KR20000044179A - Projection type video display unit including thin-film micromirror array-actuated panel - Google Patents

Abstract

PURPOSE: A projection type video display unit including a thin-film micromirror array-actuated panel is provided to realize a high contrast by removing a ghost image. CONSTITUTION: A projection type video display unit including a thin-film micromirror array-actuated panel comprises a light source(102), a thin film type mirror array panel(112), an optical pipe(103), a source lens(104), a source stop(106), a field lens(110), a projection stop(114), and a projection lens(116). The thin film type mirror array panel is composed of pixels of a mirror for reflecting a light beam. The optical pipe uniforms the light beam emitted form the light source. The source lens focuses the light beam penetrating the optical pipe. The source stop focuses flux of the light beam penetrating the source lens. The field lens irradiates the light beam penetrating the source stop to a TMA(Thin-film Micromirror Array-actuated) panel. The projection stop focuses flux of the light beam reflected from each mirror of the TMA panel. The projection lens projects the light beam penetrating the projection stop on a screen.

Description

Projection type image display device including thin film mirror array panel

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection image display device, and more particularly, to removing ghost images in 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 type image display device capable of realizing high contrast and facilitating alignment and assembly of an optical system.

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 transmit light modulators, while DMD and AMA can be classified as reflected 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 the 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 AMA generates a deformation in accordance with the electric field generated by the applied electric image signal and the bias voltage. 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 thin film piezoelectric actuators 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 including a single plate type TMA 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. Project images of the source stop 13, the source stop 13, which has an aperture for passing the light rays, and the source stop 13, which determines the amount of light rays forming an image. A field lens 16 for 1: 1 correspondence to the stop 20, a TMA panel 18 having a plurality of mirrors and for modulating the intensity of the rays irradiated from the field lens 16, for passing the rays A projection stop 20 having an aperture and concentrating the flux of modulated light rays, and a projection lens 22 for projecting the light rays passing through the projection stop 20 onto a screen (not shown).

Hereinafter, the operation principle of the conventional projection type image display apparatus 10 will be described briefly.

First, the light rays emitted from the halogen metal lamp 11 are made into parallel light by the source lens 12 and then enter the field lens 16 through the opening of the source stop 13. Light rays made into parallel light by the field lens 16 are irradiated onto the TMA panel 18. Each mirror of the TMA panel 18 vibrates, tilts or bends in accordance with an image signal voltage applied to an actuator provided thereunder. Accordingly, the light rays passing through the field lens 16 are reflected from the respective mirrors of the TMA panel 18 and then projected on the screen through the projection lens 22 through the opening of the projection stop 20 so as to display an image. Form. At this time, the path of the light rays reflected from the mirror of the TMA panel 18 determines the intensity of the light rays passing through the opening of the projection stop 20. That is, the flux of light rays passing through the opening of the projection stop 20 is controlled by the direction of the mirror of the TMA panel 18 with respect to the projection stop 20.

In Fig. 1, reference numeral P1 denotes a light beam irradiated to the TMA panel 18, P2 denotes an untilted light beam, and P3 denotes a tilted light beam.

According to the conventional projection type image display apparatus 10 described above, in the process of irradiating the light emitted from the lamp 11 onto the TMA panel 18 through the field lens 16, a part of the field lens 16 Is reflected from each side of the. That is, the field lens 16 is composed of a first surface 16a, a second surface 16b, and a third surface 16c. The light reflected from each surface above the optical axis causes the projection stop 20 to fall. Although not passing through, the light rays reflected from each side below the optical axis pass through the projection stop 20 to form a ghost image symmetrically concentrated left and right of the center on the screen.

Typically, the illuminance difference between the background and the ghost pattern is 6-7: 1 on the screen, and the lower the brightness of the background, the more ghost image is clearly detected. In particular, when a zero voltage is applied to the TMA panel so that the screen becomes dark, this ghost image is clearly seen. Since ghost always acts as noise and degrades image quality, such ghost must be removed in order to realize a reliable optical system.

Accordingly, a projection image display apparatus capable of removing ghost images has been proposed, and a schematic structure thereof is shown in FIG.

Referring to FIG. 2, the TMA panel 58 is disposed on the lower surface of the optical axis of the field lens 56, and the light source 51 and the source are about an optical axis connecting the center of the source stop 53 and the center of the field lens 56. By tilting the normal vector of the lens 52 by the angle of θ, the light rays emitted from the light source 51 were uniformly irradiated onto the front surface of the TMA panel 58.

However, according to the conventional projection type image display apparatus described above, alignment and assembly of the optical system are not only difficult because of tilting the light source and the source lens, but also a problem arises in holding the fixing part of the optical system.

Accordingly, an object of the present invention is to provide a projection type image display apparatus that can achieve high contrast and facilitate alignment and assembly of an optical system in a projection type image display apparatus including a TMA panel.

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

2 is a schematic diagram showing another conventional projection image display apparatus.

3 is a schematic diagram showing a projection image display apparatus according to the present invention.

4 is a schematic diagram showing an incidence portion in the apparatus of FIG. 3.

<Description of the symbols for the main parts of the drawings>

100: projection image display device 101: reflector

102: light source 103: light pipe

104: source lens 106: source stop

110: field lens 112: TMA panel

114: projection stop 116: projection lens

The present invention to achieve the above object, the light source for emitting light rays; TMA panel consisting of pixels of a mirror for reflecting light rays, each mirror being transformed to a deformation size corresponding to the intensity of a corresponding one of a plurality of pixels displayed on the screen, the same optical axis as the optical axis of the light source An optical pipe disposed on the optical axis for uniformizing the light rays emitted from the light source, a source lens disposed downward by a distance of Δ from the optical axis of the light source, for collecting the light beam passing through the optical pipe, and the same optical axis as the optical axis of the source lens A source stop for concentrating the flux of light rays passing through the source lens, a field lens for irradiating the TMA panel with parallel light on the light beam passing through the source stop, and a TMA panel Projection stop, and projection to focus the flux of rays reflected from each mirror Provided is a projection image display device having a projection lens for projecting light rays passing through a stop onto a screen.

According to the present invention, the light source and the light pipe are arranged on the same optical axis and the source lens, the source stop and the field lens are arranged on the same optical axis down by a distance of Δ from the optical axis of the light source. That is, the optical axis of the light source and the optical axis of the source lens are disposed to be offset so that the emission surface of the light pipe is formed on the TMA panel through the source lens and the field lens. Therefore, since the light source and the source lens are not tilted, alignment and assembly of the optical system can be easily performed, and the fixing portion of the optical system can be easily supported. In addition, by placing the TMA panel on the lower surface of the optical axis of the field lens, the ghost image can be removed to achieve high contrast.

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

Fig. 3 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. 4 is a schematic diagram showing an incidence portion in the projection image device of the present invention.

3 and 4, the projection image display apparatus 100 according to the present invention includes a reflector 101, a light source 102, a light pipe 103, a source lens 104, a source stop 106, 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 kW class halogen metal lamp that emits long wavelength infrared (LWIR) to ultraviolet (UV) light in the spectrum. In order to improve the brightness of the screen, it is necessary to generate pixels by generating light rays having a large amount of light, so use a lamp of high power as much as possible. 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 light pipe 103 is disposed on the same optical axis as the optical axis of the light source 102, and serves to mix the light rays emitted from the light source 102 with the source lens 104. Light pipes are light transmission elements that use unfocused transmission or reflection to reduce light loss and are used to distribute light more evenly. Specifically, the light pipe may be used to pre-cut the loss of the circular beam to prevent the loss of part of the circular beam when the circular beam emitted from the lamp passes through the optical component, such as a stop or lens. It acts as a scrambler to redistribute the angular distribution of light using the total reflection surface, and to reduce the color shift caused by the reflector located at the rear of the lamp.

The source lens 104 collects the light rays passing through the light pipe 103 and sends the light to the source stop 106. The source lens 104 moves downward from the optical axis connecting the center of the light source to the center of the light pipe 103. To place.

The source stop 106 is an optically opaque member and has an opening, such as a pinhole or slit, configured to pass light rays. The source stop 106 determines the amount of light rays that form the image. Preferably, the source stop 106 is disposed on the same optical axis as the optical axis of the source lens 104.

To ensure that the image of the source stop 106 corresponds 1: 1 to the projection stop 114, the field lens 110 uses the TMA panel (parallel light) to convert each of the rays passing through the source stop 106 into parallel light without light loss. 112). Preferably, the field lens 110 is disposed on the same optical axis as the optical axes of the source lens 104 and the source stop 106. Thus, the exit surface A of the light pipe 103 is imaged on the TMA panel 112 through the source lens 104 and the field lens 110.

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 projection stop 114 is an optically opaque member and has an optically reflective surface and an opening formed to pass light rays. Preferably, this opening is a pinhole or slit. The flux of light rays passing through the opening 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 on a screen (not shown) to 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 properly mixed while passing through the light pipe 103 to make the intensity uniform, and then irradiated to the source lens 104. The rays collected by the source lens 104 pass through the source stop 106 and are then irradiated to the TMA panel 112 with parallel light by the field lens 110.

Each mirror of the TMA panel 112 modulates light rays in accordance with a signal applied to an actuator provided thereunder. If an OFF voltage, i.e. a zero voltage, is applied to a particular actuator, the mirror corresponding to that actuator is not tilted so that the beams irradiated to the mirror do not pass through the projection stop 114. do.

However, when an ON voltage is applied to a particular actuator, the mirror corresponding to the actuator is tilted and thus the light rays irradiated on the mirror are modulated in intensity and directed through the field lens 110 to the projection stop 114. . At this time, the path of the light beam reflected from the mirror determines the intensity of the light beam passing through the opening of the projection stop 114. That is, the flux of the light rays passing through the opening of the projection stop 114 is controlled by the direction of the mirror of the TMA panel 112 relative to the projection stop 114.

As such, the light rays passing through the opening of the projection stop 114 are projected on the screen by the projection lens 116 to display an image corresponding thereto.

Here, FIG. 2 illustrates a monochromatic system using a single-plate TMA, but according to another preferred embodiment of the present invention, red, green and blue transmission filters are sequentially red, using a color wheel consisting of a series of color fragments. 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 a 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 of the present invention, the light source and the light pipe are disposed on the same optical axis, and the source lens, the source stop, and the field lens are disposed on the same optical axis down by a distance Δ from the optical axis of the light source. . That is, the optical axis of the light source and the optical axis of the source lens are disposed to be offset so that the emission surface of the light pipe is formed on the TMA panel through the source lens and the field lens. Therefore, since the light source and the source lens are not tilted, alignment and assembly of the optical system can be easily performed, and the fixing portion of the optical system can be easily supported. In addition, by placing the TMA panel on the lower surface of the optical axis of the field lens, the ghost image can be removed to achieve high contrast.

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 (2)

A light source 102 for emitting light rays; A thin-film mirror array (TMA) panel 112 composed of pixels of a mirror for reflecting light rays, each mirror being deformed to a deformation size corresponding to the intensity of a corresponding one of a plurality of pixels displayed on the screen. ); An optical pipe (103) disposed on the same optical axis as the optical axis of the light source (102) for uniforming the light rays emitted from the light source (102); A source lens 104 disposed downward by a distance Δ from an optical axis of the light source 102 for condensing light rays passing through the light pipe 103; A source stop (106) disposed on the same optical axis as the optical axis of the source lens (104), for concentrating the flux of light rays passing through the source lens (104); A field lens (110) disposed on the same optical axis as the optical axis of the source lens (104), for irradiating the TMA panel (112) with the light passing through the source stop (106) as parallel light; 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 image display device according to claim 1, wherein the TMA panel (112) is disposed on an under surface of the optical axis of the field lens (110).