KR19990004758A - An active mirror array optical system - Google Patents

Abstract

An optical system using an actuated mirror array (AMA) panel as an optical modulator is disclosed. The AMA panel is composed of a plurality of mirrors on which the light beams generated from the light source are illuminated, and each mirror is modified to correspond to the intensity of a corresponding one of the plurality of pixels displayed on the screen. The source stop has an aperture to determine the amount of light that is irradiated to the AMA panel, and the field lens irradiates the light rays that have passed through the source stop to the AMA panel as parallel light. The projection stop has an aperture and focuses the flux of the reflected light from each mirror of the AMA panel. The focal length F 'of the field lens is determined so that the distance S' between the field lens and the source stop is greater than the distance S between the field lens and the projection stop. Therefore, it is possible to reduce the ghost light amount while increasing the size of the optical system, increase the power of the lamp, and secure the installation space of the source part.

Description

An active mirror array optical system

The present invention relates to an optical system, and more particularly, to an optical system using an Actuated Mirror Array (AMA) panel as an optical modulator, in which a focal length of a field lens is lengthened, ) To an AMA optical system capable of reducing the amount of light or increasing the lamp power.

In general, a spatial light modulator, which is an apparatus 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 divided 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 the direct-view type image display device is a CRT (Cathode Ray Tube). Such a CRT device is called a so-called CRT, and its image quality is excellent. However, since the weight and volume of the CRT device are increased, .

The projection type image display device includes a liquid crystal display (LCD), a deformable mirror device (DMD), and an actuated mirror array (AMA) Quot;). Such a projection type image display apparatus can be divided into two groups again according to their optical characteristics. That is, devices such as LCDs can be classified as transmissive spatial light modulators, while DMDs and AMAs can be classified as reflective spatial light modulators.

Since the optical structure of the transmission optical modulator such as the LCD is very simple, it can be made thin to lighten the weight and reduce the volume. However, the light efficiency is low due to the polarity of light, and there is a problem inherently present in the liquid crystal material, for example, the response speed is slow and the inside is easily overheated. In addition, the maximum optical efficiency of existing transmission optical modulators is limited to a range of 1 to 2% and requires darkroom conditions to provide acceptable display quality.

Optical modulators such as DMD and AMA have been developed to solve the problems of the above-mentioned LCD type optical modulator.

DMD exhibits relatively good light efficiency of about 5%, but severe fatigue problems are caused by the hinge structure employed in the DMD. Further, there is a disadvantage that a very complicated and expensive driving circuit is required.

Each mirror installed in the AMA reflects the light incident from the light source at a predetermined angle and the reflected light is projected on the screen through an aperture such as a slit or a pinhole It is a device that can control the speed of light to make an image. Therefore, the structure and operation principle are simple, and a higher light efficiency (light efficiency of 10% or more) than that of LCD or DMD can be obtained. In addition, the contrast is improved, and a bright and clear image can be obtained.

Each of the actuators of the AMA is deformed in accordance with an electric image signal to be applied and an electric field generated by the bias voltage. When the actuator causes deformation, the respective mirrors mounted on the upper portion are inclined. Accordingly, the inclined mirrors reflect light incident from a light source at a predetermined angle so that an image can be formed on the screen. A piezoelectric material such as PZT (Pb (Zr, Ti) O ₃ ) or PLZT ((Pb, La) (Zr, Ti) O ₃ ) is used as an actuator for driving each of the mirrors. Further, the actuator may be configured as an electrostriction material such as PMN (Pb (Mg, Nb) O ₃ ).

The AMA is divided into a bulk type and a thin film type. Bulk AMA is disclosed in U.S. Patent 5,085,497 to Gregory Um et al. The bulk type AMA is formed by cutting a multilayer ceramic thinly and mounting a ceramic wafer having a metal electrode therein in an active matrix with a built-in transistor, processing it by a sawing method, and installing a mirror thereon. However, bulk AMA requires very high precision in design and manufacture, and has the disadvantage of slow response of the strained layer. Accordingly, a thin film type AMA that can be manufactured using a semiconductor manufacturing process has recently been developed. For example, this thin film type AMA has been disclosed in Japanese Patent Application No. 95-13353 (the name of the invention: manufacturing method of optical path adjusting device) filed by the present applicant for a patent in the Korean Intellectual Property Office.

Thin-film AMA is fabricated using a thin film process well known in the semiconductor industry. The thin film AMA was developed to transmit enough light on the screen to display a digital image at high brightness and high contrast under normal room lighting conditions. The thin-film AMA is a reflective optical modulator using thin film piezo-electric actuators in connection with microscopic mirrors of the order of 100 m to 100 m. Thin-film AMAs have been developed to have a high degree of integration for high contrast, sufficient light efficiency for high brightness, and large scale integration uniformity over 300,000 pixels of a single panel mirror. The thin film AMA consists of panels of 640 x 480 pixels each representing red, green and blue. The pixels are designed as a cantilever structure to maximize the mirror surface area to increase the light efficiency. The cantilever structure largely includes a cantilever mirror operated by an active matrix and an applied signal voltage to which an image signal voltage is applied.

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 metal halide lamp 11 of 170 W to 250 W for emitting a light beam, a reflector (Reflector) 11 for reflecting a light beam from the lamp 11, A source lens 12 for converting a light beam emitted from the lamp 11 into a parallel light, an aperture for passing the light beam, and a source stop for determining the amount of light forming the image, A source mirror 13 for reflecting the light beam that has passed through the source stop 13 and changing the optical path of the light beam so that the image of the source stop 13 is mapped to the projection stop 20 at a ratio of 1: An AMA panel 18 having a plurality of mirrors for modulating the intensity of the light emitted from the field lens 16, an aperture for passing a light beam, a flux of the modulated light beam A projection stop 20 for concentrating light, And a projection lens 22 for projecting the light ray that has passed through the projection stop 20 onto a screen (not shown).

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

First, when the AMA optical system 10 is driven, a light beam emitted from the halogen lamp 11 is condensed into parallel light by the source lens 12, passes through the opening of the source stop 13, 14 and then is incident on the field lens 16. [ The light is then irradiated onto the AMA panel 18 with parallel light through a field lens 16. Each mirror of the AMA panel 18 is vibrated, tilted or bent according to the image signal voltage applied to the actuator provided thereunder. Accordingly, the light beam passing through the field lens 16 is reflected from the mirrors, passes through the opening of the projection stop 20, and is 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 of the AMA panel 18 determines the intensity of the light beam passing through the aperture of the projection stop 20. That is, the flux of light rays passing through the aperture of the projection stop 20 is controlled by the direction of the mirror of the AMA panel 18 relative to the projection stop 20.

2 is a schematic view for explaining the optical path between the source stop 13, the field lens 16, and the projection stop 20 in the conventional AMA optical system 10 described above.

2, the conventional field lens 16 has a focal length F such that the image of the source stop 13 corresponds to the projection stop 20 at a ratio of 1: 1. That is, the magnification of the field lens 16 is determined so that the size of the source stop 13 and the projection stop 20 is equal to 1: 1. In this optical system, since the space for installing the source mirror 14 is narrow, there is a problem that the optical path of the light beam reflected from the source mirror 14 and the optical path from the AMA panel 18 to the projection lens 22 collide May occur.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical system using an AMA panel as an optical modulator in which the focal distance of the field lens is increased to reduce the ghost light amount while increasing the system size, And to provide an AMA optical system capable of securing an AMA optical system.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing an optical mirror system of an active mirror array according to a conventional method; Fig.

Fig. 2 is a schematic view for explaining optical paths between a source stop, a field lens, and a projection stop in the optical system shown in Fig. 1; Fig.

3 is a schematic view showing an optical mirror array system according to the present invention.

Fig. 4 is a schematic view for explaining the optical path between the source stop, the field lens, and the projection stop in the optical system shown in Fig. 3; Fig.

DESCRIPTION OF THE REFERENCE NUMERALS

100: AMA optical system 111: lamp

112: source lens 113: source stop

114: source mirror 115: reflector

116: field lens 118: AMA panel

120: projection stop 122: projection lens

According to an aspect of the present invention, there is provided a light source device comprising: a light source for generating a light beam; A plurality of mirrors on which the light beams are illuminated, each mirror being deformed to correspond to intensity of a corresponding one of a plurality of pixels displayed on a screen; A source stop having an aperture and determining an amount of light to be irradiated to the AMA panel; A field lens for irradiating the light passing through the source stop to the AMA panel as parallel light; And a projection stop for concentrating the flux of light reflected from each mirror of the AMA panel, wherein the focal length F 'of the field lens is such that the distance S' between the field lens and the source stop is greater than the distance between the field lens and the projection And the distance S between the stoppers.

The present invention makes the focal length of the field lens longer than the focal length of the field lens used in the conventional AMA optical system. Fixing the size of the source stop with such a focal length reduces the image size of the source stop reaching the projection stop, so that the size of the projection stop is reduced. Therefore, the amount of ghost light passing through the projection stop is reduced to about 1/4.

Further, by fixing the size of the projection stop with the focal length and increasing the size of the source stop, it is possible to use a lamp having a larger power than the conventional optical system.

Therefore, according to the present invention, it is possible to reduce the ghost light amount or increase the power of the lamp while fixing the size of the AMA optical system to be the same as the conventional one. Further, since the optical path length is increased as compared with the conventional optical system, it is possible to secure a space for installing the source portion while ensuring a sufficient optical path.

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

3 is a schematic view showing a single plate type AMA optical system according to the present invention.

3, the AMA optical system 100 according to the present invention includes a lamp 111 for emitting a light beam, a source lens 112, a source stop 113, a source mirror 114, a reflector 115, A lens 116, an AMA panel 118, a projection stop 120, and a projection lens 122.

The lamp 111 for emitting light is preferably an arc lamp, such as a halogen metal lamp of 170 W to 250 W, which emits long wavelength infrared (LWIR) to ultraviolet (UV) radiation in the spectrum. The reflector 115 reflects the light beam emitted from the lamp in the opposite direction to the source lens 112 and directs the light to the source lens 112 again.

The source lens 112 serves to condense light emitted from the lamp 111 into parallel light. The source stop 113 is an optically opaque member and has an opening that is configured to pass a light beam therethrough. The source stop 113 determines the amount of light that forms an image. The source mirror 114 reflects the light beam passing through the source stop and changes its path to the AMA panel 118.

The field lens 116 serves to irradiate each light ray passing through the source stop 113 to the AMA panel 118 without loss of light.

The AMA panel 118 includes a plurality of mirrors for reflecting the irradiated light beams, the mirrors modulating the intensity of the light beams according to the image signal voltage applied to the actuators provided thereunder. That is, each mirror is transformed into a deformation size corresponding to the strength of one pixel among a plurality of pixels displayed on the screen.

The projection stop 120 is an optically opaque member and has an optically reflective surface and an aperture formed therethrough to allow light to pass therethrough. Preferably, the opening is a pinhole or slit. The flux of light rays passing through the aperture of the projection stop 120 controls the intensity of the reflected light from each mirror of the AMA light modulator 118. The projection lens 122 performs a function of projecting a light ray passing through the opening of the projection stop 120 onto a screen (not shown) and displaying an image corresponding thereto.

4 is a schematic view for explaining an optical path between the source stop 113, the field lens 116 and the projection stop 120. As shown in Fig.

4, the focal length F 'of the field lens 116 according to the present invention is such that the distance S' between the field lens 116 and the source stop 113 is greater than the distance between the field lens 116 and the projection stop 120 S < / RTI > That is, the focal length F 'of the field lens 116 is larger than the focal length F of the conventional field lens 16 shown in FIG. This will be described in more detail as follows.

In the present invention, the focal length F 'of the field lens 116 is

, And the magnification m satisfies the relationship

.

Accordingly, when the focal length F 'is increased and the distance S between the field lens 116 and the projection stop 120 is fixed as compared with the conventional optical system shown in FIG. 2, 116 and the source stop 113 becomes longer. As a result, the size of the source stop 113 becomes larger than the size of the projection stop 120 (see the above equation (2)).

If the size of the source stop 113 is the same as that of the conventional optical system shown in Fig. 2 with the focal length F 'of the field lens 116 as described above, then the source stop 113 reaching the projection stop 120 The image size of the projection stop 120 is reduced. As a result, the size of the projection stop 120 is reduced. Therefore, the light rays reflected from each surface of the field lens 116, especially the surface under the optical axis, passing through the projection stop 120 and forming a ghost symmetrically concentrated on the left and right sides of the center on the screen, Is reduced to about 1/4, so that a reliable optical system can be constructed.

If the size of the source stop 113 is increased while fixing the size of the projection stop 120 with the focal length F 'of the field lens 116, a larger lamp 111 can be used in the conventional optical system have. Generally, the larger the size of the reflector 115 of the lamp is, the more stable and the power can be increased and the closer to the nature of the point source. Therefore, according to the present invention, the brightness of the screen can be improved by increasing the power of the lamp 111.

Further, in both of the above cases, since the optical path length from the source portion (the source stop, the source mirror) to the field lens 116 becomes longer, a space for installing the source portion can be ensured while ensuring a sufficient optical path.

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

First, when the AMA optical system 100 is driven, a light beam emitted from a lamp 111 composed of an arc lamp such as a halogen metal lamp is condensed into parallel light through the source lens 112, And is irradiated onto the source mirror 114. The light beam reflected from the source mirror 114 is first irradiated onto the AMA panel 118 with the parallel light through the field lens 116 after the path thereof is primarily changed.

If the image signal voltage is not applied to the actuators of the AMA panel 118 (i.e., when the voltage is OFF), each mirror of the AMA panel 118 does not vibrate, tilt, or bend. As a result, the light beam is out of the projection stop 120 and is in phase, so that it can not reach the screen (not shown).

If a certain voltage less than the maximum voltage is applied to the actuators of the AMA panel 118, some of the mirrors of the AMA panel 118 are tilted to some extent, And is projected onto the screen by passing through the opening of the stop 120. That is, some of the irradiated light is reflected by the front surface of the projection stop 120, and the remaining light rays pass through the aperture of the projection stop 120.

If the maximum signal voltage is applied to the actuators of the AMA panel 118, the mirrors of the AMA panel 118 are completely tilted so that the light rays irradiated onto the AMA panel 118 are directed to the apertures of the projection stop 120 Is aimed to pass. As a result, the light beam reflected by the mirror of the AMA panel 118 passes through the opening of the projection stop 120 and is projected on the screen by the projection lens 122, thereby displaying 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 aperture of the projection stop 120. That is, the flux of light rays passing through the aperture of the projection stop 120 is controlled by the orientation of the mirror of the AMA panel 118 relative to the projection stop 120.

Here, FIG. 3 illustrates a single color system using a single plate type AMA. According to another preferred embodiment of the present invention, a color wheel composed 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 lights to a single panel AMA using a color wheel.

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

As described above, the present invention increases the focal length of the field lens to 1 or more by increasing the focal length of the field lens so that the distance S 'between the field lens and the source stop is larger than the distance S between the field lens and the projection stop.

Accordingly, the size of the AMA optical system can be reduced to the same size as the conventional one while the size of the projection stop can be reduced to reduce the amount of ghost light, or the size of the source stop can be increased to increase the power of the lamp. Further, since the optical path length from the source portion to the field lens is increased as compared with the conventional optical system, it is possible to secure a sufficient space for installing the source portion while ensuring a sufficient optical path.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims It can be understood that

Claims (4)

A light source 111 for generating a light beam; (AMA) panel < RTI ID = 0.0 > (AMA) < / RTI > panel (118); A source stop (113) having an opening, the source stop (113) determining the amount of light irradiated to the active mirror array panel; A field lens (116) for irradiating the actuated mirror array panel with parallel rays of light passing through the source stop; And And a projection stop (120) for focusing the flux of light reflected from each mirror of the active mirror array panel, The focal length F 'of the field lens 116 is determined so that the distance S' between the field lens 116 and the source stop 113 is greater than the distance S between the field lens 116 and the projection stop 120 Optical system. The optical system according to claim 1, wherein the field lens (116) has a magnification of at least one. The optical system according to claim 1, wherein the size of the source stop (113) is larger than the size of the projection stop (120). The optical system according to claim 1, further comprising a projection lens (122) for projecting a light ray passing through an opening of the projection stop (120) onto a screen.