Spectrometer and measuring method

Abstract

To provide a spectrometer and a measuring method in which a device can be downsized and can accelerate acquisition of dark output values.SOLUTION: A spectrometer 1 comprises: a mirror device 17 having a movable part; a diffraction grating 8 for outputting a diffraction light L2 when a measuring beam L1 is made incident to a diffraction surface 8a; and a first photodetector 10 for detecting the diffraction light L2. The incident angle of the measuring beam L1 to the diffraction surface 8a changes according to the rotation angle of the movable part. The wavelength of the diffraction light L2 detected by the first photodetector 10 changes according to the incident angle of the measuring beam L1 to the diffraction surface 8a. The spectrometer 1 includes: a first mode as an operational mode, in which the detection result of the first photodetector 10 is acquired in the state in which the mirror device 17 is driven so that the measuring beam L1 from the mirror device 17 is made incident to the diffraction surface 8a; and a second mode, in which the detection result of the first photodetector 10 is acquired in the state in which the mirror device 17 is driven so that the measuring beam L1 from the mirror device 17 proceeds to the outside of the diffraction surface 8a.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a spectroscope and a measurement method using the spectroscope.

Background Art

[0002] For example, Patent Document 1 describes a spectrophotometer including a light source, a spectroscope that extracts monochromatic light from the light of the light source and can scan the wavelength of the monochromatic light, and a detector that detects light from a sample with respect to the monochromatic light. In the spectrophotometer described in Patent Document 1, a shutter that moves forward and backward with respect to the optical path by driving a motor is provided at the subsequent stage of the diffraction grating constituting the spectroscope. When the optical path is blocked by the shutter, no light enters the detector. At this time, the detection signal by the detector becomes a dark signal, and dark signal data is collected.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For the spectroscope as described above, miniaturization is required. In addition, it is also required to speed up the acquisition of the dark output value. Therefore, an object of the present invention is to provide a spectroscope and a measurement method capable of achieving miniaturization of the apparatus and speeding up the acquisition of the dark output value.

Means for Solving the Problems

[0005] The spectrometer of the present invention includes: [1] a support part, a movable part, a connecting part that connects the movable part to the support part so that the movable part can swing around a predetermined axis, and a first reflecting surface provided on the movable part. A mirror device that reflects the measurement light by the first reflecting surface at an angle corresponding to the rotation angle of the movable part around the axis, a diffraction grating having a diffraction surface, and when the measurement light from the mirror device is incident on the diffraction surface, outputs diffracted light dispersed according to the wavelength, and a first photodetector that detects the diffracted light output from the diffraction grating. The incident angle of the measurement light on the diffraction surface changes according to the rotation angle of the movable part, and the wavelength of the diffracted light detected by the first photodetector changes according to the incident angle of the measurement light on the diffraction surface. As an operation mode, a first mode of acquiring the detection result of the first photodetector in a state where the mirror device is driven so that the measurement light from the mirror device is incident on the diffraction surface, and a second mode of acquiring the detection result of the first photodetector in a state where the mirror device is driven so that the measurement light from the mirror device travels outside the diffraction surface.

[0006] In this spectrometer, the incident angle of the measurement light on the diffraction surface is changed by a mirror device having a movable part that can swing around a predetermined axis. As a result, the size of the device can be reduced as compared with, for example, the case where a diffraction grating is rotated by a motor. Further, as an operation mode, there are included a first mode in which the mirror device is driven so that the measurement light from the mirror device is incident on the diffraction surface, and a second mode in which the mirror device is driven so that the measurement light from the mirror device travels outside the diffraction surface (does not enter the diffraction surface). The dark output value can be obtained from the detection result of the first photodetector in the second mode. By switching between a state where the measurement light is incident on the diffraction surface and a state where the measurement light travels outside the diffraction surface by driving the mirror device, the size of the device can be reduced as compared with the case of using a shutter as in Patent Document 1, for example. Further, the dark output value can be obtained at high speed as compared with the case of using a shutter driven by a motor as in Patent Document 1, for example. Therefore, according to this spectrometer, the size of the device can be reduced and the acquisition of the dark output value can be speeded up.

[0007] The spectrometer of the present invention may be the spectrometer described in [1], "In the second mode, the measurement light that has traveled along a predetermined optical axis and is incident on the first reflection surface is reflected by the first reflection surface so as to return along the optical axis." In this case, it is possible to suppress the measurement light that has traveled outside the diffraction surface in the second mode from becoming stray light by being reflected, for example, inside the spectrometer, and it is possible to suppress the generation of stray light when obtaining the dark output value.

[0008] The spectrometer of the present invention may be the one described in [3] "further comprising a fixing member to which the mirror device is fixed, the mirror device further having a driving element for generating a driving force for swinging the movable part, and the fixing member being formed of a metal material, the spectrometer according to [1] or [2]". When the mirror device has a driving element, the heat generated in the driving element may affect the detection accuracy of the first photodetector. In this regard, in the spectrometer of [3], since the fixing member is formed of a metal material, the heat generated in the mirror device can be efficiently dissipated through the fixing member, and a decrease in the detection accuracy of the first photodetector can be suppressed.

[0009] The spectrometer of the present invention may be the one described in [4] "further comprising a fixing member to which the mirror device is fixed, a monitor light source for outputting monitor light, and a second photodetector for detecting the monitor light, the mirror device further having a second reflecting surface provided on the movable part on the back side opposite to the front side where the first reflecting surface is provided, a through hole being formed in the fixing member, the mirror device being fixed to the fixing member such that the second reflecting surface faces the through hole, the monitor light output from the monitor light source being incident on the second reflecting surface through the through hole, reflected by the second reflecting surface, and detected by the second photodetector through the through hole, the spectrometer according to any one of [1] to [3]". In this case, the rotation angle of the movable part can be accurately monitored based on the detection result of the second photodetector. Further, since the through hole formed in the fixing member functions as an aperture for the monitor light, it is possible to suppress the monitor light from the monitor light source from entering the first photodetector as stray light.

[0010] The spectroscope of the present invention may be the one described in [5] "The through-hole is formed in a tapered shape so that the width becomes narrower as it approaches the mirror device", as described in [4]. In this case, the monitor light from the monitor light source is less likely to leak to the surface side of the movable part, and it is possible to suppress the monitor light from entering the first photodetector as stray light. In addition, the monitor light can be incident on the second reflection surface at an angle, and it is less likely that a deviation occurs in the detection result of the second photodetector.

[0011] The spectroscope of the present invention may be the one described in [6] "The opening width of the through-hole on the side of the mirror device is narrower than the width of the movable part of the mirror device", as described in [4] or [5]. In this case, the monitor light from the monitor light source is less likely to leak to the surface side of the movable part, and it is possible to suppress the monitor light from entering the first photodetector as stray light.

[0012] The spectroscope of the present invention may be the one described in [7] "The first photodetector includes a plurality of detection elements having mutually different sensitivity wavelength ranges", as described in any one of [1] to [6]. In this case, the measurable wavelength range can be widened.

[0013] The spectroscope of the present invention may be the one described in [8] "The plurality of detection elements are arranged along the wavelength dispersion direction of the diffracted light at the incident position on the first photodetector", as described in [7]. In this case, for example, compared with the case where the plurality of detection elements are arranged along a direction perpendicular to the wavelength dispersion direction, a larger light receiving area can be ensured, and the light utilization efficiency can be increased.

[0014] The spectroscope of the present invention may be the one described in [9] "The distance between the plurality of detection elements is 1 mm or less", as described in [8]. In this case, the difference in wavelength resolution between the plurality of detection elements can be reduced. In addition, the difference in wavelength of the diffracted light incident on the plurality of detection elements can be reduced, and the calculation based on the detection results of the plurality of detection elements can be facilitated.

[0015] The spectrometer of the present invention may be the one described in

[10] "the plurality of detection elements are arranged along a direction perpendicular to the wavelength dispersion direction of the diffracted light at the incident position to the first photodetector, as described in [7]". In this case, for example, compared with the case where the plurality of detection elements are arranged along the wavelength dispersion direction, the difference in wavelength resolution between the plurality of detection elements can be reduced. Further, the difference in wavelength of the diffracted light incident on the plurality of detection elements can be reduced, and the calculation based on the detection results of the plurality of detection elements can be facilitated.

[0016] The spectrometer of the present invention may be the one described in

[11] "further comprising an arithmetic unit that receives the detection result of the first photodetector, and the arithmetic unit subtracts the value corresponding to the detection result of the first photodetector obtained in the second mode from the value corresponding to the detection result of the first photodetector obtained in the first mode, as described in any one of [1] to

[10] ". In this case, by subtracting the dark output value obtained in the second mode from the output value obtained in the first mode, measurement considering the dark output value can be performed.

[0017] The spectrometer of the present invention may be "

[12] further comprising an arithmetic unit that receives the detection result of the first photodetector, the first photodetector including a first detection element and a second detection element, (1) the first detection element having sensitivity in a wavelength range corresponding to the n-th order (n is an integer of 1 or more) and (n + 1)-th order diffracted light, the second detection element having sensitivity in a wavelength range corresponding to the (n + 1)-th order diffracted light, and the arithmetic unit calculating the output value of the n-th order diffracted light by subtracting the value corresponding to the detection result of the second detection element from the value corresponding to the detection result of the first detection element, or (2) the first detection element having sensitivity in a wavelength range corresponding to the m-th order (m is an integer of -1 or less) and (m - 1)-th order diffracted light, the second detection element having sensitivity in a wavelength range corresponding to the (m - 1)-th order diffracted light, and the arithmetic unit calculating the output value of the m-th order diffracted light by subtracting the value corresponding to the detection result of the second detection element from the value corresponding to the detection result of the first detection element, the spectrometer according to any one of [1] to

[11] ". In this case, the output value of the n-th order or m-th order diffracted light can be calculated with high accuracy.

[0018] The spectrometer of the present invention may be "

[13] further comprising an arithmetic unit that receives the detection result of the first photodetector, the mirror device further having a drive element for generating a driving force for swinging the movable part, and the arithmetic unit correcting the detection result of the first photodetector in the second mode based on an input signal to the drive element or an output value from the drive element, the spectrometer according to any one of [1] to

[12] ". In the second mode, since the rotation angle of the movable part is larger than that in the first mode, the power consumption in the drive element is large and heat is likely to be generated. In this regard, in the spectrometer of

[13] , the detection result of the first photodetector in the second mode can be corrected so as to reduce the influence of heat generation in the drive element based on the input signal to the drive element or the output value from the drive element.

[0019] The spectrometer of the present invention may be the one described in "

[14] the spectrometer according to any one of [1] to

[13] , wherein the detection result of the first photodetector is obtained in the second mode each time the rotation angle of the movable part is changed to obtain the detection result of the first photodetector in the first mode". In this case, since the dark output value is obtained each time the rotation angle of the movable part is changed, accurate measurement can be performed even when the dark output value is likely to change, for example.

[0020] The spectrometer of the present invention may be the one described in "

[15] the spectrometer according to any one of [1] to

[13] , wherein the detection result of the first photodetector is obtained in the second mode before or after obtaining the detection result of the first photodetector a plurality of times in the first mode while changing the rotation angle of the movable part". In this case, since the dark output value is obtained once for a plurality of measurements, the measurement time can be shortened.

[0021] The measurement method of the present invention may be the one described in "

[16] a measurement method using a spectrometer, wherein the spectrometer includes a support part, a movable part, a connecting part that connects the movable part to the support part so that the movable part can swing around a predetermined axis, a first reflecting surface provided on the movable part, and a mirror device that reflects measurement light by the first reflecting surface at an angle corresponding to the rotation angle of the movable part around the axis, a diffraction grating having a diffraction surface that outputs diffracted light dispersed according to the wavelength when the measurement light from the mirror device is incident on the diffraction surface, and a first photodetector that detects the diffracted light output from the diffraction grating, the incident angle of the measurement light on the diffraction surface changes according to the rotation angle of the movable part, the wavelength of the diffracted light detected by the first photodetector changes according to the incident angle of the measurement light on the diffraction surface, and the measurement method includes a first step of obtaining the detection result of the first photodetector in a state where the mirror device is driven so that the measurement light from the mirror device is incident on the diffraction surface, and a second step of obtaining the detection result of the first photodetector in a state where the mirror device is driven so that the measurement light from the mirror device travels outside the diffraction surface".

[0022] In the spectrometer used in this measurement method, the incident angle of the measurement light on the diffraction surface is changed by a mirror device having a movable part that can swing around a predetermined axis. As a result, the size of the apparatus can be reduced as compared with, for example, the case where a diffraction grating is rotated by a motor. Further, this measurement method includes a first step of driving the mirror device so that the measurement light from the mirror device is incident on the diffraction surface, and a second step of driving the mirror device so that the measurement light from the mirror device travels outside the diffraction surface (does not enter the diffraction surface). The dark output value can be obtained from the detection result of the first photodetector in the second step. By switching between the state where the measurement light is incident on the diffraction surface and the state where it travels outside the diffraction surface by driving the mirror device, the size of the apparatus can be reduced as compared with the case of using a shutter as in Patent Document 1, for example. Further, the dark output value can be obtained at high speed as compared with the case of using a shutter driven by a motor as in Patent Document 1, for example. Therefore, according to this measurement method, the size of the apparatus can be reduced and the acquisition of the dark output value can be speeded up.

[0023] The measurement method of the present invention may be "

[17] the measurement method according to

[16] , further including a third step of subtracting the value corresponding to the detection result of the first photodetector obtained in the second step from the value corresponding to the detection result of the first photodetector obtained in the first step". In this case, by subtracting the dark output value obtained in the second step from the output value obtained in the first step, measurement taking into account the dark output value can be performed.

[0024] The measurement method of the present invention is as described in

[18] "The first photodetector includes a first detection element and a second detection element. (1) The first detection element has sensitivity in a wavelength range corresponding to the n-th order (n is an integer of 1 or more) and (n + 1)-th order diffracted light, and the second detection element has sensitivity in a wavelength range corresponding to the (n + 1)-th order diffracted light. In the measurement method, the output value of the n-th order diffracted light is calculated by subtracting the value corresponding to the detection result of the second detection element from the value corresponding to the detection result of the first detection element, or (2) the first detection element has sensitivity in a wavelength range corresponding to the m-th order (m is an integer of -1 or less) and (m - 1)-th order diffracted light, and the second detection element has sensitivity in a wavelength range corresponding to the (m - 1)-th order diffracted light. In the measurement method, the output value of the m-th order diffracted light is calculated by subtracting the value corresponding to the detection result of the second detection element from the value corresponding to the detection result of the first detection element. The measurement method according to claim 16", and in this case, the output value of the n-th order or m-th order diffracted light can be accurately calculated.

Advantages of the Invention

[0025] According to the present invention, it is possible to provide a spectroscope and a measurement method capable of reducing the size of the device and accelerating the acquisition of the dark output value.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Mode for Carrying Out the Invention

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0028] As shown in FIG. 1, the spectroscope 1 includes an optical fiber 2, a slit member 3, a collimator 4, mirrors 5 and 6, a mirror unit 7, a diffraction grating 8, a condenser mirror 9, a first photodetector 10, a substrate unit 11, a light source 12, a condenser lens 13, an ND filter 14, a cylindrical lens 15, and a second photodetector 16. Each component except the optical fiber 2 and the substrate unit 11 is fixed on, for example, a plate-shaped base member (not shown). The mirror unit 7 has a mirror device 17 and a fixing member 18 to which the mirror device 17 is fixed.

[0029] Generally, in the spectroscope 1, the measurement light L1 introduced from the optical fiber 2 is reflected by the mirror device 17 and enters the diffraction plane 8a of the diffraction grating 8. When the measurement light L1 enters the diffraction plane 8a, the diffraction grating 8 outputs the diffracted light L2 dispersed according to the wavelength. Then, the diffracted light L2 is detected by the first photodetector 10. The incident angle of the measurement light L1 to the diffraction plane 8a changes according to the rotation angle of the movable part 22 of the mirror device 17 described later, and the wavelength of the diffracted light L2 detected by the first photodetector 10 changes according to the incident angle of the measurement light L1 to the diffraction plane 8a. Therefore, by performing the measurement while controlling the rotation angle of the movable part 22, the intensity of the light of a predetermined wavelength included in the measurement light L1 can be measured. In this way, in the spectroscope 1, the light of a specific wavelength is separated and detected from the measurement light L1.

[0030] The optical fiber 2, the slit member 3, the collimator 4, the mirrors 5 and 6, the mirror unit 7, the diffraction grating 8, the condenser mirror 9, and the first photodetector 10 constitute a spectroscopic optical system for spectroscopy of the measurement light L1. The optical fiber 2, the slit member 3, the collimator 4, the mirrors 5 and 6, the mirror unit 7, the diffraction grating 8, the condenser mirror 9, and the first photodetector 10 are arranged in this order on the optical path. In the spectroscopic optical system of the present embodiment, when viewed from a direction perpendicular to the paper surface in FIG. 1, the diffraction grating 8 is arranged between the collimator 4 and the condenser mirror 9. Further, when viewed from the said direction, the measurement light L1 going from the mirror 6 to the mirror unit 7 (mirror device 17) and the diffracted light L2 output from the diffraction plane 8a of the diffraction grating 8 intersect.

[0031] The optical fiber 2 is fixed to, for example, a fiber fixing portion 2a fixed on a base member. The optical fiber 2 guides the measurement light L1 of the measurement target to the slit member 3. The slit member 3 has a slit 3a facing the output end of the optical fiber 2. The measurement light L1 output from the optical fiber 2 passes through the slit 3a and proceeds to the collimator 4. The shape of the measurement light L1 proceeding to the collimator 4 is defined according to the shape of the slit 3a. The collimator 4 collimates the measurement light L1. The mirrors 5 and 6 reflect the measurement light L1 from the collimator 4 so as to proceed to the mirror unit 7 (mirror device 17).

[0032] With reference to FIGS. 2 to 6, the mirror unit 7 will be described. The mirror unit 7 has a mirror device 17 and a fixing member 18 to which the mirror device 17 is fixed. As shown in FIG. 6, the mirror device 17 has a support portion 21, a movable portion 22, a pair of connecting portions 23, and a first reflection surface 24. The support portion 21, the movable portion 22, and the pair of connecting portions 23 are integrally formed by, for example, an SOI (Silicon on Insulator) substrate. That is, the mirror device 17 is a MEMS device manufactured by processing a semiconductor substrate using MEMS (Micro Electro Mechanical Systems) technology (such as patterning and etching). The mirror device 17 is fixed to the fixing member 18 by, for example, an adhesive (not shown) made of resin on the back side of the support portion 21 (the side facing the fixing member 18).

[0033] The support portion 21 is formed, for example, in a rectangular frame shape. The support portion 21 is provided with a pair of electrode pads 21a for applying a drive current to a coil 26 described later, and a pair of wirings 21b that extend from the electrode pads 21a through one of the connecting portions 23 to the coil 26 and are electrically connected to the coil 26 (FIGS. 3 and 6). In FIG. 6, the connection portion between the coil 26 and the wiring 21b is shown in a simplified manner, but actually, one of the wirings 21b is connected to one end of the coil 26, and the other wiring 21b is connected to the other end of the coil 26. The electrode pads 21a are electrically connected to a wiring WR made of a flexible substrate described later via a metal wire 21c (FIG. 3). The metal wire 21c is made of, for example, gold, silver, copper, aluminum, or an alloy thereof. The thickness of the support portion 21 in the Z direction is 1 mm or less, for example, about 500 μm. The width of the support portion 21 (mirror device 17) in the X direction is, for example, about 5 mm, and the width of the support portion 21 in the Y direction is, for example, about 8 mm. The width of the support portion 21 in the Y direction is larger than the width of the support portion 21 in the X direction. Thereby, while bringing the magnet 19 closer to the mirror device 17 in the X direction to increase the magnetic force acting from the magnet 19 to the coil 26 described later, the wiring WR can be drawn out from the mirror device 17 in the Y direction.

[0034] The movable portion 22 has a first portion 31 and a second portion 32. The first portion 31 is formed, for example, in a circular shape in plan view (when viewed from the Z direction). The Z direction is a direction perpendicular to the first reflection surface 24. The second portion 32 is formed, for example, in a substantially rectangular annular shape in plan view. The second portion 32 surrounds the first portion 31 in plan view. The second portion 32 is connected to the first portion 31 via a pair of connection portions 33. The pair of connection portions 33 are located, for example, at the central portions of two sides parallel to the Y direction among the rectangular inner edges of the second portion 32. In this example, each connection portion 33 is composed of a pair of portions extending along the X direction.

[0035] The second part 32 has a rectangular annular inner part 321, a rectangular annular outer part 322 surrounding the inner part 321 in a plan view, and a pair of connecting parts 323 extending along the Y direction and connecting the inner part 321 to the outer part 322 on one side and the other side in the Y direction. In this example, each connecting part 323 is composed of a pair of parts extending along the Y direction. A coil 26 (driving element) for generating a driving force for swinging the movable part 22 is disposed on the outer part 322. The coil 26 is wound a plurality of times, for example, in a spiral (volute) shape. A magnetic field generated by the magnet 19 acts on the coil 26.

[0036] The pair of connecting parts 23 connect the movable part 22 to the support part 21 so that the movable part 22 can swing around the axis A. The axis A is parallel to the Y direction. Each connecting part 23 extends along the Y direction. Each connecting part 23 functions as a torsion bar that twists and deforms when the movable part 22 swings around the axis A.

[0037] The thickness of the movable part 22 and the connecting part 23 in the Z direction is, for example, about 100 μm. The thickness of the movable part 22 is smaller than the thickness of the support part 21. Thereby, even when the opening width W1 (for example, about 2 mm) of the through hole 41a is smaller than the width W2 (for example, about 3 mm) of the movable part 22 as in this example, it is possible to suppress the movable part 22 from contacting the fixing member 18 during swinging.

[0038] The first reflecting surface 24 is provided on the first part 31 of the movable part 22. More specifically, the first reflecting surface 24 is provided on the front surface (one side in the Z direction) of the first part 31. A second reflecting surface 25 (FIG. 4) is provided on the back surface (the other side in the Z direction) of the first part 31. The first reflecting surface 24 and the second reflecting surface 25 are constituted by, for example, the surface of a layer formed in a circular, elliptical or rectangular shape by a metal material such as aluminum, an aluminum-based alloy, gold or silver. The first reflecting surface 24 and the second reflecting surface 25 are formed flat, for example, perpendicular to the Z direction.

[0039] An example of a method for driving the mirror device 17 will be described. As an example, a high-frequency drive current is applied to the coil 26. At this time, since the magnetic field generated by the magnet 19 acts on the coil 26, a Lorentz force is generated in the coil 26. As a result, the movable part 22 is swung around the axis A, for example, at the resonance frequency level (resonance drive). By driving the mirror device 17 in this way, the measurement light L1 can be reflected and scanned by the first reflecting surface 24. As another example, a drive current of a certain magnitude may be applied to the coil 26. In this case, the movable part 22 rotates around the axis A according to the magnitude of the drive current and stops at a predetermined rotation angle. Thus, the movable part 22 may be statically driven (linear drive). Note that also in the linear drive, the movable part 22 can be continuously swung in the same manner as the resonance drive by applying a drive current such as a triangular wave to the coil 26.

[0040] As shown in FIGS. 2 to 5, the fixing member 18 is formed, for example, in a substantially rectangular shape having a long side parallel to the X direction in a plan view. The fixing member 18 is formed of a metal material such as an aluminum alloy or non-magnetic stainless steel. For example, the width of the fixing member 18 in the X direction is about 40 mm, and the width of the fixing member 18 in the Y direction is about 14 mm. The aspect ratio (width in the X direction / width in the Y direction) of the fixing member 18 is greater than 1, preferably 2 or more. By reducing the size of the fixing member 18 in the Y direction, which is perpendicular to the direction in which the pair of magnets 19 face each other, the entire spectrometer 1 can be downsized (thinned) in the Y direction.

[0041] The fixing member 18 has a fixing portion 41 to which the mirror device 17 is fixed at the center. On both sides of the fixing portion 41 in the X direction, a pair of arrangement grooves 42 for arranging the magnets 19 are formed. The magnet 19 is formed, for example, in a rectangular parallelepiped shape. The pair of magnets 19 face each other in the X direction, and the mirror device 17 is arranged at the center between the pair of magnets 19. Thereby, a magnetic field can be uniformly applied to the coil 26 of the mirror device 17. The depth D of the arrangement groove 42 is equal to or more than 1 / 3 of the thickness T of the magnet 19. Thereby, the pair of magnets 19 that attract each other can be surely held by the arrangement grooves 42. Also, the arrangement (assembly) of the magnet 19 in the arrangement groove 42 can be facilitated.

[0042] For example, the depth D of the arrangement groove 42 is about 2 mm, and the thickness T of the magnet 19 is about 4 mm. In this example, the magnet 19 protrudes in the Z direction with respect to the arrangement surface of the mirror device 17 in the fixing portion 41. Thereby, the arrangement of the magnet 19 in the arrangement groove 42 can be facilitated. For example, the width of the magnet 19 in the X direction is about 7 mm, and the width of the magnet 19 in the Y direction is about 10 mm. The width of the magnet 19 in the X direction is larger than the width of the mirror device 17 in the X direction, and the width of the magnet 19 in the Y direction is larger than the width of the mirror device 17 in the Y direction. Thereby, the magnet 19 can be formed larger, and the magnetic force acting on the coil 26 can be increased. The maximum thickness Ta of the fixing member 18 is, for example, about 4 mm.

[0043] The magnet 19 is in surface contact with the surface of the fixing portion 41 in a state where the surface of the magnet 19 faces the surface of the mirror device 17 at the end portion of the arrangement groove 42 on the mirror device 17 side. Thereby, while bringing the magnet 19 closer to the mirror device 17 in the arrangement groove 42, the magnet 19 can be easily positioned with respect to the arrangement groove 42. By bringing the magnet 19 and the mirror device 17 closer to each other, the magnetic force acting on the coil 26 provided on the mirror device 17 is increased, and the mirror device 17 can be efficiently driven. For example, the interval between a pair of magnets 19 in the X direction is about 7 mm, and the interval between the magnet 19 and the mirror device 17 in the X direction is about 1 mm.

[0044] For fixing the magnet 19 and the fixing member 18, for example, an adhesive made of resin (not shown) can be used. For example, the width of the arrangement groove 42 in the X direction is about 10 mm, which is larger than the width of the magnet 19 in the X direction. Also, the width (maximum width) of the arrangement groove 42 in the Y direction is about 12 mm, which is larger than the width of the magnet 19 in the Y direction. Thereby, the arrangement of the magnet 19 in the arrangement groove 42 can be facilitated. Also, a space for allowing the adhesive to escape in the arrangement groove 42 can be secured, and the occurrence of problems caused by the adhesive adhering to the mirror device 17 can be suppressed. Also, there is a gap of about 1 mm between the arrangement groove 42 and the mirror device 17 in the X direction. Thereby, even if the adhesive protrudes from the inside of the arrangement groove 42 toward the mirror device 17 side, it can be suppressed from contacting the mirror device 17. In this example, the magnet 19 does not contact the side surface of the arrangement groove 42 in the Y direction, but the magnet 19 may be in surface contact with any side surface of the arrangement groove 42 in the Y direction.

[0045] In a plan view, recesses 42a are formed at each of the four corners of the arrangement groove 42. The recesses 42a are formed in a rounded shape. In this example, the recesses 42a are curved in an arc shape. By forming the recesses 42a, when, for example, the magnet 19 is brought into surface contact with the side surface of the fixing portion 41, the adhesive stays at the corners (recesses 42a), and it is possible to suppress the adhesive from reaching the mirror device 17. Further, for example, when the magnet 19 is pressed against and fixed to the corner of the arrangement groove 42, stress concentration on the magnet 19 can be suppressed as compared with the case where the corners of the arrangement groove 42 are formed at right angles without forming the recesses 42a, for example. Note that the recesses 42a may not be formed. When the recesses 42a are not formed, miniaturization of the fixing member 18 and the mirror unit 7 in the Y direction can be achieved.

[0046] The fixing member 18 is fixed to the base member by four screws (not shown) and two positioning pins (not shown). Specifically, base fixing portions 18a for fixing the fixing member 18 to the base member are provided at both ends of the fixing member 18 in the X direction. The thickness of the base fixing portion 18a in the Z direction is, for example, about 2 mm, and the base fixing portion 18a is formed to have the same thickness as the portion of the fixing member 18 where the arrangement groove 42 is formed. Screw holes 18b into which the above-described screws are screwed are formed at both ends of each base fixing portion 18a in the Y direction. Positioning holes 18c into which the above-described positioning pins are inserted are formed at the center of each base fixing portion 18a in the Y direction. The positioning hole 18c on one side in the X direction (the left side in FIG. 3) is formed as a circular round hole, and the positioning hole 18c on the other side in the X direction (the right side in FIG. 3) is formed as a long hole elongated along the X direction. The position in the XY direction is regulated by the positioning hole 18c (round hole) on one side in the X direction, and the rotation in the XY plane is regulated by the positioning hole 18c (long hole) on the other side in the X direction.

[0047] In this embodiment, the width of the arrangement groove 42 in the X direction (about 10 mm) is larger than the width of the magnet 19 in the X direction (about 7 mm). As a result, a gap of about 3 mm is formed between the end portion of the magnet 19 in the X direction (the end portion on the fixing hole side) and the side surface of the arrangement groove 42. Thereby, a large distance can be ensured between the fixing holes (the screw hole 18b and the positioning hole 18c) in the X direction and the magnet 19. As a result, the workability when fixing the fixing member 18 to the base member can be improved, and the fixing strength of the fixing member 18 can be ensured and the positioning accuracy can be improved. The distance between the end portion of the magnet 19 in the X direction (the end portion on the fixing hole side) and the side surface of the arrangement groove 42 may be larger than the distance between the magnet 19 and the mirror device 17 in the X direction, and may be smaller than the width of the magnet 19 and the width of the mirror device 17 in the X direction. Thereby, a space for discharging the adhesive for fixing the magnet 19 can be secured, and while ensuring the workability when fixing the fixing member 18 to the base member, the size reduction of the mirror unit 7 in the X direction can be achieved.

[0048] The fixing portion 41 is formed with a through hole 41a penetrating the fixing portion 41 along the Z direction. The monitor light L3 described later is incident on the through hole 41a. The through hole 41a is formed in a tapered shape so that the width becomes narrower as it approaches the mirror device 17. In this example, the through hole 41a is formed in a tapered shape in any cross section parallel to the Z direction. The through hole 41a has a circular opening edge on both the mirror device 17 side and the side opposite to the mirror device 17 (FIG. 5). The mirror device 17 is fixed to the fixing portion 41 so that the second reflection surface 25 (the back surface) faces the through hole 41a. In other words, the mirror device 17 is fixed to the fixing portion 41 so that the first reflection surface 24 (the front surface) faces the side opposite to the fixing member 18. The opening width W1 of the through hole 41a on the mirror device 17 side is narrower than the width W2 of the movable portion 22. That is, when viewed from the mirror device 17 side, the through hole 41a is covered by the movable portion 22. The opening width W1 may be narrower than the width of the second reflection surface 25 (the first reflection surface 24).

[0049] For example, the aperture width W1 is about 2 mm, and the width W2 of the movable part is about 3 mm. The aperture width of the through-hole 41a on the light source 12 side (the side opposite to the mirror device 17) is, for example, about 9 mm. The aperture width of the through-hole 41a on the light source 12 side may be larger than the width of the mirror device 17 in the X direction and the width of the magnet 19 in the X direction. Also, in the cross-section of FIG. 4, the opening edge of the through-hole 41a on the light source 12 side may be located outside (the side opposite to the mirror device 17) the end of the magnet 19 on the mirror device 17 side. Thereby, the monitor light L3 emitted from the light source 12 can be surely guided to the second reflection surface 25.

[0050] A wiring WR made of, for example, a flexible printed circuit (FPC) is connected to the mirror device 17. The wiring WR is drawn out from the mirror device 17 along the Y direction perpendicular to the X direction in which the pair of magnets 19 face each other. Thereby, the wiring WR can be preferably drawn out as compared with, for example, the case where the wiring WR is drawn out from the mirror device 17 along the direction in which the pair of magnets 19 face each other. Also, in this example, the fixing member 18 has a shape elongated in the X direction in which the pair of magnets 19 face each other (a shape in which the length in the X direction is longer than the length in the Y direction). Thereby, the size of the mirror unit 7 in the Y direction perpendicular to the X direction in which the pair of magnets 19 face each other can be reduced, and the size of the spectroscope 1 can be reduced. The wiring WR is electrically connected to, for example, an electrode pad 21a formed on the support portion 21 of the mirror device 17 via a metal wire 21c (FIGS. 3 and 6).

[0051] Referring again to FIG. 1, the diffraction grating 8 has a diffraction surface 8a. The measurement light L1 reflected by the first reflection surface 24 of the mirror device 17 is incident on the diffraction surface 8a. In this example, the diffraction grating 8 is configured as a reflection type, reflects the measurement light L1 at the diffraction surface 8a, and outputs diffracted light L2 dispersed according to the wavelength. A large number of grooves 8b arranged along a predetermined direction are formed on the diffraction surface 8a. These grooves 8b constitute a blazed grating. In FIG. 1, the grooves 8b are depicted large for the purpose of explanation, but the actual grooves 8b are so small that they are not visible to the naked eye. For example, the period of the grooves is about several μm. When the measurement light L1 is incident on the diffraction surface 8a, diffracted light L2 dispersed for each wavelength along the predetermined direction (the arrangement direction of the grooves 8b) is output. In this example, the diffraction surface 8a is formed in the central portion of the surface of the diffraction grating 8 facing the mirror device 17 side. On the outer portion of the surface of the diffraction grating 8 facing the mirror device 17 side, there is a non-diffraction region 8c where the diffraction surface 8a is not formed. When the measurement light L1 is incident on the non-diffraction region 8c, the diffraction grating 8 does not output diffracted light L2. Note that the diffraction grating 8 may be configured as a transmission type. In this case, the measurement light L1 is diffracted at the diffraction surface 8a when passing through the diffraction grating 8. The non-diffraction region 8c may not be formed in the diffraction grating 8, and the diffraction surface 8a may be formed over the entire surface of the diffraction grating 8 facing the mirror device 17 side.

[0052] The condensing mirror 9 condenses the diffracted light L2 output from the diffraction grating 8 onto the first photodetector 10. The first photodetector 10 detects the diffracted light L2 condensed by the condensing mirror 9. In the spectrometer 1, the incident angle of the measurement light L1 on the diffraction surface 8a changes according to the rotation angle of the movable part 22 of the mirror device 17, and the wavelength of the diffracted light L2 detected by the first photodetector 10 changes according to the incident angle of the measurement light L1 on the diffraction surface 8a. Note that in this embodiment, the diffracted light L2 is condensed by a condensing mirror 9 separate from the diffraction grating 8, but for example, the condensing mirror 9 may be omitted by forming the diffraction surface 8a of the diffraction grating 8 as a concave surface. In this case, further miniaturization of the optical system can be achieved.

[0053] As shown in Fig. 7(a), the first photodetector 10 has a first detection element 51, a second detection element 52, and a third detection element 53. The first detection element 51, the second detection element 52, and the third detection element 53 have sensitivity wavelengths in the near-infrared and / or mid-infrared regions and have different sensitivity wavelength ranges from each other. For example, the first detection element 51 has sensitivity wavelengths in the near-infrared and mid-infrared regions, and the second detection element 52 and the third detection element 53 have sensitivity wavelengths in the near-infrared region. As an example, as shown in Fig. 8(b), the first detection element 51 is a detection element using InAsSb for the semiconductor layer and has sensitivity in a wavelength range (wavelength region) up to about 5 μm at maximum. The second detection element 52 is a detection element using InGaAs for the semiconductor layer and has sensitivity in a wavelength range up to about 2.6 μm at maximum. The third detection element 53 is a detection element using InGaAs for the semiconductor layer and has sensitivity in a wavelength range up to about 1.7 μm at maximum. Note that the detection elements 51 to 53 may have sensitivity wavelengths in the visible light region.

[0054] As shown in Figs. 8(a) and 8(b), the sensitivity wavelength range of the first detection element 51 corresponds to the first-order, second-order, and third-order diffracted lights L2. Hereinafter, the first-order diffracted light L2 will also be referred to as the first-order light, the second-order diffracted light L2 as the second-order light, and the third-order diffracted light L2 as the third-order light. As shown in Fig. 8(a), when the mirror angle (rotation angle of the movable part 22) is the same, the wavelength of the second-order light detected is 1 / 2 of the first-order light, and the wavelength of the third-order light is 1 / 2 of the second-order light. That is, among the diffracted lights L2 incident on the first photodetector 10 when the mirror angle is the same, in addition to the first-order light which is the measurement wavelength, there are higher-order lights such as the second-order light having a wavelength of 1 / 2 of the first-order light and the third-order light having a wavelength of 1 / 2 of the second-order light. The sensitivity wavelength range of the first detection element 51 includes the wavelength ranges of the first-order light, the second-order light, and the third-order light. The sensitivity wavelength range of the second detection element 52 corresponds to the second-order light and the third-order light and includes the wavelength ranges of the second-order light and the third-order light. The sensitivity wavelength range of the third detection element 53 corresponds to the third-order light and includes the wavelength range of the third-order light.

[0055] In the optical splitter 1, output values of the primary light, secondary light, and tertiary light are calculated by the following operations. The following operations are executed by an operation unit 64 described later. Specifically, the operation unit 64 first calculates an output value (tertiary light component) of the tertiary light from the detection result (detection intensity) of the third detection element 53. Next, the operation unit 64 calculates an output value (secondary light component) of the secondary light by subtracting the output value of the tertiary light (a value corresponding to the detection result of the third detection element 53) from the detection result (detection intensity) of the second detection element 52. Subsequently, the operation unit 64 calculates an output value (primary light component) of the primary light by subtracting the output value of the secondary light (a value corresponding to the detection result of the second detection element 52) and the output value of the tertiary light (a value corresponding to the detection result of the third detection element 53) from the detection result (detection intensity) of the first detection element 51. By using the primary light, secondary light, and tertiary light in this way, the measurable wavelength range can be widened. In actual operations, values obtained by multiplying the detection results (detection intensities) of the respective detection elements by the sensitivity at the wavelength (values corresponding to the detection results) are used. That is, the operations are performed in consideration of the sensitivity ratios of the respective detection elements at the wavelength.

[0056] FIG. 9 is a graph showing an example of measurement results. In this example, the results when the measurement light L1 passes through the polystyrene film and when it does not pass through are compared. The measurement light L1 is light from a tungsten lamp, and a wavelength range of 1.45 μm or less is cut by a high-pass filter. The upper two graphs G1 and G2 in FIG. 9 show the results (reference data) when the measurement light L1 does not pass through the polystyrene film. The lower two graphs G3 and G4 in FIG. 9 show the results (sample data) when the measurement light L1 passes through the polystyrene film. Graphs G1 and G3 show the acquired data, and graphs G2 and G4 show the spectral data calculated based on the data. From the comparison of graphs G2 and G4, it can be seen that when the measurement light L1 passes through the polystyrene film, the intensity decreases in the wavelength range of approximately 3300 to 3500 nm, and it can be understood that the measurement light L1 is absorbed by the polystyrene film in this wavelength range.

[0057] FIG. 10 is a graph showing the measurement results of FIG. 9 together with the measurement results by FTIR (Fourier Transform Infrared Spectroscopy). From FIG. 10, it can be seen that according to the spectrometer 1, spectroscopic measurement can be accurately performed in a wavelength range as wide as that of FTIR.

[0058] Referring again to FIG. 7, the arrangement of the first detection element 51, the second detection element 52, and the third detection element 53 in the first photodetector 10 will be described. In FIG. 7, the outer edge of the base portion of the CAN package 55 (FIG. 1) on which the detection elements 51 to 53 are mounted is indicated by the reference symbol B. In the example of FIG. 7(a), the first detection element 51, the second detection element 52, and the third detection element 53 are arranged along the wavelength dispersion direction DR of the diffracted light L2 at the incident position on the first photodetector 10. In the example of FIG. 7(b), the first detection element 51, the second detection element 52, and the third detection element 53 are arranged along a direction perpendicular to the wavelength dispersion direction DR. The wavelength dispersion direction DR is the direction in which the diffracted light L2 is dispersed, and the diffracted light L2 dispersed along the wavelength dispersion direction DR is incident on the first photodetector 10. As shown in FIG. 7, the diffracted light L2 is observed like a band-shaped rainbow on the first photodetector 10. In response to the rotation of the movable part 22 of the mirror device 17, this band-shaped rainbow moves along the wavelength dispersion direction DR. As a result, the wavelength of the diffracted light L2 incident on each detection element 51 to 53 changes.

[0059] In the example of Fig. 7(a), the light-receiving areas (lengths in the direction perpendicular to the wavelength dispersion direction DR) of the detection elements 51 to 53 can be ensured to be large, and the light utilization efficiency can be increased. On the other hand, since the incident wavelength varies according to the positions of the detection elements 51 to 53, correction by calculation is required during measurement. Also, the wavelength resolution varies according to the positions of the detection elements 51 to 53. That is, in the detector, since the optical design is such that the focus is at the center of the base portion of the CAN package 55, defocusing occurs as the distance from the center increases, and the wavelength resolution may decrease. In this regard, in the example of Fig. 7(a), the distance between the detection elements 51 to 53 in the wavelength dispersion direction DR is set to 1 mm or less. Thereby, the difference in the wavelengths of the diffracted light L2 incident on the detection elements 51 to 53 can be reduced, and the calculation based on the detection results of the detection elements 51 to 53 can be facilitated. Also, the difference in wavelength resolution between the detection elements 51 to 53 can be reduced.

[0060] In the example of Fig. 7(b), since the detection elements 51 to 53 are arranged along the direction perpendicular to the wavelength dispersion direction DR, the difference (elimination) in the wavelengths of the diffracted light L2 incident on the detection elements 51 to 53 can be reduced, and the calculation based on the detection results of the detection elements 51 to 53 can be facilitated. Also, the difference (elimination) in wavelength resolution between the detection elements 51 to 53 can be reduced. Note that the width of the diffracted light L2 incident on the first photodetector 10 (width in the direction perpendicular to the wavelength dispersion direction DR) is determined according to the shape of the slit 3a of the slit member 3. If the slit 3a is enlarged, the width of the diffracted light L2 on the first photodetector 10 can be widened, but the sizes of the first reflecting surface 24 of the mirror device 17, the condenser mirror 9, and the detection elements 51 to 53, etc. also need to be enlarged. Therefore, it is necessary to appropriately set the size of the slit 3a in consideration of the required S / N ratio.

[0061] Referring back to FIG. 1, the substrate unit 11 has a wiring board 61 and a plurality of electronic components 62 mounted on the wiring board 61. The first photodetector 10 is mounted on the wiring board 61. The plurality of electronic components 62 includes, for example, a control unit 63 that controls the operation of each element of the spectroscope 1 including the mirror device 17, and an arithmetic unit 64 that performs a predetermined calculation based on the detection results of the first photodetector 10 and the second photodetector 16. The control unit 63 and the arithmetic unit 64 are constituted by a computer including a processor such as a CPU and storage media such as a RAM and a ROM. The control unit 63 and the arithmetic unit 64 may be configured as separate elements from each other, or may be configured as common elements to each other. At least one of the control unit 63 and the arithmetic unit 64 may be provided separately from the substrate unit 11. For example, at least one of the control unit 63 and the arithmetic unit 64 may be constituted by a computer disposed outside the spectroscope 1 and communicably connected to the spectroscope 1. The control unit 63 and the arithmetic unit 64 are interchangeable, and the process described as being executed by the control unit 63 may be executed by the arithmetic unit 64, or the process described as being executed by the arithmetic unit 64 may be executed by the control unit 63.

[0062] The light source 12, the condenser lens 13, the ND filter 14, the cylindrical lens 15, the mirror unit 7, and the second photodetector 16 constitute a monitor optical system for monitoring the rotation angle (swing angle) of the movable part 22 of the mirror device 17. The condenser lens 13, the ND filter 14, the cylindrical lens 15, the mirror unit 7, and the second photodetector 16 are arranged in this order on the optical path of the monitor light L3 output from the light source 12.

[0063] The light source 12 is a monitor light source that outputs the monitor light L3. The light source 12 is constituted by, for example, an LD (Laser Diode) or an LED (Light Emitting Diode). The center wavelength of the monitor light L3 output from the light source 12 does not overlap with the sensitivity wavelength range of the detection elements 51 to 53 of the first photodetector 10. Thereby, it is possible to suppress the monitor light from being detected by the first photodetector 10 as stray light. The monitor light L3 is, for example, light in the visible range.

[0064] The light collecting lens 13 collects the monitor light L3. The ND filter 14 reduces the amount of light of the monitor light L3. In this example, the ND filter 14 is disposed obliquely with respect to the optical axis of the monitor light L3. Thereby, it is possible to suppress the generation of stray light due to reflection on the surface of the ND filter 14. The cylindrical lens 15 diffuses the monitor light L3 in a line shape. The monitor light L3 from the cylindrical lens 15 is reflected by the second reflecting surface 25 of the movable portion 22 of the mirror device 17. Specifically, the monitor light L3 enters the through hole 41a (FIG. 4) of the fixed member 18 described above, enters the second reflecting surface 25 through the through hole 41a. The monitor light L3 reflected by the second reflecting surface 25 travels through the through hole 41a, exits from the through hole 41a, and is detected by the second photodetector 16.

[0065] The second photodetector 16 is an image sensor (line sensor) formed of, for example, silicon. The arithmetic unit 64 monitors (measures) the rotation angle of the movable part 22 based on the detection result of the second photodetector 16. In this example, the monitor light L3 diffused in a line shape is made incident on the second reflecting surface 25, and the second photodetector 16 which is an image sensor detects the monitor light L3, so that the rotation angle of the movable part 22 can be measured in real time (the rotation angle can be measured at any angle). More specifically, for example, by previously storing angle information corresponding to each pixel number of the image sensor, the rotation angle of the movable part 22 can be grasped from the pixel number on which the monitor light L3 is incident. When the monitor light L3 is incident on a plurality of pixels and outputs from the plurality of pixels are acquired, the angle corresponding to the pixel with the maximum output may be determined as the rotation angle, or the average value of the outputs may be calculated to determine the rotation angle. When performing fixed-point measurement for measuring the rotation angle only at one or a plurality of specific angles, the second photodetector 16 may be configured by providing one or a plurality of detection elements having a single channel. However, from the viewpoint of monitoring the rotation angle with high accuracy and simplifying the calculation of the rotation angle, it is preferable to use an image sensor. In the above example, the arithmetic unit 64 monitors the rotation angle of the movable part 22 based on the detection result of the second photodetector 16. However, the correspondence relationship between the pixel information (such as pixel number) of the image sensor constituting the second photodetector 16 and the wavelength measured by the first photodetector 10 may be stored in advance, and the measured wavelength may be monitored in real time based on the pixel information (without passing through the rotation angle information). Thereby, wavelength information can be acquired more easily.

[0066] The operation of the optical splitter 1 (measurement method using the optical splitter 1) will be described. The optical splitter 1 includes a first mode (first step) and a second mode (second step) as operation modes. The processing of the first mode and the second mode is executed by the control unit 63 or the arithmetic unit 64. In the first mode, the detection result of the first photodetector 10 is acquired in a state where the mirror device 17 is driven so that the measurement light L1 from the mirror device 17 is incident on the diffraction surface 8a of the diffraction grating 8. In the second mode, the detection result of the first photodetector 10 is acquired in a state where the mirror device 17 is driven so that the measurement light L1 from the mirror device 17 travels outside the diffraction surface 8a (does not enter the diffraction surface 8a). The first mode is a mode corresponding to normal spectroscopic measurement, and the second mode is a mode for acquiring a dark output value in a dark state where the light to be detected is not incident on the first photodetector 10. The arithmetic unit 64 calculates the measurement result (third step) by subtracting the detection result of the first photodetector 10 acquired in the second mode from the detection result of the first photodetector 10 acquired in the first mode. For this calculation, a value corresponding to the detection result of the first photodetector 10 (for example, a value considering the sensitivity at each wavelength) may be used instead of the detection result of the first photodetector 10 itself. The monitoring of the rotation angle of the movable part 22 using the monitor optical system is performed in both the first mode and the second mode.

[0067] In the first mode, as shown in FIG. 1, the measurement light L1 from the mirror device 17 is incident on the diffraction surface 8a of the diffraction grating 8. In other words, the control unit 63 controls the mirror device 17 so that the measurement light L1 is incident on the diffraction surface 8a. In the second mode, as shown in FIG. 11, the measurement light L1 from the mirror device 17 travels outside the diffraction surface 8a. In other words, the control unit 63 controls the mirror device 17 so that the measurement light L1 is not incident on the diffraction surface 8a. In the second mode, the rotation angle of the movable part 22 is larger than that in the first mode. In this example, as shown in FIG. 11, the measurement light L1 that travels along the predetermined optical axis P and is incident on the first reflection surface 24 is reflected by the first reflection surface 24 so as to return along the optical axis. The measurement light L1 reflected by the first reflection surface 24 returns on the optical path in the spectroscopic optical system and is incident on the slit 3a of the slit member 3. Thereby, it is possible to suppress the measurement light L1 from being reflected, for example, inside the spectroscope 1 and becoming stray light.

[0068] In the second mode, for example, the movable part 22 may be driven stepwise (that is, the movable part 22 may be stopped for each rotation angle corresponding to the wavelength of the measurement target), and the dark output value may be acquired at each rotation angle. Alternatively, for example, the movable part 22 may be continuously rotated by applying a drive current such as a triangular wave to the coil 26 of the mirror device 17, and the average output value within a predetermined time width may be acquired as the dark output value. In the former case, the dark output value at each rotation angle can be acquired with a high S / N ratio and wavelength resolution. In the latter case, the dark output values corresponding to a plurality of wavelengths can be acquired at high speed.

[0069] The order of implementing the first mode and the second mode is not limited, and the second mode may be implemented after the first mode, or vice versa. Further, when measurements for a plurality of wavelengths are continuously performed, each time the rotation angle of the movable part 22 is changed and the detection result of the first photodetector 10 in the first mode is acquired, the detection result of the first photodetector 10 in the second mode may be acquired. That is, each time the measurement in the first mode is performed once, the acquisition of the dark output value in the second mode may be performed. Alternatively, before or after the detection result of the first photodetector 10 in the first mode is acquired a plurality of times while changing the rotation angle of the movable part 22, the detection result of the first photodetector 10 in the second mode may be acquired. That is, for a plurality of measurements in the first mode, the acquisition of the dark output value in the second mode may be performed once.

[0070] In the second mode, the arithmetic unit 64 may correct the detection result of the first photodetector 10 in the second mode so as to reduce the influence of heat generation in the coil 26 based on the input signal to the coil 26 or the output value from the coil 26. When the mirror device 17 is driven, heat is generated by energizing the coil 26. This heat can affect the detection accuracy of the first photodetector 10. The influence of heat on the detection accuracy of the first photodetector 10 tends to be significant when the first photodetector 10 has sensitivity in the mid-infrared region. Further, in the second mode, since the rotation angle of the movable part 22 is larger than that in the first mode, the power consumption in the coil 26 increases and heat is likely to be generated. In this regard, by correcting the detection result of the first photodetector 10 in the second mode based on the input signal to the coil 26 or the output value from the coil 26, the influence of heat generation in the coil 26 can be reduced. The input signal to the coil 26 is, for example, the current or voltage applied to the coil 26. The output value from the coil 26 is, for example, the resistance value, voltage value, or current value in the coil 26. These values correspond to the amount of heat generated in the coil 26. Note that instead of or in addition to the correction in the second mode, in the first mode, the arithmetic unit 64 may correct the detection result of the first photodetector 10 in the first mode so as to reduce the influence of heat generation in the coil 26 based on the input signal to the coil 26 or the output value from the coil 26. [Function and Effect]

[0071] In the spectroscope 1, the incident angle of the measurement light L1 on the diffraction surface 8a is changed by the mirror device 17 having the movable part 22 swingable around the axis A. Thereby, for example, compared with the case where the diffraction grating 8 is rotated by a motor, the size of the apparatus can be reduced. Further, as an operation mode, there are a first mode in which the mirror device 17 is driven so that the measurement light L1 from the mirror device 17 is incident on the diffraction surface 8a, and a second mode in which the measurement light L1 from the mirror device 17 travels outside the diffraction surface 8a (does not enter the diffraction surface 8a). The dark output value can be obtained from the detection result of the first photodetector 10 in the second mode. For example, depending on the type of the photodetector constituting the first photodetector 10, there are some in which the dark output is likely to fluctuate due to electrical or thermal factors. In order to realize accurate spectroscopic measurement, it is extremely important to obtain the dark output. By switching between the state where the measurement light L1 is incident on the diffraction surface 8a and the state where the measurement light L1 travels outside the diffraction surface 8a by driving the mirror device 17, for example, compared with the case of using a shutter as in Patent Document 1, the size of the apparatus can be reduced. Further, for example, compared with the case where a shutter driven by a motor as in Patent Document 1 is used to obtain the dark output value, the dark output value can be obtained at high speed. Further, for example, compared with the case where the dark output value is obtained by rotating the diffraction grating 8 by a motor, the dark output value can be obtained at high speed. Therefore, according to the spectroscope 1, the size of the apparatus can be reduced and the acquisition of the dark output value can be speeded up.

[0072] In the second mode, the measurement light L1 that has traveled along the optical axis P and is incident on the first reflection surface 24 is reflected by the first reflection surface 24 so as to return along the optical axis P (FIG. 11). Thereby, it is possible to suppress the measurement light L1 that has traveled outside the diffraction surface 8a in the second mode from becoming stray light by being reflected, for example, inside the spectroscope 1, and it is possible to suppress the generation of stray light when obtaining the dark output value.

[0073] The mirror device 17 is fixed to the fixing member 18. The mirror device 17 has a coil 26 for generating a driving force to swing the movable part 22, and the fixing member 18 is formed of a metal material. When the mirror device 17 has the coil 26, the heat generated in the coil 26 can affect the detection accuracy of the first photodetector 10. In this regard, in the spectroscope 1, since the fixing member 18 is formed of a metal material, the heat generated in the mirror device 17 can be efficiently dissipated to the outside of the spectroscope through the fixing member 18 and the base member to which the fixing member 18 is fixed, and a decrease in the detection accuracy of the first photodetector 10 can be suppressed.

[0074] The spectroscope 1 includes a light source 12 (monitor light source) that outputs the monitor light L3 and a second photodetector 16 that detects the monitor light L3. The mirror device 17 has a second reflection surface 25 provided on the movable part 22 on the back side opposite to the front side where the first reflection surface 24 is provided. A through hole 41a is formed in the fixing member 18, and the mirror device 17 is fixed to the fixing member 18 such that the second reflection surface 25 faces the through hole 41a. Then, the monitor light L3 output from the light source 12 enters the second reflection surface 25 through the through hole 41a, is reflected by the second reflection surface 25, and is detected by the second photodetector 16 through the through hole 41a. Thereby, the rotation angle of the movable part 22 can be accurately monitored based on the detection result of the second photodetector 16. Further, since the through hole 41a formed in the fixing member 18 functions as an aperture for the monitor light L3, it is possible to suppress the monitor light L3 from the light source 12 from entering the first photodetector 10 as stray light.

[0075] The through-hole 41a is formed in a tapered shape such that its width becomes narrower as it approaches the mirror device 17. As a result, the monitor light L3 from the light source 12 is less likely to leak to the surface side of the movable part 22, and it is possible to suppress the monitor light L3 from entering the first photodetector 10 as stray light. Also, the monitor light L3 can be incident on the second reflecting surface 25 at an angle, and it becomes less likely that there is a deviation in the detection result of the second photodetector 16. That is, it is possible to suppress the monitor light L3 that enters the second reflecting surface 25 through the through-hole 41a and the monitor light L3 that is reflected by the second reflecting surface 25 and heads toward the second photodetector 16 through the through-hole 41a from being blocked by the fixing member 18.

[0076] The opening width W1 of the through-hole 41a on the side of the mirror device 17 is narrower than the width W2 of the movable part 22 of the mirror device 17. As a result, the monitor light L3 from the light source 12 is less likely to leak to the surface side of the movable part 22, and it is possible to suppress the monitor light L3 from entering the first photodetector 10 as stray light.

[0077] The first photodetector 10 includes a first detection element 51, a second detection element 52, and a third detection element 53 having mutually different sensitivity wavelength ranges. Thereby, the measurable wavelength range can be widened.

[0078] In the example of FIG. 7(a), the detection elements 51 to 53 are arranged along the wavelength dispersion direction DR of the diffracted light L2 at the incident position on the first photodetector 10. In this case, for example, compared with the case where the detection elements 51 to 53 are arranged along a direction perpendicular to the wavelength dispersion direction DR, a larger light-receiving area can be ensured, and the light utilization efficiency can be increased.

[0079] In the example of FIG. 7(a), the distance between the detection elements 51 to 53 may be 1 mm or less. In this case, the difference in wavelength resolution between the detection elements 51 to 53 can be reduced. Also, the difference in the wavelength of the diffracted light L2 incident on the detection elements 51 to 53 can be reduced, and the calculation based on the detection results of the detection elements 51 to 53 can be facilitated. In the example of FIG. 7(b), the distance between the detection elements 51 to 53 may be 1 mm or less. In this case, the dead space between the detection elements 51 and 52 and between the detection elements 52 and 53 can be reduced, and the light utilization efficiency can be increased.

[0080] In the example of FIG. 7(b), the detection elements 51 to 53 are arranged along a direction perpendicular to the wavelength dispersion direction DR of the diffracted light L2 at the incident position to the first photodetector 10. In this case, for example, compared with the case where the detection elements 51 to 53 are arranged along the wavelength dispersion direction DR, the difference in wavelength resolution between the detection elements 51 to 53 can be reduced. Also, the difference in the wavelength of the diffracted light L2 incident on the detection elements 51 to 53 can be reduced, and the calculation based on the detection results of the detection elements 51 to 53 can be facilitated.

[0081] The arithmetic unit 64 subtracts the value corresponding to the detection result of the first photodetector 10 obtained in the second mode from the value corresponding to the detection result of the first photodetector 10 obtained in the first mode. Thereby, by subtracting the dark output value obtained in the second mode from the output value obtained in the first mode, measurement considering the dark output value can be performed.

[0082] The first photodetector 10 includes a first detection element 51 having sensitivity in a wavelength range corresponding to the first-order, second-order, and third-order diffracted light L2, a second detection element having sensitivity in a wavelength range corresponding to the second-order and third-order diffracted light L2, and a third detection element having sensitivity in a wavelength range corresponding to the third-order diffracted light L2. Then, the arithmetic unit 64 calculates the output value of the first-order diffracted light L2 by subtracting the value corresponding to the detection result of the second detection element 52 and the value corresponding to the detection result of the third detection element 53 from the value corresponding to the detection result of the first detection element 51. Thereby, the output value of the first-order diffracted light L2 can be accurately calculated. Further, the arithmetic unit 64 calculates the output value of the second-order diffracted light L2 by subtracting the value corresponding to the detection result of the third detection element 53 from the value corresponding to the detection result of the second detection element 52. Thereby, the output value of the second-order diffracted light L2 can be accurately calculated.

[0083] The arithmetic unit 64 corrects the detection result of the first photodetector 10 in the second mode based on the input signal to the coil 26 or the output value from the coil 26. In the second mode, since the rotation angle of the movable part 22 is larger than that in the first mode, the power consumption in the coil 26 increases and heat is likely to be generated. In this regard, in the spectroscope 1, based on the input signal to the coil 26 or the output value from the coil 26, the detection result of the first photodetector 10 in the second mode can be corrected so as to reduce the influence of heat generation in the coil 26.

[0084] Each time the rotation angle of the movable part 22 is changed to obtain the detection result of the first photodetector 10 in the first mode, the detection result of the first photodetector 10 in the second mode may be obtained. In this case, since the dark output value is obtained each time the rotation angle of the movable part 22 is changed, accurate measurement can be performed even when, for example, the dark output value is likely to change.

[0085] Alternatively, before or after acquiring the detection results of the first photodetector 10 a plurality of times in the first mode while changing the rotation angle of the movable part 22, the detection results of the first photodetector 10 may be acquired in the second mode. In this case, since the dark output value is acquired once for a plurality of measurements, the measurement time can be shortened.

[0086] The present invention is not limited to the above-described embodiments. For example, the materials and shapes of the respective components are not limited to the materials and shapes described above, and various materials and shapes can be adopted.

[0087] In the second mode of the above-described embodiment, the measurement light L1 is reflected by the first reflecting surface 24 so as to return along the optical axis P. However, it is only necessary that the measurement light L1 from the mirror device 17 travels outside the diffraction surface 8a, and the traveling method of the measurement light L1 is not limited. For example, the measurement light L1 from the mirror device 17 may enter the non-diffraction region 8c of the diffraction grating 8. However, in this case, since the measurement light L1 reflected in the non-diffraction region 8c may enter the first photodetector 10 as stray light, it is preferable that the measurement light L1 travels outside the diffraction grating 8.

[0088] The drive element for generating the driving force for swinging the movable part 22 was the coil 26 in the above-described embodiment, but it is not limited thereto, and for example, a piezoelectric element may be used. In this case, the piezoelectric element may be provided, for example, at the connecting part 23. In the above-described embodiment, the through hole 41a formed in the fixed member 18 was formed in a tapered shape, but the width of the through hole 41a may be uniform along the Z direction. In the above-described embodiment, the through hole 41a was formed in a tapered shape in any cross section parallel to the Z direction, but it suffices that the through hole 41a is formed in a tapered shape in a cross section passing through the center of the through hole 41a and parallel to the X direction (the direction parallel to the axis A), and it does not have to be formed in a tapered shape in a cross section passing through the center of the through hole 41a and parallel to the Y direction. The opening width W1 of the through hole 41a may be equal to or greater than the width W2 of the movable part 22. In the above-described embodiment, two magnets 19 were arranged, but four magnets 19 may be arranged. In this case, the additional two magnets 19 may be arranged so as to sandwich the mirror device 17 in the Y direction. The distance between the detection elements 51 to 53 in the wavelength dispersion direction DR may be greater than 1 mm.

[0089] In the above-described embodiment, the output value of the first-order diffracted light L2 was calculated by subtracting the value corresponding to the detection result of the second detection element 52 and the value corresponding to the detection result of the third detection element 53 from the value corresponding to the detection result of the first detection element 51. However, the output value of the first-order diffracted light L2 may be calculated by subtracting only the value corresponding to the detection result of the second detection element 52 from the value corresponding to the detection result of the first detection element 51. The first photodetector 10 does not have to have the third detection element 53. That is, in the above-described embodiment, the first-order light, the second-order light, and the third-order light were used, but only the first-order light and the second-order light may be used. Alternatively, the second detection element 52 and the third detection element 53 may be omitted, and only the first-order light may be used. The process of correcting the detection result of the first photodetector 10 in the second mode based on the input signal to the coil 26 or the output value from the coil 26 does not have to be performed.

[0090] The primary light, secondary light, and tertiary light in the above-described embodiment may be replaced with -primary light, -secondary light, and -tertiary light. That is, in the above-described embodiment, the first detection element 51 has sensitivity to primary light, secondary light, and tertiary light, the second detection element 52 has sensitivity to secondary light and tertiary light, the third detection element 53 has sensitivity to tertiary light, and the arithmetic unit 64 calculates the output value of the secondary light by subtracting the detection result of the third detection element 53 from the detection result of the second detection element 52, and calculates the output value of the primary light by subtracting the detection results of the second detection element 52 and the third detection element 53 from the detection result of the first detection element 51. However, the first detection element 51 may have sensitivity to -primary light, -secondary light, and -tertiary light, the second detection element 52 may have sensitivity to -secondary light and -tertiary light, the third detection element 53 may have sensitivity to -tertiary light, and the arithmetic unit 64 may calculate the output value of the -secondary light by subtracting the detection result of the third detection element 53 from the detection result of the second detection element 52, and calculate the output value of the -primary light by subtracting the detection results of the second detection element 52 and the third detection element 53 from the detection result of the first detection element 51. The first detection element 51 may have sensitivity to the wavelength ranges corresponding to the n-th order (n is an integer of 1 or more) and (n + 1)-th order diffracted light L2, and the second detection element 52 may have sensitivity to the wavelength range corresponding to the (n + 1)-th order diffracted light. In the above-described embodiment, n is 1. n may be 2 or more. For example, when n is 2, secondary light and tertiary light are used. The first detection element 51 may have sensitivity to the wavelength ranges corresponding to the m-th order (m is an integer of -1 or less) and (m - 1)-th order diffracted light L2, and the second detection element 52 may have sensitivity to the wavelength range corresponding to the (m - 1)-th order diffracted light. In the above modification, m is -1. m may be -2 or less. For example, when m is -2, -secondary light and -tertiary light are used.

[0091] The first photodetector 10 may have only one detection element. In this case, the spectroscope 1 is configured as a monochromator-type spectroscope that separates and detects only light of a specific wavelength from the measurement light L1. Even when the plurality of detection elements 51 to 53 included in the first photodetector 10 are arranged along a direction perpendicular to the wavelength dispersion direction DR as shown in FIG. 7(b), the spectroscope 1 is a monochromator-type spectroscope. On the other hand, when the plurality of detection elements 51 to 53 included in the first photodetector 10 are arranged along the wavelength dispersion direction DR as shown in FIG. 7(a), the incident wavelengths to the detection elements 51 to 53 are slightly different depending on the positions of the detection elements 51 to 53. In this case, the spectroscope 1 can be regarded as a monochromator-type spectroscope or can also be regarded as a polychromator-type spectroscope that separates and detects light of a plurality of wavelengths from the measurement light L1.

Explanation of Reference Numerals

[0092] 1... spectroscope, 8... diffraction grating, 8a... diffraction surface, 10... first photodetector, 12... light source (monitor light source), 16... second photodetector, 17... mirror device, 18... fixing member, 21... support portion, 22... movable portion, 23... connecting portion, 24... first reflection surface, 25... second reflection surface, 26... coil (driving element), 41a... through hole (FIG. 4), 51... first detection element, 52... second detection element, 64... arithmetic unit, A... axis, DR... wavelength dispersion direction, L1... measurement light, L2... diffracted light, L3... monitor light, W1... aperture width, W2... width.

Claims

1. A support part, a movable part, a connecting part that connects the movable part to the support part so that the movable part can swing around a predetermined axis, and a first reflecting surface provided on the movable part, and a mirror device that reflects measurement light by the first reflecting surface at an angle corresponding to the rotation angle of the movable part around the axis, A diffraction grating having a diffraction surface, which outputs diffracted light dispersed according to the wavelength when the measurement light from the mirror device is incident on the diffraction surface, A first photodetector that detects the diffracted light output from the diffraction grating, The incident angle of the measurement light on the diffraction surface changes according to the rotation angle of the movable part, and the wavelength of the diffracted light detected by the first photodetector changes according to the incident angle of the measurement light on the diffraction surface, As an operation mode, a first mode of acquiring a detection result of the first photodetector in a state where the mirror device is driven so that the measurement light from the mirror device is incident on the diffraction surface, A second mode of acquiring a detection result of the first photodetector in a state where the mirror device is driven so that the measurement light from the mirror device travels outside the diffraction surface, a spectroscope.

2. In the second mode, the measurement light that travels along a predetermined optical axis and is incident on the first reflecting surface is reflected by the first reflecting surface so as to return along the optical axis. The spectroscope according to claim 1.

3. Further comprising a fixing member to which the mirror device is fixed, The mirror device further has a driving element for generating a driving force for swinging the movable part, The fixing member is formed of a metal material. The spectroscope according to claim 1 or 2.

4. Further comprising a fixing member to which the mirror device is fixed, a monitor light source that outputs monitor light, and a second photodetector that detects the monitor light, The mirror device further has a second reflecting surface provided on the movable part on the back side opposite to the front side where the first reflecting surface is provided, A through hole is formed in the fixing member, The mirror device is fixed to the fixing member so that the second reflecting surface faces the through hole, The monitor light output from the monitor light source is incident on the second reflecting surface through the through hole, reflected by the second reflecting surface, and detected by the second photodetector through the through hole. The spectroscope according to claim 1 or 2.

5. The spectroscope according to claim 4, wherein the through hole is formed in a tapered shape such that the width thereof becomes narrower as it approaches the mirror device.

6. The spectroscope according to claim 4, wherein an opening width of the through hole on the side of the mirror device is narrower than a width of the movable part of the mirror device.

7. The spectroscope according to claim 1 or 2, wherein the first photodetector includes a plurality of detection elements having mutually different sensitivity wavelength ranges.

8. The spectroscope according to claim 7, wherein the plurality of detection elements are arranged along a wavelength dispersion direction of the diffracted light at an incident position to the first photodetector.

9. The spectroscope according to claim 8, wherein a distance between the plurality of detection elements is 1 mm or less.

10. The spectroscope according to claim 7, wherein the plurality of detection elements are arranged along a direction perpendicular to a wavelength dispersion direction of the diffracted light at an incident position to the first photodetector.

11. The spectroscope further includes an arithmetic unit that receives a detection result of the first photodetector, wherein the arithmetic unit subtracts a value corresponding to the detection result of the first photodetector obtained in the second mode from a value corresponding to the detection result of the first photodetector obtained in the first mode. The spectroscope according to claim 1 or 2.

12. The spectroscope further includes an arithmetic unit that receives a detection result of the first photodetector, wherein the first photodetector includes a first detection element and a second detection element, (1) the first detection element has sensitivity in a wavelength range corresponding to the n-th order (n is an integer of 1 or more) and (n + 1)-th order diffracted light, the second detection element has sensitivity in a wavelength range corresponding to the (n + 1)-th order diffracted light, and the arithmetic unit subtracts a value corresponding to the detection result of the second detection element from a value corresponding to the detection result of the first detection element to calculate an output value of the n-th order diffracted light, or, (2) the first detection element has sensitivity in a wavelength range corresponding to the m-th order (m is an integer of -1 or less) and (m - 1)-th order diffracted light, the second detection element has sensitivity in a wavelength range corresponding to the (m - 1)-th order diffracted light, and the arithmetic unit subtracts a value corresponding to the detection result of the second detection element from a value corresponding to the detection result of the first detection element to calculate an output value of the m-th order diffracted light. The spectroscope according to claim 1 or 2.

13. The spectroscope further includes an arithmetic unit that receives a detection result of the first photodetector, The mirror device further has a drive element for generating a driving force for swinging the movable part. The arithmetic unit corrects the detection result of the first photodetector in the second mode based on an input signal to the drive element or an output value from the drive element. The spectroscope according to claim 1 or 2.

14. Each time the rotation angle of the movable part is changed to obtain the detection result of the first photodetector in the first mode, the detection result of the first photodetector in the second mode is obtained. The spectroscope according to claim 1 or 2.

15. Before or after obtaining the detection result of the first photodetector in the first mode a plurality of times while changing the rotation angle of the movable part, the detection result of the first photodetector in the second mode is obtained. The spectroscope according to claim 1 or 2.

16. A measurement method using a spectroscope, The spectroscope is a support part, a movable part, a connecting part that connects the movable part to the support part so that the movable part can swing around a predetermined axis, and a first reflecting surface provided on the movable part. A mirror device that reflects the measurement light by the first reflecting surface at an angle corresponding to the rotation angle of the movable part around the axis, a diffraction grating having a diffraction surface, and outputting diffracted light dispersed according to the wavelength when the measurement light from the mirror device is incident on the diffraction surface, a first photodetector that detects the diffracted light output from the diffraction grating, the incident angle of the measurement light on the diffraction surface changes according to the rotation angle of the movable part, and the wavelength of the diffracted light detected by the first photodetector changes according to the incident angle of the measurement light on the diffraction surface, The measurement method is a first step of obtaining a detection result of the first photodetector in a state where the mirror device is driven so that the measurement light from the mirror device is incident on the diffraction surface, a second step of obtaining a detection result of the first photodetector in a state where the mirror device is driven so that the measurement light from the mirror device travels outside the diffraction surface. A measurement method.

17. The measurement method according to claim 16 further includes a third step of subtracting a value corresponding to the detection result of the first photodetector obtained in the second step from a value corresponding to the detection result of the first photodetector obtained in the first step.

18. The first photodetector includes a first detection element and a second detection element. (1) The first detection element has sensitivity in a wavelength range corresponding to the n-th order (n is an integer of 1 or more) and (n + 1)-th order diffracted light, and the second detection element has sensitivity in a wavelength range corresponding to the (n + 1)-th order diffracted light. In the measurement method, by subtracting the value corresponding to the detection result of the second detection element from the value corresponding to the detection result of the first detection element, the output value of the n-th order diffracted light is calculated, or (2) The first detection element has sensitivity in a wavelength range corresponding to the m-th order (m is an integer of -1 or less) and (m - 1)-th order diffracted light, and the second detection element has sensitivity in a wavelength range corresponding to the (m - 1)-th order diffracted light. In the measurement method, by subtracting the value corresponding to the detection result of the second detection element from the value corresponding to the detection result of the first detection element, the output value of the m-th order diffracted light is calculated. The measurement method according to claim 16.

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