CN111684335A

CN111684335A - Spectrometer, imaging device, scanning device, and position measurement device

Info

Publication number: CN111684335A
Application number: CN201880088746.9A
Authority: CN
Inventors: 村田佳史
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 2018-04-20
Filing date: 2018-11-06
Publication date: 2020-09-18
Also published as: WO2019202761A1

Abstract

The invention provides a spectroscope, an imaging device, a scanning device, and a position measuring device capable of controlling the wavelength of light at high speed and with high accuracy. The optical splitter (1) is provided with a piezoelectric member (10), wherein the piezoelectric member (10) has a first main surface (11) and a second main surface (12) which are parallel to each other and face each other, and wherein the distance between the first main surface and the second main surface is periodically changed by the piezoelectric effect when an alternating voltage is applied, and wherein the piezoelectric member causes light incident on the piezoelectric member to be multiply reflected between the first main surface and the second main surface, and emits light having a wavelength which changes according to the change in the distance between the first main surface and the second main surface.

Description

Spectrometer, imaging device, scanning device, and position measurement device

Technical Field

The invention relates to a spectroscope, an imaging device, a scanning device, and a position measuring device.

Background

In the related art, an etalon is known as a filter for extracting light having a desired wavelength from light having a wide frequency band. The etalon is a device that extracts light having a wavelength in a narrow band by causing light to multiply reflect between two mirrors provided in parallel and facing each other.

For example, patent document 1 below discloses an air gap etalon that extracts light of a desired wavelength based on a gap between a wavelength conversion element that converts the wavelength of incident fundamental light and an optical component.

Patent document 2 discloses a wavelength variable filter including a Photoelastic modulation (PEM) element that periodically modulates the polarization state of incident light, and a plurality of polarizers and mirrors provided above and below the PEM element. In this wavelength variable filter, incident light is multiply reflected between the upper and lower mirrors and passes through the PEM element, thereby emitting light of a desired wavelength.

Patent document 1: japanese patent laid-open No. 2014-142422

Patent document 2: japanese laid-open patent publication No. 2009-265195

If the extracted wavelength can be variably controlled using such an etalon, a light source for performing wavelength scanning, for example, can be configured. However, in the configuration disclosed in patent document 1, since the wavelength of light is determined according to the distance between the wavelength conversion element and the optical member, at least one of these members needs to be mechanically moved in order to control the wavelength. Therefore, the wavelength cannot be controlled at high speed by this configuration.

On the other hand, in the configuration disclosed in patent document 2, since the polarization state of each wavelength is controlled by the strain of the PEM element, it is necessary to provide a plurality of polarizers for the purpose of performing the light splitting. Therefore, the number of parts increases, and precise adjustment of these parts becomes difficult.

Disclosure of Invention

The present invention has been made in view of such circumstances, and an object thereof is to provide a spectroscope, an imaging device, a scanning device, and a position measuring device capable of controlling the wavelength of light at high speed and with high accuracy.

The present invention provides a spectrometer having a piezoelectric member that has a first main surface and a second main surface facing each other in parallel, and that periodically varies a distance between the first main surface and the second main surface by a piezoelectric effect by applying an alternating voltage, wherein the piezoelectric member causes light incident on the piezoelectric member to be multiply reflected between the first main surface and the second main surface, and emits light having a wavelength that varies in accordance with variation in the distance between the first main surface and the second main surface.

According to the present invention, a spectrometer, an imaging device, a scanning device, and a position measuring device capable of controlling the wavelength of light at high speed and with high accuracy can be provided.

Drawings

Fig. 1 is a diagram showing a spectroscope 1 according to an embodiment of the present invention.

Fig. 2 is a sectional view taken along line II-II of fig. 1.

Fig. 3 is a diagram for explaining the principle of extracting a desired wavelength component by the etalon.

Fig. 4A is a diagram showing the combination of light in the case where the forward wave and the reflected wave are in phase.

Fig. 4B is a diagram showing light combination in the case where the forward wave and the reflected wave are in opposite phases.

Fig. 5 is a graph showing the relationship between the transmittance of the etalon and the wavelength.

Fig. 6 is an image showing the appearance of a standing wave in the case where the thickness of the quartz plate 10 is three times the half wavelength.

Fig. 7A is a graph showing a simulation result of the light transmittance in the spectroscope 1.

Fig. 7B is a graph showing the simulation result of the light transmittance in the spectroscope 1.

Fig. 8 is a diagram showing a modification of the optical splitter 1 according to the embodiment of the present invention.

Fig. 9 is a diagram showing a modification of the optical splitter 1 according to the embodiment of the present invention.

Fig. 10 is a diagram showing a modification of the spectroscope 1 according to the embodiment of the present invention.

Fig. 11 is a diagram showing a modification of the optical splitter 1 according to the embodiment of the present invention.

Fig. 12A is a cross-sectional view of a quartz plate on which a pair of electrode films is formed.

Fig. 12B is a cross-sectional view of a quartz plate on which two pairs of electrode films are formed.

Fig. 13 is a diagram showing a modification of the optical splitter 1 according to the embodiment of the present invention.

Fig. 14 is a diagram showing a laser device to which a beam splitter according to an embodiment of the present invention is applied.

Fig. 15 is a diagram showing an inspection apparatus to which a spectroscope according to an embodiment of the present invention is applied.

Fig. 16 is a diagram showing an inspection apparatus to which a spectroscope according to an embodiment of the present invention is applied.

Fig. 17 is a diagram showing an imaging device to which a spectroscope according to an embodiment of the present invention is applied.

Fig. 18 is a diagram showing a scanning device to which a spectroscope according to an embodiment of the present invention is applied.

Fig. 19A is a diagram showing a position measuring apparatus to which a spectroscope according to an embodiment of the present invention is applied.

Fig. 19B is a diagram showing a position measuring apparatus to which a spectroscope according to an embodiment of the present invention is applied.

Fig. 19C is a diagram showing a position measuring apparatus to which a spectroscope according to an embodiment of the present invention is applied.

Fig. 20A is a timing chart of the wavelength of light transmitted through the spectroscopes 1, 2 and the detection signal in the detector 530.

Fig. 20B is a timing chart of the wavelength of light transmitted through the spectroscopes 1, 2 and the detection signal in the detector 530.

Fig. 20C is a timing chart of the wavelength of light transmitted through the spectroscopes 1, 2 and the detection signal in the detector 530.

Detailed Description

Embodiments of the present invention will be described below. In the following description of the drawings, the same or similar components are denoted by the same or similar reference numerals. The drawings are for illustrative purposes, and the size and shape of each part are schematic, and the technical scope of the present invention should not be construed as being limited to the embodiment.

A spectrometer according to an embodiment of the present invention will be described with reference to fig. 1 and 2. Fig. 1 is a diagram showing a spectroscope 1 according to an embodiment of the present invention, and fig. 2 is a sectional view taken along line II-II of fig. 1.

The spectrometer 1 is a device for extracting light of a desired wavelength from light of a wide frequency band and outputting the light. As shown in fig. 1, the spectrometer 1 includes a Quartz plate 10(Quartz Crystal Element), a pair of

reflection films

20 and 21 formed on the Quartz plate 10, and an ac power supply 30 for applying an ac voltage to the Quartz plate 10.

The quartz plate 10 is a specific example of the piezoelectric member constituting the spectrometer 1. In the present embodiment, the quartz plate 10 is formed of a quartz substrate of cut artificial quartz (so-called X-cut) in which a surface parallel to a plane defined by the Y axis and the Z axis (optical axis) among the X axis, the Y axis, and the Z axis, which are crystal axes of the artificial quartz, is cut out as a main surface. The X, Y, and Z axes are orthogonal to each other, and the normal line of the principal surface of the quartz plate is along the X axis. In a quartz plate using a quartz substrate subjected to X-cutting, a stretching vibration mode is often used as a main vibration. Hereinafter, each configuration of the spectrometer 1 will be described with reference to the axial direction of the crystal axis.

The quartz plate 10 has a flat plate shape having two main surfaces facing each other in parallel. Specifically, the quartz plate 10 has a main surface 11 (first main surface) on the positive X-axis direction side and a main surface 12 (second main surface) on the negative X-axis direction side. The

main surfaces

11 and 12 have a substantially rectangular shape having long sides parallel to the Z axis and short sides parallel to the Y axis in a plan view. In addition, the quartz plate 10 has a thickness parallel to the X-axis. In the following description, the thickness parallel to the X axis is also referred to simply as "thickness". In the present specification, a description is given of an embodiment in which the long sides, short sides, and sides in the thickness direction of the quartz plate 10 are parallel to the respective corresponding crystal axes as an example, but the present invention is not limited to this, and the embodiment is not limited to an embodiment in which the respective sides of the quartz plate 10 extend along the axes, and are strictly parallel to the axes. For example, the long side, the short side, and the side in the thickness direction may be rotated by about ± 5 degrees from each crystal axis.

One reflective film 20 (first reflective film) is formed on the principal surface 11 of the quartz plate 10, and the other reflective film 21 (second reflective film) is formed on the principal surface 12. The pair of

reflection films

20 and 21 are arranged to face each other so as to overlap substantially the entire quartz sheet 10. Here, since the pair of

reflective films

20 and 21 are respectively formed on the principal surfaces 11 and 12 of the quartz plate 10 and the principal surface 11 of the quartz plate 10 is parallel to the principal surface 12, the reflective film 20 and the reflective film 21 are similarly arranged in parallel.

In the present embodiment, each of the pair of

reflection films

20 and 21 also functions as an excitation electrode for vibrating the quartz piece 10 by the piezoelectric effect. That is, the

reflective films

20 and 21 are films formed of a conductive member, and include, for example, electrode films. When an ac voltage is applied from the ac power supply 30 to the

reflection films

20 and 21, the quartz piece 10 periodically vibrates at a high frequency (for example, MHz band) in a predetermined vibration mode such as a stretching vibration mode by the piezoelectric effect. Due to this vibration, the thickness d of the quartz plate 10 (i.e., the distance between the main surfaces 11 and 12) periodically fluctuates. Therefore, the distances between the

reflective films

20 and 21 formed on the

main surfaces

11 and 12, respectively, also periodically vary in the same manner. Further, since the

reflective films

20 and 21 also serve as excitation electrodes, the number of manufacturing steps can be reduced as compared with a configuration in which the reflective films and the excitation electrodes are provided separately.

As shown in fig. 2, in the spectrometer 1, incident light Li is incident from an incident portion 13, which is a region of the main surface 11 of the quartz plate 10. Here, for simplicity, it is assumed that the incident light Li vibrates in the paper surface. The incident light Li is reflected between the reflective film 20 and the reflective film 21a plurality of times (for example, several tens of times) and passes through the inside of the quartz plate 10, and is emitted as the emission light Lo from the emission portion 14, which is a region of the main surface 12 of the quartz plate 10. In fig. 2, the incident light Li is incident with an optical axis inclined with respect to the main surface 12 (i.e., not orthogonal to the main surface 12), and the outgoing light Lo is emitted with an optical axis inclined with respect to the main surface 11 (i.e., not orthogonal to the main surface 11). Next, before explaining the effect of the variation in thickness of the quartz plate 10 in the optical splitter 1, a principle of extracting a desired wavelength component from incident light including a wavelength component in a wide band in a general etalon will be explained.

Fig. 3 is a diagram for explaining the principle of extracting a desired wavelength component by the etalon. Fig. 4A is a diagram showing the combination of light in the case where the forward wave and the reflected wave are in phase, and fig. 4B is a diagram showing the combination of light in the case where the forward wave and the reflected wave are in opposite phase.

As shown in fig. 3, the incident light includes light of various wavelengths. While the incident light is multiply reflected by the reflecting surfaces arranged in parallel and facing each other, the forward wave and the reflected wave are repeatedly superimposed. Thus, as shown in fig. 4A, when the forward wave and the reflected wave are in phase, the intensity of light increases due to the superposition, and a standing wave is generated. On the other hand, when the phases of the traveling wave and the reflected wave are shifted to have opposite phases as shown in fig. 4B, the lights cancel each other out due to the overlapping. Therefore, light having a wavelength in which the phases of the forward wave and the reflected wave are in the same phase is selectively extracted and emitted as output light. Here, when the phase of the forward wave and the phase of the reflected wave are the same as each other, and when the integral multiple of the half wavelength of the light is equal to the distance G between the reflecting surfaces, the light intensity does not cancel each other out even after the multiple reflections. Thus, the etalon functions as a band pass filter for extracting light having a wavelength λ equal to an integral multiple of a half wavelength and a distance G (that is, satisfying n λ/2 ═ G (n: natural number, λ: wavelength)).

Fig. 5 is a graph showing the relationship between the transmittance of the etalon and the wavelength. In the figure, the horizontal axis represents wavelength and the vertical axis represents transmittance. As described above, the etalon transmits light whose distance between the reflecting surfaces is an integral multiple of a half wavelength. Therefore, the etalon has a characteristic in which transmittance periodically increases with respect to the wavelength. As shown in FIG. 5, the peak value of the transmittance and the interval between the peak values are referred to as FSR (Free-Spectral Range). When the etalon scans the wavelength of the incident light, the etalon is preferably designed such that the frequency band of the incident light is included in the frequency band of the FSR. This allows light of a unique wavelength to be extracted.

In the spectrometer 1 of the present embodiment, a desired wavelength component can be extracted by the same principle as the etalon described above. Further, according to the spectrometer 1, the extracted wavelength can be variably controlled by varying the thickness of the quartz plate 10. Next, the variable control of the wavelength will be described.

Fig. 6 is an image showing the appearance of a standing wave in the case where the thickness of the quartz plate 10 is three times the half wavelength. According to fig. 6, when the thickness of the quartz plate 10 is changed from d1 to d2, the optical path length of light is changed, and thus the wavelength of the generated standing wave is changed from λ 1 to λ 2. From this, it is understood that the wavelength of light extracted by the spectroscope 1 changes due to the change in the thickness of the quartz plate.

Fig. 7A and 7B are graphs showing simulation results of light transmittance in the spectroscope 1. In the figure, the horizontal axis represents wavelength (nm) and the vertical axis represents transmittance (ratio). Further, fig. 7B shows the simulation result in the case where the thickness of the quartz plate 10 is thickened from 100 μm to 100.1 μm as compared with fig. 7A.

As is clear from comparison between fig. 7A and 7B, increasing the thickness of the quartz plate 10 increases the wavelength at which the transmittance becomes a peak. Thus, it can be said that the wavelength λ of the extracted outgoing light Lo can be periodically varied by periodically varying the thickness d of the quartz plate 10.

As described above, according to the spectrometer 1, the thickness of the quartz plate 10 is periodically varied by the piezoelectric effect, and thus the distance between the reflection film 20 and the reflection film 21, that is, the optical path length of the light transmitted through the inside of the quartz plate 10 is periodically varied. This makes it possible to vary the wavelength of the emitted light Lo at the same frequency as the vibration of the quartz plate 10 (for example, several MHz or so). Therefore, for example, as in the configuration disclosed in patent document 1, since it is not necessary to mechanically move the components of the apparatus, the wavelength can be controlled at high speed.

Further, for example, in the configurations disclosed in patent documents 1 and 2, it is necessary to maintain the parallelism between the components of the apparatus or to precisely adjust a plurality of polarizers and mirrors, and it is difficult to maintain all the component accuracies. In this regard, according to the spectrometer 1, if the parallelism of the principal surfaces 11 and 12 (i.e., light reflecting surfaces) of the quartz plate 10 is ensured, the optical path length can be varied while maintaining the parallelism of the interface. Therefore, according to the optical splitter 1, adjustment of components and the like is not necessary, and light can be split stably and accurately with respect to disturbance.

In the configuration disclosed in patent document 2, since the transmitted light is refracted multiple times at the interface having different refractive indices, stray light is generated at each refraction, resulting in a loss of light amount. In this regard, in the spectroscope 1, since the number of interfaces is two as described above, loss of light amount can be suppressed compared to the configuration disclosed in patent document 2.

Further, the spectrometer 1 requires a smaller number of parts than the configurations disclosed in patent documents 1 and 2, and therefore can be downsized.

In addition, quartz used as the piezoelectric member in the present embodiment has the following three characteristics. First, since quartz has a lower refractive index than other piezoelectric members, it is possible to suppress variations in characteristics due to changes in the undesired shape of the quartz piece. Therefore, for example, even if the quartz piece expands due to a temperature change, deterioration of spectroscopic performance can be suppressed, and resistance to a change in external environment can be improved. In order to secure the FSR corresponding to the incident light in a wide band, the thickness of the member needs to be reduced as the refractive index of the member is increased. In this regard, according to quartz, even when it is compatible with incident light in a wide band, the thickness can be increased compared with other members. Therefore, according to the present embodiment, workability and strength can be ensured as compared with a configuration using another piezoelectric member.

The second is that quartz responds faster to variations in ac voltage than other piezoelectric components. Therefore, according to the present embodiment, the wavelength can be controlled at a higher speed than in a configuration using another piezoelectric member.

The third is that quartz is transparent over a wider wavelength band than other piezoelectric components. Further, even when the wavelength of light is relatively short and the energy is strong, the optical characteristics of quartz are not easily damaged and deterioration progresses slowly. Therefore, according to the present embodiment, for example, light having a wavelength from ultraviolet to infrared can be transmitted.

In addition, in the present embodiment, the quartz plate 10 is X-cut and vibrates in the stretching vibration mode. Therefore, the vibration of about MHz can be easily excited, and the spectral bandwidth can be increased compared to other vibration modes.

In the above-described embodiment, the case where the quartz piece is X-cut and vibrated in the stretching vibration mode has been described, but the cut angle and the vibration mode of the quartz piece are not limited thereto. For example, the quartz plate may be formed of a quartz substrate that is cut (so-called GT cut) by cutting a plane parallel to a plane defined by the X "axis and the Z" axis as a main plane, with axes obtained by rotating the Y axis and the Z axis of the X axis, the Y axis, and the Z axis of the crystal axis of the artificial quartz by about 51 degrees around the X axis from the direction of the Y axis to the Z axis as the X 'axis, the Y' axis, and the Z 'axis, and axes obtained by further rotating the X' axis and the Z 'axis by about 45 degrees around the Y' axis from the direction of the Z 'axis to the X' axis as the X "axis, the Y" axis, and the Z "axis, respectively. In such GT dicing, the normal line of the main surface has an inclination of about 39 degrees with respect to the Z axis. In this case, the amount of variation in the thickness of the quartz piece (and hence the bandwidth of the wavelength of the emitted light) is smaller than in the X-cut, and temperature stability can be obtained. Therefore, the tolerance to environmental fluctuations can be improved as compared with X-cutting.

In the case of using a GT-cut quartz plate, the symmetry between the two main surfaces in the traveling direction and the axial direction of light is broken, and therefore, it is also considered that the optical path lengths of the outgoing path and the return path are different due to the influence of birefringence. However, the same effects as in the above-described embodiment can be obtained because the polarization and phase of the reciprocating light match when the optical path lengths of the reciprocating light match. Further, a known method can be used as a method of calculating the optical path length (see, for example, japanese patent laid-open No. 2008-076120), and therefore, description thereof is omitted.

The quartz piece may be formed of a quartz substrate cut out by another cutting such as so-called AT cutting. The material of the piezoelectric member is not limited to quartz, and may be made of a material different from quartz.

In the above-described embodiment, the

reflective films

20 and 21 have the function of exciting electrodes, and an example in which an ac voltage is applied to the

reflective films

20 and 21 is shown, but the means for applying an ac voltage is not limited to this. For example, the spectrometer 1 may be provided with excitation electrodes for applying an ac voltage independently of the

reflection films

20 and 21 for multiply reflecting light.

The spectrometer 1 may be provided with an antireflection film for reducing the reflectance of either or both of the incident portion 13 of the incident light and the emission portion 14 of the emitted light, or may be provided with a reflection film for improving the reflectance. These can be designed appropriately according to, for example, the amount of incident light Li incident from the light source and the amount of light necessary as the emitted light Lo.

Next, a spectrometer according to a modification of the present embodiment will be described with reference to fig. 8 to 13. Fig. 8 to 11 and fig. 13 are views showing modifications of the spectroscope 1 according to the embodiment of the present invention. In the following description, the same elements as those of the spectroscope 1 are denoted by the same reference numerals, and description thereof is omitted. Note that the description of the same items as those of the spectroscope 1 is omitted, and only the differences will be described. In particular, the same operational effects due to the same configurations are not mentioned in turn for each embodiment.

The spectroscope 1A shown in fig. 8 is arranged such that side surfaces 15 and 16 between the principal surface 11 and the principal surface 12 of the quartz piece 10a are inclined with respect to the

principal surfaces

11 and 12.

Specifically, the side surface 15 on one side (positive direction side) of the quartz piece 10a in the Z-axis direction is an inclined surface (first inclined surface) inclined with respect to the principal surface 11. The side surface 16 on the other side (negative side) in the Z-axis direction of the quartz plate 10a is an inclined surface (second inclined surface) inclined with respect to the principal surface 12. These side surfaces 15 and 16 are disposed at positions facing each other between the

main surfaces

11 and 12.

In the spectrometer 1A, incident light Li enters from the side surface 15, and light Lo exits from the side surface 16. Thus, even if light enters the side surface 15 perpendicularly, for example, the light enters the main surface 12 of the quartz piece 10a obliquely (i.e., not orthogonally). Therefore, light incident on the quartz plate 10a from the light source (not shown) is prevented from being reflected by the reflective film 21a and returned to the light source again, and therefore damage and noise to the light source can be suppressed.

In the case where light enters and exits from a surface different from the light reflection surface as in the spectroscope 1A, the reflection films 20a and 21A may be formed on the entire

main surfaces

11 and 12 of the quartz piece 10 a. The side surfaces 15 and 16 do not necessarily need to be inclined surfaces as a whole, and may be configured to include inclined surfaces in part of the side surfaces, for example, and to allow light to enter and exit from the inclined surfaces.

The spectrometer 1B shown in fig. 9 includes

electrode films

22a and 23a instead of the

reflective films

20 and 21, compared to the spectrometer 1 shown in fig. 1. Similarly, the spectrometer 1C shown in fig. 10 includes

electrode films

22b and 23b instead of the

reflective films

20 and 21.

Specifically, in the spectrometer 1B, the electrode film 22a is formed so as to surround the periphery of the incident portion 17 of the incident light Li located in the central region on the principal surface 11 of the quartz plate 10B. The electrode film 23a is also formed so as to surround the periphery of the emission portion 18 that emits the light Lo on the main surface 12.

Electrode films

22a and 23a face each other via quartz piece 10b, and an ac voltage is applied from ac power supply 30. The incident portion 17 and the emission portion 18 may be coated with a highly reflective coating that transmits part of the light and reflects part of the light.

Even with such a configuration, the thickness of the peripheral region of the quartz piece 10b varies due to the piezoelectric effect, and the thickness of the central region varies with the variation, so that the same effect as that of the spectrometer 1 described above can be obtained.

In this way, the spectroscope does not necessarily have to share the electrode film having the function of vibrating the quartz plate and the reflection film having the function of reflecting the incident light, and may be provided independently of each other. In the

beam splitters

1B and 1C, as in the beam splitter 1A, the main surface may be arranged to be inclined with respect to the traveling direction of the incident light.

The

electrode films

22a and 23a do not necessarily need to surround the central region entirely, and may have a discontinuous portion in a part thereof, such as the

electrode films

22b and 23b shown in fig. 10. Thus, for example, when the

electrode films

22b and 23b are formed on the quartz plate 10c by vapor deposition, the film forming step is facilitated.

The quartz plate 10D of the spectroscope 1D shown in fig. 11 has a circular flat plate shape. In this way, the shape of the quartz plate is not particularly limited, and may be a rectangular flat plate shape, a circular flat plate shape, or a polygonal flat plate shape.

The quartz plate 10d has an annular inner electrode film 24x formed around the incident portion located near the center of the circle on one main surface, and an annular outer electrode film 24y (outer electrode film) formed concentrically so as to surround the outer side of the inner electrode film 24 x. On the other main surface, the inner electrode film 25x and the outer electrode film 25y are also formed to face the inner electrode film 24x and the outer electrode film 24y, respectively. An ac voltage is applied from the ac power supply 31 to the inner electrode films 24x and the inner electrode films 25x, and an ac voltage is applied from the ac power supply 32 to the outer electrode films 24y and the outer electrode films 25 y.

In this way, the electrode films formed on the quartz plate are not limited to one pair, and may be two or more pairs. In this case, alternating voltages having different phases may be applied to the two pairs of electrode films. The effects thereof will be explained.

Fig. 12A is a cross-sectional view of a quartz plate on which a pair of electrode films are formed, and fig. 12B is a cross-sectional view of a quartz plate on which two pairs of electrode films are formed. Fig. 12A and 12B show cross sections in the same direction as in fig. 2, and the electrode films are omitted for convenience of explanation.

As shown in fig. 12A, when an ac voltage is applied to a pair of electrode films partially formed in a plane (for example, electrode films corresponding to the inner electrode films 24x and the inner electrode films 25x shown in fig. 11), the peripheral region of a quartz plate may be thickened and the central region may be thinned due to the piezoelectric effect. This may deteriorate the parallelism of the reflection surface in the region where light is multiply reflected, and may reduce the accuracy of light splitting. On the other hand, as shown in fig. 12B, when ac voltages having mutually opposite phases are applied to the two pairs of electrode films, for example, the quartz plate in the region where the inner electrode films face tends to be thick, while the quartz plate in the region where the outer electrode films face tends to be thin. This suppresses the unevenness in thickness of the quartz plate, and as a result, the parallelism of the reflection surface of the region where light is reflected more than once is improved. Thus, the spectrometer 1D has higher precision of light splitting than a configuration including a pair of electrode films.

In the spectrometer 1D, the case where the quartz piece 10D has a circular flat plate shape was described as an example, but even if the quartz piece has a different shape, two pairs of electrode films may be formed in the same manner. The electrode films formed on the quartz plate are not limited to two pairs, and may be three or more pairs.

In the spectrometer 1E shown in fig. 13, a plurality of

electrode films

26 and 27 and a plurality of highly

reflective films

40 and 41 are formed on the principal surfaces of both quartz plates 10E.

The

electrode films

26 and 27 function as excitation electrodes, and an ac voltage is applied from an ac power supply 30. The high-

reflection films

40 and 41 are reflection films having a higher reflectance than the principal surface of the quartz piece and the

electrode films

26 and 27. The members of the highly

reflective films

40 and 41 are not particularly limited, but may be, for example, conductive films or dielectric films. In the spectrometer 1E, the plurality of electrode films 26 and the plurality of highly reflective films 40 are alternately arranged along the light traveling direction (Z-axis direction) on one principal surface of the quartz plate 10E. Similarly, the plurality of electrode films 27 and the plurality of highly reflective films 41 are alternately arranged along the light traveling direction (Z-axis direction) on the other principal surface of the quartz plate 10 e.

Thus, in the spectrometer 1E, the

electrode films

26 and 27 and the high-

reflection films

40 and 41 are used in combination, so that loss of the light amount due to multiple reflection can be suppressed and attenuation of the light amount of the emitted light Lo can be suppressed, as compared with a configuration without the high-

reflection films

40 and 41.

The above-described spectroscopes 1A to 1E are one example of a modification of the spectroscope 1, and the configuration of the present invention is not limited to this. For example, although the electrode film is provided on a part of the principal surface of the quartz plate in the above-described embodiment, the electrode film may be provided on the entire principal surface of the quartz plate. When the electrode film is provided on the entire main surface, the electrode film is preferably made of a material having a property of transmitting and reflecting light of a predetermined wavelength, such as ITO (Indium Tin Oxide).

In the above-described embodiment, the configuration in which the pair of opposing reflection films are formed on the principal surfaces of the quartz plate is shown, but the reflection member that reflects light in multiple may not necessarily be formed directly on the principal surfaces of the quartz plate, and may be disposed on one principal surface side and the other principal surface side. Specifically, for example, the pair of reflecting members may be provided separately from the principal surface of the quartz plate, and may be parallel to and opposed to each other with the quartz plate interposed therebetween. In this case, the incident light entering the beam splitter passes through the quartz plate a plurality of times, and multiple reflection is performed between the reflecting members.

Next, an application example of the spectroscope 1 according to an embodiment of the present invention will be described with reference to fig. 14 to 17.

Fig. 14 is a diagram showing a laser device to which a beam splitter according to an embodiment of the present invention is applied. The laser device 100 shown in the figure includes a beam splitter 1, a laser diode 110, a lens 120, an optical fiber 130, and an amplifier 140. Although fig. 14 illustrates the configuration of the beam splitter 1B, the beam splitter to which the laser device 100 is applied is not particularly limited. The same applies to the following application examples.

In the laser device 100, light emitted from a laser diode 110 as a light source is split by a beam splitter 1, and the split light is output via a lens 120 and an optical fiber 130. The Amplifier 140 is a device for amplifying the light amount, and is configured by, for example, an SOA (Semiconductor Optical Amplifier). In order to compensate for the loss of the light amount, the laser device 100 may include a plurality of amplifiers 140 and amplify the light amount a plurality of times. The amplifier 140 may be disposed at a position subsequent to the optical splitter 1 or may be disposed at a position prior to the optical splitter 1.

By applying the beam splitter 1 to the laser device 100, a laser device capable of variable control of the wavelength at high speed can be realized as described above.

Fig. 15 is a diagram showing an inspection apparatus to which a spectroscope according to an embodiment of the present invention is applied. The inspection apparatus 200 shown in the figure includes a spectrometer 1, a plurality of light sources 210,

lenses

220 and 230, and a detector 240 (imaging device).

In the inspection apparatus 200, light emitted from the plurality of light sources 210 to the object W on the conveyor is incident on the spectroscope 1 via the lens 220. Then, the light split by the beam splitter 1 is input to the detector 240 via the lens 230.

Here, if the inspection apparatus does not include the spectroscope 1, it is necessary to simultaneously detect light of a plurality of wavelengths (for example, red, yellow, green, blue, and the like) by the detector 240. Therefore, in the inspection of the color of the object W, it is necessary to use an imaging element having a plurality of pixels as the detector 240 and to provide a mechanism for assigning colors to the respective pixels. For example, this is constituted by a lens, a grating, or a color filter arranged directly above each pixel, but increasing the number of pixels for improving the spectral performance is not an option to increase the size. On the other hand, in order to miniaturize the device, the pixel pitch of the imaging element of the detector 240 must be reduced to lower the sensitivity, and a long exposure time is required. That is, in this case, high-speed light splitting cannot be performed. In particular, when a grating is used, the pixel pitch becomes small, and crosstalk noise between signals due to adjacent wavelengths is likely to occur, and thus the tendency becomes remarkable.

In this regard, since the inspection apparatus 200 includes the spectroscope 1, light whose wavelength fluctuates at a high frequency can be supplied to the probe 240. This enables the light incident on the detector 240 to be changed as appropriate over time, as in red, yellow, green, blue, red, and the like. Since the light is split by the beam splitter 1, the number of pixels required is small compared to a configuration in which light of a plurality of wavelengths is simultaneously supplied to the detector 240. As a result, the area per pixel can be increased to achieve high sensitivity, and the exposure time can be shortened. Further, if the number of pixels is small, high-speed reading can be performed. In this way, since the wavelength of the spectroscope 1 can be changed at high speed and the detector 240 can detect light at high speed, the color of the moving object W can be inspected at high speed by the conveyor as compared with a configuration without the spectroscope 1. In addition, since the interference between wavelengths can be suppressed by the optical splitter 1, the occurrence of crosstalk between signals can be avoided. The detector 240 may be a single-pixel detector, or may perform a combination process of collectively processing a plurality of pixels into one pixel, for example.

Fig. 16 is a diagram showing an inspection apparatus to which a spectroscope according to an embodiment of the present invention is applied. The inspection apparatus 300 shown in the figure is configured to move instead of the object W and scan the stationary object W with light, as compared with the inspection apparatus 200 shown in fig. 15. Specifically, the inspection apparatus 300 further includes a lens 310, a polarizing beam splitter 320, and a scanner 330, compared to the inspection apparatus 200.

In the inspection apparatus 300, light irradiated from the light source 210 is incident on the scanner 330 via the lens 310 and the polarizing beam splitter 320. The scanner 330 is a device that includes one or more mirrors and scans light by operating the mirrors, and is configured by, for example, a two-dimensional galvano mirror. The light emitted from the scanner 330 and irradiated to the object W via the lens 220 is incident on the beam splitter 1 via the lens 220, the scanner 330, and the polarization beam splitter 320 again. The light split by the beam splitter 1 is input to the detector 240 via the lens 230.

In this way, even when the object W is stationary, the color of the object W can be detected by scanning light with the scanner 330. Further, a one-dimensional galvano mirror may be used as the scanner 330, and a plurality of detectors 240 may be provided.

The beam splitter 1 may not be disposed in front of the detector 240, and may be disposed between the light source 210 and the lens 310, for example. In this case, the amount of light irradiated to the object decreases due to the loss of the amount of light in the spectroscope 1. Therefore, the present invention can suitably function in the case of an object that is difficult to be irradiated with strong light, such as in the case of biological observation. Further, the spectroscope 1 may be inserted into both the rear stage of the light source 210 and the front stage of the detector 240, and the plurality of spectroscopes 1 may be operated in synchronization with each other. Accordingly, compared to a configuration in which the spectroscope 1 is inserted into either one of the two, sharper wavelength selectivity can be obtained, and light can be dispersed with higher resolution. In the above-described embodiment, the light source 210 emits visible light for the sake of simplicity, but the wavelength of light emitted by the light source 210 is not limited to visible light. For example, by using a light source that irradiates light having a near-infrared wavelength with deep reach, the inspection device can also be used for inspecting the interior of the coating surface.

Next, a configuration example of an imaging device in a case where the spectrometer 1 is used as a wavelength scanning light source will be described with reference to fig. 17.

Fig. 17 is a diagram showing an imaging device to which a spectroscope according to an embodiment of the present invention is applied. The imaging device 400 shown in the figure is an example of an optical tomographic imaging device that images an optical tomographic image of a living body, for example. Specifically, the imaging apparatus 400 includes the spectroscope 1, the light source 410, the measurement optical system 420, the reference optical system 430, the detector 440, the timing control system 450, and the signal processing system 460.

The spectroscope 1 performs wavelength scanning on the wide-band light incident from the light source 410 and emits the light. The measurement optical system 420 measures the object W using a part of the light emitted from the spectroscope 1. The reference optical system 430 uses the other part of the light emitted from the beam splitter 1 as reference light. The probe 440 detects measuring interference light based on the reflected light from the object W and the reference light from the reference optical system 430, and outputs a measuring interference signal to the signal processing system 460. The detector 440 is constituted by a balanced type photodetector, for example.

The timing control system 450 transmits a trigger signal corresponding to the wavelength of the light emitted from the optical splitter 1 to the signal processing system 460, and controls the arithmetic processing of the signal processing system 460. Specifically, the timing control system 450 includes the FBG451, the circulator 452, and the detector 453. The FBG (Fiber bragg grating) 451 has a property of reflecting only a predetermined wavelength component (so-called bragg wavelength) of incident light and transmitting the other wavelength component. Therefore, when the output light of the spectrometer 1 is supplied to the FBG451, the reflected light is emitted from the FBG451 when the bragg wavelength component of the FBG451 is incident thereon. The reflected light is supplied to the detector 453 through the circulator 452. The detector 453 detects the reflected light and transmits a trigger signal to the signal processing system 460, thereby controlling arithmetic processing in the signal processing system 460.

The signal processing system 460 performs arithmetic processing based on the measurement interference signal transmitted from the probe 440 and the trigger signal transmitted from the timing control system 450, and outputs a cross-sectional image of the object W. In this way, according to the imaging device 400, it is possible to obtain an image of the object W while controlling the wavelength of the light irradiated to the object W.

In general, optical tomographic imaging apparatuses are often used under in-vivo conditions, and therefore, in order to suppress artifacts (virtual images) caused by movement of a living body, which is an object, or to repeatedly image the same region, it is required to perform wavelength scanning of a light source at high speed. Therefore, the spectroscope 1 functions appropriately in such an optical tomographic imaging apparatus.

The configuration of the timing control is not limited to the configuration shown in fig. 17. For example, instead of providing the timing control system 450, the imaging apparatus 400 may include an FBG interposed between the measurement optical system 420 and the probe 440. In this case, the light detected by the detector 440 is interrupted only when the wavelength of the light incident from the measurement optical system 420 matches the bragg wavelength. The wavelength of the light emitted from the spectrometer 1 can be detected based on the timing of the interruption.

Instead of providing the timing control system 450, the imaging apparatus 400 may include a control device that synchronously controls the light emission timings of the detector 440 and the light source 410. This allows light of a desired wavelength to be irradiated to the object W. Alternatively, the imaging device 400 may include a detector for detecting the wavelength of the light emitted from the spectrometer 1 instead of the timing control system 450. The detector may be a detector that outputs light having a predetermined wavelength and detects a beat signal with respect to the light emitted from the spectrometer 1, thereby detecting the wavelength of the light emitted from the spectrometer 1.

The imaging device using the spectrometer 1 is not limited to this. For example, the present invention can be applied to an optical tomographic imaging apparatus for obtaining a tomographic image of the cornea, retina, or the like of an eye (see japanese patent application laid-open No. 2017-201257), a fluorescence diagnostic apparatus for detecting fluorescence contained in a living body as an image to diagnose a disease state such as degeneration or cancer of a living tissue (see japanese patent application laid-open No. 2005-305182), and the like.

Fig. 18 is a diagram showing a scanning device to which a spectroscope according to an embodiment of the present invention is applied. The scanner 500 shown in the figure includes a beam splitter 1, a light source 510, and a prism 520.

In the scanning device 500, the broadband light emitted from the light source 510 is split by the beam splitter 1, and is further refracted by the prism 520 at different refractive indices according to the wavelength and emitted. In this way, according to the scanning device 500, the light temporally dispersed by the spectroscope 1 is spatially dispersed by the prism 520, and therefore, light for scanning a certain area can be emitted at high speed and periodically. Such a scanning device 500 can be applied to a scanner for spatially scanning light from a light source, for example, in LIDAR (light detection and Ranging) or the like described below. The spectroscopic element that spatially disperses light in the scanning device 500 is not limited to a prism, and may be, for example, a grating. This is also the same in the position measuring apparatus 600 described below.

Fig. 19A to 19C are diagrams showing a position measuring apparatus to which a spectroscope according to an embodiment of the present invention is applied. The position measuring apparatus 600 shown in fig. 19A to 19C includes a beam splitter 2 and a detector 530, which are configured in the same manner as the beam splitter 1, in addition to the scanning apparatus 500 described above.

The spectroscope 2 transmits reflected light that is emitted at different angles according to the wavelength by the scanning device 500 and reflected by the object X. The detector 530 receives and detects the reflected light transmitted through the beam splitter 2. That is, in the position measuring apparatus 600, the spectroscope 1 (first spectroscope) has a function of periodically varying the wavelength of the emitted light, and the spectroscope 2 (second spectroscope) has a function of a filter that transmits light having a specific wavelength among the reflected light.

Specifically, fig. 19A shows how light having a certain wavelength is reflected by the object X at the point a. Fig. 19B shows a case where the object X at the point B located closer to the position measurement device 600 than the point a reflects light having the same wavelength as that of the point a. Fig. 19C shows how light having a wavelength different from that in the case of the point a and the point B is reflected by the object X at the point C located at a different azimuth from the point a and the point B. In either case, the distance to the object X can be calculated by a so-called Time of Flight (Time of Flight) method based on the difference between the emission Time of light emitted from the light source 510 and the detection Time of reflected light reflected by the object X detected by the detector 530. The principle of this will be explained below.

Fig. 20A to 20C are timing charts of the wavelength of light transmitted through the spectroscopes 1 and 2 and the detection signal in the detector 530 in the situation shown in fig. 19A to 19C, respectively. For the sake of simplicity, light of three wavelengths (wavelength 1 to wavelength 3) is emitted from the prism 520.

In the position measuring apparatus 600, the spectroscope 1 on the light source side and the spectroscope 2 on the detection side are synchronously controlled. Specifically, as shown in fig. 20A to 20C, the vibration frequency of the piezoelectric element of the spectrometer 2 on the detection side (i.e., the frequency of the wavelength fluctuation of the transmitted light of the spectrometer 2) is controlled to be higher than the vibration frequency of the piezoelectric element of the spectrometer 1 on the light source side (i.e., the frequency of the wavelength fluctuation of the transmitted light of the spectrometer 1). This allows selective detection of light having a specific wavelength.

Specifically, for example, when the object X is at the point a (see fig. 19A), the light having the wavelength 3 emitted at the time t1 is reflected by the object X. The reflected light reaches the beam splitter 2, and is supplied to the detector 530 in a state where the beam splitter 2 transmits light of the wavelength 3. And the detection signal in detector 530 indicates that light was detected at time t 2. Thus, the distance d from the position measuring device 600 to the object X can be calculated from d ═ c (t 2-t 1)/2(c is the speed of light). Since the light is emitted at different angles depending on the wavelength by the prism 520, the light of the wavelength 1 and the light of the wavelength 2 do not irradiate the object X and do not return to the reflected light.

Similarly, for example, when the object X is at the point B (see fig. 19B), the light of the wavelength 3 emitted at the time t1 is reflected by the object X, and the reflected light reaches the spectroscope 2, and is supplied to the detector 530 in a state where the spectroscope 2 transmits the light of the wavelength 3. Thus, the detection signal in detector 530 indicates that light was detected at time t 2. In this case, the light of the wavelength 1 and the wavelength 2 does not irradiate the object X and does not return the reflected light.

On the other hand, for example, when the object X is at the point C (see fig. 19C), the light of the wavelength 2 emitted at the time t1 is reflected by the object X, and the reflected light reaches the spectroscope 2, and is supplied to the detector 530 in a state where the spectroscope 2 transmits the light of the wavelength 2. Thus, the detection signal in detector 530 indicates that light was detected at time t 2. In this case, the light of the wavelength 1 and the wavelength 3 does not irradiate the object X and does not return the reflected light. In this way, in the position measuring apparatus 600, the direction of the position where the object is located can be measured based on the wavelength of the reflected light detected by the detector 530. In addition, when spatial scanning is performed using a prism as described above, the wavelength can be converted into an angle using the law of refractive index dispersion and refraction (snell's law) of the glass material constituting the prism.

As described above, according to the position measuring device 600, the distance d from the position measuring device 600 to the object can be calculated based on the difference between the time t1 and the time t 2. In addition, according to the position measuring apparatus 600, it is possible to calculate the direction in which the object X is located based on the wavelength of the light detected by the detector 530. That is, according to the position measurement device 600, for example, compared to a LIDAR in which a light source or a mirror is rotated to expand an emission area of emitted light, since it is not necessary to mechanically move components of the device, it is possible to perform measurement at high speed and with high accuracy. Further, in the above, an example of two-dimensional scanning is shown for simplicity, but three-dimensional scanning can be realized by using a plurality of prisms, or using a hologram element.

The above description has been made of exemplary embodiments of the present invention. The optical splitter of the present embodiment includes a piezoelectric member having a first main surface and a second main surface facing each other in parallel, the piezoelectric member periodically varying by a piezoelectric effect by applying an alternating voltage, the piezoelectric member multiply reflecting light incident on the piezoelectric member between the first main surface and the second main surface and emitting light having a wavelength varying according to variation in the distance between the first main surface and the second main surface.

Accordingly, since the optical path length of light is varied by the piezoelectric effect, it is not necessary to mechanically move the components of the device, and the wavelength can be variably controlled at high speed. Further, since the optical path length can be varied while maintaining the parallelism between the first main surface and the second main surface of the piezoelectric member, adjustment of members and the like is not necessary, and light can be dispersed stably and accurately against disturbance.

In the above configuration, the spectrometer 1 further includes a first reflection film provided on the first main surface side and a second reflection film provided on the second main surface side, and the piezoelectric member causes light to be multiply reflected between the first reflection film and the second reflection film.

Accordingly, the reflectance is improved as compared with a configuration without a reflective film, and thus loss of light quantity can be suppressed.

In the above configuration, each of the first reflective film and the second reflective film may include an electrode film to which an ac voltage is applied.

Accordingly, the reflective film also serves as an excitation electrode, and thus the number of manufacturing steps can be reduced.

In the above configuration, each of the first reflective film and the second reflective film may include a high reflective film having a higher reflectance than the electrode film.

This can suppress loss of the light amount due to multiple reflection, and suppress attenuation of the light amount of the emitted light.

In the above configuration, the first reflective film and the second reflective film may include an inner electrode film and an outer electrode film, respectively, the outer electrode film being provided so as to surround an outer side of the inner electrode film when viewed from the first main surface or the second main surface, and the inner electrode film and the outer electrode film may be applied with alternating voltages having mutually opposite phases.

This suppresses unevenness in thickness of the quartz plate, and improves the parallelism of the reflection surface in the region where light is multiply reflected, thereby improving the precision of light splitting.

In the above configuration, the piezoelectric member may further include a first inclined surface inclined with respect to the first main surface and a second inclined surface inclined with respect to the second main surface, the first inclined surface and the second inclined surface may be disposed at positions facing each other between the first main surface and the second main surface, and the piezoelectric member may emit light incident from the first inclined surface from the second inclined surface.

Accordingly, light incident from the light source to the piezoelectric member is prevented from being reflected and returned to the light source again, and damage and noise to the light source can be suppressed.

In the above configuration, the piezoelectric member may be made of artificial quartz that is X-cut.

Accordingly, the piezoelectric member vibrates in the stretching vibration mode, and therefore the spectral bandwidth can be increased compared to other vibration modes.

In the above configuration, the piezoelectric member may be made of GT-cut artificial quartz.

Accordingly, temperature stability can be obtained as compared with artificial quartz in which X-cutting is performed. Therefore, the resistance to environmental fluctuations can be improved.

The imaging device of the present embodiment includes the above-described spectroscope, a light source that emits light to the piezoelectric member of the spectroscope, an optical system that irradiates the object with the light emitted from the spectroscope, and an imaging element that receives reflected light reflected by the object.

Thus, a light source capable of performing wavelength scanning at high speed can be provided. Therefore, for example, in an apparatus for capturing an optical tomographic image of a living body, it is possible to suppress artifacts caused by movement of the living body and to improve the capturing accuracy in the case of repeated capturing.

The scanning device of the present embodiment includes the above-described spectroscope, a light source that emits light to the piezoelectric member of the spectroscope, and a spectroscopic element that spatially disperses the light emitted from the spectroscope.

Accordingly, the light temporally dispersed by the spectroscope is spatially dispersed by the spectroscopic element, and therefore, light that periodically scans a certain region at a high speed can be emitted.

The position measuring apparatus according to the present embodiment includes a first spectroscope that transmits incident light as the above-described spectroscope, a light source that emits light to the piezoelectric member of the first spectroscope, a spectroscopic element that spatially disperses the light emitted from the first spectroscope, a second spectroscope that transmits reflected light emitted from the spectroscopic element and reflected by an object as the above-described spectroscope, and a detector that receives the transmitted light transmitted through the second spectroscope.

In this way, the distance from the position measuring device to the object can be calculated based on the difference between the emission time and the detection time. Further, according to this, it is possible to calculate the direction in which the object is located based on the wavelength of the detected light. Therefore, for example, compared to a LIDAR in which a light source or a mirror is rotated, since it is not necessary to mechanically move components of the apparatus, measurement can be performed at high speed and with high accuracy.

In the above configuration, the vibration frequency of the piezoelectric member of the second spectrometer may be higher than the vibration frequency of the piezoelectric member of the first spectrometer.

Thus, light of a specific wavelength can be selectively detected.

The embodiments described above are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention can be modified or improved within a range not departing from the gist thereof, and equivalents thereof are also included in the present invention. That is, as long as the characteristics of the present invention are provided, the embodiment in which design changes are appropriately made to each embodiment by those skilled in the art is also included in the scope of the present invention. For example, the elements provided in the embodiments, and the arrangement, materials, conditions, shapes, sizes, and the like thereof are not limited to those exemplified and can be appropriately changed. In addition, the elements included in the embodiments may be combined as long as they are technically realized, and embodiments in which the elements are combined as long as the features of the present invention are included are also included in the scope of the present invention.

Description of the reference numerals

1. 1A-1E … optical splitter, 10 a-10E … quartz plate, 11, 12 … main surface, 13 … incident part, 14 … emergent part, 15, 16 … side surface, 20a, 21A … reflective film, 22a, 22b, 23a, 23b, 26, 27 … electrode film, 24x, 25x … inner electrode film, 24y, 25y … outer electrode film, 30-32 … AC power supply, 40, 41 … high reflective film, 100 … laser device, 110 … laser diode, 120 … lens, 130 … optical fiber, 140 … amplifier, 200 … inspection device, 210 … light source, 220, 230 … lens, 240 … detector, 300 … inspection device, 310 … lens, 320 … polarized light beam splitter, 36330 scanner, 400 … imaging device, 36410 light source, …, 36420 optical system, 36430 optical system, …, 36440 optical system, …, 36451, … timing control system, 36451, 452 … circulator, 453 … probe, 460 … signal processing system, 500 … scanning device, 510 … light source, 520 … prism, 530 … probe, 600 … position determination device.

Claims

1. A light splitter, wherein,

the piezoelectric element includes a first main surface and a second main surface facing each other in parallel, and a distance between the first main surface and the second main surface is periodically varied by a piezoelectric effect by applying an alternating voltage,

the piezoelectric member causes multiple reflection of light incident on the piezoelectric member between the first main surface and the second main surface, and emits light having a wavelength that varies according to variation in distance between the first main surface and the second main surface.

2. The optical splitter of claim 1,

the beam splitter further includes a first reflection film provided on the first main surface side and a second reflection film provided on the second main surface side,

the piezoelectric member causes light to be multiply reflected between the first reflective film and the second reflective film.

3. The optical splitter of claim 2,

the first reflective film and the second reflective film each include an electrode film to which the ac voltage is applied.

4. The optical splitter of claim 3,

the first reflective film and the second reflective film each include a high reflective film having a higher reflectance than the electrode film.

5. The optical splitter of claim 2,

the first reflective film and the second reflective film each include an inner electrode film and an outer electrode film, the outer electrode film being provided so as to surround an outer side of the inner electrode film when the first main surface or the second main surface is viewed in plan,

alternating voltages having mutually opposite phases are applied to the inner electrode film and the outer electrode film.

6. The beam splitter according to any one of claims 1 to 5,

the piezoelectric member further includes a first inclined surface inclined with respect to the first main surface and a second inclined surface inclined with respect to the second main surface,

the first inclined surface and the second inclined surface are disposed at positions facing each other between the first main surface and the second main surface,

the piezoelectric member emits light incident from the first inclined surface from the second inclined surface.

7. The beam splitter according to any one of claims 1 to 6,

the piezoelectric member includes artificial quartz that is X-cut.

8. The beam splitter according to any one of claims 1 to 6,

the piezoelectric member includes GT-cut artificial quartz.

9. An imaging device is provided with:

the beam splitter according to any one of claims 1 to 8;

a light source that emits light to the piezoelectric member of the spectrometer;

an optical system for irradiating the light emitted from the beam splitter to an object; and

and an imaging element that receives the reflected light reflected by the object.

10. A scanning device is provided with:

the beam splitter according to any one of claims 1 to 8;

a light source that emits light to the piezoelectric member of the spectrometer; and

and a spectroscopic element that spatially disperses the light emitted from the spectroscope.

11. A position measuring apparatus is provided with:

a first beam splitter according to any one of claims 1 to 8, which transmits incident light;

a light source that emits light to the piezoelectric member of the first beam splitter;

a spectroscopic element that spatially disperses the light emitted from the first spectroscope;

a second beam splitter according to any one of claims 1 to 8, which transmits the reflected light that is emitted from the spectroscopic element and reflected by the object; and

and a detector that receives the transmitted light transmitted through the second beam splitter.

12. The position determining apparatus according to claim 11,

the vibration frequency of the piezoelectric member of the second beam splitter is higher than the vibration frequency of the piezoelectric member of the first beam splitter.