KR19980040062A - Optical Projection System Using Actuated Mirror Array - Google Patents

Abstract

An optical projection system using an actuated mirror array (AMA) light modulator is disclosed. An optical projection system focuses on a light source for generating light beams, a source stop that concentrates the flux of the light beams, determines a quantity of light beams forming an image, and modulates the intensity of the light beams passing through the source stops to project onto the screen. An AMA light modulator, and a projection stop for concentrating the flux of light modulated by the AMA light modulator, the magnitude being greater than the source stop. Since the projection stop is designed to be larger than the source stop, the image of the source stop can pass through the projection stop without light loss to achieve a high brightness screen.

Description

Optical Projection System Using Actuated Mirror Array

The present invention relates to an optical projection system, and more particularly, to an optical projection system capable of improving brightness on a screen in an optical projection system using an actuated mirror array as an optical modulator.

In general, spatial light modulators, which are devices for projecting optical energy onto a screen, can be applied to various fields such as optical communication, image processing, and information display devices. Typically, such devices are classified into a direct-view 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). The CRT device is called a CRT, which has excellent image quality but increases in weight and volume as the screen is enlarged, leading to an increase in manufacturing cost. There is.

Projection type image display apparatuses include liquid crystal displays (hereinafter referred to as LCDs), deformable mirror devices (hereinafter referred to as DMDs), and activated mirror arrays (hereinafter referred to as AMAs). And the like). Such projection image display devices can be further divided into two groups according to their optical characteristics. That is, devices such as LCDs can be classified as Transmissive spatial light modulators, while DMD and AMA can be classified as Reflective spatial 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, due to the polarity of the light, the light efficiency is low, there is a problem inherent in the liquid crystal material, for example, there is a disadvantage that the response speed is slow and the inside is easy to overheat. In addition, the maximum light efficiency of existing transmission light modulators is limited to a range of 1-2% and requires dark room conditions to provide acceptable display quality.

Optical modulators such as DMD and AMA have been developed to solve the problems of the aforementioned LCD type optical modulators. DMD shows a relatively good light efficiency of about 5%, but serious fatigue problems are caused by the hinge structure employed in the DMD. In addition, there is a disadvantage that a very complicated and expensive driving circuit is required.

In contrast, AMA is a piezoelectrically driven mirror array that provides light efficiency of 10% or more. In an AMA light modulator, each actuator causes a deformation in accordance with the electric field generated by the applied electrical image signal and the bias voltage. When the actuator causes deformation, each of the mirrors mounted on top of the actuator is tilted. Accordingly, the inclined mirrors can reflect light incident from the light source at a predetermined angle. The AMA optical modulator has a simple structure and operation principle, and can obtain high light efficiency compared to LCD or DMD. It also provides sufficient contrast to provide a bright and clear image under normal room temperature light conditions. Moreover, it is not only affected by the polarity of the incident light, but also does not affect the polarity of the reflected light. In addition, the reflective properties of the AMA are relatively less sensitive to temperature, which has the advantage of improving the brightness of the screen compared to other devices that are easily affected by high power light sources.

These AMA devices are largely divided into bulk type and thin film type. The bulk AMA requires actuators to be separated by a sawing method, so that high precision is required in design and manufacturing, and the response speed of the deformable part is slow. Therefore, recently, the thin film type AMA (henceforth called TFAMA) which can be manufactured using a semiconductor manufacturing process is mainly used. For example, such a TFAMA 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.

TFAMA is manufactured using thin film processes that are well known in the semiconductor industry. TFAMA was developed to transmit enough light on the screen to display digital images in high brightness and high contrast under normal room lighting conditions. TFAMA is a reflective optical modulator using thin film piezo-electric actuators in connection with microscopic mirrors of 100μ-100μ size. TFAMA has been developed to achieve even integration of large scales, combined with improved tilt angles for high contrast, sufficient light efficiency for high brightness, and 300,000 pixels of mirrors in a single panel. TFAMA consists of panels of 640x480 pixels representing red, green and blue, respectively. The size of individual pixels of the TFAMA is, for example, 100 μm × 100 μm. The size of these pixels can be easily reduced to 50μm x 50μm to satisfy the resolution required for high-definition TV. Generally, 640 x 480 pixels are assembled on a 4-inch silicon wafer to make a single TFAMA module. Multiple TFAMA modules can be assembled on 6 inch or 8 inch wafers down to the mirror pixel size needed for good productivity and low production costs. The pixels are designed as cantilever structures to maximize the mirror surface area to increase light efficiency.

1 is a plan view of the TFAMA device described in the Applicant's prior application.

As shown in FIG. 1, the TFAMA device is composed of an active matrix 1 and an actuator 2 having a cantilever structure provided on the active matrix 1. The active matrix 1 is made of a semiconductor such as silicon (Si), and includes M x N (M, N is an integer) MOS transistors (not shown). The actuator 2 is composed of a membrane layer, a lower electrode for a signal electrode, a piezoelectric layer, and an upper electrode which serves as a mirror reflecting a light beam incident on a part thereof. The actuator 2 has a rectangular concave portion formed at one side with a central portion thereof, and a rectangular protrusion formed at the other side corresponding to the concave portion. The protrusion of the actuator adjacent to the concave portion of the actuator 2 is fitted, and the protrusion of the actuator 2 is fitted into the concave portion of the adjacent actuator.

A conventional optical projection system using a TFAMA light modulator having the above-described structure is shown in FIG.

Referring to FIG. 2, a conventional AMA projection system 10 includes 170W to 250W of a metal halide lamp 11, a reflector 15, a source lens 12, A source stop 13, a source mirror 14, a modulation lens 16, an AMA light modulator 18, a projection stop 20, and a projection lens 22.

The operation principle of the conventional AMA projection system 10 will be briefly described as follows.

First, when the AMA projection system 10 is driven, the light rays emitted from the halogen metal lamp 11 are reflected by the reflector 15 and then the opening of the source stop 13 into parallel light by the source lens 12. It passes through and is irradiated on the source mirror 14. The light rays reflected from the source mirror 14 are incident on the modulation lens 15 after the path is changed primarily. The modulation lens 15 uses the AMA light modulator 18 as a parallel light beam of light passing through the source stop 13 so that the image of the source stop 13 corresponds 1: 1 to the projection stop 20. Investigate the phase. The mirror of the AMA light modulator 18 is actuated and irradiated onto the projection stop 20 in accordance with an electrical signal applied to the piezoelectric actuator provided thereunder. Light rays that pass through the opening of the projection stop 20 are projected onto the screen through the projection lens 22 to form an image. 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 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 AMA light modulator 18 with respect to the projection stop 20.

3A and 3B are schematic diagrams for explaining a relationship between an image of a source stop and a projection stop when no voltage is applied and when a voltage is applied.

Referring to FIG. 3A, when no voltage is applied to the AMA light modulator 18 (ie, when the voltage is OFF), the tilting angle of each mirror of the AMA light modulator 18 is zero (0 °). do. As a result, the image 13a of the source stop irradiated with the AMA light modulator 18 is taken out of the projection stop 20 as it is and forms an image. At this time, since the source stop 13 and the projection stop 20 are formed in the same size, the image stop 13a of the source stop corresponds to the projection stop 20 in a 1: 1 ratio.

Referring to FIG. 3B, when a voltage is applied to the AMA light modulator 18, the mirror of the AMA light modulator 18 is inclined. As a result, the light rays irradiated on the AMA light modulator 18 are reflected by the mirror and aimed to pass through the opening of the projection stop 20. At this time, since the AMA light modulator having the structure as shown in FIG. 1 uses only a part of the upper electrode as a mirror (part A of FIG. 1), the image stop 13a of the modulated source stop spreads vertically and horizontally. . Since the source stop 13 and the projection stop 20 are formed with the same size, the image stop 13a of the source stop is larger than the projection stop 20. Accordingly, light loss (see hatched portion in FIG. 3B) corresponding to the difference between the projection stop 20 and the source stop image 13a occurs, resulting in a problem that the brightness on the screen is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide an optical projection system using an AMA light modulator capable of improving luminance on a screen.

1 is a plan view of the thin film actuated mirror array device described in the prior art of the applicant.

2 is a schematic diagram illustrating a conventional actuated mirror array projection system.

3A and 3B are schematic diagrams for explaining a relationship between an image of a source stop and a projection stop in the projection system of FIG. 2 when no voltage is applied and when a voltage is applied.

4 is a schematic diagram illustrating an activated mirror array projection system according to an embodiment of the present invention.

5 is a schematic diagram illustrating a source stop and a projection stop used in the projection system of FIG. 4.

6A and 6B are schematic diagrams for explaining a relationship between an image of a source stop and a projection stop when no voltage is applied and when voltage is applied in the projection system of FIG. 4.

Explanation of symbols for main parts of the drawings

10,100 ... AMA projection system 11,111 ... lamp

12,112 ... source lens 13,113 ... source stop

14,114 ... source mirror 15,115 ... reflector

16,116 ... modulation lens 18,118 ... AMA optical modulator

20,120 ... projection stop 22,122 ... projection lens

The present invention to achieve the above object,

A light source for generating light rays;

A source stop that concentrates the flux of the light rays and determines an amount of light rays forming an image;

An AMA light modulator for modulating and projecting the intensity of light rays passing through the source stop on a screen; And

An optical projection system having a larger size than the source stop and having a projection stop for focusing the flux of light modulated by the AMA light modulator.

As described above, the present invention designs the sizes of the source and projection stops differently. That is, the projection stop is made larger than the source stop so that the image of the reflected source stop is passed through the projection stop without light loss while spreading up and down and left and right by the mirror of the AMA light modulator.

Therefore, according to the optical projection system of the present invention, since the image of the source stop passes through the projection stop without light loss, the amount of light reaching the screen is increased, thereby realizing a screen having high luminance.

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

4 is a schematic diagram illustrating an optical projection system using an AMA light modulator according to an embodiment of the present invention.

Referring to FIG. 4, the AMA projection system 100 according to the present invention includes a lamp 111 for emitting light, a source lens 112, a source stop 113, a source mirror 114, a reflector 115, Modulation lens 116, AMA light modulator 118, projection stop 120, and projection lens 122.

Lamp 111 for emitting light preferably emits long wavelength infrared (LWIR) to ultraviolet (UV) light in the spectrum as an arc lamp, such as a halogen metal lamp of 170W to 250W. The reflector 115 serves to reflect the light emitted from the lamp 111 in the opposite direction with respect to the source lens 112 to be directed back to the source lens 112.

The source lens 112 makes the light beam emitted from the lamp 111 into parallel light and irradiates the source stop 113. The source stop 113 is an optically opaque member and has an opening formed to allow light to pass therethrough. The source stop 113 determines the amount of light that forms the image.

The modulation lens 116 is configured so that the image of the source stop 113 corresponds to the projection stop 120 in a 1: 1 manner so that the light passing through the source stop 113 is not lost by the AMA light modulator 118. Investigate with

The AMA light modulator 118 includes a plurality of mirrors for reflecting the irradiated rays, which modulate the intensity of the rays in accordance with electrical signals applied to the piezoelectric actuators provided thereunder.

The projection stop 120 is an optically opaque member and has an optically reflective surface and an opening formed to pass a light beam. Preferably, the opening is a pinhole or slit. The projection lens 122 projects a ray passing through the opening of the projection stop 120 on a screen (not shown) to display a corresponding image.

Hereinafter, the operation principle of the AMA projection system 100 according to the present invention having the above-described structure will be described in more detail.

First, when driving the AMA projection system 100, the light rays emitted from the halogen metal lamp 111 are irradiated onto the source stop 113 as parallel light through the source lens 112. Light rays passing through the opening of the source stop 113 are irradiated to the AMA light modulator 118 by the modulation lens unit 116 as parallel light. The mirror of the AMA optical modulator 118 is actuated according to an electrical signal applied to the piezoelectric actuator provided thereunder and irradiated onto the projection stop 120. Light rays that pass through the opening of the projection stop 120 are projected onto the screen through the projection lens 122 to form an image. 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 120. That is, the flux of light rays passing through the opening of the projection stop 120 is controlled by the direction of the mirror of the AMA light modulator 118 relative to the projection stop 120.

Here, the source stop 113 and the projection stop 120 used in the AMA projection system 100 of the present invention are designed to be different in size as shown in FIG. That is, the projection stop 120 is designed to be larger than the source stop 113. The relationship between the image of the source stop 113 and the projection stop 120 designed as described above will be described with reference to FIGS. 6A and 6B.

Referring to FIG. 6A, when no voltage is applied to the AMA light modulator 118 (that is, when the voltage is OFF), the inclination angle of each mirror of the AMA light modulator 118 becomes zero (0 °). As a result, the image 113a of the source stop irradiated with the AMA light modulator 118 is taken out of the projection stop 120 as it is and forms an image. In this case, since the source stop 113 and the projection stop 120 are formed in different sizes, the image stop 113a of the source stop does not correspond 1: 1 to the projection stop 120.

Referring to FIG. 6B, when a voltage is applied to the AMA light modulator 118, the mirror of the AMA light modulator 118 vibrates, tilts, or bends. As a result, the light beam irradiated on the AMA light modulator 118 is reflected by the mirror and is aimed to pass through the opening of the projection stop 120. At this time, since the AMA optical modulator having the structure as shown in FIG. 1 uses only a part of the upper electrode as a mirror (part A of FIG. 1), the image 113a of the source stop being modulated is spread up and down and left and right. . However, in the present invention, since the projection stop 120 is designed to be larger than the source stop 113, the source stop image 113a passes through the projection stop 120 with little light loss.

Here, FIG. 4 illustrates a monochrome system using a single panel AMA light modulator, but according to another preferred embodiment of the present invention, red, green, and blue lights are sequentially applied to the single panel AMA light modulator. The invention can be applied to single-plate color systems that display color (R, G, B) images using devices such as color wheels for illumination.

Further, according to another preferred embodiment of the present invention, the present invention can be applied to a multi-plate color system that displays color images using a three-panel AMA light modulator.

As described above, the present invention designs the size of the source stop and the projection stop differently. That is, the projection stop is made larger than the source stop so that the image of the reflected source stop is passed through the projection stop without light loss while spreading up and down and left and right by the mirror of the AMA modulator.

Therefore, according to the optical projection system of the present invention, since the image of the source stop passes through the projection stop without light loss, the amount of light reaching the screen is increased, thereby realizing a screen having high luminance.

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

Claims (3)

A light source 111 for generating light rays; A source stop 113 for concentrating the flux of the light beams and for determining the amount of light beams forming an image; An actuated mirror array light modulator (118) for modulating and projecting the intensity of light rays passing through the source stop (113); And And a projection stop (120) having a size greater than the source stop (113) and for concentrating the flux of light modulated by the actuated mirror array light modulator (118). The light source of claim 1, wherein the light beam passing through the source stop 112 and the source stop 113 are converted into parallel light by turning the light beam generated from the light source 111 into the parallel light. And a modulation lens 116 for irradiating the actuated mirror array light modulator 118, and a projection lens for projecting light beams passing through the projection stop 120 onto the screen. Projection system. The active mirror array optical modulator 118 has an active matrix to which an image signal voltage is applied, and an actuator for receiving an image signal voltage from the active matrix, wherein the actuator is an active matrix. A membrane layer formed on the membrane layer and having a support thereon and providing stability to the actuator, a lower electrode formed on the membrane layer and functioning as a signal electrode, a piezoelectric layer formed on the lower electrode and deformable, and an optical energy Optical projection system, characterized in that consisting of the upper electrode reflecting.