JP2017173687A - Wavelength selection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength selection device capable of obtaining accurate wavelength selection characteristics corresponding to a control value.SOLUTION: A wavelength selection device comprises: a first filter F1 including a pair of reflection films provided on substrates facing each other and facing each other with a first optical distance; a control part changing the interval between the substrates facing each other according to the control value to change the first optical distance; a second filter F2 including a pair of reflection films facing each other with a second optical distance; a detection part 18 detecting an optical intensity of light passing through the first and second filters; and a calculation part calculating the selected wavelength of the first filter corresponding to the control value based on the control value and the optical intensity.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wavelength selection device having an optical filter.

  The optical filter is an optical element configured to selectively emit only light having a predetermined wavelength (wavelength band) from incident light, for example. For example, a wavelength selection element such as an optical filter has a configuration in which a pair of reflective films facing each other are arranged. The pair of reflective films are arranged in parallel with a gap, for example. Further, the interval between the reflective films is set according to the wavelength of light to be extracted. Patent Document 1 includes a wavelength variable interference filter, a detection unit that detects light transmitted through the filter, and a measurement unit that controls the filter and measures the intensity of light having a wavelength to be measured. A measuring device is disclosed.

JP 2012-93275 A

  The filtering characteristic (wavelength selection characteristic) of the optical filter is determined by the interval (optical gap) between the reflective films. The wavelength-tunable optical filter has a function of adjusting the filtering characteristics by adjusting the optical gap. In general, the reflection film of the wavelength tunable optical filter is formed on the movable part, and the reflection film is displaced by operating the movable part, thereby adjusting the filtering characteristics.

  On the other hand, in a wavelength tunable optical filter, the displacement amount of the design and the actual displacement amount may deviate due to the displacement of the movable part and the reflection film many times. In this case, for example, there is a problem that a desired filtering characteristic (extracted light) cannot be obtained even if a design control parameter is given to the movable part.

  The present invention has been made in view of the above points, and an object thereof is to provide a wavelength selection device capable of obtaining an accurate wavelength selection characteristic corresponding to a control value.

  According to the first aspect of the present invention, the first filter having a pair of reflective films which are provided on the substrates facing each other and are opposed to each other at a first optical distance, and the distance between the substrates facing each other is set as a control value. A control unit that changes the first optical distance by changing the second optical distance, a second filter having a pair of reflecting films facing each other at a second optical distance, and the first and second filters transmitted It has a detection part which detects the light intensity of light, and a calculation part which calculates the selection wavelength of the 1st filter corresponding to a control value based on a control value and light intensity.

(A) is sectional drawing of the wavelength selection apparatus which concerns on Example 1, (b) is a typical top view of the wavelength selection apparatus which concerns on Example 1. FIG. FIG. 3 is a diagram schematically illustrating an optical path in the wavelength selection device according to the first embodiment. (A) is a figure which shows the wavelength selection characteristic of the 1st filter of the wavelength selection apparatus which concerns on Example 1, (b) is a figure which shows the wavelength selection characteristic of a 2nd filter, (c) is a figure which shows the 1st filter. It is a figure which shows the intensity | strength of the light which permeate | transmitted the 1st and 2nd filter. 6 is a cross-sectional view of a wavelength selection device according to a first modification of the first embodiment. FIG. 6 is a sectional view of a wavelength selection device according to a second modification of the first embodiment. FIG. (A) And (b) is sectional drawing and the typical top view of the wavelength selection apparatus which concern on Example 2, respectively. (A) And (b) is sectional drawing and the typical top view of the wavelength selection apparatus which concern on the modification of Example 2, respectively.

  Examples of the present invention will be described in detail below.

  FIG. 1A is a schematic cross-sectional view of a wavelength selection device 10 according to the first embodiment. The wavelength selection device 10 is, for example, an optical filter. The wavelength selection device 10 is provided on the first and second substrates 11A and 11B facing each other, and the first and second reflective films 12A facing each other with an optical distance (first optical distance) DT1 and 12B. Specifically, as shown in FIG. 1A, first, the wavelength selection device 10 includes first and second main surfaces PL1 and PL2 that are opposed to each other with a gap GP therebetween. And second substrates 11A and 11B. In this specification, translucency refers to a property of transmitting at least a part of electromagnetic waves including light (visible light).

  In the present embodiment, the first and second substrates 11A and 11B have a flat plate shape. The first main surface PL1 is one of the main surfaces of the first substrate 11A. First reflective film 12A is formed on first main surface PL1.

  In the present embodiment, a columnar recess is provided at the center of one of the main surfaces of the second substrate 11B, and the bottom surface of the recess is the second main surface PL2. In the present embodiment, the second substrate 11B has a convex portion formed on the second main surface PL2. The second reflective film 12B is formed on the convex portion, and is disposed to face the first reflective film 12A with an optical distance (first optical distance) DT1. Note that the first and second substrates 11A and 11B are bonded to each other by the bonding portion BD outside the second main surface PL2.

  In the following, the entire first and second substrates 11A and 11B are the substrate pair 11, the entire first and second main surfaces PL1 and PL2 are the main surface pair PP, and the first and second substrates. The entirety of the reflective films 12A and 12B may be referred to as a reflective film pair 12.

  The first and second substrates 11A and 11B are made of, for example, quartz, borosilicate glass, silicon, or the like. The reflective film pair 12 has a resonator characteristic that selectively transmits electromagnetic waves. The reflective film pair 12 constitutes, for example, a Fabry-Perot etalon. The first and second reflective films 12A and 12B are thin films made of, for example, an alloy containing Ag and Ag, and are reflective films (reflective films) having transparency.

  The wavelength selection device 10 has a movable portion 13 whose bottom surface constitutes the first main surface PL1 and moves in a direction D perpendicular to the first main surface PL1. Further, the wavelength selection device 10 has a support portion 14 that is formed around the movable portion 13 on the first main surface PL1 and supports the movable portion 13 so as to be movable. The first reflective film 12A is formed on the movable portion 13. The first reflective film 12A is displaced in the direction D perpendicular to the first main surface PL1 according to the movement of the movable portion 13 (the optical distance DT1 increases or decreases). That is, the movable portion 13 is formed on the first main surface PL1, and displaces the first reflective film 12A in the direction D perpendicular to the first main surface PL1.

  In the present embodiment, the support portion 14 includes a thin film portion of the first substrate 11 </ b> A provided outside the movable portion 13. More specifically, a groove is provided on the main surface of the first substrate 11A opposite to the first main surface PL1, and the support portion 14 is compared with the first substrate 11A provided by the groove. Thin part. The inner portion of the support portion 14 in the first substrate 11A functions as a movable portion 13 that can be displaced. The surface (bottom surface) facing the second substrate 11B in the movable portion 13 and the support portion 14 constitutes the first main surface PL1.

  Further, the wavelength selection device 10 is formed on the first and second main surfaces PL1 and PL2, respectively, and is a driving unit including first and second electrodes 15A and 15B that generate electrostatic force that moves the movable unit 13. 15 The first and second electrodes 15A and 15B are made of a metal material such as Ag, Al, Cr, Ni, or Au, for example. In the present embodiment, the first and second electrodes 15A and 15B are film-like outside the first and second reflective films 12A and 12B on the first and second main surfaces PL1 and PL2, respectively. Is formed.

  In addition, the wavelength selection device 10 includes a control unit 16 that changes the distance between the first and second substrates 11A and 11B facing each other according to the control value and changes the optical distance DT1. In the present embodiment, the control unit 16 applies a voltage to the first and second electrodes 15A and 15B of the driving unit 15 and controls the voltage value. When a voltage is applied to the first and second electrodes 12A and 12B by the control unit 16, the movable unit 13 moves and the first reflective film 12A is displaced in a direction D perpendicular to the first main surface PL1. . That is, as the movable portion 13 moves, the optical distance (optical gap) DT1 of the reflective film pair 12 changes.

  In this embodiment, when a voltage is applied to the first and second electrodes 15A and 15B, for example, an electrostatic attractive force is generated between the first and second electrodes 15A and 15B. The support portion 14 is elastically deformed by this electrostatic attraction, and is bent (inclined) toward the second substrate 11B. Accordingly, the movable portion 13 moves toward the second substrate 11B. Thereby, for example, the distance between the first and second reflective films 12A and 12B is reduced. Depending on the voltage value to be applied, an electrostatic repulsive force can be generated between the first and second electrodes 15A and 15B, and the movable portion 13 can be moved in the direction in which the optical distance DT1 increases. Thus, the control unit 16 changes the optical distance DT1 of the reflective film pair 12 according to the voltage value (control value).

  The wavelength selection device 10 is formed on the main surface opposite to the second main surface PL2 of the second substrate 11B, and the second reflective film 12B with an optical distance (second optical distance) DT2. The third reflective film 17 is disposed so as to face the outer periphery of the first reflective film 17. In this embodiment, a groove is provided in a region facing the outer periphery of the second reflective film 12B on the back surface of the second substrate 11B, and a third reflective film 17 is formed at the bottom of the groove. The third reflective film 17 is a metal film made of the same material as the first and second reflective films 12A and 12B, for example.

  The wavelength selection device 10 includes a detection unit 18 that detects the light intensity of the light transmitted through the first, second, and third reflection films 12A, 12B, and 17. The detection unit 18 includes a light receiving unit RE that receives light transmitted through the first, second, and third reflective films 12A, 12B, and 17, and a measurement unit ME that measures the intensity of light incident on the light receiving unit RE. . The detection unit 18 includes, for example, a photo detector, an image sensor, and the like.

  Further, the wavelength selection device 10 determines the selection wavelengths of the first and second reflection films 12A and 12B corresponding to the voltage value (control value) applied by the control unit 16 based on the light intensity detected by the detection unit 18. A calculation unit 19 for calculating is provided. Specifically, the control unit 16 changes the voltage value and changes the optical distance DT1 of the reflective film pair 12. The detection unit 18 detects (measures) the intensity of light transmitted through the three first, second, and third reflective films 12A, 12B, and 17. Then, the calculation unit 18 calculates the control unit 16 and the selected wavelength of the reflection film pair 12 (the two reflection films 12A and 12B) based on the voltage value by the control unit 16 and the light intensity detected by the detection unit 18. Calculate the relationship.

  Further, the control unit 16 calibrates (corrects) the voltage value applied to the driving unit 15 based on the relationship (correlation) of the voltage value corresponding to the selected wavelength of the reflective film pair 12 calculated by the calculation unit 19.

  FIG. 1B is a schematic top view of the wavelength selection device 10. 1A is a cross-sectional view taken along the line VV in FIG. In this embodiment, as shown in FIG. 1B, first, the substrate pair 11 has a rectangular shape when viewed from above, that is, when viewed from the direction D perpendicular to the first and second main surfaces PL1 and PL2. Has a shape. The reflective film pair 12 (the shape of the first reflective film 12A is shown in FIG. 1B) has a circular shape when viewed from above. The movable part 13 has a cylindrical shape in a top view. The support part 14 is formed in an annular shape so as to surround the outer periphery of the movable part 13 in a top view.

  As shown in FIG. 1B, in the present embodiment, the third reflective film 17 is formed in an annular shape so as to face the outer peripheral portion of the second reflective film 12B. For clarity of illustration, the region of the third reflective film 17 is hatched in FIG. Although not shown, in the present embodiment, the light receiving unit RE of the detection unit 18 has a light receiving surface corresponding to the shape of the third reflective film 17, and the light receiving surface is the third reflective film 17. It is arranged to face.

  In the present embodiment, the first and second reflection films 12A and 12B, the movable portion 13, the support portion 14, and the third reflection film 17 are formed rotationally symmetrically about one point in a top view. ing.

  FIG. 2 is a diagram schematically illustrating a path of light incident on the wavelength selection device 10. The configuration of the wavelength selection device 10 and the filtering operation will be described with reference to FIG. 2 is a cross-sectional view similar to FIG. 1A, but hatching is omitted.

  First, the first reflection film 12A and the second reflection film 12B constitute a wavelength-tunable first optical filter (hereinafter referred to as a first filter) F1 that determines the wavelength selection characteristics of the wavelength selection device 10. . Next, the second reflective film 12B and the third reflective film 17 are fixed wavelength type second calibrations for calibrating the voltage value by the control unit 16 and the selection wavelength (wavelength selection characteristic) of the first filter F1. 2 optical filters (hereinafter referred to as second filters) F2.

  In other words, the wavelength selection device 10 is provided on the substrates 11A and 11B facing each other, and has a first filter F1 having a pair of reflection films 12A and 12B facing each other with a first optical distance DT1. A control unit 16 that changes the first optical distance DT1 by changing the distance between the substrates 11A and 11B according to the control value, and a pair of reflective films 12B and 17 that face each other at the second optical distance DT2. And a second filter F2.

  Further, the detection unit 18 detects the light intensity of the light transmitted through the first and second filters F1 and F2, and the calculation unit 19 corresponds to the control value based on the light intensity and the control value. The selection wavelength of one filter F1 is calculated. Further, the control unit 16 changes the first optical distance DT1 based on the relationship between the control value calculated by the calculation unit 19 and the selection wavelength of the first filter F1.

  Next, the outline of the wavelength selection operation of the wavelength selection device 10 and the detection operation by the detection unit 18 will be described with reference to FIG. First, in the present embodiment, the wavelength selection device 10 allows the input light IL incident from the first reflective film 12A side to be extracted from the second reflective film 12B as selective light (first selective light) SL1. It is configured. First, the input light IL enters the wavelength selection device 10 through the first substrate 11A. The input light IL repeats multiple reflections between the first and second reflective films 12A and 12B. At this time, in the input light IL, light having a wavelength corresponding to the optical distance DT1 between the first and second reflective films 12A and 12B remains, and light having other wavelengths is attenuated. The remaining wavelength light passes through the second reflective film 12B as the selection light SL1. The selection light SL1 passes through the second reflective film 12B and then exits from the second substrate 11B. In this way, the wavelength selection device 10 selectively outputs (transmits) incident light (electromagnetic wave).

  Next, in the selection light (first selection light) SL1, the light (selection light SL11) incident on the third reflection film 17 (second filter F2) is the second and third reflection films 12B. And 17 perform the second filtering. Of the selection light SL11 incident on the second filter F2, light having a wavelength corresponding to the optical distance DT2 between the second and third reflection films 12B and 17 remains, and the selection light (from the third reflection film 17 ( (Second selection light) SL2 is extracted. The selection light SL2 transmitted through the first and second filters F1 and F2 is received by the light receiving unit RE of the detection unit 18, and the light intensity is measured (detected).

  FIG. 3A is a diagram illustrating the wavelength selection characteristics of the first filter F1. FIG. 3A is a spectrum diagram of the selection light SL1 of the first filter F1 having a predetermined optical distance DT1. As shown in FIG. 3A, the first filter F1 is configured to selectively extract light having a specific wavelength (about 680 nm in this embodiment) corresponding to the optical distance DT1. In the present embodiment, for example, the optical distance DT1 of the first filter F1 is set to a distance comparable to the variable wavelength range in consideration of the design input light IL and the selection light SL1.

  FIG. 3B is a diagram illustrating the wavelength selection characteristics of the second filter F2. In the present embodiment, the optical distance DT2 of the second filter F2 is a fixed optical distance that is larger than the maximum variable distance of the optical distance DT1 of the first filter F1. In the present embodiment, the second filter F2 includes the reflective films 12B and 17 at an optical distance DT2 that is sufficient (for example, 10 times or more) with respect to the selection light SL1 of the first filter F1. . That is, the optical distance DT2 of the second filter F2 is determined so that the light intensity of the selection light SL2 has a plurality of maximum points.

  Accordingly, as shown in FIG. 3 (b), the first filter F1 extracts light of almost one wavelength band, whereas the second filter F2 is configured to extract light of a plurality of wavelength bands. ing.

  FIG. 3C is a spectrum diagram of light transmitted through the first and second filters F1 and F2 at a predetermined optical distance DT1. When the selected wavelength of the second filter F2 is an integral multiple of the selected wavelength of the first filter F1, as shown in FIG. 3C, the light is strengthened in the first and second filters F1 and F2. Therefore, the light of the predetermined wavelength is extracted with high intensity. On the other hand, when the selected wavelength of the second filter F2 is not an integral multiple of the selected wavelength of the first filter F1, most of the light selected by the first filter F1 is attenuated in the second filter F2. Therefore, the intensity of the selection light SL2 is small.

  The calculation unit 19 uses a known wavelength selection characteristic of the second filter F2 to obtain a difference between the selection wavelength of the first filter F1 and the voltage value (control value) that the control unit 16 gives to the drive unit 15. Calculate (derived) the actual relationship. Specifically, the calculation unit 19 calculates the selection wavelength of the first filter F1 corresponding to the control value based on the control value when the light intensity of the selection light SL2 becomes maximum.

  Further, by gradually changing the optical distance DT1 by the control unit 16, the detection unit 18 detects the maximum point of the light intensity a plurality of times. The calculation unit 19 stores a plurality of control values when the light intensity of the selection light SL2 reaches a maximum, and calculates the selection wavelength of the first filter F1 corresponding to the plurality of control values. Thereby, the calculation accuracy of the applied voltage value and the selected wavelength of the first filter F1 is improved.

  In addition, the calculation part 19 estimates the selection wavelength of the 1st filter F1 corresponding to the said control value about the control value between several control values when light intensity becomes the maximum point. For example, based on a plurality of voltage values when the light intensity maximum point is detected by the detection unit 18, the calculation unit 19 uses the first filter F1 in the voltage value region when the light intensity between them is small. Complements the selected wavelength.

  Specifically, for example, the calculation unit 19 plots the relationship between the voltage value when the intensity of the selection light SL2 is maximized and the selection wavelength of the first filter F1 on a graph, and displays the plotted point. Perform polynomial approximation so that it always passes. Then, the calculation unit 19 derives a curve that connects the plotted points, and calculates the selection wavelength of the first filter F1 according to the change in the voltage value of the control unit 16. The control unit 16 calibrates the control value based on the correlation between the control value calculated by the calculation unit 19 and the selected wavelength.

  In this embodiment, the case where the control unit 16 changes the first optical distance DT1 according to the voltage value has been described. However, the control unit 16 changes a physical parameter using an actuator, for example. The first optical distance DT1 only needs to be changed according to various control values.

  Moreover, although the case where the drive unit 15 changes the first optical distance DT1 by electrostatic force has been described, the configuration of the drive unit 15 is not limited to this, and for example, the first optical distance DT1 is changed electromagnetically. It may be configured. In the present embodiment, the case where the second reflective film 12B of the first filter F1 constitutes one reflective film of the second filter F2 has been described, but the second filter F2 is the first filter. You may have a pair of reflective film different from F1.

  In the present embodiment, the case where the control unit 16 corrects the control value based on the calculation result of the calculation unit 19 has been described. However, the control unit 16 does not need to correct the control value. It suffices that the calculation unit 19 calculates an exact correspondence between the control value and the transmission wavelength. In addition, the case where the second filter F2 is a fixed wavelength type optical filter (the second optical distance DT2 is fixed) has been described. However, the second filter F2 is a known calibration master. What is necessary is just to have a wavelength selection characteristic.

  FIG. 4 is a cross-sectional view of the wavelength selection device 10A according to the first modification of the first embodiment. In the wavelength selection apparatus 10, the case where the third reflective film 17 is provided on the second substrate 11B and the second filter F2 is configured in a pair with the second reflective film 12B has been described. On the other hand, in the present modification, the wavelength selection device 10A includes a third filter 17A formed at a position facing the first reflective film 12A of the first substrate 11A. That is, the third reflective film 17A and the first reflective film 12A may be paired to constitute the second filter F2.

  In this modification, the wavelength selection device 10A is provided with a detection unit 18A on the first substrate 11A side. The wavelength selection device 10A is configured to allow light to enter from the second substrate 11B (second reflection film 12B) and to extract the selection light to the first substrate 11A side. Also in this modification, the detection unit 18A detects the intensity of light transmitted through the second, first, and third reflective films 12B, 12A, and 17A.

  As in this modification, the first reflective film 12A may constitute one reflective film of the second filter F2. Also in this configuration, the first filter is formed using the second filter F2 by making the wavelength selection characteristics of the second filter F2 configured by the first and third reflective films 12A and 17A known. Calculation of the selection wavelength of F1 and correction of the control value can be performed.

  Further, as in the wavelength selection devices 10 and 10A, any one of the reflection films 12A and 12B of the first filter F1 constitutes one reflection film in the second filter F2, thereby reducing the size of the device. be able to.

  FIG. 5 is a schematic cross-sectional view illustrating a configuration of a wavelength selection device 10B according to the second modification of the first embodiment. In this modification, the wavelength selection device 10B has the same configuration as the wavelength selection device 10 or 10A except for the configuration of the second filter F3. The second filter F3 includes third and fourth reflective films 17B1 and 17B2 provided separately from the first and second reflective films 12A and 12B.

  Specifically, the wavelength selection device 10B includes a second filter F3 that enters the selection light SL1 reflected by the reflection mirror ML and extracts the selection light SL2. The second filter F3 includes a translucent substrate SB and third and fourth reflective films 17B1 and 17B2 that are formed on the translucent substrate SB and arranged to face each other with an optical distance. The detector 18 detects the light intensity of the selection light SL2 extracted from the second filter F3.

  As shown in this modification, the first and second filters F1 and F3 may have different reflective film pairs. Also in this modification, the first filter is used by using the second filter F3 by making the wavelength selection characteristics of the second filter F3 configured by the third and fourth reflection films 17B1 and 17B2 known. Calculation of the selected wavelength of the filter F1 and correction of the control value can be performed.

  In this embodiment and its modification, the wavelength selection device 10 includes a first filter F1 that performs wavelength selection at the first optical distance DT1, and a control unit that changes the first optical distance DT1 according to the control value. 16, a second filter F2 that performs wavelength selection at the second optical distance DT2, a detection unit 18 that detects the light intensity of the light SL2 that has passed through the first and second filters F1 and F2, and the control value And a calculation unit 19 that calculates a selection wavelength of the first filter F1 corresponding to the control value based on the light intensity.

  Therefore, the control unit 16 analyzes and compares the relationship with the change in the selected wavelength of the first filter F1 corresponding to the change in the control value given to the drive unit 15 in order to change the first optical distance DT1, and the accurate The relationship between the two can be calculated. Therefore, for example, even when the relationship between the control value and the filtering characteristic is shifted over time, an accurate filtering operation can be performed by correcting or grasping the shift. Therefore, it is possible to obtain an accurate wavelength selection characteristic corresponding to the control value.

  FIG. 6A is a schematic cross-sectional view of the wavelength selection device 20 according to the second embodiment. FIG. 6B is a schematic top view of the wavelength selection device 20. FIG. 6A is a cross-sectional view taken along the line W-W in FIG. The wavelength selection device 20 has the same configuration as the wavelength selection device 10 except for the configuration of the third reflective film 21 and the detection unit 22.

  As shown in FIGS. 6A and 6B, the third reflective film 21 of the wavelength selection device 20 has a plurality of reflective film pieces 21A. In the present embodiment, each of the reflective film pieces 21A is opposed to the outer peripheral portion of the second reflective film 12B and is disposed apart from each other. Also in the present embodiment, like the first embodiment, the third reflective film 22 constitutes a second filter F2 (see FIG. 2) together with the second reflective film 12B. In addition, the light receiving unit of the detection unit 22 includes a light receiving region RE1 disposed to face each reflective film piece 21A.

  In the present embodiment, the detection unit 22 detects the light intensity of the selection light SL2 at a plurality of locations (for example, each of the reflection film pieces 21A) of the second filter F2. Thus, for example, by detecting the distribution of the filtering characteristics in the first filter F1 (for example, the difference in the film of the first optical distance DT1), for example, the inclination of the first reflective film 12A can be detected.

  For example, when the light intensity of the selection light SL2 transmitted through each of the reflection film pieces 21A is different, the calculation unit 19 determines that the selection wavelength of the first filter F1 varies depending on the location, and performs a calculation operation in consideration of this. Do. For example, when most of the light intensities at a plurality of locations have the same light intensity, the calculation unit 19 may calculate the selection wavelength of the first filter F1 based on the light intensity of this portion.

  FIG. 7A is a schematic cross-sectional view of a wavelength selection device 20A according to a modification of the second embodiment. FIG. 7B is a schematic top view of the wavelength selection device 20A. FIG. 7A is a cross-sectional view taken along line XX in FIG. The wavelength selection device 20 </ b> A has the same configuration as the wavelength selection device 20 except for the configuration of the third reflective film 23 and the detection unit 24.

  As shown in FIGS. 7A and 7B, the third reflective film 23 of the wavelength selection device 20A includes a plurality of first reflective film pieces 23A facing the outer periphery of the second reflective film 12B, A second reflective film piece 23B facing the center of the second reflective film 12B. The light receiving unit of the detection unit 24 includes a first light receiving region RES that faces the first reflective film piece 22A and a second light receiving region REC that faces the second reflective film piece 22B.

  In the present modification, the third reflective film 23 includes the first reflective film piece 23A corresponding to the reflective film piece 21A, and the second reflective film piece 23B facing the central portion of the second reflective film 12B. Have The detection unit 24 includes light receiving regions RES and REC corresponding to the reflective film pieces 23A and 23B.

  In the present modification, the detection unit 24 detects the difference in light intensity between the central part and the outer peripheral part (peripheral part) of the first filter F1, for example, the first substrate 11A or the first The warp of the reflective film 12A can be detected. In this case, the calculation unit 19 may perform the calculation operation in consideration of, for example, the light intensity of the central portion (first reflective film piece 23B) of the first filter F1. For example, when it is detected and calculated that the first substrate 11A is warped (bent) during operation, adjustment can be easily performed based on this result.

  In the present embodiment, the detection units 22 and 24 detect the light intensity of the selection light SL2 at a plurality of locations of the first filter F1 (first and second reflection films 12A and 12B). Therefore, a detailed calculation operation can be performed by the calculation unit 19, and an accurate wavelength selection characteristic corresponding to the control value can be obtained. For example, even when the first reflective film 12A is inclined or bent over time, the inclination and the like can be easily and quickly grasped. Further, by devising the calculation method of the calculation unit 19, the control unit 16 can accurately control the first optical distance DT1, that is, the filtering characteristic of the first filter F1.

10, 10A, 10B, 20, 20A Wavelength selection device F1 First optical filter F2 Second optical filter 16 Control unit 12A First reflective film 12B Second reflective film 17, 17A, 17B1, 2, 23 Reflective film 18 Detection unit 19 Calculation unit

Claims (7)

A first filter provided on a substrate facing each other and having a pair of reflective films facing each other at a first optical distance;
A control unit that changes the first optical distance by changing an interval between the opposing substrates according to a control value;
A second filter having a pair of reflective films facing each other at a second optical distance;
A detector for detecting the light intensity of the light transmitted through the first and second filters;
A wavelength selection device comprising: a calculation unit that calculates a selection wavelength of the first filter corresponding to the control value based on the control value and the light intensity.   2. The wavelength selection device according to claim 1, wherein one reflection film of the pair of reflection films of the first filter constitutes one of the pair of reflection films of the second filter. .   3. The calculation unit according to claim 1, wherein the calculation unit calculates a selection wavelength of the first filter corresponding to the control value based on the control value when the light intensity reaches a maximum. The wavelength selection apparatus as described.   4. The wavelength selection apparatus according to claim 1, wherein the second optical distance is a fixed optical distance that is larger than a maximum variable distance of the first optical distance. 5. The second optical distance is determined so that the light intensity has a plurality of maximum points,
The calculation unit stores a plurality of control values when the light intensity reaches a maximum, calculates a selection wavelength of the first filter corresponding to the plurality of control values, and calculates the plurality of control values. The wavelength selection apparatus according to claim 4, wherein a selected wavelength of the first filter corresponding to the control value is estimated for a control value between.   The said detection part detects the light intensity of the light which permeate | transmitted the said 1st and 2nd filter in the several location of the said 1st filter, The any one of Claim 1 thru | or 5 characterized by the above-mentioned. The wavelength selection apparatus as described.   7. The control unit according to claim 1, wherein the control unit changes the first optical distance based on a relationship between the control value calculated by the calculation unit and a selection wavelength of the first filter. The wavelength selection apparatus as described in any one.

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