JP2007240626A - Optical scanner driving method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner driving method which permits oscillation in the Y-direction while suppressing vibration in the X-direction, and to provide an optical scanner driving device using the optical scanner driving method. <P>SOLUTION: Upon the start-up mode, a driving signal of voltage applied between electrodes is applied while changing an oscillation width of a movable plate in the order from a driving signal in which the oscillation width is small, such as the driving signals D, C, B and, upon the stationary mode, the driving signal is switched to the driving signal A in which the maximum oscillation width is obtained. The oscillation in the direction orthogonal to the original oscillation direction decreases in the order of the driving signals D, C, B, A and, therefore, attraction problem between comb teeth does not occur in the stationary mode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrostatic drive type drive device that can be used in an optical apparatus such as a laser printer, a barcode reader, a display, etc., that swings a micromirror around a torsion bar axis and scans a light beam reflected on the mirror. .

  In conventional optical scanning devices, a polygon mirror is often used as an optical deflector that scans a light beam. The polygon mirror rotates at high speed and scans the light beam. However, in the image formation using the polygon mirror, it is necessary to rotate the polygon mirror at a higher speed in order to achieve a higher resolution image and a higher speed image formation. is there. However, in order to achieve high-speed rotation of the mirror, it is necessary to improve the durability of the bearing and take measures against heat generation and noise, and this problem must be solved. Therefore, there is a limit to high-speed scanning using a rotating body on which a mirror is formed. On the other hand, in recent years, an optical scanning device that scans a light beam has been proposed with a configuration that swings a micromirror using silicon micromachining technology. Such micromirror devices are roughly classified from their drive systems, and an electromagnetic drive system (see, for example, Patent Document 1) and an electrostatic drive system (see, for example, Patent Document 2) have been proposed.

  In the conventional proposal, the driving method using the magnetic field generating unit or the driving method using the electrostatic induction generating unit as the driving method of the movable part of the micromirror applies the driving voltage as a sinusoidal AC signal constantly. It is a driving method. As a typical example using electrostatic induction generating means, an optical scanning device that swings a mirror by electrostatic attraction can be shown (for example, see Patent Document 3). Two types of electrostatic drive methods are currently used. One is a method in which the drive electrode has a parallel plate electrode configuration, and the other has a comb-shaped electrode configuration (see, for example, Patent Document 4). The comb-shaped electrode method is generally said to be greatly superior to the parallel plate electrode method in terms of both fluctuation amount and driving force. FIG. 5 shows a comb-tooth component of a micromirror having a comb-shaped electrode structure (details will be described later). The comb-shaped fixed electrode and the movable electrode are arranged so as to face each other. The fixed electrode is fixed to the substrate and does not move, but the movable electrode forms a movable part together with the spring, and swings in the Y direction about the beam. Examples of means for increasing the electrostatic force in the swinging direction include increasing the voltage and increasing the comb tooth length.

JP 2002-78368 A JP-A-8-213320 Japanese Patent No. 30111144 Japanese Patent No. 3006178

By the way, it has been pointed out that the comb-teeth electrode system is attracted between adjacent comb teeth in the direction (X direction) orthogonal to the swing direction (Y direction) of the comb movable electrode. That is, the vibration is in the X direction shown in FIG. As the cause, ideally, if the movable side comb teeth are located at the center of the fixed comb teeth, the electrostatic forces in the left and right X directions are balanced, and the electrostatic resultant force becomes zero. However, actually, an electrostatic force in the X direction is generated due to a slight positional shift in the X direction. When this electrostatic force exceeds the reaction force of the spring in the X direction, the movable electrode is attracted to one of the fixed electrodes, causing a short circuit between the electrodes. In order to solve this problem, conventionally, it is important to set the relationship between the spring constant ky in the Y direction and the spring constant kx in the X direction to ky << kx, and the shape of the spring is optimized. Structural improvement measures have been reported. Further, according to experiments by the inventors, it has been found that when a rectangular voltage application signal is used as a drive signal, vibration in the X direction is likely to occur.
As a method for solving the above problem, in addition to the improvement of the conventional comb-tooth structure, a new type realized by appropriately controlling the generation, selection, and signal generation timing of the signal shape of the drive signal to which the voltage is applied. Make suggestions.

  According to the first aspect of the present invention, there is provided a flat plate-like movable member having a reflecting mirror at a portion including at least a central portion and having a supporting member capable of being twisted and displaced at both axial ends including the center of gravity. The movable member is provided so as to surround the movable member in a non-contact manner, and one surface is configured to be substantially flush with the reflection mirror surface of the drive member, and among the movable members, A movable electrode is provided near the end of the movable member in a direction perpendicular to the axial direction, a fixed electrode is provided near the fixed member end of the fixed member facing the vicinity of the movable member end, and a voltage is applied between the two electrodes. In a driving method for driving an optical scanner that is capable of swinging the movable member by an electrostatic force generated between both electrodes, a plurality of types of signal wave shapes are used as drive signals for voltages applied between the electrodes. Using the drive signal I am characterized in.

According to a second aspect of the present invention, in the optical scanner driving method according to the first aspect, the method of supplying the drive signal includes two drive modes of a start mode and a steady drive mode, and each drive mode includes the plurality of types. The signal waveform shape is selectively used.
According to a third aspect of the present invention, in the optical scanner driving method according to the second aspect of the invention, a rectangular wave-shaped drive signal is used in the steady drive mode, and a drive signal other than the rectangular wave shape is used in the startup mode. It is characterized by that.
According to a fourth aspect of the present invention, in the optical scanner driving method according to the second or third aspect, in the steady driving mode, a rectangular shape from which a resonance frequency component that resonates in a direction different from the swinging direction of the movable member is removed. A wave-shaped drive signal is used.

The invention according to claim 5 is an optical scanner driving device using the optical scanner driving method according to any one of claims 1 to 4, wherein a waveform generator capable of generating an arbitrary waveform shape, An optical scanner including a waveform selection unit that enables selection of an arbitrary waveform, a waveform shaping unit that removes an arbitrary frequency component from the waveform, and an oscillation frequency generation unit that can generate the waveform at an arbitrary frequency Features a drive device.
According to a sixth aspect of the present invention, in the optical scanner driving device according to the fifth aspect, the oscillation frequency generation unit includes a data storage means for storing digital data for determining the oscillation oscillation frequency and a value of the digital data. A programmable oscillator capable of generating a corresponding arbitrary frequency is provided.

According to a seventh aspect of the present invention, in the optical scanner driving device according to the fifth or sixth aspect, the waveform generation unit corresponds to a data storage means for storing digital data for determining a waveform shape and a value of the digital data. A programmable waveform generator capable of generating an arbitrary waveform shape is provided.
According to an eighth aspect of the present invention, in the optical scanner drive device according to any one of the fifth to seventh aspects, the waveform selection unit includes data storage means for storing digital data for determining selection of a waveform shape. And a programmable waveform selector capable of selecting an arbitrary waveform corresponding to the value of the digital data.

According to a ninth aspect of the present invention, in the optical scanner driving device according to any one of the fifth to eighth aspects, the waveform shaping section stores digital data for determining a frequency for shaping the waveform and a shaping width. And a programmable waveform shaper that enables arbitrary waveform shaping corresponding to the value of the digital data.
According to a tenth aspect of the present invention, in the optical scanner driving device according to any one of the sixth to ninth aspects, a microprocessor system for performing the data storage and other control is provided. To do.

  According to the optical scanner driving method and the optical scanner driving device of the present invention, it is possible to swing in the Y direction while suppressing vibration in the X direction.

FIG. 13 shows a conventional oscillating mirror.
In the figure, reference numeral 101 denotes a support substrate, 102 denotes a mirror, 103 denotes a torsion bar, 104 denotes an electrode pad, 105 denotes a mirror electrode, 106 denotes an insulator, 107 denotes a fixed electrode, and 108 denotes a fixed electrode pad.
The operation of the conventional oscillating mirror will be described with reference to FIG.
A mirror 102 is disposed in a recess provided in a support substrate 101 as a fixing member, and the mirror 102 is supported by the support substrate 101 via a torsion bar 103 as a support member provided integrally. Both sides of the mirror 102 can be swung in the direction perpendicular to the plane of the mirror by the twisting action of the torsion bar 103. The torsion bar 103 is made of a conductive member, and both ends thereof are electrically connected to the pads 104 provided on the support substrate 101.

  Fixed electrodes 107 are supported on both sides of the concave portion of the support substrate 101 via insulators 106. The fixed electrode 107 is disposed with a small interval so that the fixed electrode 107 is in contact with the mirror electrode portions 105 on both sides of the mirror 102 so that they do not come into contact with each other due to vibration or swinging. It arrange | positions in a position higher along a rocking | swiveling direction than an initial position. That is, the mirror electrode portion and the fixed electrode portion 107 are arranged with a height difference at the initial position of the mirror electrode portion 105. This optical scanning device applies a high voltage between the pad 108 of one fixed electrode 107 and the pad 104 to which the torsion bar 103 is connected, and generates an electrostatic force between the fixed electrode 107 and the mirror electrode unit 105. The one side surface of the mirror 102 is attracted to the fixed electrode 107 side by the electrostatic attraction, and the mirror 102 is swung in the direction perpendicular to the plane of the mirror while twisting and deforming the torsion bar 103 by this attraction operation. Let When the voltage application to the fixed electrode 107 is released immediately after the swinging operation, the mirror is swung in the reverse direction by the torsional restoring force of the torsion bar 103. By repeating this voltage application and stop, the mirror 102 can be swung, and light from a light source (not shown) is reflected by the mirror 102, so that the light can be deflected and scanned.

FIG. 1 is a view showing an optical deflector having a parallel plate electrode configuration according to the present invention.
FIG. 2 is a diagram showing an optical deflector having a comb-shaped electrode configuration according to the present invention. FIG. 4A shows an initial state, and FIG. 4B shows a swinging state.
In both figures, reference numeral 1 denotes a support substrate as a fixed member, 2 denotes an elastic support portion, 3 denotes a fixed electrode, 4 denotes a movable electrode, 5 denotes a reflecting mirror surface, and 7 denotes a flat movable plate.
A central portion of a pair of opposing side edges of the movable plate 7 is supported on a support substrate 1 made of silicon by an elastic support portion 2 (hereinafter referred to as a beam for convenience of explanation), and at least near the central portion of the movable plate 7. Is a reflecting mirror surface 5 that acts as a reflecting mirror. The two beams 2 can be twisted and displaced so as to be a single axis passing through the center of gravity of the movable plate 7.
The movable electrode 4 is provided in the vicinity of the end surface of the movable plate 7 that is orthogonal to the support direction, and the fixed electrode 3 is provided at a position that is substantially in the same plane on the side of the fixed member facing the movable electrode 4. The fixed member is configured to surround the movable member 7 at least in a range where they do not come into contact with each other even by vibration or swing. For example, a gap of 5 μm is provided between the movable electrode 4 and the fixed electrode 3.
For example, when another electrode (not shown) is provided on the back surface of the movable plate 7 and a voltage is applied between the movable plate 7 and the fixed electrode, the movable plate 7 starts to oscillate due to the force with which both electrodes attract each other. Or you may start rocking | fluctuation by applying an external force. A weak air pressure is sufficient as the external force. Any other known method can be used.
When the oscillation starts, an electrostatic attractive force acts between the electrodes by applying a voltage between the electrodes at a predetermined timing, and the end surface of the movable plate 7 is attracted to the fixed electrode 3. The operation of the optical deflector configured as described above will be described with reference to FIG.

FIG. 3 is a diagram for explaining the operation of the optical deflector of the present invention. FIG. 4A is a diagram showing the vicinity of the maximum position of counterclockwise shake. FIG. 4B is a diagram showing a state where the neutral position (initial position) is passed while rotating clockwise, and FIG. 4C is a diagram showing the vicinity of the maximum position of clockwise deflection.
In the figure, the movable electrode 4 attached to the movable plate 7 is drawn out to the silicon substrate 1 and grounded through a pad (not shown). When the positional relationship between the fixed electrode 3 and the movable electrode 4 is in the state shown in FIG. 5A, when a voltage of 30 V, for example, is applied to the fixed electrode 3, the electrostatic force acting between the fixed electrode 3 and the movable electrode 4 and the beam 2 are applied. Due to the torsional rigidity, the movable plate 7 is given a force that swings clockwise in the drawing. If the voltage application to the fixed electrode 3 is turned OFF when the movable plate 7 reaches the neutral position, the movable plate 7 is further swung in the clockwise direction by the moment of inertia as shown in FIG. Finally, as shown in FIG. 5C, the armature swings to a position where the moment of inertia and the torsional rigidity of the beam 2 are balanced. When it reaches the maximum deflection angle, it pauses and starts swinging in the opposite direction. In the figure, it starts to swing counterclockwise. When a voltage is applied again to the fixed electrode 3 at an appropriate time after starting to swing counterclockwise, the movable plate 7 rotates counterclockwise in the figure due to the electrostatic force acting between the fixed electrode 3 and the movable electrode 4 and the torsional rigidity of the beam 2. Swing to. When the voltage application to the fixed electrode 3 is turned off when the movable plate 7 reaches the horizontal position again, the movable plate 7 further swings counterclockwise due to the moment of inertia. Finally, as shown in FIG. 5A, the armature swings to a position where the moment of inertia and the torsional rigidity of the beam 2 are balanced. By adjusting the voltage application frequency to the fixed electrode 3 to the resonance frequency of the movable plate 7, the movable plate 7 can be swung with a large deflection angle.

FIG. 4 is a diagram showing a movable plate swing locus and voltage application timing.
In the figure, examples of drive signals A to D are shown. The waveform shape of the drive signal A is a rectangular wave, the waveform shape of the drive signal B is a triangular wave, the waveform shape of the drive signal C is a trapezoidal wave, and the waveform shape of the drive signal D is a sine wave. It has been experimentally found that the waveform shape of the drive signal affects the swing amplitude of the movable plate 7. It was found that the swing width is between θH and θL of the movable plate swing waveform shown in the figure, and the swing width becomes smaller in the order of the drive waveforms A → D in the figure.
The drive signal PW shown in the figure is one type of rectangular wave, but a rectangular pulse with a short time width and a rectangular pulse with a slightly long time width are arranged close to each other. The overall time width is approximately the same as the time width of the rectangular waveform pulse of the drive signal A. It has been found that when such a waveform is applied in the steady drive mode, the resonance frequency component in the X direction becomes extremely small. A method for generating the drive signal PW will be described later.

As shown in the figure, the voltage may be applied for an arbitrary time t in the direction of swinging toward the swing angle 0 from the point before the maximum swing angle as the phase α of the voltage application timing from the time when the swing angle is maximum. In FIG. 2, the end of the movable member 7 not supported by the beam 2 has a comb-like shape, and a movable electrode is formed in accordance with the shape, and the movable member 7 is provided at a corresponding position on the fixed member side. It is opposed to a comb-shaped driving fixed electrode with a small gap therebetween.
The stationary electrode 3 and the movable electrode 4 that are opposed to each other in a stationary state have a length along the edge when viewed at the facing portion, and a thickness when viewed microscopically, so that extremely elongated surfaces face each other. You can see that. Since the opposing surface plays a leading role in the electrostatic attraction, the opposing electrode area can be increased in the length direction by making the electrodes comb-like in this way. Accordingly, the driving torque can be further increased, and the deflection angle of the movable plate 7 can be further increased. When a light beam is applied to the reflecting mirror surface 5 of the swinging movable plate 7, incident light can be deflected by the reflecting mirror surface 5 due to the swinging of the movable plate 7.

FIG. 5 is a partially enlarged view of a comb-tooth component of a micromirror having a comb-shaped electrode structure.
In the figure, symbol a is a torsion beam width, b is a torsion beam height, c is a movable plate thickness, d is a movable plate width, e is a movable plate length, m is a comb tooth beam height, and n is a comb tooth. The partial beam width, lx is the comb tooth beam length, Ly is the torsion beam length, X is the arrangement direction of the comb teeth, and Y is the rotation direction of the movable plate.
In the figure, the support member 2 has a torsion beam structure. The movable plate 7 supported by the support member 2 can rotate and swing around the support member 2. The oscillation frequency fy of the movable plate 7 is approximated by the following expression.
fy = 1 / 2π√ (Ky / Iy)
fy: resonance frequency of the movable plate 7,
Iy: moment of inertia,
Ky: Spring constant
The spring constant Ky is the beam width a, beam height b and beam length Ly of the torsion beam.
Is given by:
Ky = (Jp × G) / Ly,
Jp = 0.141 × a × b ³ ,
G = Ey / (2 (1 + ι)),
Ey: Young's modulus
ι: Poisson's ratio
The inertia moment Iy is defined as the lateral width d, length e, and thickness c of the movable plate 7.
It is given by
Iy = My × (e ² + c ² ) / 12
My = ρ (d × e × c)
ρ is the material density. From the above equation, the resonance frequency fy is determined by the shapes of the support member 2 and the movable plate 7.

The comb tooth portion of the movable electrode 4 has a cantilever structure, and the natural frequency fx in the X direction is approximated by the following equation.
fx = 1 / 2π√ (Kx / Ix),
fx: natural frequency of the movable electrode 4,
Ix: moment of inertia,
Kx: Spring constant
The spring constant Kx is the beam width n, beam height m, and beam length lx of the comb tooth portion.
And given by:
Kx = (3Ex × Jx) / lx ³ ,
Jx = (m × n ³ ) / 12
Ex: Young's modulus
The moment of inertia Ix is
Ix = Mx × (lx ² + n ² ) / 12
Mx = ρ (lx × m × n)
From the above formula, the natural frequency fx of the comb teeth is determined by the shape of the movable electrode 4. The natural frequency fx of the comb teeth of the movable electrode 4 has a relationship of fx >> fy with respect to the resonance frequency fy of the movable plate 7, and fx is 4 to 20 times fy.

FIG. 6 is a diagram for explaining a method of generating the drive waveform PW.
The oscillation amplitude θL-θH by driving using the driving waveform A is increased as compared with using other driving waveforms. However, in this case, the influence on the X-direction vibration is also increased. The factor of this influence is a harmonic component contained in the drive waveform A, which is a frequency band approximate to the comb natural frequency fx. fx is 4 to 20 times as large as fy. In particular, fx = fy × 2 and fx = fy × 3 are the second harmonic and the third harmonic and greatly affect the vibration in the X direction. Therefore, the vibration in the X direction can be reduced by removing the second harmonic and the third harmonic components from the drive waveform A. As shown in the figure, the drive waveform PW can be generated by applying a filter for removing the second harmonic and the third harmonic to the drive waveform A.
In this way, by using the rectangular wave shape drive signal of the drive signal PW in which the resonance frequency component that resonates and vibrates in a direction different from the swing of the movable member is used for the rectangular wave shape of the applied signal during steady driving, This has the effect of further suppressing vibrations in the X direction during steady driving.

FIG. 7 is a conceptual diagram in which a drive signal is applied between the fixed electrode 3 and the movable member disposing electrode 4.
In the figure, reference numeral 10 denotes a drive signal.
FIG. 8 is a diagram showing a case where the maximum deflection width at the end of the movable plate is within the thickness range on the fixed electrode side. FIGS. 3A, 3B and 3C are the same as FIGS. 3A, 3B and 3C.
FIG. 9 is a diagram showing a case where the maximum deflection width of the movable plate end exceeds the thickness range on the fixed electrode side. FIGS. 3A, 3B, and 3C are the same as FIGS. 3A, 3B, and 3C.
The waveform shape of the drive signal 10 is shown in FIG. It has been experimentally found that the vibration in the X direction of the comb electrode when each waveform shape is used is affected by the waveform shape of the drive signal. The vibration in the X direction decreases in the order of drive waveforms A → D. The vibration in the X direction is generated when the swing amplitude in the Y direction is within the thickness range of the fixed electrode, that is, when the swing width is as shown in FIG. When the swing width in the Y direction maintains the swing amplitude exceeding the range of the thickness of the fixed electrode, that is, in the swing width shown in FIG. 9, the vibration in the X direction decreases. From the above three points, it is considered that the above problem can be reduced by applying a drive signal waveform shape corresponding to the swinging width of the movable plate 7.

FIG. 10 is a diagram showing the swing characteristics of the movable plate swing angle and drive signal application frequency according to the present invention.
In the figure, reference numeral fc represents a resonance frequency, fd represents a steady drive frequency, fs represents a start start frequency, and θd represents a steady deflection angle.
The swing angle becomes maximum at the resonance frequency fc of the movable plate 7, and the swing angle becomes smaller as the drive signal application frequency increases. In the figure, when the optical scanner of the present invention is used while being swung at the steady drive frequency fd, the start frequency fs is first given without first applying the drive signal of the steady drive frequency fd at the time of start. In this method, the application frequency is gradually reduced over the application period Ts to bring it closer to the steady drive frequency fd. This way of giving a signal is called a startup mode. On the other hand, how to give a drive frequency in a steady state is called a steady drive mode, and both modes are collectively called a drive mode. When the drive frequency is varied from fs to fd in the initial frequency application period Ts, the waveform shape of the drive signal corresponding to the swing width of the movable plate 7 is selected and used.
As described above, the present invention proposes an optical scanner driving method in which a driving mode can be configured in a plurality of operation modes of a start mode and a steady driving mode, and the plurality of types of signal waveform shapes are selectively used in each operation mode. .

FIG. 11 is a schematic diagram for explaining the relationship between the type of drive signal and the swing width.
When the optical scanner is swung at the steady drive frequency fd, at the time of start-up, the drive signal of the target steady drive frequency fd is not directly applied, but the start frequency fs is given first, and the applied frequency is gradually applied in the initial drive frequency application period Ts. Is changed to approach the steady drive frequency fd. In this way, by setting the frequency fs away from the steady drive frequency fd as the starting frequency, the oscillation due to the rapid oscillation amplitude at the start-up of the optical scanner is started by starting the oscillation amplitude at the start-up from a small amplitude. Etc. can be avoided. A small oscillating width is obtained at the start, and then the oscillating amplitude of the optical scanner is gradually increased by changing the driving frequency so as to approach the resonance frequency of the optical scanner, and the oscillating amplitude is predetermined at the steady driving frequency fd. Can be obtained. The function of making the drive frequency arbitrarily variable will be described later.

In FIG. 6A, the swing width Y is very small, and vibration in the X direction is likely to occur within this range. In this section, a drive signal having a sine wave shape of the drive signal D is applied. In the oscillation width of FIG. 5B, a triangular signal of the drive signal C is applied. The trapezoidal wave of the drive signal B is applied in the oscillation width of FIG. 10C, and the signal shape driven at the steady drive frequency fd of FIG. Thus, the present invention uses a waveform shape different from the rectangular shape as the drive signal in the start-up mode, and uses a rectangular-wave shape drive signal in the steady drive mode.
The drive frequency is varied from the starting time to the steady drive frequency fd. At this time, it is necessary to increase the swing amplitude in the Y direction so as to reduce the vibration in the X direction. As a countermeasure, a method is proposed in which the drive signal waveform is arbitrarily changed in the process of changing the drive frequency to the steady drive frequency fd.
In the swing amplitude in the Y direction at the position of FIG. 8, the rate of occurrence of defects due to the vibration in the X direction is high, so the drive signal D is used in this range. In the position shown in FIG. 9, the swing amplitude in the Y direction becomes large, and when the comb teeth pass the range shown in FIG. 8, a sufficient speed is obtained, and the influence in the X direction is reduced. At this time, driving with the driving signal A enables more efficient driving than the driving signal D. Further, the drive signal PW can be used to reduce the influence of the resonance frequency such as the second harmonic and the third harmonic on the drive signal A. The function of making the drive signal waveform arbitrarily variable will be described later.

FIG. 12 is a block diagram showing an optical scanner driving apparatus for realizing the optical scanner driving method of the present invention.
In the figure, reference numeral 36 denotes a waveform generation unit, 39 denotes a waveform shaping unit, 42 denotes an oscillation frequency generation unit, and 50 denotes a waveform selection unit.
The optical scanner driving apparatus includes a waveform generation unit 36 that can generate an arbitrary waveform shape, a waveform selection unit 50 that can select an arbitrary waveform, a waveform shaping unit 39 that removes an arbitrary frequency component from the waveform, The oscillation frequency generator 42 is configured to generate the waveform at an arbitrary frequency. The waveform generation unit 36 can generate a waveform shape that can reduce vibration in the X direction, and the waveform generation unit 36 can selectively reduce the vibration in the X direction when the drive signal waveform at the start of optical scanner driving is selectively and timely. In the oscillation frequency generation unit 42, the frequency of the drive signal at the start of the optical scanner drive can be changed stepwise from a frequency with a small oscillation width to the steady drive frequency fd, and the operation at the initial startup can be performed smoothly. Further, the waveform shaping unit 39 can remove an unnecessary frequency component having a rectangular wave shape used during steady driving.

The waveform generator 36 has a function of making the drive signal waveform arbitrarily variable. The waveform generation unit 36 stores digital data (for example, numerical values 1 to 5 corresponding to A to D and PW) for determining the waveform shape of the drive signals A to D and PW. Data storage means. A programmable waveform generator is also provided so that a predetermined waveform shape associated in advance can be generated according to the value of the called digital data as required.
By using digital data, any data value can be easily changed and corrected, and the variable speed or variable step amount of the digital data can be easily programmed by software.

The switching timing of the driving waveform is determined based on the correlation between the driving signal application timing and the driving frequency value. An appropriate switching timing value obtained from an experiment or the like is stored in the data storage unit in advance, and switching is performed in a timely manner according to a command from the processing program.
The waveform selector 50 has a function of arbitrarily switching the drive signal waveform. The waveform selection unit 50 includes digital data storage means for storing waveform switching value data and a programmable waveform selector for generating arbitrary switching timing from the digital data.
By using digital data, any data value can be easily changed and corrected, and the variable speed or variable step amount of the digital data can be easily programmed by software.

In FIG. 4, the drive waveforms A to D and PW are shown as independent waveforms, but a method that enables the waveform shape to be changed more continuously is used. That is, when switching from the drive waveform D to the drive waveform A, the drive waveform D is not changed suddenly from the drive waveform D to the drive waveform A, but is changed to the drive waveform A while continuously deforming the drive waveform D.
By doing so, it is possible to reduce the influence of fluctuations in the swing trajectory in the Y direction accompanying the change of the drive waveform.
The waveform shaping unit 39 has a function of making the waveform shaping arbitrarily variable. The waveform shaping unit 39 has data storage means for storing digital data for determining a frequency to be subjected to waveform shaping and a shaping width. It also has a programmable waveform shaper so that the waveform shape used as the drive signal can be shaped according to the frequency and shaping width associated in advance according to the value of the digital data called as necessary. ing.
By using digital data, any data value can be easily changed and corrected, and the shaping speed or shaping step amount of the digital data can be easily programmed by software.

The oscillation frequency generation unit 42 has a function of making the drive frequency arbitrarily variable.
The oscillation frequency generation unit 42 has data storage means for storing digital data so that the oscillation frequency necessary for optical scanning can be obtained. When a desired oscillation frequency is determined by appropriate conditions, a programmable oscillator is also provided so as to call digital data corresponding to the frequency and generate a frequency corresponding to the digital data. The digital data to be stored may be the frequency value itself, but if a method of selecting a plurality of discrete frequencies in advance and selecting one of them is described in the section of drive signal selection It is also possible to use a simple number such as the number of options.
By using digital data, any data value can be easily changed and corrected, and the variable speed or variable step amount of the digital data can be easily programmed by software.

It is a figure which shows the optical deflector of the parallel plate electrode structure of this invention. It is a figure which shows the optical deflector of the comb-tooth type electrode structure of this invention. It is a figure for demonstrating operation | movement of the optical deflector of this invention. It is a figure which shows a movable plate rocking locus and a voltage application timing. It is a partial enlarged view of the comb-tooth structure part of the micromirror which has a comb-tooth-shaped electrode structure. It is a figure for demonstrating the method of producing | generating the drive waveform PW. FIG. 3 is a conceptual diagram in which a drive signal is applied between a fixed electrode 3 and a movable member disposing electrode 4. It is a figure which shows the case where the maximum deflection width of a movable plate edge part exists in the range of the thickness by the side of a fixed electrode. It is a figure which shows the case where the maximum deflection width of a movable plate edge part exceeds the range of the thickness by the side of a fixed electrode. It is a figure which shows the rocking | fluctuation characteristic of the movable plate deflection angle of this invention, and a drive signal application frequency. It is a schematic diagram explaining the relationship between the kind of drive signal, and a rocking | fluctuation width. It is a block diagram which shows the optical scanner drive device which implement | achieves the optical scanner drive method of this invention. It is a figure which shows the conventional rocking | fluctuation type mirror.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support substrate 2 Elastic support part 3 Fixed electrode 4 Movable electrode 5 Reflecting mirror surface 7 Movable plate

Claims (10)

  A flat plate-like movable member having a reflection mirror in at least a portion including the central portion and having a support member that can be twisted and displaced at both ends in the axial direction including the center of gravity, and connected to the support member, the periphery of the movable member And a fixed member configured so that one surface is substantially flush with the reflecting mirror surface of the drive member, and the movable member has a direction perpendicular to the axial direction. A movable electrode is provided in the vicinity of the movable member end, a fixed electrode is provided in the vicinity of the fixed member end of the fixed member facing the vicinity of the movable member end, and a voltage is applied between the two electrodes to generate between the two electrodes. In a driving method for driving an optical scanner that can swing the movable member by an electrostatic force, a plurality of types of signal waveform driving signals are used as a driving signal for a voltage applied between the electrodes. Light scan Driving method.   2. The optical scanner driving method according to claim 1, wherein the driving signal is provided by two driving modes of a start mode and a steady driving mode, and each driving mode selectively uses the plurality of types of signal waveform shapes. An optical scanner driving method.   3. The optical scanner driving method according to claim 2, wherein a driving signal having a rectangular wave shape is used in the steady driving mode, and a driving signal having a non-rectangular wave shape is used in the starting mode. .   4. The optical scanner driving method according to claim 2, wherein, in the steady driving mode, a rectangular waveform driving signal from which a resonance frequency component that resonates in a direction different from the swinging direction of the movable member is removed is used. An optical scanner driving method.   5. An optical scanner driving apparatus using the optical scanner driving method according to claim 1, wherein a waveform generation unit capable of generating an arbitrary waveform shape and a waveform selection capable of selecting an arbitrary waveform are provided. An optical scanner drive device comprising: a waveform shaping unit that removes an arbitrary frequency component from the waveform; and an oscillation frequency generation unit that can generate the waveform at an arbitrary frequency.   6. The optical scanner drive device according to claim 5, wherein the oscillation frequency generation unit is capable of generating an arbitrary frequency corresponding to a value of the digital data and a data storage means for storing digital data for determining the oscillation oscillation frequency. An optical scanner driving device comprising: a programmable oscillator for performing the above-described operation.   7. The optical scanner driving apparatus according to claim 5, wherein the waveform generation unit is capable of generating an arbitrary waveform shape corresponding to a value of the digital data and data storage means for storing digital data for determining the waveform shape. An optical scanner driving device comprising a programmable waveform generator.   8. The optical scanner driving device according to claim 5, wherein the waveform selection unit includes data storage means for storing digital data for determining selection of a waveform shape, and an arbitrary value corresponding to the value of the digital data. An optical scanner driving device comprising: a programmable waveform selector capable of selecting a waveform.   9. The optical scanner driving device according to claim 5, wherein the waveform shaping unit includes a data storage unit that stores digital data for determining a frequency for performing waveform shaping and a shaping width, and a digital data An optical scanner driving device comprising: a programmable waveform shaper that enables arbitrary waveform shaping corresponding to a value.   10. The optical scanner driving device according to claim 6, further comprising a microprocessor system for performing the data storage and other control.

Images