JP2016133658A - Optical filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical filter having a wider wavelength band in which the filter is functional.SOLUTION: An optical filter 3 includes a functional unit 7 having a plurality of filter pieces 14 separated by slits 13, where at least a surface of each filter piece is covered with a precious metal layer 15 and where filter pieces are supported in a manner that allows a slit width to be varied. Such an arrangement allows for better suppressing the pull-in phenomenon and process constraints and for appropriately increasing a variable range compared to conventional Fabry-Perot filters. As a result, the optical filter can extract light in a wider wavelength band compared with conventional optical filters.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical filter that reflects light of a specific wavelength and transmits other light.

  Patent Document 1 listed below discloses an invention relating to an infrared analysis apparatus including a Fabry-Perot filter, a light source, an infrared detector, and the like in a gas cell.

  The Fabry-Perot filter has a configuration in which a fixed mirror having a fixed electrode and a movable mirror having a movable electrode are opposed to each other via an air gap. In the Fabry-Perot filter, the size of the gap can be changed by electrostatically driving between the fixed mirror and the movable mirror. Then, infrared rays having a wavelength corresponding to the size of the gap can be transmitted.

JP 2003-177093 A

  However, the operation region of the conventional Fabry-Perot filter is often about 3 μm, and cannot cover a wide wavelength band. This is because, in a parallel plate type electrostatic drive actuator used for a movable mirror, if the movable mirror is changed too much, a pull-in phenomenon occurs in which the movable mirror is attracted to the fixed mirror.

  Such a pull-in phenomenon is likely to occur because the conventional Fabry-Perot filter has a gap closing (Gap-Closing) type movable structure that changes the gap between the movable mirror and the fixed mirror from the initial stage. Yes.

  In order to avoid the pull-in phenomenon, it is difficult to realize a conventional Fabry-Perot filter that is movable in the film thickness direction due to the complexity of the structure and the restrictions on the process.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an optical filter capable of widening a wavelength band that exhibits a filter function as compared with the related art.

  The optical filter in the present invention includes a functional unit having a plurality of filter pieces divided through slits, and at least the surface of each filter piece is covered with a noble metal layer, and the slit interval of each filter piece is movable. It is supported by. In the present invention, a surface plasmon can be induced with respect to incident light by forming a noble metal layer on the surface of each filter piece. At this time, a plurality of filter pieces are arranged in parallel through slits as in the present invention. By providing, light of a specific wavelength can be extracted as reflected light. Since the wavelength of the reflected light changes when the slit interval changes, the wavelength band of the reflected light extracted from the optical filter can be selected according to the slit interval by moving the slit interval as in the present invention. Moreover, in the present invention, the filter is divided into each filter piece by inserting a slit, and each filter piece is moved in a direction in which the slit interval fluctuates, so that each filter is moved horizontally. With such a configuration of the present invention, pull-in phenomenon and process restrictions can be suppressed as compared with the conventional one, and the movable range can be appropriately expanded as compared with the conventional Fabry-Perot filter in which the movable part moves in the film thickness direction. be able to. As a result, it is possible to widen the wavelength band of light that can be extracted by the optical filter as compared with the conventional case.

  In this invention, it is preferable that the drive electrode part for moving the said slit space | interval is provided. The functional unit can be appropriately driven by driving the drive electrode unit.

  In the present invention, the drive electrode unit is configured to include a movable electrode and a fixed electrode, the movable electrode is connected to the functional unit, and the fixed electrode is provided at a position facing the movable electrode. It is preferable. Thereby, a driving force can be given to the functional part by the electrostatic attractive force between the movable electrode and the fixed electrode, and the slit interval of the functional part can be varied.

  In the present invention, it is preferable that each of the movable electrode and the fixed electrode is formed of a comb-like electrode having a plurality of electrode teeth. Thereby, the driving force of the drive electrode unit can be increased, and the slit interval of the functional unit can be appropriately adjusted so as to vary within a wide movable range. Further, the slit interval can be changed in an analog manner, and the accuracy of the filter function can be improved.

  Moreover, in this invention, it is preferable that the said function part has the said filter piece and the elastic part which connects between the edge parts of the said adjacent filter piece, and the said slit space | interval is movable by the deformation | transformation of the said elastic part. . In this way, the slit interval can be moved with a simple configuration.

  In the present invention, it is preferable that three or more filter pieces are provided, and the plurality of the slit pieces are movable while maintaining an equal interval. In this way, the functional unit can reflect light of a specific wavelength with high accuracy by moving while maintaining a plurality of slit intervals at equal intervals, and can obtain a filter function with excellent accuracy.

  Moreover, in this invention, it has a 1st base material, a 2nd base material, and the insulating layer provided between the said 1st base material and the said 2nd base material, Said 1st The functional part is processed to form the functional part, the insulating layer facing the functional part is removed, and the functional part includes the first base material and the second base material. It is preferably supported so as to be movable in a direction parallel to the planar direction. A functional part can be formed using a so-called SOI substrate (Silicon on Insulator), and a structure in which each filter piece can be moved in a direction parallel to the first base material and the second base material can be easily and appropriately formed. Can be formed.

  Moreover, in this invention, it is preferable that the said insulating layer and the said 2nd base material are not provided in the position facing the said function part. Thereby, the light of wavelengths other than the specific wavelength reflected by the functional part can be appropriately transmitted to the back side of the functional part.

  Moreover, in this invention, it is preferable that each filter piece has a base material and the said noble metal layer which covers the circumference | surroundings of a base material.

  In the present invention, the noble metal layer is preferably formed of one or more selected from gold, palladium, and platinum. Thereby, surface plasmon can be induced appropriately.

  Moreover, in this invention, it is preferable that the pitch between the said filter pieces moves within the range of 2 micrometers-7 micrometers. Thereby, infrared rays with a wider wavelength band than before can be extracted.

  According to the present invention, the pull-in phenomenon and process restrictions can be suppressed as compared with the conventional case, and the movable range can be appropriately expanded as compared with the conventional Fabry-Perot filter. As a result, it is possible to widen the wavelength band of light that can be extracted by the optical filter as compared with the conventional case.

It is a conceptual diagram of the infrared analyzer using the optical filter of this Embodiment. It is sectional drawing of an optical filter when the optical filter shown in FIG. 1 is cut | disconnected in the height direction along the AA line, and it sees from the arrow direction. It is the fragmentary sectional perspective view which expanded and showed the part of the filter piece of the optical filter shown in FIG. It is a conceptual diagram of the function part and drive electrode part of the optical filter of this Embodiment. It is a top view which shows an example of the optical filter of this Embodiment. It is a top view which shows the optical filter of another embodiment different from FIG. It is a graph which shows the infrared absorption wavelength of each gas. It is an external view for demonstrating the propagation state of the light between filter pieces. It is a conceptual diagram of a reflection spectrum. It is a graph which shows the relationship between the pitch between filter pieces, and a reflective wavelength.

  Hereinafter, an embodiment of the present invention (hereinafter abbreviated as “embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the meaning.

  FIG. 1 is a conceptual diagram of an infrared analyzer using the optical filter of the present embodiment. As shown in FIG. 1, the infrared analyzer 1 includes a light source 2, an optical filter 3, a sample cell 4, and a detector 5.

  The light source 2 includes, for example, a halogen lamp and a condensing unit, and the light source 2 is irradiated with light including infrared rays. However, the configuration of the light source 2 is not limited.

  A mirror 6 is provided between the light source 2 and the optical filter 3, and the light L1 emitted from the light source 2 is reflected by the mirror 6 and enters the optical filter 3 (hereinafter sometimes referred to as incident light L1). ). The incident angle θ1 of the light L1 incident on the optical filter 3 is incident on the functional unit 7 of the optical filter 3 from an oblique direction. When the light L1 is input from directly above the functional unit 7, the amount of transmitted light increases and the reflected light cannot be extracted in a predetermined direction. Therefore, the light L1 is preferably incident on the functional unit 7 from an oblique direction.

  Of the light L 1, infrared light having a specific wavelength is reflected by the functional unit 7 (reflected light L 2) and reaches the sample cell 4 via the mirror 8.

  The sample cell 4 has a gas inlet (not shown) and a gas outlet (not shown), and a gas for performing infrared analysis flows from the gas inlet. After the analysis is completed, the gas can flow out from the gas outlet. For example, the infrared analyzer 1 shown in FIG. 1 can measure the gas concentration in the atmosphere. The gas that has flowed into the sample cell 4 has a different infrared wavelength depending on its type. Therefore, the specific gas out of the gas flowing into the sample cell 4 absorbs the reflected light L2 made of infrared rays having a specific wavelength irradiated on the sample cell 4, and the amount of absorption is detected by the detector 5, The gas concentration of a specific gas can be detected.

  The detector 5 can be a pyroelectric element, a bolometer, a thermopile, or the like, but is not particularly limited.

  Conventionally, a Fabry-Perot filter as an optical filter incorporated in an infrared analyzer has a problem in that it has a small operating area and cannot cover a wide wavelength band.

For example, when measuring CO that affects combustion control, NO _x , SO _x or the like in which exhaust gas regulations exist, infrared rays having a wavelength band of about 4 μm to 7.5 μm are required as shown in FIG. However, the conventional Fabry-Perot filter has a narrow wavelength band that can be taken out as narrow as about 3 μm to 4.5 μm. Therefore, even if the conventional Fabry-Perot filter is incorporated in an infrared analyzer, all the gases shown in FIG. The concentration could not be measured.

  Therefore, in this embodiment, a new optical filter 3 is provided in place of the conventional Fabry-Perot filter in order to extract a wider wavelength band of light than the conventional one using the optical filter.

  FIG. 2 is a cross-sectional view of the optical filter when the optical filter shown in FIG. 1 is cut in the height direction along the line AA and viewed from the arrow direction.

  As shown in FIG. 2, the optical filter 3 includes a first base material 10, a second base material 11, and an insulating layer provided between the first base material 10 and the second base material 11. (Sacrificial layer) 12. As described above, the optical filter 3 can be formed of an SOI substrate (Silicon on Insulator) 22 having the first base material 10, the second base material 11, and the insulating layer 12.

The first base material 10 and the second base material 11 are made of silicon, and the insulating layer 12 is made of SiO ₂ .

  As shown in FIG. 2, the functional unit 7 is formed on the first base material 10. The functional unit 7 includes a filter piece 14 that is divided into a plurality of pieces through the slit 13. Each filter piece 14 is formed in a long shape extending in one direction as shown in FIG. As shown in FIG. 2, each filter piece 14 includes a first base material 10 processed into a long shape and a noble metal layer 15 covering the entire surface of the first base material 10. Each filter piece 14 may be entirely formed of a noble metal layer, but the production cost increases, the formation of not only each filter piece 14 but also an elastic part and a drive electrode, which will be described later, and the connection structure with these members are complicated. The first base material 10 is processed to form each filter piece 14 by, for example, and the noble metal layer 15 is formed on the surface of the first base material 10 constituting each filter piece 14. Is preferred. The noble metal layer 15 is formed using an existing method such as plating or sputtering.

  In the present embodiment, each filter piece 14 is supported such that the slit interval is movable. “Slit” means an interval between the filter pieces 14 and is usually formed at an elongated interval, but does not particularly define an aspect ratio of the slit.

  FIG. 3 is an enlarged partial cross-sectional perspective view showing a filter piece portion of the optical filter shown in FIG. As shown in FIG. 3, the width dimension (length dimension in the x direction) of each filter piece 14 is formed by w, the height dimension (length dimension in the z direction) is formed by h, and each filter piece 14 is formed. The pitch between them is formed by p, and the film thickness of the noble metal layer 15 is formed by t.

  The width dimension w of each filter piece 14 is, for example, 0.5 μm or less. Further, the height dimension h of each filter piece 14 is formed to be 2.2 μm or less, for example. The pitch p between the filter pieces 14 is preferably movable within a range of 2 μm to 7 μm. Further, the noble metal layer 15 is formed with a film thickness t of, for example, about 0.1 μm.

  The noble metal layer 15 is preferably formed of one or more selected from gold, palladium, and platinum. The noble metal layer 15 is particularly preferably formed of gold.

  FIG. 4 is a conceptual diagram of the functional part and the drive electrode part of the optical filter according to the present embodiment. As shown in FIG. 4, the end portions on both sides of adjacent filter pieces 14 are connected by an elastic portion (spring portion) 17. The elastic part 17 is thinner than the width dimension of each filter piece 14 (width dimension w in FIG. 3), and the elastic part 17 is formed to be elastically deformable. On the other hand, each filter piece 14 is formed with higher rigidity than the elastic portion 17. Therefore, even if the elastic part 17 is deformed, each filter piece 14 can move while maintaining the shape in the direction in which the interval of the slits 13 is not deformed without being deformed.

  As shown in FIG. 4, the movable electrode 18 is integrally connected to the functional unit 7. A fixed electrode 19 is formed at a position facing the movable electrode 18. The movable electrode 18 and the fixed electrode 19 constitute a drive electrode unit 20. Both the movable electrode 18 and the fixed electrode 19 are formed by processing the first substrate 10.

  The 1st base material 10 can be processed into the shape of the function part 7 and the drive electrode part 20 using methods, such as deep RIE. In addition, as shown in FIG. 2, the insulating layer 12 in a portion facing the functional unit 7 and the drive electrode unit 20 is removed by wet etching to form a space. Furthermore, in this Embodiment, as shown in FIG. 2, the 2nd base material 11 of the position facing the function part 7 is removed. Therefore, the insulating layer 12 and the second base material 11 do not exist at a position facing the functional unit 7.

  As shown in FIG. 4, movable electrodes 18 are provided on both sides of the functional unit 7 in the x direction. Each movable electrode 18 is formed in a rectangular shape having a predetermined length in the y direction. In addition, three fixed electrodes 19 are arranged on the both sides of each movable electrode 18 in the y direction, and three rows are arranged with a fine interval in the x direction.

  4 is an initial state (a state where driving power is not applied to the functional unit 7), and each movable electrode 18 is disposed so as to face the fixed electrode 19a provided closest to the functional unit 7. Has been. When a voltage is applied between the movable electrode 18 and the fixed electrode 19b farthest from the functional unit 7 from the state of the left figure in FIG. 4, the movable electrode 18 is attracted toward the fixed electrode 19b by electrostatic attraction. Then, as shown in the right diagram of FIG. 4, the movable electrode 18 moves to a position facing the fixed electrode 19b. At this time, the elastic portion 17 connecting the end portions of the filter pieces 14 is elastically deformed so as to extend in the lateral direction (x direction), and the interval between the slits 13 provided between the filter pieces 14 is It increases from T1 in the left figure of FIG. 4 to T2 in the right figure. Each filter piece 14 is supported via an elastic portion 17 so that the slit interval is equal between the filter pieces 14. For example, by forming the width of the elastic portion 17 so as to gradually decrease as the distance from the position close to the drive electrode portion 20 is changed, the elastic coefficient of the elastic portion 17 is made different so that the movable electrode 18 moves. Thus, the slit interval can be controlled to change while maintaining an equal interval.

  4 can be returned to the left diagram of FIG. 4 by applying a voltage between the movable electrode 18 and the fixed electrode 19a. In FIG. 4, the slit interval can be changed stepwise by selecting various fixed electrodes 19 that apply a voltage to the movable electrode 18 among the plurality of fixed electrodes 19.

  As shown in FIG. 2, the incident light L1 from the light source 2 (see FIG. 1) is reflected by the functional unit 7 of the optical filter 3 at a specific wavelength (reflected light L2), and the remaining light other than the reflected light L2 is reflected. The light is transmitted below the functional unit 7 (transmitted light L3). At this time, since the insulating layer 12 and the second base material 11 do not exist below the functional unit 7, light can be appropriately transmitted.

  By the way, in this Embodiment, the noble metal layer 15 is formed on the surface of each filter piece 14, and each filter piece 14 is movable in the horizontal direction (the planar direction of the 1st base material 10 and the 2nd base material 11). With this structure, it is possible to select light of a specific wavelength from a wide wavelength band and extract it as reflected light L2 according to the principle described below.

  Incident light (for example, white light) L <b> 1 shown in FIG. 2 is incident on a noble metal layer 15 (for example, a gold thin film) that covers the surface of each filter piece 14. The incident light L1 shown in FIG. 2 is a conceptual diagram, and the incident light L1 is actually applied to substantially the entire area of the functional unit 7. Since the gold thin film is thin, it has characteristics as a bulk of gold and physical properties peculiar to the surface due to a high proportion of the surface in the volume.

  The vibrations of a large number of conduction electrons contained in the gold bulk are due to longitudinal waves (coherent waves), and the quasiparticles obtained by quantizing the vibrations are called plasmons. The vibration of the incident light L1 is a transverse wave. For this reason, normally, the longitudinal wave plasmon and the transverse wave incident light L1 hardly react and do not exchange energy. However, when the incident light L1 has a specific wavelength light (frequency), the incident light L1 and plasmon may react on the gold surface to cause a resonance phenomenon. This is a phenomenon called so-called surface plasmon resonance. In this surface plasmon resonance, plasmons are induced by the energy given from the incident light L1, thereby generating surface waves (propagating surface plasmons). That is, the energy of the specific wavelength light included in the incident light L1 is converted into the energy of the surface wave, and the process of propagating on the gold thin film is realized.

  In the present embodiment, for example, when white light is used as incident light, the energy of a specific frequency component contained in white light is used as energy for plasmon induction, and other frequency components are It transmits without resonating with plasmons (transmitted light L3 shown in FIG. 2).

  The surface wave excited by being given energy by the incident light L1 propagates on the surface of the gold thin film. The propagating surface wave propagates not only to the surface of the filter piece 14 but also to the surfaces of the other filter pieces 14 facing each other through the slit 13. At this time, a part of the light existing in the slit 13 between the filter pieces 14 changes (rotates) in the propagation direction as shown in FIG. 8, and a part of the incident light L1 propagates to the incident surface side and is reflected by the reflected light L2. Become. In addition, the arrow shown in FIG. 8 represents the direction of the pointing vector which shows the propagation direction of the light in each point. The pointing vector is defined by the outer product of the electric and magnetic fields and indicates the density of the energy flow. The reflected light spectrum at this time is as shown in FIG. 9, and light having a frequency reflecting the propagating surface wave can be extracted.

  Here, with respect to the light existing between the slits 13, the wavelength that can stably exist varies depending on the size of the pitch p between the filter pieces 14. Specifically, as shown in FIG. 10, there was a correlation between the pitch P and the reflection wavelength. The substantially linear portion shown in FIG. 10 showed a higher reflectance than the other portions. Therefore, as shown in FIG. 10, it was found that the reflection wavelength increases in a substantially linear function as the pitch p increases. Further, as shown in FIG. 10, it was found that the reflected wavelength is slightly larger than the size of the pitch p.

  In the present embodiment, the slit interval is movable, but this also moves the size of the pitch p. As a result, in the present embodiment, it is possible to control the wavelength of the radiation light existing between the slits 13.

  Here, the phenomenon occurring between the slits 13 is briefly described. A part of the energy of the incident light L1 is used for the surface plasmon resonance, and a part of the surface wave generated by the surface plasmon resonance is slit. 13 is a process in which the propagation direction is changed between 13 and reflected.

  Of the light generated between the slits 13, there is light in a direction that reflects the incident light L <b> 1 via the functional unit 7, and the light is extracted as reflected light L <b> 2 having a specific wavelength. Although attention is paid to the gap between one slit 13 here, the same phenomenon occurs in the other slits 13.

  As described above, according to the optical filter 1 of the present embodiment, the incident light L <b> 1 is incident on the functional unit 7, so that the reflected light (wavelength selection light) having a wavelength that depends on the pitch p between the filter pieces 14. L2 can be taken out.

  In the above description, the case where the incident light L1 is continuously irradiated is described. However, not only the continuous irradiation but also a configuration in which irradiation and stop are repeated periodically or aperiodically may be employed. In the above, gold is used for the noble metal layer, but the same phenomenon can be caused even with noble metals other than gold. However, by forming the noble metal layer with gold, the surface plasmon resonance described above can be more appropriately generated, and the reflected light L2 having a specific wavelength can be more selectively extracted.

  In the optical filter 3 of the present embodiment, the slits 13 are inserted and divided into the filter pieces 14, and the filter pieces 14 can be controlled to move in the direction in which the slit interval varies. According to the configuration in which the optical filter 3 is formed using the SOI substrate 22 shown in FIG. 2, each filter piece 14 can be moved toward the planar direction of each base material 10, 11. With the configuration of this embodiment, the pull-in phenomenon and process restrictions can be suppressed as compared with the conventional case, and the movable range can be appropriately expanded as compared with the conventional Fabry-Perot filter in which the movable part moves in the film thickness direction. In the present embodiment, the pitch p between the filter pieces 14 can be moved within a range of 2 μm to 7 μm. As a result, as shown in FIG. 10, infrared rays having a wider wavelength band (about 3 μm to 8 μm) can be extracted as reflected light. Then, by incorporating the optical filter 3 of the present embodiment into the infrared analyzer 1, the infrared light having the absorption wavelength of each gas shown in FIG. 7 is selected as the reflected light L2 while changing the slit interval (pitch p). The gas concentration of each gas existing in a wide wavelength band can be detected appropriately.

  FIG. 5 is a plan view showing an example of the optical filter of the present embodiment. FIG. 5 is a schematic diagram, and in reality, the slits 13 positioned between the filter pieces 14 are formed at a narrower interval. Since each dimension was demonstrated using FIG. 3, please refer there.

  As shown in FIG. 5, a movable electrode 27 is integrally connected to a functional part 26 configured by a plurality of filter pieces 14 and an elastic part 25 that integrally connects adjacent filter pieces 14. . In addition, a noble metal layer is formed only on the surface of each filter piece 14, and no noble metal layer exists in other locations.

  As shown in FIG. 5, the movable electrode 27 is configured as a comb-like electrode in which a plurality of electrode teeth 28 are arranged at intervals. As shown in FIG. 5, the movable electrode 27 is connected to a frame body 29 provided around the functional portion 26 via an elastic portion (spring portion) 25. Further, the position on the opposite side of the movable electrode 27 of the elastic portion 25 that connects the end portions of the filter pieces 14 is integrally connected to the frame body 29. The elastic portion 25 that connects between the end portions of each filter piece 14 is configured as a tension spring, and the elastic portion 32 positioned between the movable electrode 27 and the frame 29 is configured as a compression spring.

  Further, as shown in FIG. 5, a fixed electrode 30 is provided on the inner surface of the frame body 29. The fixed electrode 30 is configured as a comb-like electrode in which a plurality of electrode teeth 31 are arranged at intervals. The electrode teeth 28 constituting the movable electrode 27 and the electrode teeth 31 constituting the fixed electrode 30 are alternately arranged.

  The functional unit 26, the frame 29, the movable electrode 27, and the fixed electrode 30 can be formed on the first base material 10 (see FIG. 2) of the SOI substrate 22.

  Thus, in FIG. 5, the drive electrode part for driving the function part 26 was comprised by the comb-tooth shaped electrode. By applying a voltage between the movable electrode 27 and the fixed electrode 30, electrostatic attraction can be generated. The magnitude of the electrostatic attractive force varies depending on the magnitude of the applied voltage. By increasing the applied voltage and the electrostatic attractive force, the movable electrode 27 moves to the right in the figure in FIG. And the overlapping area of the electrode teeth 31 of the fixed electrode 30 increases. At this time, as the drive electrode portion is driven, the elastic portion 25 is elastically deformed in the expanding direction, and the interval between the slits 13 of each filter piece 14 becomes larger than the state of FIG. As described above, the slit interval can be moved by the driving force of the driving electrode portion. As shown in FIG. 5, when there are three or more filter pieces 14 and there are a plurality of slits 13, each filter piece 14 is movably supported so that each slit 13 spreads while maintaining an equal interval. ing. For example, the width of the elastic portion 25 is gradually narrowed so that the elastic coefficient of the elastic portion 25 decreases as the distance from the drive electrode portion configured to include the movable electrode 27 and the fixed electrode 30 decreases. Thereby, when the function part 26 drives, the slit 13 between each filter piece 14 which comprises the function part 26 can be fluctuate | varied easily and appropriately at equal intervals.

  As shown in FIG. 5, by forming the movable electrode and the fixed electrode constituting the drive electrode unit with comb-like electrodes, the drive force of the drive electrode unit can be increased, and the slit interval of the functional unit 7 can be appropriately set within a wide movable range. Can be adjusted to be variable. Further, unlike the configuration of FIG. 4, the slit interval can be changed in an analog manner, and the accuracy of the filter function can be improved. Moreover, the problem which a pull-in phenomenon produces in the part of a drive electrode part can be suppressed appropriately by making a drive electrode part into a comb-tooth shaped electrode.

  FIG. 6 is a plan view showing an optical filter according to another embodiment different from FIG. In FIG. 6, the shape of the elastic portion (spring portion) 35 connected between the end portions of each filter piece 14 is different from that in FIG. 5.

  That is, in FIG. 6, the elastic portion 35 is bent while repeating a peak portion and a valley portion, and the extending direction of the elastic portion 35 is an oblique direction with respect to each filter piece 14.

  Also in FIG. 6, the drive electrode part for driving the function part 26 is comprised by the comb-like electrode similarly to FIG. By applying a voltage between the movable electrode 27 and the fixed electrode 30, the movable electrode 27 can be moved with respect to the fixed electrode 30, and at this time, the elastic portion 35 is elastically deformed in the expanding direction. The interval between the slits 13 of each filter piece 14 can be made larger than the state shown in FIG. Also in FIG. 6, as in FIG. 5, each filter piece 14 is movably supported so that the functional unit 26 is driven while maintaining the intervals of the plurality of slits 13 at equal intervals. For example, the width of the elastic portion 35 is gradually narrowed so that the elastic coefficient of the elastic portion 35 decreases as the distance from the drive electrode portion having the movable electrode 27 and the fixed electrode 30 decreases. Thereby, when the function part 26 drives, the slit 13 between each filter piece 14 which comprises the function part 26 can be fluctuate | varied easily and appropriately at equal intervals.

  5 and 6, the drive electrode unit is disposed only on one side of the functional unit 26. However, similarly to FIG. 4, the drive electrode unit composed of comb-like electrodes is disposed on both sides of the functional unit 26. You can also

  The optical filter 3 of the present embodiment is not limited to being incorporated in the infrared analysis device 1 shown in FIG. 1, and can be applied to other uses (for optical communication, for image display devices, etc.). Further, the optical filter 3 may be used for an application using the reflected light L2 having a specific wavelength shown in FIG. 2, or may be used for an application using the transmitted light L3 excluding the specific wavelength.

  According to the optical filter of the present invention, it is possible to broaden the wavelength band of light that can be extracted as reflected light by the optical filter as compared with the conventional case. For this reason, by incorporating the optical filter of the present invention into, for example, an infrared analyzer, the concentration of each gas can be appropriately detected even when the infrared absorption wavelength of each gas is over a wide wavelength band.

DESCRIPTION OF SYMBOLS 1 Infrared analyzer 2 Light source 3 Optical filter 4 Sample cell 5 Detector 6, 8 Mirror 7, 26 Function part 10 1st base material 11 2nd base material 13 Slit 14 Filter piece 15 Noble metal layers 17, 25, 32 , 35 Elastic part 18, 27 Movable electrode 19, 30 Fixed electrode 20 Drive electrode part 22 SOI substrate 28, 31 Electrode tooth 29 Frame

Claims (11)

Comprising a functional part having a filter piece divided into a plurality through a slit;
At least the surface of each filter piece is covered with a noble metal layer,
Each filter piece is supported so that a slit space | interval can be moved, The optical filter characterized by the above-mentioned.   The optical filter according to claim 1, further comprising a drive electrode portion for moving the slit interval.   The drive electrode unit includes a movable electrode and a fixed electrode, the movable electrode is connected to the functional unit, and the fixed electrode is provided at a position facing the movable electrode. The optical filter according to claim 2.   The optical filter according to claim 3, wherein each of the movable electrode and the fixed electrode is formed of a comb-like electrode having a plurality of electrode teeth.   The functional section includes the filter piece and an elastic portion that connects between ends of adjacent filter pieces, and the slit interval is movable by deformation of the elastic portion. The optical filter in any one of 4 thru | or 4.   6. The optical filter according to claim 1, wherein three or more filter pieces are provided, and the plurality of filter pieces are movable while maintaining an equal interval.   A first base material; a second base material; and an insulating layer provided between the first base material and the second base material, wherein the first base material is processed. The functional part is formed, the insulating layer facing the functional part is removed, and the functional part is parallel to the planar direction of the first base material and the second base material. 7. The optical filter according to claim 1, wherein the optical filter is supported so as to be movable in a direction.   The optical filter according to claim 7, wherein the insulating layer and the second base material are not provided at a position facing the functional unit.   9. The optical filter according to claim 1, wherein each filter piece includes a base material and the noble metal layer covering the periphery of the base material.   The optical filter according to claim 1, wherein the noble metal layer is formed of at least one selected from gold, palladium, and platinum.   The optical filter according to claim 1, wherein a pitch between the filter pieces is movable within a range of 2 μm to 7 μm.