JPH09330036A - Projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To illuminate each light valve with the same luminance and to obtain a bright full-color projected image free from irregularities in the image by making the length of an optical path between a light source and a light valve for a luminance signal equal to the length of an optical path between the light source and a light valve for a color signal. SOLUTION: Light source light emitted from the light source 1 in a direction +X is made incident on a polarized beam splitter(PBS) 2. In the PBS 2, the light source light is separated by a polarizing/separating part so as to become P-polarized light which is transmitted through the PBS 2 and emitted in the direction +X and S-polarized light which is reflected by the PBS 2 in a direction +Y, then, both of P-polarized light and S-polarized light are emitted from the PBS 2 in directions orthogonal to each other. The P polarized light emitted by the PBS 2 in the direction +X goes toward a direction +Z through a mirror 3, then, the light is made incident on the light valve for a color signal 5, thereafter, the light is made incident on a projecting lens 7. The S polarized light reflected by the PBS toward the direction +Y goes toward a direction +Z through the mirror 4, then, the light is made incident on the light valve for a luminance signal 6, thereafter, the light is made incident on a projecting lens 8. That is, by such a constitution, the length of the optical path between the light source 1 and the light valve 5 is made equal to the length of the optical path between the light source 1 and the light valve 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type display device using a transmissive liquid crystal light valve, and more particularly to a projection type display device using two light valves.

[0002]

2. Description of the Related Art Conventionally, light from a light source is separated into S-polarized light and P-polarized light by a polarization beam splitter (PBS), and each polarized light is incident on a color signal liquid crystal light valve and a brightness signal liquid crystal light valve. It is known that there are two types of methods for synthesizing the modulated light that has passed through the light valves, and there are two methods for synthesizing the modulated light that has passed through the light valves. ing. 1
The other is a method in which each polarized light that is polarized and separated is modulated by a liquid crystal light valve for each color, and the modulated lights are combined and then projected onto a screen by one projection lens. The other one is a method in which polarized lights separated by polarization are modulated by liquid crystal light valves for respective colors, and the respective modulated lights are combined on a screen by respective projection lenses.

Next, as an example of the prior art, the configuration of the projection type display device described in the latter will be described. FIG. 2 is an example thereof. Light from the light source 100, which is composed of randomly polarized light, is incident on the PBS 101, and is separated into S-polarized light that is reflected by the polarization separation unit of the PBS and P-polarized light that is transmitted. The traveling direction of the P-polarized light that has passed through the PBS 101 is changed by the bending mirror 102 to a substantially right angle direction,
The light enters the color signal liquid crystal light valve 104. On the other hand, PB
The S-polarized light reflected at S101 enters the brightness signal liquid crystal light valve 103. The light modulated by the luminance signal and the light modulated by the color signal and transmitted through each light valve are projected onto a screen (not shown) by the projection lenses 105 and 106, respectively, and are modulated by the projected image modulated by the color signal and the luminance signal. The projected image is combined with the projected image on the screen.

[0004]

However, the conventional projection type display device described above has the following problems. First, since the arrangement positions of the color signal liquid crystal light valve 104 and the luminance signal light valve 103 with respect to the light source are different, the uneven illumination varies depending on the respective light valves. In the case where the liquid crystal light valves are arranged as shown in FIG. 2, if the light polarized and separated by the PBS illuminates the entire surface of the color signal light valve, the range of the brightness signal light valve surface illuminated. It will illuminate the outside of the light valve, resulting in PBS
Even if the powers of the P-polarized light that is transmitted and the S-polarized light that are reflected are separated, the illumination of the brightness signal light valve becomes dark.

In order to solve the above problems, the present invention provides
It is an object of the present invention to provide a high-intensity and compact projection-type display device having an optical element arrangement that illuminates each liquid crystal light valve in a well-balanced manner and has no image unevenness.

[0006]

According to claim 1 of the present invention,
Light from a randomly polarized light source is made incident on a polarization beam splitter, and one of the polarized lights emitted after being polarized and separated by the polarization beam splitter is made incident on a color signal light valve and the other is made on a luminance signal light valve. In the projection type display device in which the projection light emitted from each light valve is projected by the projection lens arranged for each light valve and the projected images are superimposed on the screen, each polarized light emitted from the polarization beam splitter Is reflected by a bending mirror, the traveling directions of the reflected lights are substantially parallel to each other, and the optical path lengths from the light source to the light valve are made equal to each other.

According to a second aspect of the present invention, the light source light of random polarization is made incident on the polarization beam splitter, and one of the polarized lights emitted after being polarized and separated by the polarization beam splitter is set to the color signal light valve and the other is set to the other. In the projection type display device, which is made incident on the light valve for luminance signal, projected light emitted from each light valve is projected by the projection lens arranged for each light valve, and the projected images are superimposed on the screen, Each polarized light emitted from the polarization beam splitter is reflected by a bending mirror, the traveling directions of the reflected lights are substantially parallel to each other, and the vibration direction of the polarized light incident on the color signal and brightness signal light valves is The light valve has the same direction.

Further, according to a third aspect of the present invention, the light source light consisting of randomly polarized light is made incident on the polarization beam splitter, one of the polarized lights which is polarized and separated by the polarization beam splitter is emitted to the color signal light valve, and the other is emitted. In the projection type display device, which is made incident on the light valve for luminance signal, projected light emitted from each light valve is projected by the projection lens arranged for each light valve, and the projected images are superimposed on the screen, Each of the polarized lights emitted from the polarization beam splitter is reflected by a bending mirror, the traveling directions of the reflected lights are substantially parallel to each other, and the optical path lengths from the light source to the light valve are equal to each other. Also, the vibration direction of the polarized light incident on the light valve for brightness signal is the same as that of the light valve.

[0009]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIG. The randomly polarized light source light emitted from the light source 1 in the + X direction enters a polarization beam splitter (hereinafter referred to as PBS) 2 arranged on the X axis optical axis. As the light source light 1 is focused as a virtual point far ahead of the PBS2, the light source 1 is gently focused to the PBS2.
Incident on. The incident light source light is split by the polarization splitting unit (hatched portion in FIG. 1), passes through the PBS 2 and is emitted in the + X direction (P-polarized light (oscillating in ± Y direction)) and the PBS.
At 2, the light is reflected in the + Y direction and becomes S-polarized light (vibrating in ± Z directions), and the S-polarized light and the P-polarized light are emitted from the PBS 2 in directions substantially at right angles to each other. + X by PBS2
The P-polarized light emitted in the direction is + Z by the bending mirror 3.
And proceeds to the color signal light valve 5 arranged on the Z axis. The light that has entered the light valve 5 is modulated by the color signal of the color signal light valve and enters the projection lens 7.

On the other hand, the S-polarized light reflected by the PBS 2 in the + Y direction travels in the + Z direction by the bending mirror 4,
The light enters the light valve 6 for the brightness signal arranged on the Z axis. The incident light is modulated by the brightness signal of the brightness signal light valve and enters the projection lens 8. The respective projected images are combined on the screen through the respective projection lenses 7 and 8 for the color signal and the luminance signal.

The light paths from the light source 1 to the color signal light valve and the brightness signal light valve have equal optical path lengths, and the light emitted from the color signal light valve and the light emitted from the brightness signal light valve are equal. Are arranged so that their optical axes are parallel to each other. Next, the polarization direction (vibration direction) of the polarized light entering the light valve will be described. The P and S polarized lights polarized and separated by the PBS 2 are reflected by the folding mirrors 3 and 4 in the same direction (+ Z direction). Further, the polarization directions (vibration directions) of the respective polarized lights incident on the light valves for the color signal and the brightness signal are ± Y directions with respect to the light valves 5 and 6 for the color signal and the brightness signal, respectively. It can be seen that the vibration directions are the same. With such a configuration and arrangement, the image directions on the respective light valves are also in the same direction, and the respective images are combined on the screen in the same direction. As the projected image, an image without image unevenness can be obtained.

Next, for comparison, the arrangement of the conventional example shown in FIG. 2 will be described. Randomly polarized light from the light source 100 is polarized and separated by the PBS 101, and the polarized P is separated.
Polarized light (vibration direction is ± Z direction) is transmitted through PBS101,
The light is reflected by the folding mirror 102 in the + Z direction and enters the color signal light valve 104. The vibration direction of the polarized light at that time is ± X direction. On the other hand, the S-polarized light that is polarized and separated by the PBS 101 and reflected travels in the + Z direction,
The light enters the brightness signal light valve 103. The vibration direction of the polarized light incident at that time is ± Y direction (direction perpendicular to the paper surface)
It is. In this way, the vibration directions of the polarized light incident on the color signal light valve 104 and the luminance signal light valve 103 are orthogonal to each other. Therefore, the light is modulated by each light valve, and the projection lenses 105, 10
Image unevenness is remarkably generated in the projected image synthesized on the screen via 6.

Further, in order to solve this problem, the polarization directions of the lights incident on the light valve are made the same. One of them is the light valve 1 for color signals.
There is a method of arranging a half-wave plate immediately before on either of No. 04 or the brightness signal light valve 103 and converting the polarization direction by 90 degrees to make them the same. Further, as another example in which the half-wave plate is not used, the directions of the liquid crystal panel forming the light valve and the polarizing plates forming the crossed Nicols arranged so as to sandwich the liquid crystal panel are orthogonal to each other, and It is necessary to use a method such that the orientation directions are opposite to each other.

However, in the present invention, the half-wave plate is not necessary, it is not necessary to modify other optical elements such as a liquid crystal light valve, and it can be easily realized only by arranging the optical elements. Next, the resolution of each light valve for the color signal and the brightness signal will be described. The light valve 6 for the brightness signal uses a high resolution black and white liquid crystal panel. This is because the resolution of the projected image depends on the resolution of this panel. The liquid crystal panel used for the color signal light valve 5 has pixels of R, G, and B panels formed in a matrix, and the size of the pixel of the color signal light valve is the same as that of the luminance light valve. Then 1 for the color signal
Pixels correspond to one pixel for luminance, three pixels for color signals correspond to one pixel for luminance signals, and the actual pixel density becomes 1/3 for luminance signals for luminance signals. Configuration of the projection type display device shown in the embodiment of the present invention, that is,
One of the polarized and separated light is modulated by the luminance signal of the high-definition luminance signal light valve, and the other of the polarized and separated light is emitted from the color signal light valve whose pixel density is lower than that of the luminance signal light valve. With the configuration in which the modulated light is projected as a composite image on the screen, it is possible to increase the brightness of the projected image and enable color projection without image unevenness.

A black and white image on the light valve 5 for the brightness signal, which is modulated by the brightness signal, is projected on the screen by the projection lens 7. On the other hand, the color projection image on the color signal light valve 6 modulated by the color signal is projected on the screen by the projection lens 8 and becomes a projection image combined with the monochrome image by the luminance signal. In the present invention, each of the brightness signal light valve 5 and the color signal light valve 6 is arranged at an equal distance from the light source 1. Therefore, PB
The P and S polarized lights separated by S can illuminate the liquid crystal light valve with substantially the same intensity. Further, since the light valves for the color signal and the light valves for the luminance signal have the same size, it is possible to obtain a projected image having the same brightness and no image unevenness. Further, since the means for converting the polarization direction is not necessary and the size of the PBS can be reduced, the projection type display device can be downsized.

Further, the brightness signal light valve 5 and the color signal light valve 6 are arranged such that their planes are parallel to each other, and the vibration direction of the polarized light incident on each light valve is the same as that of the light valve. By arranging them spatially so that they are oriented in the same direction, it is possible to obtain a good projection image with higher brightness and no image unevenness. In the present embodiment, the light from the light source is described as emitting light that converges in the distance. However, for example, in FIG. 1, a shaping optical system such as a lens is used between the light source 1 and the PBS 2 to shape the light into parallel light. May be.

The case of using a rod integrator that forms a surface light source having a uniform light intensity for the light emitted from the light source may be considered as follows. The light from the light source is incident on one end surface of the rod integrator, is condensed, is emitted from the other end surface, and is incident on the PBS. Therefore, the light source can be regarded as the emitting end face of the rod integrator. Even in such a configuration, by arranging so that the optical path lengths from the light source to the liquid crystal light valve are equal, the same operation as that of the embodiment of the present invention can be obtained.

[0018]

According to the present invention, the light valve for the luminance signal and the light valve for the color signal are arranged at the same distance from the light source so that each light valve can be illuminated with the same brightness. A bright full-color projection image without image unevenness can be obtained as the projection image in which the signal light valves are superimposed.

Further, by making the polarization directions of the polarized illumination light incident on the light valves for each color signal and for the luminance signal the same, it is not necessary to dispose a ½ wavelength plate on one light valve, and the structure is changed. It can be simplified and the polarization beam splitter can be miniaturized.

[Brief description of drawings]

FIG. 1 is a configuration perspective view illustrating an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a conventional projection display device.

[Explanation of symbols]

 1 Light source 2 Polarization beam splitter 3, 4 Reflecting mirror 5 Light valve for color signal 6 Light valve for luminance signal 7, 8 Projection lens

Claims (3)

[Claims] 1. A light valve for a color signal and one light beam for a luminance signal, wherein one of the polarized light beams, which is made by entering randomly polarized light source light into a polarization beam splitter and is polarized and separated by the polarization beam splitter, is emitted. Incident on
In a projection type display device in which the projection light emitted from each light valve is projected by a projection lens arranged for each light valve and the projected images are superimposed on the screen, each polarized light emitted from the polarization beam splitter Is reflected by a bending mirror, the traveling directions of the reflected lights are substantially parallel to each other, and the optical path lengths from the light source to the light valve are made equal to each other. 2. A light valve for color signals and one light beam for luminance signals, one of which is polarized light emitted from a polarization beam splitter, the light source light having random polarization being incident on the polarization beam splitter, and being polarized and separated by the polarization beam splitter. Incident on
In a projection type display device in which the projection light emitted from each light valve is projected by a projection lens arranged for each light valve and the projected images are superimposed on the screen, each polarized light emitted from the polarization beam splitter Are reflected by a bending mirror, the traveling directions of the reflected lights are substantially parallel to each other, and the vibration directions of the polarized light incident on the color signal and brightness signal light valves are the same as the light valves. A projection display device characterized by the above. 3. A light valve for color signals, one of which is polarized light emitted from a polarized beam splitter, which is made by entering light of random polarized light into a polarized beam splitter, and which is emitted after being polarized and separated by the polarized beam splitter. Incident on
In a projection type display device in which the projection light emitted from each light valve is projected by a projection lens arranged for each light valve and the projected images are superimposed on the screen, each polarized light emitted from the polarization beam splitter Is reflected by a bending mirror, the traveling directions of the reflected lights are substantially parallel to each other, and the optical path lengths from the light source to the light valve are made equal to each other, and the light beams are made incident on the color signal and brightness signal light valves. A projection display device characterized in that the polarized light vibrates in the same direction as the light valve.