JPH06202066A - Image display device and projection display device with color separating device - Google Patents

Abstract

PURPOSE:To provide the image display device which has a high light utilization efficiency and provides color separation or color composition of, specially, high color purity by designing a dichroic surface so that a specific polarized light is separated into color lights. CONSTITUTION:The light emitted from a white light source 1 through a reflector 2 is in an unpolarized state and separated by a polarization beam splitter 3 into a light containing a P-polarized component much and a light containing an S-polarized component much, so that the light containing the S-polarized component much is guided to a color separation system. Then, the light is separated by dichroic mirrors 4 and 5 of a color separation system into color light components, but the light is guided to a liquid crystal panel 9 while the plane of polarization is maintained as the S-polarized component. The polarized state of a light passed through a total reflecting mirror 8 is also held as well. The transmitted light is converted into an S-polarized light again by a lambda/2 optical phase plate 11 on the projection side of the liquid crystal panel 9 and guided to the color composition system. The color light components are multiplexed by dichroic mirrors 6 and 7 of the color composition system and the polarization directions are held as the S-polarized component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device and a projection display device having a color separation device or a color synthesis device.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional example of a liquid crystal projector which projects a color image by using a plurality of liquid crystal panels.

Reference numeral 9 is a liquid crystal panel of TN type or the like for forming image light corresponding to each color of RGB, 1 is a white light source such as a metal halide lamp, and 2 is a liquid crystal panel 9 which effectively emits light emitted from the white light source 1. A parabolic reflector 12 for guiding the light to the filter 12 is a filter that cuts ultraviolet light and infrared light included in white light.

The white light from the light source 1 is separated by the first dichroic mirror 4 into a first color light (for example, G) and second and third color lights (for example, R and B), and further, a second dichroic mirror. At 5, the light is separated into the second color light and the third color light. Reference numeral 8 denotes a total reflection mirror that reflects the first color light. The respective color lights are respectively modulated by the liquid crystal panel 9, color-synthesized by the third dichroic mirror 6 and the fourth dichroic mirror 7, and projected on the screen 15 by the projection lens 14. Reference numeral 8 is a total reflection mirror that reflects the third color light, and 13 is a condenser lens that collects the illumination light reaching each liquid crystal panel on the pupil of the projection lens on the liquid crystal panel side.

Here, although not shown, each liquid crystal panel 9
Polarization filters whose polarization directions are orthogonal to each other are placed in front of and behind. The polarization filter on the incident side of the panel is a polarizer for converting the illumination light from the light source 1 into polarized light, and the polarization filter on the emission side cuts the light whose polarization direction does not rotate even though it passes through the liquid crystal panel. It is a photon.

[0006]

However, conventionally, since the unpolarized light from the light source 1 is incident on each dichroic mirror, the color separation characteristic of the dichroic mirror is P.
Since the polarization component and the S polarization component are different, there is a drawback that the polarization state after passing through the dichroic mirror differs depending on the wavelength.

[0007]

The present invention has been made to solve the above problems, and the present invention provides a light source, a dichroic surface for separating light from the light source into a plurality of color lights, and In an image display device having a color image forming means for forming an image by modulating predetermined polarized light provided in the optical paths of a plurality of colored lights, the dichroic surface separates the predetermined polarized light into the colored light. It is characterized by being designed.

[0008]

FIG. 1 is a diagram showing an embodiment of the present invention, in which 9 is an RG.
B A liquid crystal panel such as a TN type that displays a monochrome image corresponding to each color, 1 is a white light source such as a metal halide lamp, and 2 is a parabola for effectively guiding the light emitted from the white light source 1 to the liquid crystal panel 9. A surface-shaped reflector, 3 is a polarization beam splitter for separating the light from the white light source 1 into a pair of polarized lights having different polarization states, 12 is a filter for cutting ultraviolet rays and infrared rays contained in the white light, 4 is a A first dichroic mirror for separating white light into a first color light (for example, R) and a second, third (for example, G.B) color light, and 5 is a second color light and a third color light. Second dichroic mirror for, 8 is the first,
A total reflection mirror that reflects the third color light, 6 is a third dichroic mirror for combining the first color light and the second color light, and 7 is a combination of the first, second color light and the third color light A fourth dichroic mirror for projecting, a projection lens 14 for projecting the combined liquid crystal panel image on the screen, and a condenser lens 13 for converging the illumination light reaching each liquid crystal panel on the panel side pupil of the projection lens. Reference numeral 10 is a polarizing filter, and 11 is a phase plate.

The polarization filter 10 is placed in front of and behind each liquid crystal panel 9 so that the directions of polarization of the transmitted light are orthogonal to each other. The polarization filter on the incident side of the liquid crystal panel 9 is a polarizer that polarizes the illumination light. The polarization filter on the emission side is an analyzer that cuts light whose polarization direction has not rotated even after passing through the liquid crystal panel 9. In the case of this embodiment, since the polarization beam splitter 3 is provided, the polarization filter on the incident side has the effect of further increasing the polarization ratio of the light substantially polarized by the polarization beam splitter 3.

The optical axis of the projection lens 14 is arranged perpendicular to the display surface of the liquid crystal panel 9 and vertically shifted with respect to the center of the liquid crystal panel 9. As a result, the projection image is projected above the optical axis of the projection lens 14. As shown in FIG. 2, it is assumed that the liquid crystal panel 9 of this embodiment is of a type in which the alignment direction of liquid crystal molecules is oriented at 45 degrees with respect to the edge of the liquid crystal panel 9, and the polarized light is polarized before and after the liquid crystal panel. A phase plate 11 for adjusting the direction is arranged.

The polarization beam splitter 3 uses a well-known principle that the reflectance of light incident on a medium having a different refractive index at an angle is different depending on the polarization direction. , P component (light component that vibrates in the direction of the paper surface) and a large amount of S component (light component that vibrates in the direction perpendicular to the paper surface) are separated. If necessary, a dielectric film may be deposited on the surface of the parallel plate.

The present embodiment is an example of a configuration in which all the light incident on each dichroic mirror is set to S-polarized light, and the polarization state of the light from the light source 1 to the projection lens 14 will be described with reference to FIGS. 3 and 4. .

The light emitted from the white light source 1 through the reflector 2 is in a non-polarized light state, which is indicated by a spiral arrow in the figure. Next, the polarization beam splitter 3 causes the light containing a large amount of the P-polarized component and the light containing a large amount of the S-polarized component (in FIG.
(Indicated by a double circle) and light containing a large amount of S-polarized component is guided to the color separation system. The light is separated into color light components by the color separation type dichroic mirrors 4 and 5, but at that time, the polarization plane is guided to the liquid crystal panel 9 while being kept in the S polarization component. Similarly, the polarization state of the light passing through the total reflection mirror 8 is maintained.

FIG. 4 is a diagram showing the polarization states before and after the liquid crystal panel 9, and the light incident as substantially S-polarized light is substantially coincident with the alignment direction on the incident side of the liquid crystal panel 9 by the λ / 2 optical phase plate 11. The polarization filter 1 is converted into linearly polarized light that vibrates in a direction of 45 degrees with respect to the edge of the liquid crystal panel 9 (indicated by a downward arrow in the drawing, and hereinafter referred to as a first 45 degree direction).
It is incident on 0. The polarization filter 10 is configured to transmit only the light in the first 45-degree direction that matches the alignment direction on the incident side of the liquid crystal panel 9, and here, except the polarization component of the incident light in the first 45-degree direction. When the polarized light component of is present, it is cut. In the liquid crystal panel 9, the light is polarized light whose polarization direction is rotated by approximately 90 degrees in accordance with an image signal (indicated by an upward arrow in the figure, and hereinafter referred to as a second 45-degree direction) and the first polarization direction does not change. The polarized light of 45 degrees is selected. The polarization filter 10 placed on the exit side of the liquid crystal panel 9 has its transmission direction aligned with the second 45 ° direction, and only the light whose polarization direction is rotated by the liquid crystal is transmitted.
Other polarization components are absorbed.

The transmitted light is again converted into S-polarized light by the λ / 2 optical phase plate 11 placed on the emission side of the liquid crystal panel 9 and guided to the color combining system. The color light components are combined by the dichroic mirrors 6 and 7 of the color combining system, but the polarization direction is kept at the S polarization component at that time. Total reflection mirror 8
Similarly, the polarized state is maintained for the light passing through. As a result, all the light that forms a color image has the S polarization direction after being combined and is emitted from the projection lens 14.

Although the reflected light from the polarization beam splitter 3 is used in this embodiment, the transmitted light may be guided to the color separation system. In this case, since the transmitted light is light containing a large amount of P-polarized component, it is converted to light containing a large amount of S-polarized component by disposing a λ / 2 optical phase plate after passing through the polarization beam splitter 3 or as shown in FIG. A similar configuration can be realized by making all the P-polarized light incident on the dichroic mirror. It is also possible to arrange the λ / 2 optical phase plate after synthesizing the light in the color synthesizing system so that all the emitted light, that is, the image light is made into the P-polarized light.

However, since the wavelength of the boundary for color separation in the dichroic mirror is different between P-polarized light and S-polarized light, it is important to design the dichroic film in consideration of the difference.

The polarization beam splitter 3 may be of prism type. Further, in FIG. 1, the optical axis of the projection lens passes through the center of the liquid crystal panel and coincides with the optical axis of the reflector 2. However, the liquid crystal panel is shifted with respect to the optical axis of the projection lens, and the optical axis of the reflector is changed. You may incline and set with respect to a liquid crystal panel.

FIG. 6 shows a further embodiment.

Reference numeral 29 is a liquid crystal panel such as a TN type which displays a monochrome image corresponding to each color of RGB, 21 is a white light source such as a metal halide lamp, 22 is a light source for effectively guiding the light emitted from the white light source 1 to the liquid crystal panel 29. , For example, a reflector having a parabolic shape, 23 is a polarization beam splitter for separating the light from the white light source 1 into a pair of polarized lights having different polarization states, and 32 is for cutting ultraviolet rays and infrared rays contained in the white light. Filter, 24 is white light for the first color light (eg R) and second, 3 (for example G · B)
The first dichroic mirror for separating the colored light of
Reference numeral 25 is a second dichroic mirror for separating the second color light and the third color light, 28 is a total reflection mirror for reflecting the first and third color lights, and 26 is the first color light and the second color light. A third dichroic mirror for combining, 27 is a fourth dichroic mirror for combining the first and second color lights and a third color light, and 34 is a projection for projecting the combined image of the liquid crystal panel on the screen. A lens, 33 is a condenser lens for condensing the illumination light reaching each liquid crystal panel on the panel side pupil of the projection lens, 30 is a polarization filter, 31 is a phase plate, and 35 is the light separated by the polarization beam splitter 23. Of these, a reflection mirror such as a concave mirror has a function of returning light that is not guided to the color separation system to the direction of the lamp again.

The polarization filter 30 is placed in front of and behind each liquid crystal panel 29 so that the directions of polarization of the transmitted light are orthogonal to each other. The polarization filter on the incident side of the liquid crystal panel 29 is a polarizer that polarizes the illumination light. The emission side polarization filter is an analyzer that cuts the light whose polarization direction has not rotated even after passing through the liquid crystal panel 29. In the case of the present embodiment, since the polarization beam splitter 23 is provided, the polarization filter on the incident side has the effect of further increasing the polarization ratio of the light substantially polarized by the polarization beam splitter 23.

The optical axis of the projection lens 34 is arranged perpendicular to the display surface of the liquid crystal panel 29 and vertically shifted with respect to the center of the liquid crystal panel 29. As a result, the projection image is projected above the optical axis of the projection lens 34. Figure 7
As shown in, the liquid crystal panel 29 of this embodiment is assumed to be of a type in which liquid crystal molecules are aligned in a direction parallel to the edges of the liquid crystal panel 29.

In the polarization beam splitter 23, a plurality of glass plates, each having a vapor deposition film having a characteristic that the reflectance of light incident at an angle varies depending on the polarization direction, are arranged at intervals, and P
The light is separated into light containing a lot of components (light components vibrating in the direction of the paper) and light containing a lot of S components (light components vibrating in the direction perpendicular to the paper).

The function of this embodiment will be briefly described. The S-polarized light reflected by the polarization beam splitter 23 is transmitted through the dichroic mirror 24 as the first color light and reflected as the second and third color lights, and the first color light is transmitted through the total reflection mirror 28 and the polarization filter 30. It is incident on the liquid crystal panel 29. Then, it goes to the color synthesizing system through the polarization filter 30 which is an analyzer.

The second and third color lights are λ / 2 optical phase plate 31.
Is converted into P-polarized light, and the second color light is reflected by the dichroic mirror 25, and the third color light is transmitted. And the second
Is converted into S-polarized light by the λ / 2 optical phase plate 31,
It goes to the color synthesis system through the polarization filter 30, the liquid crystal light valve 29, and the polarization filter 30. On the other hand, the third color light is converted into S-polarized light through the λ / 2 optical phase plate 31, and becomes P-polarized light having image information through the polarization filter 30, the liquid crystal light valve 29, and the polarization filter 30, and λ / 2. It is converted into S-polarized light by the optical phase plate 31 and goes to the color combining system.

The first and second color image lights are combined by the dichroic mirror 26, converted into S-polarized light by the λ / 2 optical phase plate 31, and further dichroic mirror 27.
And is combined with the third color image light to be projected by the projection lens.

Although the light is almost polarized by the polarization beam splitter 23, the polarization ratio can be further increased by the polarization filter provided on the incident side of each liquid crystal light valve.

In this embodiment, in each dichroic surface,
S-polarized light is made incident on a dichroic mirror that reflects two color lights of RGB and one color light is transmitted, that is, P that is reflected on a dichroic mirror that reflects a broad band light. Another feature is that it is configured to allow polarized light to enter.

This is because when it is desired to reflect light in a wider band on the dichroic surface, S-polarized light is more efficient than P-polarized light and can be designed easily.
When the two colors of light are separated or combined, the light to be reflected is in a relatively narrow band, so it is easy to reflect it. This is based on the fact that P-polarized light has higher efficiency when given priority.

That is, in the present embodiment, in consideration of the band of light reflected by the dichroic surface, the transmission characteristic (efficiency) of light transmitted through the dichroic surface, the dichroic characteristic with respect to the polarization direction, the most efficient and highly pure color is obtained. It is a structure that can be disassembled. In this embodiment, when light is incident on the liquid crystal panel, it is set so as to be S-polarized light in accordance with the alignment direction of the liquid crystal panel used, but as shown in the embodiment of FIG. It goes without saying that a liquid crystal panel having a degree-of-direction alignment direction can also be used.

The reflection mirror 35 may be a plane mirror or a corner cube.

In each of the above embodiments, an example of an apparatus having a single light source and a single projection lens has been described. However, even when a plurality of light sources and a single projection lens are used, a single light source and a plurality of projection lenses are used. The present invention can be implemented as long as it is an apparatus having a color separation system or a color combination system, even when combining lenses, and also when combining a plurality of light sources and a plurality of projection lenses.

In the present invention, polarized light does not necessarily have to be incident on the color separation type dichroic mirror, and it may be incident as it is as unpolarized light and polarized light by a polarizing filter in front of the liquid crystal light valve. FIG. 8 is a graph showing characteristics when light is incident on the blue reflection dichroic mirror.
The solid line shows the case where non-polarized light is made incident, the long broken line shows the case where P polarized light is made incident, and the short broken line shows the case where S polarized light is made to enter. It can be seen that it is preferable to make the dichroic surface be incident with P- or S-polarized light in order to have a sharp spectral cut characteristic on the dichroic surface and increase the purity of the color light. However, even if unpolarized light is incident and the spectral cut characteristic is not sharp, that is, the color purity is not very good, if only the P or S polarized light is taken out by the polarizing filter in front of the liquid crystal light valve, P or S on the dichroic surface This is the same as when S-polarized light is incident. However, the wavelength of the boundary for color separation between P-polarized light and S-polarized light is shifted.

Therefore, when designing the dichroic film, even if unpolarized light is incident on the dichroic mirror, it is necessary to design the dichroic film so that a preferable wavelength becomes a boundary with respect to the polarization direction incident on the liquid crystal light valve. It will be good.

[0035]

As described above, the light source, the dichroic surface for separating the light from the light source into a plurality of color lights, and the predetermined polarized light provided in the optical paths of the plurality of color lights are used to modulate the image. In the image display device having a color image forming means for forming, since the dichroic surface is designed to separate the predetermined polarized light into the color light,
Regardless of the polarization state of the light incident on the dichroic surface, the color light incident on the color image forming means has a very high color purity, and an image display device with high light utilization efficiency can be realized.

[Brief description of drawings]

FIG. 1 is an embodiment of a projection display device of the present invention.

FIG. 2 is a diagram showing an alignment direction of a liquid crystal panel used in the embodiment of FIG.

FIG. 3 is a diagram showing the polarization direction of light in the embodiment of FIG.

4 is a diagram showing the polarization direction of light in the vicinity of the liquid crystal panel of the embodiment of FIG.

FIG. 5 is another embodiment of the projection display device of the present invention.

FIG. 6 is another embodiment of the projection display device of the present invention.

7 is a diagram showing an alignment direction of a liquid crystal panel used in the embodiment of FIG.

FIG. 8 shows characteristics when light is incident on a blue reflection dichroic mirror.

FIG. 9 is a conventional projection display device.

[Explanation of symbols]

1, 21 White light source 2, 22 Reflector 3, 23 Polarizing beam splitter 4, 5, 6, 7, 24, 25, 26, 27 Dichroic mirror 8, 28 Total reflection mirror 9, 29 Liquid crystal panel 10, 30 Polarizing filter 11, 31 Phase Plate 12, 32 UV Infrared Cut Filter 13, 33 Condenser Lens 14, 34 Projection Lens

Claims (11)

[Claims] 1. A light source, a dichroic surface that separates the light from the light source into a plurality of color lights and has different wavelengths that are separated according to the polarization state of the light, and a predetermined polarized light provided in an optical path of the plurality of color lights. An image display device having a color image forming means for forming an image by modulating
The image display device, wherein the dichroic surface is designed to separate the predetermined polarized light into the colored light. 2. The light incident on the dichroic surface is elliptically polarized light containing a large amount of the predetermined polarized light, and a polarizing plate is provided on the light incident side of the color image forming means. Image display device. 3. The image display device according to claim 1, wherein the light incident on the dichroic surface is non-polarized light, and a polarizing plate is provided on the light incident side of the color image forming unit. 4. A light source, a dichroic surface that separates the light from the light source into a plurality of color lights, the wavelengths of which are different according to the polarization state of the light, and a predetermined polarized light provided in the optical paths of the plurality of color lights. In a projection display device having a color image forming means for forming an image by modulating a color image and a projecting means for projecting a color image through the color image forming means, the dichroic surface has the predetermined polarized light as the color light. A projection display device characterized by being designed to be separated into two parts. 5. The projection means has a single projection lens, and has a dichroic surface for combining the color images between the projection lens and the color image forming means. 5. The projection display device according to claim 4, wherein is designed to color-synthesize the predetermined polarized light. 6. The color image forming means is a liquid crystal panel having an alignment direction different from the polarization direction of the polarized light, and an optical phase plate is arranged on at least one of an incident side and an emitting side of the liquid crystal panel. The projection display device according to claim 4, wherein: 7. A color separation device having a dichroic surface for color separation with a predetermined wavelength as a boundary, when polarized light is incident, color separation is performed on the polarized light with the predetermined wavelength as a boundary. A color separation device characterized by being designed into. 8. The light from the light source is converted into three primary colors of red, green, and
A color having a first dichroic surface that transmits one color of blue and reflects the other two colors, and a second dichroic surface that transmits one color of the two reflected colors and reflects the other one color In the decomposing device, S-polarized light is made incident on the first dichroic surface, and P-polarized light is made incident on the second dichroic surface. 9. A phase plate for converting the S-polarized light reflected by the first dichroic surface into P-polarized light is provided between the first dichroic surface and the second dichroic surface. The color separation device according to claim 8. 10. The light of each of the three primary colors, red, green and blue,
A first dichroic surface that reflects the first color light of the three primary colors, transmits the second color light, and performs color combination; and the first and second dichroic surfaces.
A second dichroic surface for reflecting color light and transmitting a third color light for color combination;
A color synthesizing device characterized in that light is incident on the dichroic surface with P-polarized light and on the second dichroic surface with S-polarized light. 11. The first dichroic surface and the second dichroic surface.
The color separation device according to claim 10, wherein a phase plate that converts the P-polarized light that has passed through the first dichroic surface into S-polarized light is provided between the dichroic surface and the dichroic surface.