JP2025150163A - Mirror movement mechanism and interferometer - Google Patents

Abstract

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

Description

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

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

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

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

In such an optical module, the position of the movable mirror is measured based on the detection results of the interference light of the laser light. Then, based on the measurement results of the movable mirror position and the detection results of the interference light of the measurement light, spectroscopic analysis of the measurement object becomes possible. Specifically, by determining 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 object can be obtained. Therefore, the optical module described in Patent Document 1 is used in an FTIR (Fourier transform infrared spectroscopic analyzer).

Patent document 2 discloses the use of an optical microelectromechanical system (optical MEMS device) in an FTIR spectrometer. The optical MEMS device includes a movable corner cube reflector, a fixed mirror, and a MEMS actuator. The optical MEMS device can achieve a large optical path delay (optical path difference), thereby expanding the resolution range of the FTIR spectrometer.

International Publication No. 2019/009404 Special Publication No. 2012-524295

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

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

The optical MEMS device described in Patent Document 2 uses a MEMS actuator. However, MEMS actuators are unable to ensure a sufficient amount of movement. Furthermore, the movable corner cube reflector described in Patent Document 2 is composed of a combination of two moving edges and a fixed mirror. These require a large amount of space, making miniaturization difficult.

The challenge, therefore, is to develop a mirror movement mechanism that can suppress the effects of shaking when the mirror moves, is easily miniaturized, and can easily ensure a large amount of movement.

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

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

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

The mirror movement mechanism and interferometer of the present invention will be described in detail below based on the embodiments shown in the accompanying drawings.

1. First Embodiment First, an interferometer according to the first embodiment will be described.

Figure 1 is a schematic diagram showing the configuration of a spectroscopic device 100 as an interferometer according to the first embodiment. Figure 2 is a functional block diagram showing the main components of the analysis unit 300, length measurement unit 400, periodic signal generation unit 6, and calculation unit 7 shown in Figure 1.

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

As shown in FIG. 1, the spectrometer 100 includes an analysis unit 300 having an analytical optical system 3 and a mirror movement mechanism 1 (the mirror movement 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.

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

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

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 neutral density filter 56. Note that in the analysis optical system 3, some of these optical elements may be omitted, or other optical elements may be added, or they may be replaced with other optical elements.

The first light source 51 is a light source that emits, for example, white light, i.e., light composed of a wide range of wavelengths, as analytical light L1. The wavelength range of analytical light L1, i.e., the type of first light source 51, is selected appropriately depending on 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, infrared lamp, and tungsten lamp. When performing visible spectroscopic analysis, examples of the first light source 51 include a halogen lamp. When performing ultraviolet spectroscopic analysis, examples of the first light source 51 include a deuterium lamp and a UV-LED (ultraviolet light-emitting diode).

Note that by selecting a wavelength of analytical light L1 that is greater than or equal to 100 nm and less than 760 nm, a spectroscopic device 100 capable of performing ultraviolet spectroscopic analysis or visible spectroscopic analysis can be realized. Furthermore, by selecting a wavelength of analytical light L1 that is greater than or equal to 760 nm and less than or equal to 20 μm, a spectroscopic device 100 capable of performing infrared spectroscopic analysis or near-infrared spectroscopic analysis can be realized. Moreover, by selecting a wavelength of analytical light L1 that is greater than or equal to 30 μm and less than or equal to 3 mm, a spectroscopic device 100 capable of performing terahertz spectroscopic analysis can be realized.

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

The first light source 51 may also be a laser light source that emits laser light. By using a laser light source as the first light source 51, a spectroscopic device 100 can be obtained that can perform laser excitation spectroscopic analysis of the sample 9, such as Fourier Raman spectroscopic analysis and Fourier fluorescence spectroscopic analysis. In this case, the configuration of the analytical optical system 3 may be changed from the configuration described above. The laser light source may be a known light source used for Raman spectroscopy or fluorescence spectroscopy.

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

For example, a non-polarizing beam splitter is used as the beam splitter 54, but a polarizing beam splitter may also be used. In this case, the necessary wave plates can be added as appropriate.

The condenser lens 55 condenses the analytical light L1, reducing the spot size of the analytical light L1 irradiated onto the sample 9. The condenser lens 55 also condenses the diffused light emitted from the sample 9, thereby enabling localized analysis. If localized analysis is not required, the condenser lens 55 may be omitted.

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

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

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

Types of beam splitter 32 include, for example, the prism-type element (cube-type element) shown in Figure 1, as well as plate-type elements and stacked-type elements. When a plate-type beam splitter 32 is used, wavelength dispersion occurs between the analytical light L1a and analytical light L1b, so if necessary, a wavelength dispersion compensation plate may be placed between the beam splitter 32 and the fixed mirror 34.

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

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

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

The movable mirror 33 comprises multiple optical elements with retroreflectivity arranged along the light incident surface 332. Retroreflectivity refers to the property of light that is reflected by the light incident surface 332 in a manner that follows the direction of incidence. By having such retroreflectivity, even if the movable mirror 33 shakes as it moves, it is possible to suppress angular deviation (angle of deviation) of the reflected analytical light L1a relative to the direction of incidence. This makes it possible to suppress a decrease in analytical accuracy due to angular deviation.

In addition, the driver 80 can translate the movable mirror 33 by the desired amount of movement. This ensures a large amount of movement for the movable mirror 33. As a result, a spectrometer 100 (interferometer) with high wavelength resolution (wavenumber resolution) for spectral information can be realized.

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

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

The focusing lens 35 focuses the interference light, i.e., the mixed analytical light L1a and L1b, onto the first light receiving element 36. Depending on the area of the light receiving portion of the first light receiving element 36, the focusing lens 35 may be omitted.

The first light receiving element 36 receives the interference light and acquires its intensity. It then outputs a signal indicating the change in intensity over time as the first light receiving signal F(t). This first light receiving signal F(t) contains sample-derived components generated by the interaction between the analytical light L1 and the sample 9, as well as phase information derived from the position of the movable mirror 33 described above.

Examples of the first light receiving element 36 include a photodiode, a phototransistor, and a photomultiplier tube (PMT). Examples of photodiodes include InGaAs-based photodiodes, Si-based photodiodes, and avalanche photodiodes.

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

1.2. Length Measurement Optical System The length measurement optical system 4 is a Michelson-type interference optical system and includes a second light source 41, a beam splitter 42, an optical modulator 12, a second light receiving element 45, a half-wave plate 46, a quarter-wave plate 47, a quarter-wave plate 48, an analyzer 49, and optical path changing mirrors 441 and 442. Note that the length measurement optical system 4 may omit some of these optical elements, may include other optical elements, or may replace these optical elements with other optical elements. The length measurement optical system 4 uses optical heterodyne interferometry to output phase information derived from the position of the movable mirror 33 or frequency information derived from the moving speed to the calculation unit 7. In this specification, this information is referred to as a "length measurement component."

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

The second light source 41 is preferably a semiconductor laser element. This allows the spectroscopic device 100 to be made smaller, lighter, and consume less power.

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

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

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

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

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

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

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

In addition, the vibration element 30 functions as the vibration source when the periodic signal generating unit 6 generates the reference signal Ss.

Examples of the oscillator element 30 include a quartz oscillator, a silicon oscillator, and a ceramic oscillator. These oscillators utilize mechanical resonance, resulting in a high Q value and easy stabilization of the natural frequency. This increases the S/N ratio of the modulated component applied by the optical modulator 12 to the measurement light L2a, and also increases the accuracy of the reference signal Ss. As a result, the position of the movable mirror 33 can be determined with high precision, ultimately resulting in a spectrometer 100 capable of generating a spectral pattern with high accuracy on the wavelength axis (wavenumber axis).

Examples of quartz crystal oscillators include quartz crystal AT oscillators, SC-cut quartz crystal oscillators, tuning-fork quartz crystal oscillators, and quartz surface acoustic wave elements. The oscillation frequency of a quartz crystal oscillator is, for example, from 1 kHz to several hundred MHz.

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

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

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

Examples of the second light receiving element 45 include a photodiode, a phototransistor, etc.

The optical components included in each optical system have been described above, but it is preferable that optical components that require light to be incident upon be anti-reflection treated. This can improve the S/N ratio of the first received light signal F(t) and the second received light signal S2.

2 generates a periodic signal using the vibration element 30 as a source of oscillation and outputs a reference signal Ss. In this embodiment, the periodic signal generator 6 has an oscillation circuit 62 that causes the vibration element 30 to oscillate.

An example of the oscillator circuit 62 is the oscillator circuit disclosed in Japanese Patent Application Laid-Open No. 2022-38156. The oscillator circuit 62 operates using the vibration element 30 as a signal source and generates a highly accurate periodic signal. This allows the oscillator circuit 62 to output a highly accurate element drive signal Sd and reference signal Ss. Therefore, when the element drive signal Sd and the reference signal Ss are affected by an external disturbance, they are affected in the same way. As a result, the modulation component added via the vibration element 30 driven by the element drive signal Sd and the reference signal Ss are affected in the same way. Therefore, when the second light receiving signal S2 and the reference signal Ss are subjected to calculations in the calculation unit 7, the effects of the disturbance contained in both can be canceled out or reduced during the calculation process. As a result, the calculation unit 7 can accurately determine the position of the movable mirror 33, even when affected by an external disturbance.

Note that the oscillator circuit disclosed in the above publication uses an inverter IC, but a Colpitts oscillator circuit may be used instead.

Furthermore, the periodic signal generating unit 6 is not particularly limited as long as it has the function of generating a periodic signal. For example, it may be a signal generator, a function generator, etc.

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

The mirror moving mechanism 1 shown in FIG. 3 includes a moving mirror 33 and a drive unit 80 .
The movable mirror 33 has a base material 330 and a plurality of triangular pyramidal concave surfaces 381 (retroreflective optical elements) disposed on the base material 330 and arranged along a light incident surface 332 parallel to the Y-Z plane. The light incident surface 332 refers to a range of a plane intersecting the incident direction of the analytical light L1a, configured to be displaced in the incident direction of the analytical light L1a. By arranging a plurality of triangular pyramidal concave surfaces 381 in such a range, the volume of each triangular pyramidal concave surface 381 can be reduced. This allows the movable mirror 33 to be made smaller and thinner than conventional corner cube mirrors, etc.

The base material 330 is, for example, in the form of a plate extending along the Y-Z plane. It also has the rigidity necessary to support the multiple triangular pyramidal concave surfaces 381. By driving the base material 330 with the drive unit 80, the multiple triangular pyramidal concave surfaces 381 can be translated with precision in the X-axis direction.

The constituent material of the substrate 330 is not particularly limited, but examples include metal materials, ceramic materials, resin materials, etc.

The triangular pyramidal concave surface 381 shown in Figure 4 can be thought of as the inner surface of a cavity defined by the four faces that make up the triangular pyramid. One of the four faces is set parallel to the light incident surface 332 and serves as the opening face of the cavity. The remaining three faces are reflective surfaces 382 that are arranged around vertex P, which is located on the negative X-axis side of the opening face, and connect the opening face to vertex P.

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

The triangular pyramidal concave surface 381 may be replaced by a concave surface having a shape other than a triangular pyramid. Examples of replaceable concave surfaces include a concave surface having multiple reflective surfaces and configured to exhibit retroreflectivity through multiple reflections. Specific examples include concave surfaces that form a quadrangular pyramid or a polygonal pyramid of greater polygonal shape. In this case, there is no particular limit to the number of reflections.

The triangular pyramidal concave surfaces 381 may be formed directly on the substrate 330, but in this embodiment, they are formed on the surface of a mirror array sheet 331 (retroreflective sheet) placed on the substrate 330. The mirror array sheet 331 is a sheet with a front surface on which multiple triangular pyramidal concave surfaces 381 (retroreflective optical elements) are arranged, and a flat back surface.

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

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

A metal film 383 is formed on the reflective surface 382. This provides the reflective surface 382 with good light reflectivity. Examples of materials that can be used for the metal film 383 include aluminum, nickel, silver, gold, and other elements, either alone or as alloys. A dielectric multilayer film or a resin film may also be used in conjunction with the metal film 383. This can add functions such as increasing the reflectivity of the metal film 383 and suppressing deterioration of the metal film 383.

Furthermore, the reflecting surface 382 described above can reflect the analytical light L1a without passing through solids such as glass or transparent resin. Therefore, even if the analytical light L1a is white light, optical path differences between wavelengths are unlikely to occur. This prevents phase changes between wavelengths, thereby preventing the associated decrease in the S/N ratio of the first received light signal F(t).

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

The drive unit 80 shown in FIG. 1 has a motor M and a power conversion unit 862. The motor M generates a rotational force. The power conversion unit 862 converts the rotational force of the motor M into linear motion, driving the movable mirror 33 in the direction of incidence of the analytical light L1a on the light incident surface 332 (the X-axis direction). This configuration makes it possible to realize a drive unit 80 that can ensure a sufficiently large amount of movement of the movable mirror 33.

Motor M generates a rotational force in a predetermined direction and at a predetermined rotational speed. Examples of motor M include a stepping motor, a DC motor, and an ultrasonic (piezo) motor.

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

Furthermore, in this embodiment, both the analytical light L1a and the measurement light L2b are incident on the light incident surface 332 of the movable mirror 33. It is preferable that the incident positions of the analytical light L1a and the measurement light L2b on the light incident surface 332 are different from each other. This prevents the two types of light from being mixed together.

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

Examples of processors include a CPU (Central Processing Unit) and a DSP (Digital Signal Processor). Instead of using these processors to execute software, it is also possible to use a FPGA (Field-Programmable Gate Array) or ASIC (Application Specific Integrated Circuit) to implement the above-mentioned functions.

Examples of memory include HDDs (Hard Disk Drives), SSDs (Solid State Drives), EEPROMs (Electrically Erasable Programmable Read-Only Memory), ROMs (Read-Only Memory), and RAMs (Random Access Memory).

Examples of external interfaces include digital input/output ports such as USB (Universal Serial Bus), Ethernet (registered trademark) ports, etc.

Examples of the input unit include various input devices such as a keyboard, mouse, touch panel, and touchpad. Examples of the display unit include a liquid crystal display panel and an organic EL (Electro Luminescence) display panel. Note that the input unit and display unit may be provided as needed and may be omitted.

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

The moving mirror position calculation unit 72 shown in FIG. 2 has a pre-processing unit 722, a demodulation processing unit 724, and a moving mirror position signal output unit 726. The pre-processing unit 722 and the demodulation processing unit 724 can be, for example, the pre-processing unit and demodulation unit disclosed in Japanese Patent Application Laid-Open No. 2022-38156.

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

The moving mirror position signal output unit 726 generates and outputs a moving mirror position signal X(t) based on the 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 manner is a signal representing the position of the moving mirror 33, which changes over time, and captures the displacement of the moving mirror 33 at intervals sufficiently narrower than the wavelength of the measurement light L2. For example, if the wavelength of the measurement light L2 is several hundred nanometers, a position resolution of less than 10 nanometers can be achieved for the moving mirror position signal X(t). This allows the light intensity calculation unit 74 to generate highly accurate digital data of the interferogram F(x).

Figure 6 shows an example of the first light receiving signal F(t) and the movable mirror position signal X(t) acquired by the spectrometer 100 shown in Figure 1. The horizontal axis of Figure 6 represents time t, and the vertical axis represents the intensity of the interference light incident on the first light receiving element 36 or the position of the movable mirror 33.

The moving mirror position signal X(t) shown in Figure 6 is an image of a signal that continuously detects changes in the position of the moving mirror 33, achieving high position resolution. By generating an interferogram F(x) based on this moving mirror position signal X(t), an interferogram F(x) with a larger number of data points can be obtained. A larger number of data points means that the sampling interval of the interferogram F(x) is shorter and the accuracy is higher. Therefore, it is ultimately possible to obtain a spectral pattern with high wavelength resolution (wavenumber resolution).

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

1.5.2. Light Intensity Calculation Unit The light intensity calculation unit 74 generates a waveform (interferogram F(x)) that represents the intensity of the interference light with respect to the position of the movable mirror 33, based on the first light reception signal F(t) and the movable mirror position signal X(t).

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

Figure 7 shows an example of an interferogram F(x). The horizontal axis of Figure 7 represents the optical path difference of the analytical optical system 3, and the vertical axis represents the intensity of the interference light. Note that the optical path difference of the analytical optical system 3 is the difference between the optical path length between the beam splitter 32 and the movable mirror 33 and the optical path length between the beam splitter 32 and the fixed mirror 34. In Figure 7, the origin of the horizontal axis is zero optical path difference.

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

Figure 8 shows an example of a spectral pattern SP0 obtained by performing spectroscopic analysis on sample 9. Spectral pattern SP0 is an example of the reflectance spectrum of sample 9.

In the spectral pattern SP0 shown in Figure 8, sample-derived components generated when analytical light L1 acts on sample 9 are reflected as absorption peak X9. Using the spectroscopic device 100, the characteristics of sample 9, such as material, structure, and component amounts, can be analyzed based on the spectral pattern SP0.

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

In this specification, the movement of the movable mirror 33 includes not only the translation of the entire movable mirror 33 as shown in FIG. 3, but also the displacement of the portions of the light reflecting surface 332 that reflect the analytical light L1a and the measurement light L2b. Similarly, the driving of the movable mirror 33 by the driver 80 includes not only the translation of the entire movable mirror 33, but also the displacement of the portions of the light reflecting surface 332 that reflect the analytical light L1a and the measurement light L2b.

2. Modifications of the First Embodiment Next, a description will be given of modifications of the first embodiment. In the following description, differences from the first embodiment will be mainly described, and descriptions of similar points will be omitted.

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

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

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

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

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

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

The second variant is similar to the first embodiment, except that the mirror array sheet 331 is equipped with multiple triangular pyramidal prisms 385 (retroreflective optical elements) instead of the triangular pyramidal concave surface 381 described above.

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

In this type of triangular pyramid prism 385, the incident analytical light L1a is internally reflected once by each of the three reflecting surfaces 382, regardless of its angle of incidence. This allows the analytical light L1a to be returned (reflected) in the same direction as its incidence.

The triangular pyramid prism 385 may be replaced with a prism having a shape other than a triangular pyramid. Examples of replaceable prisms include prisms with multiple reflective surfaces that are configured to exhibit retroreflectivity through multiple reflections. Specific examples include polygonal pyramid prisms with a square or larger pyramid shape, and bead-shaped prisms with various spherical shapes such as perfect spheres and ellipsoids. In this case, there is no particular limit to the number of reflections. However, from the perspective of retroreflectivity and reflection efficiency, polygonal pyramid prisms, including the triangular pyramid prism 385, are preferably used.

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

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

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

The second embodiment will be described below. The following explanation will focus on the differences from the first embodiment, and will omit a description of similarities. Note that in Figure 11, the same reference numerals are used to designate components similar to those in the first embodiment.

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

The spiral surface 333 is a spiral surface arranged around a central axis AX extending in the X-axis direction. The mirror array sheet 331 is attached to the spiral surface 333.

The mirror array sheet 331 has multiple retroreflective optical elements (not shown) arranged on it. When the analytical light L1a is irradiated onto the mirror array sheet 331 while the substrate 330 is rotated around the central axis AX, the irradiation position displaces in the X-axis direction as the substrate 330 rotates. This allows the optical path length of the analytical light L1a to be changed. In other words, the drive unit 80 shown in FIG. 11 can drive the movable mirror 33 in the X-axis direction.

In addition, in this embodiment, the shape of the base material 330 converts the rotational force of the motor M into a driving force that displaces the mirror array sheet 331 in the X-axis direction. With this configuration, the power conversion unit 862 can be omitted, making it possible to reduce the size, weight, and cost of the driving unit 80.

Measuring light L2b is also irradiated onto the mirror array sheet 331. This allows changes in the optical path length of the analytical light L1a to be measured. Note that in Figure 11, for convenience of illustration, the analytical light L1a and measuring light L2b are irradiated along the same optical path, but it is preferable that they are offset from each other. This also applies to the other figures described below.

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

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

The third embodiment will be described below. The following explanation will focus on the differences from the second embodiment, and will omit a description of similarities. Note that in Figure 12, the same reference numerals are used to designate components similar to those in the second embodiment.

The third embodiment is similar to the second embodiment, except that the substrate 330 has a spiral surface 334 and a mirror array sheet 331 (retroreflective sheet) is disposed on this spiral surface 334.

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

When analytical light L1a is irradiated onto the mirror array sheet 331 while the substrate 330 is rotated around the central axis AX, the irradiation position displaces in the X-axis direction as the substrate 330 rotates. This allows the optical path length of analytical light L1a to be changed. In other words, the drive unit 80 shown in Figure 12 can drive the movable mirror 33 in the X-axis direction.

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

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

The fourth embodiment will be described below. The following explanation will focus on the differences from the first embodiment, and will omit a description of similarities. Note that in Figures 13 and 14, the same reference numerals are used to designate components similar to those in the first embodiment.

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

A mirror array sheet 331 (retroreflective sheet) is attached to the side surface 335 of the substrate 330 shown in Figure 13. Also, a spiral step is provided around the central axis AX on the side surface 335 of the substrate 330 shown in Figure 14. The mirror array sheet 331 is then attached to this step.

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

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

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

The lens unit 39 shown in FIG. 15 has a beam diameter expansion lens 391 that expands the beam diameter of the analytical light L1a. The beam diameter expansion lens 391 is provided in a position opposite the light incident surface 332. This allows the analytical light L1a, which has a larger beam diameter than in the first embodiment, to be incident on the mirror array sheet 331. Furthermore, the analytical light L1a reflected by the mirror array sheet 331 returns in the same direction as the incident light, so it is incident on the beam diameter expansion lens 391 and converted into parallel light.

This configuration allows more triangular pyramidal concave surfaces 381 (retroreflective optical elements) to act on the analytical light L1a. This reduces the influence of individual differences in the triangular pyramidal concave surfaces 381, manufacturing errors, and blurring of the base material 330 on the analytical light L1a.

Figure 16 is a diagram showing an example of the intensity distribution in the cross section of the analytical light L1a with and without the lens portion 39 shown in Figure 15.

Figure 16(a) is a schematic diagram, expressed in shades, of the cross-sectional intensity distribution of analytical light L1a when the lens portion 39 is not present. The striped lines indicate dark areas formed by the projection of the boundaries between the triangular pyramidal concave surfaces 381. These dark areas are generated because the reflectivity decreases at the boundaries between the triangular pyramidal concave surfaces 381. When the lens portion 39 is not present, there are fewer triangular pyramidal concave surfaces 381 acting on the analytical light L1a, so the influence of the dark areas is strongly reflected in the analytical light L1a. When such analytical light L1a interferes with other analytical light L1b, the problem arises that the influence of the fluctuation of analytical light L1a is likely to be strongly reflected in the interference intensity.

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

The shape of the light diameter expansion lens 391 is not particularly limited as long as it is capable of expanding the light diameter. Furthermore, the lens unit 39 may be composed of a collection of multiple lenses, or may include other optical elements such as mirrors and prisms.

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

7. Modification of the Fifth Embodiment Next, a modification of the fifth embodiment will be described. In the following description, differences from the fifth embodiment will be mainly described, and a description of similar points will be omitted. Note that in FIG. 17, the same reference numerals are used to designate the same components as those in the fifth embodiment.

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

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

With this configuration, the irradiation range of the analytical light L1a can be maintained constant even when the movable mirror 33 moves. This prevents the number of triangular pyramidal concave surfaces 381 that act on the analytical light L1a from changing as the movable mirror 33 moves.

Furthermore, with the above configuration, the distance between the moving mirror 33 and the lens unit 39 is allowed to change. Therefore, the mirror moving mechanism 1 shown in Figure 17 includes a fixed stage 863, and the lens unit 39 is supported by this fixed stage 863.

With this configuration, the drive unit 80 does not need to drive the lens unit 39, which simplifies the structure of the drive unit 80, making it smaller and less expensive.

The shape of the collimating lens 392 is not particularly limited as long as it is capable of collimating the analytical light L1a. The lens unit 39 may be composed of a collection of multiple lenses, or may include other optical elements such as mirrors or prisms.

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

As shown in FIG. 18, the analytical light L1a and the measurement light L2b must be incident on different first and second regions of the light incident surface 332. This prevents a decrease in the S/N ratio (S/N ratio of interference intensity) of the first received light signal F(t) and the second received light signal S2 that occurs when the analytical light L1a and the measurement light L2b coexist.

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

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

The sixth embodiment will be described below. The following explanation will focus on the differences from the first embodiment, and will omit a description of similarities. Note that in Figure 19, the same reference numerals are used for components similar to those in the first embodiment.

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

The bending piezo actuator 388 is, for example, rectangular, and one longitudinal end is fixed to the fixed portion 81. A mirror array sheet 331 is also attached to the bending piezo actuator 388.

The drive unit 80 has the function of applying a voltage to the bending piezoelectric actuator 388. When a voltage is applied, the bending piezoelectric actuator 388 is displaced in the X-axis direction, as shown in Figure 19. The amount of displacement can also be adjusted by adjusting the voltage.

When the analytical light L1a is irradiated onto the mirror array sheet 331 while changing the voltage applied to the bending piezo actuator 388, the irradiation position is displaced in the X-axis direction. This allows the optical path length of the analytical light L1a to be changed. In other words, the drive unit 80 shown in Figure 19 can drive the movable mirror 33 in the X-axis direction.

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

9. Advantages of the Present Embodiments The mirror moving mechanism 1 according to the present embodiment and the modifications includes a movable mirror 33 (mirror unit) and a drive unit 80 that drives the movable mirror 33. The movable mirror 33 includes a plurality of retroreflective optical elements arranged along the light incident surface 332.

This configuration reduces the effects of shaking when the moving mirror 33 moves, and makes it possible to realize a mirror moving mechanism 1 that is easy to miniaturize and ensures a large amount of movement.

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

This configuration makes it possible to create an optical element that accurately returns (reflects) incident light in the same direction as the incident direction.

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

This configuration allows the reflective surface 382 to have good light reflectivity.

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

This configuration makes it possible to achieve an optical element with good retroreflectivity and reflection efficiency.

In the mirror moving mechanism 1 according to each of the above-described embodiments and modifications, the moving mirror 33 (mirror portion) is provided with a protective film 337 that covers the retroreflective optical element (triangular pyramidal concave surface 381).

This configuration protects the optical elements from foreign matter adhesion, oxidation, etc., thereby suppressing deterioration of reflection efficiency over time.

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

This configuration makes it possible to realize a drive unit 80 that can ensure a sufficiently large amount of movement for the movable mirror 33.

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

This configuration makes it easy to construct a movable mirror 33 in which multiple triangular pyramidal concave surfaces 381 are precisely aligned, resulting in a movable mirror 33 that is easy to manufacture. Furthermore, mirror array sheets 331 are widely used for a variety of purposes and are relatively easy to obtain, which also contributes to reducing the cost of the movable mirror 33.

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

With this configuration, the shape of the helical surface 333 eliminates the need for a mechanism that converts rotational force into linear motion, such as the power conversion unit 862, making it possible to realize a drive unit 80 that can move the movable mirror 33 while achieving miniaturization, weight reduction, and cost reduction.

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

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

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

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

The mirror movement mechanism 1 according to each of the above embodiments and modifications includes a lens unit 39 that is disposed opposite the light incident surface 332 and expands the diameter of light incident on the light incident surface 332.

This configuration allows more optical elements to act on the light incident on the light incident surface 332. This reduces the impact on the light reflected by the movable mirror 33 due to individual differences in the optical elements, manufacturing errors, and blurring of the base material 330.

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

This configuration allows the distance between the movable mirror 33 and the lens unit 39 to be maintained constant. As a result, changes in the diameter expansion rate of the analytical light L1a can be suppressed, minimizing the impact on interference intensity.

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

With this configuration, the light irradiation range can be maintained constant even when the movable mirror 33 moves. This prevents the number of optical elements acting on the light from changing as the movable mirror 33 moves.

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

This configuration allows for a simpler, more compact, and less expensive structure for the drive unit 80.

In the mirror moving mechanism 1 according to each of the above embodiments and modifications, the moving mirror 33 (mirror unit) includes a bending piezo actuator 388 and a mirror array sheet 331 (retroreflective sheet). The mirror array sheet 331 is disposed on the bending piezo actuator 388 and has multiple optical elements. The driver 80 applies a voltage to the bending piezo actuator 388.

This configuration allows for a simpler, more compact, and less expensive structure for the movable mirror 33.

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

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

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

This configuration can suppress the decrease in the S/N ratio of the interference intensity that occurs when analytical light L1a and measurement light L2b coexist.

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

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

Furthermore, although a Michelson-type interference optical system is used in each of the above embodiments, other types of interference optical systems may also be used.

Furthermore, the sample placement is not limited to the placement shown in the figure. Sample-derived components are generated by applying analytical light to the sample, so the sample can be placed in any position as long as the analytical light emitted from the sample can be incident on the first light-receiving element.

1...mirror moving mechanism, 3...analysis optical system, 4...length measurement optical system, 6...periodic signal generating unit, 7...calculating unit, 9...sample, 12...optical modulator, 30...vibration element, 32...beam splitter, 33...moving mirror, 34...fixed mirror, 35...condensing lens, 36...first light receiving element, 39...lens unit, 41...second light source, 42...beam splitter, 45...second light receiving element, 46...half wave plate, 47...quarter wave plate, 48...1 /4 wave plate, 49... analyzer, 51... first light source, 54... beam splitter, 55... condenser lens, 56... neutral density filter, 62... oscillator circuit, 72... moving mirror position calculation unit, 74... light intensity calculation unit, 76... Fourier transform unit, 80... drive unit, 81... fixed unit, 100... spectroscopic device, 300... analysis unit, 330... substrate, 331... mirror array sheet, 332... light incident surface, 333... spiral surface, 334... spiral surface, 33 5...side surface, 337...protective film, 339...adhesive layer, 381...triangular pyramidal concave surface, 382...reflecting surface, 383...metal film, 385...triangular pyramidal prism, 388...bending type piezo actuator, 391...light diameter expansion lens, 392...parallelizing lens, 400...length measuring unit, 441...light path changing mirror, 442...light path changing mirror, 722...preprocessing unit, 724...demodulation processing unit, 726...moving mirror position signal output unit, 862... Power conversion unit, 863... fixed stage, AX... center axis, F(t)... first received light 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, P... vertex, S2... second received light signal, SP0... spectrum pattern, Sd... element drive signal, Ss... reference signal, X(t)... moving mirror position signal, X9... absorption peak

Claims (17)

a mirror portion including a plurality of retroreflective optical elements arranged along a light incident surface;
a driving unit that drives the mirror unit;
A mirror moving mechanism comprising: The mirror movement mechanism described in claim 1, wherein the optical element has multiple reflective surfaces and is configured to exhibit the retroreflectivity through multiple reflections on the reflective surfaces. The mirror movement mechanism described in claim 2, wherein the optical element has a metal film formed on the reflective surface and is configured to reflect light from the surface of the metal film. The mirror movement mechanism described in claim 1, wherein the optical element has multiple prisms and is configured to exhibit the retroreflectivity through multiple internal reflections in the prisms. A mirror movement mechanism according to any one of claims 2 to 4, wherein the mirror section is provided with a protective film covering the optical element. The drive unit is
A motor that generates rotational force;
a power conversion unit that converts the rotational force into a linear motion and drives the mirror unit along the incident direction of light with respect to the light incident surface;
2. The mirror moving mechanism according to claim 1, further comprising: The mirror portion is
A substrate;
a retroreflective sheet disposed on the substrate and having a plurality of the optical elements;
The mirror moving mechanism according to claim 1 , comprising: the substrate has a spiral surface that is spirally formed around a central axis,
The retroreflective sheet is disposed on the spiral surface,
The mirror moving mechanism according to claim 7 , wherein the drive unit rotates the mirror unit around the central axis as a rotation axis. The substrate has a spiral surface that forms a spiral shape extending outward from the central axis when viewed from above the central axis,
The retroreflective sheet is disposed on the spiral surface,
The mirror moving mechanism according to claim 7 , wherein the drive unit rotates the mirror unit around the central axis as a rotation axis. The substrate has a conical shape having a central axis,
The retroreflective sheet is disposed on a side surface of the cone-shaped substrate,
The mirror moving mechanism according to claim 7 , wherein the drive unit translates the mirror unit along the central axis while rotating the mirror unit around the central axis as a rotation axis. A mirror movement mechanism according to any one of claims 1 to 4, comprising a lens section disposed opposite the light incident surface and expanding the diameter of light incident on the light incident surface. The mirror movement mechanism described in claim 11, wherein the drive unit drives the mirror unit and the lens unit. The lens portion is
a light diameter expansion lens that expands the light diameter of light incident on the light incident surface;
a collimating lens provided between the light diameter expansion lens and the mirror portion, the collimating lens collimating the light whose diameter has been expanded by the light diameter expansion lens;
The mirror moving mechanism according to claim 11 , further comprising: The mirror movement mechanism described in claim 13, wherein the drive unit drives the mirror unit but does not drive the lens unit. The mirror portion is
Bending piezo actuator,
a retroreflective sheeting having a plurality of the optical elements and disposed on the bending type piezoelectric actuator;
Equipped with
The mirror moving mechanism according to claim 1 , wherein the driving unit applies a voltage to the bending type piezoelectric actuator. A mirror moving mechanism according to any one of claims 1 to 4;
an analytical optical system that outputs information derived from the sample by causing interference of light including light reflected by the mirror unit and light that has passed through the sample;
An interferometer comprising: a length measurement optical system that detects a displacement of the mirror portion by irradiating the mirror portion with a laser beam and receiving the reflected laser beam and analyzing the intensity of the reflected laser beam;
the analytical optical system is configured to irradiate a first region of the light incident surface with light;
17. The interferometer according to claim 16, wherein the length measurement optical system is configured to irradiate the laser light onto a second area of the light incident surface that is different from the first area.