JP2018155950A - Optical module and method for driving optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module capable of outputting light in a wide wavelength range, and a method for driving an optical module.SOLUTION: The optical module includes: a wavelength variable interference filter that includes a movable part having a first reflection film and a second reflection film opposing to the first reflection film, a holding part holding the movable part as displaceable, and an electrostatic actuator for displacing the movable part to the first reflection film side in response to voltage application; a light-receiving part that receives outgoing light from the wavelength variable interference filter to output a light-reception signal; a voltage control part that controls voltage application to the electrostatic actuator; and a signal acquiring part that acquires the light-reception signal from the light-receiving part. The voltage control part applies a voltage to the electrostatic actuator to displace the movable part to the first reflection film side, then dropping the voltage to displace the movable part to a position where a gap dimension is greater than the initial gap. The signal acquiring part acquires a light-reception signal from the light-receiving part when the movable part is located at the position where the gap dimension is greater than the initial gap.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an optical module and a method for driving the optical module.

2. Description of the Related Art Conventionally, an optical module including a wavelength variable filter that outputs light having a predetermined wavelength from incident light is known (see, for example, Patent Document 1).
The optical module described in Patent Document 1 includes a pair of reflective films facing each other and an electrostatic actuator that changes the dimension between the pair of reflective films. In such an optical module, the dimension between the reflective films can be changed and the wavelength of light transmitted through the wavelength tunable interference filter can be changed by an electrostatic actuator having a simple configuration in which a pair of electrodes are opposed to each other. Is possible.

Japanese Patent No. 5556002

  By the way, in an electrostatic actuator, the dimension between electrodes is changed by electrostatic attraction. For this reason, in the wavelength variable interference filter described in Patent Document 1, the dimension between the reflective films can be narrowed from the initial dimension by the electrostatic actuator, but cannot be widened. For this reason, there is a problem that light having a wavelength longer than the wavelength corresponding to the initial dimension cannot be output from the wavelength variable interference filter, and the wavelength range of light that can be output from the optical module is narrow.

  An object of the present invention is to provide an optical module capable of outputting light having a wide range of wavelengths, and a method for driving the optical module.

  An optical module according to an application example of the invention includes a first reflective film, a movable part including a second reflective film facing the first reflective film, and the movable part can be displaced in a film thickness direction of the second reflective film. A wavelength tunable interference filter comprising: a holding part that holds the light source; and an electrostatic actuator that displaces the movable part toward the first reflecting film side by applying a voltage; and receiving light emitted from the wavelength tunable interference filter. A light receiving unit that outputs a light reception signal; a voltage control unit that controls the voltage applied to the electrostatic actuator; and a signal acquisition unit that acquires the light reception signal from the light receiving unit. When the voltage is not applied, a gap dimension between the first reflective film and the second reflective film is set as an initial gap, and the voltage control unit applies the voltage to the electrostatic actuator. After displacing the movable part toward the first reflective film side, the voltage is dropped to displace the movable part to a position where the gap dimension is larger than the initial gap, and the signal acquisition unit The light reception signal from the light receiving unit when the movable unit is positioned at a position where the dimension is larger than the initial gap is obtained.

  In this application example, the optical module applies a voltage to the electrostatic actuator by the voltage control unit to displace the movable unit toward the first reflective film, and then drops the voltage. Thereby, the movable part returns toward the initial position (position where the reflection film becomes the initial gap) by the spring force of the holding part, and the gap dimension between the reflection films becomes larger than the initial gap by the restoring force. The signal acquisition unit acquires the light reception signal from the light reception unit at the timing when the gap dimension becomes larger than the initial gap. As a result, the optical module can acquire the received light amount of light having a wavelength corresponding to the gap between the reflective films that is larger than the initial gap, so that the received light amount for each light in a wide wavelength range (scanning range) is measured. can do.

In the optical module of this application example, it is preferable that the voltage control unit lowers the voltage by changing the voltage in a step waveform.
In this application example, the voltage control unit changes the voltage applied to the electrostatic actuator in a step waveform when the gap between the reflective films is set to a gap larger than the initial gap. Thereby, compared with the case where the voltage applied to an electrostatic actuator is decreased gradually, a voltage will change rapidly and the restoring force which displaces a movable part toward an initial gap also becomes large. Therefore, the movable part can be largely displaced beyond the initial gap by the restoring force, and the wavelength of light that can be transmitted by the wavelength variable interference filter can be widened. That is, in the optical module, it is possible to widen the wavelength range of light that can be measured.

In the optical module of this application example, it is preferable that a housing for storing the variable wavelength interference filter is provided, and the inside of the housing is maintained under reduced pressure.
In this application example, the variable wavelength interference filter is housed in a housing maintained under reduced pressure. For this reason, the air resistance when the movable part is displaced is also reduced, and the amount of displacement when the movable part is displaced toward the initial position by the restoring force can be increased.

In the optical module according to this application example, the voltage control unit may output the voltage so that the gap dimension reaches a target value corresponding to a target wavelength when the movable unit is displaced due to the voltage drop. It is preferable to apply to the actuator.
In this application example, the voltage control unit applies a voltage at which the gap dimension reaches a target value corresponding to the target wavelength when the movable unit is displaced beyond the initial gap by the restoring force, Descent. Accordingly, since the movable unit reaches the target value, the signal acquisition unit can acquire the amount of light received at the target wavelength by acquiring the amount of light received when the movable unit reaches the target value.

In the optical module according to this application example, the voltage control unit may be configured such that an interelectrode gap dimension, which is a gap dimension between a pair of electrodes constituting the electrostatic actuator, does not apply a voltage to the pair of electrodes. It is preferable to drop the voltage after applying the voltage for displacing the movable part to a position that is 2/3 or less of the gap between the initial electrodes, which is the gap dimension.
In this application example, the voltage is dropped after the movable portion is displaced to a position where the interelectrode gap dimension is 2/3 or less of the initial interelectrode gap. Thereby, a movable part can be displaced to the position where a gap dimension becomes more than an initial gap by restoring force.

In the optical module according to this application example, the variable wavelength interference filter includes a stopper that suppresses displacement of the movable portion toward the first reflective film when the gap dimension reaches a predetermined first gap dimension. It is preferable.
Here, as a 1st gap dimension, when a voltage drop is carried out, the dimension in which a movable part reaches | attains a target value can be illustrated.
In this application example, the voltage applied to the electrostatic actuator is lowered from the state in which the displacement of the movable portion is suppressed by the stopper, so that the gap between the reflective films can be easily made larger than the initial gap. Further, in the electrostatic actuator, when the distance between the electrodes is small, the gap control becomes difficult. In contrast, in the configuration in which the stopper is provided, the displacement of the movable portion is suppressed by the stopper when a voltage of a predetermined value or more is applied to the electrostatic actuator. Therefore, it is easy to control the voltage of the electrostatic actuator when the movable part is displaced to a position having a gap size larger than the initial gap.

In the optical module of this application example, it is preferable that the signal acquisition unit acquires the light reception signal at a predetermined time interval after the voltage is dropped.
In this application example, the signal acquisition unit acquires the light reception signal at predetermined time intervals after the voltage drop. In this case, by measuring in advance the position of the movable part every predetermined time after the voltage drop, it is possible to measure the amount of received light with respect to light having a wavelength corresponding to each position (gap size). Further, in addition to the light reception signal at a predetermined time interval, it is also possible to calculate a spectral spectrum by detecting the gap size between the reflective films at the time interval. In this case, the light quantity with respect to the target wavelength can be calculated based on the calculated spectral spectrum.

The optical module according to this application example includes a gap detection unit that detects the gap size, and the signal acquisition unit receives the light when the gap size detected by the gap detection unit reaches a predetermined target value. It is preferable to acquire a signal.
In this application example, a gap size is detected by the gap detection unit, and a light reception signal is acquired when the gap size reaches a target value. Thereby, the amount of received light with respect to a desired target wavelength can be detected.

  An optical module driving method according to an application example of the invention includes a first reflective film, a movable part including a second reflective film facing the first reflective film, and the movable part in a film thickness direction of the second reflective film. A tunable interference filter having a holding portion that is displaceably held, and an electrostatic actuator that displaces the movable portion toward the first reflecting film side by applying a voltage, and the wavelength tunable interference filter. A light receiving unit that receives light and outputs a light reception signal, wherein the first reflection film and the second reflection film are applied when the voltage is not applied to the electrostatic actuator. A gap between the first step, applying the voltage to the electrostatic actuator to displace the movable part to the first reflective film side; A third step of acquiring the light reception signal from the light receiving portion when the movable portion is displaced to a position where the gap dimension is larger than the initial gap in the second step of dropping the voltage and the second step; And performing the steps.

  In this application example, in the first step, a voltage is applied to the electrostatic actuator to displace the movable part to the first reflecting film side, the voltage is lowered in the second step, and the gap size is changed from the initial gap in the third step. The light reception signal when the movable part is displaced to the position where the distance becomes larger is acquired. Therefore, as in the above application example, the amount of light received through the wavelength variable interference filter when the gap between the reflecting films is larger than the initial gap due to the spring force (restoring force) of the holding part is the movable part. That is, the amount of light received for each light in a wide wavelength range can be measured.

1 is a block diagram showing a schematic configuration of an optical device according to a first embodiment. The top view which shows schematic structure of the wavelength variable interference filter of 1st embodiment. 1 is a cross-sectional view showing a schematic configuration of a variable wavelength interference filter according to a first embodiment. 6 is a flowchart illustrating a method for driving the optical device according to the first embodiment. The figure which shows the voltage waveform of the voltage applied to an electrostatic actuator in 1st embodiment. The relationship between the elapsed time and the gap between the reflection films of the wavelength tunable interference filter in the optical device driving method of the first embodiment, and the relationship between the elapsed time and the wavelength of light that passes through the wavelength tunable interference filter (transmission wavelength λ). FIG. Schematic which shows the wavelength variable interference filter at the time of moving a movable part in a 1st step. Schematic which shows the wavelength variable interference filter at the time of displacing a movable part in a 2nd step. Sectional drawing which shows schematic structure of the wavelength variable interference filter of 2nd embodiment. FIG. 10 is a cross-sectional view of the wavelength tunable interference filter when the movable part is displaced toward the fixed substrate in FIG. 9. 10 is a flowchart illustrating a method for driving the optical device according to the third embodiment. The flowchart which shows the drive method of the optical apparatus of 4th embodiment.

[First embodiment]
Hereinafter, a first embodiment according to the present invention will be described with reference to the drawings.
[Configuration of optical device]
FIG. 1 is a block diagram showing a schematic configuration of the optical device according to the first embodiment of the present invention.
The optical device 1 is an example of an optical module, and is a device that measures the amount of light of each wavelength in the measurement target light reflected by the measurement target X, for example. In the present embodiment, an example of measuring the measurement target light reflected by the measurement target X is shown. However, when a light emitter such as a liquid crystal panel is used as the measurement target X, the light emitted from the light emitter is used. May be measured light.
As shown in FIG. 1, the optical apparatus 1 includes an optical filter device 10, a light receiving unit 11, a signal processing circuit 12, a filter driving circuit 13, a gap detection circuit 14 (gap detection unit), and a control. Part 20.

The light receiving unit 11 receives light transmitted through the wavelength variable interference filter 5 and outputs a light reception signal (current) corresponding to the light intensity (light quantity) of the received light.
The signal processing circuit 12 includes, for example, an IV converter, an amplifier, an A / D converter, and the like. The signal processing circuit 12 converts the received light signal input from the light receiving unit 11 by the IV converter into a voltage signal, amplifies the converted voltage signal by an amplifier, and converts the amplified signal into a digital signal. To the control unit 20.

The filter drive circuit 13 applies a voltage to an electrostatic actuator 56 (to be described later) of the wavelength variable interference filter 5 based on the control of the control unit 20.
The gap detection circuit 14 detects a gap between reflective films 54 and 55 (see FIGS. 2 and 3) described later of the wavelength variable interference filter 5 and outputs the detected gap to the control unit 20.

[Configuration of optical filter device]
As shown in FIG. 1, the optical filter device 10 includes a housing 101 and a wavelength variable interference filter 5 housed in the housing 101.
The casing 101 is a box-shaped member that houses the variable wavelength interference filter 5, and the internal space is maintained under reduced pressure (for example, vacuum).
The casing 101 includes an incident window 102 for allowing the measurement light to enter the casing 101 on the optical axis of the measurement light from the measurement object X, and an exit window for allowing the light transmitted through the wavelength variable interference filter 5 to pass therethrough. 103. These entrance window 102 and exit window 103 are closed by a transparent member such as glass.

[Configuration of wavelength tunable interference filter]
Next, the wavelength variable interference filter 5 housed in the housing 101 of the optical filter device 10 will be described.
FIG. 2 is a plan view showing a schematic configuration of the variable wavelength interference filter 5. FIG. 3 is a cross-sectional view showing a schematic configuration of the wavelength variable interference filter 5 obtained by cutting FIG. 2 along the line AA.
As shown in FIG. 2, the wavelength variable interference filter 5 is a rectangular plate-shaped optical member, for example. The variable wavelength interference filter 5 includes, for example, a fixed substrate 51 and a movable substrate 52 as shown in FIG. The fixed substrate 51 and the movable substrate 52 are integrally formed by bonding with a bonding film 53 such as a plasma polymerization film mainly containing siloxane.
The fixed substrate 51 is provided with a fixed reflective film 54 that constitutes a first reflective film, and the movable substrate 52 is provided with a movable reflective film 55 that constitutes a second reflective film. The reflection film 55 is disposed so as to face the gap Gm between the reflection films. Further, the wavelength variable interference filter 5 includes an electrostatic actuator 56 (shaded portion shown in FIG. 2) that changes the gap dimension of the gap Gm between the reflection films.
Hereinafter, the configuration of each unit will be described in detail.

(Configuration of fixed substrate)
The fixed substrate 51 includes an electrode arrangement groove 511 and a reflective film installation part 512 formed by etching, for example, on the surface facing the movable substrate 52. The fixed substrate 51 is formed to have a thickness that is larger than that of the movable substrate 52, for example, and the fixed substrate 51 when the electrostatic attractive force is applied by the electrostatic actuator 56 is suppressed. Further, one end side of the fixed substrate 51 (for example, the side C5-C6 in FIG. 2 protrudes from one end side (side C1-C2) of the movable substrate 52.

The electrode arrangement groove 511 is formed in a substantially annular shape centered on a predetermined filter center point O in a plan view (hereinafter simply referred to as a plan view) when the fixed substrate 51 is viewed from the substrate thickness direction. The reflection film installation part 512 is formed so as to protrude from the central part of the electrode arrangement groove 511 toward the movable substrate 52 in a plan view. A fixed electrode 561 constituting the electrostatic actuator 56 is arranged on the groove bottom surface of the electrode arrangement groove 511, and a fixed reflective film 54 is arranged on the protruding front end surface of the reflective film installation portion 512.
Further, the fixed substrate 51 is provided with an electrode extraction groove (not shown) extending from the electrode arrangement groove 511 toward the side C3-C4.

The fixed electrode 561 is provided in a region of the groove bottom surface of the electrode arrangement groove 511 facing a movable electrode 562 of the movable portion 521 described later. The fixed electrode 561 is formed in, for example, a substantially annular shape, and a cutout portion 561A that communicates with the inside and outside of the ring is provided in a part close to the side C3-C4.
The fixed electrode 561 is connected to a first extraction electrode 563 that extends to the side C3-C4 along the electrode extraction groove. The first extraction electrode 563 is connected to a first connection electrode 565 provided on the movable substrate 52 side in the electrode extraction groove.
In the present embodiment, a configuration in which one fixed electrode 561 is provided is shown. However, for example, a configuration in which two electrodes that are concentric circles around the filter center point O are provided (double electrode configuration) may be used. .

As shown in FIG. 3, the fixed reflective film 54 is provided on the tip surface of the reflective film installation portion 512. For example, a metal film such as Ag or an alloy film such as an Ag alloy can be used as the fixed reflection film 54. In addition, a third extraction electrode 541 extending to the electrode extraction groove through the notch 561A of the fixed electrode 561 is connected to the fixed reflection film 54. The third extraction electrode 541 is connected to a third connection electrode 542 provided on the movable substrate 52 side in the electrode extraction groove.
As the fixed reflective film 54, for example, a dielectric multilayer film in which the high refractive layer is TiO ₂ and the low refractive layer is SiO ₂ may be used. In this case, a conductive film such as a metal film (or alloy film) may be stacked on the dielectric multilayer film, and the third extraction electrode 541 may be connected to the conductive film.

  Of the surface of the fixed substrate 51 that faces the movable substrate 52, the surface on which the electrode placement groove 511, the reflective film installation portion 512, and the electrode lead-out groove are not formed by etching constitutes a joint portion 513 that is joined to the movable substrate 52. To do.

(Configuration of movable substrate)
The movable substrate 52 includes a circular movable portion 521 centered on the filter center point O, a holding portion 522 that is coaxial with the movable portion 521 and holds the movable portion 521 in a plan view as shown in FIG. A substrate outer peripheral portion 525 provided outside the portion 522. In addition, one end side (side C3-C4 side) of the movable substrate 52 protrudes outside the sides C7-C8 of the fixed substrate 51, and configures the electrical component 524.

  The movable part 521 is formed to have a thickness dimension larger than that of the holding part 522. For example, in this embodiment, the movable part 521 is formed to have the same dimension as the thickness dimension of the movable substrate 52. The movable portion 521 is formed to have a diameter that is larger than at least the diameter of the outer peripheral edge of the reflection film installation portion 512 in plan view. The movable part 521 is provided with a movable electrode 562 and a movable reflective film 55.

The movable electrode 562 is opposed to the fixed electrode 561 via the interelectrode gap Ge, and is formed in a substantially annular shape having the same shape as the fixed electrode 561. Similarly to the fixed electrode 561, the movable electrode 562 is also provided with a notch 562A at a part on the side C7-C8 side.
The movable electrode 562 includes a second extraction electrode 564 that extends from the outer peripheral edge of the movable electrode 562 to the electrode extraction groove of the fixed substrate 51 and extends to the electrical component 524. The second extraction electrode 564 is connected to the filter driving circuit 13 in the electrical component 524 by wiring such as FPC (Flexible Printed Circuits) and lead wires.

The movable reflective film 55 is provided at the center of the movable portion 521 so as to face the fixed reflective film 54 with the gap Gm between the reflective films. As the movable reflective film 55, a reflective film having the same configuration as that of the fixed reflective film 54 described above is used.
Connected to the movable reflective film 55 is a fourth extraction electrode 551 extending through the notch 562A of the movable electrode 562, passing through the region facing the electrode extraction groove, and extending to the electrical component 524. The fourth lead electrode 551 is connected to the gap detection circuit 14 in the electrical component 524 by wiring such as FPC (Flexible Printed Circuits) and lead wires.

Further, the movable substrate 52 includes a first connection electrode 565 and a third connection electrode 542 provided from the region facing the electrode facing groove to the electrical component 524.
The first connection electrode 565 is connected to a first extraction electrode 563 extending to the electrode facing groove via, for example, a bump electrode. In addition, the first connection electrode 565 is connected to the filter drive circuit 13 by wiring such as FPC in the electrical component 524.
The third connection electrode 542 is connected to a third extraction electrode 541 extending to the electrode facing groove via, for example, a bump electrode. Further, the third connection electrode 542 is connected to the gap detection circuit 14 by wiring such as FPC in the electrical component 524.

  In the present embodiment, as described above, an example in which the gap dimension of the interelectrode gap Ge is larger than the gap dimension of the inter-reflection film gap Gm is shown, but the present invention is not limited to this. For example, depending on the wavelength range of the light to be measured, the gap dimension of the inter-reflection film gap Gm may be larger than the gap dimension of the inter-electrode gap Ge.

The holding part 522 is a diaphragm that surrounds the periphery of the movable part 521, and has a thickness dimension smaller than that of the movable part 521. Such a holding portion 522 is more flexible than the movable portion 521 and can displace the movable portion 521 toward the fixed substrate 51 along the film thickness direction of the movable reflective film 55 by a slight electrostatic attractive force. . Therefore, when a constant voltage is continuously applied to the electrostatic actuator 56, the movable portion 521 vibrates around a position where the electrostatic attractive force by the electrostatic actuator 56 and the spring force (restoring force) of the holding portion 522 are balanced. (Insufficient attenuation), the vibration converges at the balanced position. When the voltage to the electrostatic actuator 56 is lowered, the movable portion 521 vibrates (insufficiently attenuates) with the damping ratio ζ set to 0 <ζ <1 with the restoring force of the holding portion 522 as the center.
In the present embodiment, the diaphragm-like holding part 522 is illustrated, but the present invention is not limited to this. For example, a configuration in which beam-like holding parts arranged at equiangular intervals around the filter center point O are provided. And so on.

  The substrate outer peripheral portion 525 is provided outside the holding portion 522 in plan view. The substrate outer peripheral portion 525 is bonded to the fixed substrate 51.

In the wavelength variable interference filter 5 as described above, when the voltage is applied between the fixed electrode 561 and the movable electrode 562 by the filter driving circuit 13, the movable portion 521 is displaced toward the fixed substrate 51 by electrostatic attraction. Thereby, the gap dimension of the gap Gm between the reflection films can be changed to a predetermined amount.
Further, the gap detection circuit 14 can detect the electrostatic capacitance between the fixed reflection film 54 and the movable reflection film 55, and can output a detection signal (detection value) to the control unit 20.

[Configuration of control unit]
Returning to FIG. 1, the control unit 20 of the optical device 1 will be described.
The control unit 20 is configured by combining, for example, a CPU (Central Processing Unit), a memory, and the like, and controls the entire operation of the optical device 1. As illustrated in FIG. 1, the control unit 20 includes a voltage control unit 21 and a signal acquisition unit 22.
In addition, the control unit 20 includes a storage unit 30, and V-λ data is stored in the storage unit 30. The V-λ data is data indicating the relationship of the wavelength of light extracted by the wavelength variable interference filter 5 with respect to the voltage applied to the electrostatic actuator 56 of the wavelength variable interference filter 5. This V-λ data is generated, for example, by measuring the transmission wavelength with respect to the voltage in advance when the wavelength variable interference filter 5 is manufactured, and is stored in the storage unit 30.
In addition, although the example with which the wavelength with respect to an applied voltage is recorded on V-lambda data is shown, the gap dimension of the gap Gm between reflection films may be recorded.

The voltage control unit 21 controls the filter driving circuit 13 to apply a voltage to the fixed electrode 561 and the movable electrode 562 of the electrostatic actuator 56.
The signal acquisition unit 22 acquires a light reception signal from the light receiving unit 11. In the present embodiment, the signal acquisition unit 22 calculates a detection value output from the light receiving unit 11 when the gap size becomes a target value based on the detection value (gap size) detected by the gap detection circuit 14. get.

  Specifically, when the gap dimension of the inter-reflective film gap Gm is equal to or less than the initial gap (gap dimension when no voltage is applied to the electrostatic actuator 56), the signal acquisition unit 22 uses the V-λ data. When the recorded voltage V is applied to the electrostatic actuator 56, a light reception signal output by the light receiving unit 11 is acquired.

In addition, the voltage control unit 21 applies a voltage V corresponding to the minimum wavelength in the V-λ data to the electrostatic actuator 56, and then drops the voltage in a step waveform to, for example, 0V. In this case, when the voltage applied to the electrostatic actuator 56 is changed to 0 V in a step waveform, the movable portion 521 is displaced in the direction of returning to the initial position by the spring force (restoring force) of the holding portion 522, and the initial position And the gap dimension of the gap Gm between the reflection films becomes larger than the initial gap Gm0.
And the signal acquisition part 22 acquires the light reception signal output from the light-receiving part 11, when the gap detection value detected by the gap detection circuit 14 turns into a preset target value.

[Driving method of optical device]
Next, a method for driving the optical device 1 will be described with reference to the drawings.
FIG. 4 is a flowchart showing a driving method of the optical device 1 of the present embodiment. FIG. 5 is a diagram illustrating a voltage waveform of a voltage applied to the electrostatic actuator 56 in the present embodiment. In FIG. 4, “Act” is an abbreviation for the electrostatic actuator 56. In FIG. 5 and FIG. 6 described later, T1 is a period in which step S1 is performed, and T2 is a period in which steps S2 to S6 are performed.
As shown in FIG. 4, in the optical device 1, when performing spectroscopic measurement on a measurement target, first, the voltage control unit 21 sequentially reads the voltage V from the V-λ data stored in the storage unit 30. Then, the voltage control unit 21 sequentially applies the voltage V read to the electrostatic actuator 56 of the wavelength variable interference filter 5 in a step waveform as shown in FIG. 5 (step S1; first step).

FIG. 6 shows the relationship between the elapsed time and the gap dimension of the gap Gm between the reflection films of the wavelength tunable interference filter 5 in the driving method of the optical device 1 of this embodiment, and the elapsed time and the light transmitted through the wavelength tunable interference filter 5. It is a figure which shows the relationship with a wavelength (transmission wavelength (lambda)). FIG. 7 is a schematic diagram showing the wavelength variable interference filter 5 when the movable portion 521 is displaced in step S1.
In step S1, a voltage V is applied to the electrostatic actuator 56, whereby an electrostatic attractive force acts between the inter-electrode gap Ge, and the movable portion 521 is displaced toward the fixed substrate 51 as shown in FIG. .
At this time, the voltage control unit 21 increases the voltage applied to the electrostatic actuator 56 at predetermined time intervals. For this reason, every time the voltage increases by one step, the movable portion 521 is displaced toward the fixed substrate 51 by an amount corresponding to the voltage change. Thus, as shown in FIG. 6, the gap dimension of the reflective film gap Gm is also the initial gap Gm0, decreases stepwise to the minimum gap Gm_min corresponding to the maximum voltage _{V Max.} Thereby, the wavelength transmitted through the wavelength tunable interference filter 5 is also stepwise, for example, at an interval of 20 nm from an initial wavelength (for example, 750 nm) corresponding to the initial gap Gm0 to a minimum wavelength (for example 400 nm) corresponding to the minimum gap Gm_min. Change.

Here, the maximum voltage V _Max necessary for displacing the movable part 521 to the lower limit position where the gap dimension of the inter-reflective film gap Gm is the minimum gap Gm_min is set to the movable part 521 and the holding part 522 in step S3 described later. When the vibration is caused by the restoring force, the maximum gap size (vibration amplitude) of the gap Gm between the reflection films reaches a maximum gap Gm_max corresponding to the maximum wavelength λ _Max (for example, 900 nm) at which measurement is performed. Become.

In step S <b> 1, the signal acquisition unit 22 acquires a light reception signal output from the light reception unit 11 every time the voltage V applied to the electrostatic actuator 56 is switched. More specifically, after a lapse of the stabilization time Δt from when the voltage V to the electrostatic actuator 56 is switched until the vibration of the movable portion 521 stops, the voltage V to the electrostatic actuator 56 is next. The received light signal is acquired until switching.
At this time, the signal acquisition unit 22 refers to the detection value from the gap detection circuit 14 and the detection value becomes a predetermined gap dimension (target value) corresponding to the voltage V applied to the electrostatic actuator 56. In addition, a light reception signal may be acquired.

When the gap dimension of the inter-reflective film gap Gm becomes the minimum gap Gm_min by step S1 and the light reception signal for the minimum gap Gm_min is acquired by the signal acquisition unit 22, next, as shown in FIG. 21 sets the voltage applied to the electrostatic actuator 56 to 0 V (step S2; second step). At this time, the voltage control unit 21 changes the voltage V applied to the electrostatic actuator 56 according to the step waveform.
FIG. 8 is a schematic diagram showing the wavelength variable interference filter 5 when the movable part 521 is displaced in step S2.
As described above, in the present embodiment, in step S1, the maximum voltage V _{Max that} is applied last is a voltage that is displaced to the lower limit position where the gap dimension of the inter-reflective film gap Gm is the minimum gap Gm_min. Thereby, the movable part 521 is displaced toward the initial position by the restoring force of the holding part 522, and the initial position (position of the initial gap Gm0) is underdamped vibration with the damping ratio ζ 0 <ζ <1. Vibrates in the center. For this reason, as shown in FIG. 8, the movable part 521 can be displaced to a position where the gap dimension of the inter-reflection film gap Gm is equal to or larger than the initial gap Gm0.

Then, the signal acquisition unit 22 refers to the gap size (detected value) of the inter-reflective film gap Gm detected by the gap detection circuit 14, and determines whether or not the initial gap Gm0 is reached (step S3). When it is determined No in step S3, the process returns to step S3.
If it determines with Yes in step S3, the signal acquisition part 22 will further determine whether the detection value in the gap detection circuit 14 became the target value Gmx corresponding to a predetermined target wavelength (step S4).
If it is determined as Yes in step S4, the signal acquisition unit 22 acquires a light reception signal when the target value Gmx is detected in the gap detection value (step S5; third step).
Specifically, the signal acquisition unit 22 continues to acquire a light reception signal at a predetermined sampling frequency after step S2, that is, after the voltage applied to the electrostatic actuator 56 has been lowered, of which the gap detection circuit 14 The received light signal sampled at the timing when the detected value from the target value Gmx becomes the target value Gmx is acquired as the received light signal for the target value.

When it determines with No in step S4, or after step S5, the signal acquisition part 22 determines whether the vibration of the movable part 521 has converged (step S6). Specifically, the signal acquisition unit 22 determines whether or not the detection values in the gap detection circuit 14 sampled in a predetermined period continuously become the initial gap Gm0. When it determines with No in step S6, it returns to step S4.
On the other hand, when it is determined Yes in step S6, the signal acquisition unit 22 determines whether or not the light reception signals (for example, the light reception signals of the light having the wavelength of 20 nm intervals) for all the target wavelengths are acquired (step). S7). If it is determined No in step S7, the process returns to step S1. If it is determined Yes in step S7, the received light amount measurement process is terminated.

[Operational effects of the first embodiment]
In this embodiment, the electrostatic actuator 56 applies the gap dimension between the reflection films 54 and 55 to the wavelength variable interference filter 5, the light receiving unit 11 that receives the light transmitted through the wavelength variable interference filter 5, and the electrostatic actuator 56. A voltage control unit 21 that controls a voltage to be received, and a signal acquisition unit 22 that acquires a light reception signal from the light reception unit 11. In step S1, the voltage control unit 21 applies a voltage to the electrostatic actuator 56 so that the gap size of the gap Gm between the reflection films is changed from the initial gap Gm0 to the minimum gap Gm_min, thereby displacing the movable unit 521. In S2, the voltage applied to the electrostatic actuator 56 is set to 0V. Thereafter, when the detection value from the gap detection circuit 14 exceeds the initial gap Gm0 and reaches a predetermined target value, the signal acquisition unit 22 acquires the light reception signal from the light reception unit 11 in step S5.
That is, in this embodiment, the movable part 521 vibrates toward the initial position by the restoring force of the holding part 522 in step S2 after step S1. The signal acquisition unit 22 acquires a light reception signal output from the light reception unit 11 when the movable unit 521 is displaced from the initial position to the side opposite to the fixed substrate 51.
As a result, the optical device 1 can acquire the received light amount of light having a wavelength corresponding to the inter-reflection film gap Gm having a size larger than the initial gap Gm0. That is, in addition to the light reception signal (light reception amount) of light of each wavelength from the initial gap Gm0 to the minimum gap Gm_min, the wavelength corresponding to the maximum gap Gm_max larger than the initial gap Gm0 (in the example of FIG. 6, about 900 nm). A light reception signal of light of each wavelength can be acquired, and the amount of light received in a wide wavelength range (scanning range) can be measured.

  In the present embodiment, the voltage control unit 21 drops the voltage from the maximum voltage to 0 V using a step waveform in step S2. Thereby, the movable part 521 receives a strong restoring force of the holding part 522, and the vibration amplitude of the movable part 521 can be increased. Therefore, the amount of light received with a longer wavelength can be measured.

  In the present embodiment, the wavelength variable interference filter 5 is stored in the housing 101, and the housing 101 is maintained under reduced pressure. For this reason, the air resistance which acts on the movable part 521 is small, and the displacement amount when the movable part 521 is displaced toward the initial position by the restoring force in step S2 can be increased.

In the present embodiment, when the voltage control unit 21 obtains a light reception signal with the gap Gm between the reflection films as the gap size equal to or larger than the initial gap Gm0 in step S5, the movable unit 521 can be displaced to the gap size corresponding to the target wavelength. A maximum voltage is applied to the electrostatic actuator 56 in step S1.
Thereby, the movable part 521 can be made to reach | attain a target position by step S2, and the signal acquisition part 22 can acquire the light reception signal of the light of a target wavelength.

  In the present embodiment, in step S1, the voltage control unit 21 applies the maximum voltage to be displaced to the lower limit position where the gap dimension of the inter-reflection film gap Gm becomes the minimum gap Gm_min. Thereby, when the voltage is lowered in step S2, the movable portion 521 can be displaced beyond the initial gap Gm0.

  In the present embodiment, the signal acquisition unit 22 acquires a light reception signal output from the light reception unit 11 when the gap size of the inter-reflection film gap Gm detected by the gap detection circuit 14 reaches a target value. Thereby, when the gap dimension of the gap Gm between the reflection films becomes equal to or larger than the initial gap Gm0, it is possible to accurately acquire the amount of light received with respect to light having a desired target wavelength.

[Second Embodiment]
Next, a second embodiment according to the present invention will be described.
In the first embodiment, the voltage control unit 21 sets a voltage at which the movable unit 521 can be displaced to a desired position by a restoring force as the maximum voltage to be applied to the electrostatic actuator 56 in step S1, and is electrically reflected. The gap size of the inter-film gap Gm was controlled. However, in the electrostatic actuator 56, the electrostatic attraction acting between the electrodes 561 and 562 increases as the distance between the electrodes 561 and 562 decreases, so that the inter-electrode gap Ge is 2/3 of the initial inter-electrode gap Ge0. With the following dimensions, gap control becomes difficult.
Therefore, when the minimum gap Gm_min of the inter-reflection film gap Gm is 2/3 or less of the initial inter-electrode gap Ge0, the reflection films may be in contact with each other and be damaged.
On the other hand, the second embodiment is different from the above-described embodiment in that the gap dimension of the gap Gm between the reflection films is controlled using a stopper.

FIG. 9 is a cross-sectional view showing a schematic configuration of the variable wavelength interference filter 5 of the second embodiment. FIG. 10 is a cross-sectional view of the wavelength variable interference filter 5 when the movable portion 521 is displaced toward the fixed substrate 51 in FIG. In the following description, the same reference numerals are given to the items already described, and the description is omitted or simplified.
In the present embodiment, a fixed-side stopper 515 is erected from the electrode arrangement groove 511 of the fixed substrate 51 toward the movable substrate 52. Specifically, the fixed side stopper 515 is provided between the fixed electrode 561 in the electrode arrangement groove 511 and the reflective film installation portion 512. As the fixed-side stopper 515, for example, a rod-shaped member may protrude from the fixed substrate 51 toward the movable substrate 52, or a substantially annular (cylindrical) member centering on the filter center point O may protrude. Good. In the present embodiment, an example in which the electrode is provided in the electrode placement groove 511 is shown.
The protruding front end surface (the front end surface on the movable substrate 52 side) of the fixed side stopper 515 is located closer to the movable substrate 52 than the surface of the fixed reflective film 54 on the movable substrate 52 side.

The movable portion 521 of the movable substrate 52 is provided with a movable side stopper 526 at a position corresponding to the fixed side stopper 515 in plan view. This movable side stopper 526 has substantially the same configuration as the fixed side stopper 515, and may be constituted by, for example, a rod-like member or an annular member.
The protruding front end surface of the movable side stopper 526 (the front end surface on the fixed substrate 51 side) is located closer to the fixed substrate 51 than the surface of the movable reflective film 55 on the fixed substrate 51 side.
That is, the distance between the projecting tip surface of the movable stopper 526 (tip surface on the fixed substrate 51 side) and the projecting tip surface of the fixed stopper 515 (tip surface on the movable substrate 52 side) is the fixed substrate of the movable reflective film 55. The distance is smaller than the distance between the surface on the 51 side and the side surface of the fixed reflecting film 54 on the movable substrate 52, so that the movable reflecting film 55 and the fixed reflecting film 54 are prevented from contacting each other.

  In this embodiment, when the maximum voltage is applied to the electrostatic actuator 56 in step S1 of FIG. 4, when the gap Gm between the reflection films reaches a predetermined first gap dimension, as shown in FIG. The fixed side stopper 515 and the movable side stopper 526 come into contact with each other, and the displacement of the movable part 521 is suppressed. In the present embodiment, the first gap dimension is the minimum gap Gm_min. Here, the first gap dimension is such that the inter-electrode gap Ge is 2/3 of the initial inter-electrode gap Ge0.

  In this embodiment, the gap dimension of the inter-reflection film gap Gm can be appropriately set to the minimum gap Gm_min without bringing the fixed reflection film 54 and the movable reflection film 55 into contact with each other. For this reason, when the voltage applied to the electrostatic actuator 56 is lowered in step S2 and the movable part 521 is displaced in the direction away from the fixed substrate 51 by the restoring force, a stronger restoring force can be applied. The vibration amplitude of 521 can be increased.

In particular, in the electrostatic actuator 56, the generated electrostatic attractive force is inversely proportional to the square of the gap dimension between the electrodes 561 and 562. Therefore, the gap control becomes more difficult as the inter-electrode gap Ge becomes smaller. On the other hand, in this embodiment, since the stoppers 515 and 526 are brought into contact with each other, complicated control becomes unnecessary.
In addition, every time measurement using the optical device 1 is performed, the minimum gap Gm_min does not fluctuate, and the same restoring force can be applied to the movable portion 521 every time. That is, as described above, it is difficult to maintain the gap size of the gap Gm between the reflection films at the minimum gap Gm_min without bringing the fixed reflection film 54 and the movable reflection film 55 into contact with each other only by controlling the voltage to the electrostatic actuator 56. However, in this embodiment, the minimum gap Gm_min can be set to a high level by bringing the stoppers 515 and 526 into contact with each other. Thereby, the vibration of the movable part 521 after step S2 can be made the same vibration every time, and the light reception signal with respect to the light of a desired target wavelength can be acquired accurately.

  Further, in the present embodiment, a fixed-side stopper 515 is provided between the fixed electrode 561 and the fixed reflective film 54, and a movable-side stopper 526 is provided between the movable electrode 562 and the movable reflective film 55. Thereby, even when the movable part 521 is bent by the electrostatic attractive force of the electrostatic actuator 56, the contact between the fixed reflective film 54 and the movable reflective film 55 can be suppressed.

[Third embodiment]
Next, a third embodiment according to the present invention will be described.
In the first embodiment, in step S4 and step S5, the signal acquisition unit 22 receives light when the detection value (gap size of the gap Gm between the reflection films) detected by the gap detection circuit 14 becomes the target value. An example of acquiring a signal was shown. On the other hand, in this embodiment, the signal acquisition part 22 is different by the point which acquires a received light signal based on elapsed time.

FIG. 11 is a flowchart showing a driving method of the optical device 1 of the present embodiment.
In this embodiment, as shown in FIG. 11, the same steps S1 and S2 as in the first embodiment are performed.
In the present embodiment, simultaneously with step S2, the signal acquisition unit 22 starts the time measuring means (internal timer) provided in the control unit 20 and starts counting elapsed time (step S11).

Thereafter, the signal acquisition unit 22 refers to the elapsed time counted in step S11, acquires a light reception signal output from the light reception unit 11 at a predetermined time interval, and is detected by the gap detection circuit 14. The detected value is acquired (step S12).
Then, the process of step S7 of 1st embodiment is implemented.

Here, the “predetermined time interval” may be the sampling interval in the first embodiment.
In this embodiment, the control unit 20 further calculates a spectral spectrum (spectral spectrum curve) for each wavelength based on the received light signal acquired at a predetermined time interval and the detected gap size (detected value). calculate. Thereby, the control part 20 can acquire the received light quantity with respect to the light of a target wavelength from the calculated spectrum.

[Fourth embodiment]
Next, a fourth embodiment according to the present invention will be described.
In the third embodiment, the signal acquisition unit 22 has shown an example in which the light reception signal and the detection value from the gap detection circuit 14 are acquired at predetermined time intervals. On the other hand, in the present embodiment, the signal acquisition unit 22 is different in that the light reception signal is acquired when the elapsed time reaches a preset measurement time (not necessarily a constant interval).

FIG. 12 is a flowchart showing a driving method of the optical device 1 of the present embodiment.
In the present embodiment, as shown in FIG. 12, the same processes of Step S1, Step S2, and Step S11 as in the third embodiment are performed.
Thereafter, the signal acquisition unit 22 determines whether or not the elapsed time counted in step S11 has reached a preset time (measurement time) (step S21).
Here, in the present embodiment, the measurement time is acquired in advance and recorded in the storage unit 30 at the time of manufacturing the wavelength variable interference filter 5 or before performing the measurement. For example, the elapsed time when the maximum voltage V _Max is applied to the electrostatic actuator 56 and the movable portion 521 is displaced to the lower limit position, and the voltage to the electrostatic actuator 56 is decreased to cause underdamped vibration. And the detection value (gap size of the gap Gm between the reflection films) detected by the gap detection circuit 14 is measured. Then, an elapsed time corresponding to the target value Gmx corresponding to the target wavelength is measured in advance as a measurement time and stored in the storage unit 30.

In step S21, if the signal acquisition unit 22 determines Yes, the signal acquisition unit 22 acquires a light reception signal output from the light reception unit 11 when the measurement time is reached (step S22).
Moreover, the signal acquisition part 22 progresses to the process of step S6, when it determines with No in step S21, or after step S22.

  In this embodiment, it is not necessary to acquire the detection value from the gap detection circuit 14 when acquiring the light reception signal from the light receiving unit 11. Therefore, it is not necessary to synchronize the signal acquisition from the light receiving unit 11 and the signal acquisition from the gap detection circuit 14, and the processing load during signal acquisition can be reduced. Further, no error due to synchronization deviation occurs, and the measurement accuracy can be improved.

  In the present embodiment, the variable wavelength interference filter 5 is a stopper that suppresses the displacement of the movable portion 521 toward the fixed substrate 51 when the movable portion 521 is positioned at the lower limit position, as in the second embodiment described above. It is more preferable to have a configuration including (fixed side stopper 515 and movable side stopper 526). In this case, the vibration waveform in which the movable part 521 vibrates from the lower limit position due to the restoring force can be made uniform, and the measurement accuracy can be improved.

[Modification]
It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

In said 1st embodiment, when it determines with No in step S7, it returned to step S1, but it is not limited to this. For example, in step S1, when the light reception signal for the target wavelength has been acquired between the initial gap Gm0 and the minimum gap Gm_min, the light reception signal acquisition processing by the signal acquisition unit 22 in step S1 may be omitted. Further, when the received light signal for the wavelength of the initial gap Gm0 or more obtained by the process of step S5 has been acquired, step S2 and subsequent steps may be omitted.
In the above embodiment, step S2 is executed after the light reception signal for the minimum gap Gm_min is acquired in step S1, but the present invention is not limited to this. For example, after acquiring a light reception signal for a gap wider than the minimum gap Gm_min, the process may proceed to step 2.

  In the second embodiment, the fixed side stopper 515 is provided on the fixed substrate 51, and the movable side stopper 526 is provided on the movable substrate 52. However, the present invention is not limited to this. For example, a stopper that can contact the movable portion 521 only on the fixed substrate 51 may be provided, or a stopper that can contact the fixed substrate 51 only on the movable substrate 52 may be provided.

In the second embodiment, the protruding tip surface of the fixed side stopper 515 is positioned closer to the movable substrate 52 than the surface of the fixed reflective film 54 on the movable substrate 52 side, and the protruding tip surface of the movable side stopper 526 is movable reflecting. Although an example in which the film 55 is located on the fixed substrate 51 side from the surface on the fixed substrate 51 side is shown, the present invention is not limited to this. For example, the protruding front end surface of the fixed side stopper 515 may be positioned closer to the fixed substrate 51 than the surface of the fixed reflection film 54 on the movable substrate 52 side. In this case, the protruding dimension of the movable side stopper 526 is made larger. That's fine.
Further, as long as the movable reflective film 55 and the fixed reflective film 54 can be prevented from coming into contact with each other, either the movable side stopper 526 or the fixed side stopper 515 may be provided.

In the second embodiment, the first gap dimension is the minimum gap Gm_min, and when the fixed stopper 515 and the movable stopper 526 come into contact with each other, the amount of light having a desired minimum wavelength (for example, 400 nm) is detected. showed that. On the other hand, for example, when measuring the light having the minimum wavelength to be acquired, the fixed side stopper 515 and the movable side stopper 526 may not be in contact with each other.
In this case, the first gap dimension is smaller than the minimum gap Gm_min, and the inter-electrode gap Ge at that time is 2/3 or less of the initial inter-electrode gap Ge0. After obtaining the amount of received light of each wavelength from the wavelength corresponding to the initial gap Gm0 to the minimum wavelength, the voltage applied to the electrostatic actuator 56 is further increased to bring the fixed side stopper 515 and the movable side stopper 526 into contact ( The movable part 521 is moved to a position that becomes the first gap dimension). Then, the voltage applied to the electrostatic actuator 56 is lowered, and the movable portion 521 is displaced by the restoring force. As in the above embodiments, the gap dimension of the inter-reflective film gap Gm is set to a position where the gap is equal to or larger than the initial gap Gm0. Displace. As described above, it is possible to measure the amount of received light of each wavelength with respect to a desired wavelength range.

  In 1st embodiment, although the voltage control part 21 showed the example which changes the voltage applied to the electrostatic actuator 56 with a step waveform in step S2, it is not limited to this. For example, the voltage control unit 21 may change (drop) the voltage applied to the electrostatic actuator 56 with a first-order lag waveform. In this case, although the vibration amplitude of the movable part 521 becomes small, the time until the vibration converges can be shortened.

  In the first embodiment, the signal acquisition unit 22 acquires the light reception signal when the detection value (gap size) detected by the gap detection circuit 14 reaches the predetermined target value Gmx. The target value Gmx The average value of the received light signal may be obtained by acquiring the received light signal for a plurality of times. For example, when the movable part 521 is displaced from the initial gap Gm0 to the maximum gap Gm_max, a first light reception signal with respect to the target value Gmx is acquired, and when the movable part 521 returns from the maximum gap Gm_max to the initial gap Gm0, the target value is obtained. A second light reception signal for Gmx is acquired. Then, a signal value obtained by averaging the first received light signal and the second received light signal may be acquired as the received light amount with respect to the target value Gmx.

  In the fourth embodiment, the gap detection circuit 14 may not be provided. In this case, when the wavelength tunable interference filter 5 is manufactured, the position of the movable portion 521 (gap size of the gap Gm between the reflection films) when the movable portion 521 is underdamped and oscillated from the lower limit position and the position are reached. It is sufficient to measure the elapsed time up to and store in the storage unit 30 in advance.

By using the driving method of the optical device 1 shown in the first to fourth embodiments described above, the wavelength scanning range (measurement range) in the measurement process using the existing wavelength variable interference filter 5 can be expanded. . On the other hand, when the scanning range of the target wavelength is set in advance, the tunable interference filter 5 can be reduced in size and power can be saved.
For example, in the past, for the scanning range (λ1> λ2) from the wavelength λ1 to λ2, the initial gap Gm0 of the inter-reflective film gap Gm is the gap size corresponding to the wavelength λ1, and the minimum gap Gm_min is the gap corresponding to the wavelength λ2. It was necessary to make it a dimension. On the other hand, in the present invention, the initial gap Gm0 of the inter-reflection film gap Gm is set to a gap size corresponding to λ3 between the wavelengths λ1 and λ2, and the minimum gap Gm_min is set to a gap size corresponding to the wavelength λ2. it can. In this case, since λ1−λ2> λ3−λ2, the maximum voltage V _Max required for transmitting light of the minimum wavelength from the wavelength variable interference filter 5 can be reduced as compared with the conventional case.

  In addition, the specific structure for carrying out the present invention can be appropriately changed to other structures and the like within a range in which the object of the present invention can be achieved.

  DESCRIPTION OF SYMBOLS 1 ... Optical apparatus (optical module), 5 ... Wavelength variable interference filter, 10 ... Optical filter device, 11 ... Light-receiving part, 12 ... Signal processing circuit, 13 ... Filter drive circuit, 14 ... Gap detection circuit, 20 ... Control part, DESCRIPTION OF SYMBOLS 21 ... Voltage control part, 22 ... Signal acquisition part, 30 ... Memory | storage part, 51 ... Fixed board | substrate, 52 ... Movable board | substrate, 54 ... Fixed reflection film, 55 ... Movable reflection film, 56 ... Electrostatic actuator, 101 ... Housing | casing, 515: fixed side stopper, 521: movable part, 522 ... holding part, 526 ... movable side stopper, Ge: gap between electrodes, Gm: gap between reflection films, Gm0: initial gap, Gm_max: maximum gap, Gm_min: minimum gap, Gmx: Target value.

Claims (9)

By a first reflective film, a movable part including a second reflective film facing the first reflective film, a holding part that holds the movable part in a film thickness direction of the second reflective film, and a voltage application A variable wavelength interference filter comprising an electrostatic actuator that displaces the movable part toward the first reflective film;
A light receiving unit that receives light emitted from the wavelength variable interference filter and outputs a light reception signal;
A voltage controller for controlling the voltage applied to the electrostatic actuator;
A signal acquisition unit for acquiring the received light signal from the light receiving unit,
When the voltage is not applied to the electrostatic actuator, the gap dimension between the first reflective film and the second reflective film is an initial gap,
The voltage controller applies the voltage to the electrostatic actuator to displace the movable part toward the first reflective film, and then drops the voltage so that the gap size becomes larger than the initial gap. Displace the movable part to a position,
The optical module, wherein the signal acquisition unit acquires the light reception signal from the light reception unit when the movable unit is positioned at a position where the gap dimension is larger than the initial gap. The optical module according to claim 1,
The said voltage control part drops the said voltage by changing the said voltage with a step waveform. The optical module characterized by the above-mentioned. The optical module according to claim 1 or 2,
A housing for storing the variable wavelength interference filter;
The optical module is characterized in that the inside of the housing is maintained under reduced pressure. The optical module according to any one of claims 1 to 3,
The voltage control unit applies the voltage to the electrostatic actuator so that the gap dimension reaches a target value corresponding to a target wavelength when the movable unit is displaced due to a drop in the voltage. Optical module. The optical module according to any one of claims 1 to 4,
The voltage control unit is configured such that an inter-electrode gap dimension, which is a gap dimension between a pair of electrodes constituting the electrostatic actuator, is an initial inter-electrode gap dimension when no voltage is applied to the pair of electrodes. An optical module, wherein the voltage is dropped after applying the voltage for displacing the movable part to a position that is 2/3 or less of the gap. The optical module according to claim 5, wherein
The tunable interference filter includes a stopper that suppresses displacement of the movable portion toward the first reflective film when the gap size reaches a predetermined first gap size. The optical module according to any one of claims 1 to 6,
The optical module, wherein the signal acquisition unit acquires the light reception signal at a predetermined time interval after the voltage is dropped. The optical module according to any one of claims 1 to 6,
A gap detector for detecting the gap dimension;
The optical module, wherein the signal acquisition unit acquires the received light signal when the gap size detected by the gap detection unit reaches a predetermined target value. A movable part including a first reflective film, a second reflective film facing the first reflective film, a holding part for holding the movable part displaceably in the film thickness direction of the second reflective film, and a voltage A wavelength tunable interference filter including an electrostatic actuator that displaces the movable portion toward the first reflecting film by application; and a light receiving portion that receives light emitted from the wavelength tunable interference filter and outputs a light reception signal. A method for driving an optical module including:
When the voltage is not applied to the electrostatic actuator, the gap dimension between the first reflective film and the second reflective film is an initial gap,
A first step of applying the voltage to the electrostatic actuator and displacing the movable part toward the first reflective film;
A second step of dropping the voltage to the electrostatic actuator;
In the second step, when the movable part is displaced to a position where the gap dimension is larger than the initial gap, a third step of acquiring the light reception signal from the light receiving part;
A method for driving an optical module, comprising:

Images