JP2005309414A - Method of driving optical modulation element array, optical modulation element array and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of driving optical modulation element array, an optical modulation element array and an image forming apparatus, in which an address voltage is written without causing an erroneous operation even in a period of vibration suppression and a driving cycle is shortened. <P>SOLUTION: In the method of driving the optical modulation element array 100, a movable part provided with a movable electrode and a fixed electrode facing to the movable part are provided, the movable part is moved by electrostatic force, optical modulation elements which modulate light made incident to the movable part are arranged one-dimensionally or two-dimensionally, each optical modulation element has a driving circuit including a memory circuit, one of the electrodes is an electrode to write an element displacement signal from the driving circuit and the other is an electrode which applies a control voltage Vb, either of the electrodes receives the displacement signal from the driving circuit, the applied voltage on either of the two electrodes is controlled during the time from the arrival of the movable part to the final moving position to the output of a next moving signal by the driving circuit to either of the electrodes, thus the movable part is fixed at the final moving destination. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for driving a light modulation element array, a light modulation element array, and an image forming apparatus that modulate incident light by displacing a movable part of a light modulation part, and in particular, an improvement that enables high-speed writing of next data. Regarding technology.

  In recent years, a digital micromirror device (DMD) that produces a micromirror based on micromechanical technology and tilts the micromirror to deflect light is attracting attention as one of the spatial light modulators (SLMs). Yes. This DMD has many uses in the field of optical information processing, such as projection displays, video monitors, graphic monitors, televisions and electrophotographic prints. As for the technology relating to DMD, the following patent documents 1, 2, 3 and the like have been filed by the applicant, Texas Instruments Incorporated.

  In the DMD, a plurality of micromirrors of about 16 μm × 16 μm are provided at a pitch of 17 μm on a CMOS SRAM formed on a silicon substrate, and each micromirror corresponds to a screen pixel. FIG. 14 is an exploded perspective view showing one light modulation element (pixel) 1 of the light modulation element array. Reference numeral 3 denotes a micromirror, which is connected to a support post connecting portion 9 of a yoke 7 by a micromirror support post 5. The yoke 7 is held by a hinge 11. The hinge 11 is held by the post cap 13. The post cap 13 is connected to a hinge support post connecting portion 19 of the control bus 17 by a hinge support post 15. That is, the micromirror 3 is connected to the control bus 17 via the hinge 11, the post cap 13, and the hinge support post 15. A control voltage is supplied to the micromirror 3 via the control bus 17. The control bus 17 has a landing site 21. The landing site 21 has insulation or is kept at the same potential as the micromirror 3.

  Reference numeral 23a denotes one fixed electrode (first address electrode), and reference numeral 23b denotes the other fixed electrode (second address electrode). The first address electrode 23 a is connected to the electrode support post connection portion 29 of the first address electrode pad 27 a by the electrode support post 25. The second address electrode 23b is also connected to the electrode support post connecting portion 29 of the second address electrode pad 27b by the electrode support post 25.

  A digital signal input from the first connection portion 31a to the first address electrode pad 27a is input to the first address electrode 23a. A digital signal input from the second connection portion 31b to the second address electrode pad 27b is input to the second address electrode 23b. When a digital signal is input to the first address electrode 23a and the second address electrode 23b, the micromirror 3 is tilted, and white display or black display is selected. A part of the yoke piece 33 may contact the landing site 21 by tilting the micromirror 3.

Next, a driving sequence of the light modulation element configured as described above will be described.
FIG. 15 is a cross-sectional view schematically showing the light modulation element shown in FIG. 14, and FIG. 16 is an explanatory diagram of a drive sequence of the light modulation element shown in FIG.
In the initial state of the light modulation element 1, for example, the micromirror 3 is inclined to the left (left side in FIG. 15). At this time, as shown in FIG. 16, a constant control voltage Vb is applied to the control bus 17 (A). On the other hand, the address voltage Va1 applied to the first address electrode 23a is set smaller than the address voltage Va2 applied to the second address electrode 23b (Va1 <Va2). Therefore, the potential difference (| Vb−Va1 |) on the left side of the micromirror 3 becomes larger than the potential difference (| Vb−Va2 |) on the right side, and the micromirror 3 is tilted to the left side by electrostatic force.

  In the driving sequence in which, for example, the micromirror 3 is shifted to the right inclination from this state, first, the voltage applied to the first address electrode 23a and the second address electrode 23b is inverted (Va1> Va2). Thus, even if the address electrode is inverted, the micromirror 3 still maintains the left inclination. This is because the right end of the micromirror 3 and the second address electrode 23b are sufficiently separated from each other, so that an electrostatic force sufficient to cause the inclination does not act. This action realizes a so-called latch function that enables the next writing Tw shown in FIG. 16 to be efficiently held while being tilted (displayed).

  Next, as shown in FIG. 16, the address voltage to the first address electrode 23a and the second address electrode 23b remains unchanged, and only the control voltage Vb is lowered (b). Then, the electrostatic force on the left side of the micromirror 3 is substantially lost, and a slight electrostatic force is activated on the right side, and the elastic restoring force of the hinge 11 is added to the left side of the micromirror 3 so that the left side of the micromirror 3 is lifted. Will be released.

  Next, when the control voltage Vb is returned to the original constant value (c), the electrostatic force on the right side of the micromirror 3 acts strongly, and the micromirror 3 transitions to the right inclination. When the micromirror 3 transitions to the right inclination, the distance from the second address electrode 23b is shortened, so that the electrostatic force increases synergistically, and this time the right side is held in the landing site 21. From the decrease in the control voltage Vb to the landing on the right side of the micromirror 3 is the switch time Tr shown in FIG.

  Here, immediately after the right side of the micromirror 3 has landed, vibration is generated by receiving a reaction force from the landing site 21. Therefore, the next writing is performed after the elapse of the switch time Tr and after waiting for the vibration calming time Ts. The time (Td = Tr + Ts) from the decrease of the control voltage Vb until the next writing (d) becomes possible is a specific time dependent on the light modulation element 1. In FIG. 16, Tb indicates the time when the previous writing ends and the next writing starts. Therefore, in the conventional method of driving the light modulation element array, as shown in FIG. 17, the total time (drive cycle) Tc = Tw + Tb of the writing time Tw and the time Tb when the previous writing ends and the next writing starts is By being repeated, writing for one block (one row) BL [1] is performed, and this is performed for a plurality of predetermined (M) blocks (for a plurality of rows) BL [M], so that all pixel display is performed. It was done.

JP-A-6-124341 JP-A-8-334709 JP-A-9-238106

When the light modulation element 1 described above is used to perform photosensitive material exposure at a high speed or when a projector having a higher number of pixels is to be displayed, it is necessary to increase the driving cycle Tc. Here, in order to speed up the drive cycle Tc, it is conceivable to shorten Tw (writing time) and Tb (time when the previous writing ends and the next writing starts). For shortening Tw, reduction of the total number of pixels or speeding up of the writing clock frequency is an effective means from the relationship of Tw = (total number of pixels) / (writing clock frequency). On the other hand, the latter depends on the clock device development technology. On the other hand, shortening of Tb can be achieved by performing writing during Ts (vibration soothing time) as shown in FIG. 18 (see the broken line portion of displacement in FIG. 18).
However, if writing is performed during the vibration calming time Ts (the address voltage is reversed), there is a risk of malfunction depending on the vibration state. FIG. 19 is an explanatory diagram showing (1) a case where normal operation is performed when writing is executed during the vibration soothing time, and (2) a case where malfunction occurs. That is, as shown in FIG. 19 (1), when the right side of the micromirror 3 is in contact even during the vibration sedation time, the interelectrode voltage ΔV1 = FIG. 19 (1) -A) Even if the address voltage is inverted so that the interelectrode voltage ΔV1 = 20v and ΔV2 = 15v in FIG. 19 (1) -B) from 15v, ΔV2 = 20v, the micromirror 3 remains right-tilted. On the other hand, as shown in FIG. 19 (2), if the right side of the micromirror 3 is slightly separated from the landing site 21 due to vibration even during the vibration calming time, FIG. 19 (2) -A) When the address voltage is inverted so that the inter-electrode voltages ΔV1 = 15v and ΔV2 = 20v of FIG. 19 (2) -B), the inter-electrode voltages ΔV1 = 15v and ΔV2 = 20v. The electrostatic force on the right side is reduced by the amount of floating, and the electrostatic force on the right side loses the electrostatic force on the left side when the address voltage is reversed. As a result, the micromirror 3 that must be held at the right side is left. Inclined malfunction.
SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and provides a method of driving an optical modulation element array, an optical modulation element array, and image formation that can write an address voltage without causing a malfunction even during a vibration sedation time. An object of the present invention is to provide a device and to shorten the driving cycle.

  According to the first aspect of the present invention for achieving the above object, there is provided a method of driving a light modulation element array according to the present invention, comprising: a movable part supported so as to be elastically displaceable and having a movable electrode at least partially; Static electricity generated by applying a voltage between the movable electrode and the first and second fixed electrodes. The first and second fixed electrodes displace the movable portion in different directions. The movable portion is displaced by force, and micro electro mechanical light modulation elements that modulate light incident on the movable portion are arranged one-dimensionally or two-dimensionally, and each of the light modulation elements includes a memory circuit. A light modulation element array having a drive circuit that includes one of the movable electrode and the fixed electrode that writes an element displacement signal from the drive circuit, and the other electrode that applies a control voltage. In the way Then, any one of the electrodes receives a displacement signal from the drive circuit, and the drive circuit outputs the next displacement signal to any one of the electrodes after the movable part reaches the final movement destination. In the meantime, the voltage applied to any one of the electrodes is controlled to localize the movable part to the final destination.

  In this method of driving the light modulation element array, the voltage applied to any of the electrodes is applied after the movable part reaches the final movement destination until the drive circuit outputs the next displacement signal to any of the electrodes. Control. This generates a greater vibration-suppressing electrostatic force than before, and even during the vibration suppression time immediately after the movable part reaches the final destination, the movable part is forcibly controlled by the large electrostatic force and can be latched. Become. Therefore, the structure remains the same, and there is no need to wait for the vibration to subside as in the past even during the vibration suppression period (in other words, the data write timing can be shifted a little earlier). And the address voltage can be written without causing a malfunction. Note that if the control voltage is increased before the movable part reaches the final destination, the movable part is accelerated and brought into contact, and vibration is increased.

  The method of driving the light modulation element array according to claim 2, wherein the drive circuit outputs the next displacement signal to any one of the electrodes after the movable part reaches the final movement destination. An inter-electrode voltage between the fixed electrode and the movable electrode arranged on the final movement destination side of the movable part is increased.

  In this light modulation element array driving method, the fixed part arranged on the final movement destination side of the movable part after the movable part reaches the final movement destination and before the drive circuit outputs the next displacement signal to the electrode. By increasing the inter-electrode voltage between the electrode and the movable electrode, a vibration-suppressing electrostatic force is applied to the movable part at the final movement destination, thereby forcibly damping the movable part.

  4. The method of driving an optical modulation element array according to claim 3, wherein the drive circuit is a period from when the movable part reaches the final movement destination until the drive circuit outputs a next displacement signal to the one electrode. The voltage from is reduced.

  In this method of driving the light modulation element array, the voltage from the drive circuit is decreased by the time the movable unit reaches the final movement destination and before the drive circuit outputs the next displacement signal to the electrode. The change in the voltage between the electrodes at the time of voltage reversal becomes small, and the risk of malfunctioning can be reduced.

  The light modulation element array driving method according to claim 4, wherein the light modulation element supports the movable part in a swingable manner, and the first and second fixed electrodes are on the same side with respect to the movable part. It is characterized in that, by individually applying a driving voltage to the first and second fixed electrodes, the movable part is inclined in different directions to perform light modulation.

In the method of driving the light modulation element array, the first and second fixed electrodes are arranged on the same side of the movable part with respect to the movable part supported so as to be swingable. By individually applying a driving voltage to the two fixed electrodes, the movable part can be tilted in different directions, whereby light modulation can be performed.
In addition to the above-described configuration, the light modulation element has a movable portion disposed between the first fixed electrode and the second fixed electrode, and is individually connected to the first and second fixed electrodes. By applying a driving voltage to the movable part, the movable part may be bent toward the first fixed electrode or the second fixed electrode to perform light modulation.

  6. The light modulation element array according to claim 5, comprising a movable portion that is supported so as to be elastically displaceable and includes a movable electrode at least in part, and a fixed electrode that is disposed to face the movable portion, and the movable electrode. A microelectromechanical light modulation element that modulates the light incident on the movable part in a one-dimensional or two-dimensional manner by displacing the movable part by electrostatic force generated by applying a voltage between the electrode and the fixed electrode. Each of the light modulation elements has a drive circuit including a memory circuit, one of the electrodes is an electrode for writing an element displacement signal from the drive circuit, and the other is an electrode for applying a control voltage. A light modulation element array according to any one of claims 1 to 4, further comprising a control unit that performs light modulation based on the driving method of the light modulation element array according to any one of claims 1 to 4.

  In this light modulation element array, the voltage applied to one of the electrodes is increased by the control unit between the time when the movable part reaches the final movement destination and the time when the drive circuit outputs the next displacement signal to one electrode. Thus, the electrostatic force for localizing the movable part to the final movement destination increases. Thereby, even during the vibration sedation time, the movable part is latched by a large electrostatic force, and the address voltage can be written without causing a malfunction.

  The image forming apparatus according to claim 6 is a light source, the light modulation element array according to claim 5, an illumination optical system that irradiates the light modulation element array with light from the light source, and an emission from the light modulation element array. And a projection optical system that projects the projected light onto the image forming surface.

  In this image forming apparatus, the light modulation element array according to claim 5 is provided in a main part of the configuration, so that it is possible to write the address voltage without causing malfunction even during the vibration sedation time. In comparison, the driving cycle is shortened. As a result, high-speed photosensitive material exposure and display of a projector having a higher number of pixels are possible. In addition, in an image forming apparatus (exposure apparatus) in which gradation control is performed by turning on and off exposure light, the on / off time can be shortened, so that higher gradation can be realized.

  According to the driving method of the light modulation element array according to the present invention, one of the electrodes receives the displacement signal from the drive circuit, and the drive circuit receives the next displacement signal after the movable part reaches the final movement destination. Before applying to one of the electrodes, the applied voltage of either electrode is increased, decreased, or increased and decreased, so that a greater vibration-suppressing electrostatic force than before can be generated. Even during the vibration calming time immediately after the movable part reaches the final movement destination, the movable part is forcibly damped by a large electrostatic force, and can be latched. Therefore, it is not necessary to wait for the vibration to settle, and the address voltage can be written without causing a malfunction, even during the vibration calming time. As a result, the driving cycle can be shortened.

  According to the light modulation element array of the present invention, since the control unit that performs light modulation based on the light modulation element array driving method according to any one of claims 1 to 5 is provided, the movable part. The voltage applied to any one of the electrodes is controlled by the control unit until the drive circuit outputs the next displacement signal to any one of the electrodes after reaching the final movement destination. Even during the conversion time, the movable part can be latched by a large electrostatic force. Therefore, the address voltage can be written without causing a malfunction even during the vibration sedation time. As a result, the driving cycle can be shortened and high-speed all-pixel display can be performed.

  According to the image forming apparatus of the present invention, the light source, the light modulation element array according to claim 6, the illumination optical system that irradiates the light modulation element array with light from the light source, and the light modulation element array. Since the projection optical system for projecting light is provided, the driving cycle can be shortened as compared with the conventional apparatus. As a result, high-speed photosensitive material exposure and a projector with a higher number of pixels can be displayed.

Preferred embodiments of a light modulation element array driving method, light modulation element array, and image forming apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram of a light modulation element array and its peripheral memory loading circuit used in the driving method according to the present invention, FIG. 2 is a sectional view schematically showing one light modulation element in the light modulation element array, and FIG. FIG. 3 is an equivalent circuit diagram of the drive circuit shown in FIG. 2.

  The light modulation element array 100 includes the light modulation elements 200 shown in FIG. 2 that are individually addressable micromechanical elements. The light modulation element 200 is a deformable mirror device, and has a movable part (micromirror 3) that is supported by a hinge 11 so as to be elastically displaceable and includes a movable electrode at least partially. The micromirror 3 is displaced by tilting motion. As will be described later in detail, the light modulation element 200 is addressed by at least one pair of address electrodes, and controls the micromirror 3 to control the first position (left inclined position in FIG. 2) and the second position (FIG. 2). To the right tilt position).

  The light modulation element array 100 operates by reflecting light at the micromirrors 3 provided in the respective light modulation elements 200. That is, each light modulation element 200 represents one pixel of the image. The light modulation element 200 is attached to a drive circuit 51 as a memory cell. The drive circuit 51 stores data related to the on / off position.

  The memory loading circuit shown in FIG. 1 corresponds to the line loading in which the memory cell provided with the light modulation element 200 is loaded for every row (row). Therefore, the light modulation element array 100 includes 1 to P shift register circuits 53, a latch circuit 55, and a column driver circuit 57. The shift register circuit 53 is controlled by the clock signal CK.

  The 1st to Pth column data is simultaneously written in each shift register circuit 53, and when it becomes 1st to Nth column, the shift register circuit 53 is loaded and the data row is transferred to the latch circuit 55. The next data row can be loaded into the shift register circuit 53 while the data is latched and stored in the selected row of the light modulation element array 100. The latch circuit 55 is controlled by load, set, and set signals. A column driver circuit 57 drives one bit of row data to each column.

  A row decoder 59 is connected to the light modulation element array 100. Row decoder 59 receives address data representing 1 to M rows to be loaded into the memory, a row enable signal, and a read / write signal.

  The controller 61 sends load, set, and set signals to the latch circuit 55, and sends address data, row enable signals, and read / write signals to the row decoder 59. In addition, the controller 61 sends a drive signal to the column driver circuit 57.

  The data row transferred to the latch circuit 55 is transferred to the column driver circuit 57 as it is, and is output up and supplied to the data lines D and / D shown in FIG. When the data row is supplied to the data line / D, the row designation signal for writing the data row to any row by the address signal of FIG. 1 and the row decoder 59 is supplied to Row EN shown in FIG. . When the designated row is supplied and the designated row becomes active, the drive circuit 51 having the transistor TR is switched to store the written data row. By repeating these M times, data for all pixels is written.

  As shown in FIG. 2, the light modulation element 200 includes a fixed electrode 23 disposed so as to face the micromirror 3. The fixed electrode 23 includes a first address electrode 23a and a second address electrode 23b. The light modulation element 200 displaces the micromirror 3 by an electrostatic force generated by applying a voltage between the micromirror 3 and the fixed electrode 23, and modulates the light incident on the micromirror 3. The light modulation element array 100 includes the micro electro mechanical light modulation elements 200 arranged one-dimensionally or two-dimensionally. In the present embodiment, one of the electrodes is a fixed electrode 23 that writes element displacement signals Q and / Q (see FIG. 3) from the drive circuit 51, and the other is a movable electrode that applies a control voltage Vb. This movable electrode is also used as the micromirror 3. Hereinafter, the micromirror 3 and the movable electrode 3 will be described with the same reference numerals. In FIG. 2, 21 represents a landing site (pad), and 67 represents a circuit board.

  In the present invention, the controller 61 sends a voltage increase signal to the control unit 63 attached to the light modulation element array 100. The control unit 63 that has received the voltage increase signal increases the control voltage Vb of each light modulation element 200 at a predetermined timing via the control voltage generator 65. The control voltage Vb is supplied commonly to each row.

FIG. 4 is an explanatory diagram showing the behavior of the movable part of the driving method according to the present invention, FIG. 5 is an explanatory diagram of the driving sequence of the driving method according to the present invention, and FIG. It is explanatory drawing showing the correlation of these.
The predetermined timing is such that after the displacement signal Q, / Q from the drive circuit 51 is received by the fixed electrode 23 and the micromirror 3 reaches the final movement destination (left inclined position or right inclined position in FIG. 2), The time until the drive circuit 51 outputs the next displacement signals Q and / Q to the fixed electrode 23 is set by the controller 63.

This drive sequence will be described more specifically.
As shown in FIG. 4A, in the light modulation element 200, for example, the micromirror 3 is inclined to the left side (left side in FIG. 4) in the initial state. At this time, a constant control voltage Vb (+20 V) is applied to the movable electrode 3 as shown in FIG. On the other hand, the address voltage Va1 (0V) applied to the first address electrode 23a is set smaller than the address voltage Va2 (+ 5V) applied to the second address electrode 23b (Va1 <Va2). Accordingly, the voltage between the left electrodes of the micromirror 3 (| Vb−Va1 | = ΔV1 = 20V) becomes larger than the voltage between the right electrodes (| Vb−Va2 | = ΔV2 = 15V) (ΔV1> ΔV2). Thereby, the micromirror 3 is tilted to the left as the counterclockwise electrostatic torque TR1 becomes larger than the sum of the clockwise electrostatic torque TR2 due to the electrostatic force and the elastic restoring force TRe of the hinge 11.

  Next, as shown in FIGS. 4B and 5, the voltage applied to the first address electrode 23a and the second address electrode 23b is inverted while the control voltage Vb remains unchanged (Va1> Va2). That is, the address voltage Va1 (5V) is applied to the first address electrode 23a, the address voltage Va2 (0V) is applied to the second address electrode 23b, and the next displacement signal writing Tw is performed. At this time, the voltage between the electrodes becomes (ΔV1 = 15V) <(ΔV2 = 20V), and ΔV2 on the right side increases, but it remains held in the latched state due to the above-described action.

  In the driving sequence in which, for example, the micromirror 3 is shifted to the right tilt from this state, first, the address voltage (Va1> Va2) to the first address electrode 23a and the second address electrode 23b is left as it is, and the symbol (C ) As shown in the position, only the control voltage Vb is lowered (for example, Vb = 5V). Then, the electrostatic force on the left side of the micromirror 3 disappears (ΔV1 = 0), a slight electrostatic force works on the right side (ΔV2 = 5V), and the elastic restoring force of the hinge 11 is added to this, so that the micromirror 3 The left side rises and the left tilt is released.

  Next, when the control voltage Vb is returned to the original constant value (Vb = 20 V), as shown at the position (D) in FIG. 5, the voltage between the electrodes on the right side of the micromirror 3 (ΔV2 = 20 V) is changed to the left electrode. As shown in FIG. 4D, the micromirror 3 shifts to the right inclination. When the micromirror 3 transitions to the right inclination, the distance from the second address electrode 23b is shortened, so that the electrostatic force increases synergistically, and this time the right side is held in the landing site 21.

  Here, immediately after the right side of the micromirror 3 has landed, vibration is generated by receiving a reaction force from the landing site 21. At this time, that is, after the micromirror 3 reaches the final movement destination (right tilt position), the drive circuit 51 outputs the next displacement signals Q and / Q to the fixed electrode 23 (reference (E) in FIG. 5). Until the position), the control unit 63 increases the control voltage Vb (for example, Vb = 30 V). As a result, a larger vibration suppressing electrostatic force (ΔV2 = 30V) than before is generated, and the vibration is forcibly suppressed by the large electrostatic force even during the vibration calming time immediately after the micromirror 3 reaches the final movement destination. Latching in the state shown in 4 (E) is possible. In this state, the next displacement signal writing Tw is performed.

  When the writing Tw is completed, the address voltage (Va1> Va2) to the first address electrode 23a and the second address electrode 23b is left as it is, as shown above, as indicated by the symbol (F) in FIG. In addition, only the control voltage Vb is lowered (for example, Vb = 5 V). Then, the electrostatic force on the left side of the micromirror 3 disappears (ΔV1 = 0), a slight electrostatic force works on the right side (ΔV2 = 5V), and the elastic restoring force of the hinge 11 is added to this, so that the micromirror 3 The right side is lifted and the right-tilt is released.

  Next, when the control voltage Vb is returned to the original constant value (Vb = 20V), as shown at the position of the reference symbol (G) in FIG. 5, the voltage between the left electrodes of the micromirror 3 (ΔV1 = 20V) is changed to the right electrode. As shown in FIG. 4 (G), the micromirror 3 returns to the state of transition to the left inclination again.

  Thus, in the driving method of the light modulation element array 100 described above, the period from when the micromirror 3 reaches the final movement destination to when the driving circuit 51 outputs the next displacement signal to the fixed electrode 23 is As shown in FIG. 6, the voltage applied to the movable electrode 3 (that is, the control voltage Vb) is increased. As a result, a larger vibration-suppressing electrostatic force is generated than before, and the vibration is forcibly suppressed by the large electrostatic force even during the vibration calming time immediately after the micromirror 3 reaches the final movement destination, thereby enabling latching. That is, as shown in FIG. 5, the drive cycle Tc (= Tw + Tb) is shortened by shortening the time Tb when the previous write Tw ends and the next write Tw starts.

  Therefore, the structure remains the same, and there is no need to wait for the vibration to settle, even during the vibration suppression period (in other words, the data write timing can be shifted slightly forward). The address voltage can be written Tw from the early stage shown in FIG. 6 without causing malfunction.

  In the above example, the case where the control voltage Vb is increased to Vb = 30V with respect to the conventional Vb = 20V has been described, but it is needless to say that this is an example and the value is not limited thereto. FIG. 7 is an explanatory diagram showing the correlation between the rotation angle of the movable part and the voltage between the boundary electrodes at which the movable part is stably latched. The curve in the figure represents, for example, the correlation between the boundary electrode voltage X (V) and the rotation angle of the micromirror 3 when TR2 = TR1 + TRe is satisfied in the state of FIG. That is, when the interelectrode voltage is driven in a relationship of ΔVa <ΔVb <ΔVc, if the interelectrode voltage is ΔVa, a transition to an unstable region (region below the curve X (V)) is made with a slight angle change. Is stable in the stable region (region above the curve X (V)) even when the angle change is approximately θ = 4 ° when the voltage between electrodes is ΔVb, and approximately θ = 20 ° when the voltage between electrodes is ΔVc. It can be seen that even in the case of a change in angle, it is stable in the stable region.

  Accordingly, the interelectrode voltage ΔV (a, b, c) can be defined as a voltage that can maintain the contact state at the maximum vibration displacement after the micromirror 3 reaches the final movement destination. The higher it is, the more stable it is to maintain the contact state.

FIG. 8 is an explanatory diagram showing the behavior of the movable portion when the tilted state is maintained, and FIG. 9 is an explanatory diagram of a drive sequence when the tilted state is maintained.
4 and 5, the case where the left-inclined micromirror 3 is inclined to the right and transitions to the left-inclination has been described as an example. However, in FIGS. 8 and 9, the case where the left-inclined micromirror 3 maintains the state. explain.
As shown in FIG. 8A, when the micromirror 3 is tilted to the left, a constant control voltage Vb (+20 V) is applied to the movable electrode 3 as shown in FIG. The address voltage Va1 (0V) applied to the first address electrode 23a is set smaller than the address voltage Va2 (+ 5V) applied to the second address electrode 23b (Va1 <Va2). Therefore, the micromirror 3 tilts to the left as the counterclockwise electrostatic torque TR1 becomes larger than the sum of the clockwise electrostatic torque TR2 due to the electrostatic force and the elastic restoring force TRe of the hinge 11.

  Next, as shown in FIGS. 8B and 9, the next displacement signal writing Tw is performed. From this state, the address voltage (Va1 <Va2) to the first address electrode 23a and the second address electrode 23b is left as it is, and only the control voltage Vb is lowered (for example, Vb) as indicated by the position (C) in FIG. = 5V). Then, the electrostatic force on the right side of the micromirror 3 disappears (ΔV2 = 0), a slight electrostatic force works on the left side (ΔV1 = 5V), and the elastic restoring force of the hinge 11 is added to this, so that the micromirror 3 The left side rises and the left tilt is released.

  Next, when the control voltage Vb is returned to the original constant value (Vb = 20V), as shown in the position of the reference symbol (D) in FIG. 9, the voltage between the left electrodes of the micromirror 3 (ΔV1 = 20V) is changed to the right electrode. As shown in FIG. 8D, the micromirror 3 again shifts to the left inclination. When the micromirror 3 transitions to the left inclination, the distance from the first address electrode 23a is shortened, so that the electrostatic force increases synergistically and is held in a state where the left side is landed on the landing site 21 again.

  Here, immediately after the left side of the micromirror 3 has landed, vibration is generated by receiving a reaction force from the landing site 21. At this time, that is, after the micromirror 3 reaches the final movement destination (left inclined position), the drive circuit 51 outputs the next displacement signals Q and / Q to the fixed electrode 23 (reference (E) in FIG. 9). Until the position), the control unit 63 increases the control voltage Vb (for example, Vb = 30 V). As a result, a larger vibration suppressing electrostatic force (ΔV1 = 30 V) than before is generated, and the vibration is forcibly suppressed by the large electrostatic force even during the vibration calming time immediately after the micromirror 3 reaches the final movement destination. Latching in the state shown in FIG. In this state, the next displacement signal writing Tw is performed.

  When the writing Tw is completed, the address voltage (Va1 <Va2) to the first address electrode 23a and the second address electrode 23b is left as it is, as shown above, as indicated by the reference numeral (F) in FIG. In addition, only the control voltage Vb is lowered (for example, Vb = 5 V). Then, the electrostatic force on the right side of the micromirror 3 disappears (ΔV2 = 0), a slight electrostatic force works on the left side (ΔV1 = 5V), and the elastic restoring force of the hinge 11 is added to this, so that the micromirror 3 The left side rises and the left tilt is released.

  Next, when the control voltage Vb is returned to the original constant value (Vb = 20 V), as shown in the position of symbol (G) in FIG. 9, the voltage between the left electrodes of the micromirror 3 (ΔV1 = 20 V) is changed to the right electrode. As shown in FIG. 8 (G), the micromirror 3 returns to the state of transition to the left inclination again.

  As described above, even when the left inclined micromirror 3 maintains the state, after the micromirror 3 reaches the final movement destination, the drive circuit 51 outputs the next displacement signal to the fixed electrode 23. During this period, the control voltage Vb applied to the movable electrode 3 is increased, so that a large vibration suppressing electrostatic force is generated, and latching is possible even during the vibration sedation time.

  Therefore, according to the driving method described above, even when the left-inclined micromirror 3 maintains the state, the drive circuit 51 outputs the next displacement signal after the micromirror 3 reaches the final destination. In the meantime, since the control voltage Vb is increased, the micromirror 3 can be latched with a large electrostatic force during the vibration calming time, and the address voltage is written without waiting for the vibration to subside and without causing a malfunction. be able to. As a result, the driving cycle Tc can be shortened.

  In addition, the fixed electrode 23 has two first address electrodes 23 a and second address electrodes 23 b that tilt the micromirror 3 in different directions, and a driving voltage is alternately applied to the two fixed electrodes 23. Since the micromirror 3 is driven bidirectionally, the micromirror 3 is driven bidirectionally and can be arranged at the first and second positions. As a result, an optical modulation operation consisting of an ON state in which light incident on the movable part at the first position is reflected and an OFF state in which light incident on the movable part at the second position is deflected to the optical absorber is possible. It becomes.

  Note that if the control voltage Vb is increased before the micromirror 3 reaches the final movement destination, the micromirror 3 is accelerated and comes into contact with the micromirror 3, and vibration is increased. Further, even if the control voltage Vb is increased after writing is started, the effect of damping the micromirror 3 and shifting the writing timing forward cannot be obtained.

  And according to said light modulation element array 100, since the control part 63 which controls the increase in the control voltage Vb and performs light modulation based on said drive method was provided, even during the vibration calming time, The micromirror 3 is latched by a large electrostatic force, and the address voltage can be written without causing a malfunction. As a result, the driving cycle can be shortened and high-speed all-pixel display can be realized.

Next, a modified example of the driving method according to the present invention will be described.
FIG. 10 is an explanatory diagram of a driving sequence showing a modification example in which the address voltage is increased, and FIG. 11 is an explanatory diagram of a driving sequence showing a modification example in which the address voltage and the control voltage are increased.
In the above embodiment, the element displacement signal from the drive circuit 51 is written to the fixed electrode 23, the control voltage Vb is applied to the movable electrode 3, and the control voltage Vb applied to the movable electrode 3 The case where the micromirror 3 is forcibly damped and can be latched by being increased during the conversion time has been described, but in this modified example, as shown in FIG. While the same constant control voltage Vb is applied, the address voltage applied to the fixed electrode 23 is decreased during the vibration calming time.

  When writing is performed during vibration, the address voltage is inverted, and an unstable state of (electrode voltage in the deflection direction) <(electrode voltage in the reverse direction) is obtained, which is likely to cause a malfunction. Therefore, by reducing the address voltage before inversion of the address voltage, the difference between the electrode voltage in the deflection direction and the voltage between the electrodes in the reverse direction is reduced, so that the effect of address inversion can be reduced. In particular, the micro mirror 3 can be latched in a right-tilt state.

  Therefore, as in this modification, the forced vibration suppression of the micromirror 3 during the vibration sedation time can be realized by reducing the address voltage, and the drive cycle Tc similar to the above is shortened (from landing) The effect of shortening the time Td until writing) can be obtained.

  Further, as shown in FIG. 11, the driving method according to the present invention increases the control voltage Vb applied to the movable electrode 3 at the same time as the address voltage applied to the fixed electrode 23 is decreased during the vibration sedation time. It may be a thing. In this modification, the control unit 63 decreases the address voltage and increases the control voltage Vb, so that the movable part restraint in the deflection direction before and after the address voltage inversion is increased, and latching is possible in a right-tilt state. Become.

  Accordingly, since the malfunction of the micromirror 3 is eliminated even when the movable part vibrates, the data write timing can be shifted further forward (the time Td from landing to writing can be shortened).

In the light modulation element array 100 described above, the structure for performing the light modulation by inclining the micromirror 3 has been described as an example. However, the present invention is not limited to this structure, for example, a parallel plate type light modulation element. It can also be applied to.
That is, by disposing the movable part between the first fixed electrode and the second fixed electrode and individually applying a driving voltage to the first and second fixed electrodes, the movable part is The light modulation may be performed by bending toward the first fixed electrode or the second fixed electrode. Even with this configuration, the same effects as described above can be obtained.

  Next, an image forming apparatus configured using the light modulation element array 100 will be described. Here, as an example of the image forming apparatus, first, the exposure apparatus 300 will be described. FIG. 12 is a view showing the schematic arrangement of an exposure apparatus constituted by using the light modulation element array of the present invention. The exposure apparatus 300 includes an illumination light source 71, an illumination optical system 73, a light modulation element array 100 in which a plurality of light modulation elements 200 of the above-described embodiment are arranged in the same plane and two-dimensionally, a projection optical system 75, and the like. Is provided.

  The illumination light source 71 is a light source such as a laser, a high-pressure mercury lamp, and a short arc lamp. The illumination optical system 73 is, for example, a collimator lens that converts planar light emitted from the illumination light source 71 into parallel light. The parallel light that has passed through the collimator lens is perpendicularly incident on each light modulation element of the light modulation element array 100. As a means for collimating the planar light emitted from the illumination light source 71, there is a method of arranging two microlenses in series in addition to the collimating lens. Further, by using an illumination light source 71 having a small light emission point such as a short arc lamp, the illumination light source 71 may be regarded as a point light source, and parallel light may be incident on the light modulation element array 100. Moreover, the LED array which has LED corresponding to each light modulation element of the light modulation element array 100 is used as the illumination light source 71, and the light is emitted by bringing the LED array and the light modulation element array 100 close to each other to emit light. Parallel light may be incident on each light modulation element of the element array 100. If a laser is used as the illumination light source 71, the illumination optical system 73 may be omitted.

  The projection optical system 75 is for projecting light onto a recording medium 77 that is an image forming surface. For example, a microlens array having a microlens corresponding to each light modulation element of the light modulation element array 100 or the like. It is.

Hereinafter, the operation of the exposure apparatus 300 will be described.
Planar light emitted from the illumination light source 71 is incident on the illumination optical system 73, and the parallel light is incident on the light modulation element array 100. The reflection of light incident on each light modulation element 200 of the light modulation element array 100 is controlled according to the image signal. The light emitted from the light modulation element array 100 is photographed and exposed on the image forming surface of the recording medium 77 by the projection optical system 75. The photographing light is projected and exposed while moving in the scanning direction relative to the recording medium 77, and a large area can be exposed with high resolution. As described above, by providing the collimating lens on the light incident surface side of the light modulation element array 100, the light incident on the planar substrate of each modulation element can be converted into parallel light. In the figure, reference numeral 79 denotes an optical absorber for introducing off-light.

  The exposure apparatus 300 is not limited to using a collimating lens as the illumination optical system 73 but can be configured using a microlens array. In this case, each microlens of the microlens array corresponds to each light modulation element 200 of the light modulation element array 100, and is designed and adjusted so that the optical axis and focal plane of the microlens are aligned with the center of each light modulation element. The

  In this case, incident light from the illumination light source 71 is condensed by the microlens array into a region having a smaller area than one element of the light modulation element 200 and enters the light modulation element array 100. Reflection of light incident on each light modulation element 200 of the light modulation element array 100 is controlled according to an input image signal (element displacement signals Q and / Q). The light emitted from the light modulation element array 100 is projected and exposed onto the image forming surface of the recording medium 77 by the projection optical system 75. The projection light is projected and exposed while moving in the scanning direction relative to the recording medium 77, and a large area can be exposed with high resolution. Thus, since the light from the illumination light source 71 can be condensed by the microlens array, an exposure apparatus with improved light use efficiency can be realized.

  The lens surface shape of the microlens is not particularly limited, such as a spherical surface or a hemispherical surface, and may be a convex curved surface or a concave curved surface. Further, it may be a flat microlens array having a refractive index distribution, or may be an array of diffractive lenses such as Fresnel lenses or binary optics. The material of the microlens is, for example, transparent glass or resin. Resin is excellent from the viewpoint of mass productivity, and glass is excellent from the viewpoint of life and reliability. From an optical viewpoint, the glass is preferably quartz glass, fused silica, alkali-free glass, or the like, and the resin is preferably acrylic, epoxy, polyester, polycarbonate, styrene, vinyl chloride, or the like. The resin includes a photo-curing type and a thermoplastic type, and is preferably selected as appropriate according to the manufacturing method of the microlens.

Next, a projection apparatus will be described as another example of the image forming apparatus.
FIG. 13 is a diagram showing a schematic configuration of a projection apparatus configured using the light modulation element array of the present invention. Components similar to those in FIG. 12 are denoted by the same reference numerals, and description thereof is omitted. A projector 400 as a projection apparatus includes an illumination light source 71, an illumination optical system 73, a light modulation element array 100, and a projection optical system 81. The projection optical system 81 is an optical system for a projection device that projects light onto a screen 83 that is an image forming surface. The illumination optical system 73 may be the collimator lens described above or a microlens array.

Next, the operation of the projector 400 will be described.
Incident light from the illumination light source 71 is condensed into a region having a smaller area than one element of the light modulation element 200 by, for example, a microlens array, and enters the light modulation element array 100. The reflection of light incident on each light modulation element 200 of the light modulation element array 100 is controlled according to the image signal. The light emitted from the light modulation element array 100 is projected and exposed on the image forming surface of the screen 83 by the projection optical system 81. As described above, the light modulation element array 100 can be used for a projection apparatus, and can also be applied to a display apparatus.

  Therefore, in the image forming apparatus such as the exposure apparatus 300 and the projector 400, the above-described light modulation element array 100 is provided in the main part of the configuration, so that the address voltage can be written without causing malfunction even during the vibration suppression period. As a result, the driving cycle Tc is shortened as compared with the conventional apparatus. As a result, high-speed photosensitive material exposure and display of a projector having a higher number of pixels are possible. Further, in the image forming apparatus (exposure apparatus 300) in which gradation control is performed by turning on and off the exposure light, it is possible to realize a higher gradation by shortening the on / off time. As a result, high-speed photosensitive material exposure and a projector with a higher number of pixels can be displayed.

  In the above-described embodiment, the configuration of the light modulation element 200 in which the micromirror 3 that is a movable part is swung in the left-right direction (bidirectional) has been described as an example. However, in the present invention, the movable part is flexible. Applicable to unidirectional and bidirectional light modulation elements consisting of a thin film (diaphragm), and the flexible thin film disposed with a gap to the substrate 67 approaching and separating from the substrate 67 by electrostatic force and elastic restoring force Even so, the same effects as described above can be obtained.

It is a light modulation element array used in the driving method according to the present invention and its peripheral memory loading circuit diagram. It is sectional drawing which represented typically one light modulation element in a light modulation element array. FIG. 3 is an equivalent circuit diagram of the drive circuit shown in FIG. 2. It is explanatory drawing showing the behavior of the movable part of the drive method which concerns on this invention. It is explanatory drawing of the drive sequence of the drive method which concerns on this invention. It is explanatory drawing showing the correlation with the behavior at the time of the displacement of a movable part, and a control voltage. It is explanatory drawing showing the correlation of the rotation angle of a movable part, and the voltage between boundary electrodes by which a movable part is latched stably. It is explanatory drawing showing the behavior of the movable part in case an inclination state is maintained. It is explanatory drawing of the drive sequence in case an inclination state is maintained. It is explanatory drawing of the drive sequence showing the modification which reduces an address voltage. It is explanatory drawing of the drive sequence showing the modification which reduces an address voltage and increases a control voltage. It is a figure which shows schematic structure of the exposure apparatus comprised using the light modulation element array of this invention. It is a figure which shows schematic structure of the projection apparatus comprised using the light modulation element array of this invention. It is a disassembled perspective view which shows one pixel 1 of a light modulation element array. It is sectional drawing which represented typically the light modulation element shown in FIG. FIG. 16 is an explanatory diagram of a drive sequence of the light modulation element shown in FIG. 15. It is operation | movement explanatory drawing of the conventional all pixel display. It is explanatory drawing of the drive sequence at the time of writing in during a vibration calming time. It is explanatory drawing of the malfunction which arises by the writing in vibration sedation time.

Explanation of symbols

3 Movable electrode, micromirror (movable part), (the other electrode)
23 Fixed electrode 23a First address electrode (fixed electrode), (one electrode)
23b Second address electrode (fixed electrode), (one electrode)
51 Drive Circuit 63 Control Unit 71 Light Source 73 Illumination Optical System 75 Projection Optical System 77 Recording Medium (Image Forming Surface)
100 light modulation element array 200 light modulation element 300 exposure apparatus (image forming apparatus)
400 projector (image forming apparatus)
Q, / Q Element displacement signal Vb Control voltage

Claims (6)

A movable part that is supported so as to be elastically displaceable and has a movable electrode at least in part; and first and second fixed electrodes that are arranged opposite to the movable part and displace the movable part in different directions. A microelectromechanical system that displaces the movable portion by electrostatic force generated by voltage application between the movable electrode and the first and second fixed electrodes, and modulates light incident on the movable portion. The light modulation elements are arranged one-dimensionally or two-dimensionally, each of the light modulation elements has a drive circuit including a memory circuit, and one of the movable electrode and the fixed electrode is from the drive circuit. It is an electrode for writing an element displacement signal, and the other is an electrode for applying a control voltage.
One of the electrodes receives a displacement signal from the drive circuit, and after the movable part reaches the final movement destination, the drive circuit outputs the next displacement signal to any one of the electrodes. A method of driving a light modulation element array, comprising: controlling a voltage applied to any one of the electrodes to localize the movable part to the final movement destination.   The fixed electrode disposed on the final movement destination side of the movable part after the movable part reaches the final movement destination and before the drive circuit outputs the next displacement signal to any one of the electrodes. 2. The method of driving an optical modulation element array according to claim 1, wherein an inter-electrode voltage between the movable electrode and the movable electrode is increased.   2. The voltage from the drive circuit is reduced between the time when the movable part reaches the final movement destination and the time when the drive circuit outputs a next displacement signal to the one electrode. Alternatively, the method of driving the light modulation element array according to claim 2.   The light modulation element swingably supports the movable part, and the first and second fixed electrodes are arranged on the same side with respect to the movable part. The first and second fixed electrodes 4. The light modulation element array according to claim 1, wherein light modulation is performed by individually applying a driving voltage to the movable portion to incline the movable portion in different directions. 5. Driving method. A movable part that is supported so as to be elastically displaceable and includes a movable electrode at least in part, and a fixed electrode that is disposed to face the movable part, and applies a voltage between the movable electrode and the fixed electrode Displacement of the movable part by electrostatic force generated by the micro electromechanical light modulation elements that modulate the light incident on the movable part are arranged one-dimensionally or two-dimensionally, each of the light modulation elements Comprises a drive circuit including a memory circuit, and one of the electrodes is an electrode for writing an element displacement signal from the drive circuit, and the other is a light modulation element array in which a control voltage is applied.
5. A light modulation element array, comprising: a control unit that performs light modulation based on the driving method of the light modulation element array according to any one of claims 1 to 4. A light source;
The light modulation element array according to claim 5;
An illumination optical system for irradiating the light modulation element array with light from the light source;
An image forming apparatus comprising: a projection optical system that projects light emitted from the light modulation element array onto an image forming surface.

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