JP7645488B2 - Optical filter, spectroscopic sensor, and method for manufacturing optical filter - Google Patents

Description

This disclosure relates to an optical filter, a spectroscopic sensor, and a method for manufacturing an optical filter.

A Fabry-Perot interference type optical filter is known that outputs light of a specific wavelength when light of a wide wavelength band is input. Patent Document 1 discloses an optical filter that includes a first substrate having a plurality of step portions of different heights, a second substrate bonded opposite 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 containing 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.

JP 2010-204457 A

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 together, but the smaller the optical filter, the more difficult it becomes to maintain a specified gap between the first and second mirror pairs. Similarly, it becomes difficult to ensure 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.

The objective of the present disclosure is to provide an optical filter that is small and easy to manufacture, and is capable of outputting light of multiple desired wavelengths, a spectroscopic sensor equipped with an optical filter, and a method for manufacturing an optical filter.

An optical filter according to one embodiment of the present disclosure includes a substrate that transmits light and has a first surface and a second surface, a first region that is a predetermined region on the first surface, a second region that is a region on the first surface that is different 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 and second regions, and a second optical thin film disposed opposite the first surface and spaced a predetermined distance from the first surface.

An optical filter according to one aspect of the present disclosure includes a substrate that transmits light and has a first surface and a second surface, a first optical thin film formed in a first region that is a predetermined region on the first surface, a second optical thin film arranged facing the first optical thin film at a predetermined distance from the first surface, a third optical thin film formed in a second region that is a region on the first surface different from the first region, and a fourth optical thin film arranged facing the third optical thin film at the predetermined distance from the first surface, and at least one of the first optical thin film and the second optical thin film has optical characteristics different from at least one of the third optical thin film and the fourth optical thin film.

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

A method for manufacturing an optical filter according to one aspect 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 the surface of the substrate on which the recess is formed, making the outer edge of the first region and the 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 the region of the second optical thin film facing the outer edge of the first region and the outer edge of the second region conductive.

The present disclosure provides an optical filter that is small and easy to manufacture, and is capable of outputting light of multiple desired wavelengths, a spectroscopic sensor equipped with an optical filter, and a method for manufacturing an optical filter.

FIG. 1 is a diagram for explaining a Fabry-Perot interference type optical filter. FIG. 1 is a diagram for explaining the wavelength tunable range of the wavelength output from an optical filter. FIG. 1 is a schematic diagram showing a first configuration example of an optical filter according to an embodiment of the present invention; FIG. 1 is a schematic diagram showing a second configuration example of an optical filter according to an embodiment of the present invention; FIG. 13 is a schematic diagram showing a third configuration example of the optical filter according to the embodiment; 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.

Below, the embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters and duplicate explanation of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Note that the attached drawings and the following explanation 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.

(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.

The optical filter 10 comprises a substrate 20, an optical thin film 30A, an optical thin film 30B, and a support 40.

The substrate 20 is in the form of a flat plate made of a light-transmitting material and has a first surface 21 and a second surface 22 opposite the first surface 21.

For ease 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 and Z axes, that is, the axis extending from the front to the back of the paper, is defined as the Y axis. For ease 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 directional expressions are used for ease of explanation and are not intended to limit the position of the structure when actually used. The same applies to the other drawings.

The optical thin film 30A is formed (e.g., by vapor deposition) on the first surface 21 of the substrate 20. The optical thin film 30A is a multilayer film in which high-refractive index materials and low-refractive index materials are alternately laminated.

Optical thin film 30B is disposed opposite optical thin film 30A. 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 optical thin film 30A with an air layer between them.

Examples of materials with a high refractive index include titanium oxide film (TiO ₂ ) and silicon (Si). The refractive index of titanium oxide film is about 2.5, and the refractive index of silicon is about 3.6. Examples of materials with a low refractive index include silicon oxide film (SiO ₂ ) and silicon nitride film (SiN). The refractive index of silicon oxide film is about 1.5, and the refractive index of 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.

1A, 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 (e.g., an air layer) is formed between the region 50A and the region 50B.

The support 40 is disposed between an area of the optical thin film 30A different from the area 50A and the electrode portion 60A and an area of the optical thin film 30B different from the area 50B and the electrode portion 60B, and supports the optical thin film 30B. For example, the support 40 extends upward from an area of the optical thin film 30A different from the area 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.

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, light of wavelength λ ₁ corresponding to the distance d ₁ is 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 light output after passing through the thin film pair 50 may be referred to as a transmission wavelength. For example, in the case of a tungsten light source, the wavelength band of the white light is 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 because it varies depending on the illumination light source used.

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

In this way, the Fabry-Perot interference type optical filter 10 can selectively output light of any wavelength between _λ1 and _λ2 from the input white light by changing the distance between the thin film pair 50 between _d1 and _d2 .

The following method is available for bending 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 parts 60A and 60B are provided at predetermined positions of 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 a limit to the amount by which the optical thin film 30B can be bent. That is, there is a limit to the method of bending the optical thin film 30B to expand the wavelength tunable range between λ ₁ and λ ₂ shown in FIG. 2(a).

Therefore, in this embodiment, a plurality of thin film pairs are formed in the optical filter 10 so that different transmission wavelengths are output. This makes it possible to output light of any transmission wavelength in a wider range than when the transmission wavelength is changed only by the bending of the optical thin film 30B. For example, by forming a plurality of thin film pairs in the optical filter 10 so that the transmission wavelengths from λ ₁ to λ ₂ , λ ₂ to λ ₃ , and λ ₃ to λ ₄ (where λ ₁ < λ ₂ < λ ₃ < λ ₄ ) are output, the wavelength tunable range can be expanded to between λ ₁ and λ ₄ as shown in FIG. 2B. A specific configuration example of such an optical filter 10 will be described below.

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

The optical filter 10 comprises a substrate 20, an optical thin film 30A, an optical thin film 30B, and a support 40.

The substrate 20 is made of a light-transmitting material and has a first surface 21 and a second surface 22 opposite 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 regions 51A, 52A, 53A, the electrode portion 61A, the electrode portion 62A, and the electrode portion 63A are different regions on the first surface 21.

Region 52A is closer to the second surface 22 than region 53A. That is, in region 52A, the first surface 21 is recessed in a direction approaching the second surface 22.

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

As shown in FIG. 3, no recess is formed in region 53A. However, region 53A may have a recess that is shallower than region 52A, for example.

The recesses in regions 52A and 51A are formed by etching the first surface 21 of the substrate 20. This makes it easy to form the recesses in regions 52A and 51A in a single step.

The optical thin film 30A is formed with a predetermined 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 deposition processing. This allows the optical thin film 30A with steps to be easily formed all at once on the first surface 21.

The support 40 extends upward from areas of the first surface 21 other than the areas 51A, 52A, 53A, electrode portion 61A, electrode portion 62A, and electrode portion 63A, and supports the optical thin film 30B.

Optical thin film 30B is disposed opposite optical thin film 30A. Optical thin film 30B is supported by support 40.

Optical thin film 30B has region 51B which faces region 51A of optical thin film 30A, region 52B which faces region 52A of optical thin film 30A, and region 53B which faces region 53A of optical thin film 30A.

Hereinafter, the 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. The 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. The 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.

The distance between the thin film pair 51 may be expressed as d ₁ , the distance between the thin film pair 52 as d ₂ , and the distance between the thin film pair 53 as d _3. Here, the distances d ₁ , d ₂ , and d ₃ have a relationship of d ₁ > d ₂ > d _3. In other words, the regions 51A and 52A of the first surface 21 are each recessed so that the distance between the thin film pair 51 is d ₁ , and the distance between the thin film pair 52 is d ₂ .

When white light is input toward the optical thin film 30B, light having a transmission wavelength λ ₁ corresponding to the distance d ₁ is output from the thin film pair 51, light having a transmission wavelength λ ₂ corresponding to the distance d ₂ is output from the thin film pair 52, and light having a transmission wavelength λ ₃ corresponding to the distance d ₃ is output from the thin film pair 53.

This makes it possible to realize the optical filter 10 that can output light having transmission wavelengths λ ₁ , λ ₂ , and λ ₃ by inputting white light. In other words, it is possible to realize the optical filter 10 that can selectively transmit and output light having a wide range of wavelengths.

Moreover, the optical thin film 30A can be formed all at once by deposition on the first surface 21, and the distances _d1 , _d2 , _d3 of the thin film pair 51, 52, 53 can be formed all at once by engraving the first surface 21, so that the optical filter 10 can be easily miniaturized. Moreover, the support 40 and the optical thin film 30B can also be formed all at once, so there is no need to bond them, and it is easy to maintain the gap at a specified distance. The same applies to ensuring the positional misalignment and parallelism between the mirrors.

Note that while FIG. 3 shows an example of an 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 they are two or more. Also, region 53A may be read as the first region, and region 52A may be read as the second region. Alternatively, region 52A may be read as the first region, and region 51A may be read as the second region. Also, optical thin film 30A may be read as the first optical thin film, and optical thin film 30B may be read as the second optical thin film.

<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.

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. In other words, the electrode portion 61A and the electrode portion 61B are disposed opposite each other.

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. In other words, the electrode portion 62A and the electrode portion 62B are disposed opposite each other.

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. In other words, the electrode portion 63A and the electrode portion 63B are disposed opposite each other.

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 portion of the electrode portion 61B, is deflected by electrostatic attraction in a direction approaching the region 51A of the optical thin film 30A. In other words, the distance _d1 of the thin film pair 51 becomes shorter.

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 deflected by electrostatic attraction in a direction approaching the region 52A of the optical thin film 30A. In other words, the distance _d2 between the thin film pair 52 becomes shorter.

When a voltage is applied to the electrode portion 63A and the electrode portion 63B, the electrostatic attraction causes the region 53B of the optical thin film 30B, which is the inner edge portion of the electrode portion 63B, to bend in a direction approaching the region 53A of the optical thin film 30A. In other words, the distance _d3 of the thin film pair 53 becomes shorter.

As a result, by adjusting the voltages applied to the electrodes 61A, 61B, 62A, 62B, 63A, and 63B, the distances _d1 , _d2 , and _d3 can be changed, and the transmission wavelengths _λ1 , _λ2 , and _λ3 can be changed, thereby realizing the optical filter 10 that can selectively transmit and output light of a wider range of wavelengths.

Moreover, the electrode portion 61A is disposed along the outer edge of the region 51A, not in the region 51A where the recess is formed. Similarly, the electrode portion 62A is disposed along the outer edge of the region 52A, not in the region 52A where the recess is formed. Therefore, the distance between the electrode portion 61A and the electrode portion 61B, the distance between the electrode portion 62A and the electrode portion 62B, and the distance between the electrode portion 63A and the electrode portion 63B can all be 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. 4, the distance between any of the electrodes can be a common distance d _3. Therefore, the same distance change can be realized for the thin film pair 51, the thin film pair 52, and the thin film pair 53 in response to the same voltage application, and the control of the transmission wavelength becomes easy.

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, so that even if there are manufacturing variations in the initial distances _d1 , _d2 , and _d3 , for example, the variations can be corrected by adjusting the applied voltage.

Although FIG. 4 shows an example of an 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 they are two or more. Also, 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.

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 the substrate 20. Here, it is not necessary to form a trench in region 53A of the 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 by thermal oxidation or the like in regions other than the regions 51A, 52A, and 53A and their outer edges.
(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) Gaps (d ₁ , d ₂ , d ₃ ) are formed between the lower optical thin film 30A and the upper optical thin film 30B in the regions 51A, 52A, and 53A by sacrificial layer etching or the like.
This allows the optical filter 10 to be manufactured easily in a compact size.

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

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

The optical filter 10 shown in FIG. 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.

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

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. In other words, the electrode portion 61A and the electrode portion 61B are disposed opposite each other.

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. In other words, the electrode portion 62A and the electrode portion 62B are disposed opposite each other.

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. In other words, the electrode portion 63A and the electrode portion 63B are disposed opposite each other.

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.

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 _d1 .

Optical thin films 71A and 71B and optical thin films 72A and 72B have different thin film configurations and different transmission characteristics. Optical thin films 72A and 72B and optical thin films 73A and 73B have different thin film configurations and different transmission characteristics. Similarly, optical thin films 73A and 73B and optical thin films 71A and 71B have different thin film configurations and different transmission characteristics.

For example, the optical thin films 71A and 71B have the optical characteristic that, when white light is input at a distance d ₁ , light of wavelength λ ₁ is output. For example, the optical thin films 72A and 72B have the optical characteristic that, when white light is input at a distance d ₁ , light of wavelength λ ₂ is output. For example, the optical thin films 73A and 73B have the optical characteristic that, when white light is input at a distance d ₁ , light of wavelength λ ₃ is output. Note that λ ₁ , λ ₂ , and λ ₃ may have a relationship of λ ₁ < λ ₂ < λ ₃ .

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

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 portion of the electrode portion 61B, is deflected by electrostatic attraction in a direction approaching the region 51A of the optical thin film 71A. In other words, the distance _d1 between the thin film pair 71 becomes shorter.

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 portion of the electrode portion 62B, is deflected by electrostatic attraction in a direction approaching the region 52A of the optical thin film 72A. In other words, the distance _d1 between the thin film pair 72 becomes shorter.

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 portion of the electrode portion 63B, is deflected by electrostatic attraction in a direction approaching the region 53A of the optical thin film 73A. In other words, the distance _d1 between the thin film pair 73 becomes shorter.

Thus, by adjusting the voltages applied to the electrodes 61A, 61B, 62A, 62B, 63A, and 63B, the distance _d1 between each of the thin film pairs 71, 72, and 73 can be changed, and the transmission wavelengths _λ1 , _λ2 , and _λ3 can be changed. Thus, an optical filter 10 can be realized that can selectively transmit and output light of a wider range of wavelengths.

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, so that even if there is a manufacturing variation in the distance _d1 between the initial thin film pairs 71, 72, and 73 or a variation in the optical characteristics of the initial thin film pairs 71, 72, and 73, the variation can be corrected by adjusting the applied voltage.

Note that while FIG. 5 shows an example of an optical filter 10 having three pairs of thin films with different optical characteristics, the optical filter 10 may have any number of pairs of thin films as long as they are two or more. Also, optical thin film 71A may be read as the first optical thin film, optical thin film 71B as the second optical thin film, optical thin film 72A as the third optical thin film, and optical thin film 72B as the fourth optical thin film. Alternatively, optical thin film 72A may be read as the first optical thin film, optical thin film 72B as the second optical thin film, optical thin film 73A as the third optical thin film, and optical thin film 73B as the fourth optical thin film.

<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 include the optical filter 10 shown in Fig. 3 or Fig. 5.

As shown in FIG. 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 also be built into the sensor module 90, in which case it operates in response to commands from the control unit 92, just like the optical filter 10.

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

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

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

The control unit 92 controls the distances d ₁ , d ₂ , and d ₃ between the thin film pairs 51, 52, and 53 by controlling the voltages applied to, for example, the electrode units 61A, 61B, 62A, 62B, 63A, and 63B included in the optical filter 10. In other words, the control unit 92 selects the transmission wavelength.

The light receiving element 91 is composed of, for example, a photodiode. The light receiving element 91 receives the light output from the optical filter 10 and outputs an electrical signal (current) at a level corresponding to the amount of light received.

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 that passes through or is reflected by the object 83 (or the wavelength components of the light that does not pass through or is not 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 the content rate, based on the wavelength components of the light displayed on the PC 82.

Although the embodiments have been described above with reference to the attached 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 fall within the technical scope of the present disclosure. Furthermore, the components in the above-described embodiments may be combined in any manner as long as they do not deviate from the spirit of the invention.

The technology disclosed herein is useful for expanding the range of transmission wavelengths available in optical filters and spectroscopic sensors, and can be used, for example, in component analysis of measured objects.

10 Optical filter 20 Substrate 21 First surface 22 Second surface 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 Region 61A, 61B, 62A, 62B, 63A, 63B Electrode portion 80 Spectroscopic sensor 81 Light source 82 PC
83 Measurement object 90 Sensor module 91 Light receiving element 92 Control unit

Claims (6)

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. 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;
when a voltage is applied to the third electrode portion and the fourth electrode portion, an electrostatic attraction is generated to deflect a region of the second optical thin film facing the second region in a direction approaching the first optical thin film.
2. The optical filter of claim 1. 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. An optical filter according to any one of claims 1 to 3 ;
A light source that outputs light toward a 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. 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. 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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