KR19990035352A - Driving circuit of thin film type optical path control device - Google Patents

Abstract

The present invention relates to a thin film type optical path control device comprising M × N (M, N is a natural number) actuators and a driving circuit for individually driving each of the actuators, comprising: a restoration signal for restoring the actuator to an initial state before driving; An image signal for driving the actuator so as to correspond to image data applied from the outside; By providing the drive circuit of the thin film type optical path control device characterized in that the actuator is driven by a drive signal comprising a buffer signal for buffering a signal difference between the restoration signal and the image signal, It is effective to prevent shortening of life.

Description

Driving circuit of thin film type optical path control device

The present invention relates to thin film type optical path control apparatus (AMA), and more particularly to thin film type optical path configured to relieve electrical stress applied to the strained layer when the initial tilt angle of the thin film type optical path control device is restored. It relates to a drive circuit of the adjusting device.

AMA is a type of projection image display device, and refers to a device for displaying a predetermined image by reflecting light incident from a light source at a predetermined angle for each pixel of M × N (M, N is a natural number). Compared to the CRT representing a direct-view image display device, it operates at a lower voltage, consumes less power, and provides an image without distortion. In addition, liquid crystal display (LCD) and DMD ( Its light efficiency is higher than that of Deformable Mirror Device, and its development is actively underway.

In the above-described AMA, the unit pixels having a cross section as shown in FIG. 1 form an M × N structure to form an AMA module 350 as shown in FIG. 2, and the AMA module 350 configured as described above is shown in FIG. 2. It is operated by a driving circuit as shown in Figure 1 to 5, the operation of the M × N thin film type optical path control apparatus according to the prior art will be described briefly as follows.

1 is a cross-sectional view showing a cross section of a unit pixel constituting a general M × N thin film type optical path control device, FIG. 2 is a block diagram showing a driving circuit for driving a general M × N thin film type optical path control device. 3 is a circuit diagram showing a driving circuit corresponding to a unit pixel constituting a general M × N thin film type optical path adjusting device. 4 and 5 are waveform diagrams showing driving signals for driving the M × N thin film type optical path adjusting device according to the related art.

Hereinafter, to facilitate understanding of the present invention, the M × N thin film type optical path adjusting device is called an AMA module, and each unit pixel constituting the M × N thin film type optical path adjusting device is called an AMA pixel.

First, when a synchronization signal and image data are externally applied to the system control unit 310, the system control unit 320 may drive the M × N AMA pixel in the AMA module to correspond to the image signal applied from the outside. The drive controller 320 controls the gate driver 330 and the source driver 340. In this case, the system controller 310 may control the driving signal to be applied to each AMA pixel from the gate driver 330 and the source driver 340 based on the synchronization signal applied from the outside.

By driving control of the system controller 330, the gate driver 300 applies a gate signal so that the driving signal provided from the source driver 340 may be sequentially applied to the M × N thin film type optical path adjusting device constituting the AMA module. The source driver 330 generates a driving signal corresponding to the image data applied from the outside. In this case, the driving signal generated by the source driver 330 may be a voltage of a predetermined level.

In addition, the common electrode unit 320 provides a common voltage, such as a ground voltage, to the upper electrode 240 of the AMA pixel under the control of the system controller 310.

Thereafter, when the gate signal generated by the gate driver 330 is provided to the gate electrode 120 of the AMA pixel along the gate line shown in FIG. 3, the gate electrode 120 is turned on, and thus the switch driver 340 is turned on. The driving signal generated at is applied to the drain electrode 115.

Meanwhile, since the drain electrode 115 makes an electrical connection with the lower electrode 220 through the metal layer 140 made of a conductive metal and the distributor 270, the driving signal applied to the drain electrode 115 is the metal layer 140. And the lower electrode 220 via the distributor 270.

In this case, since the common voltage provided from the common electrode unit 320 is applied to the upper electrode 240, a potential difference between the driving signal applied to the lower electrode 220 and the common voltage applied to the upper electrode 240 occurs. Therefore, an electric field is generated between the lower electrode 220 and the upper electrode 240 corresponding to the potential difference between the driving signal and the common voltage.

Meanwhile, the deformable portion 230 formed between the lower electrode 220 and the upper electrode 240 may be PZT (Pb (Zr, Ti) O ₃ ) or PLZT ((Pb, La) (Zr, Ti) O ₃ Piezoelectric ceramics, such as), or electrodistorted ceramics, such as PMN (Pb (Mg, Nb) O ₃ ), have a property of deforming in proportion to an electric field.

Thus, the deformable portion 230 is deformed in proportion to the electric field generated by the electric potential difference between the lower electrode 220 and the upper electrode 240 to incline the entire actuator 240 at a predetermined angle proportional to the applied electric field. .

By the operation process described above, in the state in which the actuator 200 is inclined at a predetermined angle, the light incident from the light source is reflected at a predetermined angle corresponding to the inclination angle on the surface of the upper electrode 240. In this case, the upper electrode 230 is composed of a conductor having good light reflection efficiency such as aluminum (Al), and will simultaneously serve as a common electrode and a mirror.

By the above-described process, each of the M × N AMA pixels constituting the AMA module 350 reflects the light incident from the light source at a predetermined angle, thereby forming a predetermined image corresponding to the input image data.

Meanwhile, as shown in FIG. 4, the driving signal generated by the source driver 340 according to the related art has a voltage level corresponding to image data applied from the outside during the initial 66.7 μs of the time of 33 ms corresponding to one frame. An excitation video signal was generated.

However, since the conventional operation of the actuator 200 by such a drive signal is driven by a hysteresis characteristic, the actuator 200 cannot be restored to the initial tilt angle until the next image signal is applied, and also the drive of the actuator 200. If this is repeated, there is a problem that the initial tilting angle of the actuator 200 increases.

Therefore, in the related art, a refresh signal is used to improve the problem of lowering the contrast due to the above-described problem. As shown in FIG. A recovery signal with a predetermined voltage level (-Vrf) inverted was generated. That is, after the actuator 200 spaced apart from the initial tilting angle by a predetermined interval is restored to the initial tilting angle by the restoration signal, an image signal is applied.

However, in such a conventional method, since the electrical stress received by the strained layer 230 increases as the restoration signal increases in the original image signal, the physical properties (such as resistance and dielectric constant) of the strained layer are lowered. In addition to this, there was a problem that the life of the strained layer 230 is also shortened.

The present invention has been made to solve the above-mentioned conventional problems, the present invention is to apply a restoration signal for restoring the actuator of the thin film type optical path control device to the initial tilting angle, a predetermined interval between the restoration signal and the image signal An object of the present invention is to provide an initial tilt angle recovery circuit of a thin film type optical path adjusting device configured to apply a stand-by signal.

In order to achieve the above object, in the present invention, in the thin film type optical path control device composed of M x N (M, N is a natural number) actuators and a driving circuit for individually driving each of the actuators, the initial stage before driving the actuators A restore signal for restoring to a state; An image signal for driving the actuator so as to correspond to image data applied from the outside; A drive circuit for a thin film type optical path control device is provided, wherein the actuator is driven by a drive signal including a buffer signal for buffering a signal difference between the restoration signal and the image signal.

1 is a cross-sectional view showing a cross section of a unit pixel constituting a general M × N thin film type optical path control device;

2 is a block diagram showing a driving circuit for driving a general M × N thin film type optical path control device;

3 is a circuit diagram showing a driving circuit corresponding to a unit pixel constituting a general M × N thin film type optical path adjusting device;

4 is a waveform diagram showing a driving signal for driving an M × N thin film type optical path adjusting device according to a conventional embodiment;

5 is a waveform diagram showing a driving signal for driving an M × N thin film type optical path adjusting device according to another embodiment of the present invention;

6 is a waveform diagram showing a drive signal for driving the M × N thin film type optical path adjusting device according to the present invention;

<Description of Symbols for Main Parts of Drawings>

100 driving substrate 110 semiconductor substrate

115: drain electrode 120: source electrode

125 gate electrode 130 field oxide film

135: insulating layer 140: metal layer

145: protective layer 150: etch stop layer

160: air gap 200: actuator

210: membrane 220: lower electrode

230: strained layer 240: upper electrode

250: stripe 260: power distribution hole

270: distributor 310: system control unit

320: common electrode 330: gate driver

340: source driver 350: AMA module

Advantages and other objects and advantages of the present invention will be more clearly understood by the following description with reference to the attached FIGS. 1, 3, and 6.

1 to 3 have been described above, Figure 6 is a waveform diagram showing a drive signal for driving the M × N thin film type optical path control apparatus according to the present invention.

Referring to FIG. 6, it can be seen that the driving signal for driving the M × N thin film type optical path adjusting device includes a refresh signal, a buffering signal, and a video signal. . In this case, the driving signal according to the present invention is sequentially applied to the restoration signal, the buffer signal, and the image signal, and further, on the basis of the buffer signal, the restoration signal and the image signal have inverted voltage levels. It would be desirable to have other predetermined voltage levels.

Hereinafter, a process of applying a driving signal to the actuator 200 will be omitted since it has been described above, and will be described based on the state in which the actuator 200 is driven by the driving signal according to the present invention.

First, when the actuator 200 is spaced apart from the initial tilting angle by a predetermined angle due to the previous driving, and a restoration signal of the driving signal according to the present invention is applied to the lower electrode 220, the upper electrode 240 may be grounded. Since the same common voltage is applied, a predetermined potential difference occurs between the lower electrode 220 and the upper electrode 240.

Therefore, a predetermined electric field corresponding to the potential difference is formed between the lower electrode 220 and the upper electrode 240, and such an electric field will act on the strained layer 230. At this time, since the reconstruction signal is a signal inverted from the image signal, the electric field acting on the strained layer 230 will also have an inverted polarity.

Due to the influence of an electric field having a polarity opposite to that of the actuator 200, the domains in the deformable layer 230 are rearranged in the opposite direction to that of the actuator 200.

By rearranging the domains within the strained layer 230, the strained layer 230 will cause a contraction action in a direction opposite to the driving direction of the actuator 200, and the actuator 200 will tilt in a direction opposite to the driving direction. At this time, since the reconstruction signal has a predetermined signal level corresponding to the degree that the actuator 200 is spaced apart from the initial tilting angle, the actuator will be positioned at the initial tilting angle.

Thereafter, a signal from which the reconstruction signal has been removed, that is, a buffer signal is applied for a predetermined time immediately before the image signal is applied, and such a buffer signal has the same voltage level as the common voltage applied to the upper electrode 240. In this case, the time when the buffer signal is applied may be such that the image signal is applied while the domains in the deformable layer 230 do not rearrange and the actuator 200 maintains the initial tilt angle.

As described above, when the actuator 200 is positioned at the initial tilting angle by the restoration signal and the image signal is applied to the strained layer 230 while the voltage difference corresponding to the signal level of the restoration signal is reduced by the buffer signal, the lower electrode An electric field corresponding to the potential difference between the image signal and the common voltage is formed between the 220 and the upper electrode 240, and the domains in the strained layer 230 are rearranged corresponding to the electric field. In this case, the signal applied to the lower electrode 220 does not change from the reconstruction signal to the image signal but changes from the buffer signal at the common voltage level to the image signal, thereby reducing the variation of the electric field acting on the strained layer 230.

Thus, the electrical stress applied to the strained layer 230 is reduced by the signal level of the recovery signal.

On the other hand, due to the shrinking action of the strained layer 230 by rearranging the domains in the strained layer 230, the actuator 200 is driven at a predetermined angle corresponding to the image signal applied to the lower electrode 220.

The thin film type optical path adjusting device may form a predetermined image corresponding to image data applied from the outside by repeating the above-described operation process and reflecting the light incident from the light source to a predetermined angle by the driving signal according to the present invention. .

As described above, when the driving signal according to the present invention is used, the actuator is forcibly restored to the initial tilting angle by using the restoration signal in order to prevent contrast degradation, and a buffer signal is inserted between the restoration signal and the image signal. By alleviating the potential difference applied to the strained layer, it is possible to prevent the deterioration of physical properties and the shortening of the life of the strained layer 230.

Claims (4)

In the thin film type optical path control device comprising M × N (M, N is a natural number) actuators and a driving circuit for driving each of the actuators individually, A restoration signal for restoring the actuator to an initial state before driving; An image signal for driving the actuator so as to correspond to image data applied from the outside; And said actuator is driven by a drive signal comprising a buffer signal for buffering a signal difference between said reconstruction signal and said image signal. The driving circuit of claim 1, wherein the driving signal comprises the restoration signal, a buffer signal, and an image signal in units of a driving signal corresponding to one frame. The drive circuit according to claim 1, wherein the buffer signal is generated between the restoration signal and the image signal. 4. The drive circuit according to any one of claims 1 to 3, wherein each signal constituting the drive signal is a voltage having a different level.