KR100201829B1 - Optical projection system - Google Patents

Abstract

An optical projection system is disclosed that can eliminate ghost patterns. An optical projection system includes a light source for generating light beams, an actuated mirror array (AMA) light modulator for modulating the light beams according to an applied electrical signal and changing their light paths and projecting them onto a screen, and actuating the light beams in parallel light. A modulation lens for irradiating onto the shaped mirror array light modulator, a projection stop to focus the flux of light modulated by the actuated mirror array light modulator, and a modulation and placement between the modulation lens and the actuated mirror array light modulator And a plate for removing a ghost pattern formed by the light rays reflected from each side of the lens passing through the projection stop and projected onto the screen. Since the intensity of the light projected to the position where the ghost pattern is formed on the screen is compensated for by the ghost pattern removing plate, the ghost pattern acting as noise can be removed.

Description

Optical projection system

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an optical projection system, and in particular in an optical projection system using an Actuated Mirro Array (hereinafter referred to as AMA) module used to project a digital image onto a screen, the reflection of light on the lens surface. The present invention relates to an optical projection system capable of eliminating ghost patterns caused by the present invention.

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 due to the on-off driving caused by the non-stable property.

In contrast, AMA is a piezoelectrically driven mirror array that provides light efficiency of 10% or more. The AMA device, each of the mirrors installed therein reflects the light flowing from the light source at a predetermined angle, and the reflected light can adjust the luminous flux to pass through the slit (Slit) to form an image on the screen Device. Therefore, its structure and operation principle are simple, and high light efficiency can be obtained compared to LCD, DMD, and the like. 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.

In general, each actuator causes a deformation in accordance with the electric field generated by the applied electric 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. Piezoelectric ceramics such as PZT (Pb (Zr, Ti) O ₃ ) or PLZT ((Pb, La) (Zr, Ti) O ₃ ) or PMN (Pb (Mg, Nb) A total distortion ceramic such as) O ₃ ) is used.

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 that can be manufactured by using a semiconductor manufacturing process has been developed to complete the quality of mirror arrays. The thin film type AMA is disclosed in Korean Patent Application No. 95-13358, filed on May 26, 1995 by the present applicant.

Thin-film AMA is a reflective light modulator using thin film piezo-electric actuators in the context of fine mirrors, which combines more than 300,000 pixels of a single-plate mirror to achieve uniformity of large scale integration. It has been developed to have. The thin film type AMA is composed 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 largely includes an active matrix to which an image signal voltage is applied and a mirror operated by an applied signal voltage. The inclination angle of the thin film type AMA varies linearly with applied voltage and has almost instantaneous frequency response.

A conventional optical projection system using such a thin film type AMA as an optical path control device is shown in FIG.

Referring to FIG. 1, a conventional optical projection system 10 includes a light source 12, a source lens 14, a source stop 16, a mirror 18, and a modulation lens 20. , An AMA light modulator 22, a projection stop 24, a projection lens 28, and a screen 30. The projection stop 24 is an optically opaque member and has a front surface 25 which is an optically reflective surface and an aperture 26 formed to pass light rays. Preferably, the opening 24 is a pinhole or slit.

First, when the thin film type AMA module is automatically aligned with the optical projection system 10 and driven, the light emitted from the light source 12 such as a metal halide lamp is incident on the source lens 14 and then the source stop 16 Is irradiated onto the mirror 18 through the opening of the < RTI ID = 0.0 > The light beam irradiated onto the mirror 18 is incident on the modulation lens 20 after the optical path thereof is primarily changed.

Light rays passing through the modulation lens 20 are irradiated onto the AMA light modulator 22 with parallel light. The AMA light modulator 22 includes a plurality of reflecting surfaces, which are mounted on a piezoelectric actuator. The piezoelectric actuators actuate each reflecting surface in response to an electrical signal applied to each actuator, whereby light rays passing through the field lens 20 are reflected from the reflecting surface.

The light modulated by the AMA light modulator 22 is focused on the modulation lens 20 and irradiated onto the projection stop 24. Light rays incident on the front surface 25 of the projection stop 24 do not pass through the openings 26 but are totally reflected, and the light rays passing through the openings 26 are projected on the screen 30 by the projection lens 28. Projected to form an image.

However, according to the conventional AMA projection system as described above, in the process of the light emitted from the light source 12 is irradiated on the AMA light modulator 22 through the modulation lens 20, a part of the modulation lens ( Reflected from each side of 20). As such, the light rays reflected from each surface of the modulation lens 20 pass through the opening 26 of the projection stop 24 and are projected onto the screen 30 by the projection lens 28. In particular, when the screen 30 is in a dark state, that is, an OFF voltage, that is, a voltage of zero is applied to the piezoelectric actuator, the light beam reflected by the AMA light modulator 22 is projected to stop. Even when it is impossible to pass 112, the light reflected from each side of the modulation lens 20 is projected onto the screen 30 so that the ghost is concentrated on the left and right sides of the center on the screen 30 as shown in FIG. 2. The pattern 32 is distinctly formed.

Typically, the illuminance difference between the background and the ghost pattern is 6 to 7: 1 on the screen 30. As the brightness of the background is lower, the image of the ghost pattern is clearly detected. Since such ghost patterns act as noise, these ghost patterns must be eliminated in order to realize a reliable projection system.

Accordingly, an object of the present invention is to provide an optical projection system capable of eliminating ghost patterns caused by light reflection of the modulation lens surface in an optical projection system using an AMA module.

1 is a schematic diagram illustrating a conventional optical projection system.

FIG. 2 is a schematic diagram illustrating a ghost pattern caused by the optical projection system shown in FIG. 1.

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

4A is a schematic diagram showing a conventional ghost pattern.

4B is a graph showing the distribution of light intensity according to the x-x 'distance of FIG. 4A.

5A is a schematic view showing a plate for removing a ghost pattern according to the present invention.

FIG. 5B is a graph showing the distribution of light intensity according to the y-y 'distance of FIG. 5A.

Explanation of symbols for main parts of the drawings

10, 100 ... optical projection system 12, 102 ... light source

14, 104 ... source lens 16, 106 ... source stop

18, 108 ... mirror 20, 110 ... modulation lens

111 ... plate for removing ghost patterns

22, 112 ... AMA optical modulator 24, 114 ... projection stop

28, 118 ... projection lens 30, 120 ... screen

32 ... Ghost Pattern

The present invention to achieve the above object,

A light source for generating light rays;

An actuated mirror array (AMA) light modulator for modulating the light beam according to an applied electrical signal and changing its light path to project it on a screen;

A modulation lens for irradiating the light beam onto the actuated mirror array light modulator with parallel light;

A projection stop to focus the flux of light modulated by the actuated mirror array light modulator; And

A plate disposed between the modulation lens and the actuated mirror array light modulator, the plate for removing ghost patterns formed by the light rays reflected from each side of the modulation lens being projected on the screen through the projection stop; It provides an optical projection system.

As described above, the present invention arranges a ghost pattern removing plate between the modulation lens and the AMA light modulator in order to remove ghost patterns that appear concentrated on the left and right of the center on the screen. The ghost pattern removing plate is coated to have a low reflectivity in the region corresponding to the position where the ghost pattern is formed, and the remaining region is coated to have a high reflectance.

Therefore, since the intensity of the light projected at the position where the ghost pattern is formed on the screen is compensated for by the ghost pattern removing plate, there is almost no difference in illuminance between the background of the screen and the ghost pattern, thereby eliminating the ghost pattern. have.

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

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

Referring to FIG. 3, the optical projection system 100 according to the present invention includes a light source 102, a source lens 104, a source stop 106, a mirror 108, a field lens 110, and a ghost pattern removing plate. 111, an AMA light modulator 112, a projection stop 114, a projection lens 118, and a screen 120.

The light source 102 is a broadband source of optical energy, preferably using a metal halide lamp. The optical energy coming from the metal halide lamp 102 is the long wavelength infrared (LWIR), visible and ultraviolet (UV) light in the spectrum.

The source lens 104 performs a function of spectroscopy of light emitted from the light source 102 into parallel light. The source stop 106 is an optically opaque member and has an opening formed to allow light to pass therethrough. The source stop 106 functions to concentrate the flux of light that has passed through the source lens 104.

A mirror 108 is disposed after the source stop 106, which serves to primarily change the light path of the light rays emitted from the light source 102. The modulation lens 110 is disposed in front of the AMA light modulator 112, so that the light beam whose optical path is primarily changed by the mirror 108 can be irradiated onto the AMA light modulator 112 with parallel light without being lost. It serves to reduce the light path.

A ghost pattern removing plate 111 is disposed between the modulation lens 110 and the AMA light modulator 112. As shown in FIG. 5A, the ghost pattern removing plate 111 is coated so that a region corresponding to the ghost pattern has a low reflectance (denoted by-) and a remaining region is coated by a high reflectance (denoted by +). do. Preferably, the plate 111 is coated with a material such as MgF ₂ , SiO ₂ , Ti ₂ O ₃ .

The projection stop 114 is an optically opaque member and has a front surface 115 that is an optically reflective surface and an opening 116 formed to pass light rays. Preferably, the opening 116 is a pinhole or slit. The projection lens 118 projects a light beam passing through the opening 116 of the projection stop 114 on the screen 120 to display an image corresponding thereto.

The AMA light modulator 112 includes a plurality of reflective surfaces, which are mounted on piezoelectric actuators. The piezoelectric actuators actuate the respective reflecting surfaces in response to electrical signals applied to the respective actuators, so that light rays passing through the modulation lens 110 are reflected from the reflecting surfaces. The light rays reflected from each reflective surface are modulated by the flux of light rays passing through the opening 116 of the projection stop 114. The flux of the light beam is controlled by the direction of the reflective surface of the AMA light modulator 112 with respect to the opening 116.

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

First, the light rays emitted from the halogen metal lamp 102 are spectroscopically by the source lens 104 and then irradiated onto the mirror 108 through the opening of the source stop 106. The light beam irradiated onto the mirror 108 is incident on the modulation lens 110 after the optical path thereof is primarily changed. The light rays passing through the modulation lens 110 are irradiated onto the AMA light modulator 112 through the ghost pattern removing plate 111 as parallel light.

The light beam irradiated by the AMA light modulator 112 is modulated according to the electrical signal applied to the piezoelectric actuator of the AMA light modulator 112, and then passes through the ghost pattern removing plate 111 to the modulation lens 110. Is focused on and irradiated onto the projection stop 114.

If an OFF voltage, i.e. zero voltage, is applied to the piezoelectric actuator, the respective reflecting surfaces of the AMA light modulator 112 do not vibrate, tilt or bend, so that the light beam stops projection. The screen 120 becomes dark because it cannot pass through the 114.

However, when an ON voltage is applied to the piezoelectric actuator, the respective reflecting surfaces of the AMA light modulator 112 vibrate, tilt or bend, depending on the embodiment used. In this case, the degree of vibration, tilting or bending of the reflective surface of the AMA light modulator 112 is expressed as a change in light intensity at a corresponding point on the screen 120.

Here, the light beams modulated by the AMA light modulator 112 and focused on the modulation lens 110 after passing through the ghost pattern removing plate 111 are shown in FIG. 5B. The light intensity of the portion passing through the region corresponding to the position where the ghost pattern on the screen is formed is compensated.

4A is a schematic diagram showing a conventional ghost pattern, and FIG. 4B is a graph showing a distribution of light intensities according to the x-x 'distance of FIG. 4A. FIG. 5A is a schematic view showing a ghost pattern removing plate according to the present invention, and FIG. 5B is a graph showing the distribution of light intensity according to the y-y 'distance of FIG. 5A. 4B and 5B, the horizontal axis represents distance and the vertical axis represents light intensity. In addition, in FIG. 5B, the solid line shows the light intensity curve, and the dotted line shows the light intensity curve of the light ray passing through the ghost removal plate.

Referring to FIG. 4A, according to the conventional optical projection system as shown in FIG. 1, a ghost pattern 32 acting as noise on the left and right sides of the center on the screen 30 by light rays reflected from each surface of the modulation lens. Is formed. Since the ghost pattern is shown as the light intensity is increased in the area as shown in Figure 4B, the illuminance difference between the background and the ghost pattern occurs on the screen. This roughness difference is more pronounced when the screen is dark.

However, as shown in FIG. 5A, the region corresponding to the ghost pattern is coated to have a low reflectance (denoted by-) and the remaining region is coated to have a high reflectance (denoted by +). When disposed between the modulation lens 110 and the AMA light modulator 112, the intensity of the light beam passing through the region corresponding to the position where the ghost pattern on the screen among the light beams modulated by the AMA light modulator 112 is formed is low. You lose. Thus, as shown in FIG. 5B, the light intensity of the ghost pattern and the light intensity passing through the ghost pattern removing plate 111 are compensated for each other so that the difference in illuminance between the background and the ghost pattern on the screen 120 is eliminated. do.

As described above, the light beam whose light intensity is compensated by the ghost pattern removing plate 111 is focused on the modulation lens 110 and then directed to the projection stop 114. The light rays incident on the front surface 115 of the projection stop 114 do not pass through the opening 116 and are fully reflected, and the light rays passing through the opening 116 are reflected on the screen 120 by the projection lens 118. Projected to form an image.

Here, FIG. 3 illustrates a monochrome system using a single plate AMA light modulator, but according to another preferred embodiment of the present invention, a single plate AMA light modulator sequentially emits red, green, and blue light like a color wheel. The ghost pattern removing plate of the present invention can be applied to a single-plate color system that can display red, green and blue images by irradiation with.

Further, according to another preferred embodiment of the present invention, three AMA light modulators, namely R-AMA, G-AMA and B-AMA, which are arranged at different reflection angles to reflect red, green and blue light, respectively, The ghost pattern removal plate of this invention can be applied to the 3-plate color system used. In this case, the optical projection system comprises a plurality of mirrors for reflecting light rays emitted from the light source and passing through the source stop into red, green and blue light of different wavelengths, and the R-AMA, G-AMA and B-AMA. And an R-modulation lens, a G-modulation lens and a B-modulation lens respectively disposed in front of the light modulators. At this time, the ghost pattern removing plates of the present invention are disposed between the R-modulation lens and the R-AMA, the G-modulation lens and the G-AMA, and the B-modulation lens and the B-AMA, respectively.

As described above, the present invention arranges a ghost pattern removing plate between the modulation lens and the AMA light modulator in order to remove the ghost pattern appearing concentrated on the left and right of the center on the screen. The ghost pattern removing plate is coated to have a low reflectivity in the region corresponding to the position where the ghost pattern is formed, and the remaining region is coated to have a high reflectance.

Therefore, according to the optical projection system according to the present invention, since the intensity of light projected at the position where the ghost pattern is formed on the screen is compensated by the ghost pattern removing plate, the difference in illuminance between the background of the screen and the ghost pattern is different. Almost eliminated, eliminating ghost patterns.

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 (5)

A light source 102 for generating light rays; An actuated mirror array (AMA) light modulator (112) for modulating the light beam in accordance with an applied electrical signal and changing its light path to project on a screen; A modulation lens (110) for irradiating the light beam onto the actuated mirror array light modulator (112) with parallel light; A projection stop (115) for concentrating the flux of light modulated by the actuated mirror array light modulator (112); And Disposed between the modulation lens 110 and the actuated mirror array light modulator 112, and the light reflected from each side of the modulation lens 110 passes through the projection stop 115 and is projected onto the screen And a plate (111) for removing the ghost pattern is formed. The optical projection system of claim 1, wherein the plate 111 for removing the ghost pattern is coated to have a low reflectivity in an area corresponding to the ghost pattern, and to coat the remaining areas with a high reflectivity. . The optical projection system of claim 2, wherein the plate for removing the ghost pattern is coated with a material of MgF ₂ , SiO ₂ , or Ti ₂ O ₃ . The method of claim 1, wherein a source lens (104) for spectroscopy the light emitted from the light source (102), a source stop (106) for concentrating the flux of the light spectroscopy by the source lens (104), the source A plurality of mirrors 108 for reflecting the light beams passing through the stop 106 by wavelength, and a projection lens 118 for projecting the light beams passing through the projection stop 114 on the screen 120 Optical projection system, characterized in that. The optical projection system of claim 1, wherein the actuated mirror array light modulator (112) comprises R-AMA, G-AMA, and B-AMA for modulating the light beam by wavelength.