KR19990043441A - Driving method of thin film type optical path control device - Google Patents

Abstract

The present invention applies a common signal to the upper electrode, and applies a drive signal consisting of a precharge signal and a holding signal to the lower electrode, driving the thin film type optical path control device for driving the actuator by an electric field formed between the two electrodes A method of controlling a thin film type optical path comprising: applying a reconstruction signal of a predetermined voltage level to the common signal for a predetermined time just before applying the precharge signal to the lower electrode in order to prevent contrast degradation. By providing a driving method of the device, there is an effect that can improve the performance and reliability of the thin-film optical path control device.

Description

Driving method of thin film type optical path control device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving thin-film optical path control apparatus (AMA), and more particularly, to a thin film optical path configured to restore an initial tilting angle after an actuator of the thin-film optical path control device is driven. It relates to a driving method 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 the driving circuit as shown in Figure 1 to 4, 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 is a waveform diagram showing a drive signal for driving the M × N thin film type optical path adjusting device according to the prior 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 the drive control of the system controller 330, the gate driver 300 applies the gate signal so that the driving signal provided from the source driver 340 can be sequentially applied to the M × N thin film type optical path adjusting device constituting the AMA module. The source driver 330 generates a drive 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 source 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 is precharged for about 4 ms at the beginning of one horizontal period of 63.5 μs out of the 33 ms time corresponding to one frame. and a holding signal for maintaining a predetermined voltage level corresponding to the image data applied from the outside by the discharge for the remaining time.

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, the actuator is spaced at a predetermined interval from the initial tilting angle in the initial state, so that there is a problem that the contrast of the thin film type optical path control device is lowered.

The present invention has been made to solve the above-mentioned conventional problems, an object of the present invention is to restore the initial tilting angle immediately before the drive of the thin film type optical path control device, and then drive the actuator configured to drive the thin film type optical path control device. To provide.

In order to achieve the above object, in the present invention, by applying a common signal to the upper electrode, and applying a drive signal consisting of a pre-charge signal and a holding signal to the lower electrode, the two electrodes A driving method of a thin film type optical path control device for driving an actuator by an electric field formed therebetween, wherein the restoration signal of a predetermined voltage level is applied to the common signal for a predetermined time just before applying the precharge signal to the lower electrode. The present invention provides a method for driving a thin film optical path control device.

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;

FIG. 5 is a waveform diagram showing waveforms of signals applied to respective constituent members of the thin film type optical path adjusting device according to the driving method of the thin film type optical path adjusting device according to the preferred embodiment of the present invention; FIG.

* Explanation of symbols for main parts of the 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 driving unit 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. 3 and 5. At this time, the signal level of each waveform shown in Figure 5 is according to a preferred embodiment of the present invention, it will be easily applicable within the scope of the signal level limited in the present invention.

FIG. 3 has been described above, and FIG. 5 is a waveform diagram showing waveforms of signals applied to respective constituent members of the thin film type optical path adjusting device according to the driving method of the thin film type optical path adjusting device.

Referring to FIG. 5, the signal illustrated in FIG. 5A is a gate signal generated by the gate driver 330 under the control of the system controller 310 and is applied to each AMA pixel constituting the AMA module 350. . In this case, the gate signal is a low active signal, and in the exemplary embodiment of the present invention, one horizontal scanning period 63.5 corresponding to an AMA pixel to be driven among 33 ms corresponding to one screen for the NTSC (National Television System Committee) μs) remain on at -5V and remain off at 17V for the remainder of the time.

The signal shown in FIG. 5B is a common signal generated by the common electrode unit 320 under the control of the system controller 310. In a preferred embodiment of the present invention, the signal is driven at 3V during the initial 2μs of 63.5μs with the gate signal turned on. It is applied, and 0V is applied to the rest of the interval. In this case, in the preferred embodiment of the present invention, the case where the common signal is applied at 3 V for 2 μs has been exemplified, but more preferably, it is preferably selectively applied within the range of 2 to 15 V for 1.5 to 2.5 μs. In addition, the common signal is a signal applied to the upper electrode 240, and is applied at 2 to 15 V during the initial 1.5 to 2.5 μs of the 63.5 μs in which the gate signal is turned on, and the lower electrode (via the drain electrode 115 during the same time). A source signal applied at 0 V and a reverse potential are formed on the 220 to restore the actuator 200 to an initial tilting angle, and thus a signal of a common signal applied by the actuator 200 corresponding to the distance spaced from the initial tilting angle. You will have to vary the level.

Meanwhile, the signal shown in FIG. 5C is a source signal generated by the source driver 340 under the control of the system controller 310. The signal shown in FIG. 5C is applied at 17V for 1.5 to 2.5 from the time when the common signal is turned off and the rest of the time. Since it is applied at 0V, it will be more preferable to apply for about 2μs. At this time, the period of applying the 17V for 1.5 to 2.5μs from the time of turning off is the precharge time. After charging the predetermined voltage during this period, the predetermined signal level corresponding to the image data applied from the outside is charged. By discharging up to, the actuator 200 is driven.

The signal shown in FIG. 5D is a signal for actually operating the actuator 200 according to FIGS. 5A to 5C. During the initial 2 μs of the period when the gate signal is turned on, the signal of 2 to 15V and the source signal of 0V are generated. The reversal potential is applied a reconstruction signal of -2 to -15V, and during the next 2μs precharge time, a predetermined voltage is charged using the potential difference between the common signal of 0V and the source signal of 17V, and the precharge in the remaining sections. By discharging the voltage charged in time to a predetermined voltage level, the voltage level corresponding to the image data applied from the outside is maintained.

The operation method of the thin film type optical path adjusting device according to the present invention for driving the thin film type optical path adjusting device using the above-described waveform will now be described.

First, the system controller 310 controls the gate driver 330, the source driver 340, and the common electrode part 320 in response to a timing at which a predetermined AMA pixel is to be driven.

Accordingly, in order to drive a predetermined AMA pixel provided in the AMA module 350 under the control of the system controller 310, the gate driver 330 applies a gate signal of 17V to the gate electrode 125. A gate signal of -5V is applied to the gate electrode 125 as shown in FIG. 5A during one horizontal scanning period (63.5 µs) out of 33 ms corresponding to one screen for NTSC.

In this case, since the back bias voltage is applied to the driving substrate at 17V, the back bias voltage is maintained at 17V while the gate signal is applied at 17V. However, while the gate signal is applied at -5V, the back bias voltage is applied to the driving substrate. As a result, a channel is formed between the source electrode 130 and the drain electrode 115, that is, the driving element corresponding to the predetermined AMA pixel to be driven is turned on.

Meanwhile, while the common electrode 320 is applying the 0 V common signal to the upper electrode 240, under the control of the system controller 310, as shown in FIG. 5B, from the time when the gate signal is turned on, the common electrode 320 is turned on. A common signal having a signal level in the range of 2 to 15 V (3 V in the figure) is turned on for 1.5 to 2.5 μs (2 μs in the figure) and is applied to the upper electrode 240.

On the other hand, while applying a common signal having a signal level within the range of 2 to 15V (3V in the figure) in the common electrode unit 320 to the upper electrode 240, the source driver 340, as shown in Figure 5c, The source signal of 0V is applied to the source electrode 120 under the control of the system controller 310.

At this time, since a channel is formed between the source electrode 120 and the drain electrode 115 due to the potential difference between the gate signal and the back bias signal, the source signal applied to the source electrode 120 is a drain electrode. Via 115, it is applied to the lower electrode 220.

Therefore, a common signal of 2 to 15V (3V in the figure) is applied to the upper electrode 240, and a source signal of 0V is applied to the lower electrode 220, and thus, between the upper electrode 240 and the lower electrode 220. Since the reverse potential of -2 to -15V (-3V in the figure) is formed as shown in FIG. 5D, the actuator 200 is tilted in a direction opposite to the direction in which the tilt is made in response to the external image data, thereby providing an initial tilt angle. Will keep. At this time, since the turn-on period of the common signal is a signal for restoring the actuator 200 spaced by a predetermined angle from the initial tilting angle to the initial tilting angle, the signal level of the common signal is that the actuator 200 is spaced apart from the initial tilting angle. It should be applied corresponding to the angle.

As described above, in the state where the actuator 200 maintains the initial tilting angle, the system control unit 310 may again rotate the common electrode unit 320 and the source driving unit to tilt the actuator 200 corresponding to image data applied from the outside. 340 will be controlled, where a gate signal of -5V is still being applied to the gate electrode 125.

On the other hand, while the common electrode 320 is applied to the upper electrode 240 with a common signal having a signal level in the range of 2 to 15V (3V in the figure), when the 1.5 to 2.5μs (2μs) elapses, the system controller 310 ) And is turned off to apply a common signal of 0V to the upper electrode 240 as shown in FIG. 5B.

When the source driver 340 also applies a source signal of 0V to the source electrode 120, when 1.5 to 2.5 μs (2 μs in FIG. 2) elapses, as shown in FIG. 5C, a source signal of 17 V is applied to the source electrode. To (120). At this time, since a channel is formed between the source electrode 120 and the drain electrode 115 due to the potential difference between the gate signal and the back bias signal, the source signal applied to the source electrode 120 is a drain electrode. Via 115, it is applied to the lower electrode 220.

Therefore, since a common signal of 0 V is applied to the upper electrode 240 and a source signal of 17 V is applied to the lower electrode 220, a potential difference of 17 V is formed between the upper electrode 240 and the lower electrode 220. As shown in FIG. 5D, the actuator 200 will charge a voltage corresponding to the signal level of the source signal during 1.5-2.5 μs (2 μs in the figure) to which the source signal is applied. At this time, the source signal of 17V is a precharge signal for charging as described above.

Then, when charging is completed by a precharge signal for 1.5 to 2.5 μs (2 μs in the figure), the system controller 310 will drive control the source driver 340 to turn off the source signal to 0V. Under the control of the system controller 310, the source driver 310 turns off the source signal of 17V and applies a source signal of 0V to the source electrode 120 as shown in FIG. 5C.

Accordingly, a common signal of 0 V is applied to the upper electrode 240, and a source signal of 0 V is also applied to the lower electrode 240, so that the potential difference between the upper electrode 240 and the lower electrode 220 is 0 V, but the actuator 200 is applied. ) Is charged to a predetermined voltage level by the precharge signal, and thus will have a predetermined voltage level as shown in FIG. 5D by discharge. At this time, the predetermined voltage level maintained while discharging the charged voltage corresponds to image data applied from the outside, and this voltage is referred to as a holding signal, and the actuator 200 operates for 33 ms corresponding to one screen for NTSC. It will be tilted at an angle corresponding to the signal level of the holding signal.

As described above, when the thin film type optical path adjusting device is driven based on the driving method of the thin film type optical path adjusting device according to the present invention, the actuator 200 is initially tilted in response to the signal level of the common signal before driving the actuator 200. By restoring to an angle, the lowering of the contrast of the thin film type optical path control device can be prevented, whereby the reliability of the thin film type optical path control device can be improved.

Claims (3)

A thin film type for driving an actuator by an electric field formed between the two electrodes by applying a common signal to the upper electrode and applying a driving signal consisting of a pre-charge signal and a holding signal to the lower electrode. In the driving method of the optical path control device, And a restoration signal of a predetermined voltage level is applied to the common signal for a predetermined time just before the precharge signal is applied to the lower electrode. The method of claim 1, wherein the restoration signal is applied in a voltage level range of 2 to 15V. The method of claim 1 or 2, wherein the reconstruction signal is applied within a time range of 1.5 to 2.5 s immediately before the precharge signal.