JP4711201B2 - Optical deflector control device and optical deflector control method - Google Patents

Description

  The present invention relates to an optical deflector control device and an optical deflector control method, and more particularly to an optical deflector control device and an optical deflector control method for controlling light deflection caused by application of an electric field to an electro-optic crystal.

  Currently, there is an increasing demand for light control elements for deflecting laser light in projectors and other video equipment, laser printers, high-resolution confocal microscopes, barcode readers, spectrometers, and the like. As a technology for deflecting light, a technology that rotates a polygon mirror, a technology that controls the deflection direction of light using a galvanometer mirror, a light diffraction technology that uses an acousto-optic effect, a micromachine technology called MEMS (Micro Electro Mechanical System), a prism Techniques for deflecting a beam using an electro-optic crystal processed into a shape or an electro-optic crystal on which prism-shaped electrodes are formed have been proposed.

  Among them, the light deflection technique disclosed in Patent Document 1 is a very useful configuration because the beam deflection can be efficiently increased with a simple configuration. That is, in the light deflection technique described in Patent Document 1, by applying an electric field to the electro-optic crystal, a space charge is generated inside the electro-optic crystal, and the cross section is perpendicular to the optical axis of the incident light. A gradient of the magnitude of the electric field is generated. Since the gradient of the refractive index changes due to the gradient of the electric field, the light propagating through the electro-optic crystal is deflected.

  In Patent Document 1, a large deflection angle can be obtained by using a simple and symmetric structure of an electro-optic crystal and a positive electrode and a negative electrode respectively disposed on two opposing surfaces of the electro-optic crystal. Further, the deflection angle of the deflected beam can be temporally changed by applying an AC voltage between the electrodes instead of the DC voltage.

International Publication No. 2006/137408 Pamphlet

  As apparent from the above, in the optical deflection technique, the configuration in which electrons are injected into the electro-optic crystal as described in Patent Document 1 to cause the gradient of the electric field is the same as that of the outgoing light that was required at that time. Increasing the deflection angle can be realized and is very effective. As a next demand that satisfies such a demand for obtaining a large deflection angle, there is a voice that it is desired to shorten a time required to obtain a certain deflection angle according to voltage application.

  That is, conventionally, a predetermined time is required until the deflection angle becomes constant due to the influence of trap levels existing in the electro-optic crystal or at the interface between the electro-optic crystal and the electrode. It takes some time to fill the empty trap levels in the electro-optic crystal or at the interface between the electro-optic crystal and the positive electrode or negative electrode with electrons. Therefore, when a voltage is applied to the positive electrode and the negative electrode to inject electrons into the electro-optic crystal for deflection, electrons are injected from the negative electrode, but it takes time to fill the empty trap level with electrons. In short, it takes time until the spatial distribution of electrons (space charge) reaches a steady state. Therefore, during that time, the deflection angle is not uniquely determined by the value of the applied voltage. That is, since the deflection angle is not stable until the space charge spatial distribution reaches a steady state and a predetermined time is required until the steady state is reached, it takes time until the deflection angle is uniquely determined by the value of the applied voltage.

  The present invention has been made in view of such problems, and the object of the present invention is to use electro-optics when deflecting light by using the gradient of the electric field generated by electron injection into the electro-optic crystal. It is an object of the present invention to provide an optical deflector control device and an optical deflector control method capable of shortening a deflection angle uniquely determined by a value of a voltage applied to a crystal or a deflection angle within an allowable range.

In order to solve such a problem, the invention according to claim 1 is an electro-optic crystal having an electro-optic effect, wherein a space charge is generated inside by applying a voltage, and the gradient of the electric field is increased. An electro-optic crystal generating, a first electrode disposed on the first surface of the electro-optic crystal, and a second surface disposed on the second surface opposite to the first surface of the electro-optic crystal. An optical deflector control device for controlling an operation of an optical deflector including an electrode , wherein a first voltage for the operation of the optical deflector is applied between the first electrode and the second electrode. A first voltage application operation to be applied, and a second voltage applied between the first electrode and the second electrode so that a deflection angle is constant with respect to a time axis when the first voltage is applied. characterized in that it comprises a voltage applying means for controlling the second voltage application operation for

  The invention according to claim 2 is the invention according to claim 1, further comprising a timing acquisition means for acquiring a timing for applying the first voltage, wherein the second voltage application means is the timing acquisition means. The second voltage is applied before the timing acquired in step (1).

  According to a third aspect of the present invention, in the first aspect of the present invention, the second voltage applying unit is configured such that when a predetermined elapsed time has elapsed since the last application of the second voltage has elapsed, The second voltage is applied.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the first voltage is a voltage equal to or higher than the second voltage, and the first deflector operates in the operation of the optical deflector. A first voltage that is equal to or higher than the second voltage is always applied to the electrode and the second electrode, and the second voltage applying means is configured to apply the first voltage and the second voltage. The second voltage is applied when a predetermined elapsed time elapses after the application of any one of the above is completed.

  According to a fifth aspect of the present invention, in the first aspect of the invention, the second voltage applying means controls the second voltage applied first to continue to be applied as a bias. .

According to a sixth aspect of the present invention, there is provided an electro-optic crystal having an electro-optic effect, wherein a space charge is generated in the interior by applying a voltage and a gradient of an electric field is generated; Operation of an optical deflector including a first electrode disposed on a first surface of an optical crystal and a second electrode disposed on a second surface opposite to the first surface of the electro-optic crystal A first voltage applying step of applying a first voltage for operation of the optical deflector between the first electrode and the second electrode ; And a second voltage application step of applying a second voltage between the first electrode and the second electrode so that a deflection angle is constant with respect to the time axis when the first voltage is applied. It is characterized by that.

  The invention described in claim 7 further comprises a timing acquisition step of acquiring timing for applying the first voltage in the invention of claim 6, wherein the second voltage application step is the timing acquisition. The second voltage is applied before the timing acquired in the process.

  The invention according to claim 8 is the invention according to claim 6, wherein in the second voltage application step, when a predetermined elapsed time has elapsed since the last application of the second voltage has been completed, The second voltage is applied.

  According to a ninth aspect of the present invention, in the sixth aspect of the invention, the first voltage is a voltage equal to or higher than the second voltage, and the first deflector is operated during the operation of the optical deflector. A first voltage that is equal to or higher than the second voltage is constantly applied to the electrode and the second electrode, and the second voltage application step includes the first voltage and the second voltage. The second voltage is applied when a predetermined elapsed time has elapsed since the end of the application of either one of the above.

  According to a tenth aspect of the present invention, in the sixth aspect of the invention, the second voltage applying step controls the second voltage applied first to continue to be applied as a bias. .

  According to the present invention, when the voltage for the deflection operation is applied, the filling of the electrons into the trap level of the electro-optic crystal is in a state in which the deflection angle within the allowable range can be output, so the deflection operation is started. It is possible to shorten the time to do.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings described below, components having the same function are denoted by the same reference numerals, and repeated description thereof is omitted.
In one embodiment of the present invention, KTN (KTa _1-x Nb _x O ₃ (0 <x <1)) and KLTN (K _1-y Li _y Ta _1-x Nb _x O ₃ (0 <x <1, An electro-optic crystal having an electro-optic effect such as 0 <y <1)), and an electrode for applying an electric field to the electro-optic crystal, and the electro-optic crystal produced by applying a voltage to the electrode The optical deflector for deflecting light is controlled by the gradient of the refractive index.

FIG. 1 is a diagram showing a configuration of an optical deflector using an electro-optic crystal according to an embodiment of the present invention.
In FIG. 1, an optical deflector 10 includes a rectangular electro-optic crystal 11 such as KTN or KLTN, a positive electrode 12 formed on a first surface of the electro-optic crystal 11, and a first surface of the electro-optic crystal 11. The negative electrode 13 formed in the 2nd surface which opposes is provided. The positive electrode 12 and the negative electrode 13 are in ohmic contact with the electro-optic crystal 11. The positive electrode 12 and the negative electrode 13 are connected to a DC power source 14. The DC power supply 14 is connected to a control unit (not shown) for controlling the optical deflector 10.

FIG. 2 is a block diagram showing a schematic configuration of the control unit.
The control unit 20 includes a CPU 21 that executes processing operations such as various calculations, controls, and determinations, and a ROM 22 that stores a control program and the like for each process related to the optical deflector executed by the CPU 21. Further, the control unit 20 includes a RAM 23 for temporarily storing data during the processing operation of the CPU 21, input data, and the like. The control unit 20 is connected to an input operation unit 24 including a keyboard or various switches for inputting predetermined commands or data. Further, a DC power source 14 is connected to the control unit 20 via a drive circuit 25. The CPU 21 controls the driving of the DC power supply 14 via the driving circuit 25 in accordance with a processing procedure program stored in the ROM 22.

  In such a configuration, when a voltage is applied to the positive electrode 12 and the negative electrode 13, the positive electrode 12 and the negative electrode 13 are in ohmic contact, so that electrons are injected from the negative electrode 13 into the electro-optic crystal 11. Space charge is generated. This space charge causes a gradient of the electric field in the electro-optic crystal 11, and a gradient of the refractive index occurs due to the gradient of the electric field. Therefore, when incident light enters the electro-optic crystal 11 at this time, the emitted light is deflected by the gradient of the refractive index.

  In this way, a large deflection angle can be obtained by using the electro-optic crystal 11 and the simple and symmetrical structure of the positive electrode 12 and the negative electrode 13. Further, the deflection angle of the deflected beam can be temporally changed by applying an AC voltage between the electrodes instead of the DC voltage.

Now, trap levels exist inside the electro-optic crystal 11 and at the interfaces between the electro-optic crystal 11 and the positive electrode 12 and the negative electrode 13.
FIG. 3 is an energy band diagram for explaining the existence of trap levels in the electro-optic crystal or at the interface between the electro-optic crystal and the electrode.
As shown in FIG. 3, when electrons are not injected from the electrode into the electro-optic crystal (charge injection), a part of the trap level 31 is filled with electrons 32, but an empty trap level is also present. Exists. That is, in FIG. 1, when no voltage is applied to the positive electrode 12 and the negative electrode 13, the trap levels existing in the electro-optical crystal 11 or at the interface between the electro-optical crystal 11 and the positive electrode 12 and the negative electrode 13 are empty. A trap level exists.

Next, when a voltage equal to or higher than the voltage V _TFL (described later) is applied to the electrode, the relationship between the applied voltage and the current deviates from Ohm's law, and a large amount of electrons are injected from the electrode into the electro-optic crystal. A part of the injected electrons starts to be trapped in the empty trap level. That is, in FIG. 1, electrons are injected from the negative electrode 13 to the electro-optic crystal 11 by applying a voltage equal to or higher than the voltage V _TFL , and some of the injected electrons fill the empty trap levels.

For example, when voltage application (> V _TFL ) is started between the electrodes at a certain time and electrons are injected from the electrodes into the electro-optic crystal, a part of the injected electrons 41 is trapped as shown in FIG. A large number of trap levels 31 are trapped by the empty one of 31 and filled with injected electrons 41.

In the present specification, regardless of the number of empty trap levels that exist, the inside of the electro-optic crystal and the electro-optic crystal and the electrode in contact with the electro-optic crystal after applying a predetermined voltage equal to or higher than V _TFL The time required for almost all of the empty trap levels existing at the interface to be filled with the injected electrons will be referred to as T _filled . This T _filled is determined by the number of empty trap levels present in the electro-optic crystal or at the interface between the electro-optic crystal and the electrode, and is not a unique time. That is, when there are many empty trap levels when a predetermined voltage equal to or higher than V _TFL is applied, T _filled becomes long, and when there are not many empty trap levels, T _filled is short. Become.

After the trap level is almost filled as described above (after T _{filled has} elapsed), as shown in FIGS. 5A and 5B, the spatial distribution of electrons (space charge) in the electro-optic crystal 11 and The spatial distribution of the electric field does not depend on time. Since the deflection angle of the optical deflector 10 is determined by the spatial distribution of the electric field in the electro-optic crystal 11 by applying a voltage (distribution of the electric field gradient), the spatial distribution of the electric field in time as shown in FIG. The less dependent, the smaller the change in deflection angle with time. That is, the deflection angle is uniquely determined by the value of the applied voltage. This state is shown in FIG.

  FIG. 6A is a diagram showing the change over time of the voltage applied to the positive electrode 12 and the negative electrode 13, and FIG. 6B is a graph showing the applied voltage to the positive electrode 12 and the negative electrode 13 in FIG. It is a figure which shows the time-dependent change of a deflection angle in the case of changing with time as shown.

When an instruction for a deflection operation is input by the user via the input operation unit 24, the CPU 21 drives the DC power supply 14 and applies the voltage V ₁ to the electro-optic crystal 11 by the positive electrode 12 and the negative electrode 13 for a time t _1. Control to apply. That is, in response to the user input, as shown in FIG. 6 (a), voltages V ₁ at time 0 is applied to the positive electrode 12 and the negative electrode 13, and terminates the voltage application at time t _1.

At this time, if the voltage V ₁ is equal to or higher than V _TFL , a large amount of electrons are injected from the electrode into the electro-optic crystal, and therefore, from time 0 to time t ₂ (t ₂ <t ₁ ) in FIG. The time T _filled and the electrons injected from the negative electrode 13 into the electro-optic crystal 11 fill the empty trap level present in the electro-optic crystal 11, and at time t ₂ (after T _{filled has} elapsed) Almost all of the levels are filled with electrons. From time t ₂ to time t ₁ , the electron density and electric field magnitude in the electro-optic crystal 11 are as shown in FIGS. 5A and 5B, so that the deflection angle is constant regardless of time. Value. That is, a deflection angle uniquely determined by the voltage V ₁ (≧ V _TFL ) can be obtained.

Then, at time t _1, as shown in FIG. 6 (a), consider the case of off the voltage applied to the electrodes. When the applied voltage is turned off in this way, as shown in FIG. 7, electrons existing in the conduction band of the electro-optic crystal move to the electrode relatively quickly and disappear.

However, the electrons 71 filled in the trap level 31 remain trapped in the trap level. That is, the electrons 71 captured in the trap level 31 jump out of the trap level 31 due to thermal re-emission, but it takes time T _detrap until the jumping out of the electron 71 from the trap level 31 is completed. That is, in FIG. 6B, no voltage is applied to the positive electrode 12 and the negative electrode 13 from time t ₁ to t ₃ (t ₁ <t ₃ ) after the elapse of time T _detrap . Since a voltage higher than _VTFL is not applied, among the electrons trapped in the trap level, the electrons jump out of the trap level due to thermal re-emission, and the trap level is filled with time. The number of electrons gradually decreases.

Then, at time t _3, as shown in FIG. 8, the electron emission from the trap level 31 due to thermal re-emission is completed. Note that, as described with reference to FIG. 3, even when the emission of the electrons is completed, a part of the trap level 31 may be filled with electrons.

Time t ₃ state subsequent trap level, because the time 0 is equivalent to the previous trap level, time t ₃ or later again, when a voltage is applied for the deflection, the deflection angle until a lapse of the time T _[filled Is not stable as shown in FIG. That is, in order to obtain a stable deflection angle, it takes time T _filled necessary to fill substantially all trap levels with electrons in order to realize the stable deflection angle.

In one embodiment of the present invention, the accuracy of the output deflection angle may not be high, that is, the instability of the deflection angle may be allowed to some extent even if it is not the most stable deflection angle. is there. That is, when only time has elapsed T _[filled by applying a voltage, as shown in FIG. 6 (b), but becomes stable deflection angle theta _a is output, in some cases, the deflection angle theta _b If acceptable accuracy of the deflection angle if between deflection angle theta _a also.

As can be seen from the above, the filling of electrons into the trap level and the deflection angle are related, and when a voltage V ₁ (≧ V _TFL ) is applied, the deflection angle Therefore, the trap level is filled with electrons corresponding to the above. For example, in the case of outputting the most stable deflection angle, it can be said that substantially all of the trap levels are filled with electrons, and the electron filling and the thermal re-emission of electrons with respect to the trap levels are in an equilibrium state. If the realized deflection angle is not stable, the electron filling state of the trap level at one moment and the electron filling state of the trap state at the next moment are different. The horn changes with time.

Therefore, when the instability of the deflection angle is allowed to some extent, it is sufficient that the trap level corresponding to the deflection angle allowed as instability is filled (captured). Therefore, in this case as well, in order to obtain an allowable deflection angle, it takes time T _comp required to at least complete the filling of electrons into the trap level corresponding to the allowable deflection angle.

In one embodiment of the present invention, in the deflection operation, for example, until the filling of electrons into the trap level necessary to achieve a deflection angle within an allowable range, such as time T _filled and time T _comp , is completed. It is essential to realize a deflection angle within the allowable range without waiting for the elapse of time. Therefore, in one embodiment of the present invention, a voltage higher than V _TFL is applied to the electrode for applying a voltage to the electro-optic crystal at a stage before the voltage for deflection is applied. In order to realize an electron-filled state of trap levels, the trap levels are filled with electrons as much as necessary.

  In this way, prior to the voltage application for deflection, the trapped state electron capture (filling) state is set so that at least the accuracy of the minimum deflection angle can be achieved, thereby applying the voltage for deflection. Sometimes it is possible to achieve a deflection angle output within an acceptable range.

Here, the voltage V _TFL is a current-voltage characteristic measured when a voltage is applied to an optical deflector including an electro-optic crystal in which electrodes are arranged on two opposing surfaces, such as the optical deflector 10 shown in FIG. It can be found experimentally as a voltage that deviates from a region where the current is proportional to the voltage.

FIG. 9 is a diagram for explaining how to obtain the voltage V _{TFL according} to an embodiment of the present invention, and shows a log-log plot of current-voltage characteristics when KTN is used as the electro-optic crystal 11. FIG.
In FIG. 9, a region 91 is a voltage range in which a current is proportional to the voltage when a voltage is applied to the positive electrode 12 and the negative electrode 13, and a region 92 is a voltage when a voltage is applied to the positive electrode 12 and the negative electrode 13. This is a voltage range in which the current is proportional to the square of the voltage.

As can be seen from FIG. 9, when a voltage is applied to the positive electrode 12 and the negative electrode 13, the applied voltage and the current are in a proportional relationship within the region 91. That is, the applied voltage and current follow Ohm's law. At this time, the voltage is increased, and when the voltage reaches 93, the relationship between the applied voltage and the current deviates from Ohm's law. In the region 91 where the relationship between the applied voltage and the current follows Ohm's law, the injection of electrons from the negative electrode 13 to the electro-optic crystal 11 is negligible, but is negligible. However, when the voltage is 93 or more, a large amount of electrons are injected from the negative electrode 13 to the electro-optic crystal 11. In one embodiment of the present invention, this voltage 93 is the voltage V _TFL .

That is, in this specification, the “voltage V _TFL ” is a voltage at which the applied voltage and the current deviate from the proportional state when the relationship between the voltage applied to the electrode provided in the optical deflector and the current is measured. Thus, when the relationship between the applied voltage and the current follows Ohm's law, a larger amount of electrons are injected from the electrode into the electro-optic crystal than in the electrode, and the space charge limited state is achieved. Refers to the voltage.

That is, in the optical deflector of the present invention, in order to realize optical deflection, it is important to distribute the space charge in the electro-optic crystal and apply a gradient of the electric field when applying a voltage. It is necessary to inject electrons from the electrode into the electro-optic crystal by applying a predetermined voltage. As described above, even when the relationship between the applied voltage and the current follows Ohm's law, a small amount of electrons are injected from the electrode into the electro-optic crystal, but this is small enough to be ignored. . However, when the relationship between the applied voltage and the current deviates from Ohm's law, electrons are injected from the electrode to the electro-optic crystal so that a sufficient gradient of the electric field can be realized, and part of the injected electrons. Are trapped (filled) in the trap level. In one embodiment of the present invention, before applying a voltage for deflection, a trap state (filling state) of electrons in a trap level for realizing a desired range of deflection angle (deflection angle within an allowable range). ) Must be formed, and a large amount of electron injection is required to form the trap state. That is, electron injection is required when the relationship between the applied voltage and the current deviates from Ohm's law, and in one embodiment of the present invention, the voltage when deviating from Ohm's law is the voltage V _TFL .

In a deflector having an electro-optic crystal such as KTN, the deflection angle fluctuates over time from application of a voltage equal to or higher than V _TFL to T _filled, and becomes stable when more time elapses. Further, the deflection angle does not become zero immediately after the electric field is turned off, and approaches zero in a finite time. Therefore, in one embodiment of the present invention, V _TFL is obtained according to the electro-optic crystal used for the optical deflector and the electrode for applying a voltage to the electro-optic crystal, and a predetermined voltage equal to or higher than the V _TFL is applied. By measuring the time dependence of the deflection angle, the time dependence of the deflection angle as shown in FIG. 6B can be obtained. From the time dependence of the deflection angle, T _filled , T _comp , T _detrap can be determined.

The KTN and KLTN exhibit a large secondary electro-optic effect when an electric field is applied in the crystal axis direction. The value is 2 × 10 ⁻¹⁴ m ² / V ² , and the nonlinear constant is 2000 pm / V or more at the time of DC bias of 100 V / mm, and LiNO ₃ (LN), which is a material having a primary electro-optic effect, It is significantly larger than the nonlinear constant of 30 pm / V. Furthermore, KTN and KLTN can change the phase transition temperature from paraelectricity to ferroelectricity from almost absolute zero to 400 ° C. by changing the composition ratio of Ta and Nb. Therefore, the operating temperature can be set as desired, such as room temperature, without using a temperature controller. Thus, KTN and KLTN are preferable materials for the optical deflector.

In addition, in one embodiment of the present invention, for example, LiNbO ₃ , LiTaO ₃ , LiIO ₃ , KNbO ₃ , KTiOPO ₄ , BaTiO ₃ , SrTiO ₃ , Ba _1-x Sr _x TiO ₃ (0 <x <1), _{Ba 1-x Sr x Nb 2} O 6 (0 <x <1), Sr 0.75 Ba 0.25 Nb 2 O 6, Pb 1-y La y Ti 1-x Zr x O 3 (0 <x <1,0 < y <1), Pb (Mg _1/3 Nb _2/3 ) O ₃ —PbTiO ₃ , KH ₂ PO ₄ , KD ₂ PO ₄ , (NH ₄ ) H ₂ PO ₄ , BaB ₂ O ₄ , LiB ₃ O ₅ Electro-optic crystals of CsLiB ₆ O ₁₀ , GaAs, CdTe, GaP, ZnS, ZnSe, ZnTe, CdS, CdSe, and ZnO can be used.

(First embodiment)
In one embodiment of the present invention, for example, a spectroscope in which a deflection time is set in advance, a display that performs a deflection operation when a predetermined time is reached, and the timing for applying a voltage for deflection are set in advance. Can be applied to any configuration. In the present embodiment, a mode in which the control unit recognizes the timing of applying a voltage for deflection will be described.
FIG. 10 is a flowchart for optical deflection control according to the present embodiment. FIG. 13 is a diagram showing a change over time in the deflection angle in the optical deflection control of the present embodiment. In FIG. 13, the solid line indicates the time dependence of the deflection angle when the trap level filling voltage is larger than the voltage for deflection operation (deflection operation voltage). The broken line indicates the time dependence of the deflection angle when the trap level filling voltage is smaller than the voltage for deflection operation (deflection operation voltage).
In FIG. 10, as an example, a case of realizing the deflection angle of the deflection angle theta _a in FIG. 13, performs two deflection operation, setting a timing for performing the deflection operation of each of the two in advance Shall be. Therefore, it is assumed that the RAM 23 holds the time for performing the deflection operation for each of the two times. The control unit further includes a clock.

  In FIG. 10, a case has been described in which the control unit recognizes the timing of two deflection operations in advance, but the deflection operation is not limited to two. In other words, in the present embodiment, the voltage application (the trap level filling voltage of the trap level filling voltage) is prepared as a preparation for realizing a deflection angle within an allowable range before the voltage application timing for the deflection recognized by the control unit. The number of times of voltage application for deflection is not limited to the above two times, but may be one time or three or more times.

  In the present embodiment, a case will be described in which the trap level filling voltage described later is larger than the voltage for the deflection operation.

In step 1001, the CPU 21 acquires the timing for performing the deflection operation based on the user input. That is, at time T ₀ , the time T ₁ (> T ₀ ) at which the user performs the first deflection operation and the time T ₂ (> T at which the _second deflection operation is performed) via the input operation unit 24. If you enter _1), CPU 21 stores in RAM23 the time _{T 1} and _{T 2,} which is the input as the first timing and the second timing.
In step 1002, the CPU 21 acquires a time T ₁ for performing the first deflection operation from the RAM 23.

In step 1003, the CPU 21 refers to the clock and, as shown in FIG. 13, when the time T _filled before the time T ₁ acquired in step 1002 (time T _a1 ; T _a1 <T ₁ ) is reached. Control is performed such that a predetermined voltage equal to or higher than the voltage V _TFL (hereinafter also referred to as “trap level filling voltage”) is applied to the positive electrode 12 and the negative electrode 13 for a time T _filled . That is, the CPU 21 controls to apply the trap level filling voltage so that the realized deflection angle is constant with respect to the time axis when the voltage for the deflection operation is applied. Thus, by applying the trap level filling voltage in advance, the trap level is substantially filled so that the deflection angle does not have time dependency.

In the present embodiment, as described above, since the trap level filling voltage is larger than the voltage for the deflection operation, the trap level is substantially filled with electrons at time T ₁ after T _filled from time T _a1. At the same time, more electrons are present in the conduction band than when a voltage for deflection operation is applied. Therefore, the deflection angle θ _c realized after T _{filled has} elapsed since the trap level filling voltage was applied at time T _a1 is larger than the deflection angle θ _a desired to be realized during the deflection operation.

In Step 1004, the CPU 21 controls to apply a voltage for the first deflection operation to the electro-optic crystal 11 at time T ₁ . At this time, in response to the change in the applied voltage from the trap level filling voltage to the deflection operation voltage, the conduction band electronic state is also changed from the trap level filling voltage application to the deflection operation voltage. It changes at the time of application. So deflection angle is realized when applying a voltage for deflecting operation theta _a, as shown in FIG. 13, the deflection angle also changes discontinuously in theta _a from theta _c at time T _1.

When the trap level filling voltage is equal to the voltage for the deflection operation, the deflection angle θ _c is equal to the deflection angle θ _a , so that the realized deflection angle continuously changes at time T ₁ .

In the present embodiment, a state capable of realizing the deflection angle of the deflection angle theta _a is a deflection angle within the allowable range as a deflection angle when the voltage for the already applied voltage deflection operation in the previous stage of step 1004 Therefore, a desired deflection angle can be realized without waiting time at the timing of applying a voltage for deflection to the positive electrode 12 and the negative electrode 13.

In step 1005, the CPU 21 acquires time T ₂ for performing the second deflection operation from the RAM 23.

In step 1006, the CPU 21 refers to the clock, and when the time T _filled before the time T ₂ acquired in step 1005 (time T _a2 ; T _a2 <T ₂ ), the trap level filling voltage is obtained. _Is applied to the positive electrode 12 and the negative electrode 13 for a time T _filled .

In step 1007, the CPU 21 controls to apply a voltage for the second deflection operation to the electro-optic crystal 11 at time T ₂ . In this embodiment, possible states realizing the deflection angle of the deflection angle theta _a is a deflection angle within the allowable range as a deflection angle when the voltage for the previous already stage, applied voltage deflection operations of steps 1007 Therefore, a desired deflection angle can be realized without waiting time at the timing of applying a voltage for deflection to the positive electrode 12 and the negative electrode 13.

In the present embodiment has explained the case to achieve a stable deflection angle theta _a as the deflection angle, depending on the system used, a stable range of the deflection angle theta _a deflection angle having a certain range (theta _b and sometimes deflection angle) can be tolerated between the theta _a. That is, in this embodiment, some systems, stable operation at 80% or more of the deflection angle of the deflection angle theta _a is not a problem. In this case, in steps 1003 and 1006, a trap level filling voltage may be applied when the time T _comp before T ₁ and T ₂ is reached.

As described above, in this embodiment, when the control unit recognizes the timing of the deflection operation (timing of voltage application for deflection) in advance, the voltage V precedes the timing by the time T _filled or T _{comp. Since} a voltage equal to or higher than _TFL is applied, a deflection angle with a desired accuracy can be realized during a desired deflection operation.

In the above description, the trap level filling voltage is larger than the voltage for the deflection operation. However, even if the trap level filling voltage is smaller than the voltage for the deflection operation. good. In this case, as shown in FIG. 13, the times T _b1 and T _b2 for applying the trap level filling voltage are earlier than the times T _a1 and T _a2 , respectively. That is, T _filled when the trap level filling voltage is smaller than the voltage for the deflection operation is larger than T _filled when the trap level filling voltage is larger than the voltage for the deflection operation.

Further, when the trap level filling voltage is smaller than the voltage for the deflection operation, the trap level is substantially filled with electrons at time T ₁ after T _filled from time T _b1 , and the conduction band is also filled in the conduction band. There will be fewer electrons than when a voltage for deflection operation is applied. Therefore, the deflection angle θ _d realized after T _{filled has} elapsed since the trap level filling voltage was applied at time T _b1 is smaller than the deflection angle θ _a desired to be realized during the deflection operation. Therefore, as shown in FIG. 13, the deflection angle also changes discontinuously in theta _a from theta _d at time T _1.

(Second Embodiment)
In the present embodiment, a mode in which the control unit does not recognize in advance at which timing the deflection operation is performed will be described. In other words, in the present embodiment, after applying a voltage equal to or higher than the voltage V _{TFL for} a time at least realizing the filling state of electrons necessary to realize a deflection angle within an allowable range, regardless of the deflection operation. When a predetermined time has elapsed (according to a certain rule), a voltage equal to or higher than the voltage V _TFL is applied, or the trap level filling voltage is always set from when the device is turned on or when the first trap level filling voltage is applied. By continuing to apply the voltage, a deflection angle within an allowable range can be output whenever a voltage for deflection is applied.

FIG. 11 is a flowchart for optical deflection control according to the present embodiment. In FIG. 11, the next trap level filling voltage is applied after the elapse of a predetermined elapsed time, which will be described later, from the end of the previous application of the trap level filling voltage, regardless of the application of the voltage for the deflection operation during that time. The form to perform is demonstrated.
In FIG. 11, as in the case of FIG. 10, the case where the deflection angles θ _{a to} θ _e of FIGS. 15 and 16 are realized will be described as an example. The control unit further includes a timer.

In step 1101, when the optical deflector 10 is turned on, the CPU 21 controls the trap level filling voltage to be applied to the positive electrode 12 and the negative electrode 13 for the time T _filled . At this time, the CPU 21 starts a timer after the application of the trap level filling voltage is finished, and starts measuring the elapsed time after the application of the trap level filling voltage is finished.

  In step 1102, the CPU 21 determines whether or not the user has input an instruction regarding the deflection operation. When the user instructs the deflection operation via the input operation unit 24, the CPU 21 determines that there is an instruction for the deflection operation based on the user input, and proceeds to Step 1103, where the user input instructs the deflection operation. If it is determined that there is no, the process proceeds to step 1104.

In step 1103, the CPU 21 controls to apply a voltage for the deflection operation to the positive electrode 12 and the negative electrode 13. In this embodiment, the trap level filling voltage is applied for the time T _filled when the power is turned on. Therefore, when the instruction for the deflection operation is input after the power is turned on, the applied voltage is the trap level filling voltage. the deflection angle are ready for realizing the deflection angle of theta _a, it is possible to apply a voltage for deflecting latency without.

  In step 1104, with reference to the timer started in step 1101, it is determined whether or not a predetermined elapsed time has elapsed from the end of the previous application of the trap level filling voltage to the present. If it is determined that the predetermined elapsed time has not elapsed, the process returns to step 1102. On the other hand, if it is determined that the predetermined elapsed time has elapsed, the process proceeds to step 1105.

Note that the predetermined elapsed time refers to a time during which a deflection angle within the allowable range (here, θ _{a to} θ _e ) can be realized within the time. As described above, when the voltage application of the voltage V _TFL or higher such as the trap level filling voltage is turned off, electrons are gradually emitted from the trap level over time due to thermal re-emission, and the allowable deflection angle is eventually increased. It becomes impossible to realize. That is, the period during which the deflection angle within the allowable range can be realized is determined, and this period is called a predetermined elapsed time. The predetermined elapsed time can be experimentally obtained according to the range of the deflection angle to be realized and the material of the electro-optic crystal to be used.

In step 1105, the CPU 21 controls the trap level filling voltage to be applied to the positive electrode 12 and the negative electrode 13 for a time T _filled . At this time, the CPU 21 resets the time measured by the current timer, starts the timer again after the application of the trap level filling voltage is completed, and fills the trap level which is a predetermined voltage equal to or higher than V _TFL. The measurement of the elapsed time after the application of the working voltage is started. As described above, since the voltage for preparation for the realization of the deflection angle within the allowable range (voltage equal to or higher than the voltage V _TFL ) is applied for at least the time T _filled at every predetermined elapsed time, when the instruction of the deflection operation is performed. Even when the voltage for deflection is applied, it is possible to realize an electron filling state of a desired trap level.

  In step 1106, as in step 1102, the CPU 21 determines whether or not the user has input an instruction regarding the deflection operation. When the user instructs the deflection operation via the input operation unit 24, the CPU 21 determines that there is an instruction for the deflection operation based on the user input, and proceeds to step 1108, where the user input that instructs the deflection operation. If it is determined that there is no, the process proceeds to step 1107.

  In step 1107, the CPU 21 refers to the timer to acquire the elapsed time from the end of the previous application of the trap level filling voltage, and whether the acquired elapsed time has passed the predetermined elapsed time. Judge whether or not. When it is determined that the time has elapsed, it is necessary to fill the trap level with electrons, and the process proceeds to step 1105. On the other hand, if it is determined that it has not elapsed, even if there is an instruction for a deflection operation in the current state, the deflection angle within the allowable range can be output.

  In step 1108, the CPU 21 controls to apply a voltage for the deflection operation to the positive electrode 12 and the negative electrode 13. In this embodiment, since the trap level is filled with electrons to the extent that a deflection angle within an allowable range can be realized in the stage before this step, it is possible to apply a voltage for deflection without waiting time. it can.

  In step 1109, the CPU 21 determines whether there is a user input related to power-off of the optical deflector 10. When the power-off is instructed by the user, the CPU 21 performs control related to power-off and ends. On the other hand, if the user is not instructed to turn off the power, the process proceeds to step 1110.

  In step 1110, the CPU 21 refers to the timer to acquire the elapsed time from the end of the previous application of the trap level filling voltage, and whether the acquired elapsed time has exceeded a predetermined elapsed time. Judge whether or not. When it is determined that the time has elapsed, it is necessary to fill the trap level with electrons, and the process proceeds to step 1105. On the other hand, if it is determined that it has not elapsed, even if there is an instruction for a deflection operation in the current state, the deflection angle within the allowable range can be output.

14A, 14B to 16A, 16B, the time dependence of the deflection angle when the voltage for the deflection operation according to this embodiment is applied at an arbitrary time. Will be explained.
FIG. 14A is a diagram showing the time dependence of the trap level filling voltage when the voltage for the deflection operation is not applied, and FIG. 14B is the timing shown in FIG. It is a figure which shows the time dependence of the deflection angle implement | achieved at the time of applying the voltage for trap level filling.
In FIG. 14A, when time 0 (= T _β1 ) is reached, the trap level filling voltage V _filled is applied for T _first-filled . Since the trap level is filled with electrons from this time, the deflection angle to be realized increases with time. At time T _α1 (after T _first-filled ), the trap level is almost filled with electrons. As a result, a large number of electrons also exist in the conduction band. _{Let the} deflection angle realized at this time be θ _a ′.

In this specification, “T _αn (n: natural number)” refers to the time when the trap level filling voltage is turned off, and “T _βn (n; natural number)” refers to the trap level filling voltage. Refers to the time at which application of.

When the voltage is turned off at time T _α1 , electrons existing in the conduction band disappear, so that the deflection angle realized as shown in FIG. 14B becomes steeply small (deflection angle θ _a ″), and then the trap Since electrons are gradually re-emitted from the level, the realized deflection angle is gradually reduced. At this time, by applying the following trap level filling voltage after a predetermined time has elapsed from the time T _{[alpha] 1,} it is possible to re-fill the minute electrons above reemitted. Therefore, as shown in FIG. 14A, when T _β2 , which is a time after a predetermined time has elapsed from time T _α1 , the trap level filling voltage V _filled is applied for T _{second-filled} .

Note that, as described above, T _filled is a predetermined voltage equal to or higher than V _TFL regardless of the state of filling of electrons at the trap level (whether it is almost empty or a predetermined trap level is filled). Is the time required from the start of the application until almost all empty trap levels are filled with electrons. Therefore, when a trap level filling voltage is applied when almost all trap levels are empty (time T _β1 ), the trap level filling voltage is applied because the number of trap levels to be filled is large. The time to do is relatively large. On the other hand, when the trap level filling voltage is applied when most of the trap levels are filled with electrons (time T _β2 , time T _β3 , time T _β4 ), the number of trap levels to be filled is Therefore, the time for applying the trap level filling voltage is relatively small. As described above, T _filled relatively changes depending on the trap level filling state when the trap level filling voltage is applied, and thus T _first-filled becomes larger than T _{second-filled} .

In FIG. 14B, when the trap level filling voltage V _filled is applied at the time T _β2 , the deflection angle realized is sharply increased. This is because the electrons in the conduction band are applied by the application of the trap level filling voltage. This is because of the inflow. That is, the deflection angle is increased by the electrons that are present in the conduction band by applying a voltage. Then, in the time from time _Tβ2 to time _Tα2 , the vacant trap level is filled with electrons.

In the present embodiment, the time between the time T _α1 when the previous trap level filling voltage is turned off and the time T _β2 when the application of the next trap level filling voltage is started is defined as a predetermined elapsed time. Therefore, even when the trap level filling voltage is turned off at time _Tα1 , the trap level is filled with electrons that can stably realize an allowable deflection angle. Become. Therefore, as will be described later with reference to FIGS. 15A and 15B and FIGS. 16A and 16B, a stable deflection angle within an allowable range can be realized regardless of the deflection operation. Can do.

  FIG. 15A is a diagram showing the time dependence of the applied voltage when a voltage for the deflection operation is applied (when the voltage for the deflection operation is larger than the trap level filling voltage). FIG. 15B is a diagram showing the time dependence of the deflection angle realized when a voltage is applied at the timing shown in FIG. FIG. 16A is a diagram showing the time dependence of the applied voltage when a voltage for the deflection operation is applied (when the voltage for the deflection operation is smaller than the trap level filling voltage). FIG. 16B is a diagram showing the time dependence of the deflection angle realized when a voltage is applied at the timing shown in FIG.

In FIG. 15 and FIG. 16, “V _active ” indicates a voltage for the deflection operation, and “T _active ” indicates an application time of the voltage V _active for the deflection operation.

15A and 15B, when the voltage for the deflection operation is applied at an arbitrary time when the voltage V _active for the deflection operation is larger than the trap level filling voltage V _filled. The time dependence of the deflection angle will be described.
In FIG. 15A, reference numeral 1501 denotes a voltage for the deflection operation when the voltage V _active for the deflection operation is applied immediately before the trap level filling voltage is applied (time T _β2 ). Reference numeral 1502 denotes a voltage for the deflection operation when the voltage V _active for the deflection operation is applied immediately after the trap level filling voltage is turned off (time T _α3 ), and reference numeral 1503 denotes the deflection operation. For the deflection operation when the voltage V _active is applied after a certain time has elapsed since the trap level filling voltage is turned off.

In FIG. 15 (b), if the voltage 1501 for deflecting operation is applied at time T _.beta.2, instead of the trap level filling voltage V _[filled, voltage V _active for deflecting operation is applied While I, as described with reference to FIG. 14, at time T _.beta.2, somewhat are electrons are re-emitted from the trap level, the allowable range of deflection angles theta _a to be realized (FIG. 15 (b) The trap level is filled with electrons that can realize the deflection angles θ _{e to} θ _a ). Therefore, even if the voltage V _active for the deflection operation is applied at time T _β2 , at least the deflection angle θ _e can be realized, and then the trap level vacant during T _active is filled with electrons, thereby deflecting it is possible to realize the angle θ _a.

When voltage 1502 for deflection operation is applied, trap level filling voltage V _filled is turned off at time _Tα3 , but voltage V _active for deflection operation is applied. At this time, the electrons in the trap levels is substantially filled, it is possible to realize a deflection angle theta _a in voltage 1502 for deflecting operation.

Further, when the voltage 1503 for the deflection operation is applied, the trap level filling voltage V _filled is not applied, but is within a predetermined elapsed time from the time when the previous trap level filling voltage is turned off. since, although some are electrons are re-emitted from the trap level of electrons enough to achieve a deflection angle of the allowable range of deflection angles theta _a to be realized is filled in the trap level. Therefore, even in this case, when the voltage 1503 for the deflection operation is applied, the trap level is sufficiently filled with electrons, and a deflection angle between the deflection angles θ _e and θ _a is realized. Can do. Then, electrons empty trap level by the voltage 1503 for deflecting operation can be realized deflection angle theta _a filled.

Also, with reference to FIGS. 16A and 16B, when the voltage V _active for the deflection operation is smaller than the trap level filling voltage V _filled , the voltage for the deflection operation is applied at an arbitrary time. The time dependence of the deflection angle at the time of performing will be described.
In FIG. 16A, reference numeral 1601 denotes a voltage for the deflection operation when the voltage V _active for the deflection operation is applied immediately before the trap level filling voltage is applied (time T _β2 ). Reference numeral 1602 denotes a voltage for the deflection operation when the voltage V _active for the deflection operation is applied immediately after the trap level filling voltage is turned off (time T _α3 ), and reference numeral 1603 denotes the deflection operation. For the deflection operation when the voltage V _active is applied after a certain time has elapsed since the trap level filling voltage is turned off.

In FIG. 16B, when the voltage 1601 for the deflection operation is applied, some electrons are re-emitted from the trap level at the time _Tβ2 . However, as described above, electrons enough to achieve a deflection angle theta _e in the allowable range of deflection angles theta _a to be realized is filled in the trap level. Therefore, even if the voltage V _active for the deflection operation is applied at time T _β2 , at least the deflection angle θ _e can be realized, and then the trap level vacant during T _active is filled with electrons, thereby deflecting it is possible to realize the angle θ _a.

When the voltage 1602 for the deflection operation is applied, the trap level filling voltage V _filled is turned off at the time _Tα3 , but the voltage V _active for the deflection operation is applied. At this time, the electrons in the trap levels is substantially filled, it is possible to realize a deflection angle theta _a in voltage 1602 for deflecting operation.

Further, when the voltage 1603 for the deflection operation is applied, the trap level filling voltage V _filled is not applied, but is within a predetermined elapsed time from the time when the previous trap level filling voltage is turned off. since, although some are electrons are re-emitted from the trap level of electrons enough to achieve a deflection angle of the allowable range of deflection angles theta _a to be realized is filled in the trap level. Accordingly, even in this case, when the voltage 1603 for the deflection operation is applied, the trap level is sufficiently filled with electrons, and a deflection angle between the deflection angles θ _e and θ _a is realized. Can do. Then, electrons empty trap level by the voltage 1603 for deflecting operation can be realized deflection angle theta _a filled.

As described above, in this embodiment, the trap level filling voltage is applied after a predetermined elapsed time after applying a predetermined voltage equal to or higher than the voltage V _TFL such as the trap level filling voltage. Whenever an operation instruction is input, the trap level in the electro-optic crystal can be always filled with electrons so that a deflection angle within an allowable range can be realized.

  In the present embodiment, as described above, it is important to be able to realize a deflection angle within an allowable range regardless of the instruction of the deflection operation. Therefore, the trap level filling applied first is not limited to the mode in which the next trap level filling voltage is applied after the elapse of the predetermined elapsed time from the end of the previous trap level filling voltage application or before the elapsed time. The working voltage may be always applied as a bias. In this case, when the power of the optical deflector 10 is turned on, the CPU 21 may control so that the trap level filling voltage is applied to the positive electrode 12 and the negative electrode 13 as a bias. Alternatively, the trap level filling voltage once applied may be continuously applied as a bias in response to a user input related to an instruction to apply the trap level filling voltage as a bias. The termination of the trap level filling voltage applied as the bias may be performed according to a user input related to the termination, or may be terminated when the power is turned off.

  In the present embodiment, it is not essential to apply the current trap level filling voltage before the predetermined elapsed time has elapsed since the end of the previous trap level filling voltage application. Even if it is carried out, it is essential to fill the trap level of the electro-optic crystal with electrons so that at least a deflection angle within an allowable range can be realized.

In the present embodiment, if the voltage for the deflection operation is always equal to or higher than V _TFL , after the application of the voltage for the deflection operation is completed, the electron filling state in the trap level of the electro-optic crystal 11 is At least a deflection angle within an allowable range can be realized. Therefore, in this embodiment, when the voltage for the deflection operation is always equal to or higher than V _TFL , the trap level filling voltage is applied before a predetermined elapsed time has elapsed after the voltage application for the deflection operation is completed. You may make it do.

In this case, in steps 1103 and 1108, the CPU 21 resets the time measured by the current timer, and starts measuring the elapsed time after the application of the voltage for the deflection operation is completed. In this case, both the voltage for the deflection operation and the trap level filling voltage become predetermined voltages equal to or higher than V _TFL , and in steps 1107 and 1110, the CPU 21 refers to the timer to perform the previous deflection operation. What is necessary is just to acquire the elapsed time from the end of voltage application and determine whether or not the elapsed time has passed a predetermined elapsed time.

(Third embodiment)
In the first and second embodiments, the time for applying a predetermined voltage equal to or higher than V _TFL is T _filled or T _comp , but is not limited to these times. In the present invention, it is sufficient that the trapping state (filling state) of electrons in the trap level is prepared in a desired state when a voltage for deflection is applied. That is, it is sufficient that the desired state can be formed prior to application of the voltage for deflection, and the time for applying the trap level filling voltage may be set to T _filled or T _comp or more.

In addition, in the elapsed time from application of a predetermined voltage (trap level filling voltage or voltage for deflection operation in some cases) higher than the previous V _TFL to application of the predetermined voltage higher than the current V _TFL Accordingly, the application time of the trap level filling voltage may be determined. As described above, after T _{detrap has} elapsed since the application of a predetermined voltage equal to or higher than V _TFL , such as a trap level filling voltage, the electron trapping state at the trap level returns to the initial state. In order to realize the deflection angle, it is necessary to apply a predetermined voltage equal to or higher than V _TFL by at least T _filled and T _comp .

However, when the elapsed time from the previous application to the current application of a predetermined voltage equal to or higher than V _TFL is within T _detrap , more electrons are filled in the trap level than in the initial state. Therefore, in this case, the time for applying a predetermined voltage equal to or higher than V _TFL applied for the purpose of forming a desired electron filling state may be shorter than T _filled or T _comp . That is, the trapped state electron capture state changes according to the elapsed time from the previous application to the current application of a predetermined voltage equal to or higher than V _TFL. If the relationship with the application time of the trap level filling voltage, which is at least necessary for realizing the angle, is obtained, the application time corresponding to the elapsed time can be determined using the relationship.

FIG. 15 is a diagram for explaining a case where the next trap level filling voltage is applied before T _detrap elapses after the previous trap level filling voltage is turned off. In FIG. 15, time T _c1 is the time when the previous trap level filling voltage is turned off, and time T _c2 is the time after T _{detrap has} elapsed from time T _c1 .

As described above, at the time between time T _c1 and time T _c2 , the trap level of the electro-optic crystal 11 is filled with more electrons than in the initial state. Therefore, the elapsed time T ′ _filled from when the trap level filling voltage is applied until the trap level is substantially _filled is smaller than T _filled . Therefore, T ′ _filled can be reduced by applying the next trap level filling voltage at time T _c3 between time T _c1 and time T _c2 .

Therefore, in the present embodiment, the relationship between the elapsed time and the application time of the trap level filling voltage that is at least necessary to realize the deflection angle within the allowable range is obtained by experiments, and the elapsed time and the above The application time is plotted, and the plotted result is stored in the RAM 23 as a table. In step 1003, step 1006, and step 1105, the CPU 21 determines whether or not the elapsed time from the end of application of the predetermined voltage equal to or higher than the previous V _TFL is less than T _detrap and determines that it is _{equal to} or higher than T _detrap. If so, the processing is performed as described in the first and second embodiments.

On the other hand, when determining that it is less than T _detrap , the CPU 21 refers to the above table, and trap level filling voltage according to the elapsed time from the end of application of a predetermined voltage equal to or higher than the previous V _TFL. And the trap level filling voltage may be applied during the extracted application time.

  Thus, what is important in the present invention is that by applying the trap level filling voltage prior to the application of the voltage for the deflection operation by the control performed by the control unit for controlling the optical deflector, At the time of applying a voltage for the deflection operation, at least the filling of electrons into the trap level necessary to realize a deflection angle within an allowable range is completed. In order to realize the completion state, for example, the trap level filling voltage is applied at the time described in the first to third embodiments.

(Fourth embodiment)
In the first to third embodiments, the DC power source is used as an example of the optical deflector 10, but an AC power source may be used.
12A to 12D are diagrams showing the relationship between the deflection angle and time when an AC voltage is applied according to the present embodiment.
FIG. 12A is a diagram showing the time change of voltage when a rectangular wave voltage having an amplitude of ± V ₀ (applied voltage period T _period <2T _filled ) is applied, and FIG. it is a graph showing a temporal change of the voltage in the case of applying a rectangular wave voltage (the applied voltage period T _period> 2T _filled) with an amplitude of V _0. FIG. 12B is a diagram showing the change over time in the deflection angle when the applied voltage changes with time as shown in FIG. 12A. FIG. 12D shows the applied voltage in FIG. It is a figure which shows a time-dependent change of a deflection angle in the case of changing over time as shown in (c).

(Other embodiments)
The above-described embodiment of the present invention can be applied to a system including a plurality of devices (for example, a computer, a scanner, a printer, a spectrometer, a display, etc.), or a single device (a scanner, a printer, a spectrometer, a display, etc.). It is also possible to apply to.

  Also, a control method for storing a program for operating each component so as to realize the functions of the above-described embodiment in a storage medium, reading the program stored in the storage medium as a code, and executing the program on a computer is also provided in the above-described embodiment. Included in the category. That is, a computer-readable storage medium is also included in the scope of the present invention. In addition to the storage medium storing the computer program, the computer program itself is included in the above-described embodiment.

It is a figure which shows the structure of the optical deflector using the electro-optic crystal based on one Embodiment of this invention. It is a block diagram which shows schematic structure of the control part which controls an optical deflector based on one Embodiment of this invention. It is an energy band figure for demonstrating that a trap level exists in the inside of an electro-optic crystal and the interface of an electro-optic crystal and an electrode based on one Embodiment of this invention. It is a figure which shows a mode that an electron is filled to a trap level when an electron is injected into an electro-optic crystal from the electrode by the voltage application to an electrode based on one Embodiment of this invention. (A) is the figure which shows the relationship between the position in the electro-optic crystal after applying T to the electro-optic crystal sandwiched between the electrodes and T _filled and the electron density, and (b) FIG. 4 is a diagram showing the relationship between the position in the electro-optic crystal and the magnitude of the electric field after T _filled after applying voltage to the electrode in the electro-optic crystal sandwiched between the electrodes. (A) is a figure which shows the time change of the voltage applied with respect to the electrode formed in the electro-optic crystal, (b) is a time change as the applied voltage to the said electrode shows to (a). It is a figure which shows the time-dependent change of a deflection angle in a case. It is an energy band figure just after the voltage application stop to the electro-optic crystal concerning one embodiment of the present invention. It is an energy band figure after T _detrap progress after the voltage application stop to an electro-optic crystal concerning one embodiment of the present invention. It is a figure for demonstrating how to obtain _| require voltage _{VTFL based} on one Embodiment of this invention. 6 is a flowchart for controlling light deflection according to an embodiment of the present invention. 6 is a flowchart for controlling light deflection according to an embodiment of the present invention. (A)-(d) is a figure which shows the relationship between a deflection angle and time at the time of applying the alternating voltage based on one Embodiment of this invention. It is a figure which shows the time-dependent change of a deflection angle at the time of control of the optical deflection shown in FIG. (A) is a figure which shows the time dependence of the voltage for trap level filling when the voltage for deflection | deviation operation is not applied, (b) is a voltage for trap level filling at the timing shown to (a). It is a figure which shows the time dependence of the deflection angle implement | achieved at the time of applying. (A) is a figure which shows the time dependence of the applied voltage at the time of applying the voltage for a deflection operation (when the voltage for a deflection operation is larger than the voltage for trap level filling), (b) These are figures which show the time dependence of the deflection angle implement | achieved when applying a voltage at the timing shown to (a). (A) is a figure which shows the time dependence of the applied voltage at the time of applying the voltage for a deflection operation (when the voltage for a deflection operation is smaller than the voltage for trap level filling), (b) These are figures which show the time dependence of the deflection angle implement | achieved when applying a voltage at the timing shown to (a). It is a figure for _{demonstrating} the case where the next trap level filling voltage is applied before T _detrap passes after _turning off the last trap level filling voltage according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical deflector 11 Electro-optic crystal 12 Positive electrode 13 Negative electrode 14 DC power supply 20 Control part 21 CPU
22 ROM
23 RAM
24 Input operation unit 25 Drive circuit

Claims (10)

An electro-optic crystal having an electro-optic effect, wherein a space charge is generated inside by applying a voltage, and a gradient of the magnitude of an electric field is generated; and
A first electrode disposed on a first surface of the electro-optic crystal;
An optical deflector control device for controlling an operation of an optical deflector comprising a second electrode disposed on a second surface facing the first surface of the electro-optic crystal,
First a first voltage application operation of which is applied between the first electrode and the second electrode a voltage, deflection angle time before SL when the first voltage applied for operation of the optical deflector Voltage application means for controlling a second voltage application operation in which a second voltage is applied between the first electrode and the second electrode so as to be constant with respect to the axis. Optical deflector control device. Timing acquisition means for acquiring the timing of applying the first voltage;
The optical deflector control device according to claim 1, wherein the second voltage application unit applies the second voltage before the timing acquired by the timing acquisition unit.   2. The second voltage application unit is configured to apply the current second voltage when a predetermined elapsed time has elapsed from the end of the previous application of the second voltage. The optical deflector control device described. The first voltage is equal to or higher than the second voltage;
During the operation of the optical deflector, a first voltage that is equal to or higher than the second voltage is always applied to the first electrode and the second electrode,
The second voltage applying unit applies the second voltage when a predetermined elapsed time has elapsed since the end of applying either the first voltage or the second voltage. The optical deflector control device according to claim 1.   2. The optical deflector control device according to claim 1, wherein the second voltage application unit performs control so as to continuously apply the second voltage applied first as a bias. 3. An electro-optic crystal having an electro-optic effect, wherein a space charge is generated inside by applying a voltage, and a gradient of the magnitude of an electric field is generated; and
A first electrode disposed on a first surface of the electro-optic crystal;
An optical deflector control method for controlling an operation of an optical deflector including a second electrode disposed on a second surface opposite to the first surface of the electro-optic crystal,
Applying a first voltage for operation of the optical deflector between the first electrode and the second electrode ; and
And a second voltage applying step of applying a second voltage between the first electrode and the second electrode so that a deflection angle is constant with respect to the time axis when the first voltage is applied. An optical deflector control method. A timing acquisition step of acquiring a timing of applying the first voltage;
The optical deflector control method according to claim 6, wherein the second voltage application step applies the second voltage before the timing acquired in the timing acquisition step.   7. The second voltage application step, when a predetermined elapsed time has elapsed since the end of the previous application of the second voltage, the application of the second voltage this time is performed. The optical deflector control method described. The first voltage is equal to or higher than the second voltage;
During the operation of the optical deflector, a first voltage that is equal to or higher than the second voltage is always applied to the first electrode and the second electrode,
In the second voltage application step, the second voltage is applied when a predetermined elapsed time has elapsed since the end of the application of either the first voltage or the second voltage. The optical deflector control method according to claim 6.   The optical deflector control method according to claim 6, wherein the second voltage applying step controls the second voltage applied first as a bias.

Images