KR100743290B1 - Reflective Optics in Projection Systems - Google Patents

Abstract

A reflective optical device of a projection system according to the present invention comprises: a dichroic mirror for color separation of an incident light source; First to third beam splitters for transmitting or reflecting the light source according to the incident direction of the light source; A first polarization conversion element and a second polarization conversion element disposed between the dichroic mirror and the first beam splitter to polarize the red and green light sources; First to third panels through which light sources transmitted or reflected by the first and third beam splitters are incident and reflected; A quarter wave plate disposed between the panel and the beam splitter; Third and fourth polarization conversion elements disposed between the first and second beam splitters and the second and third beam splitters; And a fifth polarization conversion element disposed between the second beam splitter and the projection lens to attenuate the reflected wave incident through the projection lens in a reverse path.

Projection System, Reflective Type, Optical Device, Polarization Device, Reflected Wave, Contrast

Description

Optical apparatus of reflection type in the projection system

1 is a block diagram showing a reflective optical device of a conventional projection system.

2 is a view showing a path of the reflected wave in the prior art FIG.

3 is a block diagram showing a reflective optical device of a projection system according to an embodiment of the present invention.

4 is a view showing a path of the reflected wave in FIG.

<Description of the symbols for the main parts of the drawings>

50 dichroic mirrors 51, 52, 58, 61, 62, 70 ...

53,59,63 ... beam splitter 54,56,64 ... 1/4 wave plate

55 ... Red panel 57 ... Green panel

65 Blue panel 60 Projection lens

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection optical system, and in particular to a reflective optical device of a projection system that can attenuate reflected waves reflected back from a projection lens to improve contrast.

Recently, the use of high resolution projectors and projections is increasing. In particular, as the commercialization of digital TV is imminent, the use of projection TV having a large screen with high resolution is increasing. Therefore, in order to realize a high resolution large screen, screen brightness has emerged as a very important variable.

In general, in the case of a three-panel type, a high light utilization efficiency and a vivid image can be realized, and thus a lot of attention is being focused on portable projector applications through a compact configuration. According to this trend, there is a strong demand for an optical system capable of realizing bright and clear images by maximizing light utilization efficiency while using the same lamp. Therefore, polarized light is used to express gray levels in a system using a transmissive high temperature poly or a reflective liquid crystal on silicon (LCoS) micro display.

1 is a view showing a reflective optical device of a conventional projection system.

1, a dichroic mirror 10 for color separation of a light source; First to third beam splitters 13, 19, and 23 for transmitting or reflecting according to the incident direction of the light source; A first polarization conversion element (11) and a second polarization conversion element (12) disposed between the dichroic mirror (10) and the first beam splitter (13); First to third panels 15, 17, and 25 through which light sources transmitted or reflected by the first and third beam splitters 13 and 23 are incident and reflected; Quarter-wave plates 14, 16, 24 provided between the panels 15, 17, 25 and the beam splitters 13, 19, 23; The first and second beam splitters 13 and 19 and the second and third beam splitters 19 and 23 are configured to include third and fourth polarization conversion elements 18 and 21.

Referring to the accompanying drawings, the reflective optical device of the conventional projection system is as follows.

Referring to FIG. 1, a dichroic mirror 10 separates colors of incident light sources. That is, red and green light sources (S waves) are reflected from the incident light source, and blue light sources (P waves) are transmitted.

The light source reflected by the dichroic mirror 10 is an S wave, and a red light source of the S wave is converted into a P wave in the first polarization converting element 11, and transmitted through the second polarization converting element 12 to be first. It is incident on the beam splitter 13. The P wave incident on the first beam splitter 13 is transmitted and incident (signal on) to the red panel which is the first panel 15 through the quarter wave plate 14. The signal incident on the first panel 15 is reflected by the first panel 15 and the quarter wave plate 14 to be converted into S-waves, and reflected by the first beam splitter 13, and thus the third polarization conversion element. Converted to P wave via (18). The red light source converted into P wave in the third polarization conversion element 18 passes through the second beam splitter 19 and is formed on the screen through the projection lens 20.

The green light source of the S wave passes through the first and second polarization conversion elements 11 and 12 and is incident and reflected on the first beam splitter 13, and the second panel passes through the quarter wave plate 16. It is incident (signal on) to the green panel (17). The light source reflected by the second panel 17 and the quarter wave plate 16 is converted into P waves, and transmitted through the first beam splitter 13, and the transmitted P waves are transmitted by the third polarization conversion element 18. The second beam splitter 19 passes through the projection lens 20 and is formed on the screen.

On the other hand, the blue light source transmitted from the dichroic mirror 10 is a P wave, and is converted into an S wave in the second polarization conversion element 62, and the blue light source converted into the S wave is reflected by the third beam splitter 23. And incident (signal on) to the blue panel, which is the third panel 25, through the quarter-wave plate 24. S-waves incident on the third panel 25 are reflected again and converted into P-waves through the quarter-wave plate 24 to pass through the third beam splitter 23, and the transmitted P-waves are the fourth polarization conversion element 21. Is converted into S-waves and reflected by the second beam splitter 19 to be formed on the screen through the projection lens 20.

The first to third beam splitters 13, 19, and 24 transmit P waves and reflect S waves, and the first polarization conversion element 11 is a red light source suppression layer, and the P waves are S waves. The S wave is converted into a P wave. The third polarization conversion element 18 is a suppression film of red and blue light sources, in which P waves are converted into S waves and S waves are converted into P waves. The fourth polarization conversion element 21 is a suppression film of a blue light source. P waves are converted into S waves, and S waves are converted into P waves.

However, in the reflective optical apparatus as shown in FIG. 2, the light sources passing through the projection lens 20, for example, the red and green light sources are reflected again (dashed lines), and the reflected light sources Rx and Gx are The reverse path is incident on the first panel (Red panel) or the second panel (Green panel) through the second beam splitter 19, the third polarization conversion element 18, the first beam splitter 13, respectively. The signal incident on each panel is reflected again. As such, the reflected wave traveling in the reverse path reduces contrast quantification, thereby causing an overall deterioration in image quality of the TV.

The present invention provides a reflective optical device of a projection system that attenuates reflected waves of projection lenses to improve chess contrast.

A first object of the present invention is to provide a reflection type optical device of a projection system that includes a polarization conversion element between a beam splitter and a projection lens to improve contrast ratio while removing reflected waves.

It is a second object of the present invention to provide a reflective optical device of a projection system including an achromatic lens between a beam splitter and a projection lens.

Reflective optical device of the projection system according to the present invention for achieving the above object,

A dichroic mirror for color separation of the incident light source;

First to third beam splitters for transmitting or reflecting the light source according to the incident direction of the light source;

A first polarization conversion element and a second polarization conversion element disposed between the dichroic mirror and the first beam splitter to polarize the red and green light sources;

First to third panels through which light sources transmitted or reflected by the first and third beam splitters are incident and reflected;

A quarter wave plate disposed between the panel and the beam splitter;

Third and fourth polarization conversion elements disposed between the first and second beam splitters and the second and third beam splitters;

And a fifth polarization conversion element disposed between the second beam splitter and the projection lens to attenuate the reflected wave incident through the projection lens in a reverse path.

Preferably, the fifth polarization conversion element converts the left circularly polarized light to the light source passing through the second beam splitter and converts the S-wave to the right circularly polarized light reflected from the projection lens to the second beam splitter.

Preferably, the fifth polarization conversion element is characterized in that the Achromatic lens (Achromatic lens).

Preferably, the chromatic lens is characterized in that the Achromatic quarter-wave plate (Achromatic QWP).

Hereinafter, with reference to the accompanying drawings as follows.

3 is a block diagram showing a reflective optical device of the projection system according to the present invention.

3, the dichroic mirror 50 for color separation of the light source; First to third beam splitters 53, 59, and 63 for transmitting or reflecting the light source according to the incident direction of the light source; A first polarization conversion element (51) and a second polarization conversion element (52) installed between the dichroic mirror (50) and the first beam splitter (53) to convert to desired polarizations; First to third panels 55, 57, and 65 through which light sources transmitted or reflected by the first and third beam splitters 53 and 63 are incident and reflected; Quarter wave plates 54, 56, 64 provided between the panels 55, 57, 65 and the beam splitters 53, 59, 63; Third and fourth polarization conversion elements 58 and 61 provided between the first and second beam splitters 53 and 59 and the second and third beam splitters 59 and 63; And a fifth polarization conversion element 70 provided between the second beam splitter 59 and the projection lens 60 to convert the reflected wave reflected from the projection lens into the S wave.

Referring to the accompanying drawings, the optical system of the projection system according to the embodiment of the present invention as described above is as follows.

Referring to FIG. 3, a dichroic mirror 50 separates colors of incident light sources. That is, red and green light sources (S waves) are reflected from the incident light source, and blue light sources (P waves) are transmitted.

The light source reflected by the dichroic mirror 50 is an S wave, and the red light source of the S wave is converted into a P wave in the first polarization conversion element 51, and passes through the second polarization conversion element 52 to pass through the first polarization conversion element 52. The light is transmitted through the beam splitter 53 and incident (signal on) to the red panel which is the first panel 55 through the quarter wave plate 54. The signal incident on the first panel 55 is reflected through the first panel 55 and the quarter wave plate 54 to be converted into S-waves, and reflected by the first beam splitter 53, so that the third polarization conversion element Converted to P wave via (58). The red light source converted into P wave in the third polarization conversion element 58 is transmitted through the second beam splitter 59. At this time, the P wave transmitted through the second beam splitter 59 is converted into left circularly polarized light by the fifth polarization conversion element 70 and is formed on the screen through the projection lens 60. Here, the second beam splitter 59 sums and outputs the R / G / B color signals incident on different paths.

In addition, the green light source of the S-wave reflected by the dichroic mirror 50 passes through the first and second polarization conversion elements 51 and 52 and is incident and reflected by the first beam splitter 53. The green light source enters (signals on) the green panel which is the second panel 57 through the quarter wave plate 56. The light source reflected by the second panel 57 and the quarter-wave plate 56 is converted into P-waves and transmitted through the first beam splitter 53, and the transmitted P-waves are transmitted by the third polarization conversion element 58. As a result, the second beam splitter 59 is transmitted. At this time, the P wave transmitted through the first beam splitter 59 is converted into left circularly polarized light by the fifth polarization conversion element 70, and is formed on the screen through the projection lens 60.

On the other hand, the blue light source transmitted from the dichroic mirror 50 is a P wave, and is converted into an S wave in the second polarization conversion element 62, and the blue light source converted into the S wave is reflected by the third beam splitter 63. Then, the light is incident (signal on) to the blue panel, which is the third panel 65, through the quarter wave plate 64. S-waves incident on the third panel 65 are reflected again and converted into P-waves through the quarter-wave plate 64 to pass through the third beam splitter 63, and the transmitted P-waves are the fourth polarization conversion element 61. Is converted into an S wave and reflected by the second beam splitter 59. At this time, the S-waves reflected by the second beam splitter 59 pass through the fifth polarization conversion element 70 and are converted into left circularly polarized light, and are formed on the screen through the projection lens 60.

In addition, the first to third beam splitters 53, 59, and 63 have characteristics of transmitting P waves and reflecting S waves, and the first polarization conversion element 51 is a red light source suppression film. The wave is converted into an S wave, and the S wave is converted into a P wave. The third polarization conversion element 58 is a suppression film of red and blue light sources, in which P waves are converted into S waves and S waves are converted into P waves. The fourth polarization conversion element 61 is a blue light source suppression film, in which P waves are converted into S waves and S waves are converted into P waves. Further, the first to third panels 55, 57 and 65 are preferably reflective liquid crystal panels.

In addition, the fifth polarization conversion element 70 converts the P wave transmitted from the second beam splitter 59 into left circularly polarized light, and converts right circularly polarized light, which is a light source reflected by the reverse path through the projection lens 60, into S wave. give. The fifth polarization conversion element 70 is an achromatic lens, and the achromatic lens is a lens for correcting chromatic aberration of two colors. For example, the fifth polarization conversion element 70 is formed of an AQWP. .

The fifth polarization conversion element 70 converts the reflected wave, which is the right circularly polarized light incident in the reverse path, into an S wave, so that the light source reflected through the projection lens 60 as shown in FIG. The green light sources Rx and Gx are changed into S waves in the right circularly polarized signal, thereby being reflected without being transmitted by the second beam splitter 59. The S-waves reflected by the second beam splitter 59 are transmitted by the fourth polarization conversion element 61 and reflected by the third beam splitter 63. Accordingly, it is possible to solve the problem that the light source reflected from the projection lens is incident back to the panel (eg, red panel, green panel), and as a result, attenuates the reflected wave, thereby improving the chess contrast.

So far, the present invention has been described with reference to the preferred embodiments, and those skilled in the art to which the present invention pertains to the detailed description of the present invention and other forms of embodiments within the essential technical scope of the present invention. Could be implemented. Here, the essential technical scope of the present invention is shown in the claims, and all differences within the equivalent range will be construed as being included in the present invention.

According to the reflective optical device of the projection system according to the present invention, the light source reflected from the projection lens in the reverse path is subjected to polarization conversion and then reflected in another path, thereby improving chess contrast through attenuation of the reflected wave. It works.

Claims (4)

A dichroic mirror for color separation of the incident light source; First to third beam splitters for transmitting or reflecting the light source according to the incident direction of the light source; A first polarization conversion element and a second polarization conversion element disposed between the dichroic mirror and the first beam splitter to polarize the red and green light sources; First to third panels through which light sources transmitted or reflected by the first and third beam splitters are incident and reflected; A quarter wave plate disposed between each panel and the beam splitter; Third and fourth polarization conversion elements disposed between the first and second beam splitters and the second and third beam splitters; And a fifth polarization conversion element disposed between the second beam splitter and the projection lens to attenuate the reflected wave incident through the projection lens in a reverse path. The fifth polarization conversion element is an achromatic quarter-wave plate that converts the left circularly polarized light to the light source passing through the second beam splitter and converts the S circular wave to the right circularly polarized light reflected from the projection lens to the second beam splitter. Reflective optical device of the projection system, characterized in that. delete delete delete

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