JP2013160707A - Capacitance detection circuit, optical module and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitance detection circuit that can reduce influence of parasitic capacitance and can highly accurately detect capacitance of a capacitor, and further to provide an optical module and an electronic apparatus.SOLUTION: A capacitance detection circuit 10 comprises: a detection target capacitor Cx; a sine wave generation circuit 11 for outputting an input signal, sine wave signal, to an input terminal of the detection target capacitor Cx; an operational amplifier 12 in which an output terminal of the detection target capacitor Cx is connected to an inverting input terminal and a non-inverting input terminal is connected to the GND; a feedback circuit 13 that is connected between an output terminal and the inverting input terminal of the operational amplifier 12 and is provided with an impedance element 13A; a timing signal generation circuit 15 for generating a timing signal synchronized with the input signal output from the sine wave generation circuit 11; and a sample-and-hold circuit 14 that is connected to the output terminal of the operational amplifier 12 and acquires an output signal from the operational amplifier 12 at timing based on the timing signal.

Description

  The present invention relates to a capacitance detection circuit that detects a capacitance of a capacitor, an optical module including the capacitance detection circuit, and an electronic apparatus.

Conventionally, a capacitance detection circuit for detecting the capacitance of a capacitor is known (see, for example, Patent Document 1).
FIG. 19 shows a conventional capacitance detection circuit.
As shown in FIG. 19, in the conventional capacitance detection circuit, a switch S1 is connected to an input terminal of a detection voltage, and a capacitor Cx1 that is a capacitance detection target and a switch S2 are connected to the output terminal of the switch S1. The Capacitor Cx1 has the other terminal to which switch S1 is not connected connected to the ground (GND). In the switch S2, the other terminal to which the switch S1 is not connected is connected to the inverting input terminal of the operational amplifier OP. The non-inverting input terminal of the operational amplifier OP is connected to GND. A feedback circuit is provided between the output terminal of the operational amplifier OP and the inverting input terminal of the operational amplifier OP. In this feedback circuit, a feedback capacitor Cf and a switch S3 are connected in parallel. The output terminal of the operational amplifier OP is connected to the sample and hold circuit via the switch S4.

In the conventional capacitance detection circuit as shown in FIG. 19, the capacitance of the capacitor Cx1 is detected by the following procedure.
First, at the first timing, the voltage Va is applied to the detection voltage input terminal, and at the same time, the switches S1 and S3 are connected (ON state), and the switches S2 and S4 are disconnected (OFF state). As a result, the feedback circuit is short-circuited, and the charge of the feedback capacitor Cf is discharged. Further, the capacitor Cx1 is charged.
Next, at the second timing, the switches S1 and S3 are switched to the ON state, the switch S2 is switched to the ON state, and the switch S4 is maintained in the OFF state. As a result, the discharge current of the capacitor Cx1 flows to the operational amplifier OP, and an equal current also flows to the feedback capacitor Cf, so that the voltage at the feedback capacitor Cf increases. Note that the feedback capacitor Cf has a fixed capacity and is known.
Thereafter, at the third timing, the switch S4 is switched to the ON state, and the voltage of the feedback capacitor Cf is taken into the sample and hold circuit.
As described above, a voltage corresponding to the capacitance of the capacitor Cx1 is generated in the feedback capacitor Cf, and by measuring the voltage, the capacitance of the capacitor Cx1 can be detected.

JP 11-326409 A

By the way, in the conventional capacitance detection circuit as described above, when parasitic capacitance occurs, the voltage output to the sample and hold circuit also changes, and there is a problem that the detection accuracy decreases.
20 and 21 are diagrams for explaining the current flowing through the operational amplifier OP when parasitic capacitance is generated in the capacitance detection circuit of FIG. Here, it is assumed that parasitic capacitances Ca and Cb are generated between the ground (GND) on the input side and the output side of the capacitor Cx1, respectively.
In the conventional capacitance detection circuit, when the switch S1 is switched to the ON state and the switch S2 is switched to the OFF state at the first timing, the current Is flows through the capacitor Cx1, as shown in FIG. At this time, since the parasitic capacitance Cb generated on the output end side of the capacitor Cx1 is connected to the GND, no current flows, but the current Ip flows in the parasitic capacitance Ca generated on the input end side of the capacitor Cx1.
Next, when the switch S1 is switched to the OFF state at the second timing and the switch S2 is switched to the ON state, as shown in FIG. 21, the charge stored in the capacitor Cx1 is used as the current Is as the inverting input of the operational amplifier OP. Flows to the terminal. At this time, the charge stored in the parasitic capacitance Ca also flows to the operational amplifier OP as a current Ip. Therefore, a current of Is + Ip flows through the feedback capacitor Cf, and the output voltage of the operational amplifier OP increases by the amount of the current Ip. As described above, it is impossible to accurately detect the capacitance of the capacitor Cx1.

  It is an object of the present invention to provide a capacitance detection circuit, an optical module, and an electronic device that can reduce the influence of parasitic capacitance and can detect the capacitance of a capacitor with high accuracy.

  A capacitance detection circuit of the present invention includes a detection target capacitor that is a detection target of a capacitance, a sine wave generation circuit that outputs a sine wave signal to an input terminal of the detection target capacitor, an inverting input terminal, a non-inverting input terminal, and an output An operational amplifier in which an output terminal of the detection target capacitor is connected to the inverting input terminal, and the non-inverting input terminal is connected to the ground, and is connected between the output terminal and the inverting input terminal of the operational amplifier. A feedback circuit provided with an impedance element; a timing signal generation circuit that generates a timing signal synchronized with the sine wave signal output from the sine wave generation circuit; and the timing signal connected to the output terminal of the operational amplifier. A sample-and-hold circuit that acquires an output signal from the operational amplifier at a timing based on It is characterized in.

According to the present invention, the output terminal of the detection target capacitor is connected to the inverting input terminal of the operational amplifier, and the non-inverting input terminal of the operational amplifier is connected to the ground (GND). Therefore, when the sine wave signal output from the sine wave generation circuit is input to the detection target capacitor, the output of the operational amplifier has a voltage corresponding to the ratio between the impedance of the detection target capacitor and the impedance of the impedance element of the feedback circuit. Become.
On the other hand, the phase of the output signal output from the operational amplifier is inverted with respect to the sine wave signal. Therefore, it is possible to detect the peak voltage of the output signal by detecting the output signal at a timing shifted by a half cycle of the sine wave signal from the timing at which the peak voltage is output in the sine wave signal. In other words, by generating a timing signal synchronized with the sine wave signal by the timing signal generation circuit, the sample and hold circuit can detect (acquire) the peak voltage of the output signal based on this timing signal. Become.
Since the impedance of the impedance element is a fixed value, the impedance and capacitance of the detection target capacitor are calculated based on the signal value of the output signal acquired by the sample and hold circuit and the signal value of the sine wave signal. can do.

Here, a case where there is a parasitic capacitance between the input terminal and the output terminal of the detection target capacitor between the ground (GND) will be described. In the present invention, when there is a parasitic capacitance between the input terminal side of the capacitor to be detected and the ground, a current flows in the parasitic capacitance due to the voltage of the sine wave signal output from the sine wave generation circuit, but this current flows in the GND. Therefore, no current flows through the operational amplifier.
Further, since the non-inverting input terminal of the operational amplifier is connected to GND, the potential of the inverting input terminal is also set to the GND level (reference potential) due to an imaginary short of the operational amplifier. Therefore, even when there is a parasitic capacitance between the output terminal side of the detection target capacitor and the ground, the potential on both ends of the parasitic capacitance is at the GND level, and no current flows.
As described above, according to the present invention, it is possible to reduce the influence of the parasitic capacitance, and to accurately detect the capacitance of the detection target capacitor.

  Further, in the conventional capacitance detection circuit as shown in FIG. 19, four switches are provided. For this reason, it is necessary to manage crosstalk so that signals for controlling these switches do not affect other signals, which makes circuit board design difficult. On the other hand, in the present invention, no switch is required to perform capacitance detection, the substrate configuration can be simplified, and crosstalk can be prevented.

  In the capacitance detection circuit of the present invention, the timing signal generation circuit includes a first one-shot circuit that outputs a first timing signal synchronized with the sine wave signal, and a peak of the output signal based on the first timing signal. A second one-shot circuit that outputs a second timing signal synchronized with a timing at which the voltage is output, and the sample and hold circuit acquires an output signal at a timing at which the second timing signal is output. Is preferred.

In the present invention, the timing signal generation circuit generates a first timing signal synchronized with the sine wave signal by the first one-shot circuit, and the second one-shot circuit generates an output signal based on the first timing signal. A second timing signal that matches the timing at which the peak voltage is output is output.
In this way, by providing two one-shot circuits, even if there is a phase difference between the sine wave signal output from the sine wave generation circuit and the output signal output from the operational amplifier, the optimum output Signal acquisition timing can be set.

In the capacitance detection circuit of the present invention, the sine wave generation circuit outputs a rectangular input signal obtained by converting a sine wave signal into a rectangular wave to the timing signal generation circuit, and the first one-shot circuit converts the rectangular input signal into the rectangular input signal. And generating the first timing signal that rises in synchronization with the rise timing of the output signal, and the second one-shot circuit generates a second timing signal that rises in synchronization with the fall timing of the first timing signal. The output time of the first timing signal and the second timing signal is less than a quarter cycle of the sine wave signal, and the sum of the output time of the first timing signal and the output time of the second timing signal Is preferably greater than a quarter period of the sine wave signal.
The output time in the present invention refers to the time during which a rectangular wave (square wave) timing signal is maintained at a high level.

In the present invention, the sine wave generation circuit generates a rectangular input signal having a rectangular wave (square wave) shape from the sine wave signal and outputs the rectangular input signal to the timing signal generation circuit. For example, when a rectangular input signal is generated from a sine wave signal output from a sine wave generation circuit using a Schmitt trigger inverter, a rectangular input signal that sets the sine wave signal to a high level or a low level with a predetermined voltage as a threshold value Is generated. At this time, the inverter outputs a signal having a level inverted from the input level. Therefore, the inverter outputs a rectangular input signal that rises when the input sine wave signal falls below the threshold. Therefore, by setting the threshold value to an intermediate value between the peak voltage and the bottom voltage of the sine wave signal, the rising timing of the rectangular input signal can be matched with the rising timing of the output signal output from the operational amplifier.
When a rectangular input signal is input, the first one-shot circuit outputs a rectangular wave first timing signal based on the rising timing or falling timing of the rectangular input signal. As described above, when the rising timing of the output signal output from the operational amplifier matches the rising timing of the rectangular input signal, the first timing signal is output at the rising timing of the rectangular input signal.
The second one-shot circuit outputs a second timing signal that rises with the falling timing of the first timing signal as a trigger.

  Here, in the present invention, the output period of the first timing signal, that is, the time for which the first timing signal is output is less than a quarter cycle of the sine wave signal, and the time for which the first timing signal is output. The output time of each timing signal is set so that the sum of the time with which the second timing signal is output is ¼ or more of the sine wave signal. Thus, when the time of each timing signal is set, the output signal of the peak voltage is output from the operational amplifier within the output time of the second timing signal. Therefore, the sample and hold circuit can acquire an appropriate signal value of the output signal by detecting the output signal within the output time of the second timing signal.

In the capacitance detection circuit of the present invention, it is preferable that the output time of the second timing signal is set to a time when the voltage of the output signal is 99% or more of the peak voltage.
In the present invention, since the output time of the second timing signal is set to a time when the voltage of the output signal is 99% or more of the peak voltage, the error of the detected signal value can be suppressed to less than 1%, Detection accuracy can be improved.

In the capacitance detection circuit of the present invention, it is preferable that the sine wave generation circuit is an oscillation circuit using a crystal resonator.
An oscillation circuit using a crystal resonator can output a sine wave signal having a highly accurate signal value and a highly accurate frequency. Therefore, an output signal having a stable frequency and signal value can be output from the operational amplifier, and the capacitance detection accuracy can be improved.

In the capacitance detection circuit of the present invention, it is preferable that the impedance element is a resistor.
In the present invention, since an element composed only of a resistor is used as the impedance element, the cost of the capacitance detection circuit can be reduced.

In the capacitance detection circuit of the present invention, it is preferable that the impedance element is an element in which a resistor and a capacitor are directly connected.
In the present invention, the impedance element is constituted by an element combining a resistor and a capacitor. In such a configuration, the impedance adjustment in the impedance element can be easily performed as compared with the case where the impedance element is configured by only the resistor. Thereby, the capacitance detection accuracy of the detection target capacitor can be improved.

  The optical module of the present invention includes a first substrate, a second substrate disposed to face the first substrate, a conductive first reflective film provided on the first substrate, and a second substrate. A conductive second reflection film provided opposite to the first reflection film via the gap between the reflection films, a gap changing unit for changing a gap amount of the gap between the reflection films, and the gap between the reflection films And a capacitance detection circuit for detecting the gap amount, wherein parasitic capacitance generated in the capacitance detection circuit in the detection of the gap amount by the capacitance detection circuit is removed.

  In the present invention, when the gap amount of the gap between the reflection films in the optical module is detected by the capacitance detection circuit, the parasitic capacitance generated in the capacitance detection circuit is removed. Therefore, the gap amount can be detected with high accuracy, and light with a desired wavelength can be extracted with high accuracy.

  The optical module of the present invention includes a first substrate, a second substrate disposed to face the first substrate, a conductive first reflective film provided on the first substrate, and a second substrate. A conductive second reflective film provided opposite to the first reflective film via a gap between the reflective films, a gap changing unit for changing a gap amount of the gap between the reflective films, and the first reflective film A sine wave generation circuit that outputs a sine wave signal, an inverting input terminal, a non-inverting input terminal, and an output terminal, the output terminal of the capacitor to be detected is connected to the inverting input terminal, and the non-inverting input terminal An operational amplifier connected to ground, a feedback circuit connected between the output terminal and the inverting input terminal of the operational amplifier and provided with an impedance element, and the sine wave signal output from the sine wave generation circuit A timing signal generation circuit that generates a predetermined timing signal, and a sample and hold circuit that is connected to the output terminal of the operational amplifier and acquires an output signal from the operational amplifier at a timing based on the timing signal. Features.

  In the present invention, a wavelength tunable interference filter (Fabry-Perot interferometer) can be configured by the first reflective film and the second reflective film, and the incident amount is changed by changing the gap amount between the reflective films by the gap changing unit. Light having a desired wavelength can be extracted from the light. At this time, in the present invention, the first reflective film and the second reflective film are used as the detection target capacitors, and the capacitance between the first reflective film and the second reflective film can be detected with high accuracy in the same manner as the above-described invention. Based on the detected capacitance, the gap amount of the gap between the reflective films can be accurately measured. Therefore, in the optical module of the present invention, it is possible to accurately extract light having a desired wavelength by driving the gap changing unit based on the measured gap amount of the gap between the reflective films.

  The optical module of the present invention includes a first substrate, a second substrate disposed to face the first substrate, a first reflective film provided on the first substrate, and a reflective substrate provided on the second substrate. A second reflective film provided opposite to the first reflective film via an inter-film gap; a gap changing portion for changing a gap amount of the inter-reflective film gap; and a first measurement electrode provided on the first substrate A second measurement electrode provided on the second substrate and facing the first measurement electrode via a predetermined gap; and a sine wave generation circuit that outputs a sine wave signal to the first measurement electrode; An operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, the inverting input terminal being connected to the output terminal of the detection target capacitor, and the non-inverting input terminal being connected to the ground, The output terminal And a feedback circuit connected between the inverting input terminals and provided with an impedance element, a timing signal generation circuit that generates a timing signal synchronized with the sine wave signal output from the sine wave generation circuit, and the operational amplifier A sample-and-hold circuit connected to an output terminal and acquiring an output signal from the operational amplifier at a timing based on the timing signal.

  In the present invention, a wavelength tunable interference filter can be configured by the first reflecting film and the second reflecting film as in the above-described invention, and the incident amount is changed by changing the gap amount of the gap between the reflecting films by the gap changing unit. Light having a desired wavelength can be extracted from the light. In addition, even when each of the reflective films does not have conductivity, such as when a dielectric multilayer film is used as the first reflective film and the second reflective film, the static of the first measurement electrode and the second measurement electrode. By detecting the capacitance, the gap amount of the gap between the reflective films can be measured.

  The electronic device according to the present invention includes a first substrate, a second substrate disposed to face the first substrate, a first reflective film provided on the first substrate, and a reflective substrate provided on the second substrate. A second reflection film provided opposite to the first reflection film via an interfilm gap, a gap changing unit for changing a gap amount of the gap between the reflection films, and outputting a sine wave signal to the first reflection film A sine wave generation circuit, an inverting input terminal, a non-inverting input terminal, and an output terminal. The output terminal of the detection target capacitor is connected to the inverting input terminal, and the non-inverting input terminal is connected to the ground. An operational amplifier, a feedback circuit connected between the output terminal and the inverting input terminal of the operational amplifier and provided with an impedance element, and a timing signal synchronized with the sine wave signal output from the sine wave generation circuit A timing signal generating circuit for generating, coupled to said output terminal of said operational amplifier, characterized in that anda sample and hold circuit for obtaining an output signal from the operational amplifier at a timing based on said timing signal.

As such an electronic device, for example, a spectrophotometer that takes out light of a desired wavelength by the first reflective film and the second reflective film and measures the amount of the extracted light, or a spectroscope that captures the dispersed image light. Examples thereof include a camera and a component analyzer that performs component analysis of a measurement target based on the dispersed light.
In the present invention, the capacitance between the first reflective film and the second reflective film can be detected with high accuracy, and a desired gap amount is set by setting the gap amount between the reflective films based on the detected capacitance. Wavelength light can be extracted with high accuracy. Therefore, various processes such as a spectroscopic measurement process, a spectral image imaging process, and a component analysis process can be accurately performed based on the extracted high-accuracy light, and the performance of the electronic apparatus can be improved.

  The electronic device according to the present invention includes a first substrate, a second substrate disposed to face the first substrate, a first reflective film provided on the first substrate, and a reflective substrate provided on the second substrate. A second reflective film provided opposite to the first reflective film via an inter-film gap; a gap changing portion for changing a gap amount of the inter-reflective film gap; and a first measurement electrode provided on the first substrate A second measurement electrode provided on the second substrate and facing the first measurement electrode via a predetermined gap; and a sine wave generation circuit that outputs a sine wave signal to the first measurement electrode; An operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, the inverting input terminal being connected to the output terminal of the detection target capacitor, and the non-inverting input terminal being connected to the ground, The output terminal and front A feedback circuit connected between the inverting input terminals and provided with an impedance element, a timing signal generation circuit that generates a timing signal synchronized with the sine wave signal output from the sine wave generation circuit, and the output terminal of the operational amplifier And a sample and hold circuit that acquires an output signal from the operational amplifier at a timing based on the timing signal.

  The present invention can be applied to a spectroscopic measurement device, a spectroscopic camera, a component analysis device, and the like, similarly to the above-described invention. Moreover, since the capacitance of the first measurement electrode and the second measurement electrode can be detected with high accuracy, the gap amount of the gap between the reflection films can be set based on the detected capacitance, and the desired wavelength Can be extracted with high accuracy. Therefore, various processes such as a spectroscopic measurement process, a spectral image imaging process, and a component analysis process can be accurately performed based on the extracted high-accuracy light, and the performance of the electronic apparatus can be improved.

The figure which shows the circuit structure of the capacity | capacitance detection circuit of 1st embodiment. The figure which shows the circuit structure of a sine wave generation circuit. The figure which shows the waveform of the detection signal acquired by the sine wave signal output from a sine wave generation circuit, the output signal output from an operational amplifier, the 2nd timing signal output from a timing signal generation circuit, and a sample and hold circuit. The figure which shows the structure of a timing signal generation circuit. The timing chart of an output signal, a rectangular input signal, a 1st timing signal, and a 2nd timing signal. The figure which shows an example of the circuit structure of a sample and hold circuit. The figure which shows the flow of an electric current when parasitic capacitance generate | occur | produces in a capacity | capacitance detection circuit. The block diagram which shows schematic structure of the spectrometer of 2nd embodiment. The circuit diagram which shows schematic structure of an optical module. The top view which shows schematic structure of a wavelength variable interference filter. Sectional drawing which cut the AA 'line of FIG. The top view of the wavelength variable interference filter in other embodiment. The figure which shows the Wien bridge oscillation circuit using RC oscillation which is another example of the sine wave generation circuit. The figure which shows the circuit using the microcomputer and low-pass filter which are the other examples of a sine wave generation circuit. Schematic which shows an example of the gas detection apparatus which is an electronic device provided with the optical module. The block diagram which shows the structure of the control system of the gas detection apparatus of FIG. The figure which shows schematic structure of the food analyzer which is an electronic device provided with the optical module. The schematic diagram which shows schematic structure of the spectroscopic camera which is an electronic device provided with the optical module. The figure which shows the example of the conventional capacitance detection circuit. The figure for demonstrating the influence of a parasitic capacitance in the conventional capacity | capacitance detection circuit. The figure for demonstrating the influence of a parasitic capacitance in the conventional capacity | capacitance detection circuit.

[First embodiment]
Hereinafter, a capacitance detection circuit according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a circuit configuration of the capacitance detection circuit according to the first embodiment.

[Overall configuration of capacitance detection circuit]
As shown in FIG. 1, the capacitance detection circuit 10 includes a sine wave generation circuit 11 that outputs an input signal V _I (sine wave signal) to an input terminal of the detection target capacitor Cx, and an output terminal of the detection target capacitor Cx. The operational amplifier 12 connected to the output terminal, the feedback circuit 13 provided between the output terminal and the inverting input terminal of the operational amplifier 12, the sample and hold circuit 14 connected to the output terminal of the operational amplifier 12, the sine wave generation circuit 11 and the sample A timing signal generation circuit 15 connected to the hold circuit 14 and a measurement processing unit 16 are provided.
The capacitance detection circuit 10 is a circuit for detecting the capacitance of the detection target capacitor Cx, and the measurement processing unit 16 determines the detection target capacitor Cx based on the signal value output from the sample and hold circuit 14. Measure the capacitance. The measurement of capacitance by the measurement processing unit 16 will be described later.

[Configuration of sine wave generation circuit]
FIG. 2 is a diagram illustrating a circuit configuration of the sine wave generation circuit 11.
In the present embodiment, as a sine wave generating circuit 11, as shown in FIG. 2, using a crystal oscillator circuit for outputting a predetermined input signal V _I using a piezoelectric effect of the crystal body.
Specifically, the sine wave generation circuit 11 includes an inverter 11A and a crystal resonator 11B connected between the input and output of the inverter 11A. In such sine wave generating circuit 11, a first output terminal 11C of the input terminal side of the inverter 11A, the output is the input signal V _I sinusoidal, from the second output end 11D of the output terminal side of the inverter 11A, rectangular A wave (square wave) input signal (rectangular input signal V _IR ) is output. The input signal V _I (sine wave) output from the first output terminal 11C is input to the detection target capacitor Cx, and the rectangular input signal V _IR output from the second output terminal 11D is input to the timing signal generation circuit 15. Is done.

Also, the inverter 11A on the basis of the threshold value of the input signal V _I to predetermined sorts to a high level and a low level, so-called Schmitt trigger type inverter is used. As this threshold value, an intermediate value V _IC ((V _Imax + V _Imin ) / 2) of the peak voltage V _Imax and the bottom voltage V _Imin of the input signal V _I (sine wave) is used. Further, when passing the input signal V _I to the inverter, the level value is inverted and outputted. Therefore, in this embodiment, when the input signal V _I is from the bottom voltage V _Imin to the intermediate value V _Ic , the rectangular input signal V _IR is at the high level, and the input signal V _I is at the intermediate value V _Ic to the peak voltage V _Imax . In some cases, it is low. In other words, the rectangular input signal V _IR rises from a low level to a high level at the intermediate value V _Ic when the sinusoidal input signal V _I changes from the peak voltage V _Imax to the bottom voltage V _Imin . After T / 4 period elapses (T is the period of the input signal _{V I),} when the input signal _{V I} is changed from the bottom voltage _{V Imin} to a peak voltage _{V Imax,} the intermediate value _{V Ic,} low level from the high level Stand up to.

[Configuration of operational amplifier and feedback circuit]
As shown in FIG. 1, the operational amplifier 12 has an inverting input terminal connected to the output terminal of the detection target capacitor Cx, and a non-inverting input terminal connected to GND. A sample and hold circuit 14 is connected to the output terminal of the operational amplifier 12 and a feedback circuit 13 is provided between the inverting input terminal.

As shown in FIG. 1, the feedback circuit 13 includes an impedance element 13A. As the impedance element 13A, an element to which a capacitor having a known resistance and capacitance is connected is used. Thus, in the impedance element 13A using a resistor and a capacitor, the impedance can be set to a desired value with high accuracy.
The impedance element 13A may be constituted only by a resistor. When the impedance element 13A configured only by such a resistor is used, the circuit configuration of the feedback circuit 13 can be simplified and the cost can be reduced.

Here, assuming that the impedance of the detection target capacitor Cx is Z _f and the impedance of the impedance element 13A is Z _i (fixed value), the input signal V _I input to the operational amplifier 12 and the output signal V output from the operational amplifier 12 _O (voltage) satisfies the relationship of the following formula (1).

[Equation 1]
V _O = −Z _f / Z _i · V _I (1)

3 shows an input signal V _I output from the sine wave generation circuit 11, an output signal V _O output from the operational amplifier 12, a second timing signal V _h1 described later output from the timing signal generation circuit 15, and a sample and FIG. 4 is a diagram illustrating a waveform of a detection signal acquired by a hold circuit 14.
As shown in FIGS. 3 and (1), the operational amplifier 12 inverts the phase of the input signal V _I and outputs an output signal V _O. Further, the output signal V _O of the operational amplifier 12 changes according to the ratio of the impedance Z _i of the impedance element 13A and the impedance Z _f of the detection target capacitor Cx, as shown in the equation (1).

[Configuration of timing signal generation circuit]
FIG. 4 is a diagram illustrating a configuration of the timing signal generation circuit 15. FIG. 5 is a timing chart of each signal.
As shown in FIG. 4, the timing signal generation circuit 15 includes a first one-shot circuit 15A and a second one-shot circuit 15B.

The first one-shot circuit 15A on the basis of the rectangular input signal V _IR input from the sine-wave generating circuit 11, and outputs a first timing signal V _h0.
As described above, the rectangular input signal V _IR rises from the low level to the high level at the intermediate value V _Ic when the input signal V _I changes from the peak voltage V _Imax to the bottom voltage V _Imin . Here, the phase of the output signal V _O output from the operational amplifier 12 is inverted with respect to the input signal V _I. Therefore, as shown in FIG. 5, the rectangular input signal V _IR is obtained when the output signal V _O of the operational amplifier 12 changes from the bottom voltage V _Omin to the peak voltage V _Omax , when the intermediate value V _OC ((V _Omax + V _Omin ) / In 2), the signal rises from the low level to the high level.
The first one-shot circuit 15A generates a first timing signal V _ho rising at the rising timing and the timing of the rectangular input signal V _IR. That is, the first timing signal V _ho rises from the low level to the high level in synchronization with the rising timing of the output signal V _O. The first one-shot circuit 15A, from the rising timing of the first timing signal V _ho predetermined time T1, and maintained a high level, lowers the first timing signal V _ho to a low level.

As shown in FIG. 5, the second one-shot circuit 15B has a second timing signal V _h1 that rises from a low level to a high level at the falling timing of the first timing signal V _ho output from the first one-shot circuit 15A. Is generated. The second one-shot circuit 15B, after maintaining a high level from rising timing a predetermined time T2 of the second timing signal V _h1, lowering the second timing signal V _h1 to a low level.

Here, the first one-shot circuit 15A and a second one-shot circuit 15B is (output time of the first timing signal V _h0 described in the present invention) first timing signal V _h0 time T1 is set to the high level and the The time T2 (the output time of the second timing signal _Vh1 described in the present invention) at which the second timing signal _Vh1 is set to the high level is set to a value satisfying the following equations (2) to (4).

[Equation 1]
T1 <T / 4 (2)
T2 <T / 4 (3)
T1 + T2> T / 4 (4)

In the above formula (2) ~ (4), T is the period of the input signal _{V I.} If the times T1 and T2 are set so as to satisfy the above conditions, a peak voltage appears in the output signal V _O output from the operational amplifier 12 within the time when the second timing signal V _h1 is set to the high level. . Therefore, the sample and hold circuit 14 obtains the output signal V _O during the time when the second timing signal V _h1 is set to the high level (the output time of the second timing signal V _h1 ), thereby It is possible to acquire a signal value with a small error.
As the time T2 to the second timing signal V _h1 is maintained at a high level, it is preferable that the output signal V _O from the operational amplifier 12 is set to a time equal to or greater than 99% of the peak voltage V _Omax.

[Configuration of sample and hold circuit]
FIG. 6 is a diagram illustrating an example of the circuit configuration of the sample and hold circuit 14.
As shown in FIG. 6, the sample and hold circuit 14 includes a switch S connected to the operational amplifier 12, an operational amplifier 14A connected to the switch S, and a hold capacitor 14B connected between the switch S and the operational amplifier 14A. Is provided. The output terminal of the switch S is connected to the non-inverting input terminal of the operational amplifier 14A, and a feedback circuit is formed between the output terminal of the operational amplifier 14A and the inverting input terminal of the operational amplifier 14A.
The connection state of the switch S is switched based on the second timing signal V _h1 output from the timing signal generation circuit 15. That is, when the second timing signal V _h1 from the timing signal generation circuit 15 is at a high level, the switch S switches to the ON state and connects the operational amplifier 12 and the operational amplifier 14A. On the other hand, when the second timing signal V _h1 is at a low level, the operational amplifier 12 and the operational amplifier 14A are disconnected by switching to the OFF state.

In such a sample and hold circuit 14, when the switch S is turned on, the output signal V _O output from the operational amplifier 12 is applied to the hold capacitor 14B. Therefore, even if the switch S is turned OFF, hold capacitor 14B holds the voltage of the output signal _{V O,} the operational amplifier 14A performs a DC output _{V S.} Therefore, the detection signal V _S (= V _Omax ) detected (acquired) by the sample and hold circuit 14 is a constant DC signal as shown in FIG.
That is, the sample and hold circuit 14 holds the output signal V _O (V _Omax ) and outputs it as the detection signal V _S during the output time when the high level signal value is output as the second timing signal V _h1 .
In the present embodiment, the operational amplifier 14A is used as a buffer with a gain of 1. However, the output range may be set so that the voltage range becomes a desired range by amplifying the output.

[Influence of parasitic capacitance]
Next, in the capacitance detection circuit 10 as described above, the influence when parasitic capacitances Ca and Cb are generated between the ground (GND) on the input / output end side of the detection target capacitor Cx will be described.
FIG. 7 is a diagram illustrating a current flow when parasitic capacitance is generated in the capacitance detection circuit 10.
As shown in FIG. 7, the detected capacitor Cx, with the input of the input signal V _I, current I _S flows, is input to the operational amplifier 12. On the other hand, when the parasitic capacitance Ca is generated on the input terminal side of the detection target capacitor Cx, the current _Ip flows through the parasitic capacitance Ca, but does not flow through the operational amplifier 12 because the current _Ip flows through GND.
The non-inverting input terminal of the operational amplifier 12 is connected to GND. Therefore, the potential of the inverting input terminal of the operational amplifier 12 becomes the reference potential (GND level) due to the imaginary short of the operational amplifier 12. Therefore, even if the parasitic capacitance Cb occurs between the output end of the detection target capacitor Cx and the ground, the input / output ends of the parasitic capacitance Cb have the same potential and no current flows.
As described above, in the capacitance detection circuit 10 of the present embodiment, even when the parasitic capacitances Ca and Cb are generated between the input and output terminals of the detection target capacitor Cx and the ground, the detection target capacitor Cx. and current _{I S} flowing through, equal to the current _{I f} flowing through the impedance element 13A _(I S _{= I} F), the aforementioned equation (1) is maintained, there is no influence of the parasitic capacitance.

[Measurement Processing Unit Operation]
When the detection signal V _S (the peak voltage V _OMAX of the output signal V _O ) acquired by the sample and hold circuit 14 is input to the measurement processing unit 16, the detection target capacitor Cx is based on the above-described equation (1). calculating the impedance Z _i, further calculates the electrostatic capacitance C of the detected capacitor Cx.

[Operational effects of this embodiment]
As described above, the capacitance detection circuit 10 of this embodiment includes a sine wave generating circuit 11 outputs the input signal V _I to the input terminal of the detection target capacitor Cx, to the output terminal of the detection target capacitor Cx is an inverting input terminal The operational amplifier 12 whose non-inverting input terminal is connected to GND, the output terminal of the operational amplifier 12 and the inverting input terminal are connected, the feedback circuit 13 including the impedance element 13A, and the output signal V _O output from the operational amplifier 12 And a sample and hold circuit 14 for detection. The capacitance detection circuit 10 includes a timing signal generation circuit 15 that outputs a second timing signal V _h1 that is synchronized with the input signal V _I of the sine wave generation circuit 11, and the sample and hold circuit 14 includes a second timing signal V _h. the signal value of the high level to obtain an output signal V _O which is input at the time is output as _h1.

In the capacitance detection circuit 10 having such a configuration, even when the parasitic capacitance Ca is generated between the ground on the input terminal side of the detection target capacitor Cx, the current _Ip flowing through the parasitic capacitance Ca can be supplied to the GND. Even when a parasitic capacitance Cb is generated between the output terminal of the detection target capacitor Cx and the ground, no current flows through the parasitic capacitance Cb due to an imaginary short of the operational amplifier 12. Accordingly, the current flowing through the operational amplifier 12, the current _{I f} flowing current _{I S} next to the detected capacitor Cx, the impedance element 13A is the same as current _{I s.} Therefore, the detection signal V _S detected by the sample and hold circuit 14 does not include the signal value of the error component based on the parasitic capacitance, and the accurate electrostatic capacitance of the detection target capacitor Cx is determined based on the detection signal V _S. Capacitance can be measured.

  Further, the switch provided in the capacitance detection circuit 10 is only the switch S provided in the sample-and-hold circuit 14, and the control signal for controlling the switch S can be reduced. Therefore, in designing the circuit, the influence of the crosstalk caused by the control signal can be reduced, so that the configuration of the circuit board can be simplified.

In the present embodiment, the timing signal generation circuit 15 includes a first one-shot circuit 15A and a second one-shot circuit 15B. The first one-shot circuit 15A outputs a first timing signal V _h0 synchronized with the input signal V _I, the second one-shot circuit 15B, based on the first timing signal V _h0, the peak voltage from the operational amplifier 12 A second timing signal V _h1 synchronized with the timing at which V _Omax is output is output.
Thus, even when the output signal V _O output from the operational amplifier 12 is out of phase with the input signal V _I output from the sine wave generation circuit 11 by a half cycle, the output timing of the peak voltage V _Omax The second timing signal V _h1 can be output at the optimum timing corresponding to the above, and the detection signal V _S can be obtained with high accuracy in the sample and hold circuit 14.

Moreover, sine-wave generating circuit 11, the inverter 11A, and outputs the timing signal generating circuit 15 generates a rectangular input signal V _IR from the input signal V _I of the sine wave. The first one-shot circuit 15A generates a first timing signal V _h0 which rises synchronously with the rise timing of the rectangular input signal V _IR, the second one-shot circuit 15B is standing in the first timing signal V _h0 A second timing signal _Vh1 that rises in synchronization with the downlink timing is generated. Further, the first one-shot circuit 15A and the second one-shot circuit 15B, as shown in the equations (2) to (4), output time T1, when high-level signals are output as the respective timing signals V _h0 and V _h1 the T2, respectively, is set to less than 1/4 of the period T of the input signal _{V I.} The first one-shot circuit 15A and a second one-shot circuit 15B, the sum of these output time (T1 + T2) is to be larger than 1/4 of the period of the input signal _{V I,} set each time T1, T2 To do.
Such timing signal by generating a time to peak voltage V _Omax is output as an output signal V _O, the second timing signal V _h1 can be overlapped time T2 to the high level. Therefore, the sample and hold circuit 14 can acquire the peak voltage V _Omax with high accuracy by acquiring the output signal VO based on the second timing signal V _h1 .
Further, the time when the second timing signal V _h1 is set to the high level is set to a time when the voltage of the output signal V _O is 99% or more of the peak voltage V _Omax , so that the detection signal V _S is detected. The error can be suppressed to less than 1%, and the detection accuracy can be further improved.

In the present embodiment, as the sine wave generation circuit 11, a crystal oscillation circuit using a crystal resonator 11B is used.
Such a crystal oscillation circuit can output the input signal V _I having a desired signal value at a highly accurate frequency. Therefore, the output signal V _O output from the operational amplifier 12 also has stable signal characteristics, and the capacitance detection accuracy can be improved.

[Second Embodiment]
Next, a second embodiment of the present invention will be described based on the drawings.
FIG. 8 is a block diagram illustrating a schematic configuration of a spectroscopic measurement apparatus that is an electronic apparatus according to the second embodiment.
FIG. 9 is a circuit diagram showing a schematic configuration of the optical module of the second embodiment.

As shown in FIG. 8, the spectroscopic measurement device 20 of the second embodiment is a device that analyzes the light intensity of each wavelength in the measurement target light reflected by the measurement target X and measures the spectral spectrum.
As shown in FIG. 8, the spectroscopic measurement apparatus 20 includes a wavelength variable interference filter 5, a detector 21 (detection unit), an IV converter 22, an amplifier 23, an A / D converter 24, and a voltage. A control circuit 25, a capacitance detection circuit 10, and a control circuit unit 30 are provided.

The detector 21 receives the light transmitted through the variable wavelength interference filter 5 and outputs a detection signal (current) corresponding to the light intensity of the received light.
The IV converter 22 converts the detection signal input from the detector 21 into a voltage value and outputs the voltage value to the amplifier 23.
The amplifier 23 amplifies a voltage (detection voltage) corresponding to the detection signal input from the IV converter 22.
The A / D converter 24 converts the detection voltage (analog signal) input from the amplifier 23 into a digital signal and outputs the digital signal to the control circuit unit 30.
The voltage control circuit 25 applies a drive voltage to an electrostatic actuator 56 described later of the wavelength variable interference filter 5 based on the control of the control circuit unit 30.

[Configuration of wavelength tunable interference filter]
Here, the wavelength variable interference filter 5 incorporated in the spectrometer 20 will be described below. FIG. 10 is a plan view showing a schematic configuration of the variable wavelength interference filter. 11 is a cross-sectional view taken along line AA ′ of FIG.
As shown in FIGS. 10 and 11, the variable wavelength interference filter 5 includes a fixed substrate 51 that is the first substrate of the present invention and a movable substrate 52 that is the second substrate of the present invention. The fixed substrate 51 and the movable substrate 52 are each formed of, for example, various types of glass such as soda glass, crystalline glass, quartz glass, lead glass, potassium glass, borosilicate glass, and non-alkali glass, or crystal. . The fixed substrate 51 and the movable substrate 52 include a bonding film in which the first bonding portion 513 of the fixed substrate 51 and the second bonding portion 523 of the movable substrate are formed of, for example, a plasma polymerization film mainly containing siloxane. By being joined by 53, it is comprised integrally.

The fixed substrate 51 is provided with a fixed reflective film 54 constituting the first reflective film of the present invention, and the movable substrate 52 is provided with a movable reflective film 55 constituting the second reflective film of the present invention. The fixed reflection film 54 and the movable reflection film 55 are disposed to face each other via the inter-reflection film gap G1. The wavelength variable interference filter 5 is provided with an electrostatic actuator 56 that is used to adjust (change) the gap amount of the inter-reflection film gap G1. The electrostatic actuator 56 corresponds to a gap changing unit in the present invention. The electrostatic actuator 56 includes a fixed electrode 561 provided on the fixed substrate 51 and a movable electrode 562 provided on the movable substrate 52. These fixed electrode 561 and movable electrode 562 are opposed to each other through an interelectrode gap. Here, the electrodes 561 and 562 may be provided directly on the substrate surfaces of the fixed substrate 51 and the movable substrate 52, respectively, or may be provided via other film members. Here, the gap amount of the interelectrode gap is larger than the gap amount of the inter-reflection film gap G1.
Further, in the plan view as shown in FIG. 10 in which the wavelength variable interference filter 5 is viewed from the thickness direction of the fixed substrate 51 (movable substrate 52), the plane center point O of the fixed substrate 51 and the movable substrate 52 is the fixed reflection film. 54 and the center point of the movable reflective film 55 and the center point of the movable part 521 described later.
In the following description, the wavelength tunable interference filter 5 was seen from a plan view seen from the thickness direction of the fixed substrate 51 or the movable substrate 52, that is, from the stacking direction of the fixed substrate 51, the bonding film 53, and the movable substrate 52. The plan view is referred to as a filter plan view.

(Configuration of fixed substrate)
In the fixed substrate 51, an electrode arrangement groove 511 and a reflection film installation part 512 are formed by etching. The fixed substrate 51 is formed to have a thickness larger than that of the movable substrate 52, and the fixed substrate is caused by electrostatic attraction when a voltage is applied between the fixed electrode 561 and the movable electrode 562 or internal stress of the fixed electrode 561. There is no 51 deflection.
Further, notches 514 are formed at the apexes C2 and C4 of the fixed substrate 51. When the wavelength variable interference filter 5 is viewed from the fixed substrate 51 side, a movable electrode pad 564P and a second measurement lead to be described later are used. The electrode 566 is exposed.

The electrode arrangement groove 511 is formed in an annular shape centering on the plane center point O of the fixed substrate 51 in the filter plan view. The reflection film installation part 512 is formed so as to protrude from the center part of the electrode arrangement groove 511 toward the movable substrate 52 in the plan view. The groove bottom surface of the electrode arrangement groove 511 is an electrode installation surface 511A on which the fixed electrode 561 is arranged. In addition, the protruding front end surface of the reflection film installation portion 512 is a reflection film installation surface 512A.
In addition, the fixed substrate 51 is provided with electrode extraction grooves 511B extending from the electrode arrangement grooves 511 toward the vertices C1, C2, C3, and C4 of the outer peripheral edge of the fixed substrate 51.

A fixed electrode 561 is provided on the electrode installation surface 511 </ b> A of the electrode arrangement groove 511. More specifically, the fixed electrode 561 is provided in a region of the electrode installation surface 511 </ b> A that faces a movable electrode 562 of the movable portion 521 described later. The fixed electrode 561 is formed in a C shape having an opening at a position facing the vertex C3. In addition, an insulating film for ensuring insulation between the fixed electrode 561 and the movable electrode 562 may be stacked over the fixed electrode 561.
The fixed substrate 51 is provided with a fixed extraction electrode 563 extending from the outer peripheral edge of the fixed electrode 561 in the direction of the vertex C1. The extended leading end portion of the fixed extraction electrode 563 (the portion located at the vertex C1 of the fixed substrate 51) constitutes a fixed electrode pad 563P connected to the voltage control circuit 25.
In the present embodiment, a configuration in which one fixed electrode 561 is provided on the electrode installation surface 511A is shown. For example, a configuration in which two concentric circles centered on the plane center point O are provided (double electrode configuration). ) Etc.

As described above, the reflection film installation portion 512 is formed in a substantially cylindrical shape that is coaxial with the electrode arrangement groove 511 and has a smaller diameter than the electrode arrangement groove 511, and faces the movable substrate 52 of the reflection film installation portion 512. The reflective film installation surface 512A is provided.
As shown in FIG. 11, a conductive fixed reflection film 54 is installed in the reflection film installation portion 512. As the fixed reflective film 54, for example, a metal film such as Ag or an alloy film such as an Ag alloy can be used.

  The fixed substrate 51 is provided with a first measurement lead electrode 565 that is connected to the outer peripheral edge of the fixed reflective film 54 and extends in the direction of the vertex C3. The first measurement lead electrode 565 passes through the C-shaped opening of the fixed electrode 561 and the electrode lead groove 511 </ b> B and extends to the vertex C <b> 3 of the fixed substrate 51. In addition, the extended leading end portion of the first measurement lead electrode 565 (the portion located at the vertex C3 of the fixed substrate 51) is connected to the sine wave generation circuit 11 of the capacitance detection circuit 10.

  Further, an antireflection film may be formed at a position corresponding to the fixed reflection film 54 on the light incident surface of the fixed substrate 51 (the surface on which the fixed reflection film 54 is not provided). This antireflection film can be formed by alternately laminating low refractive index films and high refractive index films, and reduces the reflectance of visible light on the surface of the fixed substrate 51 and increases the transmittance.

  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 extraction groove 511B are not formed by etching constitutes the first joint portion 513.

(Configuration of movable substrate)
The movable substrate 52 includes a circular movable portion 521 centered on the plane center point O in the filter plan view as shown in FIG. 10, a holding portion 522 that is coaxial with the movable portion 521 and holds the movable portion 521, A substrate outer peripheral portion 525 provided outside the holding portion 522.
Further, as shown in FIG. 10, the movable substrate 52 has a notch 524 corresponding to the vertices C1 and C3, and is fixed when the wavelength variable interference filter 5 is viewed from the movable substrate 52 side. The electrode pad 563P and the first measurement lead electrode 565 are exposed.

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 larger than at least the diameter of the outer peripheral edge of the reflection film installation surface 512A in the filter plan view. The movable part 521 is provided with a movable electrode 562 and a movable reflective film 55.
Similar to the fixed substrate 51, an antireflection film may be formed on the surface of the movable portion 521 opposite to the fixed substrate 51. Such an antireflection film can be formed by alternately laminating a low refractive index film and a high refractive index film, reducing the reflectance of visible light on the surface of the movable substrate 52 and increasing the transmittance. Can be made.

  The movable electrode 562 is provided to face the fixed electrode 561 with an interelectrode gap interposed therebetween. The movable electrode 562 is formed in a C shape having an opening at a position facing the vertex C4. The movable substrate 52 is provided with a movable extraction electrode 564 extending from the outer peripheral edge of the movable electrode 562 toward the vertex C2 of the movable substrate 52. The extended leading end portion of the movable extraction electrode 564 (the portion located at the vertex C2 of the movable substrate 52) constitutes a movable electrode pad 564P connected to the voltage control circuit 25.

The movable reflective film 55 is provided at the center of the movable surface 521A of the movable part 521 so as to face the fixed reflective film 54 with the gap G1 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.
In the present embodiment, as described above, an example in which the gap amount of the interelectrode gap is larger than the gap amount of the inter-reflection film gap G1 is shown, but the present invention is not limited to this. For example, when using infrared rays or far infrared rays as the measurement target light, the gap amount of the gap G1 between the reflection films may be larger than the gap amount of the gap between the electrodes depending on the wavelength range of the measurement target light.

  The movable substrate 52 is provided with a second measurement lead electrode 566 connected to the outer peripheral edge of the movable reflective film 55 and extending in the direction of the vertex C4. The second measurement lead electrode 566 passes through the C-shaped opening of the movable electrode 562 and extends to the vertex C4 of the movable portion 521. In addition, the extended leading end portion (the portion located at the vertex C4 of the movable substrate 52) of the second measurement lead electrode 566 is connected to the inverting input terminal of the operational amplifier 12 in the capacitance detection circuit 10.

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 part 522 is easier to bend than the movable part 521, and the movable part 521 can be displaced toward the fixed substrate 51 by a slight electrostatic attraction. At this time, since the movable portion 521 has a thickness dimension larger than that of the holding portion 522 and becomes rigid, even when the holding portion 522 is pulled toward the fixed substrate 51 by electrostatic attraction, the shape of the movable portion 521 changes. Absent. Therefore, the movable reflective film 55 provided on the movable portion 521 is not bent, and the fixed reflective film 54 and the movable reflective film 55 can be always maintained in a parallel state.
In this 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 plane center point O are provided. And so on.

  As described above, the substrate outer peripheral portion 525 is provided outside the holding portion 522 in the filter plan view. The surface of the substrate outer peripheral portion 525 that faces the fixed substrate 51 includes a second joint portion 523 that faces the first joint portion 513.

[Driving wavelength variable interference filter]
In the wavelength variable interference filter 5 as described above, the fixed electrode pad 563P and the movable electrode pad 564P are connected to the voltage control circuit 25, respectively. Therefore, when the voltage is applied between the fixed electrode 561 and the movable electrode 562 by the voltage control circuit 25, the movable portion 521 is displaced toward the fixed substrate 51 by electrostatic attraction. Thereby, it is possible to change the gap amount of the gap G1 between the reflection films to a predetermined amount.

Here, in this embodiment, as shown in FIG. 9, the fixed reflective film 54 is connected to the sine wave generating circuit 11 of the capacitance detection circuit 10 via the first measurement extraction electrode 565, and the movable reflective film 55 is the first. The second measurement lead electrode 566 is connected to the operational amplifier 12 of the capacitance detection circuit 10. Therefore, the fixed reflective film 54 and the movable reflective film 55 can be regarded as Cx of the first embodiment, and the detection signal V _S corresponding to the electrostatic capacitances of the fixed reflective film 54 and the movable reflective film 55 is sampled and held. It can be output from the circuit 14.
Thus, the control circuit unit 30, based on the detection signal V _S, the electrostatic capacitance of the fixed reflection film 54 and the movable reflective layer 55 can be accurately calculated, precise gap distance of the gap G1 between the reflective films Can be calculated.

[Configuration of control circuit section]
Returning to FIG. 8, the control circuit unit 30 of the spectrometer 20 will be described.
The control circuit unit 30 corresponds to the measurement control unit of the present invention, and is configured by combining, for example, a CPU and a memory, and controls the overall operation of the spectroscopic measurement apparatus 20. As shown in FIG. 8, the control circuit unit 30 includes a gap measuring unit 31, a filter driving unit 32, and a light measuring unit 33. In addition, the control circuit unit 30 includes a storage unit 34 that stores various data. The storage unit 34 stores V-λ data indicating the relationship of the wavelength of light transmitted through the wavelength variable interference filter 5 with respect to the drive voltage applied to the electrostatic actuator 56 of the wavelength variable interference filter 5. In addition, the storage unit 34 stores V _S -G data indicating the relationship of the gap amount of the inter-reflective film gap G 1 with respect to the detection signal V _S acquired by the capacitance detection circuit 10. As the V _S -G data, the wavelength of light transmitted through the wavelength variable interference filter 5 may be stored with respect to the gap amount of the inter-reflection film gap G1.

When the detection signal V _S is input from the sample and hold circuit 14 of the capacitance detection circuit 10, the gap measurement unit 31 receives the gap between the reflection films G 1 based on the V _S -G data stored in the storage unit 34. Measure the amount.
In the present embodiment, the gap measuring unit 31 shows an example in which the gap amount of the inter-reflective film gap G1 is measured based on the V _S -G data stored in advance in the storage unit 34. As in the measurement processing unit 16 of the embodiment, the impedance and capacitance of the capacitor constituted by the fixed reflective film 54 and the movable reflective film 55 are calculated from the equation (1) and the detection signal V _S , and are calculated from the capacitance. You may calculate the gap amount of the gap G1 between reflection films.

The filter drive unit 32 sets a drive voltage for setting the wavelength of light extracted by the wavelength variable interference filter 5, controls the voltage control circuit 25, and sends the drive voltage to the electrostatic actuator 56 of the wavelength variable interference filter 5. Apply.
Here, the filter drive unit 32 reads the drive voltage corresponding to the target wavelength to be measured from the V-λ data stored in the storage unit 34, and applies the read drive voltage to the electrostatic actuator 56.
Further, when the gap measuring unit 31 measures the gap amount of the inter-reflective film gap G1, the filter driving unit 32 determines the gap amount of the inter-reflective film gap G1 with respect to the set voltage and the inter-reflective film gap obtained by the measurement. A difference value from the gap amount of G1 is calculated. When the calculated difference value is equal to or greater than the predetermined threshold, the filter driving unit 32 transmits light having a desired wavelength based on the gap amount of the inter-reflection film gap G1 measured by the gap measuring unit 31. The voltage to be applied to the electrostatic actuator 56 is corrected so as to be in the state.

  The light measurement unit 33 measures the amount of light received from the detector 21 and stores the measurement result in the storage unit 34. The light measurement unit 33 measures the spectral characteristics of the measurement target light based on the measurement result stored in the storage unit 34.

[Operational effects of the second embodiment]
In the spectroscopic measurement apparatus 20 of this embodiment, the fixed reflection film 54 of the wavelength variable interference filter 5 is connected to the sine wave generation circuit 11 of the capacitance detection circuit 10, and the movable reflection film 55 is connected to the operational amplifier 12 of the capacitance detection circuit 10. The Therefore, similarly to the above-described invention, the capacitance detection circuit 10 outputs the accurate detection signal V _S corresponding to the capacitance to the control circuit unit 30 with the fixed reflection film 54 and the movable reflection film 55 as the detection target capacitors. be able to.
Therefore, the gap measuring unit 31 can accurately measure the gap amount of the inter-reflection film gap G1, and corrects the voltage applied to the electrostatic actuator 56 based on the measured gap amount, thereby measuring the object to be measured. Light having a desired wavelength can be extracted from light with high accuracy.

[Other Embodiments]
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.
For example, in the second embodiment, the conductive fixed reflection film 54 and the movable reflection film 55 are used as the detection target capacitor Cx, and the gap amount of the gap G1 between the reflection films is measured. However, the present invention is not limited to this.
For example, in the case of using a dielectric multilayer film in which, for example, the high refractive layer is TiO ₂ and the low refractive layer is SiO ₂ as the fixed reflective film 54 and the movable reflective film 55, as shown in FIG. It is good also as a structure provided with the electrode for an electric capacity measurement.
FIG. 12 is a plan view of a wavelength tunable interference filter according to another embodiment.
As shown in FIG. 12, the fixed substrate 51 is provided with, for example, an annular first measurement electrode 567 on the outer peripheral side of the fixed reflection film 54 on the reflection film installation portion 512. The first measurement electrode 567 includes a first measurement extraction electrode 567P extending toward the apex C3, and the extension tip of the first measurement extraction electrode 567P is connected to the sine wave generation circuit 11 of the capacitance detection circuit 10. Connected.
In addition, the movable substrate 52 includes a second measurement electrode 568 facing the first measurement electrode 567 between the movable reflective film 55 and the movable electrode 562. The second measurement electrode 568 includes a second measurement lead electrode 568P extending toward the vertex C4, and the extension tip of the second measurement lead electrode 568P is connected to the operational amplifier 12 of the capacitance detection circuit 10. .
Even in such a configuration, as in the second embodiment, the first measurement electrode 567 and the second measurement electrode 568 are used as the detection target capacitor Cx, and an accurate detection signal V _S corresponding to the capacitance is detected. Therefore, the accurate gap amount of the gap G1 between the reflection films can be measured.

  In the second embodiment, the example in which the first measurement extraction electrode 565 is connected to the sine wave generation circuit 11 and the second measurement extraction electrode 566 is connected to the operational amplifier 12 is shown, but the present invention is not limited to this. . For example, the first measurement extraction electrode 565 may be connected to the operational amplifier 12 and the second measurement extraction electrode 566 may be connected to the sine wave generation circuit 11. The wavelength variable interference filter 5 shown in FIG. 12 is the same, and the first measurement extraction electrode 567P may be connected to the sine wave generation circuit 11, and the second measurement extraction electrode 568P may be connected to the operational amplifier 12.

In the above embodiment, the crystal oscillation circuit is illustrated as the sine wave generation circuit 11, but the present invention is not limited to this. For example, a ceramic oscillation circuit using a ceramic resonator may be used instead of the crystal resonator 11B.
Further, other oscillation circuits as shown in FIGS. 13 and 14 may be used.
The example shown in FIG. 13 is a Wien bridge oscillation circuit using RC oscillation. Further, in the example shown in FIG. 14, a rectangular wave (rectangular input signal V _IR ) having a desired cycle and duty ratio is generated by a microcomputer or the like, and a harmonic component is cut by a low-pass filter, whereby a sine wave input signal V _I Is an example of generating.

In the above embodiment, by using a crystal oscillator circuit having an inverter 11A as a sine wave generating circuit 11, at the fall timing of the input signal V _I, a rectangular input signal V _IR rising from a low level to a high level is output However, the present invention is not limited to this. For example, the generated input signal V _I, in the case of converting to a rectangular input signal V _IR by the A / D conversion circuit and the like, a rectangular input signal V _IR rising from a low level to a high level at the rising edge of the input signal V _I It is formed.
In this case, the first one-shot circuit 15A in synchronization with the falling edge of the rectangular input signal V _IR, may generate a first timing signal V _h0 which rises from the low level to the high level.

In the above-described embodiment, the example in which the timing signal generation circuit 15 includes the first one-shot circuit 15A and the second one-shot circuit 15B has been described, but the present invention is not limited to this. For example, a timing signal for acquiring the output signal V ₀ may be generated by three or more one-shot circuits.

In the second embodiment, the electrostatic actuator 56 that varies the gap amount of the inter-reflective film gap G1 by applying a voltage is exemplified as the gap amount changing unit of the wavelength tunable interference filter 5. However, the present invention is not limited to this.
For example, instead of the fixed electrode 561, a first dielectric coil may be arranged, and a dielectric actuator in which a second dielectric coil or a permanent magnet is arranged instead of the movable electrode 562 may be used.
Further, a piezoelectric actuator may be used instead of the electrostatic actuator 56. In this case, for example, the lower electrode layer, the piezoelectric film, and the upper electrode layer are stacked on the holding unit 522, and the voltage applied between the lower electrode layer and the upper electrode layer is varied as an input value, thereby expanding and contracting the piezoelectric film. Thus, the holding portion 522 can be bent.

Moreover, although the spectroscopic measurement apparatus 20 was illustrated in 2nd embodiment as an electronic device of this invention, the optical module and electronic device of this invention can be used by various field | areas.
For example, it can be used as a light-based system for detecting the presence of a specific substance. As such a system, for example, an in-vehicle gas leak detector that detects a specific gas with high sensitivity by adopting a spectroscopic measurement method using the variable wavelength interference filter of the present invention, or a photoacoustic rare gas detection for a breath test. A gas detection device such as a vessel can be exemplified.
An example of such a gas detection device will be described below with reference to the drawings.

FIG. 15 is a schematic diagram illustrating an example of a gas detection device including an optical module.
FIG. 16 is a block diagram showing a configuration of a control system of the gas detection device of FIG.
As illustrated in FIG. 15, the gas detection device 100 includes a sensor chip 110, a flow path 120 including a suction port 120A, a suction flow path 120B, a discharge flow path 120C, and a discharge port 120D, a main body 130, It is configured with.
The main body unit 130 includes a sensor unit cover 131 having an opening through which the flow channel 120 can be attached, a discharge unit 133, a housing 134, an optical unit 135, a filter 136, a wavelength variable interference filter 5, a light receiving element 137, and the like. And a control unit 138 that processes the detected signal and controls the detection unit, a power supply unit 139 that supplies power, and the like. Note that a filter as shown in FIG. 12 may be used as the variable wavelength interference filter 5. The optical unit 135 emits light, and a beam splitter 135B that reflects light incident from the light source 135A toward the sensor chip 110 and transmits light incident from the sensor chip toward the light receiving element 137. And lenses 135C, 135D, and 135E.
As shown in FIG. 16, an operation panel 140, a display unit 141, a connection unit 142 for interfacing with the outside, and a power supply unit 139 are provided on the surface of the gas detection device 100. When the power supply unit 139 is a secondary battery, a connection unit 143 for charging may be provided.
Further, as shown in FIG. 16, the control unit 138 of the gas detection apparatus 100 controls a signal processing unit 144 configured by a CPU or the like, a light source driver circuit 145 for controlling the light source 135A, and the variable wavelength interference filter 5. Voltage control unit 146, a light receiving circuit 147 that receives a signal from the light receiving element 137, a sensor chip detection that reads a code of the sensor chip 110 and receives a signal from a sensor chip detector 148 that detects the presence or absence of the sensor chip 110 The circuit 149, the discharge driver circuit 150 for controlling the discharge means 133, the fixed reflection film 54 and the movable reflection film 55 of the wavelength variable interference filter 5 (if the wavelength variable interference filter 5 shown in FIG. 12 is used, the first measurement electrode 567 And the capacitance detection circuit 10 for detecting the capacitance of the second measurement electrode 568), etc. It is provided.

Next, operation | movement of the above gas detection apparatuses 100 is demonstrated below.
A sensor chip detector 148 is provided inside the sensor unit cover 131 at the upper part of the main body unit 130, and the sensor chip detector 148 detects the presence or absence of the sensor chip 110. When the signal processing unit 144 detects the detection signal from the sensor chip detector 148, the signal processing unit 144 determines that the sensor chip 110 is attached, and displays a display signal for displaying on the display unit 141 that the detection operation can be performed. put out.

  For example, when the operation panel 140 is operated by the user and an instruction signal to start the detection process is output from the operation panel 140 to the signal processing unit 144, the signal processing unit 144 first sends the signal processing unit 144 to the light source driver circuit 145. A light source activation signal is output to activate the light source 135A. When the light source 135A is driven, laser light having a single wavelength and stable linear polarization is emitted from the light source 135A. The light source 135A includes a temperature sensor and a light amount sensor, and the information is output to the signal processing unit 144. When the signal processing unit 144 determines that the light source 135A is stably operating based on the temperature and light quantity input from the light source 135A, the signal processing unit 144 controls the discharge driver circuit 150 to operate the discharge unit 133. Thereby, the gas sample containing the target substance (gas molecule) to be detected is guided from the suction port 120A to the suction channel 120B, the sensor chip 110, the discharge channel 120C, and the discharge port 120D. The suction port 120A is provided with a dust removal filter 120A1 to remove relatively large dust, some water vapor, and the like.

The sensor chip 110 is a sensor that incorporates a plurality of metal nanostructures and uses localized surface plasmon resonance. In such a sensor chip 110, an enhanced electric field is formed between the metal nanostructures by the laser light, and when gas molecules enter the enhanced electric field, Raman scattered light and Rayleigh scattered light including information on molecular vibrations are generated. Occur.
These Rayleigh scattered light and Raman scattered light enter the filter 136 through the optical unit 135, and the Rayleigh scattered light is separated by the filter 136, and the Raman scattered light enters the wavelength variable interference filter 5. Then, the signal processing unit 144 controls the voltage control unit 146 to adjust the voltage applied to the wavelength variable interference filter 5, and causes the wavelength variable interference filter 5 to split the Raman scattered light corresponding to the gas molecule to be detected. . At this time, the signal processing unit 144 measures the gap amount of the gap G1 between the reflection films based on the detection signal V _S detected by the capacitance detection circuit 10, and the voltage control unit 146 applies it to the electrostatic actuator 56. Correct the voltage to an appropriate value. When the dispersed light is received by the light receiving element 137, a light reception signal corresponding to the amount of received light is output to the signal processing unit 144 via the light receiving circuit 147.
The signal processing unit 144 compares the spectrum data of the Raman scattered light corresponding to the gas molecule to be detected obtained as described above and the data stored in the ROM, and determines whether or not the target gas molecule is the target gas molecule. To determine the substance. Further, the signal processing unit 144 displays the result information on the display unit 141 or outputs the result information from the connection unit 142 to the outside.

  15 and 16 exemplify the gas detection device 100 that performs gas detection from the Raman scattered light obtained by spectrally dividing the Raman scattered light by the wavelength variable interference filter 5. You may use as a gas detection apparatus which specifies gas classification by detecting the light absorbency of. In this case, a gas sensor that allows gas to flow into the sensor and detects light absorbed by the gas in the incident light is used as the optical module of the present invention. A gas detection device that analyzes and discriminates the gas flowing into the sensor by such a gas sensor is an electronic apparatus of the present invention. Even in such a configuration, it is possible to detect a gas component using the wavelength variable interference filter.

In addition, the system for detecting the presence of a specific substance is not limited to the detection of the gas as described above, but a non-invasive measuring device for saccharides by near-infrared spectroscopy, and non-invasive information on food, living body, minerals, etc. A substance component analyzer such as a measuring device can be exemplified.
Hereinafter, a food analyzer will be described as an example of the substance component analyzer.

FIG. 17 is a diagram illustrating a schematic configuration of a food analysis apparatus which is an example of an electronic apparatus using an optical module in which the variable wavelength interference filter 5 is incorporated.
As shown in FIG. 17, the food analysis apparatus 200 includes a detector 210 (optical module), a control unit 220, and a display unit 230. The detector 210 includes a light source 211 that emits light, an imaging lens 212 into which light from the measurement target is introduced, a wavelength variable interference filter 5 that splits the light introduced from the imaging lens 212, and the dispersed light. An image pickup unit 213 (detection unit) for detecting the capacitance, and a capacitance detection circuit 10. Note that a filter as shown in FIG. 12 may be used as the variable wavelength interference filter 5.
In addition, the control unit 220 controls the light source control unit 221 that controls the turning on / off of the light source 211 and the brightness control at the time of lighting, the voltage control unit 222 that controls the wavelength variable interference filter 5, and the imaging unit 213. , A detection control unit 223 that acquires a spectral image captured by the imaging unit 213, a signal processing unit 224, and a storage unit 225.

In the food analyzer 200, when the system is driven, the light source 211 is controlled by the light source control unit 221, and light is irradiated from the light source 211 to the measurement object. Then, the light reflected by the measurement object enters the wavelength variable interference filter 5 through the imaging lens 212. The variable wavelength interference filter 5 is applied with a voltage capable of dispersing a desired wavelength under the control of the voltage control unit 222, and the dispersed light is imaged by an imaging unit 213 configured by, for example, a CCD camera or the like. At this time, the signal processing unit 224 measures the gap amount of the inter-reflective film gap G1 based on the detection signal V _S detected by the capacitance detection circuit 10, and the voltage control unit 146 applies it to the electrostatic actuator 56. Correct the voltage to an appropriate value. The captured light is accumulated in the storage unit 225 as a spectral image. In addition, the signal processing unit 224 controls the voltage control unit 222 to change the voltage value applied to the wavelength tunable interference filter 5, and acquires a spectral image for each wavelength.

Then, the signal processing unit 224 performs arithmetic processing on the data of each pixel in each image accumulated in the storage unit 225, and obtains a spectrum at each pixel. In addition, the storage unit 225 stores, for example, information related to food components with respect to the spectrum, and the signal processing unit 224 analyzes the obtained spectrum data based on the information related to food stored in the storage unit 225. The food component contained in the detection target and its content are obtained. Moreover, a food calorie, a freshness, etc. are computable from the obtained food component and content. Furthermore, by analyzing the spectral distribution in the image, it is possible to extract a portion of the food to be inspected that has reduced freshness, and to detect foreign substances contained in the food. Can also be implemented.
Then, the signal processing unit 224 performs processing for causing the display unit 230 to display information such as the components and contents of the food to be examined, the calories, and the freshness obtained as described above.

Moreover, although the example of the food analysis apparatus 200 is shown in FIG. 17, it can utilize also as a noninvasive measurement apparatus of the other information as mentioned above by the substantially similar structure. For example, it can be used as a biological analyzer for analyzing biological components such as measurement and analysis of body fluid components such as blood. As such a bioanalytical device, for example, a device that detects ethyl alcohol as a device that measures a body fluid component such as blood, it can be used as a drunk driving prevention device that detects the drunk state of the driver. Further, it can also be used as an electronic endoscope system provided with such a biological analyzer.
Furthermore, it can also be used as a mineral analyzer for performing component analysis of minerals.

Furthermore, the optical module and electronic apparatus of the present invention can be applied to the following apparatuses.
For example, it is possible to transmit data using light of each wavelength by changing the intensity of light of each wavelength over time. In this case, light of a specific wavelength is transmitted by a wavelength variable interference filter provided in the optical module. The data transmitted by the light of the specific wavelength can be extracted by separating the light and receiving the light at the light receiving unit, and the electronic data having such a data extraction optical module can be used to extract the light data of each wavelength. By processing, optical communication can be performed. At this time, by measuring the gap amount of the gap between the reflection films by the capacitance detection circuit and correcting the gap so that light having a desired wavelength is transmitted, the occurrence of a data communication error or the like can be suppressed.

Further, the electronic apparatus can be applied to a spectroscopic camera, a spectroscopic analyzer, or the like that captures a spectroscopic image by dispersing light with the variable wavelength interference filter of the present invention. An example of such a spectroscopic camera is an infrared camera incorporating a wavelength variable interference filter.
FIG. 18 is a schematic diagram showing a schematic configuration of the spectroscopic camera. As shown in FIG. 18, the spectroscopic camera 300 includes a camera body 310, an imaging lens unit 320, and an imaging unit 330 (detection unit).
The camera body 310 is a part that is gripped and operated by a user.
The imaging lens unit 320 is provided in the camera body 310 and guides incident image light to the imaging unit 330. As shown in FIG. 18, the imaging lens unit 320 includes an objective lens 321, an imaging lens 322, and a wavelength variable interference filter 5 provided between these lenses. The circuit is configured such that the gap amount of the gap G1 between the reflection films can be measured. Note that a filter as shown in FIG. 12 may be used as the variable wavelength interference filter 5.
The imaging unit 330 includes a light receiving element, and images the image light guided by the imaging lens unit 320.
In such a spectroscopic camera 300, a spectral image of light having a desired wavelength can be captured by transmitting light having a wavelength to be imaged by the variable wavelength interference filter 5.

Furthermore, the optical module of the present invention may be used as a bandpass filter. For example, among the light in a predetermined wavelength range emitted from the light emitting element, only the light in a narrow band centered on the predetermined wavelength is used as the variable wavelength interference filter. It can also be used as an optical laser device for spectrally transmitting through.
Further, the optical module of the present invention may be used as a biometric authentication device. For example, the optical module can be applied to authentication devices such as blood vessels, fingerprints, retinas, and irises using light in the near infrared region and visible region.

  Furthermore, an optical module and an electronic device can be used as a concentration detection device. In this case, the infrared energy (infrared light) emitted from the substance is spectrally analyzed by the variable wavelength interference filter, and the analyte concentration in the sample is measured.

  As described above, the optical module and the electronic apparatus of the present invention can be applied to any device that separates predetermined light from incident light. And since the optical module of this invention can disperse | distribute a some wavelength with one device as mentioned above, the measurement of the spectrum of a some wavelength and the detection with respect to a some component can be implemented accurately. Therefore, compared with the conventional apparatus which takes out a desired wavelength with a plurality of devices, it is possible to promote downsizing of the optical module and the electronic apparatus, and for example, it can be suitably used as a portable or in-vehicle optical device.

  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 5 ... Variable wavelength interference filter, 10 ... Capacitance detection circuit, 11 ... Sine wave generation circuit, 11A ... Inverter, 11B ... Crystal oscillator, 12 ... Operational amplifier, 13 ... Feedback circuit, 13A ... Impedance element, 14 ... Sample and hold circuit 15 ... Timing signal generation circuit, 15A ... First one-shot circuit, 15B ... Second one-shot circuit, 20 ... Spectrometer (electronic device), 21 ... Detector, 25 ... Voltage control circuit, 30 ... Control circuit section, DESCRIPTION OF SYMBOLS 31 ... Gap measurement part, 32 ... Filter drive part, 51 ... Fixed board | substrate (1st board | substrate), 52 ... Movable board | substrate (2nd board | substrate), 54 ... Fixed reflective film (1st reflective film), 55 ... Movable reflective film ( (Second reflective film), 56 ... electrostatic actuator (gap changing unit), 100 ... gas detection device (electronic device), 200 ... food analysis device (electronic device) 300 ... spectroscopic camera (electronic apparatus), 565 ... first measurement lead electrode, 566 ... second measurement lead electrode, 567 ... first measurement electrode, 568 ... second measuring electrode, Cx ... detected capacitor.

Claims (12)

A detection target capacitor that is a detection target of the capacitance; and
A sine wave generating circuit that outputs a sine wave signal to an input terminal of the capacitor to be detected;
An operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, wherein the output terminal of the capacitor to be detected is connected to the inverting input terminal, and the non-inverting input terminal is connected to the ground;
A feedback circuit connected between the output terminal and the inverting input terminal of the operational amplifier and provided with an impedance element;
A timing signal generation circuit that generates a timing signal synchronized with the sine wave signal output from the sine wave generation circuit;
A sample-and-hold circuit that is connected to the output terminal of the operational amplifier and acquires an output signal from the operational amplifier at a timing based on the timing signal;
A capacitance detection circuit comprising: The capacitance detection circuit according to claim 1,
The timing signal generation circuit, a first one-shot circuit that outputs a first timing signal synchronized with the sine wave signal,
A second one-shot circuit that outputs a second timing signal synchronized with a timing at which a peak voltage of the output signal is output based on the first timing signal;
With
The capacitance detection circuit, wherein the sample-and-hold circuit acquires an output signal at a timing when the second timing signal is output. The capacitance detection circuit according to claim 2,
The sine wave generation circuit outputs a rectangular input signal obtained by converting a sine wave signal into a rectangular wave to the timing signal generation circuit,
The first one-shot circuit generates the first timing signal that rises in synchronization with the timing when the output signal rises based on the rectangular input signal,
The second one-shot circuit generates a second timing signal that rises in synchronization with a falling timing of the first timing signal,
The output time of the first timing signal and the second timing signal is smaller than a quarter period of the sine wave signal,
The sum of the output time of said 1st timing signal and the output time of said 2nd timing signal is larger than the 1/4 period of the said sine wave signal. The capacity | capacitance detection circuit characterized by the above-mentioned. The capacitance detection circuit according to claim 3,
An output time of the second timing signal is set to a time when the voltage of the output signal is 99% or more of the peak voltage. In the capacity detection circuit according to any one of claims 1 to 4,
The sine wave generation circuit is an oscillation circuit using a crystal resonator. In the capacity detection circuit according to any one of claims 1 to 5,
The impedance detection element is a resistor. In the capacity detection circuit according to any one of claims 1 to 5,
The impedance detection element is an element in which a resistor and a capacitor are directly connected. A first substrate;
A second substrate disposed opposite the first substrate;
A conductive first reflective film provided on the first substrate;
A conductive second reflective film provided on the second substrate and provided facing the first reflective film via a gap between the reflective films;
A gap changing unit for changing a gap amount of the gap between the reflective films;
A capacitance detection circuit that detects the gap amount of the gap between the reflection films,
An optical module, wherein parasitic capacitance generated in the capacitance detection circuit in the detection of the gap amount by the capacitance detection circuit is removed. A first substrate;
A second substrate disposed opposite the first substrate;
A conductive first reflective film provided on the first substrate;
A conductive second reflective film provided on the second substrate and provided facing the first reflective film via a gap between the reflective films;
A gap changing unit for changing a gap amount of the gap between the reflective films;
A sine wave generation circuit that outputs a sine wave signal to the first reflective film;
An operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, wherein the output terminal of the capacitor to be detected is connected to the inverting input terminal, and the non-inverting input terminal is connected to the ground;
A feedback circuit connected between the output terminal and the inverting input terminal of the operational amplifier and provided with an impedance element;
A timing signal generation circuit that generates a timing signal synchronized with the sine wave signal output from the sine wave generation circuit;
A sample-and-hold circuit that is connected to the output terminal of the operational amplifier and acquires an output signal from the operational amplifier at a timing based on the timing signal;
An optical module comprising: A first substrate;
A second substrate disposed opposite the first substrate;
A first reflective film provided on the first substrate;
A second reflective film provided on the second substrate and provided facing the first reflective film via a gap between the reflective films;
A gap changing unit for changing a gap amount of the gap between the reflective films;
A first measurement electrode provided on the first substrate;
A second measurement electrode provided on the second substrate and provided facing the first measurement electrode via a predetermined gap;
A sine wave generation circuit that outputs a sine wave signal to the first measurement electrode;
An operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, wherein the output terminal of the capacitor to be detected is connected to the inverting input terminal, and the non-inverting input terminal is connected to the ground;
A feedback circuit connected between the output terminal and the inverting input terminal of the operational amplifier and provided with an impedance element;
A timing signal generation circuit that generates a timing signal synchronized with the sine wave signal output from the sine wave generation circuit;
A sample-and-hold circuit that is connected to the output terminal of the operational amplifier and acquires an output signal from the operational amplifier at a timing based on the timing signal;
An optical module comprising: A first substrate;
A second substrate disposed opposite the first substrate;
A first reflective film provided on the first substrate;
A second reflective film provided on the second substrate and provided facing the first reflective film via a gap between the reflective films;
A gap changing unit for changing a gap amount of the gap between the reflective films;
A sine wave generation circuit that outputs a sine wave signal to the first reflective film;
An operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, wherein the output terminal of the capacitor to be detected is connected to the inverting input terminal, and the non-inverting input terminal is connected to the ground;
A feedback circuit connected between the output terminal and the inverting input terminal of the operational amplifier and provided with an impedance element;
A timing signal generation circuit that generates a timing signal synchronized with the sine wave signal output from the sine wave generation circuit;
A sample-and-hold circuit that is connected to the output terminal of the operational amplifier and acquires an output signal from the operational amplifier at a timing based on the timing signal;
An electronic apparatus comprising: A first substrate;
A second substrate disposed opposite the first substrate;
A first reflective film provided on the first substrate;
A second reflective film provided on the second substrate and provided facing the first reflective film via a gap between the reflective films;
A gap changing unit for changing a gap amount of the gap between the reflective films;
A first measurement electrode provided on the first substrate;
A second measurement electrode provided on the second substrate and provided facing the first measurement electrode via a predetermined gap;
A sine wave generation circuit that outputs a sine wave signal to the first measurement electrode;
An operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, wherein the output terminal of the capacitor to be detected is connected to the inverting input terminal, and the non-inverting input terminal is connected to the ground;
A feedback circuit connected between the output terminal and the inverting input terminal of the operational amplifier and provided with an impedance element;
A timing signal generation circuit that generates a timing signal synchronized with the sine wave signal output from the sine wave generation circuit;
A sample-and-hold circuit that is connected to the output terminal of the operational amplifier and acquires an output signal from the operational amplifier at a timing based on the timing signal;
An electronic apparatus comprising:

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