KR100208679B1 - Actuated mirror array optical projection system and a projection method using the same - Google Patents

Abstract

An actuated mirror array (AMA) optical system capable of removing ghosts caused by surface reflection of a field lens and a projection method using the same are disclosed. The optical system includes a light source for generating a light beam and a plurality of mirrors on which the light beam is illuminated, each mirror being modified to correspond to the intensity of a corresponding one of the plurality of pixels displayed on the screen. Includes a panel. The projection lens projects light rays reflected from each mirror of the AMA panel onto the screen. The source mirror is rotated at -45 ° on the optical axis of the projection lens and reflects the light generated from the light source to enter the AMA panel. The field lens is half-divided so that only the portion above the optical axis is used, and the light reflected from the source mirror is irradiated to the AMA panel with parallel light. The source lens can be installed to prevent collision of the source mirror and the projection lens while eliminating ghosts caused by surface reflection of the field lens. In addition, since the center of the light spot incident on the AMA panel is located on the optical axis of the projection lens, it is possible to reduce the design cost of the projection lens.

Description

Actuated mirror array optics and projection method using the same

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 as a light modulator for projecting an image onto a screen, The present invention relates to an optical system capable of removing ghosts caused by surface reflection of a lens and a projection method using the same.

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 of improving the brightness of the screen compared to 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 170W to 250W metal halted 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 (13) having an aperture for passing the light beam and determining an amount of light beam forming an image ), A field lens 16 for mapping the image of the source stop 13 to the projection stop 20 1: 1, and a plurality of mirrors, and modulating the intensity of light emitted from the field lens 16. A projection panel (20) having an opening for passing the light beam, and a projection stop (20) for concentrating the flux of the modulated light beam, and a light beam passing through the projection stop (20). Projection to project onto And a Sean lens 22.

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

First, when the AMA optical system 10 is driven, the 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 and then the field lens 16. ) Is incident. The light is then irradiated onto the AMA panel 18 with parallel light through the field lens 16. 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 Fig. 1, reference numeral P1 denotes a light beam irradiated to the AMA panel 18, P2 denotes an untilted light beam, and P3 denotes a tilted light beam.

According to the conventional AMA optical system 10 described above, in the process of irradiating the light emitted from the lamp 11 onto the AMA panel 14 through the field lens 16, a part of the angle of the field lens 16 Reflected from the surface. 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 symmetrically concentrated ghost on the left and right of the center on the screen. Typically, the illuminance difference between the background and the ghost pattern on the screen is 6 to 7: 1, and the lower the brightness of the background, the clearer the ghost image is detected. In particular, when a zero voltage is applied to the AMA panel and the screen becomes dark, the image of such ghost is clearly displayed. Since ghost always acts as noise and degrades image quality, it is necessary to remove such ghost in order to realize a reliable optical system.

Accordingly, the present applicant has invented an AMA optical system capable of removing ghost, and filed it with Korean Patent Application No. 96 # 52682 on November 7, 1996 to the Korean Patent Office.

2 is a schematic diagram showing an AMA optical system described in the applicant's prior application. 3A to 3C are schematic diagrams showing propagation paths of light rays in the AMA optical system.

Referring to FIG. 2, the AMA optical system 50 includes a halogen metal lamp 51, a reflector 55, a source lens 52, a source stop 53, a field lens 56, an AMA panel 58, and a projection stop. 60, and projection lens 62.

In Fig. 2, reference numeral P1 denotes a light beam irradiated to the AMA panel 58, P2 denotes an untilted light beam, and P3 denotes a tilted light beam.

According to the conventional AMA optical system 10 shown in FIG. 1, the ghost generated in the second surface 16b of the field lens 16 is less visible due to its low reflectance. Therefore, the ghost generated by the light rays reflected from the first surface 16a and the third surface 16c of the lower end of the field lens 16 should be removed. Accordingly, in the AMA optical system 50 of FIG. 2, the AMA panel 58 is removed from the optical axis in order to remove ghost patterns occurring at the lower end of the field lens (ie, the lower part of the optical axis). By placing them up by a distance of, only the light passing through the upper end of the field lens 56 (i.e., above the optical axis) was irradiated to the AMA panel 58 as shown in FIG. 3A.

The light reflected from the plane 56a of the field lens is the same in its propagation path both above and below the optical axis. Therefore, when only the upper end of the field lens 56 is used, the light rays reflected from the plane 56a of the field lens at the upper part of the optical axis are totally reflected to the upper part of the projection stop 60 as shown in FIG. 3B. Therefore, the ghost pattern cannot be formed on the screen. On the other hand, the light rays reflected from the curved surface 56b of the field lens have different propagation paths of the light rays reflected from the upper part of the optical axis and the propagation paths of the light rays reflected from the lower part according to the curvature of the lens. That is, as shown in Figure 3C the optical axis and a certain distance ( Beams reflected from the curved surface 56b of the field lens pass through the projection stop 60. Therefore, in the AMA optical system 50, a certain distance (corresponding to the minimum distance that a ghost pattern can occur) By raising the AMA panel 58 up to only the upper end of the field lens 56, the light reflected from the curved surface 56b of the field lens cannot pass through the projection stop 60.

According to the AMA optical system 50 described above, the aperture of the projection lens 62 is doubled because the central axis of the AMA panel 58 is shifted upward from the optical axis of the projection lens 62 (ie, the aperture center). You lose. In order to install a source mirror that reflects light beams passing through the source stop 53 and irradiates the AMA panel 58, the unit mirror of the AMA panel 58 has a maximum inclination angle of 3 °. The source mirror should be installed such that the light reflected therefrom is incident at an angle of about 6 ° with respect to the central axis of the AMA panel 58. However, since the aperture of the projection lens 62 is large in the AMA optical system 50, a problem arises in which the source mirror and the projection lens 62 collide with each other, making it difficult to install the source mirror.

Meanwhile, in order to increase the light utilization efficiency of the AMA optical system, the light beams generated from the lamps 51 should be irradiated to the AMA panel 58 with less loss. Therefore, the center of the beam spot is the AMA panel ( 58) to face the central axis. However, in the AMA optical system 50 described above, since the center axis of the AMA panel 58 is shifted upward from the optical axis of the projection lens 62, the center of the light spot must deviate from the optical axis of the projection lens 62 to maintain the light efficiency. do. In this case, since many aberrations such as spherical aberration and coma occur in the projection lens 62, the design cost is increased.

Accordingly, the present invention has been made to solve the above-mentioned problems of the conventional method, and a first object of the present invention is to eliminate ghosts caused by surface reflection of a field lens in an optical system using an AMA panel as an optical modulator. In addition, the present invention provides an optical system that is capable of installing a source mirror and facilitates the design of a projection lens.

It is a second object of the present invention to provide a projection method capable of removing ghosts using the optical system.

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

2 is a schematic diagram showing the actuated mirror array optical system described in the applicant's prior application.

3A to 3C are schematic diagrams showing propagation paths of light rays in the optical system of FIG. 2.

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

5 is a cross-sectional view of an actuated mirror array panel used in the optical system of FIG. 4.

Explanation of symbols for main parts of the drawings

10, 50, 100 ... AMA optics 11, 51, 111 ... Lamp

12, 52, 112 ... source lens 13, 53, 113 ... source stop

114 ... source mirror 15, 55, 115 ... reflector

16, 56, 116 ... field lenses 18, 58, 118 ... AMA panels

20, 60, 120 ... projection stop 22, 62, 122 ... projection lens

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

A light source for generating light rays;

An AMA panel comprising a plurality of mirrors on which the rays are illuminated, each mirror adapted to correspond to an intensity of a corresponding one of the plurality of pixels displayed on the screen;

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

A source mirror positioned at -45 ° on the optical axis of the projection lens and reflecting light rays generated from the light source to be incident on the AMA panel; And

The optical system comprises a field lens for dividing only the upper portion of the optical axis to be used, and irradiating the light reflected from the source mirror to the AMA panel with parallel light.

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

Generating light rays from the light source;

Injecting the light beam generated from the light source into a half-field field lens so that only the upper portion of the optical axis is used to produce parallel light, and irradiating the same to an AMA panel including a plurality of mirrors;

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

Projecting light reflected from each mirror of said AMA panel onto a screen through a projection lens,

Before injecting a light beam generated from the light source into a half-field field lens so that only the upper part of the optical axis is used, the light beam is irradiated to a source mirror rotated by -45 ° on the optical axis of the projection lens to change its light path. It provides a projection method characterized in that it further comprises the step of.

The field lens is divided in half so that only its upper end (i.e., above the optical axis) is used to remove ghosts caused by the light reflected from each side of the field lens. A source mirror for reflecting light rays generated from the light source and changing its path to the AMA panel is installed by rotating at -45 ° with respect to the optical axis of the projection lens. Since the source mirror is located inside the aperture of the projection lens, the center of the light spot incident on the AMA panel through the source mirror is positioned on the optical axis of the projection lens.

When no image signal voltage is applied to the AMA panel, the light rays reflected from each mirror of the AMA panel are returned back to the light source through the source mirror. On the other hand, when an image signal voltage is applied to the AMA panel, the light rays reflected from each mirror of the AMA panel exit to both sides of the source mirror and are projected onto the screen through the projection lens. In this case, in order to maintain the uniformity of the tilting angle of each mirror of the AMA panel, the mirrors may be tilted in opposite directions, that is, facing each other, with respect to the optical axis of the projection lens. To place.

Therefore, the optical system can be compactly constructed by using a half-divided field lens to remove ghosts. In addition, since the source mirror is provided inside the aperture of the projection lens, it is possible to prevent the source mirror and the projection lens from colliding with each other. In addition, since the center of the light spot incident on the AMA panel is located on the optical axis of the projection lens, aberration does not occur in the projection lens, thereby reducing the design cost.

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

Referring to FIG. 4, 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. Lens 116, AMA panel 118, projection stop 120, and projection lens 122.

Lamp 111 for emitting light is preferably a 170 W to 250 W halogen metal lamp that emits long wavelength infrared (LWIR) to ultraviolet (UV) light in the spectrum. 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 light rays emitted from the lamp 111 into parallel light. 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 113 to redirect its path towards the AMA panel 118. The source mirror 114 is disposed to rotate at -45 ° on the optical axis of the projection lens 122. Therefore, since the source mirror 114 is located inside the aperture of the projection lens 122, the center of the light spot incident on the AMA panel 118 through the source mirror 114 is located at the optical axis of the projection lens 122. Done.

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). In a conventional AMA optical system, a part of light is reflected from each side of the field lens in a process in which light emitted from the lamp is irradiated to the AMA panel through the field lens. At this time, the light rays reflected from each side above the optical axis of the field lens cannot pass through the projection stop, but the light rays reflected from each side below the optical axis pass through the projection stop to prevent ghosts acting as noise on the screen. To form. In the AMA optical system described in the applicant's prior application, the ghost is removed by placing the AMA panel at the upper end of the field lens without dividing the field lens, but in the AMA optical system 100 of the present invention, the upper portion of the optical axis of the field lens 116, That is, the field lens 116 was divided in half so as to use only the upper end portion. Thus, the present invention provides the advantage that the optical system can be compactly constructed while eliminating ghosts by using the half-divided field lens 116.

The AMA panel 118 includes a plurality of mirrors 118a for reflecting the irradiated rays, which modulate the intensity of the rays in accordance with an image signal voltage applied to an actuator provided thereunder. That is, each mirror 118a is deformed to a deformation size corresponding to the intensity of the corresponding one pixel among the plurality of pixels displayed on the screen. 5 is a cross-sectional view of the AMA panel. Referring to this, the mirrors 118a of the AMA panel are arranged such that the mirrors on both sides of the AMA panel are tilted in opposite directions, that is, facing each other, based on the optical axis of the projection lens 122.

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, the light rays emitted from the halogen metal lamp 111 are condensed into parallel light through the source lens 112, and then pass through the source stop 113 to the source mirror 114. Is investigated. Light rays reflected from the source mirror 114 are irradiated to the AMA panel 118 with parallel light by the field lens 116.

If no image signal voltage is applied to the AMA panel 118 (ie, when the voltage is OFF), the respective mirrors 118a of the AMA panel do not vibrate, tilt or bend. At this time, since the center of the light spot incident from the source mirror 114 to the AMA panel 118 is located at the central axis of the AMA panel 118, the light rays reflected from the non-tilted mirrors 118a are not reflected. Back to lamp 111 via 114.

If an image signal voltage is applied to the AMA panel 118, the respective mirrors 118a of the AMA panel are vibrated, tilted or bent, depending on the embodiment used. In this case, the mirrors 118a of the AMA panel are arranged such that the mirrors on both sides of the AMA panel are tilted in opposite directions with respect to the optical axis of the projection lens 122. When an image signal voltage is applied to the mirrors, the mirrors on both sides of the projection lens 122 are tilted in a direction facing each other. Accordingly, the light rays reflected from the mirror 118a exit to both sides of the source mirror 114, pass through the opening of the projection stop 120, and are then projected onto the screen through the projection lens 112. If the mirrors 118a of the AMA panel are not arranged to tilt in opposite directions with respect to the optical axis of the projection lens 122, a part of the rays reflected from the tilted mirror is fitted to the source mirror 114 so that the lamp The problem of returning to 111 again occurs. Therefore, in order to maintain the uniformity of the tilting angle of the mirrors 118a, the mirrors on both sides of the projection lens 122 should be disposed so as to tilt in opposite directions.

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 present 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 optical system and the projection method using the same according to the present invention have the following effects.

First, the optical system can be compactly constructed by dividing the field lens so that only its upper end (i.e., the upper part of the optical axis) is used to remove ghosts generated by the light reflected from each side of the field lens.

Secondly, a source mirror for reflecting light rays generated from the light source and changing its path to the AMA panel is installed by rotating at -45 ° on the optical axis of the projection lens. Therefore, since the source mirror is located inside the aperture of the projection lens, the source mirror and the projection lens can be prevented from colliding with each other.

Third, since the source mirror is located on the optical axis of the projection stop, the center of the light spot incident on the AMA panel from the source mirror is located on the optical axis of the projection lens. Therefore, aberrations such as spherical aberration and coma do not occur in the projection lens, thereby reducing the design cost.

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 (9)

A light source 111 for generating light rays; And a plurality of mirrors 118a on which the light beams are illuminated, each mirror being modified to correspond to the intensity of a corresponding one of the plurality of pixels displayed on the screen. 118); A projection lens 122 for projecting light rays reflected from each mirror of the actuated mirror array panel onto a screen; A source mirror 114 which is rotated at -45 ° on the optical axis of the projection lens and reflects light rays generated from the light source to be incident on the actuated mirror array panel; And And a field lens (116) for dividing only the upper portion of the optical axis to be used, and irradiating the reflected light from the source mirror (114) to the actuated mirror array panel with parallel light. The optical system according to claim 1, wherein the mirrors (118a) of the actuated mirror array panel are arranged such that mirrors on both sides thereof are deformed in opposite directions with respect to the optical axis of the projection lens (122). The optical system according to claim 1, wherein the source mirror (114) is located inside the aperture of the projection lens (122). 2. The source stop of claim 1, further comprising: a source lens 112 for condensing the light rays generated from the light source with parallel light, and a source stop for concentrating the flux of the light rays collected by the source lens to the source mirror. 113, and a projection stop 120 having an opening, the projection stop 120 of which flux of light passing through the opening controls the intensity of light reflected from each mirror of the actuated mirror array panel. . Generating light rays from the light source; Injecting a light beam generated from the light source into a half-field field lens so that only an upper portion of the optical axis is used to produce parallel light, and irradiating the light to the actuated mirror array panel including a plurality of mirrors; 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 through a projection lens, Before injecting a light beam generated from the light source into a half-field field lens so that only the upper part of the optical axis is used, the light beam is irradiated to a source mirror rotated by -45 ° on the optical axis of the projection lens to change its light path. And further comprising a step of causing the projection. The projection method according to claim 5, wherein the mirrors of the actuated mirror array panel are arranged such that mirrors on both sides thereof are deformed in opposite directions with respect to the optical axis of the projection lens. 6. The projection method according to claim 5, wherein when each mirror of the actuated mirror array panel is not deformed, the light reflected from each mirror returns back to the light source through the source mirror. 6. The method of claim 5, further comprising: prior to irradiating the source mirror with light rays generated from the light source, incident light rays generated from the light source into a source lens to make parallel light; And directing a light beam passing through the source lens to a source stop having an opening to concentrate the flux of the light beam. 6. The projection stop according to claim 5, wherein before the projecting light reflected from each mirror of the actuated mirror array panel onto the screen, the light beam reflected from each mirror of the 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.