KR100757115B1 - Reflective Optics in Projection Systems - Google Patents

Abstract

According to the present invention, a light source for generating white light; A dichroic mirror that transmits first light and reflects second and third light among the three color light components of the white light; A first beam splitter for polarizing separation by reflecting S waves of the first light and transmitting P waves; A second beam splitter for reflecting S-waves of two incident light beams and modulating the third light beams by P-waves and then transmitting them to perform color separation and polarization separation simultaneously; First to third reflective liquid crystal displays for reflecting the first to third light reflected or transmitted from the first and second beamsplitter; A quarter wave plate for modulating a waveform of first to third light incident on the first to third reflective liquid crystal displays; A third beam splitter for synthesizing the first to third lights reflected from the first to third reflective liquid crystal displays; And a projection lens for projecting the light synthesized by the third beam splitter to display an image on a screen, wherein the second and third incident light incident from the second beam splitter into the second and third reflective liquid crystal displays, respectively. There is provided a reflective optical device of a projection system in which the optical path lengths of light are formed differently.

According to the reflective optical device of the projection system according to the present invention, a path difference between light passing through the red reflective liquid crystal display panel and the green reflective liquid crystal display panel of the projection system is generated so that interference does not occur between the red light source and the green light source. It is effective.

Reflective optics, 1/4 wave plate, path difference

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 diagram showing a reflective optical apparatus of a projection system according to the present invention,

3 is an enlarged view of a red reflective liquid crystal display panel and a green reflective liquid crystal display panel in the reflective optical apparatus of the projection system according to the present invention;

4 is a cross-sectional view of the QWP used in the reflective optical device of the projection system according to the present invention;

5 is a path of light incident on the green reflective liquid crystal display panel in the reflective optical device of the projection system according to the present invention;

6 is a view illustrating a path of light incident on a red reflective liquid crystal display panel in the reflective optical apparatus of the projection system according to the present invention.

The reflective optical device of the projection system of the present invention, more specifically, the path difference between the light reflected from the green reflective liquid crystal display panel and the red reflective liquid crystal display panel in the reflective optical device of the projection system. The reflective optical device of the projection system to prevent the interference caused by.

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 display 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 and 24 provided between the display panels 15, 17 and 25 and the beam splitters 13, 19 and 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 reflective liquid crystal display panel, which is the first display panel 15, through the quarter wave plate 14. The signal incident on the first display panel 15 is reflected by the first display 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 polarized light. Through the conversion element 18, it is converted into a P wave. 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.

In addition, the green light source of the S-wave is transmitted through the first and second polarization conversion elements 11 and 12 to be incident on the first beam splitter 13 and reflected, and the second display is made through the quarter wave plate 16. It is incident (signal on) to the green reflective liquid crystal display panel (Green Panel) which is the panel 17. The light source reflected by the second display 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. Then, the second beam splitter 19 passes through and is formed on the screen through the projection lens 20.

On the other hand, the blue light source transmitted from the dichroic mirror 10 is P wave, and the second polarization conversion element 22 is converted into S wave, and the blue light source converted into S wave is reflected by the third beam splitter 23. And incident (signal on) to the blue reflective liquid crystal display panel (Blue panel) that is the third display panel 25 through the quarter-wave plate 24. S-waves incident on the third display 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 fourth polarization conversion elements ( 21 is converted into an S wave 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.

In such a three-plate LCoS optical engine, the green light source incident on the first beamsplitter 13 is reflected on the PBS plane, and the red light source is transmitted. Thereafter, the light is incident on the red reflective liquid crystal display panel and the green reflective liquid crystal display panel, and then reflected and met again. At this time, the PBS plane of the first beamsplitter reflects S-polarized light and transmits P-polarized light. In practice, however, light leaks when S-polarized light and P-polarized light cross the PSB plane. At this time, the geometry of the red reflective liquid crystal display panel and the green reflective liquid crystal display panel portion satisfies the Michelson interferometer structure. If the same path difference in the leaked beams is smaller than the interference distance (theoretically 100 μm), which is a distance at which a constant waveform is maintained, the light satisfies the interference condition and causes interference with each other.

The interference condition of light in which interference occurs with each other is as follows, and in the case of leakage beams of the green light source and the red light source, both conditions are satisfied.

1) The polarization states should be the same.

2) Both lights must be of the same single wavelength.

3) Both lights should have the same intensity.

That is, the incident light of the LCoS system is quasi-monochromatic light and has the same wavelength and polarization. In the LCoS system, the position of each display panel is determined by the automatic matching device with the most optimal focus performance. At this time, the position of each display panel is different from each other, and the distance difference between the red and green reflective liquid crystal display panels is smaller than the interference distance, thereby causing interference.

If the interference occurs in this way, an interference stripe is formed on the screen, which causes a problem that the image to be displayed on the screen is not properly displayed. Therefore, it is necessary to prevent the interference generated between the red light source and the green light source. There is.

In this case, the focal length of the display panel that is movable by red and green areas is very small as 4 micrometers, and even if only the red or green display panel is moved within the depth of focus range, there is a problem that the interference pattern cannot be removed.

The present invention has been made to solve the above problems, the reflection type having a structure to eliminate the interference generated between the red light source and the green light source without moving the display panel in the three-plate LCoS optical engine of the projection system It is an object to provide an optical device.

Reflective optical device according to the present invention for achieving the above object, the light source for generating white light; A dichroic mirror that transmits first light and reflects second and third light among the three color light components of the white light; A first beam splitter for polarizing separation by reflecting S waves of the first light and transmitting P waves; A second beam splitter for reflecting S-waves of two incident light beams and modulating the third light beams by P-waves and then transmitting them to perform color separation and polarization separation simultaneously; First to third reflective liquid crystal displays for reflecting the first to third light reflected or transmitted from the first and second beamsplitter; A quarter wave plate for modulating a waveform of first to third light incident on the first to third reflective liquid crystal displays; A third beam splitter for synthesizing the first to third lights reflected from the first to third reflective liquid crystal displays; And a projection lens for projecting the light synthesized by the third beam splitter to display an image on a screen, wherein the second light is incident from the second beam splitter into the second and third reflective liquid crystal displays, respectively. The optical path lengths of the third light are different from each other.

At this time, it is preferable that the thickness of the quarter wave plate adjacent to the second reflective liquid crystal display panel of the quarter wave plate is larger than the thickness of the quarter wave plate adjacent to the third reflective liquid crystal display panel.

Further, it is preferable that the thickness of the quarter wave plate adjacent to the second reflective liquid crystal display panel among the quarter wave plates is larger than the thickness of the quarter wave plate adjacent to the third reflective liquid crystal display panel by 0.033 mm or more. .

At this time, the first light is blue light, the second light is red light, and the third light is preferably formed of green light.

By having the structure as described above, the optical path difference between the green light source and the red light source is larger than the interference distance so that interference between the green light source and the red light source does not occur.

Hereinafter, a reflective optical apparatus of a projection system according to the present invention will be described with reference to the drawings.

2 is a view showing a reflective optical device of the projection system according to the present invention. In FIG. 2, in describing the reflective optical device of the projection system according to the present invention, the same reference numerals are used for the same components as in the prior art.

The reflective optical device of the projection system according to the present invention includes a light source for generating white light.

In front of the light source, a dichroic mirror is formed which transmits the first light and reflects the second and third light among the three color light components of the white light.

In front of the dichroic mirror, a first beam splitter for polarizing separation by reflecting S waves of the first light and transmitting P waves is formed.

In addition, a second beam splitter is formed on the side of the dichroic mirror. At this time, the second beamsplitter is configured to reflect the S-wave of the incident two light and modulate the third light to the P-wave and then transmit it to simultaneously perform color separation and polarization separation.

Outside the first and second beamsplitters, first to third reflective liquid crystal display panels for reflecting first to third light reflected or transmitted from the first and second beamsplitters are positioned.

At this time, between the first to third reflective liquid crystal display panel and the first and second beam splitter 1 for modulating the waveform of the first to third light incident to the first to third reflective liquid crystal display The / 4 wave plates are formed respectively. Accordingly, when the first to third lights enter the first to third reflective liquid crystal display panels, S waves are modulated to P waves and P waves to S waves.

Meanwhile, the first to third lights reflected from the first to third reflective liquid crystal display panels are synthesized in the third beam splitter, and the light synthesized by the third beam splitter is projected by the projection lens. The image is displayed on the screen.

At this time, in the reflective optical device according to the present invention, the optical path lengths of the second and third light incident from the second beam splitter to the second and third reflective liquid crystal displays are respectively different.

In order to form different optical path lengths of the second light and the third light as described above, more specifically, two quarter wave plates QWP disposed between the second and third reflective liquid crystal display panels and the second beam splitter : Quarter Wave Plate) has different thickness.

In the reflective optical device according to the preferred embodiment of the present invention, the second reflective liquid crystal display panel is formed of a red reflective liquid crystal display panel, and the third reflective liquid crystal display panel is formed of a green reflective liquid crystal display panel.

3 is a schematic view of a quarter wave plate installed in the red and green reflective liquid crystal display panels used in the reflective optical device according to the present invention.

As can be seen in Figure 3, in the reflective optical device according to the present invention, the quarter wave plate installed adjacent to the red reflective liquid crystal display panel is a quarter wave installed adjacent to the green reflective liquid crystal display panel. It is formed thicker than the thickness of the plate.

In this case, the quarter wave plate disposed adjacent to the red reflective liquid crystal display panel is not necessarily formed to be thicker than the thickness of the quarter wave plate disposed adjacent to the green reflective liquid crystal display panel, and vice versa. It is also possible that the thickness of the quarter-wave plate provided adjacent to the type liquid crystal display panel is thicker than the thickness of the quarter-wave plate provided adjacent to the red reflective liquid crystal display panel.

At this time, the configuration of the quarter wave plate is made by bonding glass having a predetermined thickness to the lower side of the QWP film, as shown in FIG. 4. At this time, by adjusting the thickness of the glass bonded to the QWP film, it is possible to prevent the interference generated between the green light source and the red light source.

That is, in the related art, since the 1/4 wavelength plate was formed to have the same thickness, the two optical path differences could not be more than the interference distance, but in the present invention, in order to form the two optical path differences more than the interference distance, 1 / The thickness between the four wave plates is to be formed differently.

At this time, in theory, if the optical path difference between the red light source and the green light source is 100 μm or more, the interference distance is out of range, and interference does not occur between the red light source and the green light source.

Therefore, the thickness difference between the minimum quarter wave plate for escaping the interference distance is as follows.

If 2 x (refractive index x thickness of 1/4 wavelength plate on red reflective liquid crystal display panel side-refractive index x thickness of 1/4 wavelength plate on green reflective liquid crystal display panel side) is formed at 100 µm or more, the interference distance will deviate. .

When the refractive index of the glass attached to the quarter wave plate is n = 1.518725,

Thickness of 1/4 wave plate on red reflective liquid crystal display panel side-Thickness of quarter wave plate on green reflective liquid crystal display panel side = 0.033 mm.

Therefore, if the difference between the "thickness of the 1/4 wavelength plate on the side of the red reflective liquid crystal display panel" and the "thickness of the 1/4 wavelength plate on the side of the refractive index x green reflective liquid crystal display panel" is 0.033 mm or more, the interference fringe can be removed. Can be.

In the reflective optical apparatus of the projection system according to the preferred embodiment of the present invention, the thickness of the quarter wave plate provided adjacent to the red reflective liquid crystal display panel is 1/4 installed adjacent to the green reflective liquid crystal display panel. It is formed to be 0.5mm thicker than the thickness of the wave plate.

This is a value determined in consideration of the productivity and manufacturing tolerances of the optical component, such that the thickness of the quarter wave plate may be variously modified.

One preferred embodiment of the reflective optical apparatus of the projection system according to the present invention configured so that the thickness difference between the 1/4 wavelength plate on the red reflective liquid crystal display panel side and the 1/4 wavelength plate on the green reflective liquid crystal display panel side is 0.5 mm. The optical path of the green light source and the optical path of the red light source according to the embodiment are illustrated in FIGS. 5 and 6.

Referring to FIG. 5, the optical path flowing from the first beam splitter of the green light source is OPL (Optical Path Length) = 2.0 + 0.55 * 1.518725 + 2.2 + 1.05 * 1.518725 + 0.1 = 6.72996 mm.

At this time, in the optical path of the green light source,

Iii) the distance between the first beam splitter and the quarter wave plate is 2 mm,

Ii) the thickness of the quarter wave plate is 0.55 mm,

1/4) the distance between the quarter wave plate and the green reflective liquid crystal display panel is 2.2 mm,

유리) The glass thickness formed on the green reflective liquid crystal display panel is 1.05mm,

Iii) The thickness of the liquid crystal layer is 0.1mm

Formed.

In addition, the optical path flowing from the first beam splitter of the red light source is OPL = 1.673489 + 1.05 * 1.518725 + 2.2 + 1.05 * 1.518725 + 0.1 = 6.72996 mm,

At this time, in the optical path of the red light source,

Iii) the distance between the first beam splitter and the quarter wave plate is 1.673489 mm,

Ii) the thickness of the quarter wave plate is 1.05 mm,

1/4) the distance between the quarter wave plate and the green reflective liquid crystal display panel is 2.2 mm,

유리) The glass thickness formed on the green reflective liquid crystal display panel is 1.05mm,

Iii) the thickness of the liquid crystal layer is 0.1mm

Formed.

Therefore, the optical path difference between a red light source and a green light source is 433.0 μm × 2 = 866 μm.

This is a value where the minimum condition of the interference distance deviates sufficiently from 100 μm.

According to such a configuration, it is possible to remove the interference fringes generated in the reflective optical device of the conventional projector system.

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, a path difference between light passing through the red reflective liquid crystal display panel and the green reflective liquid crystal display panel of the projection system is generated so that interference does not occur between the red light source and the green light source. It is effective.

Claims (8)

A light source generating white light; A dichroic mirror that transmits first light and reflects second and third light among the three color light components of the white light; A first beam splitter for polarizing separation by reflecting S waves of the first light and transmitting P waves; A second beam splitter for reflecting S-waves of two incident light beams and modulating the third light beams by P-waves and then transmitting them to perform color separation and polarization separation simultaneously; First to third reflective liquid crystal displays for reflecting the first to third light reflected or transmitted from the first and second beamsplitter; A quarter wave plate for modulating a waveform of first to third light incident on the first to third reflective liquid crystal displays; A third beam splitter for synthesizing the first to third lights reflected from the first to third reflective liquid crystal displays; And a projection lens configured to display the image on a screen by projecting the light synthesized by the third beam splitter. And the optical path lengths of the second and third light incident from the second beamsplitter to the second and third reflective liquid crystal displays are respectively different. The method of claim 1, Since the thickness of the quarter wave plate adjacent to the second reflective liquid crystal display among the quarter wave plates is greater than the thickness of the quarter wave plate adjacent to the third liquid crystal display, the optical path lengths of the second and third lights are reduced. Reflective optical device of a projection system, characterized in that formed differently. The method of claim 1, Among the quarter-wave plates, the thickness of the quarter-wave plate adjacent to the second reflective liquid crystal display is greater than or equal to 0.033 mm than the thickness of the quarter-wave plate adjacent to the third liquid crystal display. Reflective optical device of a projection system, characterized in that the furnace length is formed differently. The method of claim 1, The optical paths of the second and third light beams have a thickness of the quarter wave plate adjacent to the second reflective liquid crystal display of the quarter wave plate being 0.5 mm greater than the thickness of the quarter wave plate adjacent to the third liquid crystal display. Reflective optical device of a projection system, characterized in that the length is formed differently. delete The method of claim 1, Among the quarter-wave plates, the thickness of the quarter-wave plate adjacent to the third liquid crystal display is greater than or equal to 0.033 mm than the thickness of the quarter-wave plate adjacent to the second reflective liquid crystal display. Reflective optical device of a projection system, characterized in that the furnace length is formed differently. The method of claim 1, The light path of the second and third light beams is greater than the thickness of the quarter wave plate adjacent to the third reflective liquid crystal display among the quarter wave plates by 0.5 mm greater than the thickness of the quarter wave plate adjacent to the second liquid crystal display. Reflective optical device of a projection system, characterized in that the length is formed differently. The method of claim 1, And wherein the first light is blue light, the second light is red light, and the third light is green light.

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