Spectroscopic unit and spectroscopic module

Abstract

To provide a spectroscopic unit and spectroscopic module that can perform measurements with high precision. [Solution] The spectroscopic unit 110 includes a Fabry-Perot interference filter 10 having a pair of mirrors whose distance from each other is variable, an optical system 50 having a first lens 51 that focuses light from an object M onto the Fabry-Perot interference filter 10, and a photodetector 8 that detects light transmitted through the Fabry-Perot interference filter 10. When the distance D1 from the first lens 51 to the object M is 5 cm, and a circular area on the surface of the object M with a diameter D2 of 1 cm is defined as the field of view region A, the optical system 50 is configured to allow light with a divergence angle of 1 degree or less to enter the light transmission region of the Fabry-Perot interference filter 10, while preventing light with a divergence angle greater than 1 degree from entering the light transmission region of the Fabry-Perot interference filter 10 from entering the light transmission region.

Description

Technical Field

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[0001] The present invention relates to a spectroscopic unit and a spectroscopic module.

Background Art

[0002] A spectroscopic module including a light source that emits light to an object, a spectroscopic unit that spectrally analyzes the light from the object, and a light detection element that detects the light spectrally analyzed by the spectroscopic unit is known (see, for example, Patent Document 1). According to such a spectroscopic module, for example, the components of an object can be measured nondestructively.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In measurement using a spectroscopic module, scattered light (signal light) emitted from an object upon receiving light emitted from a light source is detected. However, not only the scattered light that should originally be detected but also noise light such as specularly reflected light of the light emitted from the light source on the surface of the object and external disturbance light is detected together, and there is a risk that the measurement accuracy of the spectroscopic module will decrease.

[0005] An object of the present invention is to provide a spectroscopic unit and a spectroscopic module capable of performing measurement with high accuracy.

Means for Solving the Problems

[0006] The spectroscopic unit of the present invention is a spectroscopic unit comprising: [1] a Fabry-Perot interference filter having a pair of mirrors whose distance from each other is variable; an optical system having a first lens that focuses light from an object onto the Fabry-Perot interference filter; and a photodetector that detects the light transmitted through the Fabry-Perot interference filter, wherein when the distance from the first lens to the object is 5 cm and the field of view is defined as a circular region on the surface of the object having a diameter of 1 cm, the optical system is configured such that, of the light incident on the first lens from the field of view, light with a divergence angle greater than 1 degree is not incident on the light transmission region of the Fabry-Perot interference filter, and light with a divergence angle of 1 degree or less is incident on the light transmission region.

[0007] In the above-described spectroscopic unit, when the distance from the first lens to the object is 5 cm and the field of view is defined as a circular area on the surface of the object with a diameter of 1 cm, the optical system is configured to allow light with a divergence angle of 1 degree or less to enter the light transmission region of the Fabry-Perot interference filter, while preventing light with a divergence angle greater than 1 degree from entering the light transmission region of the Fabry-Perot interference filter. Generally, since the light source is positioned at a distance from the optical axis of the light directed toward the Fabry-Perot interference filter, noise light such as specular reflection from the surface of the object has an angle of 1 degree or more. Therefore, with the above-described spectroscopic unit, such noise light does not enter the photodetector element through the light transmission region of the Fabry-Perot interference filter. As a result, a decrease in measurement accuracy caused by noise light can be suppressed. Furthermore, the field of view is a relatively large circular area with a diameter of 1 cm, and light with a divergence angle of 1 degree or less enters the light transmission region from this field of view. In other words, light can be guided from a wide area on the surface of the object to the light transmission region, and the amount of light detected by the photodetector element can be increased. Therefore, the above-mentioned spectroscopic unit allows for measurements with high accuracy.

[0008] The spectroscopic unit of the present invention may also be [2] "the spectroscopic unit according to [1] above, wherein the pair of mirror portions face each other in a predetermined direction, and when viewed from the predetermined direction, the outer edge of the first lens is larger than the outer edge of the Fabry-Perot interference filter." In this case, the optical system can guide light from a wider area on the surface of the object to the light transmission region of the Fabry-Perot interference filter via the first lens, thereby increasing the amount of light detected by the photodetector. Furthermore, by guiding light from a wide area to the light transmission region of the Fabry-Perot interference filter, the light signals detected by the photodetector are averaged, and variations in measurement results caused by the measurement position on the surface of the object can be suppressed.

[0009] The spectroscopic unit of the present invention may also be [3] "the spectroscopic unit according to [1] or [2] above, wherein the photodetector is a single-channel element." In this case, the spectral spectrum of scattered light emitted from the object can be reliably obtained. That is, for example, in a multi-channel photodetector that outputs signals from multiple pixels, the amount of signal light can change greatly depending on the shape of the position on the surface of the object corresponding to that pixel (even if a large field of view is secured, only a portion of the area corresponds to each pixel). In contrast, in the present invention, since the light incident on the photodetector from a relatively large field of view via a Fabry-Perot interference filter is output as a single signal, the signal from the entire field of view is averaged, reducing the variation in the signal depending on the position and making it possible to obtain a stable signal.

[0010] The spectroscopic unit of the present invention may also be [4] "the spectroscopic unit according to any one of [1] to [3] above, wherein the pair of mirrors face each other in a predetermined direction, the optical system has a second lens located between the first lens and the Fabry-Perot interference filter, and the second lens is configured such that the angle of light transmitted through the second lens with respect to the predetermined direction is smaller than the angle of light incident on the second lens with respect to the predetermined direction." The transmission wavelength of the Fabry-Perot interference filter changes depending on the angle of incidence of light (it is dependent on the angle of incidence). According to the spectroscopic unit, the angle of light incident on the Fabry-Perot interference filter can be made nearly parallel to the opposing direction (predetermined direction) of the pair of mirrors, and light of a desired wavelength can be transmitted with good resolution in the Fabry-Perot interference filter. Furthermore, even when a condensing lens with a large width and condensing angle (e.g., the first lens) is placed in close proximity to the Fabry-Perot interference filter, good resolution can be obtained by using the second lens, thus enabling the spectroscopic module to which the spectroscopic unit is applied to be made more compact.

[0011] The spectroscopic unit of the present invention may also be [5] "the spectroscopic unit according to [4] above, wherein the second lens is formed separately from the first lens." In this case, the degree of freedom in the arrangement and design of the first and second lenses can be improved.

[0012] The spectroscopic unit of the present invention may also be the spectroscopic unit described in [4] above, wherein the second lens is integrally formed with the first lens. In this case, the spectroscopic unit can be realized with a simple configuration with a small number of parts.

[0013] The spectroscopic unit of the present invention may also be [7] "the spectroscopic unit according to any one of [1] to [6] above, further comprising a bandpass filter located between the first lens and the Fabry-Perot interference filter." In this case, unwanted wavelengths of light can be cut off by the bandpass filter, and only light of the desired wavelengths can be incident on the Fabry-Perot interference filter. Therefore, measurements can be performed with higher accuracy.

[0014] The spectroscopic unit of the present invention may also be [8] "the spectroscopic unit according to any one of [1] to [7] above, wherein the pair of mirror portions face each other in a predetermined direction, and when viewed from the predetermined direction, the width of the first lens is at least twice the width of the light transmission region." In this case, the optical system can guide light from a wider area on the surface of the object through the first lens to the light transmission region of the Fabry-Perot interference filter, thereby increasing the amount of light detected by the photodetector.

[0015] The spectroscopic unit of the present invention may also be [9] "the spectroscopic unit according to any one of [1] to [8] above, wherein the pair of mirror portions face each other in a predetermined direction, and when viewed from the predetermined direction, the width of the first lens is 10 times or more the width of the light transmission region." In this case, the optical system can guide light from a wider area on the surface of the object to the light transmission region of the Fabry-Perot interference filter via the first lens, thereby increasing the amount of light detected by the photodetector.

[0016] The spectroscopic module of the present invention is

[10] "a spectroscopic module comprising a spectroscopic unit described in any one of [1] to [9] above, and a package housing the spectroscopic unit, wherein the package has a light incident portion into which light from the object is incident, and the first lens is located in the light incident portion." In this case, the spectroscopic unit can be protected by the package. Furthermore, in the packaged spectroscopic module, light can be incident into the package via the first lens located in the light incident portion.

[0017] The spectroscopic module of the present invention may also be

[11] "the spectroscopic module according to

[10] above, wherein the package has a cylindrical portion, the first lens is disposed inside the cylindrical portion, and when viewed from the extending direction of the cylindrical portion, the light transmission region is located inside the cylindrical portion." In this case, the light focused by the first lens can be efficiently incident onto the light transmission region of the Fabry-Perot interference filter.

[0018] The spectroscopic module of the present invention may also be

[12] "the spectroscopic module according to

[11] above, wherein the package further comprises a main body portion that houses the Fabry-Perot interference filter, the cylindrical portion is connected to the main body portion so as to protrude from the main body portion, and the light incident portion is formed at the end of the cylindrical portion that protrudes from the main body portion." In this case, a space between the first lens and the Fabry-Perot interference filter can be provided within the cylindrical portion, making the main body portion more compact. Furthermore, when using the spectroscopic module, the light incident portion (first lens) can be brought close to the object while holding the main body portion.

[0019] The spectroscopic module of the present invention may also be

[13] "the spectroscopic module according to

[11] or

[12] above, further comprising a plurality of light sources that emit light toward the object, wherein the plurality of light sources are located along the circumferential direction of the cylindrical portion." In this case, the object can be uniformly irradiated with light from the plurality of light sources, and measurements can be performed with higher accuracy. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a spectroscopic unit and spectroscopic module that can perform measurements with high accuracy. [Brief explanation of the drawing]

[0021] [Figure 1] This is a cross-sectional view of a photodetector applied to a spectroscopic module of one embodiment. [Figure 2]It is a plan view of the photodetection device shown in FIG. 1. [Figure 3] It is a perspective view of the Fabry - Perot interference filter shown in FIG. 1. [Figure 4] It is a cross - sectional view of the Fabry - Perot interference filter along the IV - IV line shown in FIG. 3. [Figure 5] It is a perspective view of the spectroscopic module of one embodiment. [Figure 6] It is a perspective view of the spectroscopic module of one embodiment. <000009​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Embodiments of the present invention will be described in detail below with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are omitted. [Photodetector]

[0023] First, a photodetector 1 applied to a spectroscopic module according to one embodiment will be described. The photodetector 1 is, for example, a MEMS-FPI sensor. As shown in Figure 1, the photodetector 1 comprises a housing 2. The housing 2 is a CAN package having a stem 3 and a cap 4. The cap 4 includes a side wall 5 and a top wall 6. The side wall 5 and the top wall 6 are integrally formed from a metal material. The top wall 6 is integrally formed with the side wall 5 so as to cover one opening of the cylindrical side wall 5. The stem 3 is made of a metal material. The stem 3 is hermetically bonded to the side wall 5 so as to cover the other opening of the cylindrical side wall 5.

[0024] A wiring board 7 is fixed to the inner surface 3a of the stem 3. The substrate material of the wiring board 7 is, for example, silicon, ceramic, quartz, glass, plastic, etc. A photodetector 8 and a temperature compensation element such as a thermistor (not shown) are mounted on the wiring board 7. The photodetector 8 is, for example, an infrared detector. As an infrared detector, for example, a quantum type sensor using InGaAs, a thermopile, or a bolometer can be used. When detecting light in the ultraviolet, visible, and near-infrared wavelength ranges, for example, a silicon photodiode can be used as the photodetector 8. In this example, the photodetector 1 has one photodetector 8 (photodetector). The photodetector 8 is a single-channel element. A single-channel element is an element that outputs a single electrical signal, regardless of whether it has a single light-receiving region (single photoelectric conversion region) or multiple light-receiving regions (multiple photoelectric conversion regions). In a single-channel element with multiple light-receiving regions, for example, the current values ​​obtained from the multiple light-receiving regions are added together to produce a single electrical signal.

[0025] Multiple spacers 9 are fixed to the wiring board 7. The material of each spacer 9 is, for example, silicon, ceramic, quartz, glass, or plastic. A Fabry-Perot interference filter 10 is fixed to the multiple spacers 9. That is, the Fabry-Perot interference filter 10 is supported by multiple spacers 9. The light-transmitting region 10a of the Fabry-Perot interference filter 10 faces the light-receiving portion of the photodetector element 8. The spacers 9 may be formed integrally with the wiring board 7. The Fabry-Perot interference filter 10 may be supported by a single spacer 9.

[0026] Multiple lead pins 11 are fixed to the stem 3. Each lead pin 11 penetrates the stem 3, with electrical insulation and airtightness ensured between it and the stem 3 by an insulating member 17. Each lead pin 11 is electrically connected via wires 12 to electrode pads provided on the wiring board 7, terminals of the photodetector 8, terminals of the temperature compensation element, and terminals of the Fabry-Perot interference filter 10, respectively. In the photodetector 1, electrical signals are input and output to the photodetector 8, temperature compensation element, and Fabry-Perot interference filter 10, respectively, via the multiple lead pins 11.

[0027] The housing 2 has an opening 20. The opening 20 is formed in the top wall 6 of the cap 4 so as to face the light transmission region 10a of the Fabry-Perot interference filter 10. A light-transmitting member 13 is hermetically bonded to the inner surface 6a of the top wall 6. The light-transmitting member 13 closes the opening 20. The light-transmitting member 13 has a light-incident surface 13a and a light-emitting surface 13b that face each other, as well as a side surface 13c. The light-incident surface 13a of the light-transmitting member 13 is substantially flush with the outer surface 6b of the top wall 6 in the opening 20. The side surface 13c of the light-transmitting member 13 is in contact with the inner surface 5a of the side wall 5 of the cap 4. Such a light-transmitting member 13 is formed by placing glass pellets inside the cap 4 with the opening 20 facing downwards and melting the glass pellets.

[0028] A bandpass filter 14 is fixed to the light-emitting surface 13b of the light-transmitting member 13 by a light-transmitting adhesive member 15. For example, the bandpass filter 14 selectively transmits light within the measurement wavelength range of the photodetector 1 from the light transmitted through the light-transmitting member 13. The bandpass filter 14 has a light-incident surface 14a and a light-emitting surface 14b, as well as a side surface 14c that are opposite to each other. The side surface 14c of the bandpass filter 14 is spaced apart from the inner surface 5a of the side wall 5 of the cap 4. As an example, the bandpass filter 14 includes a light-transmitting member formed in the shape of a rectangular plate from a light-transmitting material (e.g., silicon, glass, etc.) and a dielectric multilayer film (e.g., a multilayer film consisting of a combination of a high refractive index material such as TiO2 or Ta2O5 and a low refractive index material such as SiO2 or MgF2) formed on the surface of the light-transmitting member opposite to the opening 20. The dielectric multilayer film may be formed on the surface of the light-transmitting member on the side of the opening 20.

[0029] In this embodiment, the light-transmitting section 16 is composed of a light-transmitting member 13, an adhesive member 15, and a bandpass filter 14. That is, the light-transmitting section 16 includes a light-transmitting member 13 that closes the opening 20, and a bandpass filter 14 positioned on the opposite side of the opening 20 from the light-transmitting member 13. The light-incident surface 16a of the light-transmitting section 16 is the light-incident surface 13a of the light-transmitting member 13, and the light-emitting surface 16b of the light-transmitting section 16 is the light-emitting surface 14b of the bandpass filter 14. The light-emitting surface 16b of the light-transmitting section 16 is located inside the housing 2.

[0030] The light detection device 1 includes an aperture section 151A having an aperture 150. The aperture 150 is a light passage hole located within the housing 2 between the light emission surface 16b of the light transmission section 16 and the Fabry-Perot interference filter 10. As shown in Figures 1 and 2, the aperture section 151A is composed of a plate-shaped first surrounding section 152. When viewed from direction B1, the first surrounding section 152 continuously surrounds the aperture 150. Direction B1 is the opposing direction of the pair of mirror sections (the first mirror section 35 and the second mirror section 36, described later) of the Fabry-Perot interference filter 10. When viewed from direction B1, the outer edge 150a of the aperture 150 is located inside the outer edge 20a of the opening 20 of the housing 2. The first surrounding section 152 is positioned within the housing 2 between the light transmission section 16 and the Fabry-Perot interference filter 10. The first enclosing portion 152 has a pair of opposing surfaces 152a, 152b and a side surface 152c. Surface 152a is the surface on the light-transmitting portion 16 side and is in contact with the light-emitting surface 16b of the light-transmitting portion 16 (i.e., the light-emitting surface 14b of the bandpass filter 14). Surface 152b is the surface on the Fabry-Perot interference filter 10 side and is spaced apart from the Fabry-Perot interference filter 10.

[0031] Of the outer surface of the first enclosing portion 152, at least the surface 152b on the Fabry-Perot interference filter 10 side has light-absorbing properties. For example, the outer surface of the first enclosing portion 152, which is formed in a plate shape from aluminum, stainless steel, etc., can be subjected to chrome plating, black anodizing, electroless nickel plating, black paint coating, etc. (a roughening treatment may also be applied), thereby imparting light-absorbing properties to the outer surface of the first enclosing portion 152 for light in the visible to near-infrared wavelength range. Note that not only surface 152b, but also surface 152a may have light-absorbing properties.

[0032] The positioning of the aperture portion 151A in the direction perpendicular to direction B1 is performed by the first surrounding portion 152 and the housing 2. Specifically, the positioning of the aperture portion 151A in the direction perpendicular to direction B1 is performed by the fit between the side surface 152c of the first surrounding portion 152 and the inner surface 5a of the side wall 5 of the cap 4. The positioning of the aperture portion 151A in direction B1 is performed by the first surrounding portion 152 and the light-transmitting portion 16. Specifically, the positioning of the aperture portion 151A in direction B1 is performed by the contact between the surface 152a of the first surrounding portion 152 and the light-emitting surface 16b of the light-transmitting portion 16.

[0033] With the aperture portion 151A positioned, the first enclosing portion 152 is fixed to at least one of the housing 2 and the light-transmitting portion 16. Specifically, the first enclosing portion 152 is fixed to at least one of the housing 2 and the light-transmitting portion 16 by at least one of the following: an adhesive member (not shown) positioned between the side surface 14c of the bandpass filter 14 and the inner surface 5a of the side wall 5; an adhesive member (not shown) positioned at the corner formed by the surface 152b of the first enclosing portion 152 and the inner surface 5a of the side wall 5; and an adhesive member (not shown) positioned between the light-emitting surface 14b of the bandpass filter 14 and the surface 152a of the first enclosing portion 152.

[0034] In the first embodiment, the opening 20 of the housing 2, the aperture 150 of the aperture portion 151A, the light transmission region 10a of the Fabry-Perot interference filter 10, and the light receiving region of the photodetector 8 are arranged on line L in this order. When viewed from a direction parallel to line L, line L passes through the centers of the opening 20, the aperture 150, the light transmission region 10a, and the light receiving region, respectively. In other words, in the photodetector 1, the Fabry-Perot interference filter 10 is positioned in the housing 2 on the opposite side of the opening 20 from the light emission surface 16b of the light transmission portion 16, and the photodetector 8 is positioned in the housing 2 on the opposite side of the opening 20 from the Fabry-Perot interference filter 10.

[0035] In the light detection device 1 configured as described above, when the light to be measured is incident on the light transmission region 10a of the Fabry-Perot interference filter 10 via the aperture 20, the light transmission section 16 (i.e., the light transmission member 13, the adhesive member 15, and the bandpass filter 14) and the aperture 150, light of a predetermined wavelength from the light to be measured is transmitted through the pair of mirror sections of the Fabry-Perot interference filter 10. The light transmitted through the pair of mirror sections of the Fabry-Perot interference filter 10 is incident on the photodetector element 8 and detected by the photodetector element 8. As an example, in order to obtain the spectral spectrum of the light to be measured, the light detection device 1 is configured such that the voltage applied to the Fabry-Perot interference filter 10 is changed (i.e., the distance between the pair of mirror sections in the Fabry-Perot interference filter 10 is changed), and the light transmitted through the light transmission region 10a of the Fabry-Perot interference filter 10 is detected by the photodetector element 8. By detecting the intensity of the light transmitted through the light transmission region 10a with the photodetector element 8, a spectral spectrum can be obtained.

[0036] [Fabry-Perot interference filter] The Fabry-Perot interference filter 10 described above will now be explained in more detail. As shown in Figures 3 and 4, the Fabry-Perot interference filter 10 has a light-transmitting region 10a that transmits light of a wavelength corresponding to the distance between the first mirror portion 35 and the second mirror portion 36. The light-transmitting region 10a is, for example, a cylindrical region with line L as its centerline.

[0037] The Fabry-Perot interference filter 10 includes a substrate 21. The substrate 21 is, for example, a rectangular plate. The material of the substrate 21 is, for example, silicon, quartz, or glass. The substrate 21 has a first surface 21a and a second surface 21b that face each other in a direction parallel to the line L. The first surface 21a is the surface on the light incident side (bandpass filter 14 side). The second surface 21b is the surface on the light emission side (photodetector 8 side).

[0038] A first layer structure 30 is arranged on the first surface 21a of the substrate 21. The first layer structure 30 is formed by stacking a first anti-reflective layer 31, a first laminate 32, a first intermediate layer 33, and a second laminate 34 on the first surface 21a in this order. An air gap S is formed between the first laminate 32 and the second laminate 34 by a frame-shaped first intermediate layer 33. When the material of the substrate 21 is silicon, the material of the first anti-reflective layer 31 and the first intermediate layer 33 is, for example, silicon oxide. The thickness of the first intermediate layer 33 is, for example, several tens of nanometers to several tens of micrometers.

[0039] The portion of the first laminate 32 corresponding to the light-transmitting region 10a functions as the first mirror portion 35. The first laminate 32 is composed of multiple polysilicon layers and multiple silicon nitride layers stacked alternately one layer at a time. Preferably, the optical thickness of each of the polysilicon layer and silicon nitride layer constituting the first mirror portion 35 is an integer multiple of 1 / 4 of the central transmission wavelength of light transmitted through the light-transmitting region 10a. The first mirror portion 35 may be placed on the first surface 21a of the substrate 21 without the first anti-reflective layer 31.

[0040] The portion of the second laminate 34 corresponding to the light-transmitting region 10a functions as a second mirror portion 36. The second mirror portion 36 faces the first mirror portion 35 via an air gap S in a direction parallel to the line L (a predetermined direction). The second laminate 34 is constructed by alternately stacking multiple polysilicon layers and multiple silicon nitride layers one layer at a time. Preferably, the optical thickness of each polysilicon layer and silicon nitride layer constituting the second mirror portion 36 is an integer multiple of 1 / 4 of the central transmission wavelength of light transmitted through the light-transmitting region 10a.

[0041] In the first laminate 32 and the second laminate 34, a silicon oxide layer may be provided instead of a silicon nitride layer. The materials of each layer constituting the first laminate 32 and the second laminate 34 are not limited to the materials described above, and may include, for example, titanium oxide, tantalum oxide, zirconium oxide, magnesium fluoride, aluminum oxide, calcium fluoride, silicon, germanium, or zinc sulfide.

[0042] Multiple through-holes 34b are formed in the portion of the second laminate 34 corresponding to the void S. Each through-hole 34b extends from the surface 34a of the second laminate 34 opposite to the first laminate 32 to the void S. The multiple through-holes 34b are formed to such an extent that they do not substantially affect the function of the second mirror portion 36. The multiple through-holes 34b were used to form the void S by removing a portion of the first intermediate layer 33 by etching.

[0043] A first electrode 22 is formed in the first laminate 32 so as to surround the light-transmitting region 10a. A second electrode 23 is formed in the first laminate 32 so as to include the light-transmitting region 10a. The first electrode 22 and the second electrode 23 are formed by doping the polysilicon layer closest to the void S in the first laminate 32 with impurities to reduce its resistance. A third electrode 24 is formed in the second laminate 34 so as to face the first electrode 22 and the second electrode 23 across the void S. The third electrode 24 is formed by doping the polysilicon layer closest to the void S in the second laminate 34 with impurities to reduce its resistance. The second electrode 23 only needs to be approximately the same size as or larger than the light-transmitting region 10a.

[0044] The first layer structure 30 is provided with a pair of first terminals 25 and a pair of second terminals 26. The pair of first terminals 25 face each other across a light-transmitting region 10a. Each first terminal 25 is located in a through hole extending from the surface 34a of the second laminate 34 to the first laminate 32. Each first terminal 25 is electrically connected to the first electrode 22 via wiring 22a formed in the first laminate 32. The pair of second terminals 26 face each other across a light-transmitting region 10a in a direction perpendicular to the direction in which the pair of first terminals 25 face each other. Each second terminal 26 is located in a through hole extending from the surface 34a of the second laminate 34 to the interior of the first intermediate layer 33. Each second terminal 26 is electrically connected to the second electrode 23 via wiring 23a formed in the first laminate 32, and is also electrically connected to the third electrode 24 via wiring 24a formed in the second laminate 34.

[0045] Trenches 27 and 28 are provided on the surface 32a of the first laminate 32 facing the second laminate 34. Trench 27 extends in an annular shape to surround the connection portion between the wiring 23a and the second terminal 26. Trench 27 electrically insulates the first electrode 22 from the wiring 23a. Trench 28 extends in an annular shape along the inner edge of the first electrode 22. Trench 28 electrically insulates the first electrode 22 from the region inside the first electrode 22 (i.e., the region where the second electrode 23 exists). Trench 29 is provided on the surface 34a of the second laminate 34. Trench 29 extends in an annular shape to surround the first terminal 25. Trench 29 electrically insulates the first terminal 25 from the third electrode 24. The regions within each of the trenches 27, 28, and 29 may be made of insulating material or may be voids.

[0046] A second layer structure 40 is arranged on the second surface 21b of the substrate 21. The second layer structure 40 is constructed by stacking a second anti-reflective layer 41, a third laminate 42, a second intermediate layer 43, and a fourth laminate 44 on the second surface 21b in this order. The second anti-reflective layer 41, the third laminate 42, the second intermediate layer 43, and the fourth laminate 44 have the same configuration as the first anti-reflective layer 31, the first laminate 32, the first intermediate layer 33, and the second laminate 34, respectively. In other words, the second layer structure 40 has a stacked structure that is symmetrical to the first layer structure 30 with respect to the substrate 21. By configuring the second layer structure 40 to correspond to the first layer structure 30, warping of the Fabry-Perot interference filter 10 is suppressed.

[0047] The third laminate 42, the second intermediate layer 43, and the fourth laminate 44 have an opening 40a that includes a light-transmitting region 10a. The opening 40a is cylindrical in shape, for example, with line L as its centerline, and has approximately the same diameter as the light-transmitting region 10a. The opening 40a opens on the light-emitting side, and the bottom surface of the opening 40a extends to the second anti-reflective layer 41. The opening 40a allows light transmitted through the first mirror portion 35 and the second mirror portion 36 to pass through.

[0048] A light-shielding layer 45 is formed on the light-emitting surface of the fourth laminate 44. The material of the light-shielding layer 45 is, for example, aluminum. A protective layer 46 is formed on the surface of the light-shielding layer 45 and on the inner surface of the opening 40a. The material of the protective layer 46 is, for example, aluminum oxide. By setting the thickness of the protective layer 46 to 1 to 100 nm (preferably about 30 nm), the optical influence of the protective layer 46 can be ignored.

[0049] In the Fabry-Perot interference filter 10 configured as described above, when a voltage is applied between the first terminal 25 and the second terminal 26, a potential difference is generated between the first electrode 22 and the third electrode 24, and an electrostatic force corresponding to this potential difference is generated between the first electrode 22 and the third electrode 24. As a result, the second mirror portion 36 is attracted to the first mirror portion 35 fixed to the substrate 21, and the distance between the first mirror portion 35 and the second mirror portion 36 changes. At this time, no potential difference is generated between the second electrode 23 and the third electrode 24, so the flatness of the second mirror portion 36 in the light transmission region 10a is ensured. Thus, in the Fabry-Perot interference filter 10, the distance between the first mirror portion 35 and the second mirror portion 36 is variable. Here, the wavelength of light transmitted through the light transmission region 10a depends on the distance between the first mirror portion 35 and the second mirror portion 36. Therefore, by adjusting the voltage applied between the first terminal 25 and the second terminal 26, the wavelength of light transmitted through the light-transmitting region 10a can be adjusted.

[0050] [Spectroscopic Module] Referring to Figures 5 to 9, a spectral module 100 in one embodiment to which the above-described photodetector 1 is applied will be described. In the following description, the direction in which the first mirror section 35 and the second mirror section 36 face each other (in this example, the direction parallel to line L) is referred to as the Z-axis direction, one direction perpendicular to the Z-axis direction is referred to as the X-axis direction, and the direction perpendicular to both the Z-axis direction and the X-axis direction is referred to as the Y-axis direction. The spectral module 100 emits light toward an object and detects the light from the object.

[0051] The spectroscopic module 100 comprises a spectroscopic unit 110, a package 120 housing the spectroscopic unit 110, and a ring illumination 130 that emits light toward an object. For the sake of clarity, the ring illumination 130 is not shown in Figures 6 and 7. As shown in Figure 7, the spectroscopic unit 110 includes a photodetector 1, an optical system 50, a control board 61, and a control board 62.

[0052] The optical system 50 includes a first lens 51 and a second lens 52. In this example, the first lens 51 and the second lens 52 are formed separately from each other. The first lens 51 and the second lens 52 are aligned in the Z-axis direction. The second lens 52 is located between the first lens 51 and the Fabry-Perot interference filter 10. That is, the first lens 51, the second lens 52, and the Fabry-Perot interference filter 10 are aligned in this order in the Z-axis direction. A bandpass filter 14 is positioned between the optical system 50 and the Fabry-Perot interference filter 10. That is, the bandpass filter 14 is located between the first lens 51 and the Fabry-Perot interference filter 10.

[0053] The first lens 51 is a lens that focuses light from an object measured by the spectroscopic module 100 onto the Fabry-Perot interference filter 10 of the photodetector 1. As shown in Figure 8, the first lens 51 has a circular shape when viewed from the Z-axis direction. In Figure 8, the diagrams of components other than the first lens 51, the second lens 52, and the Fabry-Perot interference filter 10 are omitted. The first lens 51 includes a surface 51a, a surface 51b, and a side surface 51c.

[0054] Surface 51a is the surface of the first lens 51 opposite to the second lens 52. Surface 51a is curved so as to be convex in the direction away from the second lens 52. That is, surface 51a is a curved surface that protrudes outward from the first lens 51. Surface 51b is the surface of the first lens 51 on the side facing the second lens 52. Surface 51b is located on the opposite side from surface 51a. Surface 51b extends perpendicular to the Z-axis direction. Side surface 51c extends in an annular shape when viewed from the Z-axis direction. Light from the object enters the interior of the first lens 51 from surface 51a and then exits to the second lens 52 from surface 51b.

[0055] The second lens 52 is, for example, a collimating lens. As shown in Figure 9, the second lens 52 is configured such that the angle θ1 of light transmitted through the second lens 52 with respect to the Z-axis direction is smaller than the angle θ2 of light incident on the second lens 52 with respect to the Z-axis direction. As shown in Figure 8, when viewed from the Z-axis direction, the second lens 52 has a circular shape. The second lens 52 includes a surface 52a, a surface 52b, and a side surface 52c.

[0056] Surface 52a is the surface of the second lens 52 that faces the first lens 51. Surface 52a extends perpendicular to the Z-axis direction. Surface 52b is the surface of the second lens 52 that faces the first lens 51. Surface 52b is located on the opposite side from surface 52a. Surface 52b is curved so as to be concave in the direction toward the first lens 51. That is, surface 52b is a curved surface that is concave toward the inside of the second lens 52. Side surface 52c extends in an annular shape when viewed from the Z-axis direction. Light from the object (light transmitted through the first lens 51) enters the interior of the second lens 52 from surface 52a and is then emitted from surface 52b to the photodetector 1.

[0057] As shown in Figure 8, the first lens 51, the second lens 52, and the Fabry-Perot interference filter 10 overlap each other in the Z-axis direction. When viewed from the Z-axis direction, the outer edge 51d of the first lens 51 is larger than the outer edge 52d of the second lens 52. The outer edge 51d is located outside the outer edge 52d. When viewed from the Z-axis direction, the width W1 of the first lens 51 is larger than the width W2 of the second lens 52. Width W1 is the maximum width of the first lens 51, and width W2 is the maximum width of the second lens 52. In this example, width W1 is the diameter of the first lens 51 when viewed from the Z-axis direction, and width W2 is the diameter of the second lens 52 when viewed from the Z-axis direction. Width W1 may be more than twice or more than four times the width W2. Width W1 may be, for example, about 15 mm. Width W2 may be, for example, about 6 mm.

[0058] When viewed from the Z-axis direction, the outer edge 51d of the first lens 51 is larger than the outer edge 10b of the Fabry-Perot interference filter 10. The outer edge 51d is located outside the outer edge 10b. When viewed from the Z-axis direction, the width W1 of the first lens 51 is larger than the width W3 of the Fabry-Perot interference filter 10. Width W3 is the maximum width of the Fabry-Perot interference filter 10. In this example, width W3 is the length of the diagonal of the Fabry-Perot interference filter 10 when viewed from the Z-axis direction. Width W1 may be more than twice or more than four times the width W3. When viewed from the Z-axis direction, the width W1 of the first lens 51 is larger than the width W4 of the light transmission region 10a of the Fabry-Perot interference filter 10. Width W4 is the maximum width of the light transmission region 10a. In this example, width W4 is the diameter of the light transmission region 10a when viewed from the Z-axis direction. In this example, width W1 is more than 10 times the width W4.

[0059] When viewed from the Z-axis direction, the outer edge 52d of the second lens 52 is larger than the outer edge 10b of the Fabry-Perot interference filter 10. The outer edge 52d is located outside the outer edge 10b. When viewed from the Z-axis direction, the width W2 of the second lens 52 is larger than the width W3 of the Fabry-Perot interference filter 10. The width W2 may be more than twice or more than four times the width W3. When viewed from the Z-axis direction, the width W2 of the second lens 52 is larger than the width W4 of the light transmission region 10a. In this example, the width W4 is approximately 0.75 mm. The size of the width W4 is not limited.

[0060] Control boards 61 and 62 are arranged so as to overlap each other in the Z-axis direction. The housing 2 is positioned on the surface 61a of control board 61. The housing 2 is positioned in the area of ​​surface 61a that does not overlap with control board 62. The housing 2 is fixed to control board 61 by a plurality of lead pins 11 that penetrate through control board 61 and are fixed to control board 61.

[0061] Package 120 has a main body 121 (module case) and a cylindrical part 125 (lens holder) that extends from the main body 121. The main body 121 has a roughly rectangular parallelepiped shape. The main body 121 houses the photodetector 1, control board 61 and control board 62. That is, the main body 121 houses the Fabry-Perot interference filter 10. The main body 121 has a pair of wall parts 121a, 121b, a pair of wall parts 121c, 121d and a pair of wall parts 121e, 121f. Wall part 121a is located on the opposite side of wall part 121b in the Z-axis direction. Wall part 121c is located on the opposite side of wall part 121d in the X-axis direction. Wall part 121e is located on the opposite side of wall part 121f in the Y-axis direction. The light detection device 1 is housed closer to wall 121f than to wall 121e. The control boards 61 and 62 are housed such that control board 61 is located between control board 62 and wall 121b.

[0062] An opening 122 is formed in the wall portion 121a into which the cylindrical portion 125 is inserted. The inner edge of the opening 122 is circular when viewed from the Z-axis direction. The opening 122 is formed closer to the wall portion 121f than to the wall portion 121e. When viewed from the Z-axis direction, the Fabry-Perot interference filter 10 is located inside the opening 122.

[0063] The cylindrical portion 125 extends along the Z-axis direction. That is, the central axis of the cylindrical portion 125 is aligned with the Z-axis direction. The optical system 50 (first lens 51 and second lens 52) is arranged inside the cylindrical portion 125. When viewed from the Z-axis direction (the direction in which the cylindrical portion 125 extends), the light transmission region 10a of the Fabry-Perot interference filter 10 is located inside the cylindrical portion 125. The cylindrical portion 125 is fixed to the main body portion 121 while inserted into an opening 122 formed in the wall portion 121a.

[0064] The cylindrical portion 125 has a first portion 126 and a second portion 127 formed integrally with the first portion 126. The first portion 126 is exposed to the outside of the main body portion 121, and its end portion 125b is located inside the main body portion 121. That is, the cylindrical portion 125 is connected to the main body portion 121 so as to protrude from the main body portion 121. The cylindrical portion 125 may be connected to the main body portion 121 using, for example, a screw (such as a grub screw). When viewed from the Z-axis direction, the outer diameter of the first portion 126 is larger than the inner diameter of the opening 122, and the outer diameter of the second portion 127 is smaller than the inner diameter of the opening 122. The first portion 126 is not inserted into the opening 122, while the second portion 127 is inserted into the opening 122.

[0065] The first part 126 includes an end 125a, which is one end of the cylindrical portion 125, and the second part 127 includes an end 125b, which is the other end of the cylindrical portion 125. A light-incident portion 129 is formed in the end 125a, into which light from an object is incident. That is, the package 120 has a light-incident portion 129. In this example, the light-incident portion 129 is an opening connected to the internal space of the cylindrical portion 125.

[0066] The inner surface 128 of the cylindrical portion 125 includes region 128a, region 128b, region 128c, region 128d, and region 128e. Regions 128a, 128b, 128c, 128d, and 128e are located in this order in the direction from end 125a to end 125b.

[0067] Region 128a is formed in a circular shape when viewed from the Z-axis direction. The inner diameter of region 128a is constant in the Z-axis direction. The first lens 51 is positioned inside region 128a. Region 128a is in contact with the side surface 51c of the first lens 51. Region 128a defines an aperture which is the light incident portion 129. That is, the first lens 51 is located in the light incident portion 129. Region 128b is formed in a tapered shape, with the inner diameter decreasing from the end 125a side to the end 125b side. Region 128c is formed in a circular shape when viewed from the Z-axis direction. The inner diameter of region 128c is constant in the Z-axis direction. The inner diameter of region 128c is smaller than the inner diameter of region 128a.

[0068] Region 128d is circular when viewed from the Z-axis direction. The inner diameter of region 128d is constant in the Z-axis direction. The inner diameter of region 128d is smaller than the inner diameter of region 128a and larger than the inner diameter of region 128c. The second lens 52 is located inside region 128d. Region 128d is in contact with the side surface 52c of the second lens 52. Region 128e is circular when viewed from the Z-axis direction. The inner diameter of region 128e is constant in the Z-axis direction. The inner diameter of region 128e is smaller than the inner diameter of region 128a and larger than the inner diameters of regions 128c and 128d. The photodetector 1 is located inside region 128e. Region 128e is in contact with the side surface of the housing 2.

[0069] The ring light 130 is attached to the package 120. In this example, the ring light 130 is attached to the first portion 126 of the cylindrical portion 125. The ring light 130 may be detachably attached to the first portion 126. The ring light 130 has a base 131 formed in an annular shape to surround the cylindrical portion 125, and a plurality of light sources 132 that emit light toward an object. The plurality of light sources 132 are arranged on the base 131 such that light is emitted from the surface 131a side of the base 131 opposite to the main body portion 121. The plurality of light sources 132 are located along the circumferential direction of the cylindrical portion 125. That is, the plurality of light sources 132 are arranged to surround the cylindrical portion 125 when viewed from the Z-axis direction. In this example, the plurality of light sources 132 are arranged at equal intervals from each other in the circumferential direction of the cylindrical portion 125. Each light source 132 may be an infrared lamp that emits light in the near-infrared to mid-infrared wavelength range.

[0070] Figure 10 schematically shows the path of light from the object M. In Figure 10, the path of some of the light L1 from the object M is schematically shown. In measurements using the spectroscopic module 100, with the surface 131a of the ring illumination 130 facing the object M, light is emitted from multiple light sources 132 toward the object M. The light emitted from the light sources 132 is scattered at the surface S1 of the object M and incident on the optical system 50. That is, the light from the object M includes scattered light generated at the surface S1 of the object M. The light from the object M passes through the optical system 50 (first lens 51 and second lens 52), the light transmitting member 13 and the bandpass filter 14 in this order and is incident on the Fabry-Perot interference filter 10. The light (light intensity) transmitted through the Fabry-Perot interference filter 10 is detected by the photodetector 8, and a spectral analysis is obtained based on the detection result.

[0071] Next, the configuration of the optical system 50 will be further explained with reference to Figures 10 and 11. The optical system 50 is designed to satisfy predetermined conditions. Specifically, when the distance D1 from the first lens 51 to the object M is 5 cm, and a circular area on the surface S1 of the object M with a diameter D2 of 1 cm is defined as the field of view region A, the optical system 50 is configured such that, of the light incident on the first lens 51 from the field of view region A, light with a divergence angle greater than 1 degree is not incident on the light transmission region 10a of the Fabry-Perot interference filter 10, while light with a divergence angle of 1 degree or less is incident on the light transmission region 10a. In other words, the optical system 50 is configured to cut out (prevent from incident on the light transmission region 10a) light with a divergence angle greater than 1 degree from the light incident on the first lens 51 from the field of view region A. The diameter D2 (1 cm) of the field of view region A is larger than the width W4 (approximately 0.75 mm in this example) of the light transmission region 10a of the Fabry-Perot interference filter 10.

[0072] The distance D1 from the first lens 51 to the object M is the shortest distance between the first lens 51 and the object M. In this example, distance D1 is the distance from the vertex of surface 51a to surface S1 of object M. Field of view region A is a region virtually set on surface S1 of object M. Field of view region A is a circular region with a diameter D2 of 1 cm, and in this example extends perpendicular to the Z-axis direction. When viewed from the Z-axis direction, the center of field of view region A coincides with the center of the first lens 51.

[0073] Figure 11 is a schematic diagram showing the divergence angle of light from an object M. As described above, the light from object M includes scattered light generated at the surface S1 of object M. The scattered light is emitted so as to spread radially from the surface S1. Figure 11 shows the light L1 and light L2 contained in the scattered light from point P. Light L1 is light with a divergence angle θ3 greater than 1 degree, and light L2 is light with a divergence angle θ4 less than or equal to a predetermined angle of 1 degree or less. In this example, the predetermined angle is 0.3 degrees. The divergence angle is the angle that indicates how much light spreads as it travels, and is expressed as an angle from the central axis of the light. Specifically, light L1 and L2 are light that travels along the side surface of a hypothetical cone with point P as its vertex, and the angle between the central axis of the cone and the side surface corresponds to the divergence angle.

[0074] As described above, the optical system 50 is configured to allow light L2 having a divergence angle θ4 of 1 degree or less to enter the light transmission region 10a, while preventing light L1 having a divergence angle θ3 greater than 1 degree from entering the light transmission region 10a. In this example, the optical system 50 is configured to prevent light having a divergence angle greater than the predetermined angle but less than 1 degree from entering the light transmission region 10a. That is, the optical system 50 is configured to allow light having a divergence angle of 0.3 degrees or less to enter the light transmission region 10a, while preventing light having a divergence angle greater than the predetermined angle (0.3 degrees) from entering the light transmission region 10a.

[0075] In addition to the scattered light described above, the light from object M also contains specularly reflected light. The specularly reflected light from object M is the light emitted from the light source 132 that has been specularly reflected from the surface S1 of object M. In the optical system 50, which is designed to satisfy the predetermined conditions regarding the divergence angle described above, specularly reflected light with a reflection angle greater than 1 degree from the light field region A that enters the first lens 51 does not enter the light transmission region 10a. Furthermore, the optical system 50 is designed so that light with a divergence angle greater than a predetermined angle (0.3 degrees) from the light field region A that enters the first lens 51 does not enter the light transmission region 10a. Therefore, in the optical system 50, specularly reflected light with a reflection angle greater than a predetermined angle (0.3 degrees) also does not enter the light transmission region 10a. For the same reason, among the ambient light that enters the first lens 51, ambient light with an angle greater than 1 degree with respect to the Z-axis direction does not enter the light transmission region 10a. Furthermore, in the optical system 50, among the ambient light incident on the first lens 51, light having an angle greater than a predetermined angle (0.3 degrees) with respect to the Z-axis direction does not enter the light transmission region 10a. [Mechanism of Action and Effects]

[0076] In the spectroscopic unit 110, when the distance D1 from the first lens 51 to the object M is 5 cm, and a circular area on the surface S1 of the object M with a diameter D2 of 1 cm is defined as the field of view A, the optical system 50 is configured to allow light with a divergence angle of 1 degree or less to enter the light transmission region 10a of the Fabry-Perot interference filter 10, while preventing light with a divergence angle greater than 1 degree from entering the light transmission region 10a of the Fabry-Perot interference filter 10. Generally, since the light source 132 is positioned at a distance from the optical axis of the light directed toward the Fabry-Perot interference filter 10, noise light such as specular reflection from the surface S1 of the object M has an angle of 1 degree or more. Therefore, with the spectroscopic unit 110, such noise light does not enter the photodetector 8 through the light transmission region 10a of the Fabry-Perot interference filter 10. As a result, a decrease in measurement accuracy caused by noise light can be suppressed. In particular, if the surface S1 of the object M has irregularities, the direction of specularly reflected light from the surface S1 of the object M will vary, causing the signal detected by the spectroscopic module to change significantly depending on the measurement position on the object M. Since specularly reflected light does not contain information about the physical properties of the object M, it is preferable that it not be detected. The spectroscopic unit 110 suppresses the incidence of such specularly reflected light into the light transmission region 10a of the Fabry-Perot interference filter 10, thereby enabling highly accurate measurements. Furthermore, the spectroscopic unit 110 also suppresses the incidence of ambient light having an angle greater than 1 degree with respect to the Z-axis direction into the light transmission region 10a via the optical system 50, thus enabling highly accurate measurements. In addition, the field of view A is a circular region with a diameter of 1 cm, which is sufficiently larger than the width W4 (approximately 0.75 mm) of the light transmission region 10a of the Fabry-Perot interference filter 10, and light with a divergence angle of 1 degree or less is incident on the light transmission region 10a from the field of view A. In other words, light can be guided from a wide area on the surface S1 of the object M to the light-transmitting region 10a, and the amount of light detected by the photodetector 8 can be increased. Therefore, with the spectroscopic unit 110, measurements can be performed with high accuracy.

[0077] Figure 12 is a graph showing the results of measurements using the spectroscopic module 100. In this measurement, the light absorption of the object (instant coffee beans) was measured at each wavelength. Specifically, the object was placed on a turntable, and light was emitted from the light source 132 of the ring illumination 130 towards the object while the turntable was rotating. The distance D1 from the object to the first lens 51 was 5 cm. While changing the voltage applied to the Fabry-Perot interference filter 10 (the transmission wavelength of the Fabry-Perot interference filter 10), the light from the object was detected by the photodetector element 8, and the light absorption of the object was measured at each wavelength. Figure 12 shows the results of the second derivative of the light absorption of the object. Multiple measurements were performed, and Figure 12 shows the results of each measurement. As shown in Figure 12, the multiple measurement results were in close agreement and showed similar trends. That is, the variation between multiple measurement results was kept small, and it was confirmed that the spectroscopic module 100 can perform measurements with high accuracy regardless of the measurement position on the object.

[0078] When viewed from the Z-axis direction, the outer edge 51d of the first lens 51 is larger than the outer edge 10b of the Fabry-Perot interference filter 10. This allows the optical system 50 to guide light from a wider area on the surface S1 of the object M to the light-transmitting region 10a of the Fabry-Perot interference filter 10 via the first lens 51, thereby increasing the amount of light detected by the photodetector 8. Furthermore, by guiding light from a wider area to the light-transmitting region 10a of the Fabry-Perot interference filter 10, the light signals detected by the photodetector 8 are averaged, suppressing variations in measurement results caused by the measurement position on the surface S1 of the object M.

[0079] The photodetector element 8 is a single-channel element. This ensures that the spectral spectrum of scattered light emitted from the object M can be reliably obtained. In other words, in a multi-channel photodetector element that outputs signals from multiple pixels, for example, the amount of signal light can vary greatly depending on the shape of the surface of the object corresponding to that pixel (even if a large field of view is secured, each pixel only corresponds to a portion of the area). In contrast, in the present invention, light incident on the photodetector element 8 from a relatively large field of view A via the Fabry-Perot interference filter 10 is output as a single signal. Therefore, the signal from the entire field of view A is averaged, reducing the signal variation depending on the position and allowing a stable signal to be obtained.

[0080] The first mirror section 35 and the second mirror section 36 face each other in the Z-axis direction. The optical system 50 has a second lens 52 located between the first lens 51 and the Fabry-Perot interference filter 10. The second lens 52 is configured such that the angle θ1 of light transmitted through the second lens 52 with respect to the Z-axis direction is smaller than the angle θ2 of light incident on the second lens 52 with respect to the Z-axis direction. The transmitted wavelength of the Fabry-Perot interference filter 10 changes depending on the angle of incidence of the light (it is dependent on the angle of incidence). With the spectroscopic unit 110 having the second lens 52, the angle of light incident on the Fabry-Perot interference filter 10 can be made nearly parallel to the opposing direction (Z-axis direction) of the first mirror section 35 and the second mirror section 36, and light of a desired wavelength can be transmitted with good resolution. Furthermore, even when a large focusing lens (for example, the first lens 51) is placed close to the Fabry-Perot interference filter 10, good resolution can be obtained by using the second lens 52, thus enabling a more compact spectroscopic module 100 to which the spectroscopic unit 110 is applied.

[0081] The second lens 52 is formed separately from the first lens 51. This improves the degree of freedom in the arrangement and design of the first lens 51 and the second lens 52.

[0082] The spectroscopic unit 110 includes a bandpass filter 14 positioned between the first lens 51 and the Fabry-Perot interference filter 10. This allows unwanted wavelengths of light to be filtered out by the bandpass filter 14, and only the desired wavelengths of light to be incident on the Fabry-Perot interference filter 10. As a result, measurements can be performed with higher accuracy.

[0083] When viewed from the Z-axis direction, the width W1 of the first lens 51 is at least twice (10 times in this example) the width W4 of the light transmission region 10a of the Fabry-Perot interference filter 10. This allows the optical system 50 to guide light from a wider area on the surface S1 of the object M to the light transmission region 10a of the Fabry-Perot interference filter 10 via the first lens 51, thereby increasing the amount of light detected by the photodetector 8.

[0084] The spectroscopic module 100 comprises a spectroscopic unit 110 and a package 120 that houses the spectroscopic unit 110. The package 120 has a light incident section 129 into which light from the object M is incident. The first lens 51 is located in the light incident section 129. This allows the spectroscopic unit 110 to be protected by the package 120. Furthermore, in the spectroscopic module 100 enclosed in package 120, light can be incident into the package 120 via the first lens 51 located in the light incident section 129.

[0085] The package 120 has a cylindrical portion 125. The first lens 51 is positioned inside the cylindrical portion 125. When viewed from the direction of extension of the cylindrical portion 125, the light transmission region 10a of the Fabry-Perot interference filter 10 is located inside the cylindrical portion 125. This allows the light focused by the first lens 51 to be efficiently incident on the light transmission region 10a of the Fabry-Perot interference filter 10.

[0086] The package 120 has a main body 121 that houses the Fabry-Perot interference filter 10. The cylindrical portion 125 is connected to the main body 121 so as to protrude from it. The light incident portion 129 is formed at the end of the cylindrical portion 125 that protrudes from the main body 121. This allows for a space between the first lens 51 and the Fabry-Perot interference filter 10 to be provided within the cylindrical portion 125, making the main body 121 more compact. Furthermore, when using the spectroscopic module 100, the light incident portion 129 (first lens 51) can be brought close to the object M while holding the main body 121.

[0087] The spectroscopic module 100 is equipped with multiple light sources 132 that emit light onto the object M. The multiple light sources 132 are positioned along the circumferential direction of the cylindrical portion 125. This allows the object M to be uniformly illuminated with light from the multiple light sources 132, enabling measurements with higher accuracy. For example, if there is only one light source 132, and the surface S1 of the object M has irregularities, shadows may be cast on the surface S1, potentially causing variations in the amount of light (scattered light (signal light)) from the object M. In contrast, in the spectroscopic module 100, because the multiple light sources 132 are positioned along the circumferential direction of the cylindrical portion 125, light is irradiated onto the object M from multiple directions, thus stabilizing the amount of light from the object M. [Differentiation]

[0088] The present invention is not limited to the embodiments described above. For example, as shown in Figure 13, the optical system 50 may have a plurality of second lenses 52 (second lenses 52A, 52B). In the example shown in Figure 13, the second lenses 52A and 52B have the same configuration as the second lens 52 described above. The second lenses 52A and 52B are arranged side by side in the Z-axis direction. The second lens 52A is positioned between the first lens 51 and the second lens 52B. Light from the object M is focused by the first lens 51, then passes through the second lens 52A and 52B in that order, and enters the Fabry-Perot interference filter 10.

[0089] According to the modified example shown in Figure 13, the angle of light incident on the Fabry-Perot interference filter 10 can be made closer to parallel with the opposing direction (Z-axis direction) of the first mirror section 35 and the second mirror section 36 (improving collimation), allowing light of a desired wavelength to be transmitted in the Fabry-Perot interference filter 10 with even better resolution.

[0090] As another variation, as shown in Figure 14, the optical system 50 may have a plurality of first lenses 51 (first lenses 51A, 51B) and a plurality of second lenses 52 (second lenses 52A, 52B). In the example shown in Figure 14, the first lenses 51A and 51B have the same configuration as the first lens 51 described above. The second lenses 52A and 52B have the same configuration as the second lens 52 described above.

[0091] The first lens 51A and the first lens 51B are arranged side by side in the Z-axis direction. The second lens 52A and the second lens 52B are also arranged side by side in the Z-axis direction. The first lens 51A, the first lens 51B, the second lens 52A, and the second lens 52B are arranged in this order from the object M side in the Z-axis direction. That is, of the first lens 51A, the first lens 51B, the second lens 52A, and the second lens 52B, the first lens 51A is the lens closest to the object M. Light from the object M passes through the first lens 51A, the first lens 51B, the second lens 52A, and the second lens 52B in this order and enters the Fabry-Perot interference filter 10.

[0092] In the modified example shown in Figure 14, the optical system 50 has multiple first lenses 51 (condensing lenses), which improves the light-gathering performance of the optical system 50 and shortens the length (distance) of the optical system 50. In the modified example shown in Figure 14, the optical system 50 may have only one second lens 52.

[0093] In another variation, as shown in Figure 15, the second lens 52 may be formed integrally with the first lens 51. In the example shown in Figure 15, the optical system 50 has a first lens 51, a second lens 52, and a connecting portion 53 that connects the first lens 51 and the second lens 52. The first lens 51, the second lens 52, and the connecting portion 53 are formed integrally with each other. The first lens 51, the second lens 52, and the connecting portion 53 together constitute a lens 55. That is, the lens 55 has a portion corresponding to the first lens 51, a portion corresponding to the second lens 52, and a portion corresponding to the connecting portion 53.

[0094] The first lens 51 (the portion of lens 55 corresponding to the first lens 51) includes a surface 51a, which is a curved surface projecting outward in the Z-axis direction of the first lens 51 (lens 55). The portion of the first lens 51 opposite to surface 51a is connected to a connecting portion 53. The second lens 52 (the portion of lens 55 corresponding to the second lens 52) includes a surface 52b, which is a curved surface recessing inward in the Z-axis direction of the second lens 52 (lens 55). The portion of the second lens 52 opposite to surface 52b is connected to a connecting portion 53. The connecting portion 53 is cylindrical in shape. One end of the connecting portion 53 is connected to the first lens 51, and the other end of the connecting portion 53 is connected to the second lens 52. The first lens 51, the second lens 52, and the connecting portion 53 are continuous with each other without any breaks. According to the modified example shown in Figure 15, the second lens 52 is formed integrally with the first lens 51. This allows the spectroscopic unit 110 to be realized with a simple configuration that requires fewer parts.

[0095] When viewed from the Z-axis direction, the outer edge 51d of the first lens 51 may be smaller than the outer edge 10b of the Fabry-Perot interference filter 10. When viewed from the Z-axis direction, the outer edge 52d of the second lens 52 may be smaller than the outer edge 10b of the Fabry-Perot interference filter 10. The shapes of the first lens 51 and the second lens 52 are not limited. For example, the first lens 51 and the second lens 52 may each have an elliptical or rectangular shape when viewed from the Z-axis direction.

[0096] The photodetector element 8 may be a multi-channel element. A multi-channel element is an element that has multiple light-receiving regions (multiple photoelectric conversion regions) and outputs multiple electrical signals obtained from the multiple light-receiving regions without summing them up as a single electrical signal. If the photodetector element 8 is a multi-channel element, the multiple electrical signals output from the photodetector element 8 (current values ​​obtained from the multiple light-receiving regions) may be summed up by another device (e.g., a computer) connected to the photodetector element 8. The photodetector device 1 may have multiple photodetector elements 8 (photodetectors).

[0097] The optical system 50 does not have to have a second lens 52. The optical system 50 may have three or more first lenses 51, or three or more second lenses 52. The spectroscopic unit 110 does not have to have a bandpass filter 14.

[0098] When viewed from the Z-axis direction, the width W1 of the first lens 51 may be less than 10 times the width W4 of the light transmission region 10a of the Fabry-Perot interference filter 10.

[0099] The cylindrical portion 125 may be integrally connected to the main body portion 121. That is, the cylindrical portion 125 may be formed as a single component together with the main body portion 121, rather than as a separate part from the main body portion 121. The package 120 does not have to have the cylindrical portion 125. In this case, the optical system 50 (first lens 51 and second lens 52) may be housed in the main body portion 121.

[0100] The arrangement of the multiple light sources 132 is not limited. The multiple light sources 132 do not have to be arranged along the circumferential direction of the cylindrical portion 125. The spectral module 100 may have only one light source 132.

[0101] In measurements using the spectroscopic module 100, the spectroscopic module 100 can be positioned at any position relative to the object M. That is, the distance D1 from the first lens 51 to the object M may be greater than or less than 5 cm. The distance D1 may be in the range of a few millimeters to several tens of centimeters.

[0102] In the above embodiment, the example described was a case where the light source 132 and the spectroscopic module 100 are positioned on the same side with respect to the surface S1 of the object M, and the spectroscopic module 100 is applied to a measurement (reflection measurement) in which the light emitted so as to be reflected from the object M is detected by the spectroscopic unit 110. However, the spectroscopic module 100 may also be applied to a transmission measurement. The transmission measurement will be described with reference to Figure 16. As shown in Figure 16, when the spectroscopic module 100 is applied to a transmission measurement, the spectroscopic unit 110 may be positioned on the opposite side of the object M from the light source 132. In this example, the object M is held by a sample holder H. In this example, the spectroscopic module 100 includes an optical fiber 81 and a collimating lens 82. Light emitted from the light source 132 enters the collimating lens 82 via the optical fiber 81. The light that enters the collimating lens 82 is collimated by the collimating lens 82 and then enters the object M. The light that enters the object M is transmitted through the object M. Light from the object M (light transmitted through the object M) enters the optical system 50 of the spectroscopic unit 110 and is detected by the photodetector 8. The light from the object M includes scattered light from the object M.

[0103] The spectroscopic module 100 may be mounted on the photodetector 200 shown in Figure 17. The photodetector 200 comprises a plurality of spectroscopic modules 100, a holder 210, and a light source unit 220. In this example, the photodetector 200 comprises four spectroscopic modules 100. In this example, when viewed from a predetermined direction B2, the four spectroscopic modules 100 are arranged on the vertices of a virtual rectangle surrounding the light source unit 220. The number and arrangement of the spectroscopic modules 100 are not limited. The spectroscopic module 100 according to this modified example differs from the spectroscopic module 100 according to the above-described embodiment in that it does not include a ring illumination 130.

[0104] The holder 210 is a component that holds the spectroscopic module 100. The holder 210 has a surface 210a and a surface 210b. Surface 210b is located on the opposite side of surface 210a in direction B2. The holder 210 has a recess 211 formed therein that opens on surface 210a (receding from surface 210a to surface 210b). The recess 211 has a bottom surface 211a and a side surface 211b. The bottom surface 211a extends perpendicular to direction B2. The side surface 211b is the surface that connects surface 210a and bottom surface 211a. When viewed from direction B2, the side surface 211b extends so as to surround the light source unit 220. The side surface 211b is inclined with respect to direction B2. The inner surface of the recess 211 (bottom surface 211a and side surface 211b) is a mirror surface with high light reflectivity and functions as a reflector that reflects light.

[0105] The holder 210 has a plurality of through holes 212 into which each spectroscopic module 100 is inserted. One end of each through hole 212 is open on the side surface 211b. The cylindrical portion 125 of each spectroscopic module 100 is inserted into the corresponding through hole 212. Specifically, the cylindrical portion 125 is positioned inside the through hole 212 such that the end portion 125a (light incident portion 129) of the cylindrical portion 125 is exposed from the opening of the through hole 212 on the side surface 211b.

[0106] In this example, the light source unit 220 is provided as a separate configuration from the spectral module 100. The light source unit 220 is not directly attached to the spectral module 100. The light source unit 220 has a base 221 and a plurality of light sources 222 that emit light toward an object. The holder 210 has a recess 213 in which the base 221 is placed and a plurality of through holes 214 in which the plurality of light sources 222 are placed. The recess 213 opens toward the surface 210b (it is recessed toward the surface 210a from the surface 210b). The through holes 214 open toward the bottom surface of the recess 213 and the bottom surface 211a of the recess 211. Each light source 222 is positioned inside the through holes 214 so as to be exposed from the opening of the through hole 214 toward the bottom surface 211a.

[0107] In measurements using the photodetector 200, with the surface 210a of the holder 210 (the bottom surface 211a and side surface 211b, which are the inner surfaces of the recesses 211) facing the object M, light L10 is emitted from multiple light sources 222 towards the object M. The light L10 emitted from the light sources 222 is scattered on the surface S1 of the object M and incident on the optical system 50 of the spectroscopic module 100. The light L10 from the object M is incident on the light incident section 129 exposed through the opening of the through hole 212 on the side surface 211b. The light L10 incident on the light incident section 129 passes through the optical system 50 (first lens 51 and second lens 52), the light transmitting member 13, and the bandpass filter 14 in that order and is incident on the Fabry-Perot interference filter 10. The light (light intensity) transmitted through the Fabry-Perot interference filter 10 is detected by the photodetector 8, and a spectral analysis is obtained based on the detection result. This modified version also suppresses the incidence of specularly reflected light from the surface S1 of the object M, as well as noise light such as ambient light, into the light transmission region 10a, enabling highly accurate measurements.

[0108] The photodetector 200 may include a control board 230 and a plurality of wirings 240 arranged on the surface 210b of the holder 210, as shown in Figure 18. The control board 230 is connected to a plurality of spectroscopic modules 100. Specifically, the control board 230 is electrically connected to the Fabry-Perot interference filter 10 of the photodetector 1 provided in the spectroscopic module 100 via the wirings 240. The control board 230 controls the input and output of electrical signals to the Fabry-Perot interference filter 10. The control board 230 may be used in place of the control boards 61 and 62 in the above-described embodiment (as a control board common to the plurality of spectroscopic modules 100). In this case, the control boards 61 and 62 of each spectroscopic module 100 may be omitted. The photodetector 200 may include a flexible substrate instead of the wirings 240. [Explanation of symbols]

[0109] 8...Photodetector element, 10...Fabry-Perot interference filter, 10a...Light transmission region, 10b, 51d...Outer edge, 14...Bandpass filter, S1...Surface, 50...Optical system, 51...First lens, 52...Second lens, 100...Spectroscopic module, 110...Spectroscopic unit, 120...Package, 121...Main body, 125...Tube, 125a...End, 129...Light incident part, 132...Light source, A...Field of view, M...Object.

Claims

1. A Fabry-Perot interference filter having a pair of mirrors whose distance from each other is variable, An optical system having a first lens that focuses light from an object onto the Fabry-Perot interference filter, The system comprises a photodetector that detects the light transmitted through the Fabry-Perot interference filter, When the distance from the first lens to the object is 5 cm, and the field of view is defined as a circular area on the surface of the object with a diameter of 1 cm, the optical system is configured such that, of the light incident on the first lens from the field of view, light with a divergence angle greater than 1 degree is not incident on the light transmission area of ​​the Fabry-Perot interference filter, while light with a divergence angle of 1 degree or less is incident on the light transmission area. Spectroscopic unit.

2. The pair of mirror portions face each other in a predetermined direction, When viewed from the predetermined direction, the outer edge of the first lens is larger than the outer edge of the Fabry-Perot interference filter. The spectroscopic unit according to claim 1.

3. The aforementioned photodetector is a single-channel element. The spectroscopic unit according to claim 1 or 2.

4. The pair of mirror portions face each other in a predetermined direction, The optical system has a second lens located between the first lens and the Fabry-Perot interference filter. The second lens is configured such that the angle of light transmitted through the second lens with respect to the predetermined direction is smaller than the angle of light incident on the second lens with respect to the predetermined direction. The spectroscopic unit according to claim 1 or 2.

5. The second lens is formed separately from the first lens. The spectroscopic unit according to claim 4.

6. The second lens is formed integrally with the first lens. The spectroscopic unit according to claim 4.

7. The system further comprises a bandpass filter located between the first lens and the Fabry-Perot interference filter. The spectroscopic unit according to claim 1 or 2.

8. The pair of mirror portions face each other in a predetermined direction, When viewed from the predetermined direction, the width of the first lens is at least twice the width of the light transmission region. The spectroscopic unit according to claim 1 or 2.

9. The pair of mirror portions face each other in a predetermined direction, When viewed from the predetermined direction, the width of the first lens is 10 times or more the width of the light transmission region. The spectroscopic unit according to claim 1 or 2.

10. A spectral unit according to claim 1 or 2, The package comprises the aforementioned spectroscopic unit, The package has a light incident portion into which the light from the object is incident, The first lens is located at the light incident portion, Spectroscopic module.

11. The package has a cylindrical portion, The first lens is positioned inside the cylindrical portion, When viewed from the direction of extension of the cylindrical portion, the light-transmitting region is located inside the cylindrical portion. The spectroscopic module according to claim 10.

12. The package further comprises a main body that houses the Fabry-Perot interference filter, The cylindrical portion is connected to the main body so as to protrude from the main body, The light incident portion is formed at the end of the cylindrical portion that protrudes from the main body portion. The spectroscopic module according to claim 11.

13. The system further comprises multiple light sources that emit light toward the aforementioned object, The aforementioned multiple light sources are positioned along the circumferential direction of the cylindrical portion. The spectroscopic module according to claim 11.

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