JP2818537B2 - Liquid crystal projector using polarized light source device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector using a polarized light source device, and more particularly to a liquid crystal projector capable of increasing the brightness of a projection screen and achieving a uniform brightness distribution of the projection screen.

[0002]

2. Description of the Related Art A conventional liquid crystal projector will be described below with reference to the drawings. FIG. 7 shows a conventional general liquid crystal projector. This liquid crystal projector uses a high brightness white light source 1 such as a metal halide lamp.
11 and a parabolic reflecting mirror 112 which reflects a part of the light beam emitted from the light source 111 and generates a parallel light beam
A heat ray filter 119 for absorbing or reflecting the heat ray of the light beam incident through the reflecting mirror 112; a polarizing plate 116a for converting the parallel light beam from which the heat ray has been removed into a linearly polarized light component; A liquid crystal light valve 117 that modulates light in accordance with an image signal, a polarizing plate 116b that transmits only the component in the transmission axis direction of the modulated linearly polarized component light, and a linearly polarized component light that is transmitted are shown. Projection lens 11 that enlarges and projects on a screen that does not
8 was provided.

However, in the liquid crystal projector having such a configuration, of the light flux emitted from the light source 111, only the linearly polarized light component transmitted through the polarizing plate 116a is used as illumination light for the liquid crystal light valve 117, and this linearly polarized light component is used. Other linearly polarized light components orthogonal to the light are lost, resulting in poor light use efficiency and a dark projection screen. Further, when the amount of light emitted from the light source 111 is increased in order to make the projection screen brighter, there is a problem that the performance of the polarizing plate 116a is significantly deteriorated and the characteristics of the liquid crystal light valve 117 are significantly deteriorated. Further, there is a problem that the linearly polarized component light not used as illumination light is converted into heat in the polarizing plate 116a, which causes the polarizing plate 116a to change its quality due to a rise in temperature and to deteriorate the projected image.

In order to solve such problems, Japanese Patent Application Laid-Open Nos. Hei 3-122263 and Hei 3-126910 propose a liquid crystal projector having a polarized light source device as shown in FIGS. . In these drawings,
The polarization light source device 200 includes a polarization beam splitter 201.
And reflection means 202. The polarization beam splitter 201 has a configuration in which a plurality of prisms having a triangular prism shape are combined, and emits one of the P-polarized component light and the S-polarized component light, which are linearly polarized light components, out of the light beam emitted from the light source 111. The light is reflected and transmitted through the other, and separates both polarized light components. Further, the reflection means 202 is, for example, 1 /
The liquid crystal light valve 1 is a combination of a two- or quarter-wave plate and a plane mirror, in which the polarization directions of the two polarization component lights separated by the polarization beam splitter 201 are the same.
It is incident on 17. Japanese Patent Laid-Open No. 3-1 having such a configuration
According to the liquid crystal projector disclosed in Japanese Patent No. 22631 and Japanese Patent Application Laid-Open No. 3-126910, the efficiency of use of the luminous flux emitted from the light source 111 is improved, and the liquid crystal light valve 117 can be effectively illuminated.

In Japanese Utility Model Application Laid-Open No. 2-121779, as shown in FIG. 12, one of the S-polarized component light and the P-polarized component light separated by the polarization beam splitter 201 is separated by a half-wave plate 206. A liquid crystal projector has been proposed in which polarization conversion is performed so that these two polarized component light beams have the same polarization direction, and then enter the liquid crystal light valve 117.

[0006]

SUMMARY OF THE INVENTION However, the above-mentioned Japanese Patent Application Laid-Open Nos. 3-122263 and 3-12691.
In the liquid crystal projector of No. 0, although the light use efficiency can be improved, there is a problem that the uniformity of the projection screen luminance distribution is lacking. That is, the light beam emitted from the light source 111 becomes the illumination light 301 of the liquid crystal light valve via the polarized light source device 200 and the like, and illuminates the effective display area 117a of the liquid crystal light valve 117 in a state as shown in FIG.
Here, generally, the intensity distribution of the luminous flux emitted from the light source is the strongest at the central portion, and this illumination light 301 also has a vertical cross section, a horizontal cross section, and an effective display area 117a of the liquid crystal light valve 117.
In the diagonal sections, as shown in FIGS. 10B to 10D, the illuminance distribution was strong at the central portion and weakened as approaching the peripheral portion. Therefore, Japanese Patent Application Laid-Open No.
The projection screen luminance distributions of the liquid crystal projectors described in Japanese Patent No.
The illuminance distribution of No. 1 was reflected, and as shown in FIG. 11, the central part was strong and the peripheral part was weak, and was uneven.

In the liquid crystal projector disclosed in Japanese Utility Model Application Laid-Open No. 2-121779, the transmitted light 302 and the reflected light 303 of the polarizing beam splitter 201 move the effective display area 117a of the liquid crystal light valve 117 in a state as shown in FIG. I was lighting. For this reason, as shown in FIGS. 13B and 13C, portions (central portions) where the light intensity of the transmitted light 302 and the reflected light 303 are strong are located on both sides of the central portion of the effective display area 117a of the liquid crystal light valve 117. As shown in FIG. 14, two peaks appear in the projection screen luminance distribution of the liquid crystal projector, and there is a problem that the projection screen luminance distribution lacks uniformity. Further, there is a problem that the output of the light source 111 must be increased in order to increase the luminance at the center of the projection screen in order to make the projection screen luminance distribution uniform.

The present invention has been made in view of the above problems, and has as its object to provide a liquid crystal projector capable of increasing the brightness of a projection screen and achieving a uniform luminance distribution of the projection screen. .

[0009]

In order to achieve the above object, a liquid crystal projector according to the present invention comprises a liquid crystal projector having a central axis coinciding with an optical axis of a light source and a vertex directed toward the light source. It has a polygonal pyramid-shaped polarization splitting surface, and among the light emitted from the light source, reflects one of the P-polarized component light and the S-polarized component light by this polarization splitting surface and transmits the other to effectively operate the liquid crystal light valve. a polarization beam splitter for emitting the entire display area, polarization of the polarization beam splitter
Receives the reflected light beam reflected from the light separation surface and changes the optical path.
Projected on the periphery of the effective display area of the liquid crystal light valve
And the polarization transmitted through the polarization beam splitter.
Optical means having the function of converting the light component into the same polarization component as light
And a polarized light source device comprising:
A step is installed at a predetermined angle, and the polarizing beam splitter is
Change the optical path of the reflected light beam reflected from the polarization separation surface
Light beam reflecting element, and reflected from the polarizing beam splitter.
The phase of the polarized light component is
Phase to make the same polarization component as the polarization component transmitted through the splitter
And a configuration including a difference plate , preferably , a configuration in which the polarization splitting surface of the polarization beam splitter forming the polarized light source device is a regular quadrangular pyramid, or the polarization splitting surface of the polarization beam splitter forming the polarized light source device is The configuration is a regular octagonal pyramid shape.

[0010]

According to the liquid crystal projector of the present invention having the above configuration, the polarization splitting surface of the polarization beam splitter reflects one of the P-polarized component light and the S-polarized component light in the light beam emitted from the light source, The other polarized component light is transmitted through the other. Among these, the polarized component light transmitted through the polarized beam splitter illuminates the entire effective display area of the liquid crystal light valve. Also, the polarization component light reflected on the polarization splitting surface of the polarization beam splitter is changed in optical path by a light beam reflection element, and then phase-converted by a phase difference plate to become the same component light as the polarization component light transmitted through the polarization beam splitter. Illuminate the periphery of the effective display area of the liquid crystal light valve.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the liquid crystal projector of the present invention will be described below with reference to the drawings. First, a liquid crystal projector according to a first embodiment of the present invention will be described. FIG. 1 is a block diagram illustrating a liquid crystal projector according to the present embodiment. FIG. 2 is a perspective view showing a polarized light source device of the present liquid crystal projector. FIG. 3 is an exploded perspective view showing the polarized light source device. In the liquid crystal projector according to the present embodiment, the polarization beam splitter of the polarization beam splitter has a configuration of a regular quadrangular pyramid.

In these drawings, reference numeral 10 denotes a light source unit, which comprises a light source 11 and a reflecting mirror 12. Light source 1
Reference numeral 1 denotes a high-luminance light source such as a metal halide lamp, a xenon lamp, and a halogen lamp.
The light beam radiated from 1 is reflected by the parabolic reflecting mirror 12 and emitted as a parallel light beam of indeterminate polarization. 20
Denotes a polarized light source device, which comprises a polarized beam splitter 21, a light beam reflecting element 22 and a retardation plate 23. The polarization beam splitter 21 includes a regular quadrangular pyramid prism 21a whose center axis coincides with the optical axis of the light source 11, and whose apexes of the four inclined surfaces face the light source 11 to form a polarization separation surface. And four pentahedral prisms 21b to 21e which are combined with the regular quadrangular pyramid prism 21a to make the whole rectangular parallelepiped. The four inclined surfaces forming the polarization splitting surface of the regular quadrangular pyramid prism 21a are formed so as to be inclined by 45 ° with respect to the optical axis of the light source 11 and to be targeted. Such a polarization beam splitter 21 transmits the P-polarized component light and reflects the S-polarized component light of the light flux emitted from the light source by the polarization splitting surface.

The light beam reflecting elements 22 are reflecting mirrors for changing the optical path of the S-polarized component light reflected by the polarizing beam splitter 21, and are attached to the four sides of the polarizing beam splitter 21 on the light source 11 side, respectively. 21 with respect to the exit surface 21f of the light-receiving surface 21 at a predetermined angle α ° smaller than 45 ° (that is, 9 ° with respect to the normal direction of the polarization separation surface).
(Inclination of 0 ° or less).

The phase difference plate 23 is arranged in the optical path of the S-polarized component light whose optical path has been changed by the light beam reflecting element 22. The phase difference plate 23 is a half-wave plate that performs a phase conversion of 90 ° on a plane perpendicular to the traveling direction of the transmitted light, and converts the transmitted S-polarized component light into the P-polarized component light. Incidentally, such a phase difference plate 23 may be arranged so as to coincide with the emission surface 21f of the S-polarized component light of the polarization beam splitter 21. Reference numeral 30 denotes an image forming unit, and the polarizing plate 3
1a, 31b, liquid crystal light valve 32 and projection lens 3
3, when the light beam emitted from the polarized light source device 20 is incident, the light is detected by the front and rear polarizing plates 31a and 31b, and the image formed on the liquid crystal light valve 32 is screened by the projection lens 33 (not shown). On the screen. Further, in the present embodiment, the luminous flux emitted from the luminous flux reflecting element 22 is made to enter the four corners of the effective display area 32a of the liquid crystal light valve 32.
Is arranged at an angle.

Next, the operation of the liquid crystal projector according to the present embodiment having the above configuration will be described. In the light source unit 10, the light beam emitted by the light source 11 is reflected by the parabolic reflector 12, becomes a parallel non-uniform polarized light beam, and is emitted to the polarized light source device 20. The polarized light source device 20 allows the polarized beam splitter 21 to transmit the P-polarized component light and reflect the S-polarized component light in the light beam emitted from the light source unit 10. The P-polarized component light that has passed through the polarization beam splitter 21 proceeds straight as it is and is emitted to the liquid crystal light valve 32. The S-polarized component light reflected by the polarization beam splitter 21 is changed in optical path by a light beam reflecting element 22 and is phase-converted to a P-polarized component light by a phase difference plate 23. The light is reflected in the original direction and emitted to the liquid crystal light valve 32. As a result, on the liquid crystal light valve 32, the P-polarized component light transmitted through the polarization beam splitter 21 and the P-polarized component light whose optical path has been changed and the phase has been converted by the light beam reflecting element 22 and the phase difference plate 23 are superimposed.

FIG. 4A shows the liquid crystal light valve 3.
FIG. 4B is an explanatory diagram showing a superimposed state of a projection light beam (light beam emitted from the polarized light source device 20) for illuminating No. 2 and FIG.
Is a graph showing the illuminance distribution of the projection light beam. In these drawings, P transmitted through the polarizing beam splitter 21 is shown.
The polarization component light (transmitted light 41) and the P-polarization component light (reflected light 42) whose optical path has been changed and phase-converted by the light flux reflection element 22 and the phase difference plate 23 have a strong central portion, and the farther away from the central portion, the stronger. 4 shows a light intensity distribution that becomes weaker. Then, of the luminous flux emitted from the polarized light source device 20, the P-polarized component light transmitted through the polarization beam splitter 21 mainly illuminates the entire effective display area 32a of the liquid crystal light valve 32. The P-polarized component light whose optical path has been changed and phase-converted by the phase difference plate 23 mainly illuminates the four corners of the effective display area 32 a of the liquid crystal light valve 32. As a result, the light intensity is high as shown in FIG. 4B, and almost uniform illuminance distribution characteristics can be obtained.

Next, a liquid crystal projector according to a second embodiment of the present invention will be described with reference to FIGS.
FIG. 5 is a perspective view showing a polarized light source device of the liquid crystal projector according to the present embodiment. FIG. 6 is an exploded perspective view showing the polarized light source device. In the liquid crystal projector of this embodiment, the polarization splitting surface of the polarization beam splitter 51 has a regular octagonal pyramid shape, and the retardation plate is a half-wave plate 53a.
And the quarter-wave plate 53b are alternately arranged.

According to the liquid crystal projector of this embodiment having such a configuration, the luminous flux emitted from the light source 11 is separated into P-polarized component light and S-polarized component light by the polarization splitting surface of the polarization beam splitter 51. . The P-polarized component light transmitted through the polarization beam splitter 51 goes straight as it is and illuminates the entire effective display area 32 a of the liquid crystal light valve 32. On the other hand, the S-polarized component light reflected on the polarization splitting surface of the polarization beam splitter 51 is changed in optical path by the light beam reflecting element 52 and is phase-converted to P-polarized component light by the light beam reflecting elements 53a and 53b. Illuminate the upper, lower, left, right, and four corners of the effective display area 32a. That is, according to the liquid crystal projector of the present embodiment, it is possible to superimpose the illumination light in the directions of the center, up, down, left, right, and four corners of the effective display area 32a, thereby obtaining a projection luminance distribution with extremely high uniformity.

According to the present liquid crystal projector according to the first and second embodiments, the polarization beam splitter 21,
The linearly polarized light component separated by the polarization separation surface 51 is effectively polymerized on the effective display area 32 a of the liquid crystal light valve 32. As a result, the brightness of the projection screen can be increased, and the distribution of the brightness of the projection screen can be made uniform. Further, by adjusting the installation angle of the light beam reflecting elements 22 and 52, the luminance ratio of the center to the periphery on the projection screen can be arbitrarily controlled.

Further, since the linearly polarized light component, which has not been conventionally used, can be used as the illumination light for the liquid crystal light valve 32, the conversion efficiency to the linearly polarized light component light is about twice that of the conventional one, and the light use efficiency of the light source is improved. And the polarizing plate 31
It is possible to suppress image deterioration due to temperature rises of a and 31b and characteristic changes due to heat of the liquid crystal light valve 32, and obtain a high quality projected image. Furthermore, the polarized light source device 20,
Since the light beam emitted from the light source 50 is converted into linearly polarized light component light having a uniform polarization direction, light is hardly absorbed by the polarizing plates 31a and 31b, and the light use efficiency can be further improved.

The liquid crystal projector of the present invention is not limited to the above embodiment. For example, the polarization splitting surface of the polarization beam splitter is preferably a regular quadrangular pyramid or a regular octagonal pyramid from the viewpoint of forming a retardation plate, but may be changed to another regular pyramid. Although the liquid crystal projector of the above embodiment has a monochrome display configuration, a color separation optical element such as a dichroic mirror or a dichroic prism is provided between the polarized light source device 20 (50) and the polarizing plate 31a. Is divided into three primary colors, and each light beam is modulated by a liquid crystal light valve, and then color-combined by a color-combining optical element, and then enlarged and projected by one projection lens, or the color-combining optical element is If a configuration in which images are superimposed on a projection screen using three projection lenses is omitted, full-color display is possible.

[0022]

As described above, according to the liquid crystal projector of the present invention, the brightness of the projection screen can be increased and the distribution of the brightness of the projection screen can be made uniform.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a liquid crystal projector according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a polarized light source device of the liquid crystal projector.

FIG. 3 is an exploded perspective view showing a polarized light source device of the liquid crystal projector.

4A and 4B show characteristics of a projection light beam of the polarized light source device. FIG. 4A is an explanatory diagram showing a state of superposition of the projection light beam, and FIG. 4B is a graph showing an illuminance distribution of the projection light beam. is there.

FIG. 5 is a perspective view showing a polarized light source device of a liquid crystal projector according to a second embodiment of the present invention.

FIG. 6 is an exploded perspective view showing the polarized light source device.

FIG. 7 is a block diagram showing a liquid crystal projector according to one conventional example.

FIG. 8 is a block diagram showing a liquid crystal projector according to another conventional example.

FIG. 9 is a block diagram showing a liquid crystal projector according to still another conventional example.

10A and 10B show characteristics of a projection light beam of a liquid crystal projector according to another example of the related art, and FIG. 10A is an explanatory diagram showing a state of superposition of the projection light beam, and FIGS. (C) and (d) are graphs each showing the illuminance distribution of the projected light beam.

FIG. 11 is a graph showing a horizontal cross-sectional luminance distribution of a projection screen of a liquid crystal projector according to another example of the related art.

FIG. 12 is a block diagram showing a liquid crystal projector according to still another conventional example.

13A and 13B show characteristics of a projection light beam of a liquid crystal projector according to the above and still another conventional example, and FIG.
Is an explanatory view showing the state of superimposition of the projected light beam, FIG.
(C) is a graph showing the illuminance distribution of the projection light beam.

FIG. 14 is a graph showing a horizontal cross-sectional luminance distribution of a projection screen of a liquid crystal projector according to yet another conventional example.

DESCRIPTION OF THE SYMBOLS 10 Light source unit 11 Light source 12 Reflecting mirror 20 Polarized light source device 21 Polarized beam splitter 21a Regular quadrangular pyramid prism 21b-e pentahedral prism 21f Outgoing surface 22 Light beam reflecting element 23 Phase difference plate 30 Image forming units 31a, 31b Polarized light Plate 32 Liquid crystal light valve 32a Effective display area of liquid crystal light valve 41 Transmitted light 42 Reflected light 50 Polarized light source device 51 Polarized beam splitter 52 Reflected light beam element 53a Phase difference plate (1/2 wavelength plate) 53b Phase difference plate (1/4) Wave plate)

Claims (3)

(57) [Claims] 1. A central axis coincides with an optical axis of a light source, and
A vertex has a regular polygonal pyramid-shaped polarization splitting surface facing the light source side, and among the light emitted from the light source, one of the P-polarized component light and the S-polarized component light is separated by the polarization splitting surface. A polarizing beam splitter that reflects light, transmits the other light, and emits light to the entire effective display area of the liquid crystal light valve, and reflects light from the polarization splitting surface of the polarizing beam splitter.
Receives the reflected light flux, changes the optical path, and
At the periphery of the effective display area of the
The same polarization as the polarization component light transmitted through the polarization beam splitter
Optical means having the function of converting
A polarization light source device, wherein the optical means is installed at a predetermined angle, and the polarization beam splitter is polarized.
Light that changes the optical path of the reflected light beam reflected from the light separation surface
Bundle reflection element, reflected from the polarizing beam splitter
The polarization beam splitter converts the phase of the
Retarder to make the same polarization component as the transmitted polarization component
A liquid crystal projector comprising: 2. A polarization beam splitter forming the polarization light source device, wherein a polarization splitting surface has a regular quadrangular pyramid shape.
The liquid crystal projector as described. 3. A polarization beam splitter forming the polarization light source device, wherein a polarization splitting surface has a regular octagonal pyramid shape.
The liquid crystal projector as described.