KR20010001561A - Optical projection system having thin-film micromirror array-actuated panel - Google Patents

Abstract

PURPOSE: A projection image displaying device is provided to alternately drive unit actuators of a thin-film micromirror array-actuated(TMA) panel in upward/downward directions relating to one signal, so as to alleviate a mechanical stress of the actuator and to prevent a ghost on a screen. CONSTITUTION: A light source(102) emits rays. A thin-film micromirror array-actuated(TMA) panel(112) arranges matrix-typed pixels composed of mirrors and actuators. The mirrors reflect the emitted rays. The actuators formed on lower sides of the mirrors transform the mirrors according to applied signals. The actuators are alternately driven to upward/downward directions relating to one signal in the TMA panel(112). A projection stop(114) concentrates flux of the rays reflected from each mirror. A projection lens(116) projects the rays passing through the projection stop(114) on a screen.

Description

Projection type image display device including thin-film mirror array panel {OPTICAL PROJECTION SYSTEM HAVING THIN-FILM MICROMIRROR ARRAY-ACTUATED PANEL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection image display device, and more particularly, to a projection image display device including a thin-film micromirror array-actuated (hereinafter referred to as TMA) panel. The present invention relates to a projection image display device that can prevent afterimages from appearing on a screen by alternately driving in a downward direction.

Optical path control devices or spatial light modulators for projecting optical energy onto the screen can be applied to various fields such as optical communication, image processing and information display devices. Typically, image processing apparatuses using such an optical modulator are classified into a direct view type image display device and a projection type image display device according to a method of displaying optical energy on a screen.

An example of a direct view image display device is a CRT (Cathode Ray Tube), which is a so-called CRT device, which has excellent image quality but increases in weight and volume as the size of the screen increases, leading to increased manufacturing costs. There is. Examples of the projection image display apparatus include a liquid crystal display (LCD), a deformable mirror device (DMD), and an actuated mirror array (AMA). Such projection image display apparatuses can be further divided into two groups according to their optical characteristics. That is, devices such as LCDs can be classified as transmission light modulators, while DMD and AMA can be classified as reflective light modulators.

Transmission optical modulators, such as LCDs, have a very simple optical structure, which makes them thinner, lighter in weight, and smaller in volume. However, the light efficiency is low due to the polarity of the light, there is a problem inherent in the liquid crystal material, for example, the response speed is slow and its inside is easy to overheat. In addition, the maximum light efficiency of existing transmission optical modulators is limited to a range of 1-2% and requires dark room conditions to provide acceptable display quality. Therefore, optical modulators such as DMD and AMA have been developed to solve the above problems.

Although DMD shows a relatively good light efficiency of about 5%, the hinge structure employed in the DMD not only causes serious fatigue problems, but also requires a very complicated and expensive driving circuit.

The AMA reflects the light incident from the light source at a predetermined angle, and each mirror installed therein adjusts the luminous flux so that the reflected light is projected on the screen through an opening such as a slit or pinhole to form an image. Device. Therefore, its structure and operation principle are simple, and high light efficiency (more than 10% light efficiency) can be obtained compared to LCD or DMD. In addition, the contrast of the image projected on the screen is improved to obtain a brighter and clearer image.

Each actuator of the TMA generates a deformation in accordance with the electric field generated by the applied electric image signal and the bias signal. As the actuator deforms, each of the mirrors mounted thereon is tilted. Therefore, the inclined mirrors reflect the light incident from the light source at a predetermined angle to form an image on the screen. As an actuator for driving the respective mirrors, a piezoelectric material such as PZT (Pb (Zr, Ti) O ₃ ), or PLZT ((Pb, La) (Zr, Ti) O ₃ ) is used. It is also possible to configure the actuator as electrostrictive material such as PMN (Pb (Mg, Nb) O 3).

These AMAs are classified into bulk and thin film types. Bulk AMA is disclosed in US Pat. No. 5,085,497 to Gregory Um et al. The bulk AMA is made by thinly cutting a multilayer ceramic to mount a ceramic wafer having a metal electrode formed therein in an active matrix in which a transistor is built, and then processing by a sawing method and installing a mirror on the top. However, bulk AMA requires very high precision in design and manufacture, and has a disadvantage of slow response of the strained layer. Accordingly, recently, a thin film type AMA (TMA) that can be manufactured using a semiconductor manufacturing process has been developed. For example, such a TMA is disclosed in Korean Patent Application No. 95-13353 (name of the invention: a method for manufacturing an optical path control device) filed by the applicant with the Korean Patent Office.

TMA is a reflective optical modulator using a thin film piezoelectric actuator in connection with microscopic mirrors, and has been developed to have uniformity of large scale integration over more than 300,000 pixels of a single plate mirror. This TMA consists of panels of 640x480 pixels representing red (R), green (G), and blue (B), respectively. The pixels are designed as cantilever structures to maximize the surface area of the mirror to increase light efficiency. The cantilever structure includes an active matrix to which an image signal voltage is applied and a mirror operated by the applied signal voltage.

A conventional projection type image display apparatus using a single plate type TMA as an optical modulator is shown in FIG.

Referring to FIG. 1, a conventional projection type image display apparatus 10 includes a halogen metal lamp 11 of 170 W to 270 W for emitting light rays, a reflector 19 for reflecting light rays from the lamp 11, and a lamp 11. Source lens 12 for making the light rays emitted from the light into parallel light, a source stop 13 having an opening for passing the light rays, and a light source passing through the source stop 13 for determining an amount of light rays forming an image. A source lens 14 for reflecting the light, a field lens 16 for correspondingly matching the image of the source stop 13 to the projection stop 20, and a plurality of mirrors and irradiated from the field lens 16. The TMA panel 18 for modulating the intensity of the light rays to be made, the projection stop 20 having an opening for passing the light rays and focusing the flux of the modulated light rays, and the light rays passing through the projection stop 20 are screened ( Degree And a projection lens 22 for projection on a not).

The operation principle of the conventional projection image display apparatus 10 will be briefly described as follows.

First, the light rays emitted from the lamp 11 are condensed into parallel light by the source lens 12 and then irradiated to the source mirror 14 through the opening of the source stop 13. The light rays reflected from the source mirror 14 are irradiated onto the TMA panel 18 with parallel light through the field lens 16 after its path is primarily changed.

The TMA panel 18 is composed of mirrors for reflecting the irradiated light rays and actuators for deforming the mirror according to a signal applied and formed under each mirror. 2 is a cross-sectional view showing the structure of the unit actuator of the TMA panel 18. As shown in FIG.

Referring to FIG. 2, each unit actuator 30 includes a membrane 10, a lower electrode 15 stacked on the membrane 10, a strain layer 20 stacked on the lower electrode 15, And an upper electrode 25 stacked on the strain layer 20.

The upper electrode 25 is applied with a ground voltage (0V) as a common electrode, and the lower electrode 15 is used as a signal electrode. When an image signal voltage of 0 to 10 V is applied to the lower electrode 15, the strain layer 20 formed between the upper electrode 25 and the lower electrode 15 causes deformation, and thus includes the strain layer 20. The actuator 30 to be tilted upwards. Therefore, the upper electrode 25 on the actuator 30 is also tilted in the same direction. Light rays incident from the light source are reflected by the upper electrode 25 bent at a predetermined angle, and then projected onto a screen to form an image.

If an OFF state, i.e., a zero voltage is applied to a specific actuator of the TMA panel 18, the mirror corresponding thereto is not tilted so that the light beam reflected from the projection stop 20 is shown in FIG. You get out of it and win a prize. Thus, a black image is displayed on the screen.

If the maximum signal is applied to a specific actuator of the TMA panel 18, the mirror corresponding thereto is fully tilted upwards and all the rays reflected therefrom pass through the opening of the projection stop 20 as shown in FIG. The white image is displayed by being projected on the screen.

According to the conventional projection type image display device described above, since the unit actuator of the TMA panel is driven only in the upward direction, mechanical stress is accumulated and the actuator does not realize a perfect OFF state when the zero voltage is applied, resulting in an afterimage on the screen. This problem occurs.

Accordingly, it is an object of the present invention to provide a projection type image display apparatus which can prevent afterimages from appearing on a screen in a projection type image display apparatus including a TMA panel.

1 is a schematic diagram of a conventional projection type image display apparatus.

FIG. 2 is a cross-sectional view showing the structure of a unit actuator in the thin film mirror array panel shown in FIG. 1.

3 is a plan view of the projection stop shown in FIG. 1.

4 is a schematic diagram of a projection image display apparatus according to the present invention.

FIG. 5 is a cross-sectional view showing the structure of a unit actuator in the thin film mirror array panel shown in FIG. 4.

6 is a plan view of the projection stop shown in FIG.

<Explanation of symbols for main parts of drawing>

100: projection image display device 101: reflector

102: light source 104: source lens

106: source stop 108: source mirror

110: field lens 112: TMA panel

114: projection stop 116: projection lens

200: lower electrode 205: lower strained layer

210: common electrode 215: upper strained layer

220: upper electrode 225: actuator

In order to achieve the above object, the present invention provides a pixel array consisting of a light source for emitting light rays, a mirror for reflecting light rays, and an actuator formed at a lower portion of the mirror and an actuator for modifying the mirror according to an applied signal. On the screen, a TMA panel in which the actuator is alternately driven up and down for a signal, a projection stop for concentrating the flux of the rays reflected from each mirror of the TMA panel, and the rays passing through the projection stop on the screen. Provided is a projection image display device having a projection lens for projecting.

According to the present invention, the actuator of the TMA panel is a lower electrode to which the first signal is applied, a lower strain layer stacked on top of the lower electrode, a common electrode stacked on top of the lower strain layer, and a top strain stacked on top of the common electrode. The upper electrode stacked on the layer and the upper strained layer and configured to have an upper electrode to which the second signal is applied is alternately driven one by one in the frame direction by the frame method.

The projection stop is formed to have two openings symmetrically at the center thereof, so that, for example, the actuator is projected onto the screen through the opening on the left side when the actuator is driven upward, and on the right side when the actuator is driven downward. To be projected onto the screen through the aperture.

Therefore, according to the present invention, by driving the unit actuator of the TMA panel in the up-and-down direction with respect to one signal, the physical stress of the actuator can be alleviated and the afterimage can be prevented from appearing on the screen.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 4 is a schematic diagram showing a projection type image display apparatus including a single plate type TMA according to the present invention, illustrating a single plate type single color system.

Referring to FIG. 4, the projection image display apparatus 100 according to the present invention includes a reflector 101, a light source 102, a source lens 104, a source stop 106, a source mirror 108, and a field lens 110. ), TMA panel 112, projection stop 114 and projection lens 116.

The light source 102 for emitting light rays is preferably a halogen metal lamp of about 170 W to 270 W, which emits long wavelength infrared (LWIR) to ultraviolet (UV) light in the spectrum. The reflector 101 serves to reflect the light rays emitted from the light source 102 in the opposite direction to the source lens 104 to be directed back to the source lens 104.

The source lens 104 serves to condense the light rays emitted from the light source 102 into parallel light. The source stop 106 is an optically opaque member and has an opening formed to pass light rays. Preferably this opening is a pinhole or slit. The source stop 106 determines the amount of light rays that form the image. The source mirror 108 serves to reflect the light rays passing through the source stop 106 so that its path is directed to the TMA panel 112.

The field lens 110 directs each ray passing through the source stop 106 to the TMA panel 112 without light loss, so that the image of the source stop 106 corresponds to the projection stop 114 1: 1. Investigate.

The TMA panel 112 includes a plurality of mirrors for reflecting the irradiated rays, each of which modulates the intensity of the rays in accordance with an electrical signal applied to an actuator provided thereunder. That is, each mirror is deformed to a deformation size corresponding to the intensity of the corresponding one pixel among the plurality of pixels displayed on the screen. The structure of the unit actuator of the TMA panel 112 according to the present invention is shown in FIG. 5.

Referring to FIG. 5, the unit actuator 225 of the TMA panel 112 according to the present invention includes a lower electrode 200 to which a first signal is applied, and a lower strain layer 205 stacked on the lower electrode 200. , The common electrode 210 stacked on the lower strain layer 205, the upper strain layer 215 stacked on the upper portion of the common electrode 210, and the second strain signal stacked on the upper strain layer 215. The upper electrode 220 is applied. When a signal voltage of about 10 V is applied to the upper electrode 220 and 0 V is applied to the common electrode 210 and the lower electrode 200, the lower strained layer 205 serves as a membrane in the conventional TMA panel and the upper electrode As the upper strained layer 215 formed between the 220 and the common electrode 210 causes deformation, the actuator 225 is tilted upward. On the other hand, when a signal voltage of about 10V is applied to the lower electrode 200 and 0V is applied to the common electrode 210 and the upper electrode 220, the upper strained layer 215 serves as a membrane in the conventional TMA panel. The actuator 225 is tilted downward while the lower deformation layer 205 formed between the lower electrode 200 and the common electrode 210 causes deformation.

Projection stop 114 is an optically opaque member and has an optically reflective surface and openings such as pinholes or slits formed to pass light rays. According to the present invention, the projection stop 114 has two openings A and B symmetrically from the center as shown in FIG. 6 so as to correspond to the light beams modulated by the actuators which are alternately driven upwards or downwards. To form. For example, when the actuator 225 of the TMA panel 112 drives in the upward direction, the light beam reflected from the mirror corresponding thereto is projected on the screen (not shown) through the opening of A, and the actuator 225 When driving in the downward direction, the light beam reflected from the mirror corresponding thereto is projected on the screen through the opening of B. Here, the flux of light rays passing through the openings A and B of the projection stop 114 controls the intensity of the light rays reflected from each mirror of the TMA panel 112.

The projection lens 116 functions to project light rays passing through the opening of the projection stop 114 onto the screen and display an image corresponding thereto.

The operation principle of the projection image display apparatus 100 according to the present invention having the above-described structure will be described in more detail as follows.

First, light rays emitted from a light source 102 made of an arc lamp, such as a halogen metal lamp, are condensed into parallel light by the source lens 104 and then irradiated to the source mirror 108 through the source stop 106. . The light rays reflected from the source mirror 108 are irradiated to the TMA panel 112 with parallel light through the field lens 110 after its path is primarily changed.

Each mirror of the TMA panel 112 modulates light rays in accordance with a signal applied to an actuator 225 provided thereunder. Preferably, the actuators 225 of the TMA panel 112 are driven in a frame manner. For example, when a white image is to be displayed, a white signal to be applied to the actuators 225 of the TMA panel 112 is stored in a predetermined buffer unit, and the signals are simultaneously turned on at any moment. In this case, data of one frame (that is, a white image) corresponding to one screen is simultaneously displayed on the screen. At this time, the unit actuator 225 of the TMA panel 112 is alternately driven in the up and down directions for each frame.

If an OFF voltage, i.e., zero voltage, is applied to a particular actuator, the mirror corresponding to the actuator is not tilted, and thus the light rays reflected therefrom are projected stops 114 as shown in FIG. Phase is formed between both openings (A, B). Therefore, the black image is displayed on the screen because it does not pass through the projection stop 114.

If an ON voltage, for example, an all-back signal voltage, is applied to a specific actuator of the TMA panel 112, a signal voltage of 10 V is applied to the upper electrode 220 in the first frame, and the common electrode 210 and the lower electrode are applied. 0V is applied to the 200 to drive the actuator 225 in the upward direction. Accordingly, the mirror corresponding to the actuator 225 is tilted upward and the rays reflected therefrom pass through the A opening of the projection stop 114 as shown in FIG. 6 and then on the screen by the projection lens 116. Is projected on.

Subsequently, in the second frame, a signal voltage of about 10 V is applied to the lower electrode 200 and 0 V is applied to the common electrode 210 and the upper electrode 220 to drive the actuator 225 downward. Accordingly, the mirror corresponding to the actuator 225 is tilted downward and the rays reflected therefrom pass through the B opening of the projection stop 114 as shown in FIG. 6 and then on the screen by the projection lens 116. Is projected on.

Here, FIG. 4 illustrates a monochromatic system using a single plate TMA, but according to another preferred embodiment of the present invention, red is sequentially red using a color wheel consisting of a series of color segments of red, green and blue transmission filters. The present invention can be applied to a single plate color system capable of displaying red, green and blue images by irradiating green and blue light to the single plate TMA.

In addition, according to another preferred embodiment of the present invention, the present invention can be applied to a multi-plate color system using a 3-plate TMA.

As described above, according to the projection type image display apparatus, the unit actuator of the TMA panel is alternately driven in the up and down directions with respect to one signal to alleviate the physical stress of the actuator to prevent afterimages from appearing on the screen. can do.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand that you can.

Claims (4)

A light source 102 for emitting light rays; Pixels composed of a mirror for reflecting light rays and an actuator 225 for deforming the mirror according to a signal formed and applied to the bottom of the mirror are arranged in a matrix form, and the actuator 225 is provided with respect to one signal. A thin film mirror array (TMA) panel 112 which is alternately driven in an upward direction and a downward direction; A projection stop 114 for concentrating the flux of light rays reflected from each mirror of the TMA panel 112; And And a projection lens (116) for projecting light rays passing through the projection stop (114) onto a screen. The projection type image display apparatus according to claim 1, wherein the projection stop (114) is formed to have two openings (A, B) symmetrically at a center thereof. The actuator 225 of the TMA panel 112 includes a lower electrode 200 to which a first signal is applied, a lower strain layer 205 stacked on an upper portion of the lower electrode 200, and a lower portion of the actuator 225. The common electrode 210 stacked on the strained layer 205, the upper strained layer 215 stacked on the upper portion of the common electrode 210, and the upper strained layer 215 stacked on top of the second signal Projection type image display device, characterized in that consisting of the upper electrode 220 is applied. The method of claim 3, wherein the actuator 225 of the TMA panel 12 is applied by the first and the second signal by a frame method, it is driven alternately in the up and down direction by one frame. Projection type image display device.