto both surfaces of the substrate 334. Therefore, on one surface of the substrate 334 shown in Fig. 11, a reflecting surface 332 is provided, and on the other surface, a reflecting surface 333 is provided. According to such a mirror movement mechanism 1, for example, the analysis light L1a can be made incident on the reflecting surface 332, and the length measurement light L2b can be made incident on the reflecting surface 333. As a result, an optical element for detouring the length measurement light L2b as shown in Fig. 1 becomes unnecessary, and the configuration of the length measurement optical system 4 can be simplified.

[0126] Also, since the wall portion 82 has the through-hole 822, when an adhesive is applied between the substrate 334 and the wall portion 82, the excess adhesive can be extruded toward the through-hole 822 side. As a result, the thickness of the adhesive can be made uniform. As a result, the arrangement accuracy of the reflecting surfaces 332 and 333 with respect to the wall portion 82 can be improved.

[0127] Fig. 12 is a cross-sectional view showing the mirror movement mechanism 1 according to the third modification of the first embodiment. In Fig. 12, the same components as those in the first embodiment are denoted by the same reference numerals.

[0128] The third modification is the same as the first embodiment except that the diameter of the moving mirror 33 is smaller than the beam diameter of the length measurement light L2b incident on the reflecting surface 332.

[0129] The moving mirror 33 shown in Fig. 12 has a substrate 334. The diameter of the substrate 334 shown in Fig. 12 is set to be smaller than the beam diameter of the length measurement light L2b incident on the reflecting surface 332. As a result, the length measurement light L2b reflected by the reflecting surface 332 has a beam diameter narrowed down to the diameter of the substrate 334. As a result, the moving mirror 33 shown in Fig. 12 has a function of an iris for narrowing the beam diameter. As a result, the beam diameter can be narrowed without providing an iris at another location, so the number of optical elements constituting the length measurement optical system 4 can be reduced.

[0130] FIG. 13 is a cross-sectional view showing a mirror moving mechanism 1 according to a fourth modification of the first embodiment. In FIG. 13, the same components as those in the first embodiment are denoted by the same reference numerals.

[0131] The fourth modification is the same as the first embodiment except that the length of the inner cylinder 81 in the direction of the central axis AX is equal to or greater than the length of the outer cylinder 83.

[0132] Both ends of the inner cylinder 81 shown in FIG. 13 protrude from the outer cylinder 83 in the direction of the central axis AX. According to such a configuration, even when dust is generated due to the screwing together of the first screw groove 812 and the second screw groove 832, the generated dust is less likely to adhere to the reflecting surface 332 of the moving mirror 33.

[0133] FIG. 14 is a cross-sectional view showing a mirror moving mechanism 1 according to a fifth modification of the first embodiment. FIG. 15 is a partially enlarged view of the mirror moving mechanism 1 shown in FIG. 14. In FIGS. 14 and 15, the same components as those in the first embodiment are denoted by the same reference numerals.

[0134] The fifth modification is the same as the first embodiment except that it includes a preloading portion 84 having an elastic body 842.

[0135] The mirror movement mechanism 1 shown in Fig. 14 includes a preloading portion 84 that preloads the inner cylinder 81 in the direction of the central axis AX. The preloading portion 84 shown in Fig. 14 has an elastic body 842. The elastic body 842 generates an elastic force that repels when compressed in the X-axis direction. Examples of the elastic body 842 include a coil spring, a leaf spring, rubber, an elastomer, etc. One end of the elastic body 842 on the minus side of the X-axis is fixed to the outside, and the end on the plus side of the X-axis is in contact with the inner cylinder 81. And the length of the elastic body 842 is set so as to be held in a state compressed in the X-axis direction from its natural state regardless of the position of the inner cylinder 81. Thereby, the elastic body 842 preloads the inner cylinder 81 in the direction of the central axis AX. As a result, as shown in Fig. 15, the tooth surfaces of the first thread groove 812 and the second thread groove 832 can be maintained in a contact state. Thereby, the generation of backlash due to the gap between the tooth surfaces can be suppressed, and the generation of angular deviation (deflection angle) of the moving mirror 33 can be suppressed.

[0136] Fig. 16 is a cross-sectional view showing the mirror movement mechanism 1 according to the sixth modification of the first embodiment. In Fig. 16, the same components as those in the first embodiment are denoted by the same reference numerals.

[0137] The sixth modification is the same as the first embodiment except that it includes a preloading portion 84 having a magnet 844 and a magnetic body 846.

[0138] The mirror movement mechanism 1 shown in Fig. 16 also includes a preloading portion 84 that preloads the inner cylinder 81 in the direction of the central axis AX. The preloading portion 84 shown in Fig. 16 has a magnet 844 and a magnetic body 846. The magnet 844 is, for example, a permanent magnet or an electromagnet and is fixed outside the mirror movement mechanism 1. The magnetic body 846 generates a magnetic force such as a magnetic attraction force or a magnetic repulsive force with the magnet 844. The magnetic body 846 is, for example, a magnetic metal, a metal oxide, a magnet, etc. These magnetic attraction forces and magnetic repulsive forces maintain the state where the tooth surfaces of the first thread groove 812 and the second thread groove 832 are in contact with each other as shown in Fig. 15. Thereby, the generation of backlash due to the gap between the tooth surfaces can be suppressed.

[0139] FIG. 17 and FIG. 18 are cross-sectional views showing a mirror moving mechanism 1 according to a seventh modification of the first embodiment. In FIGS. 17 and 18, the same components as those in the first embodiment are denoted by the same reference numerals.

[0140] The seventh modification is the same as the first embodiment except that the cross-sectional shapes of the threads of the first thread groove 812 and the second thread groove 832 are different.

[0141] The cross-sectional shape of the thread of the first thread groove 812 shown in FIG. 17 and the cross-sectional shape of the thread of the second thread groove 832 are each substantially a right triangle, and a part of the tooth surface (tooth surface 812a of the first thread groove 812 and tooth surface 832a of the second thread groove 832) is set to be substantially orthogonal to the X-axis. Also, the cross-sectional shape of the thread of the first thread groove 812 shown in FIG. 18 and the cross-sectional shape of the thread of the second thread groove 832 are each substantially a rectangle, and a part of the tooth surface (tooth surface 812a of the first thread groove 812 and tooth surface 832a of the second thread groove 832) is set to be substantially orthogonal to the X-axis. Then, as shown in FIGS. 17 and 18, the inner cylinder 81 is preloaded so that the state where the tooth surface 812a and the tooth surface 832a are in contact is maintained. Thereby, for example, even when the inner cylinder 81 is displaced in the Z-axis direction with respect to the outer cylinder 83, the displacement of the inner cylinder 81 in the X-axis direction can be suppressed. As a result, the adverse effect due to the displacement of the reflecting surface 332 in the X-axis direction can be suppressed.

[0142] When a plane orthogonal to the central axis AX is assumed, the angle formed by the tooth surface 812a and this plane and the angle formed by the tooth surface 832a and this plane are each preferably 15° or less, and more preferably 10° or less. Thereby, the effect of suppressing the displacement of the inner cylinder 81 in the direction of the central axis AX can be obtained more reliably. On the other hand, these angles are preferably 1° or more, and more preferably 3° or more. Thereby, the first thread groove 812 and the second thread groove 832 can be screwed together more smoothly.

[0143] FIG. 19 is a cross-sectional view showing a mirror movement mechanism 1 according to an eighth modification of the first embodiment. In FIG. 19, the same components as those in the first embodiment are denoted by the same reference numerals.

[0144] The eighth modification is the same as the first embodiment except that, as shown in FIG. 19, the second screw groove 832 does not reach the end of the outer cylinder 83 on the positive X-axis side.

[0145] According to such a configuration, the inner cylinder 81 cannot move to the end of the outer cylinder 83 on the positive X-axis side. Therefore, it is possible to prevent the inner cylinder 81 from coming out of the end of the outer cylinder 83 on the positive X-axis side.

[0146] FIG. 20 is a cross-sectional view showing a mirror movement mechanism 1 according to a ninth modification of the first embodiment. FIG. 21 is a front view of the mirror movement mechanism 1 shown in FIG. 20 as viewed from the positive X-axis side.

[0147] The ninth modification is the same as the first embodiment except that a connecting portion 85 for connecting the wall portion 82 and the moving mirror 33 is provided.

[0148] The mirror movement mechanism 1 shown in FIG. 20 includes a connecting portion 85. The connecting portion 85 connects the wall portion 82 and the moving mirror 33. Specifically, the connecting portion 85 includes a shaft 852 that penetrates the central portion of the wall portion 82 and extends along the X-axis, and a disk portion 854 that is connected to the end of the shaft 852 on the positive X-axis side and extends in the Y-Z plane. The end of the shaft 852 on the negative X-axis side is fixed to the wall portion 82 via a bearing 86. The bearing 86 supports the shaft 852 so that it can rotate around the central axis AX. The disk portion 854 supports the moving mirror 33. A part of the outer edge of the disk portion 854 constitutes a protruding portion 856 that protrudes outward. On the other hand, a guide groove 834 extending in the X-axis direction is provided on the inner surface of the outer cylinder 83 so as to cross the second screw groove 832. And the protruding portion 856 is fitted in the guide groove 834 as shown in FIG. 21.

[0149] According to such a configuration, even if the inner cylinder 81 is rotationally driven, the moving mirror 33 does not rotate. That is, even if the inner cylinder 81 is rotationally driven, power is not transmitted to the connection portion 85 supported via the bearing 86. Further, since the protruding portion 856 is fitted in the guide groove 834, the connection portion 85 is suppressed from rotating about the central axis AX, and the connection portion 85 can move in the X-axis direction. For this reason, the moving mirror 33 can move in the X-axis direction while its rotation is suppressed, and the analysis light L1a and the length measurement light L2b are always irradiated to the same position of the reflecting surface 332. As a result, problems that may occur due to the rotation of the moving mirror 33 can be solved. Specifically, it is possible to suppress the respective reflection intensities of the analysis light L1a and the length measurement light L2b from unintentionally changing due to the rotation of the moving mirror 33. Even in each of the above-described modified examples, the same effects as those of the first embodiment can be obtained.

[0150] 3. Second Embodiment Next, the mirror moving mechanism according to the second embodiment will be described.

[0151] FIG. 22 is a cross-sectional view showing the mirror moving mechanism 1 according to the second embodiment. FIG. 23 is a perspective view schematically showing the spline shaft 864 shown in FIG. 22 and the second linear groove 816 provided on the inner surface of the inner cylinder 81.

[0152] Hereinafter, the second embodiment will be described. In the following description, the differences from the first embodiment will be mainly described, and the description of the same matters will be omitted. In FIGS. 22 and 23, the same matters as those in the first embodiment are denoted by the same reference numerals. The second embodiment is the same as the first embodiment except that the configuration of the drive unit 80 is different.

[0153] The drive unit 80 shown in Fig. 22 has a motor M and a power conversion unit 862. The power conversion unit 862 shown in Fig. 22 is composed of a spline shaft 864 connected to the output shaft of the motor M, and transmits the rotational output of the motor M to the inner cylinder 81. Specifically, as shown in Fig. 23, a second linear groove 816 extending parallel to the central axis AX is provided on the inner surface of the inner cylinder 81. Further, as shown in Fig. 23, the spline shaft 864 has external teeth 866 on its outer surface. By meshing the external teeth 866 with the second linear groove 816, the rotational output is transmitted from the spline shaft 864 to the inner cylinder 81. On the other hand, the second linear groove 816 extends long in the direction of the central axis AX. For this reason, the spline shaft 864 can slide in the direction of the central axis AX while transmitting the rotational output. Thereby, the inner cylinder 81 is rotationally driven and can move in the direction of the central axis AX. Note that the spline shaft 864 may be another spline shaft used for a ball spline or the like. Similarly, the inner cylinder 81 having the second linear groove 816 may be another spline bearing.

[0154] As the motor M shown in Fig. 22, a stepping motor is particularly preferably used. Since a stepping motor can easily control the rotation angle even at a low speed, it can generate an appropriate rotational output even when the reduction ratio of the power conversion unit 862 is small. Also in the second embodiment as described above, the same effects as those of the first embodiment can be obtained.

[0155] 4. Modification of the Second Embodiment Next, a modification of the second embodiment will be described.

[0156] Hereinafter, a modification of the second embodiment will be described. In the following description, the description will focus on the differences from the second embodiment, and the description of the same matters will be omitted.

[0157] Fig. 24 is a cross-sectional view showing a mirror moving mechanism 1 according to a modification of the second embodiment. In Fig. 24, the same components as those in the second embodiment are denoted by the same reference numerals.

[0158] The modified example is the same as the second embodiment except that a flexible shaft 867 is used.

[0159] The power conversion unit 862 shown in FIG. 24 has a spline shaft 864 and a flexible shaft 867. The flexible shaft 867 is a shaft that connects the output shaft of the motor M and the spline shaft 864. Since the flexible shaft 867 has flexibility, it is possible to transmit the rotational output even if it does not extend linearly. Therefore, by using the flexible shaft 867, the degree of freedom in arranging the motor M can be increased. As a result, the size of the mirror moving mechanism 1 can be reduced, and the degree of freedom in design can be increased. Even in the modified example as described above, the same effects as those of the second embodiment can be obtained.

[0160] 5. Third Embodiment Next, an interferometer according to the third embodiment will be described.

[0161] FIG. 25 is a schematic configuration diagram showing a shape measuring device 200 as an interferometer according to the third embodiment. FIG. 26 is a functional block diagram showing each main part of the analysis unit 300, the length measuring unit 400, the periodic signal generation unit 6, and the calculation unit 7 in FIG. 25.

[0162] Hereinafter, the third embodiment will be described. In the following description, the differences from the first embodiment will be mainly described, and the description of the same matters will be omitted. In FIGS. 25 and 26, the same matters as those in the first embodiment are denoted by the same reference numerals.

[0163] The spectroscopic device 100 according to the first embodiment is a device that irradiates the analysis light L1 emitted from the first light source 51 to the sample 9 and performs spectroscopic analysis of the sample 9. On the other hand, the shape measuring device 200 according to the third embodiment is a device that irradiates the analysis light L1 to the sample 9 and measures the shape of the surface or inside of the sample 9. The shape measuring device 200 shown in FIG. 25 is the same as the spectroscopic device 100 shown in FIG. 1 except that the configuration of the analysis optical system 3 is different.

[0164] The analysis optical system 3 shown in FIG. 25 includes a first light source 51, a beam splitter 32, a condenser lens 35, a condenser lens 37, and a first light receiving element 36.

[0165] The first light source 51 shown in FIG. 25 includes, for example, white light sources such as an SLD (Super Luminescent Diode) and an LED (Light Emitting Diode), a wavelength-sweeping light source, and various lamps described in the first embodiment. Preferably, a broadband light source called a low-coherence light source is used.

[0166] The analysis light L1 emitted from the first light source 51 is split into two by the beam splitter 32. The beam splitter 32 shown in FIG. 25 reflects a part of the analysis light L1 as analysis light L1a toward the moving 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.

[0167] The beam splitter 32 also transmits the analysis light L1a reflected by the moving 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.

[0168] The first light receiving element 36 receives the interference light and acquires its intensity. Then, a signal indicating the temporal change in intensity 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 analysis light L1b and the sample 9 and the phase information derived from the above-described moving mirror 33. The sample-derived component is, for example, a change in the phase added to the analysis light L1b according to the surface shape of the sample 9.

[0169] As the first light receiving element 36, for example, in addition to a photodiode, a phototransistor, etc., image sensors such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor) can be mentioned. By using an image sensor, a two-dimensional distribution of the first light receiving signal F(t) can be acquired. Thereby, the surface shape of the sample 9 can be measured two-dimensionally.

[0170] The length measuring optical system 4, the periodic signal generation unit 6, and the mirror movement mechanism 1 shown in FIG. 25 are the same as those in FIG. 1.

[0171] The arithmetic unit 7 shown in FIG. 26 includes a moving mirror position arithmetic unit 72, a light intensity arithmetic unit 74, and a shape calculation unit 78.

[0172] Similar to the first embodiment, the light intensity arithmetic unit 74 shown in FIG. 26 generates a waveform (interferogram F(x)) representing the intensity of the first light receiving signal F(t) at each position of the moving mirror 33 based on the first light receiving signal F(t) and the moving mirror position signal X(t). The shape calculation unit 78 shown in FIG. 26 calculates the surface shape and internal shape of the sample 9 based on this waveform. Specific analysis methods are known by names such as white light interferometry and time-domain OCT (Optical Coherence Tomography).

[0173] In addition, in FIG. 25, the case where the sample 9 reflects the analysis light L1b is illustrated. However, when the sample 9 transmits the analysis light L1b, the shape measurement device 200 shown in FIG. 25 can measure the internal shape (internal structure) of the sample 9. Specific analysis methods are known by names such as optical coherence tomography.

[0174] Also in the third embodiment as described above, the same effects as those of the first embodiment can be obtained. That is, according to the third embodiment, since the effect of the mirror movement mechanism 1 can be enjoyed, a shape measurement device 200 that can measure the analysis results of the surface shape, internal shape, etc. of the sample 9 with high accuracy can be realized.

[0175] 6. Effects achieved by each of the above embodiments The mirror moving mechanism 1 according to each of the above embodiments and each modification includes a moving mirror 33, an inner cylinder 81, an outer cylinder 83, and a drive unit 80. The moving mirror 33 has a reflecting surface 332. The inner cylinder 81 supports the moving mirror 33 on its inner surface and has a first thread groove 812 extending around the central axis AX on its outer surface. The outer cylinder 83 has a second thread groove 832 on its inner surface that engages with the first thread groove 812. The drive unit 80 rotates the inner cylinder 81 around the central axis AX as the rotation axis, thereby moving the inner cylinder 81 in the direction of the central axis AX.

[0176] According to such a configuration, in the entire circumference or many parts around the central axis AX, the state where the first thread groove 812 and the second thread groove 832 are in contact is maintained. Therefore, when the inner cylinder 81 is rotationally driven, the play of the inner cylinder 81 with respect to the outer cylinder 83 can be minimized. As a result, the translational property of the movement of the moving mirror 33 can be enhanced, and the occurrence of angular deviation (deflection angle) of the moving mirror 33 can be suppressed. Also, a large movement amount of the moving mirror 33 can be ensured. Furthermore, since it is not necessary to use a large guide mechanism or the like, the size of the mirror moving mechanism 1 can be reduced.

[0177] Also, it is preferable that the length of the outer cylinder 83 in the direction of the central axis AX is longer than the distance by which the drive unit 80 moves the inner cylinder 81.

[0178] According to such a configuration, the first thread groove 812 and the second thread groove 832 can be screwed together throughout the entire movement amount of the moving mirror 33. As a result, throughout the entire movement amount of the moving mirror 33, the occurrence of a deflection angle can be suppressed.

[0179] Also, it is preferable that the moving mirror 33 is supported at an intermediate portion of the length of the inner cylinder 81 in the direction of the central axis AX.

[0180] According to such a configuration, even when dust is generated due to the screwing together of the first screw groove 812 and the second screw groove 832, the generated dust is less likely to adhere to the reflecting surface 332 of the moving mirror 33. Thereby, it is possible to suppress a decrease in the S / N ratio of the interference signal due to a decrease in the reflectance of the reflecting surface 332.

[0181] Also, the mirror moving mechanism 1 according to each of the above embodiments and each modification example may include a wall portion 82 that is fixed to the inner surface of the inner cylinder 81 and intersects the central axis AX. And the moving mirror 33 may be supported by the wall portion 82.

[0182] According to such a configuration, since the wall portion 82 and the moving mirror 33 can be prepared individually, a reflecting surface 332 with high surface accuracy can be obtained.

[0183] Also, the mirror moving mechanism 1 according to each of the above embodiments and each modification example may include a preloading portion 84 that preloads the inner cylinder 81 in the direction of the central axis AX.

[0184] According to such a configuration, it is possible to maintain the state in which the tooth surface of the first screw groove 812 and the tooth surface of the second screw groove 832 are in contact. Thereby, it is possible to suppress the occurrence of backlash due to the gap between the tooth surfaces, and it is possible to suppress the occurrence of angular deviation (deflection angle) of the moving mirror 33.

[0185] Also, the preloading portion 84 may be configured to preload the inner cylinder 81 by the elastic force generated in the elastic body 842.

[0186] According to such a configuration, it is possible to maintain the state in which the tooth surface of the first screw groove 812 and the tooth surface of the second screw groove 832 are in contact by using the elastic force.

[0187] Also, the preloading portion 84 may be configured to preload the inner cylinder 81 by the magnetic force generated by the magnet 844.

[0188] According to such a configuration, it is possible to maintain the state in which the tooth surface of the first screw groove 812 and the tooth surface of the second screw groove 832 are in contact by using the magnetic force.

[0189] Further, the angle formed by the tooth surface 812a of the first screw groove 812 and a plane orthogonal to the central axis AX, and the angle formed by the tooth surface 832a of the second screw groove 832 and the plane are preferably 15° or less.

[0190] According to such a configuration, the effect of suppressing the displacement of the inner cylinder 81 in the direction of the central axis AX can be obtained more reliably.

[0191] Further, the moving mirror 33 preferably has retroreflectivity. According to such a configuration, the light incident on the moving mirror 33 can be returned in the same direction as the incident direction. As a result, even when the deflection angle is large, since the positions where the reflected analysis light L1a and the length measurement light L2b return are less likely to change, the loss of light intensity due to the deflection angle can be minimized.

[0192] Further, the mirror moving mechanism 1 according to each of the above embodiments and each modification may include a wall portion 82 fixed to the inner surface of the inner cylinder 81, a connection portion 85 connecting the wall portion 82 and the moving mirror 33, and a bearing 86 that does not rotate the connection portion 85 when the inner cylinder 81 is rotationally driven.

[0193] According to such a configuration, the moving mirror 33 can be moved in the X-axis direction while its rotation is suppressed, and the analysis light L1a and the length measurement light L2b are always irradiated at the same position on the reflecting surface 332. As a result, problems that may occur due to the rotation of the moving mirror 33 can be eliminated. Specifically, it is possible to suppress the unintentional change in the respective reflection intensities of the analysis light L1a and the length measurement light L2b due to the rotation of the moving mirror 33.

[0194] Further, the moving mirror 33 may have a substrate 334 and reflecting surfaces 332 and 333 provided on both surfaces of the substrate 334.

[0195] According to such a configuration, for example, the analysis light L1a can be made incident on the reflecting surface 332, and the length measuring light L2b can be made incident on the reflecting surface 333. As a result, for example, an optical element for bypassing the length measuring light L2b becomes unnecessary, and the configuration of the length measuring optical system 4 can be simplified.

[0196] Further, the inner cylinder 81 may have a first linear groove 814 intersecting with the first screw groove 812 on the outer surface. Furthermore, the drive unit 80 may include a motor M and a worm gear 863 connected to the motor M and screwed with the first linear groove 814.

[0197] According to such a configuration, the reduction ratio of the power conversion unit 862 can be increased, and backlash can be reduced. As a result, it is not necessary to add a speed reducer or the like, so that the drive unit 80 can be easily miniaturized, and the position accuracy of the moving mirror 33 can be easily improved.

[0198] Further, the motor M is preferably a DC motor. According to such a configuration, it can contribute to the miniaturization of the mirror moving mechanism 1.

[0199] Further, the inner cylinder 81 may have a second linear groove 816 extending parallel to the central axis AX on the inner surface. Furthermore, the drive unit 80 may include a motor M and a spline shaft 864 that slides with respect to the inner cylinder 81 and is connected to the motor M.

[0200] According to such a configuration, the inner cylinder 81 can be rotationally driven and can move in the direction of the central axis AX.

[0201] Further, the drive unit 80 may include a flexible shaft 867 that transmits the rotational output of the motor M to the spline shaft 864.

[0202] According to such a configuration, the degree of freedom in arranging the motor M can be increased. As a result, the mirror moving mechanism 1 can be miniaturized, and the degree of freedom in design can be increased.

[0203] Also, the interferometer (spectrometer 100 or shape measurement device 200) according to the embodiment includes a mirror moving mechanism 1 according to the embodiment or each modification example that reflects the analysis light L1a, and an analysis optical system 3. The analysis optical system 3 performs interference of light including the analysis light L1a reflected by the mirror moving mechanism 1 and the analysis light L1b that has passed through the sample 9, and outputs a first light reception signal F(t) including information derived from the sample 9.

[0204] According to such a configuration, an interferometer that is miniaturized, lightweight, and low-cost can be realized. In addition, the translational property of the movement of the moving mirror 33 can be enhanced, and the occurrence of angular deviation (deviation angle) of the moving mirror 33 can be suppressed. Thereby, when the interferometer is applied to the spectrometer 100 or the shape measurement device 200, highly accurate analysis results can be obtained.

[0205] Also, the interferometer (spectrometer 100 or shape measurement device 200) according to the embodiment may further include a length measurement optical system 4. The length measurement optical system 4 makes the length measurement light L2b (laser light) incident on the reflection surface 332, and performs interference of light including the reflected length measurement light L2b, and outputs a second light reception signal S2 including information indicating the position of the moving mirror 33.

[0206] According to such a configuration, an interferogram F(x) with a larger number of data points can be obtained. The large 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. Also, even when using analysis light L1 with a shorter wavelength (larger wavenumber), an interferogram F(x) with a sufficient number of data points can be obtained. Thereby, a spectral pattern in a wider wavelength range (wider wavenumber range), that is, a wider-band spectral pattern can be obtained.

[0207] As described above, the mirror moving mechanism and the interferometer of the present invention have been described based on the illustrated embodiments. However, the mirror moving mechanism and the interferometer of the present invention are not limited to the above-described embodiments and each modification example, and the configuration of each part may be replaced with any component, or any other component may be added.

[0208] Further, the mirror moving mechanism and the interferometer of the present invention may include a combination of two or more of the above-described embodiments and their modification examples. Furthermore, each functional unit included in 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.

[0209] Also, in each of the above-described embodiments, a Michelson-type interference optical system is used, but an interference optical system of another type may be used.

[0210] Furthermore, the arrangement of the sample is not limited to the illustrated arrangement. Since the sample-derived component is generated by applying the analysis light to the sample, 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.

Explanation of Reference Numerals

[0211] 1... Mirror movement mechanism, 3... Analytical optical system, 4... Length measurement optical system, 6... Periodic signal generation unit, 7... Calculation unit, 9... Sample, 12... Optical modulator, 30... Vibration element, 32... Beam splitter, 33... Moving mirror, 34... Fixed mirror, 35... Condensing lens, 36... First light receiving element, 37... Condensing lens, 41... Second light source, 42... Beam splitter, 45... Second light receiving element, 46... Half-wave plate, 47... Quarter-wave plate, 48... Quarter-wave plate, 49... Analyzer, 51... First light source, 54... Beam splitter, 55... Condensing lens, 56... Light attenuation filter, 62... Oscillation circuit, 72... Moving mirror position calculation unit, 74... Light intensity calculation unit, 76... Fourier transform unit, 78... Shape calculation unit, 80... Driving unit, 81... Inner cylinder, 82... Wall portion, 83... Outer cylinder, 84... Preloading unit, 85... Connection portion, 86... Bearing, 100... Spectroscopic device, 200... Shape measurement device, 300... Analysis unit, 330... Corner cube prism, 332... Reflective surface, 333... Reflective surface, 334... Substrate, 336... Incident surface, 338... Retroreflective surface, 400... Length measurement unit, 401... Base portion, 402... First vibrating arm, 403... Second vibrating arm, 404... Electrode, 405... Electrode, 406... Light reflecting surface, 431... Vibration piece, 432... Groove, 433... Pad, 434... Diffraction grating, 435... Pad, 436... Vibration direction, 441... Optical path changing mirror, 442... Optical path changing mirror, 722... Pretreatment unit, 724... Demodulation processing unit, 726... Moving mirror position signal output unit, 812... First screw groove, 812a... Tooth surface, 814... First linear groove, 816... Second linear groove, 822... Through hole, 831... Window portion, 832... Second screw groove, 832a... Tooth surface, 833... Screw hole, 834... Guide groove, 842... Elastic body, 844... Magnet, 846... Magnetic body, 852... Shaft, 854... Disk portion, 856... Protrusion, 862... Power conversion unit, 863... Worm gear, 864... Spline shaft, 866... External teeth, 867... Flexible shaft, 4311... Surface, 4312... Back surface, AX... Central axis, F(t)... First light receiving signal, F(x)... Interferogram, L1... Analytical light, L1a... Analytical light, L1b... Analytical light, L2... Length measurement light, L2a... Length measurement light, L2b... Length measurement light, M... Motor, S2... Second light receiving signal, SP0... Spectrum pattern, Sd... Element drive signal, Ss... Reference signal, X(t)... Moving mirror position signal, X9... Absorption peak

Claims

1. A moving mirror having a reflecting surface, an inner cylinder that supports the moving mirror on its inner surface and has a first thread groove extending around a central axis on its outer surface, an outer cylinder having a second thread groove on its inner surface that engages with the first thread groove, a drive unit that rotates the inner cylinder about the central axis as a rotation axis to move the inner cylinder in the direction of the central axis, A mirror moving mechanism, characterized by comprising:

2. The mirror moving mechanism according to claim 1, wherein the length of the outer cylinder in the direction of the central axis is longer than the distance by which the drive unit moves the inner cylinder.

3. The mirror moving mechanism according to claim 1 or 2, wherein the moving mirror is supported at an intermediate portion of the length of the inner cylinder in the direction of the central axis.

4. fixed to the inner surface of the inner cylinder and having a wall portion intersecting the central axis, The mirror moving mechanism according to claim 1 or 2, wherein the moving mirror is supported by the wall portion.

5. The mirror moving mechanism according to claim 1 or 2, further comprising a preloading portion that preloads the inner cylinder in the direction of the central axis.

6. The mirror moving mechanism according to claim 5, wherein the preloading portion preloads the inner cylinder by an elastic force generated in an elastic body.

7. The mirror moving mechanism according to claim 5, wherein the preloading portion preloads the inner cylinder by a magnetic force generated by a magnet.

8. The mirror moving mechanism according to claim 5, wherein the angle formed by the tooth surface of the first thread groove and a plane perpendicular to the central axis, and the angle formed by the tooth surface of the second thread groove and the plane are 15° or less.

9. The mirror moving mechanism according to claim 1 or 2, wherein the moving mirror has retroreflectivity.

10. a wall portion fixed to the inner surface of the inner cylinder, a connecting portion that connects the wall portion and the moving mirror, a bearing that does not rotate the connecting portion when the inner cylinder is rotationally driven, The mirror moving mechanism according to claim 1 or 2, characterized by comprising:

11. The moving mirror, a substrate, the reflecting surfaces provided on both surfaces of the substrate, The mirror moving mechanism according to claim 1 or 2, characterized by having:

12. The inner cylinder has a first linear groove intersecting the first thread groove on its outer surface, The drive unit, a motor, a worm gear connected to the motor and engaging with the first linear groove, The mirror moving mechanism according to claim 1 or 2, characterized by having:

13. The mirror moving mechanism according to claim 12, wherein the motor is a DC motor.

14. The inner cylinder has a second linear groove extending parallel to the central axis on the inner surface thereof. The drive unit includes a motor, a spline shaft connected to the motor and sliding with respect to the inner cylinder. The mirror moving mechanism according to claim 1 or 2, having the above.

15. The mirror moving mechanism according to claim 14, wherein the drive unit has a flexible shaft that transmits the rotational output of the motor to the spline shaft.

16. The mirror moving mechanism according to claim 1 or 2 that reflects the analysis light, and an analysis optical system that outputs a first light reception signal including information derived from the sample by performing interference of light including the analysis light reflected by the mirror moving mechanism and the analysis light that has passed through the sample. An interferometer characterized by comprising the above.

17. The interferometer according to claim 16, further comprising a length measuring optical system that outputs a second light reception signal including information indicating the position of the moving mirror by causing interference of light including the laser light incident on the reflection surface and the reflected laser light.

Images