Optical filter, spectroscopic sensor, and method for manufacturing optical filter

Abstract

To provide a small size and easy-to-manufacture optical filter capable of outputting light with multiple desired wavelengths.SOLUTION: The optical filter includes: a substrate having a first surface and a second surface, which transmits light; a first area as a predetermined area on the first surface; a second area that is an area different from the first area on the first surface, and which is an area closer to the second surface than the first area; a first optical thin film that is formed over the first surface including the first area and the second area; and a second optical thin film placed facing the first surface with a predetermined distance apart from the first surface.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to an optical filter, a spectroscopic sensor, and a method for manufacturing an optical filter. [Background technology]

[0002] A Fabry-Perot interference type optical filter is known that outputs light of a predetermined wavelength when light of a wide wavelength band is input. Patent Document 1 discloses an optical filter including a first substrate having a plurality of step portions each having a different height, a second substrate bonded opposite to the first substrate and having a movable step portion formed of steps, a first mirror pair and a second mirror pair provided at each step portion via gaps of different sizes, a pair of electrode pairs provided around the mirror pairs, and a diaphragm portion formed on the first substrate. When light including various continuous wavelengths such as white light is input, the optical filter disclosed in Patent Document 1 outputs light of a wavelength corresponding to the gap of the first mirror pair and light of a wavelength corresponding to the gap of the second mirror pair. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-204457 A Summary of the Invention [Problem to be solved by the invention]

[0004] The optical filter disclosed in Patent Document 1 is manufactured by forming a gap in each of the first and second substrates and bonding these two substrates, but the smaller the optical filter, the more difficult it is to maintain a predetermined gap between the first and second mirror pairs. Similarly, it is also difficult to ensure the misalignment and parallelism between the mirrors. In other words, the technology disclosed in Patent Document 1 makes it difficult to manufacture a small optical filter.

[0005] An object of the present disclosure is to provide an optical filter that is small and easy to manufacture, and is capable of outputting light of a plurality of desired wavelengths, a spectroscopic sensor including an optical filter, and a method for manufacturing an optical filter. [Means for solving the problem]

[0006] An optical filter of one embodiment of the present disclosure comprises a substrate that transmits light and has a first surface and a second surface, a first region that is a predetermined area on the first surface, a second region that is a different area on the first surface from the first region and is closer to the second surface than the first region, a first optical thin film formed on the first surface including the first region and the second region, and a second optical thin film positioned opposite the first surface and spaced a predetermined distance from the first surface.

[0007] An optical filter according to one embodiment of the present disclosure comprises a substrate that transmits light and has a first surface and a second surface, a first optical thin film formed in a first region, which is a predetermined region on the first surface, a second optical thin film arranged opposite the first optical thin film and a predetermined distance away from the first surface, a third optical thin film formed in a second region, which is a region on the first surface different from the first region, and a fourth optical thin film arranged opposite the third optical thin film and the predetermined distance away from the first surface, wherein at least one of the first optical thin film and the second optical thin film has different optical properties than at least one of the third optical thin film and the fourth optical thin film.

[0008] A spectroscopic sensor according to an aspect of the present disclosure includes an optical filter according to an aspect of the present disclosure, a light source that outputs light toward the optical filter, and a light receiving element that receives light that has passed through the optical filter.

[0009] A method for manufacturing an optical filter according to one embodiment of the present disclosure includes forming a recess in at least one of a first region and a second region of a substrate that transmits light, forming a first optical thin film on a surface of the substrate on which the recess is formed, making an outer edge of the first region and an outer edge of the second region in the first optical thin film conductive, forming a support in a region different from the first region, the second region and the conductive region, forming a second optical thin film supported by the support and facing the first optical thin film, and making a region of the second optical thin film facing the outer edge of the first region and a region facing the outer edge of the second region conductive. Effect of the Invention

[0010] According to the present disclosure, it is possible to provide an optical filter that is small and easy to manufacture, and is capable of outputting light of a plurality of desired wavelengths, a spectroscopic sensor including an optical filter, and a method for manufacturing an optical filter. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram for explaining a Fabry-Perot interference type optical filter. [Diagram 2] FIG. 1 is a diagram for explaining the wavelength tunable range of the wavelength output from an optical filter. [Diagram 3] FIG. 1 is a schematic diagram showing a first configuration example of an optical filter according to an embodiment of the present invention; [Figure 4] FIG. 2 is a schematic diagram showing a second configuration example of the optical filter according to the embodiment; [Diagram 5] FIG. 13 is a schematic diagram showing a third configuration example of the optical filter according to the embodiment; [Figure 6] FIG. 1 is a block diagram showing a configuration example of a spectroscopic sensor including an optical filter according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters and duplicated description of substantially the same configuration may be omitted. This is to avoid the following description becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0013] (Present embodiment) Fig. 1 is a diagram for explaining a Fabry-Perot interference type optical filter, and Fig. 2 is a diagram for explaining a wavelength tunable range of the wavelength output from the optical filter.

[0014] The optical filter 10 includes a substrate 20, an optical thin film 30A, an optical thin film 30B, and a support 40.

[0015] The substrate 20 has the shape of a flat plate made of a light-transmitting material, and has a first surface 21 and a second surface 22 opposite to the first surface 21.

[0016] For convenience of explanation, as shown in FIG. 1, the axis perpendicular to the first surface 21 of the substrate 20 and extending in the height direction is defined as the Z axis. The axis perpendicular to the Z axis and extending from left to right on the paper is defined as the X axis. The axis perpendicular to the X axis and the Z axis, that is, the axis extending from the front to the back of the paper, is defined as the Y axis. For convenience of explanation, the positive direction of the Z axis may be referred to as "up", the negative direction of the Z axis as "down", the negative direction of the X axis as "left", the positive direction of the X axis as "right", the positive direction of the Y axis as "front", and the negative direction of the Y axis as "rear". These expressions relating to directions are used for convenience of explanation and are not intended to limit the position of the structure when actually used. The same applies to other drawings.

[0017] The optical thin film 30A is formed (eg, by vapor deposition) on the first surface 21 of the substrate 20. The optical thin film 30A is a multi-layer film in which materials with high refractive index and materials with low refractive index are alternately laminated.

[0018] The optical thin film 30B is disposed opposite the optical thin film 30A. The optical thin film 30B is a multi-layer film in which high refractive index materials and low refractive index materials are alternately laminated, and has a structure symmetrical to the optical thin film 30A with an air layer sandwiched therebetween.

[0019] One example of a material with a high refractive index is titanium oxide (TiO 2 ) or silicon (Si). The refractive index of titanium oxide film is about 2.5, and the refractive index of silicon is about 3.6. An example of a material with a low refractive index is silicon oxide film (SiO 2 ) or silicon nitride film (SiN). The refractive index of a silicon oxide film is about 1.5, and the refractive index of a silicon nitride film is about 2.1. However, the above materials and refractive indexes are only examples, and the optical thin films 30A and 30B can be made of various materials.

[0020] As shown in FIG. 1(a), a region 50A, which is a predetermined region in the optical thin film 30A, and a region 50B, which is a region facing the region 50A in the optical thin film 30B, are separated by a predetermined distance d 1 A space (for example, an air layer) is formed between region 50A and region 50B.

[0021] The support 40 is disposed between a region of the optical thin film 30A different from the region 50A and the electrode portion 60A and a region of the optical thin film 30B different from the region 50B and the electrode portion 60B, and supports the optical thin film 30B. For example, the support 40 extends upward from a region of the optical thin film 30A different from the region 50A and the electrode portion 60A, and supports the optical thin film 30B. The support 40 may be made of a material that transmits light, or may be made of a material that blocks light.

[0022] When light in a wide wavelength band (hereinafter referred to as white light) is input toward the region 50B of the optical thin film 30B, the distance d 1 The wavelength λ corresponding to 1is output from the region 50A of the optical thin film 30A. Hereinafter, the set of the region 50B of the optical thin film 30B and the region 50A of the optical thin film 30A may be referred to as a thin film pair 50. The wavelength of the light output after passing through the thin film pair 50 may be referred to as a transmitted wavelength. For example, in the case of a tungsten light source, the wavelength band of the white light is from 300 nm to 3000 nm. However, the wavelength band of the white light is not limited to this range and may be wider or narrower than this range since it varies depending on the illumination light source used.

[0023] As shown in FIG. 1B, the region 50B of the optical thin film 30B is bent in a direction toward the region 50A of the optical thin film 30A, and the distance between the thin film pair 50 is reduced by d 2 ( <d 1 ) and when white light is input toward the region 50B of the optical thin film 30B, the distance d 2 The wavelength λ corresponding to 2 (<λ 1 ) of light is output from the thin film pair 50.

[0024] In this manner, the Fabry-Perot interference type optical filter 10 has a distance between the thin film pair 50 of d 1 From d 2 By changing between λ 1 From λ 2 It is possible to selectively output light of any wavelength between these.

[0025] The following method can be used to bend the region 50B of the optical thin film 30B in a direction approaching the region 50A of the optical thin film 30A. That is, electrode sections 60A, 60B are provided at predetermined positions on the optical thin films 30B and 30A facing each other, and a voltage is applied to each electrode to generate an electrostatic attraction force, thereby bending the region 50B of the optical thin film 30B in a direction approaching the region 50A of the optical thin film 30A. However, since there is a limit to the strength of the structure, there is also a limit to the amount by which the optical thin film 30B can be bent. That is, the optical thin film 30B can be bent to a size λ shown in FIG. 2(a). 1 and λ 2 There are limitations to the methods for expanding the wavelength tuning range between

[0026] Therefore, in this embodiment, a plurality of thin film pairs are formed in the optical filter 10 so that different transmission wavelengths are output from each other. This allows light of any transmission wavelength in a wider range to be output, compared to the case where the transmission wavelength is changed only by the bending of the optical thin film 30B. For example, 1 From λ 2 , λ 2 From λ 3 , λ 3 From λ 4 (where λ 1 <λ 2 <λ 3 <λ 4 By forming multiple thin film pairs so that the transmitted wavelength of λ 2 is output, the wavelength tunable range is expanded to λ 2 (see Fig. 2(b)). 1 From λ 4 A specific configuration example of such an optical filter 10 will be described below.

[0027] <First configuration example> FIG. 3 is a schematic diagram showing a first configuration example of the optical filter 10 according to the present embodiment.

[0028] The optical filter 10 includes a substrate 20, an optical thin film 30A, an optical thin film 30B, and a support 40.

[0029] The substrate 20 is made of a light-transmitting material and has a first surface 21 and a second surface 22 opposite to the first surface 21. The first surface 21 of the substrate 20 includes, for example, a region 51A, a region 52A, a region 53A, an electrode portion 61A, an electrode portion 62A, and an electrode portion 63A. The region 51A, the region 52A, the region 53A, the electrode portion 61A, the electrode portion 62A, and the electrode portion 63A are different regions on the first surface 21.

[0030] Region 52A is closer to second surface 22 than region 53A. That is, in first surface 21, a recess is formed in the direction approaching second surface 22 in region 52A.

[0031] Region 51A is closer to second surface 22 than region 52A. That is, in region 51A of first surface 21, a carve is formed in the direction approaching second surface 22 that is deeper than the carve in region 52A.

[0032] The region 53A is not recessed as shown in Fig. 3. However, the region 53A may be recessed in a shallower manner than the region 52A.

[0033] The recesses of the regions 52A and 51A are formed by etching the first surface 21 of the substrate 20. This makes it possible to easily form the recesses of the regions 52A and 51A at the same time.

[0034] The optical thin film 30A is formed with a predetermined film thickness on the first surface 21 including the regions 51A, 52A, and 53A. For example, the optical thin film 30A is formed on the first surface 21 by a deposition process. This allows the optical thin film 30A having steps to be easily formed on the first surface 21 all at once.

[0035] The support 40 extends upward from a region of the first surface 21 different from the regions 51A, 52A, 53A, electrode portion 61A, electrode portion 62A, and electrode portion 63A, and supports the optical thin film 30B.

[0036] The optical thin film 30B is disposed opposite to the optical thin film 30A. The optical thin film 30B is supported by a support 40.

[0037] The optical thin film 30B has a region 51B facing the region 51A of the optical thin film 30A, a region 52B facing the region 52A of the optical thin film 30A, and a region 53B facing the region 53A of the optical thin film 30A.

[0038] Hereinafter, a set of region 51A of optical thin film 30A and region 51B of optical thin film 30B may be referred to as thin film pair 51. A set of region 52A of optical thin film 30A and region 52B of optical thin film 30B may be referred to as thin film pair 52. A set of region 53A of optical thin film 30A and region 53B of optical thin film 30B may be referred to as thin film pair 53.

[0039] The distance between the thin film pair 51 is d 1 , the distance between the thin film pair 52 is d 2 , the distance between the thin film pair 53 is d 3 Here, the distance d 1 , d 2 , d 3 d 1 >d 2 >d 3 In other words, the distance between the thin film pair 51 is d 1 , the distance between the thin film pair 52 is d 2 The regions 51A and 52A of the first surface 21 are dug out so as to have the following structure.

[0040] When white light is input toward the optical thin film 30B, the distance d 1 The transmission wavelength λ corresponding to 1 The light is output at a distance d from the thin film pair 52. 2 The transmission wavelength λ corresponding to 2 The light is output at a distance d from the thin film pair 53. 3 The transmission wavelength λ corresponding to 3 The light emitted is

[0041] By inputting white light, the transmission wavelength λ 1 , λ 2 , λ 3 In other words, it is possible to realize an optical filter 10 that can selectively transmit and output light in a wide range of wavelengths.

[0042] In addition, the optical thin film 30A can be formed in one step by deposition on the first surface 21, and the distance d 1 , d 2 , d 3can be formed all at once by digging into the first surface 21, which makes it easy to miniaturize the optical filter 10. Similarly, the support 40 and the optical thin film 30B can be formed all at once, which eliminates the need for bonding, and makes it easy to maintain a predetermined gap. The same is true in terms of ensuring the positional misalignment and parallelism between the mirrors.

[0043] 3 shows an example of the optical filter 10 having three thin film pairs with different distances d, the optical filter 10 may have any number of thin film pairs as long as it is two or more. Furthermore, the region 53A may be read as the first region, and the region 52A may be read as the second region. Alternatively, the region 52A may be read as the first region, and the region 51A may be read as the second region. Furthermore, the optical thin film 30A may be read as the first optical thin film, and the optical thin film 30B may be read as the second optical thin film.

[0044] <Second configuration example> Fig. 4 is a schematic diagram showing a second configuration example of the optical filter 10 according to the present embodiment. The optical filter 10 in Fig. 4 has similar components to the optical filter 10 in Fig. 3, but differs from the optical filter 10 in Fig. 3 in the positions at which the electrode sections 61A, 61B, 62A, 62B, 63A, and 63B are arranged.

[0045] The electrode portion 61A is disposed along the outer edge of the region 51A of the optical thin film 30A, and the electrode portion 61B is disposed along the outer edge of the region 51B of the optical thin film 30B. That is, the electrode portion 61A and the electrode portion 61B are disposed to face each other.

[0046] The electrode portion 62A is disposed along the outer edge of the region 52A of the optical thin film 30A, and the electrode portion 62B is disposed along the outer edge of the region 52B of the optical thin film 30B. That is, the electrode portion 62A and the electrode portion 62B are disposed opposite each other.

[0047] The electrode portion 63A is disposed along the outer edge of the region 53A of the optical thin film 30A, and the electrode portion 63B is disposed along the outer edge of the region 53B of the optical thin film 30B. That is, the electrode portion 63A and the electrode portion 63B are disposed opposite each other.

[0048] When a voltage is applied to the electrode portion 61A and the electrode portion 61B, the region 51B of the optical thin film 30B, which is the inner edge of the electrode portion 61B, is bent in a direction approaching the region 51A of the optical thin film 30A due to electrostatic attraction. 1 becomes shorter.

[0049] When a voltage is applied to the electrode portion 62A and the electrode portion 62B, the region 52B of the optical thin film 30B, which is the inner edge of the electrode portion 62B, is bent in a direction approaching the region 52A of the optical thin film 30A due to electrostatic attraction. 2 becomes shorter.

[0050] When a voltage is applied to the electrode portion 63A and the electrode portion 63B, the region 53B of the optical thin film 30B, which is the inner edge of the electrode portion 63B, is bent in a direction approaching the region 53A of the optical thin film 30A due to electrostatic attraction. 3 becomes shorter.

[0051] Thus, by adjusting the voltages applied to the electrodes 61A, 61B, 62A, 62B, 63A, and 63B, the distance d 1 , d 2 , d 3 Therefore, the transmission wavelength λ 1 , λ 2 , λ 3 Therefore, it is possible to realize an optical filter 10 that can selectively transmit and output light of a wider range of wavelengths.

[0052] Moreover, electrode portion 61A is disposed along the outer edge of region 51A, not in region 51A where the recess is formed. Similarly, electrode portion 62A is disposed along the outer edge of region 52A, not in region 52A where the recess is formed. Therefore, the distance between electrode portion 61A and electrode portion 61B, the distance between electrode portion 62A and electrode portion 62B, and the distance between electrode portion 63A and electrode portion 63B are all set to a common distance d 3 Since the magnitude of the electrostatic attraction varies depending on the distance between the electrodes, according to the configuration shown in FIG.3 Therefore, the thin film pair 51, the thin film pair 52, and the thin film pair 53 can all achieve the same distance change when the same voltage is applied, making it easy to control the transmission wavelength.

[0053] The electrode portions 61A and 61B, the electrode portions 62A and 62B, and the electrode portions 63A and 63B may be configured to be capable of controlling the applied voltages individually. 1 , d 2 , d 3 Even if there is manufacturing variation in the voltage, the variation can be corrected by adjusting the applied voltage.

[0054] 4 shows an example of the optical filter 10 having three thin film pairs with different distances d, but the optical filter 10 may have any number of thin film pairs as long as the number is two or more. The region 53A may be read as the first region, the region 52A as the second region, the electrode portion 63A as the first electrode portion, the electrode portion 63B as the second electrode portion, the electrode portion 62A as the third electrode portion, and the electrode portion 62B as the fourth electrode portion. Alternatively, the region 52A may be read as the first region, the region 51A as the second region, the electrode portion 62A as the first electrode portion, the electrode portion 62B as the second electrode portion, the electrode portion 61A as the third electrode portion, and the electrode portion 61B as the fourth electrode portion.

[0055] The optical filter 10 shown in FIG. 4 is manufactured, for example, through the following steps S1 to S9. (S1) By anisotropic etching or the like, trenches are formed in regions 51A and 52A in substrate 20. Here, it is not necessary to form a trench in region 53A of substrate 20. (S2) The lower optical thin film 30A is formed on the substrate 20 by deposition or the like. (S3) The regions of the lower optical thin film 30A corresponding to the electrode portions 61A, 62A, and 63A (that is, the outer edge of the region 51A, the outer edge of the region 52A, and the outer edge of the region 53A) are made conductive by ion implantation or the like. (S4) Supports 40 are formed in regions other than the regions 51A, 52A, and 53A and their outer edges by thermal oxidation or the like. (S5) The upper optical thin film 30B is formed by deposition or the like. (S6) The regions of the upper optical thin film 30B corresponding to the electrode portions 61B, 62B, and 63B (that is, the outer edge of the region 51B, the outer edge of the region 52B, and the outer edge of the region 53B) are made conductive by ion implantation or the like. (S7) A sacrificial layer etching window is formed in the upper optical thin film 30B by dry etching or the like. (S8) Electrode extraction wiring circuits are formed in the regions of the electrode portions 61A, 61B, 62A, 62B, 63A, and 63B of the optical thin films 30A and 30B by metal sputtering or the like. (S9) The gap (d 1 ,d 2 ,d 3 ) is formed. This allows the small-sized optical filter 10 to be manufactured easily.

[0056] The lower optical thin film 30A and the upper optical thin film 30B each have a multi-layer structure in which high-refractive index materials and low-refractive index materials are alternately laminated. Therefore, the processes of deposition and ion implantation are repeated multiple times. Moreover, the lower optical thin film 30A and the upper optical thin film 30B preferably have the same number of layers in the lamination direction (Z-axis direction), and it is desirable that the lamination order of the high-refractive index materials and the low-refractive index materials be symmetrical.

[0057] <Third configuration example> FIG. 5 is a schematic diagram showing a third configuration example of the optical filter 10 according to the present embodiment.

[0058] 5 has an optical thin film 71A formed in region 51A, an optical thin film 72A formed in region 52A, and an optical thin film 73A formed in region 53A on the first surface 21 of the substrate 20. In addition, the optical filter 10 has an optical thin film 71B arranged opposite the optical thin film 71A, an optical thin film 72B arranged opposite the optical thin film 72A, and an optical thin film 73B arranged opposite the optical thin film 73A.

[0059] In addition, the optical filter 10 has electrode portions 61A, 61B, 62A, 62B, 63A, and 63B.

[0060] The electrode portion 61A is disposed along the outer edge of the region 51A of the optical thin film 71A, and the electrode portion 61B is disposed along the outer edge of the region 51B of the optical thin film 71B. That is, the electrode portion 61A and the electrode portion 61B are disposed to face each other.

[0061] The electrode portion 62A is disposed along the outer edge of the region 52A of the optical thin film 72A, and the electrode portion 62B is disposed along the outer edge of the region 52B of the optical thin film 72B. That is, the electrode portion 62A and the electrode portion 62B are disposed to face each other.

[0062] The electrode portion 63A is disposed along the outer edge of the region 53A of the optical thin film 73A, and the electrode portion 63B is disposed along the outer edge of the region 53B of the optical thin film 73B. That is, the electrode portion 63A and the electrode portion 63B are disposed opposite each other.

[0063] Hereinafter, the set of optical thin films 71A and 71B may be referred to as thin film pair 71. The set of optical thin films 72A and 72B may be referred to as thin film pair 72. The set of optical thin films 73A and 73B may be referred to as thin film pair 73.

[0064] The distance between the thin film pair 71, the distance between the thin film pair 72, and the distance between the thin film pair 73 are all d 1 It is.

[0065] The optical thin films 71A and 71B and the optical thin films 72A and 72B have different thin film configurations and have different transmission characteristics. The optical thin films 72A and 72B and the optical thin films 73A and 73B have different thin film configurations and have different transmission characteristics. Similarly, the optical thin films 73A and 73B and the optical thin films 71A and 71B have different thin film configurations and have different transmission characteristics.

[0066] For example, the optical thin films 71A and 71B are spaced apart by a distance d 1When white light is input, the wavelength λ 1 For example, the optical thin films 72A and 72B have an optical characteristic that the light is output at a distance d 1 When white light is input, the wavelength λ 2 For example, the optical thin films 73A and 73B have an optical characteristic that the light is output at a distance d 1 When white light is input, the wavelength λ 3 The optical characteristic is that light of λ 1 , λ 2 , λ 3 is λ 1 <λ 2 <λ 3 The relationship may be as follows.

[0067] The difference in optical characteristics is due to the difference in at least one of the material, film thickness, number of layers, refractive index, and transmittance of the optical thin films 71A, 71B, 72A, 72B, 73A, and 73B.

[0068] When a voltage is applied to the electrode portion 61A and the electrode portion 61B, the region 51B of the optical thin film 71B, which is the inner edge of the electrode portion 61B, is bent in a direction approaching the region 51A of the optical thin film 71A due to electrostatic attraction. 1 becomes shorter.

[0069] When a voltage is applied to the electrode portion 62A and the electrode portion 62B, the region 52B of the optical thin film 72B, which is the inner edge of the electrode portion 62B, is bent in a direction approaching the region 52A of the optical thin film 72A due to electrostatic attraction. 1 becomes shorter.

[0070] When a voltage is applied to the electrode portion 63A and the electrode portion 63B, the region 53B of the optical thin film 73B, which is the inner edge of the electrode portion 63B, is bent in a direction approaching the region 53A of the optical thin film 73A due to electrostatic attraction. 1 becomes shorter.

[0071] Thus, by adjusting the voltages applied to the electrodes 61A, 61B, 62A, 62B, 63A, and 63B, the distances d 1 Therefore, the transmission wavelength λ 1 , λ 2 , λ 3 Therefore, it is possible to realize an optical filter 10 that can selectively transmit and output light of a wider range of wavelengths.

[0072] The electrode portions 61A and 61B, the electrode portions 62A and 62B, and the electrode portions 63A and 63B may be configured to be capable of controlling the applied voltages individually. 1 Even if there is manufacturing variation or initial variation in the optical properties of each of the thin film pairs 71, 72, and 73, the variation can be corrected by adjusting the applied voltage.

[0073] 5 shows an example of the optical filter 10 having three thin film pairs with different optical characteristics, the optical filter 10 may have any number of thin film pairs as long as it is two or more. Also, the optical thin film 71A may be read as the first optical thin film, the optical thin film 71B as the second optical thin film, the optical thin film 72A as the third optical thin film, and the optical thin film 72B as the fourth optical thin film. Alternatively, the optical thin film 72A may be read as the first optical thin film, the optical thin film 72B as the second optical thin film, the optical thin film 73A as the third optical thin film, and the optical thin film 73B as the fourth optical thin film.

[0074] <Example of spectroscopic sensor configuration> Fig. 6 is a block diagram showing a configuration example of a spectroscopic sensor 80 including the optical filter 10 according to the present embodiment. The spectroscopic sensor 80 including the optical filter 10 shown in Fig. 4 will be described below. However, the spectroscopic sensor 80 may also include the optical filter 10 shown in Fig. 3 or Fig. 5.

[0075] 6, the spectroscopic sensor 80 includes a light source 81, a PC 82, an optical filter 10, a light receiving element 91, and a control unit 92. The optical filter 10, the light receiving element 91, and the control unit 92 may be collectively referred to as a sensor module 90. The light source 81 may be built into the sensor module 90, and in that case, it operates in response to a command from the control unit 92, just like the optical filter 10.

[0076] Examples of the light source 81 include a tungsten lamp, a halogen lamp, and an LED (Light Emitting Diode). The light source 81 outputs white light toward the optical filter 10 and the light receiving element 91. The measurement object 83 is disposed between the light source 81 and the optical filter 10. Examples of the measurement object 83 include some kind of liquid or gas.

[0077] The optical filter 10 receives light that is output from the light source 81 and passes through the object 83. The optical filter 10 then outputs light of a transmission wavelength that has passed through the thin film pair 51, 52, and 53 as described above.

[0078] Furthermore, when measuring reflected light, the measurement object 83 is placed on the same side as the light source 81. Examples of the measurement object 83 include some solid or metal. In this case as well, the light output from the light source 81 and reflected by the measurement object 83 is input to the optical filter 10. Then, the optical filter 10 outputs light of the transmission wavelength that has passed through the thin film pair 51, 52, and 53 as described above.

[0079] The control unit 92 controls the voltages applied to the electrodes 61A, 61B, 62A, 62B, 63A, and 63B of the optical filter 10, thereby adjusting the distance d 1 , d 2 , d 3 That is, the control unit 92 selects the transmission wavelength.

[0080] The light receiving element 91 is configured by, for example, a photodiode. The light receiving element 91 receives the light output from the optical filter 10, and outputs an electric signal (current) at a level according to the amount of the received light.

[0081] The PC 82 instructs the control unit 92 on the magnitude of the voltage to be applied to the electrodes 61A, 61B, 62A, 62B, 63A, and 63B. The PC 82 also analyzes and displays the wavelength components of the light received by the light receiving element 91. This allows the user to operate the PC 82 to measure the wavelength components of the light passing through or reflected by the object 83 (or the wavelength components of the light not passing through or reflected by the object 83). Therefore, for example, the user can perform a qualitative or quantitative evaluation of the components of the object 83, such as a component analysis and content rate, based on the wavelength components of the light displayed on the PC 82.

[0082] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, corrections, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also belong to the technical scope of the present disclosure. In addition, the components in the above-mentioned embodiments may be arbitrarily combined within the scope of the invention. [Industrial Applicability]

[0083] The technology disclosed herein is useful for expanding the selection range of transmission wavelengths in optical filters and spectroscopic sensors, and can be used, for example, for component analysis of a measurement object. [Explanation of symbols]

[0084] 10 Optical Filters 20 Substrate 21 Page 1 22 Side 2 30A, 30B, 71A, 71B, 72A, 72B, 73A, 73B Optical thin film 40 Support 50, 51, 52, 71, 72, 73 Thin film pair 50A, 50B, 51A, 51B, 52A, 52B, 53A, 53B area 61A, 61B, 62A, 62B, 63A, 63B Electrode section 80 Spectroscopic Sensor 81 Light source 82 PC 83 Measurements 90 Sensor Module 91 Photodetector 92 Control section

Claims

1. a substrate that is optically transparent and has a first surface and a second surface; a first region which is a predetermined region on the first surface; a second region that is different from the first region on the first surface and is closer to the second surface than the first region; a first optical thin film formed collectively on the first surface of the substrate including the first region and the second region; a second optical thin film disposed opposite the first surface at a predetermined distance from the first surface, Optical filters.

2. a first electrode portion formed by making an outer edge portion of the first region of the first optical thin film conductive; a second electrode portion formed by making conductive a region of the second optical thin film that is disposed opposite to an outer edge portion of the first region; a third electrode portion formed by making an outer edge portion of the second region of the first optical thin film conductive; a fourth electrode portion formed by making conductive a region of the second optical thin film that faces an outer edge portion of the second region, when a voltage is applied to the first electrode portion and the second electrode portion, an electrostatic attraction is generated to deflect a region of the second optical thin film facing the first region in a direction approaching the first optical thin film; the third electrode portion and the fourth electrode portion, when a voltage is applied thereto, deflect a region of the second optical thin film facing the second region in a direction approaching the first optical thin film by electrostatic attraction.

2. The optical filter of claim 1.

3. The application of a voltage to the first electrode portion and the second electrode portion and the application of a voltage to the third electrode portion and the fourth electrode portion are controlled individually.

3. The optical filter of claim 2.

4. An optical filter according to any one of claims 1 to 3; A light source that outputs light toward the measurement object; a light receiving element that receives light that is output from the light source, passes through or is reflected by the object, and is transmitted through the optical filter; Spectroscopic sensor.

5. A method for manufacturing an optical filter, comprising the steps of: forming a recess in at least one of a first region and a second region of a light-transmitting substrate; forming a first optical thin film on the surface of the substrate on which the recess is formed; making an outer edge portion of the first region and an outer edge portion of the second region of the first optical thin film conductive; forming a support in a region different from the first region, the second region, and the conductive region; forming a second optical thin film supported by the support and facing the first optical thin film; a region of the second optical thin film facing an outer edge portion of the first region and a region of the second optical thin film facing an outer edge portion of the second region are made conductive; A method for manufacturing an optical filter.

6. moreover, forming a sacrificial layer etching window in the second optical thin film; forming an electrode extraction wiring circuit in the conductive region of the first optical thin film and the second optical thin film; forming a gap between the first optical thin film and the second optical thin film in the first region and the second region; A method for manufacturing the optical filter according to claim 5.

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