JP2010151984A - Deformable mirror system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a deformable mirror system, in which the variation in deformation due to the accumulation of parasitic electric charge is not generated and which is stably driven. <P>SOLUTION: The deformable mirror system includes: a deformable mirror composed of a deformation part 3a with a first electrode 5 formed therein, a fixed part which is disposed facing to the first electrode 5 with a predetermined gap and has a second electrode 6 formed on the side facing to the first electrode 5, and a dielectric film 7 formed between the first electrode 5 and the second electrode 6; an amplifying part 22, which amplifies a driving voltage indication signal so as to deform the deformation part and applies the amplified the driving voltage indication signal to between the first electrode 5 and the second electrode 6 as potential difference of the driving voltage; a parasitic charge estimation part 24, which estimates the parasitic electric charge accumulated on the dielectric film and outputs the estimated value of electric charge; and a correction part 21, which changes the driving voltage indication signal on the basis of the estimated value of electric charge to correct the output voltage of the amplifying part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a deformable mirror system including a deformable mirror that changes the shape of a reflecting surface by electrostatic driving and a drive voltage control unit that drives the deformable mirror.

  2. Description of the Related Art In general, attention is paid to a deformable mirror manufactured using a known MEMS (Micro Electro-Mechanical System) technology and capable of changing the shape of a reflecting surface by electrostatic driving. For example, Patent Document 1 proposes a deformable mirror.

The configuration of a deformable mirror according to the prior art is shown in FIG. In this deformable mirror, the upper substrate 42 and the lower substrate 43 are arranged to face each other with a predetermined interval. The upper substrate 42 includes a reflective surface 44 on the front surface side and an upper electrode 45 on the opposite side, and has flexibility to be deformed by electrostatic attraction. The lower substrate 43 includes a lower electrode 47 formed on the opposite side, and a dielectric film 48 covering the lower electrode 47. The reflecting surface 44 is deformed so as to be bent by an electrostatic driving force generated by applying a voltage between the upper electrode 45 and the lower electrode 43.
JP 2005-168180 A

  In the conventional deformable mirror described above, when a voltage is continuously applied to deform the reflecting surface, a parasitic charge is generated in the dielectric film formed between the upper electrode and the lower electrode due to the electric field generated between the upper electrode and the lower electrode. To do. As this parasitic charge, it is conceivable that it is accumulated in a dielectric film or due to adsorption of polar molecules (mainly water molecules) in the atmosphere. Due to these parasitic charges, an electric field opposite to the electric field for driving is generated, and there is a problem that the electrostatic attractive force is reduced and the deformation of the reflecting surface is reduced.

  Therefore, the present invention has an object to provide a deformable mirror system that stably drives and deforms an input signal by estimating a parasitic charge amount and correcting a drive voltage based on the estimated value. And

  In order to achieve the above object, the embodiment according to the present invention has a deformed portion in which a reflective surface is formed on one surface and a first electrode is formed on the other surface, and a predetermined distance from the first electrode. A fixed portion having a second electrode formed on the opposite side of the first electrode, and a dielectric film formed between the first electrode and the second electrode, And an amplifying unit that amplifies a driving voltage instruction signal to deform the deforming unit, and gives a potential difference of the driving voltage between the first electrode and the second electrode; A parasitic charge amount estimation unit that estimates a parasitic charge amount accumulated in the dielectric film and outputs a charge estimation value; and a drive voltage instruction signal is changed based on the charge estimation value to output an output voltage of the amplification unit And a deformable mirror system comprising:

  According to the present invention, it is possible to provide a deformable mirror system that stably drives and deforms an input signal by estimating a parasitic charge amount and correcting a drive voltage based on the estimated value. it can.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The deformable mirror system according to the first embodiment will be described. FIG. 1 is a top view of the deformable mirror according to the first embodiment viewed from above, FIG. 2 is a cross-sectional view showing the configuration of the deformable mirror taken along the line AA ′ in FIG. 1, and FIG. It is a figure which shows the internal structure of the deformable mirror of the state which removed the board | substrate. First, the configuration of the deformable mirror 1 will be described.

  The deformable mirror 1 is configured such that the electrode substrate 2 and the mirror substrate 3 are arranged so as to face each other with a predetermined interval across the spacer 8. The mirror substrate 3 is formed so that one side is shorter than the electrode substrate 2, and is formed so that a first extraction electrode 5a and a second extraction electrode 6a for connection to a drive control unit described later are exposed.

  In the present embodiment, when viewed from above, the reflective film 4 serving as a circular reflecting surface is provided on the surface side (non-facing surface side) of the mirror substrate 3. Of course, the reflecting surface is not limited to a circular shape, and may be suitably formed in accordance with the application and specifications. As the reflection film 4, a metal having a high reflectance is suitable, although it varies depending on the specifications of the deformable mirror 1, for example, aluminum, gold, or a dielectric multilayer film is used. In the case of using a metal that has the property of being oxidized when exposed to the air, such as aluminum, the outermost surface is further coated with a highly transparent thin film such as silicon oxide.

  As shown in FIG. 3B, the first electrode 5 made of a conductive material such as metal is formed on the entire surface of the mirror substrate 3 on the opposite surface side.

  Further, as shown in FIG. 2, the mirror substrate 3 includes a deformable portion 3 a and a support portion 3 b, and the support portion 3 b supports the deformable portion 3 a and also fixes the electrode substrate 2 via the spacer 8. Used as For these electrodes and the reflective film 4, a plating method, a vapor deposition method using a semiconductor technique, a CVD method, or a sputtering method is used as a manufacturing method. In addition, an electrode and an extraction electrode which will be described later are formed by the same method.

  Further, a substantially identical second electrode 6 is formed on the electrode substrate 2 so as to face the circular reflecting surface, and further a dielectric film (insulating film) so as to cover the second electrode 6. 7 is formed. As the dielectric film 7, a silicon oxide film, a silicon nitride film, or the like is used. In the present embodiment, the dielectric film 7 is formed on the second electrode 6. However, the dielectric film 7 is not limited to this, and may be formed on the opposing first electrode 5 side. You may arrange | position so that it may arrange | position in the state mutually spaced apart from the 2nd electrode 6. In that case, you may form on the other structure provided between electrodes. The second electrode 6 is electrically connected to the second extraction electrode 6a by wiring.

  As shown in FIG. 2, the height of the spacer 8, that is, the distance between the electrode substrate 2 and the mirror substrate 3, is determined by the deformation amount of the deformation portion 3a of the mirror substrate 3, and is about three times or more the necessary deformation amount. An interval of is required. In this embodiment, the spacer 8 is an example formed using an inorganic material such as glass or a silicon substrate, a metal, or the like. Instead, an organic adhesive including beads (adjusted according to the diameter) is used. May be.

  Also, as shown in FIGS. 3A and 3C, the first extraction electrode 5a is connected to the connection pad 5c provided at a position facing the first electrode 5 by wiring on the electrode substrate 2. Is done. A surface of the first electrode 5 facing the connection pad 5c is defined as a connection area 5b. The connection pads 5c and the connection area 5b are connected by pressure contact with a conductive material for electrical connection such as a metal plate or a conductive wire, or a conductive paste. Another method is to form a conductive pattern that turns from the front surface to the back surface of the spacer 8, and to fix the electrical connection by bringing both ends of the conductive pattern into close contact with the connection pad 5c and the connection area 5b when fixing. You may go. Although not shown, electrical connection from the first extraction electrode 5a and the second extraction electrode 6a to the outside is usually performed by wire bonding.

Here, the operation principle of the deformable mirror 1 will be described with reference to FIG.
This deformable mirror 1 employs an electrostatic drive system that deforms the reflecting surface on the deforming portion 3a by electrostatic force. First, the first electrode 5 is connected to a zero (0) potential (ground potential) and a driving voltage is applied to the second electrode 6, so that the first electrode 5 is interposed between the first electrode 5 and the second electrode 6. A potential difference is generated, and the reflecting surface is deformed toward the electrode substrate 2 together with the deforming portion 3a due to the electrostatic force attraction generated thereby.

  The displacement of the deformation portion 3a with respect to the initial state is defined as a deformation amount, and the direction in which the deformation portion 3a deforms toward the drive substrate 2 is defined as a positive deformation amount.

The amount of deformation of the reflecting surface and the deforming portion 3 a can be changed by the potential difference between the first electrode 5 and the second electrode 6.

Next, the parasitic charge described as a problem will be described.
As described above, when a driving voltage is applied to the second electrode 6, the dielectric film formed on the second electrode 6 by the electric field generated between the first electrode 5 and the second electrode 6. Parasitic charges accumulate in 7. As this parasitic charge, it can be considered that it is accumulated in the dielectric film 7 and is due to adsorption of polar molecules (mainly water molecules) in the atmosphere. In the present embodiment, since a positive voltage is applied to the second electrode 6, an electric field in the direction from the second electrode 6 to the first electrode 5 is generated. Due to this electric field, a negative charge is accumulated in the dielectric film 7 on the second electrode 6, and this electric field causes an electric field in the direction opposite to the electric field between the first electrode 5 and the second electrode 6. (An electric field from the first electrode 5 toward the second electrode 6) is generated. As a result, a part of the electric field due to the drive voltage is canceled, the electrostatic attraction is lowered, and the deformation amount of the deformable portion 3a is reduced.

FIG. 4 shows each drive characteristic with and without parasitic charges.
In a state where there is no parasitic charge and a state where there is a parasitic charge, the plot of the drive voltage versus the deformation amount of the deformation unit 3a is shifted to the high voltage direction. In FIG. 4, when the drive voltage is increased by about 20 V, the same deformation amount as when there is no parasitic charge is obtained. Hereinafter, the increment of the drive voltage is referred to as a parasitic charge amount equivalent voltage.

  Next, FIG.5 and FIG.6 shows the structural example of the system by the drive control part 20 and the deformable mirror 1 for driving the deformable mirror 1 of this embodiment. FIG. 5 shows a signal flow during normal driving, and FIG. 6 shows a signal flow during estimation, which will be described later.

  The drive control unit 20 includes a correction unit 21 that corrects the drive voltage instruction signal, an amplification unit 22 that outputs the drive voltage to the deformable mirror 1 based on the amplification unit input signal corrected and output by the correction unit 21, A deformation amount detection unit 23 that detects the deformation amount of the deformation unit 3a, and a parasitic charge amount estimation unit 24 that outputs a parasitic charge amount equivalent voltage estimation value to the correction unit 21 based on the detected deformation amount signal. .

  The correction unit 21 is an amplification unit input signal that is corrected by adding a parasitic charge equivalent voltage estimated value to a drive voltage instruction signal input from an input unit (operation unit) (not shown) or a device that uses the system. Is output. The amplification unit 22 amplifies the amplification unit input signal output from the correction unit 21 and applies a driving voltage to the second electrode 6 to deform the reflection surface of the deformation unit 3a.

  The deformation amount detection unit 23 detects the deformation amount of the reflecting surface of the deformable mirror 1 and outputs a deformation amount signal. The detection principle may be optical detection or electrical. In the case of electrical detection, any of capacitance detection, magnetic force detection, strain gauge, or the like may be used. The deformation amount signal output from the deformation amount detection unit 23 is input to the parasitic charge amount estimation unit 24, and a parasitic charge amount equivalent voltage is estimated based on the deformation amount signal.

Here, a method of estimating the parasitic charge amount equivalent voltage will be described.
In FIG. 4, the relationship between the driving voltage and the deformation amount of the deforming portion 3a in the state where the parasitic charge exists (solid line) is such that the deformation amount becomes minimum when the driving voltage is equal to the parasitic charge amount equivalent voltage, and the driving voltage below that Is monotonously decreasing, and at higher driving voltages, it is monotonically increasing. In FIG. 4, when the drive voltage is 20V, the deformation amount is minimum. The minimum amount of deformation is ideally the opening, but a certain amount of deformation may remain due to assembly of the members. The parasitic charge amount estimation unit 24 obtains a drive voltage when the deformation amount signal output from the deformation amount detection unit 23 is minimized using the above characteristics, and calculates a parasitic charge amount equivalent voltage estimation value (parameter). ).

Next, the deformation minimum derivation method will be described.
The estimation of the parasitic charge equivalent voltage is performed as follows. When the driving voltage is already applied, the driving is stopped, and the input of the amplifying unit 22 is switched from the output of the correcting unit 21 to the parasitic charge amount estimating unit 24 as shown in FIG. For this switching, a switching unit (switching switch) (not shown) may be provided to perform signal switching.

  The parasitic charge amount estimation unit 24 controls the input signal to the amplifying unit 22 to gradually increase the signal drive voltage from 0 V, detect the drive voltage at which the deformation amount signal changes from decrease to increase, and detect the parasitic charge amount equivalent voltage. Hold and output as a guess.

  As another method, the drive voltage is sequentially increased from 0 V to a voltage sufficiently higher than the voltage corresponding to the amount of parasitic charges, applied, the deformation amount at the applied voltage is measured at any time, and the obtained deformation amount and the drive voltage value are compared. , Fitting function. At this time, the drive voltage is applied within a range in which the deformable portion 3a of the deformable mirror 1 is not destroyed. It is also possible to adopt a method of outputting a parasitic charge amount equivalent voltage estimated value by obtaining a drive voltage that minimizes the deformation amount in the fitted function.

The function [equation (1)] used for fitting is

(Δd: deformation amount, V: drive voltage, d0, α, Voff: parameter to be fitted) can be used, and at that time, the deformation amount is minimized when the drive voltage is Voff. As a result, Voff is output. Thus, after obtaining the estimated voltage value corresponding to the parasitic charge amount, as shown in FIG. 5, the input of the amplifying unit 22 is returned to the output of the correcting unit 21, and normal driving is performed.

  As described above, the correction of the drive voltage by the correction unit 21 based on the obtained parasitic charge amount equivalent voltage estimation value does not cause a change in the deformation amount due to the accumulation of the parasitic charge amount. The deformable mirror 1 can be driven stably. The estimation of the parasitic charge equivalent voltage may be performed automatically when the power is turned on, or may be performed at predetermined time intervals during the operation of the system.

Next, a modified example of the first embodiment will be described with reference to FIGS. 7 (a) and 7 (b) to FIGS. 10 (a) and 10 (b).
In this modification, a parasitic charge amount equivalent voltage is estimated by utilizing the fact that the deformation amount is folded back by a parasitic charge amount equivalent voltage and is generated in an absolute value near the voltage at which the deformation amount of the deformation portion 3a is minimized. Is. The configuration of this modification is the same as that of the first embodiment described above, and a description thereof is omitted here.

  In this modification, a sine wave having an offset voltage is applied from the amplifying unit 22 to the second electrode 6 as a drive voltage. FIG. 7A shows an example in which the offset voltage is high and sufficiently different from the parasitic charge amount equivalent voltage, and FIG. 7B shows the behavior of the deformation amount of the deformation portion 3a at that time. FIG. 8A shows an example in which the offset voltage is high but the difference is small with respect to the parasitic charge amount equivalent voltage, and FIG. 8B shows the behavior of the deformation amount of the deformation portion 3a at that time. FIG. 9A shows an example where the offset voltage matches the parasitic charge amount equivalent voltage, and FIG. 9B shows the behavior of the deformation amount of the deformation portion 3a at that time. FIG. 10A shows an example in which the offset voltage is low and sufficiently different from the parasitic charge amount equivalent voltage, and FIG. 10B shows the behavior of the deformation amount of the deformation portion 3a at that time.

  As shown in FIG. 7A, when the offset voltage is high with respect to the parasitic charge amount equivalent voltage, a uniform oscillation caused by the sine wave occurs in the deformed portion 3a. When the parasitic charge equivalent voltage and the offset voltage approach each other, the behavior of the deformation amount is a state in which a sine wave is detected, and the amplitude of the deformation amount decreases.

  Furthermore, as shown in FIG. 9A, when the parasitic charge amount equivalent voltage and the offset voltage match, as shown in FIG. 9B, the behavior of the deformation amount is the center of the amplitude of the original sine wave. The waveform is folded at, and the amplitude is minimum. Further, as shown in FIG. 10A, when the offset voltage is lower than the parasitic charge amount equivalent voltage, as shown in FIG. 10B, the deformation amount is shown in FIG. 7B described above. The phase is opposite to the phase, and the amplitude is increased as compared with the case of FIG.

  By utilizing the above characteristics, a parasitic charge equivalent voltage estimated value can be obtained from the offset voltage that minimizes the amplitude of the deformation. Here, when detecting the deformation amount of the deformation portion 3a, by focusing only on the same frequency component as the frequency of the sine wave applied to the second electrode 6, and detecting the deformation amount of the deformation portion 3a, Accurate charge estimation can be performed. Although the waveform of the voltage to be applied has been described as a sine wave, other alternating signals such as a rectangular wave and a triangular wave may be used. Further, since the phase difference between the sine wave of the drive voltage and the sine wave, which is the behavior of the deformation amount, is changed across the state where the parasitic charge equivalent voltage and the offset voltage coincide with each other, a method for detecting this can be used.

Next, a second embodiment will be described.
FIG. 11 shows a configuration example of a system including the drive control unit 20 and the deformable mirror 1 for driving the deformable mirror 1 of the present embodiment. The deformable mirror 1 is equivalent to the first embodiment (FIGS. 1 to 3) described above, and will be described using the same reference numerals, and description of the configuration here will be omitted.

The present embodiment is a deformable mirror system including a drive control unit 20 including a correction unit 21, an amplification unit 22, and a parasitic charge amount estimation unit 25, and a deformable mirror 1.
The correction unit 21 adds the estimated voltage value corresponding to the parasitic charge amount to the drive voltage instruction signal input to the system, and outputs an amplification unit input signal. The amplifying unit 22 amplifies the amplifying unit input signal output from the correcting unit 21 and applies a driving voltage to the second electrode 6. The parasitic charge amount estimation unit 25 monitors the drive voltage output from the amplification unit 22, estimates a parasitic charge amount equivalent voltage from the information, and outputs a parasitic charge amount equivalent voltage estimation value. The estimation method will be described later.

With reference to FIG. 12, the change with time of the voltage corresponding to the amount of parasitic charge to be charged will be described.
The above-described voltage corresponding to the amount of parasitic charge changes with time according to the state of the drive voltage, and converges to the same voltage value as the drive voltage after a long time. As shown in FIG. 12, when the drive voltage is higher than the parasitic charge amount equivalent voltage, the parasitic charge amount equivalent voltage becomes high. On the other hand, when the drive voltage is lower than the parasitic charge amount equivalent voltage, the parasitic charge amount equivalent voltage is low.

When the parasitic charge equivalent voltage is 0V and the drive voltage changes from 0V to Vin in a stepped manner, the parasitic charge equivalent voltage Vout changes as calculated by the following equation (2).

Here, Vin: drive voltage, t: time from the start of application, τ: time constant of convergence. Further, FIG. 12 conceptually shows a state in which the voltage equivalent to the amount of parasitic charges has sufficiently converged. However, in the actual deformable mirror 1, the convergence takes a long time (several thousand hours or more) as shown in FIG. 13, and when the drive voltage is changed before the convergence, the amount of parasitic charge at that time is changed. Convergence starts from the equivalent voltage toward the drive voltage.

  The deformable mirror system in the present embodiment is estimated using the above-described characteristics of parasitic charge accumulation. For example, using Equation (2), a parasitic charge equivalent voltage estimated value is obtained and output based on the drive voltage and the time from the start of application.

  As described above, the deformable mirror system according to the present embodiment estimates the parasitic charge amount without temporarily stopping the drive, and corrects the drive voltage to generate the deformation amount change caused by the parasitic charge. Therefore, the deformable mirror 1 can be driven stably. The parasitic charge amount estimation unit 25 may obtain the amplification voltage from the amplification unit input signal output from the correction unit 21 without directly monitoring the drive voltage.

Next, derivation of the time constant in the deformable mirror system of this embodiment will be described.
The time constant τ of the above-described equation (2) used in the parasitic charge amount estimation unit 25 can be derived by the following procedure. First, in a state where the voltage Vin is applied as the drive voltage, a voltage estimated value corresponding to the amount of parasitic charge at a certain point in time is detected and set as V′out. This detection uses the method of the first embodiment. Thereafter, when the time Δt elapses, the estimated voltage value corresponding to the parasitic charge amount is detected again and set to Vout. The time constant τ can be derived by performing the calculation of Equation (3) described later using the above values. This process may be performed at the time of factory shipment or may be performed as an initialization operation when the power is turned on. Note that it is desirable to store the value of the time constant τ obtained at the time of factory shipment in a nonvolatile memory.

Next, a first modification of the second embodiment will be described with reference to FIG.
This modification has the same configuration as that of the second embodiment (FIG. 11) described above, and the method of estimating the parasitic charge amount is different.

  The parasitic charge amount estimation unit 25 in the second embodiment described above can also have the following configuration. In the present modification, the parasitic charge amount estimation unit 25 obtains a new parasitic charge amount equivalent voltage estimated value based on the difference between the drive voltage and the immediately preceding parasitic charge amount equivalent voltage estimated value. For this derivation, the following formula (4) is used. The derivation procedure is as follows.

First, a parasitic charge equivalent voltage estimated value is stored as V′out. In the initial state, V′out = 0 may be set, or may be derived using the method in the first embodiment. After elapse of time Δt, a new parasitic charge equivalent voltage estimated value Vout is derived from the equation (4) based on the drive voltage and the time constant τ. As the time constant τ used here, a value derived from the above-described equation (3) is used. By using this procedure, the amount of parasitic charge can be estimated sequentially, and therefore, as shown in FIG. 13, even if the drive voltage changes before the parasitic charge amount equivalent voltage converges, An amount equivalent voltage estimated value can be output.

Here, Vout: current estimated parasitic charge amount equivalent voltage value (output), V′out: immediately preceding estimated parasitic charge amount equivalent voltage value, Vin: drive voltage, τ: time constant, Δt: calculation interval time.

Next, a second modification of the second embodiment will be described with reference to FIG.
This modification has the same configuration as that of the above-described second embodiment (FIG. 11), and the method for estimating the parasitic charge is different.

  In this modification, it can be considered that the state where the drive voltage is 0 V is maintained even when the power source (main power source) of the deformable mirror system is not turned on. Therefore, the amount of parasitic charges is estimated based on the elapsed time from when the power supply is turned off. The estimation procedure is as follows.

  First, the timing at which the power source of the deformable mirror system is turned off is detected, and the parasitic charge amount equivalent voltage estimation value V3 and the time t1 at that time are stored in the nonvolatile memory. The power-off detection may be performed by detecting a decrease in the power supply voltage or by receiving a shutdown signal from a device using the deformable mirror system.

Next, when the time when the deformable mirror system is turned on is t2, the amount of parasitic charges can be estimated from the following equation (5).

  Detection of the timing when the power supply of this system is turned on may be detected by detecting an increase in power supply voltage or by receiving a startup signal from an apparatus using the deformable mirror system. According to this modification, even in a system in which the power supply is turned off for a long time, the amount of parasitic charges can be reliably estimated, and stable driving can be realized. In addition, although the time of power-off was memorize | stored as time t1, you may memorize | store the time when the drive voltage became the opening. In this case, the parasitic charge amount voltage estimated value V3 stores the parasitic charge amount at the time when the drive voltage becomes the gate.

Next, a third embodiment will be described.
FIG. 16 shows a configuration example of a system including the drive control unit 20 and the deformable mirror 1 for driving the deformable mirror 1 of the present embodiment. The deformable mirror 1 is equivalent to the first embodiment (FIGS. 1 to 3) described above, and will be described using the same reference numerals, and description of the configuration here will be omitted.

  In the present embodiment, the parasitic charge equivalent voltage is estimated using the characteristic that the parasitic charge changes depending on the environment in which the deformable mirror 1 is used. The present embodiment includes a correction unit 21, an amplification unit 22, a temperature sensor / humidity sensor 26, and a parasitic charge amount estimation unit 27, and drives and controls the deformable mirror 1 using a sensor signal based on the temperature / humidity of the atmosphere. This is a deformable mirror system. In this configuration, the temperature sensor / humidity sensor 26 is a known sensor, and even if the temperature sensor and the humidity sensor are both mounted, either the temperature sensor or the humidity sensor is mounted. It may be.

  In this configuration, the temperature sensor / humidity sensor 26 detects the temperature / humidity of the atmosphere of the deformable mirror 1 and outputs a temperature / humidity signal to the parasitic charge amount estimation unit 27. The parasitic charge amount estimation unit 27 estimates a parasitic charge amount equivalent voltage based on the temperature / humidity signal and outputs a parasitic charge amount equivalent voltage estimation value to the correction unit 21.

  The correction unit 21 adds the estimated voltage value corresponding to the parasitic charge amount to the drive voltage instruction signal input to the system, and outputs an amplification unit input signal. The amplifying unit 22 amplifies the amplifying unit input signal output from the correcting unit 21 and applies a driving voltage to the second electrode 6 to drive the deformable mirror 1.

  According to the present embodiment, it is possible to obtain a parasitic charge amount equivalent voltage estimation value corresponding to the parasitic charge amount due to adsorption of polar molecules (mainly water molecules) in the atmosphere.

In addition to this embodiment, any one of the first and second embodiments described above is combined to reduce the amount of parasitic charge caused by the charge accumulated in the dielectric film, and to absorb polar molecules in the atmosphere. It is also possible to obtain a parasitic charge equivalent voltage estimated value in consideration of the resulting parasitic charge and correct the drive voltage output from the amplifying unit 22.
Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention.

(Appendix)
The invention having the following configuration can be extracted from the specific embodiment.

(1) Deformation part [3a] in which a reflective surface was formed;
A fixing part [8] for fixing the deformation part;
Electrodes [5, 6] provided to face the deformed portion and the fixed portion, respectively;
A dielectric film [7] present between the two electrodes;
In a deformable mirror [1] comprising:
An amplifying unit [22] that amplifies a driving voltage instruction signal to deform the deforming unit and gives a potential difference between the driving voltages to the two electrodes;
A parasitic charge amount estimation unit [24] that estimates a parasitic charge amount accumulated in the dielectric film and outputs an estimated charge value; and an output voltage of the amplifying unit by changing a drive voltage instruction signal based on the estimated charge value A deformable mirror system, comprising: a correction unit [21] that corrects the angle.

(Corresponding embodiment)
The embodiment related to the deformable mirror system described in (1) corresponds to the first embodiment. [] In each item of (1) are reference numerals corresponding to the components shown in FIGS. 1 to 3.

(Function and effect)
According to the deformable mirror system described in (1), the relationship between the deformation amount of the deformation portion obtained by actual measurement and the drive voltage is such that the deformation amount is minimum when the drive voltage is equal to the parasitic charge amount equivalent voltage. Thus, it decreases monotonously at a driving voltage lower than that, and increases monotonously at a driving voltage higher than that. Therefore, the driving voltage when the deformation amount signal is minimized is obtained and output as a parasitic charge amount equivalent voltage estimation value (parameter). The minimum amount of deformation is ideally zero. The correction voltage is corrected by the correction unit based on the estimated parasitic charge equivalent voltage estimated value, so that the deformation amount due to the accumulation of the parasitic charge does not occur and the deformable mirror is driven stably. be able to.

(2) The parasitic charge amount estimation unit [24] outputs a parasitic charge amount equivalent voltage estimated value that is an estimated value of a voltage necessary to cancel the electrostatic force due to the parasitic charge as a charge estimated value,
The correction unit [21] changes the drive voltage instruction signal so that a value obtained by adding the parasitic charge amount equivalent voltage estimation value is output from the amplification unit [22] (1) The deformable mirror system described in 1.

(Corresponding embodiment)
The embodiment relating to the deformable mirror system described in (2) corresponds to the first embodiment. [] In each item of (2) are reference numerals corresponding to the components shown in FIGS. 1 to 3.

(Function and effect)
According to the deformable mirror system described in (2), the parasitic charge amount estimation unit gradually increases the signal drive voltage from 0 V by controlling the input signal to the amplification unit, and the deformation amount signal increases from the decrease. Is detected and output as a parasitic charge equivalent voltage estimated value. The correction voltage is corrected by the correction unit based on the estimated parasitic charge equivalent voltage estimated value, so that the deformation amount due to the accumulation of the parasitic charge does not occur and the deformable mirror is driven stably. be able to.

(3) The parasitic charge amount estimation unit [25] detects the driving voltage and outputs a parasitic charge amount equivalent voltage estimated value based on the state of the driving voltage (1) or (2 ) Deformable mirror system.

(Corresponding embodiment)
The second embodiment corresponds to the embodiment of the deformable mirror system described in (3). [] In (3) are reference numerals corresponding to the components shown in FIG.

(Function and effect)
According to the deformable mirror system described in (3), the parasitic charge amount estimation unit monitors the drive voltage output from the amplification unit, and estimates the parasitic charge amount equivalent voltage from the information to estimate the parasitic charge amount equivalent voltage. The estimated value is output to the correction unit. The drive voltage is corrected by the correction unit based on the obtained parasitic charge amount equivalent voltage estimated value. As in (2), the effect is that the amount of parasitic charge is estimated without temporarily stopping the drive, and the deformable mirror 1 is driven stably without causing a deformation amount change due to the parasitic charge. be able to.

  (4) The parasitic charge amount estimation unit [25] detects the drive voltage and a period during which the voltage is applied, and outputs a parasitic charge equivalent voltage estimated value based on the voltage and the length of the period. (3) The deformable mirror system according to (3).

(Corresponding embodiment)
The embodiment relating to the deformable mirror system described in (4) corresponds to the second embodiment. [] In [4] are reference numerals corresponding to the components shown in FIG.

(Function and effect)
The deformable mirror system in the present embodiment makes an estimation using the characteristics of parasitic charge accumulation. For example, using formula (1), a parasitic charge amount equivalent voltage estimation value is obtained and output based on the drive voltage and the time (period) from the start of application. As in (2), the effect is that the amount of parasitic charge is estimated without temporarily stopping driving, and the deformable mirror is driven stably without causing a change in the amount of deformation caused by the parasitic charge. Can do.

  (5) The parasitic charge estimation unit [25] detects a period in which the amplification unit [22] does not apply a voltage to the opposed electrodes and detects the parasitic charge based on the length of the period. 4. The deformable mirror system according to claim 3, wherein an equivalent voltage estimated value is output.

  The second modification of the second embodiment shown in FIG. 15 corresponds to the embodiment relating to the deformable mirror system described in (5). [] In (5) are reference numerals corresponding to the components shown in FIG.

(Function and effect)
The deformable mirror system in the present embodiment can reliably estimate the amount of parasitic charges even in a system in which the power supply is turned off for a long time, and can realize stable driving.

  (6) The parasitic charge amount estimation unit [25] calculates a change amount of the parasitic charge amount equivalent voltage from the difference between the drive voltage and the immediately preceding parasitic charge amount equivalent voltage estimate value, and obtains the parasitic charge amount equivalent voltage estimate value. The deformable mirror system according to (3), wherein the deformable mirror system outputs.

  The embodiment relating to the deformable mirror system described in (6) corresponds to the first modification of the second embodiment shown in FIG. [] In (6) are reference numerals corresponding to the components shown in FIG.

(Function and effect)
The deformable mirror system according to the present embodiment can estimate the parasitic charge amount sequentially, and continuously estimate the parasitic charge equivalent voltage even when the drive voltage changes before the parasitic charge equivalent voltage converges. A value can be output.

  (7) The parasitic charge amount estimation unit [24] includes a detection unit [23] that detects the deformation amount of the deformable mirror [1], and the deformation signal output from the drive voltage and the detection unit [23]. The variable shape mirror system according to (1) or (2), wherein an estimated voltage value corresponding to the amount of parasitic charges is output based on the relationship (1).

  The embodiment related to the deformable mirror system described in (7) corresponds to the first embodiment. [] In (7) are reference numerals corresponding to the components shown in FIG.

(Function and effect)
The deformation amount detection unit of the deformable mirror system in this embodiment detects the deformation amount of the reflecting surface of the deformable mirror by optical detection or electrical detection, and outputs a deformation amount signal. The parasitic charge amount estimation unit estimates a parasitic charge amount equivalent voltage based on the deformation amount signal and the drive voltage.

  (8) The parasitic charge amount estimation unit [24] detects the drive voltage that minimizes the value of the deformation signal, and outputs a parasitic charge amount equivalent voltage estimated value based on the detected voltage. The deformable mirror system according to (7).

  The embodiment related to the deformable mirror system described in (8) corresponds to the first embodiment. [] In (8) are reference numerals corresponding to the components shown in FIG.

(Function and effect)
When the deformation amount detected by the deformation amount detection unit of the deformable mirror system in the present embodiment is minimized, the drive voltage and the parasitic charge amount equivalent voltage estimation value are equal. Based on the drive voltage at this time, the parasitic charge Outputs an estimated voltage (parameter) corresponding to the amount.

  (9) The parasitic charge amount estimation unit [24] applies an AC signal having an offset voltage to the electrodes 5 and 6 provided facing each other through the amplification unit [22], and The variable shape mirror system according to (7), characterized in that an offset voltage having a minimum amplitude is obtained, and a parasitic charge equivalent voltage estimated value is output based on the offset voltage.

  The embodiment relating to the deformable mirror system described in (9) corresponds to a modification of the first embodiment in FIGS. [9] In [9], the reference numerals corresponding to the components shown in FIG.

(Function and effect)
The deformable mirror system according to the present embodiment estimates the parasitic charge equivalent voltage from the offset voltage that minimizes the amplitude of the deformation by utilizing the fact that the deformation is folded back by the parasitic charge equivalent voltage and is generated as an absolute value. The value can be determined.

  (10) The parasitic charge amount estimation unit [24] applies an AC signal having an offset voltage to the electrodes 5 and 6 provided opposite to each other via the amplification unit [22], and 8. The deformable mirror system according to claim 7, wherein an offset voltage at which the phase difference of the AC signal changes is obtained, and a parasitic charge equivalent voltage estimated value is output based on the offset voltage.

  The modification of the first embodiment of the embodiment related to the deformable mirror system described in (10) is applied. [9] In [9], the reference numerals corresponding to the components shown in FIG.

(Function and effect)
In the deformable mirror system according to the present embodiment, the phase difference between the behavior of the drive voltage and the deformation amount changes across the state where the parasitic charge equivalent voltage and the offset voltage coincide with each other. The value can be determined.

  (11) The parasitic charge amount estimation unit [27] includes a temperature detection unit [26], and outputs a parasitic charge amount equivalent voltage estimation value based on the temperature. Deformable mirror system.

  The embodiment relating to the deformable mirror system described in (11) corresponds to the third embodiment. [] In (11) are reference numerals corresponding to the components shown in FIG.

(Function and effect)
In the deformable mirror system according to the present embodiment, a parasitic charge equivalent voltage estimated value is obtained based on the temperature of the deformable mirror atmosphere.
(12) The parasitic charge amount estimation unit [27] includes a humidity detection unit [26], and outputs a parasitic charge amount equivalent voltage estimation value based on humidity. Variable shape mirror system.

  The embodiment relating to the deformable mirror system described in (12) corresponds to the third embodiment. [] In (12) are reference numerals corresponding to the components shown in FIG.

(Function and effect)
In the deformable mirror system according to the present embodiment, a parasitic charge amount equivalent voltage estimation value is obtained based on the humidity of the deformable mirror atmosphere.
(13) The variable shape mirror according to claim 9, wherein the parasitic charge amount estimation unit obtains an offset voltage that minimizes the amplitude of the same frequency component as the AC signal applied to the electrode among the deformation signals. system.

  The embodiment relating to the deformable mirror system described in (13) corresponds to the modification of the first embodiment in FIGS. 7 (a), 7 (b) to 10 (a), 10 (b). [] In (13) are reference numerals corresponding to the components shown in FIG.

(Function and effect)
In the deformable mirror system according to the present embodiment, when detecting the swing of the deformed portion, the swing of the deformed portion is focused on only the frequency component identical to the frequency of the sine wave applied to the second electrode. By detecting this, it is possible to perform charge estimation with higher accuracy.

FIG. 1 is a top view of the deformable mirror according to the first embodiment as viewed from above. FIG. 2 is a cross-sectional view showing the configuration of the A-A ′ cross section of the deformable mirror shown in FIG. 1. FIGS. 3A, 3B, and 3C are views showing the internal configuration of the deformable mirror with the upper substrate removed. FIG. 4 is a diagram illustrating drive characteristics depending on the presence or absence of parasitic charges in the deformable mirror according to the first embodiment. FIG. 5 is a configuration example of a system including a drive control unit and a deformable mirror for driving the deformable mirror, and is a diagram illustrating a signal flow during normal driving. FIG. 6 is a diagram illustrating a signal flow at the time of estimation. FIG. 7A is a diagram showing an example in which the offset voltage is high and sufficiently different from the parasitic charge amount equivalent voltage, and FIG. 7B is a diagram showing the behavior of the deformation amount of the deformation portion at that time. . FIG. 8A is a diagram illustrating an example in which the offset voltage is high and the difference is small with respect to the parasitic charge amount equivalent voltage, and FIG. 8B is a diagram illustrating the behavior of the deformation amount of the deformation portion at that time. FIG. 9A is a diagram illustrating an example in which the offset voltage matches the parasitic charge amount equivalent voltage, and FIG. 9B is a diagram illustrating the behavior of the deformation amount of the deformation portion at that time. FIG. 10A is a diagram showing an example in which the offset voltage is low and sufficiently different from the parasitic charge amount equivalent voltage, and FIG. 10B is a diagram showing the behavior of the deformation amount of the deformation portion at that time. . FIG. 11 is a diagram illustrating a configuration example of a system including a drive control unit and a deformable mirror for driving the deformable mirror according to the second embodiment. FIG. 12 is a diagram conceptually showing a state in which the parasitic charge amount equivalent voltage is sufficiently converged. FIG. 13 is a diagram conceptually showing a state in which the voltage equivalent to the amount of parasitic charges converges with time. FIG. 14 is a diagram for explaining a first modification of the second embodiment. FIG. 15 is a diagram for explaining a second modification of the second embodiment. FIG. 16 is a diagram illustrating a configuration example of a system including a drive control unit and a deformable mirror for driving the deformable mirror according to the third embodiment. FIG. 17 is a diagram showing a configuration of a deformable mirror according to the prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Variable shape mirror, 2 ... Electrode substrate, 3 ... Mirror substrate, 3a ... Deformation part, 3b ... Support part, 4 ... Reflection film, 5 ... 1st electrode, 5a ... 1st extraction electrode, 5b ... Connection area 5c: Connection pad, 6 ... Second electrode, 6a ... Second extraction electrode, 7 ... Dielectric film (insulating film) 8 ... Spacer, 20 ... Drive control unit, 21 ... Correction unit, 22 ... Amplification unit , 23 ... deformation amount detection unit, 24 ... parasitic charge amount estimation unit, 25 ... parasitic charge amount estimation unit, 26 ... temperature sensor / humidity sensor, 27 ... parasitic charge amount estimation unit.

Claims (13)

A deformed portion having a reflective surface formed on one surface and a first electrode formed on the other surface is disposed opposite to the first electrode with a predetermined interval, A deformable mirror composed of a fixed portion having a second electrode formed on the opposite side, and a dielectric film formed between the first electrode and the second electrode;
An amplifying unit that amplifies a driving voltage instruction signal to deform the deforming unit and applies the signal as a potential difference of the driving voltage between the first electrode and the second electrode;
A parasitic charge amount estimation unit that estimates a parasitic charge amount accumulated in the dielectric film and outputs an estimated charge value;
A correction unit that corrects the output voltage of the amplification unit by changing the drive voltage instruction signal based on the estimated charge value;
A deformable mirror system comprising: The parasitic charge amount estimation unit outputs, as a charge estimation value, a parasitic charge amount equivalent voltage estimation value that is an estimation value of a voltage necessary to cancel the electrostatic force due to the parasitic charge,
2. The deformable mirror according to claim 1, wherein the correction unit changes the drive voltage instruction signal so that a value obtained by adding the parasitic charge equivalent voltage estimated value is output from the amplification unit. system.   3. The variable shape according to claim 1, wherein the parasitic charge amount estimation unit detects the drive voltage and outputs a parasitic charge amount equivalent voltage estimation value based on a state of the drive voltage. Mirror system.   The parasitic charge amount estimation unit detects the drive voltage and a period during which the voltage is applied, and outputs a parasitic charge equivalent voltage estimated value based on the voltage and the length of the period. 4. The deformable mirror system according to 3.   The parasitic charge amount estimation unit detects a period in which the amplification unit does not apply a voltage to the opposed electrodes, and outputs a parasitic charge amount equivalent voltage estimation value based on the length of the period. 4. The deformable mirror system according to claim 3, wherein   The parasitic charge amount estimation unit calculates a change in the parasitic charge amount equivalent voltage from the difference between the drive voltage and the immediately preceding parasitic charge amount equivalent voltage estimate value, and outputs a parasitic charge amount equivalent voltage estimate value. The deformable mirror system according to claim 3.   The parasitic charge amount estimation unit includes a detection unit that detects a deformation amount of the deformable mirror, and outputs a parasitic charge amount equivalent voltage estimation value based on a relationship between the drive voltage and a deformation signal output from the detection unit. The deformable mirror system according to claim 1 or 2, characterized in that:   8. The parasitic charge amount estimation unit detects the drive voltage that minimizes the value of the deformation signal and outputs a parasitic charge amount equivalent voltage estimation value based on the detected voltage. Deformable mirror system.   The parasitic charge amount estimation unit applies an AC signal having an offset voltage to the electrodes provided opposite to each other through the amplifying unit, obtains an offset voltage that minimizes the amplitude of the deformation signal, and calculates the offset 8. The deformable mirror system according to claim 7, wherein an estimated voltage value corresponding to the amount of parasitic charges is output based on the voltage.   The parasitic charge amount estimation unit applies an AC signal having an offset voltage to the electrodes provided opposite to each other through the amplification unit, and generates an offset voltage at which a phase difference between the deformation signal and the AC signal changes. The deformable mirror system according to claim 7, wherein the variable shape mirror system is obtained and outputs a parasitic charge equivalent voltage estimated value based on the offset voltage.   The variable shape mirror system according to claim 2, wherein the parasitic charge amount estimation unit includes a temperature detection unit, and outputs a parasitic charge amount equivalent voltage estimation value based on the temperature.   The variable shape mirror system according to claim 2, wherein the parasitic charge amount estimation unit includes a humidity detection unit, and outputs a parasitic charge amount equivalent voltage estimation value based on the humidity.   10. The deformable mirror system according to claim 9, wherein the parasitic charge amount estimation unit obtains an offset voltage that minimizes the amplitude of the same frequency component as the AC signal applied to the electrode among the deformation signals.

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