KR100209955B1 - Optical system of an actuated mirror array and a projection method by using the same - Google Patents

Abstract

An actuated mirror array (AMA) optical system and a projection method using the same are disclosed. The optical system includes a light source for generating light rays and a source lens for condensing light rays generated from the light sources. The illumination uniformity improving member has a plurality of glass thin plates stacked on top of each other, and the light beam collected by the source lens allows each of the glass thin plates to pass through a uniform divergent angle. The source stop has an opening and concentrates the flux of the light beam with a uniform divergence angle. The AMA panel comprises a plurality of mirrors in which the light rays passing through the source stop are uniformly illuminated, each mirror being modified to correspond to the intensity of a corresponding one of the plurality of pixels displayed on the screen. The projection lens projects light rays reflected from each mirror of the AMA panel on the screen. Since the angle of light coming from the source stop is made uniform, the intensity of light at the center and periphery of the AMA panel is made uniform.

Description

Actuated mirror array optics and projection method using the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Actuated Mirror Array (hereinafter referred to as AMA) optical system and a projection method using the same, particularly in an optical system using an AMA panel used to project an image on a screen as an optical modulator. It relates to an optical system and a projection method using the same that can improve the intensity uniformity and angle uniformity of the light generated from the.

In general, a spatial light modulator, which is an apparatus for projecting optical energy onto a screen, may be applied to various fields such as optical communication, image processing, and information display apparatus. 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%, requiring 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 enough 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 that the brightness of the screen can be improved over other devices that are easily affected by high power light sources.

Such AMA devices are largely classified into bulk type devices and thin film type devices. The bulk AMA has a center electrode between two piezoelectric layers. The central electrode is connected to an active matrix having a conductive epoxy for the signal voltage. On top of the bulk AMA is a mirror layer, which has an inclination angle of +/- 0.25 ° under a voltage of up to 30V. For this reason, bulk AMA requires very high precision in design and manufacture, and there are many difficulties in assembling the structure.

Accordingly, recently, a thin film type AMA (hereinafter referred to as TFAMA) has been developed that can be manufactured using a semiconductor manufacturing process in order to complete the quality of mirror arrays. The TFAMA is disclosed in Korean Patent Application No. 95-13358, filed May 26, 1995 by the applicant.

TFAMA is a reflective light modulator that uses thin film piezo-electric actuators in conjunction with microscopic mirrors to provide uniformity of large scale integration across more than 300,000 pixels of a single-plate mirror. Has been developed. This TFAMA 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 mirror surface area to increase the 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 optical system using a single panel TFAMA as an optical modulator is shown in FIG.

Referring to FIG. 1, a conventional AMA optical system 10 includes a 170 ha to 250 w metal halide lamp 11 for emitting light, and a reflector for reflecting light from the lamp 11. (15), a source lens (12) for making the light beam emitted from the lamp (11) into parallel light, a source stop for determining the amount of light beam forming an image with an aperture for passing the light beam; (13), a source mirror (14) for reflecting light rays passing through the source stop (13), and a field lens (16) for one-to-one correspondence of the image of the source stop (13) to the projection stop (20). A projection panel having a plurality of mirrors and having an AMA panel 18 for modulating the intensity of the light beam irradiated from the field lens 16, an opening for passing the light beam, and concentrating the flux of the modulated light beam. Stop 20, and the projection And a top projection lens 22 for projecting a light beam passing through the 20 onto a screen (not shown).

The operation principle of the conventional AMA optical system 10 is briefly described as follows.

First, when the AMA optical system 10 is driven, light rays emitted from the halogen metal lamp 11 are condensed into parallel light by the source lens 12, and then pass through the opening of the source stop 13 to obtain a source mirror ( 14) is irradiated onto. The light rays reflected from the source mirror 14 are irradiated onto the AMA panel 18 with parallel light through the field lens 16 after the path is primarily changed.

Each mirror of the AMA panel 18 vibrates, tilts or bends in accordance with an image signal voltage applied to an actuator provided below it. Accordingly, light rays passing through the field lens 16 are reflected from the mirrors and then passed through the opening of the projection stop 20 to be projected on the screen through the projection lens 22 to form an image. At this time, the path of the light beam reflected from the mirror of the AMA panel 18 determines the intensity of the light beam passing through the opening of the projection stop 20. In other words, 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 panel 18 with respect to the projection stop 20.

In the conventional AMA optical system 10 as described above, when light emitted from the lamp 11 passes through the source stop 13 as shown in FIG. 2, it exits from the source stop 13. The angle of light is directed in a particular direction, ie the center of the AMA panel 18. As a result, the difference between the intensity of light reaching the center of the AMA panel 18 and the intensity of light reaching its periphery becomes large, so that the amount of light modulation occurs when each mirror of the AMA panel 18 is tilted. The problem of unevenness arises.

In addition, in the conventional AMA optical system, a halogen metal lamp 11 used as a light source is attached to the reflector 15 for reflecting light emitted in the opposite direction to the source lens 13 and directing the light toward the source lens 13. In this case, the lamp 11 must be accurately positioned at the focus of the reflector 15. However, since the halogen metal lamp 11 emits light by arc discharge between two metal electrodes as an arc lamp, it is difficult to accurately place it in the focus of the reflector 15. The brightness of the screen is deteriorated due to the influence on the fixed tolerance of the lamp. That is, a problem arises in that an uneven brightness of the entire screen is formed so that an unwanted pattern having an X shape that is relatively brighter than the surroundings is formed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and a first object of the present invention is an optical system using an AMA panel as an optical modulator, which can improve illumination uniformity of light generated from a light source. To provide.

It is a second object of the present invention to provide a projection method capable of making uniform illumination of light generated from a light source using the AMA optical system.

1 is a schematic diagram showing a conventional actuated mirror array optical system.

FIG. 2 is a front view of a source stop used in the optical system of FIG. 1. FIG.

3 is a schematic diagram showing an actuated mirror array optical system according to an embodiment of the present invention.

4 is an enlarged view of an illumination uniformity improving member in the optical system of FIG. 3.

FIG. 5 is a schematic diagram for describing a path of light rays in the optical system of FIG. 3.

* Explanation of symbols for main parts of the drawings

10, 100: AMA optical system 11, 111: lamp

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

14, 114: source mirror 15, 115: reflector

16, 116: field lens 117: illumination uniformity improving member

18, 118: AMA panel 20, 120: projection stop

22, 122: projection lens

In order to achieve the first object of the present invention described above,

A light source for generating light rays;

A source lens for condensing light rays generated from the light source;

A plurality of glass thin plates superimposed, and illuminating uniformity improving means for allowing the light rays collected by the source lens to pass through the respective thin glass plates at a uniform divergence angle;

A source stop having an opening and for concentrating the flux of said light beam having a uniform divergence angle;

An AMA panel including a plurality of mirrors in which light rays passing through the source stop are uniformly illuminated, each mirror being modified to correspond to an intensity of a corresponding one of a plurality of pixels displayed on a screen; And

And a projection lens for projecting light rays reflected from each mirror of the AMA panel onto a screen.

In order to achieve the second object of the present invention described above,

Generating light rays from the light source;

Condensing the light rays generated from the light source and irradiating them with an illumination uniformity improving means in which a plurality of glass sheets are overlapped, so that the light rays pass each glass sheet at a uniform divergence angle;

Directing the beam of light having a uniform divergence angle to a source stop having an opening to concentrate the flux;

Irradiating the AMA panel including a plurality of mirrors with the light beams passing through the source stop at a uniform divergence angle;

Transforming each mirror of the AMA panel into a deformation size corresponding to the intensity of a corresponding one of the plurality of pixels displayed on the screen; And

And projecting light reflected from each mirror of the AMA panel onto a screen.

As described above, the present invention arranges the illumination uniformity improving means between the source lens and the source stop. The illumination uniformity improving means is formed of a structure in which a plurality of thin glass plates are stacked. Since the glass has a property of transmitting part of the incident light and reflecting the rest, the light passing through the source lens passes through each of the thin glass plates, and finally has a uniform divergence angle and exits the illumination uniformity improving means. . At this time, the light generated from the light source is properly adjusted to the source lens so that it can be emitted at the maximum angle while passing through the illumination uniformity improving means.

The amount of light lost is minimized by attaching the mirrors to the four side surfaces of the illumination uniformity improving means, respectively, except for the light incident surface and the light exit surface. In addition, the light incident surface and the light exit surface are polished and then anti-reflected, thereby increasing light transmittance.

Therefore, according to the AMA optical system according to the present invention, the light rays having a uniform divergence angle and passing through the illumination uniformity improving means are uniformly illuminated on the front surface of the AMA panel through the source stop. That is, since the light emitted from each point of the source stop has a uniform angle, not only the light of the AMA panel can be irradiated uniformly, but also the intensity of the light irradiated to the center and the periphery of the AMA panel becomes uniform. Therefore, the uniformity of the light amount modulation of the AMA panel can be improved.

In addition, since the fixed tolerance inherent in the lamp used as the light source does not affect the optical system by the illumination uniformity improving means, the brightness of the screen can be improved. In addition, since the manufacturing method of the illumination uniformity improving means is very simple, it does not significantly affect the manufacturing cost and does not require redesign of the optical system.

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 an optical system using a single plate type thin film AMA according to the present invention as an optical modulator, illustrating a single plate monochrome system.

Referring to FIG. 3, the AMA optical 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, and a field. The lens 116, the illumination uniformity improving member 117, the AMA panel 118, the projection stop 120, and the 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 rays emitted from the lamp in the opposite direction to the source lens 112 and back to the source lens 112. The source lens 112 collects the light rays emitted from the lamp 111 into parallel light.

The illumination uniformity improving member 117 is formed in a structure in which a plurality of glass thin plates 117a are overlapped, and an enlarged view thereof is shown in FIG. 4. 5 is a schematic view for explaining a path of light rays in the illumination uniformity improving member 117.

Referring to FIGS. 4 and 5, in general, glass has a property of transmitting part of an incident light beam and reflecting the rest of light, so that the light collected by the source lens 112 causes each of the thin glass plates 117a to have a characteristic of being transmitted. As it passes, it finally exits the illumination uniformity improving member 117 with a uniform divergence angle [mu] H. At this time, the light generated from the lamp 111 is properly adjusted to the source lens 112 so as to pass through the illumination uniformity improving member 117 at a maximum angle.

Mirrors 119 are attached to four side surfaces 117d except for the light incident surface 117b and the light exit surface 117c of the illumination uniformity improving member 117. The mirrors 119 reflect light rays reflected from the glass thin plates placed at the edges back to the glass thin plates, thereby minimizing the loss of the amount of light passing through the illumination uniformity improving member 117. In addition, the light incident surface 117b and the light exit surface 117c are polished and then subjected to antireflection, thereby increasing the transmittance of light. The antireflection treatment is preferably a coating treatment for absorbing incident light. The four side surfaces 117d and the mirrors 119 of the illumination uniformity improving member 117 are fixed by a plastic mold, an adhesive, or the like. Each glass sheet of the illumination uniformity improving member 117 is preferably formed to a thickness of about 1mm.

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 source mirror 114 serves to reflect the light rays passing through the source stop and redirect its path towards the AMA panel 118.

The field lens 116 transmits each ray passing through the source stop 113 without light loss so that the image of the source stop 113 corresponds to the projection stop 120 in a 1: 1 manner. Investigate with).

The AMA panel 118 includes a plurality of mirrors for reflecting the irradiated rays, which modulate the intensity of the rays in accordance with the image signal voltage applied to the 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 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 flux of light rays passing through the opening of the projection stop 120 controls the intensity of light rays reflected from each mirror of the AMA light modulator 118. 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.

Referring to the operation principle of the AMA optical system 100 according to the present invention having the above-described structure in more detail as follows.

First, when the AMA optical system 100 is driven, light emitted from the lamp 111 composed of an arc lamp such as a halogen metal lamp is irradiated to the illumination uniformity improving member 117 with parallel light through the source lens 112. do. Since the plurality of glass thin plates 117a of the illumination uniformity improving member 117 transmit some of the incident light and reflect the rest of the light uniformity improving member 117, the illumination uniformity improving member 117 is finally applied to each glass thin plate 117a. The divergence angle of the light passing through becomes uniform. As such, the light rays having a uniform divergence angle pass each point of the source stop 113 at a uniform divergence angle. Thus, the light rays passing through the source stop 113 are propagated at a uniform divergence angle without being directed in any particular direction. Light rays passing through the source stop 113 are reflected from the source mirror 114 and irradiated to the AMA panel 118 with parallel light by the field lens 116.

If no image signal voltage is applied to the actuators of the AMA panel 118 (ie, when the voltage is OFF), the respective mirrors of the AMA panel 118 do not vibrate, tilt or bend. As a result, light rays are imaged out of the projection stop 120 and thus cannot reach on a screen (not shown).

If a predetermined voltage less than the maximum voltage is applied to the actuators of the AMA panel 118, each of the mirrors of the AMA panel 118 is inclined to some extent, so that a part of the rays irradiated onto the AMA panel 118 is projected. Projected on the screen by passing through the opening of the stop 120. That is, some of the light rays that are irradiated are reflected by the front surface of the projection stop 120, and the remaining light rays pass through the opening of the projection stop 120.

If the maximum signal voltage is applied to the actuators of the AMA panel 118, the respective mirrors of the AMA panel 118 are completely inclined so that the light beam irradiated on the AMA panel 118 opens the opening of the projection stop 120. Aim to pass. As a result, the light rays reflected by the mirror of the AMA panel 118 pass through the opening of the projection stop 120 and are projected on the screen by the projection lens 122 to display an image corresponding thereto. At this time, the path of the light beam reflected from each 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 panel 118 relative to the projection stop 120.

Here, FIG. 3 illustrates a monochromatic system using a single-plate AMA, but according to another preferred embodiment of the present invention, a color wheel consisting of a series of color fragments of red, green and blue transmission filters The invention can be applied to a single plate color system capable of displaying red, green and blue images by sequentially irradiating red, green and blue light to a single panel AMA using a color wheel.

In addition, according to another preferred embodiment of the present invention, the present invention can be applied to a multi-panel color system using a three panel AMA.

As described above, the present invention arranges the illumination uniformity improving means between the source lens and the source stop. The illumination uniformity improving means is formed of a structure in which a plurality of glass thin plates are overlapped. Since the glass has a property of transmitting part of the incident light and reflecting the rest, the light passing through the source lens passes through each of the thin glass plates, and finally has a uniform divergence angle and exits the illumination uniformity improving means. . The amount of light lost is minimized by attaching the mirrors to the four side surfaces of the illumination uniformity improving means, respectively, except for the light incident surface and the light exit surface. In addition, the light incident surface and the light exit surface are polished and then subjected to antireflection, thereby increasing the transmittance of light.

Therefore, according to the AMA optical system according to the present invention, the light rays having a uniform divergence angle and passing through the illumination uniformity improving means are uniformly illuminated on the front surface of the AMA panel through the source stop. That is, since the light emitted from each point of the source stop has a uniform angle, not only the light of the AMA panel can be irradiated uniformly, but also the intensity of the light irradiated to the center and the periphery of the AMA panel becomes uniform. Therefore, the uniformity of the light amount modulation of the AMA panel can be improved.

In addition, since the fixed tolerance inherent in the lamp used as the light source does not affect the optical system by the illumination uniformity improving means, the brightness of the screen can be improved. In addition, since the manufacturing method of the illumination uniformity improving means is very simple, it does not significantly affect the manufacturing cost and does not require redesign of the optical system.

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 present invention without departing from the spirit and scope of the invention described in the claims below. I can understand that you can.

Claims (7)

A light source 111 for generating light rays; A source lens 112 for condensing light rays generated from the light source; A plurality of glass thin plates 117a overlapping each other, and illumination uniformity improving means 117 for allowing the light rays collected by the source lens to pass through the respective thin glass plates at a uniform divergence angle; A source stop 113 having an opening and for concentrating the flux of said light ray having a uniform divergence angle; And a plurality of mirrors in which the rays passing through the source stop are uniformly illuminated, each mirror modified to correspond to the intensity of a corresponding one of the plurality of pixels displayed on the screen. Panel 118; And And a projection lens (122) for projecting light rays reflected from each mirror of the panel (118) of the actuated mirror array onto the screen. The method of claim 1, wherein the illumination uniformity improving means 117 has mirrors 119 attached to four side surfaces 117d except for the light incident surface 117b and the light exit surface 117c. The light incident surface (117b) and the light exit surface (117c) is an optical system characterized in that the anti-reflective treatment. The optical system according to claim 2, wherein the four sides (117d) of the illumination uniformity improving means (117) and the mirrors (119) are fixed with a plastic mold or an adhesive. The optical system according to claim 2, wherein the light incident surface (117b) and the light exit surface (117c) of the illumination uniformity improving means (117) are polished before antireflective treatment. The actuated mirror according to claim 1, wherein the source mirror 114 reflects light beams passing through the source stop 113 and changes its path, and the light beam reflected from the source mirror 114 is parallel to the actuated mirror. A field lens 116 for irradiating the array panel 118, and an flux having an opening to control the intensity of light reflected from each mirror of the actuated mirror array panel 118. Optical system further comprises a projection stop (120). Generating light rays from the light source; Condensing the light rays generated from the light source and irradiating them with an illumination uniformity improving means in which a plurality of glass sheets are overlapped, so that the light rays pass each glass sheet at a uniform divergence angle; Directing the beam of light having a uniform divergence angle to a source stop having an opening to concentrate the flux; Irradiating the actuated mirror array panel including a plurality of mirrors with the light rays passing through the source stop at a uniform divergence angle; Transforming each mirror of the actuated mirror array panel into a deformation size corresponding to the intensity of a corresponding one of a plurality of pixels displayed on the screen; And Projecting light reflected from each mirror of the actuated mirror array panel onto a screen. 7. A projection stop according to claim 6, wherein prior to projecting the light reflected from each mirror of said actuated mirror array panel onto a screen, the light beam reflected from each mirror of said actuated mirror array panel is moved to a projection stop having an opening. And sending a flux of light rays passing through the opening to control the intensity of the light rays reflected from the mirror.