JPH1054984A - Irradiation device for liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form linearly polarized light with high efficiency by assembling a quarter wavelength plate and a polarizing beam splitter instead of a polarizing plate used for forming the linearly polarized light. SOLUTION: The part of a light beam which is not directly reflected by a parabolic reflection mirror 2 is reflected by an aperture spherical reflection mirror 3 having a circular aperture of a rectangular aperture on the central part. Since a white light source 1 is roughly arranged on the focusing position of the mirror 3, the reflected light beam is transmitted through the focusing position of the mirror 3, reflected by the mirror 2, and converted into the parallel light. Thus, since the light beam converted into the parallel light is a natural light beam, the polarization direction is in disorder. The light beam converted into the parallel light is made incident on the quarter wavelength plate 4, modulated in terms of a polarization plane, and made incident on the polarizing beam splitter 5. As to the light beam whose polarization plane is modulated; a P polarized light component passes through the splitter 5, but an S polarized light component is reflected by reflection surfaces 6 and 7, goes toward the plate 4 again, and passes through the plate 4 so as to be converted into the circularly polarized light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an irradiation device for a liquid crystal projector.

[0002]

2. Description of the Related Art In a conventional irradiation apparatus for a liquid crystal projector, the light collection efficiency and polarization efficiency are extremely poor, and the final light utilization efficiency is about 2%. The causes include insufficient light-collecting characteristics due to the size of the light source, and furthermore, since the liquid crystal light valve uses a polarizing plate and an analyzer, there are polarization conversion loss and absorption. In addition, the polarization characteristics may be insufficient due to the wavelength dependence of the optical element in the polarization conversion optical system.

[0003]

In the conventional irradiation apparatus for a liquid crystal projector, the efficiency of using light from a light source is as low as about 2%. The light source generally used is a metal halide lamp. However, since it is not a point light source, it is impossible to obtain perfect parallel light, but it is necessary to improve the light-collecting characteristics. Further, when irradiating the liquid crystal light valve, it is necessary that the light is linearly polarized light. However, since the light source is in a non-polarized state close to natural light, it must be efficiently converted to linearly polarized light.

[0004]

According to a first aspect of the present invention, a white light source is arranged at a substantially focal position of a first reflecting mirror having a curved surface, and further has a curved surface and an opening at a central portion. The first and second reflectors are arranged so as to face each other such that the focal position of the second reflector substantially coincides with the position of the white light source.
A quarter-wave plate is disposed so as to be located between the quarter-wave plates, and the polarizing beam splitter is further positioned such that the quarter-wave plate is located between the second reflecting mirror and the polarizing beam splitter. It is suggested to arrange.

Further, the second invention proposes that the first reflecting mirror is a parabolic reflecting mirror and the second reflecting mirror is a spherical reflecting mirror.

Further, the third invention proposes that the first reflecting mirror is a spherical reflecting mirror, a collimator lens is used instead of the second reflecting mirror, and the focal point of the collimator lens coincides with the position of the white light source. .

According to a fourth aspect of the present invention, the first reflecting mirror is an ellipsoidal reflecting mirror, and the white light source is disposed at a position substantially coincident with a focal position existing on the first reflecting mirror side. It is proposed to make the other focal position of the collimator lens substantially coincide with the focal position of the collimator lens.

A fifth invention proposes that the polarizing beam splitter has two reflecting surfaces, and the two reflecting surfaces are orthogonal to each other.

The sixth invention proposes that the high-speed axis or the low-speed axis of the quarter-wave plate is at 45 degrees with respect to the reflecting surface of the polarizing beam splitter and the incident surface formed by the incident light.

According to a seventh aspect of the present invention, a white light source is disposed substantially at a focal position of a first reflecting mirror having a curved surface, and the focal position of a second reflecting mirror having a curved surface and having an opening at a central portion is set to the light source. The first and second reflectors face each other so as to substantially coincide with each other, the white light source is separated into red, green, and blue light by two dichroic mirrors, and the quarter-wave plate and the polarization beam are separated. It is proposed that an optical element composed of a splitter is arranged independently for each color light beam, and that the red, green and blue colors are combined by a third dichroic mirror.

[0011]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of an optical system showing an embodiment of the present invention. A part of the light emitted from the white light source 1 which is a metal halide lamp, a halogen lamp or a xenon lamp is reflected by the parabolic reflector 2. At this time, since the white light source 1 is disposed substantially at the focal position of the parabolic reflector 2, the reflected light beam is converted into substantially parallel light. Some light rays that are not directly reflected by the parabolic reflector 2 are reflected by an aperture spherical reflector 3 having a circular or rectangular aperture at the center. On this occasion,
Since the white light source 1 is disposed substantially at the focal position of the open spherical reflecting mirror 3, the reflected light beam passes through the focal position of the open spherical reflecting mirror 3, is reflected by the parabolic reflecting mirror 2, and becomes parallel light. Is converted. The light beam converted into parallel light as described above is a natural light, so that the polarization direction is random. The light beam converted into parallel light is incident on the quarter-wave plate 4, is subjected to polarization plane modulation, and is incident on the polarization beam splitter 5. The P-polarized light component of the polarization-modulated light beam passes through the polarizing beam splitter 5, while the S-polarized light component is reflected by the reflection surfaces 6 and 7 and travels again toward the quarter-wave plate 4. ,
The light is converted into circularly polarized light by passing through the quarter-wave plate 4. This is because the high-speed axis or the low-speed axis of the quarter-wave plate 4 is at an angle of 45 degrees with respect to the plane of incidence between the reflecting surfaces 6 and 7 of the polarizing beam splitter 5 and the incident light beam. The light beam converted into the circularly polarized light is reflected by the parabolic reflector 2 and passes through the white light source 1, and a part of the light is reflected again by the parabolic reflector 2 and converted into a parallel light.
The light is converted from circularly polarized light to P-polarized light by the wavelength plate 4 and passes through the polarization beam splitter 5. The white light source 1 which is reflected by the parabolic reflector 2 among the light beams converted into circularly polarized light
, And reflected by the open spherical reflecting mirror 3. This light beam passes through the white light source 1 again, is further reflected by the parabolic reflector 2, and is converted into parallel light. The circularly-polarized light converted into parallel light is converted from circularly-polarized light to P-polarized light by a quarter-wave plate, and passes through the polarization beam splitter 5. With the optical system configured as described above, the light collection efficiency and the polarization conversion efficiency are dramatically improved.

Next, a second embodiment will be described with reference to FIG. The difference from the first embodiment is that the parabolic reflector 2 is a spherical reflector 8a and the aperture spherical reflector 3 is a collimator lens 9. The white light source 1 is disposed substantially at the focal position of the spherical reflecting mirror 8a, and further disposed substantially at the focal position of the collimator lens 9. Therefore,
Most of the light emitted from the white light source 1 is a spherical reflecting mirror 8a.
The light is condensed by the collimator lens 9 and converted into parallel light. The light converted into parallel light is subjected to polarization plane modulation by the quarter-wave plate 4 and is incident on the polarization beam splitter 5, where the P-polarized component is transmitted but the S-polarized component is reflected.
And 7 are reflected. The reflected S-polarized light component passes through the quarter-wave plate again and is converted into circularly polarized light. Further, the light is condensed at the position of the white light source 1 by the collimator lens 9, becomes divergent light, and is reflected by the spherical reflecting mirror 8a.
The light is condensed again at the position of the white light source 1, becomes divergent light, and is converted into parallel light by the collimator lens 9. The circularly polarized light beam converted into parallel light passes through the quarter-wave plate 4 and is converted into P-polarized light, so that it can pass through the polarizing beam splitter 5. As described above, by using the present invention, linearly polarized light can be efficiently obtained.

Next, a third embodiment will be described with reference to FIG. The difference from the second embodiment is that the spherical reflecting mirror 8a is an elliptical reflecting mirror 8b, the white light source 1 is disposed at a position substantially coincident with the focal position on the side closer to the elliptical reflecting mirror 8b, and furthermore, a collimator lens. 9 is an elliptical reflecting mirror whose focal position is 8
It is arranged to substantially coincide with the other focal point of b. Therefore, most of the light emitted from the white light source 1 is condensed by the elliptical reflecting mirror 8b, the open spherical reflecting mirror 3 and the collimator lens 9, and is converted into parallel light. The light converted into the parallel light is polarization-modulated by the quarter-wave plate 4 and is incident on the polarization beam splitter 5, where the P-polarized light component is transmitted while the S-polarized light component is reflected by the reflection surfaces 6 and 7. The reflected S-polarized light component passes through the quarter-wave plate again and is converted into circularly polarized light. Further, the collimator lens 9 allows the collimator lens 3 of the elliptical reflecting mirror 8b to be formed.
At the focal point on the side, becomes divergent light again, is reflected by the ellipsoidal reflecting mirror 8b, condenses again at the position of the white light source 1, further diverges, and focuses on the collimator lens 3 side of the elliptical reflecting mirror 8b. Focus at the position, further diverge and collimator lens 9
Is converted into parallel light. The circularly polarized light beam converted into parallel light passes through the quarter-wave plate 4 and is converted into P-polarized light, so that it can pass through the polarizing beam splitter 9. As described above, by using the present invention, linearly polarized light can be efficiently obtained. The substantially parallel light rays converted into linearly polarized light by the color separation optical system shown in FIG. 4 are transmitted by the dichroic mirror 10 to red light, and the other lights are reflected. The reflected light is transmitted by the dichroic mirror 11 for blue light and is reflected for green light. The transmitted blue light is reflected by the mirror 12,
The liquid crystal light valve 20 is irradiated by the condenser lens 19. The blue light having the transmitted image information passes through the dichroic mirror 21 and enters the projection lens 22. The red light transmitted through the dichroic mirror 10 is reflected by the mirror 13 and is irradiated on the liquid crystal light valve 15 by the condenser lens 14. The transmitted red light passes through the dichroic mirror 16, is further reflected by the dichroic mirror 21, and enters the projection lens 22. The green light reflected by the dichroic mirror 11 is applied to the liquid crystal light valve 18 by the condenser lens 17. The transmitted green light is reflected by the dichroic mirror 16, further reflected by the dichroic mirror 21, and enters the projection lens 22. Each pixel of the liquid crystal light valves 15, 18, and 20 is turned on and off according to image data, and the amount of transmitted light is controlled. The red, blue, and green image information incident on the projection lens 22 are superimposed and projected on a screen as a final image. All of the liquid crystal light valves used in the color separation optical system shown in FIG. 4 have no polarizing plate for polarization conversion on the light incident side, and the alignment direction of the liquid crystal and the polarization direction of the incident light coincide. Therefore, the projection efficiency can be improved.

Next, a fourth embodiment will be described.
FIG. 5 is a schematic configuration diagram of an optical system that separates a light beam condensed by a condensing optical system into red, blue, and green light and linearly polarizes it. The feature of the present invention is to use a combination of a quarter-wave plate and a polarizing beam splitter optimized for each central wavelength of red, blue and green so that each color has a linear polarization function independently. It is composed. That is, the quarter-wave plate 27 and the polarizing beam splitter 28 are optimized for the center wavelength of red, and the red light of the S-polarized component reflected by the polarizing beam splitter 28 is shown in FIG. 1, FIG. 2 or FIG. Returning to the condensing optical system excluding the polarization conversion optical system described above, the light again enters the polarization conversion optical system including the quarter-wave plate 27 and the polarization beam splitter 28, and the red light is efficiently converted to P-polarized light. . Similarly, the quarter-wave plate 23 and the polarizing beam splitter 24 are optimized for the center wavelength of green, and the green light is efficiently converted to P-polarized light. Further, the quarter-wave plate 25 and the polarizing beam splitter 26 are optimized for the center wavelength of blue, and the blue light is efficiently converted to P-polarized light. As described above, since red, green and blue are independently subjected to P-polarization conversion, extremely high quality linearly polarized light can be obtained for each primary color. In this manner, the linearly polarized light beam enters the projection lens 22. Each pixel of the liquid crystal light valves 15, 18 and 20 is turned on and off according to image data, the amount of light transmission is controlled, and red, blue and green image information are superimposed and projected on a screen as a final image. . All the liquid crystal light valves used in the color separation optical system shown in FIG. 5 have no polarizing plate for polarization conversion on the light incident side, and the alignment direction of the liquid crystal and the polarization direction of the incident light are matched. , Can greatly improve the projection efficiency.

It is desirable that the dichroic mirrors 10, 11, 16 and 21 and the mirrors 12 and 13 shown in the fourth embodiment of the present invention have a small polarization dependence of the reflectance and transmittance.

[0016]

By using the illuminating device for a liquid crystal projector of the present invention, the efficiency is extremely improved by combining a quarter-wave plate and a polarizing beam splitter instead of the polarizing plate used for linear polarization. Linear polarization can be achieved. The synergistic effect of the condensing optical system formed by combining the parabolic reflector and the spherical reflecting mirror and the polarization conversion optical system formed by combining the quarter-wave plate and the polarizing beam splitter is particularly large. Further, by independently providing the polarization conversion optical system for each of red, green, and blue, the polarization conversion efficiency can be dramatically improved.

[Brief description of the drawings]

FIG. 1 is a schematic optical system configuration diagram of an irradiation device for a liquid crystal projector of the present invention.

FIG. 2 is a schematic optical system configuration diagram of another irradiation apparatus for a liquid crystal projector according to the present invention.

FIG. 3 is a schematic optical system configuration diagram of another irradiation apparatus for a liquid crystal projector according to the present invention.

FIG. 4 is a schematic configuration diagram of a conventional color separation optical system.

FIG. 5 is a schematic configuration diagram of a polarization conversion optical system and a color separation optical system of the present invention.

[Name of code]

 REFERENCE SIGNS LIST 1 White light source 2 Parabolic reflector 3 Open spherical reflector 4 Quarter-wave plate 5 Polarizing beam splitter 6 Reflecting surface 7 Reflecting surface 8 a Spherical reflector 8 b Elliptical reflector 9 Collimator lens 10 Dichroic mirror 11 Dichroic mirror DESCRIPTION OF SYMBOLS 12 Mirror 13 Mirror 14 Condenser lens 15 Liquid crystal light valve 16 Dichroic mirror 17 Condenser lens 18 Liquid crystal light valve 19 Condenser lens 20 Liquid crystal light valve 21 Dichroic mirror 22 Projection lens 23 Quarter wave plate 24 Polarizing beam splitter 25 Quarter Wave plate 26 Polarizing beam splitter 27 Quarter wave plate 28 Polarizing beam splitter

Continuation of the front page (51) Int.Cl. ⁶ Identification code Reference number in the agency FI Technical display location G03B 33/12 G03B 33/12

Claims (7)

[Claims] 1. A white light source is disposed substantially at a focal position of a first reflecting mirror having a curved surface, and a focal position of a second reflecting mirror having a curved surface and having an opening at a central portion substantially coincides with the light source. So that the first and second reflectors face each other and that the second reflector is located between the first reflector and the quarter wave plate. And an illuminating device for a liquid crystal projector, wherein the polarizing beam splitter is arranged so that the quarter-wave plate is located between the second reflecting mirror and the polarizing beam splitter. 2. The illuminating device for a liquid crystal projector according to claim 1, wherein said first reflecting mirror is a parabolic reflecting mirror, and said second reflecting mirror is a spherical reflecting mirror. 3. The method according to claim 1, wherein the first reflecting mirror is a spherical reflecting mirror, a collimator lens is used in place of the second reflecting mirror, and a focal point of the collimator lens coincides with a position of the white light source. The irradiation device for a liquid crystal projector according to claim 1, wherein: 4. The first reflecting mirror is an elliptical reflecting mirror, and the white light source is disposed at a position substantially coincident with a focal position existing on the first reflecting mirror side, and the first reflecting mirror is provided. 5. The collimator lens according to claim 1, wherein the other focal position of the mirror substantially coincides with the focal position of the collimator lens.
The irradiation device for a liquid crystal projector according to the above. 5. The illuminating device for a liquid crystal projector according to claim 1, wherein the polarizing beam splitter has two reflecting surfaces, and the two reflecting surfaces are orthogonal to each other. 6. The apparatus according to claim 1, wherein a high-speed axis or a low-speed axis of the quarter-wave plate is at 45 degrees with respect to an incident surface formed by a reflection surface of the polarization beam splitter and an incident light beam. Irradiation device for liquid crystal projector. 7. A white light source is disposed substantially at a focal position of a first reflecting mirror having a curved surface, and a focal position of a second reflecting mirror having a curved surface and having an opening at a central portion substantially coincides with the light source. The first and second reflectors face each other, the white light source is separated into red, green and blue by two dichroic mirrors,
A liquid crystal having a configuration in which an optical element composed of a wave plate and the polarizing beam splitter is independently arranged for each color light beam, and the red, green and blue colors are combined by a third dichroic mirror. Irradiation device for projector.