KR100358807B1 - A color-filter embedded projection system - Google Patents

Abstract

In a projection system that displays a large screen image by enlarging and projecting an image implemented by a reflective liquid crystal display, for the purpose of realizing a high brightness full-color screen with a simplified optical configuration,

A light source that emits white light, an optical filter that selectively transmits light in the visible wavelength range except ultraviolet and infrared light among white light, a polarizing beam splitter that separates incident light into S-polarized light and P-polarized light, and a polarizing beam S-polarized light is provided from the splitter, and a color filter layer is provided on one side of the liquid crystal layer to realize a full-color image by pixel-by-pixel driving of the liquid crystal, and is disposed on an optical path to selectively select light of a specific polarization axis. The present invention provides a projection system including a polarizing plate transmitting through and a projection lens system to enlarge and project an image implemented by a reflective liquid crystal display onto a screen.

Description

Projection system employing color filter {A color-filter embedded projection system}

The present invention relates to a projection system for displaying a large screen image by enlarging and projecting an image implemented by a liquid crystal display. More specifically, a color filter is provided inside the liquid crystal display to implement a high-brightness full-color screen with a simplified optical configuration. A projection system that can be.

In general, a liquid crystal on silicon (LCOS) among reflective liquid crystal displays is a liquid crystal cell formed on a semiconductor substrate, unlike a known liquid crystal display, and highly integrated components and driving circuits of each pixel. Since it can be arranged in a small size of about 1 inch, it is possible to realize a high resolution display of more than XGA (eXtended Graphics Array) class.

For this reason, the LCOS panel has attracted attention as an image realization device of the projection system, and the technology development and commercialization of the LCOS panel and the projection system using the same are being actively conducted.

The projection system implements a full-color screen by including three LCOS panels corresponding to R, G, and B light, and combining the R, G, and B images implemented by each LCOS panel into one. While the screen brightness is excellent, it is disadvantageous in terms of manufacturing cost due to the three LCOS panels, and has a disadvantage in that the optical system configuration is complicated.

In addition, a color shutter method and a hologram color filter method are known as a method of implementing a full-color screen with one LCOS panel, and US Pat. No. 5,999,282 discloses the hologram color filter method.

6 is a schematic diagram of a projection system to which a color shutter method is applied, wherein the color shutter 1 is disposed between an imaging lens 3 and a polarizing beam splitter (PBS) 5 and sequentially according to a control signal. It consists of three liquid crystal panels for R, G, and B which drive. In this way, the color shutter 1 sequentially converts the white light emitted from the light source 7 into R, G, B light and provides it to the LCOS panel 9.

The color shutter method is advantageous in terms of manufacturing cost due to its simple optical configuration, but has low screen brightness due to low light utilization efficiency, and the LCOS panel 9 must sequentially implement images corresponding to R, G, and B light. The disadvantage is that fast response speed is required.

FIG. 7 is a schematic diagram of a projection system employing a holographic color filter method, in which three dichroic mirrors 11 in which R, G, and B dichroic mirrors 11 are S-polarized white light in a polarization beam splitter 5 are shown in FIG. When the light is selectively reflected by the light of the B wavelength band, the polarization hologram 13 diffracts the R, G, and B light selectively into the respective R, G, and B pixel areas of the color filter 15 provided on the outer surface of the LCOS panel 9. To provide it to the LCOS panel 9.

In this manner, the three-color dichroic mirror 11, the polarization hologram 13, and the color filter 15 are implemented to realize a full-color screen. Although not only high precision optical alignment is required, but the overall system configuration is complicated, there are disadvantages in terms of productivity and manufacturing cost.

Accordingly, the present invention has been devised to solve the above problems, and an object of the present invention is to provide a projection system capable of realizing excellent screen brightness by improving light utilization efficiency than a conventional color shutter method.

Another object of the present invention is to provide a projection system that is advantageous in terms of productivity and manufacturing cost by easily realizing a full color while simplifying the optical configuration and driving method.

1 is a schematic diagram of a projection system according to the present invention.

2 is a cross-sectional view of a reflective liquid crystal display.

3 is a cross-sectional view of a reflective liquid crystal display according to another embodiment.

4 is a schematic diagram showing a detailed process of the pigment dispersion method.

5 is a schematic view showing a detailed process of the electrodeposition method.

6-7 are schematic views of a projection system according to the prior art.

In order to achieve the above object, the present invention,

A light source emitting white light,

An optical filter selectively transmitting light in a visible light wavelength band excluding ultraviolet and infrared rays among the white light;

A polarizing beam splitter for separating incident light into S-polarized light and P-polarized light,

A reflection type liquid crystal display receiving S-polarized light from the polarization beam splitter and including a color filter layer on one surface of the liquid crystal layer to realize a full-color image by driving pixels by liquid crystal;

A polarizing plate disposed on an optical path and selectively transmitting light of a specific polarization axis;

Provided is a projection system including a projection lens system to enlarge and project an image implemented by the reflective liquid crystal display on a screen.

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

1 is a schematic diagram of a projection system according to the present embodiment, in which a projection system reflects white light emitted from a light source 2 via an optical filter 4 and a plurality of optical lenses and a polarizing beam splitter 6. It is provided to the type liquid crystal display 8, and implements a large screen image by magnifying and projecting the image implemented by the reflective liquid crystal display 8 to a screen (not shown) through the projection lens system 10.

The light source 2 includes a parabolic reflector 12 on one surface so that the light emitted from the light source 2 is concentrated toward the optical filter 4, and the optical filter 4 is connected to the light source 2. Among the provided lights, infrared rays longer than the red color of visible light and ultraviolet rays shorter than the violet color of visible light are blocked to selectively transmit light in the visible range.

In addition, a pair of condenser lenses 14 and a polarization conversion system (PCS) 16 are provided on the front surface of the optical filter 4, and the polarization conversion system 16 is an unstable polarized light emitted from the light source 2. The light of the state is converted into a stable polarization state in which the reflective liquid crystal display 8 is advantageous for driving, and the imaging lens 18 located in front of the polarization conversion system 16 refracts the light passing through the polarization conversion system 16. It forms in the polarizing plate 20. FIG.

The polarizing plate 20 provided with the light through the imaging lens 18 selectively transmits the light oscillating in the same direction as its polarization axis, and the polarizing beam splitter 6 receives the light incident from the polarizing plate 20. It separates into S-polarized light and P-polarized light, and among them, S-polarized light with good reflection efficiency is provided to the reflective liquid crystal display 8.

The reflective liquid crystal display 8 receives S-polarized light to drive a liquid crystal pixel by pixel to provide a screen, and provides light incident by a built-in reflector (not shown) to the polarizing beam splitter 6 again. The image exiting the polarization beam splitter 6 is enlarged and projected onto the screen while passing through the projection lens system 10 in which a plurality of lenses are combined.

In this case, the reflective liquid crystal display 8 provided in the present embodiment includes a color filter layer therein to implement a full-color screen with white light provided from the light source 2. This allows the projection system to provide a full-color screen with the reflective liquid crystal display 8 itself, even if there is no separate coloration means such as a color shutter or dichroic mirror between the light source 2 and the reflective liquid crystal display 8. The implementation has the advantage that the optical configuration is much simpler.

FIG. 2 is a cross-sectional view of the reflective liquid crystal display according to the present embodiment, wherein the reflective liquid crystal display 8 forms a semiconductor integrated circuit 24 and a driving circuit as switching elements on the semiconductor lower substrate 22, It consists of an LCOS panel in which the upper substrate 28 is integrally combined with the lower semiconductor substrate 22 through the liquid crystal layer 26, and R, G, and B colors are given to each pixel on one surface of the liquid crystal layer 26. A color filter layer 30 is further included.

A transparent electrode 32 such as an indium tin oxide (ITO) film is formed on one surface of the upper substrate 28 facing the liquid crystal layer 26, and the lower semiconductor substrate facing the upper substrate 28. On one surface of the pixel 22, a reflective electrode 34 such as an aluminum film is formed for each pixel, and the transparent electrode 32 and the reflective electrode 34 are combined to form a pixel, each functioning as a common electrode and a pixel electrode. do.

In particular, the reflective electrode 34 is electrically connected to the semiconductor integrated circuit 24 provided for each pixel. More specifically, the semiconductor integrated circuit 24 includes a source 36 and a drain 38 formed in the semiconductor lower substrate 22. And the gate electrode 40 disposed therebetween, and the drain 38 is electrically connected to the reflective electrode 34 by the connection electrode 42, and the capacitor is adjacent to the gate electrode 40. 44 is disposed.

In addition, the gate electrode 40, the connection electrode 42, and the capacitor 44 are separated from each other by the insulating layer 46.

When the semiconductor integrated circuit 24 having such a configuration applies a signal to the reflective electrode 34, the reflective electrode 34 drives the liquid crystal molecules pixel by pixel together with the transparent electrode 32 to implement a predetermined image. . In this case, the image implemented by the reflective liquid crystal display 8 is colorized by the color filter layer 30 provided on one surface of the upper substrate 28 facing the liquid crystal layer 26 and directed to the polarization beam splitter 6.

The color filter layer 30 has a configuration in which R, G, and B dye films are formed for each pixel on one surface of the upper substrate 28 facing the liquid crystal layer 26, as shown in FIG. 3. As illustrated, R, G, and B dye films are formed for each pixel on one surface of the semiconductor lower substrate 22 facing the liquid crystal layer 26.

When the color filter layer 30 is formed on the upper substrate 28, the color filter layer 30 may be previously formed in a pixel area that will face the reflective electrode 34, for example, before the transparent electrode 32 is formed. For example, it may be produced by a pigment dispersion method.

As shown in FIG. 4, the pigment dispersion method coats a resist dye colored with R dye on a glass substrate 48, and forms a polyvinyl alcohol (PVA) film 52 thereon. After selectively curing a specific portion through the photo mask 54, the remaining uncured resist is developed to form an R dye film, and the B dye and the G dye process are repeated in the above-described process. It is a method of forming a G and B dye film.

When the color filter layer 30 is formed on the semiconductor lower substrate 22, the color filter layer 30 is formed on the surface of the reflective electrode 34 facing the liquid crystal layer 26, and may be manufactured by, for example, an electrodeposition method. have. At this time, an insulating film and an alignment film (not shown) are formed on the surface of the color filter layer 30.

In the electrodeposition method, as shown in FIG. 5, the transparent electrode 56 is formed on the glass substrate 48 at which the respective R, G, and B dye films are attached, the R dye is coated on the entire surface of the substrate, and then the R dye. When an electrodeposition voltage is applied to the transparent electrode 56 corresponding to the film, an R dye film is formed on the transparent electrode 56 to which the voltage is applied, and each of the transparent electrodes 56 is repeated by repeating the B dye and the G dye process. ) To form R, G and B dye films.

When the color filter layer 30 is formed on the semiconductor lower substrate 22 as described above, when the color filter layer 30 is manufactured by the electrodeposition method, the reflective electrode 34 is formed on the semiconductor lower substrate 22. The R, G, and B dye films may be formed on the reflective electrode 34 by applying an electrodeposition voltage directly to the reflective electrode 34 without the transparent electrode.

Of course, the color filter layer 30 may be formed by the electrodeposition method on the transparent electrode 32 in addition to the above-described method, and may be manufactured by other methods besides the electrodeposition method on the reflective electrode 34. In addition, each of the R, G, and B dye films included in the color filter layer 30 may be formed in various shapes such as a dot shape or a stripe shape corresponding to each pixel.

As described above, the color filter layer 30 is applied to the existing pigment dispersion method and the electrodeposition method as it is, one surface of the upper substrate 28 facing the liquid crystal layer 26 or one surface of the lower substrate 22 facing the liquid crystal layer 26. As such, it can be easily formed inside the reflective liquid crystal display 8.

As a result, the projection system having the reflective liquid crystal display 8 includes the reflective liquid crystal display 8 and the transparent electrode 32 or the reflective electrode 34 in which the color filter layer 30 constitutes each pixel. Directly formed on one side of the, the reflective liquid crystal display 8 realizes a full-color screen.

Therefore, the projection system provided by this embodiment has the following advantages.

First, as the reflective liquid crystal display 8 includes the color filter layer 30 therein, colorization means for separating white light into R, G, and B light between the light source 2 and the reflective liquid crystal display 8. This is not required. This simplifies the optical configuration and internal structure, which is advantageous for miniaturization design and fabrication.

Second, since the reflective liquid crystal display 8 receives the white light emitted from the light source 2 and full-colors it, it is possible to easily implement a high-resolution full-color screen without a precise optical system arrangement as compared to the hologram color filter method. . This improves work efficiency and improves productivity, which is advantageous for mass production.

Third, the light utilization efficiency is improved by about 2 times compared to the color shutter method, thereby effectively improving the brightness of the screen. Equations 1 and 2 below calculate the light utilization efficiency of the reflection type liquid crystal display driven by the color shutter method and the case where the built-in color filter is included, respectively, and compare the liquid crystal display having the same panel size and the number of pixels. In both cases, the polarization conversion efficiency of the liquid crystal mode itself is assumed to be the same.

Light utilization efficiency = aperture ratio (about 86%) × color filter efficiency (about 95/3%) × liquid crystal efficiency (about 88%) = about 24%

%) = About 14%

Here, the color filter method requires a pixel to be divided into three pixels of R, G, and B, so that the aperture ratio is lower than that of the color shutter method, but the liquid crystal efficiency is higher than that of the color shutter method requiring fast response speed. Since the efficiency is higher than the color shutter efficiency, the light utilization efficiency of the projection system according to the present embodiment shows a higher value than the conventional color shutter method.

Fourth, the burden on the reaction time of the liquid crystal is reduced compared to the color shutter method of sequentially providing the R, G, and B light to the reflective liquid crystal display, so that the production of the liquid crystal is facilitated and the manufacturing cost of the reflective liquid crystal display is reduced. You can.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

As such, by providing a highly sensitive color filter layer inside a reflective liquid crystal display provided by a known LCOS panel, the projection system according to the present invention can detect white light emitted from a light source without a separate colorizing means such as a color shutter or a dichroic mirror. The full-color screen can be realized in the reflective liquid crystal display itself.

This simplifies the optical configuration, which is advantageous for miniaturized design and manufacturing, and it is suitable for mass production by easily realizing high resolution full-color screen without precise optical arrangement, and improves the light utilization efficiency compared to the color shutter method. Color screen can be implemented.

Claims (6)

A light source emitting white light; An optical filter that selectively transmits light of visible light wavelength band except ultraviolet and infrared rays among the white light; A polarizing beam splitter for separating the incident light into S-polarized light and P-polarized light; A reflection type liquid crystal display receiving S-polarized light from the polarization beam splitter and including a color filter layer on one surface of the liquid crystal layer to implement a full-color image by pixel-by-pixel driving of the liquid crystal; A polarizer disposed on the optical path and selectively transmitting light of a specific polarization axis; And a projection lens system to enlarge and project an image implemented by the reflective liquid crystal display onto a screen. The liquid crystal display of claim 1, wherein A semiconductor lower substrate forming a semiconductor integrated circuit and a driving circuit; An upper substrate disposed opposite the lower semiconductor substrate and forming a transparent electrode on one surface of the lower semiconductor substrate; A liquid crystal layer disposed between the semiconductor lower substrate and the upper substrate; A reflective electrode electrically connected to the semiconductor integrated circuit and formed thereon to form a pixel in combination with a transparent electrode; And a color filter layer provided on one surface of the liquid crystal layer to impart respective R, G, and B colors to the plurality of pixels. The method of claim 2, And the color filter layer is formed in each pixel region between the upper substrate and the transparent electrode. The method of claim 2, And the color filter layer is formed on the reflective electrode facing the liquid crystal layer. The method of claim 4, wherein And the reflective electrode receives an electrodeposition voltage to form R, G, and B dye films on the surface thereof. The method of claim 1, And a polarization conversion system disposed between the optical filter and the polarization beam splitter and converting light of an unstable polarization state emitted from a light source into a stable polarization state advantageous for driving a reflective liquid crystal display.