JPH052150A - Polarized light source device - Google Patents

Abstract

PURPOSE:To convert all light into light which is polarized in the constant direction without using any polarizing plate, to double the quantity of light, and to prevent thermal deterioration of a polarizing plate. CONSTITUTION:Nearly parallel converged light 31 from a light source means 30 is diffracted spectrally by a polarization beam splitter 33 into reflected linearly polarized light (S wave) 35 and transmitted linearly polarized light (P wave) 36. The P wave 36 is inverted by striking on a reflecting means 37, made reversely incident on the polarization beam splitter 33 and transmitted, and transmitted through a linearly polarized light rotating means 32 to become linearly polarized light 38 which is rotated clockwise by 45 deg. and this light is reflected and inverted by a reflector 2, and made incident on and transmitted through the linearly polarized light rotating means 32 to have its polarizing direction rotated clockwise by 45 deg. and linearly polarized light (P wave) which is in phase with the S wave 35 is obtained. This P wave 39 is made incident on the polarization beam splitting means 33, reflected at right angles to the optical axis of natural light 31, and put on the same optical axis with the S wave 35 which is difference spectrally in advance.

Description

Detailed Description of the Invention

[0001]

The present invention relates to red (R), green (G),
The present invention relates to a polarized light source device which is suitable for application to a liquid crystal color projection type display in which display images of black and white liquid crystal plates provided separately for blue (B) are color-mixed and projected.

[0002]

2. Description of the Related Art In recent years, with the trend toward larger screens of televisions, a liquid crystal projection display for enlarging and projecting an image of a liquid crystal television panel on a screen is required for its small size, light weight and easy handling. Attention has been paid. However, when comparing the liquid crystal projection display with the CRT (cathode ray tube) image projection display, which is currently the mainstream of projection displays and has a high degree of perfection, the resolution and brightness are still unsatisfactory, and there is room for improvement.

Regarding resolution, development of high-definition liquid crystal television panels is in progress. Regarding brightness, a liquid crystal projection display that can separate the image formation and the light source is more advantageous, but it is 1/2 to 1/1 compared to the standard CRT method.
It is still around 3 A quick way to increase the projected light flux is to use a high light output lamp, but this is not practical because it results in increased power consumption and component degradation due to increased device temperature.

FIG. 3 is a schematic view showing a conventional example of a liquid crystal color projection type display called a mirror system using a dichroic mirror for color separation and mixing of light. In the figure, reference numeral 1 denotes a light source such as a xenon lamp, and the light emitted from the light source 1 is reflected by a reflecting mirror 2 which has a reflecting surface having a parabolic surface and which makes the light source light parallel light parallel to the optical axis. Liquid crystal plate 7,
A condenser lens (not shown) arranged immediately before the lenses 12 and 15 converges the light toward the projection optical system 19. At this time,
The converged parallel rays enter the blue dichroic mirror 4 that separates and reflects only the blue light. The blue light 5 separated by the blue dichroic mirror 4 is converged by the mirror 6 in the optical system 3
The light is reflected in parallel to the optical axis of and enters the transmissive liquid crystal panel 7. A voltage is selectively supplied to the liquid crystal panel 7 according to constituent pixels of an arbitrary image to be projected, and the blue light 5 transmitted through the liquid crystal panel 7 becomes a blue image light 5a having a video signal.

The blue dichroic mirror 4 loses the blue component 5 and the light transmitted through the mirror 4 becomes yellow. The yellow light 8 is incident on the red dichroic mirror 9, and the red light 10
Is separated, and the remaining green light 11 passes through the mirror 9. The separated red light 10 is incident on a transmissive liquid crystal panel 12 having the same structure as the liquid crystal panel 7, and the red image light 1
It becomes 0a. The blue image light 5a and the red image light 10a are mixed by the mixing dichroic mirror 13 to become magenta image light 14.

On the other hand, the green light 11 also enters the transmission type liquid crystal panel 15 having the same structure as the liquid crystal panel 7, becomes green image light 11a, is reflected by the mirror 16 and enters the mixing dichroic mirror 17. The green image light 11a and the magenta color image light 14 are mixed with the dichroic mirror 1 for mixing.
7 is mixed and becomes the RGB additive color mixed image light 18, which is enlarged and projected onto the large screen 20 through the projection optical system 19 to reproduce a color image.

FIG. 4 shows a transmissive liquid crystal panel 7 (liquid crystal panel 1
2 and 15 are also the same) (illustration is omitted in FIG. 3), and two polarizing plates 21A and 21B provided on both sides are provided. The reason is that the liquid crystal used in the liquid crystal panel 7 (twisted nematic liquid crystal) does not transmit or block light depending on the voltage application state, but rotates the polarization plane of incident light. is there. That is, when natural light of which the polarization direction is not determined is incident, it is emitted as natural light regardless of the voltage application state, and therefore, even if an image is formed on the liquid crystal panel, it cannot be recognized. Therefore, first, a polarizing plate 21A is placed in front of the liquid crystal panel 7, and only natural polarized light of a certain direction is transmitted and converted into linear polarized light. That is, when natural light passes through the polarizing plate 21A, it is decomposed into two linearly polarized lights that are orthogonal to each other, and of these, the components parallel to the polarization direction are transmitted and the orthogonal components are absorbed. Then, when linearly polarized light parallel to the polarization direction is incident on the liquid crystal panel 7, the polarization direction is partially rotated according to the image and exits from the liquid crystal panel 7. Here, when the polarizing plate 21B is used again to transmit only light polarized in a certain direction, a grayscale image is obtained. The component orthogonal to the polarization direction is the polarizing plate 21A.
When absorbed by, it is converted into heat.

[0008]

As is apparent from the above, in the conventional device, the polarizing plate 21A is changed from the natural light.
Since at least half of the light is absorbed by the polarizing plate 21A at the stage of extracting the linearly polarized light polarized in (2), there is a problem in that the light is effectively used. Further, the absorbed light is converted into heat and raises the temperature of the polarizing plate 21A.
There was also an incidental problem of degrading 1A. Therefore, not only the polarized component in a certain direction is extracted from the natural light by the polarizing plate 21A, but all the light from the light source can be converted into the polarized light in the certain direction, and the amount of light is increased and the polarizing plate by heat is generated. There is a demand for the development of a device that can solve the problem of deterioration. The problem of the deterioration of the second polarizing plate 21B is that the opening portion of the liquid crystal panel 7 is about 40% of the total area (the increase of the opening ratio is also an important factor for increasing the brightness of the liquid crystal color projection display). Therefore, it is not a problem as much as the first polarizing plate 21A.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to make all light constant without using a polarizing plate at the stage of extracting linearly polarized light from natural light. It is an object of the present invention to provide a polarized light source device capable of being converted into light polarized in a direction and capable of solving the problem of deterioration of a polarizing plate due to heat as well as doubling the amount of light.

[0010]

In order to achieve the above object, the present invention is provided with a light source means having a reflector such as a paraboloid of revolution, and a substantially parallel optical axis of convergent light from the light source means. A polarized beam splitting means for splitting the converged light into a transmitted linearly polarized light (P wave) and a reflected linearly polarized light (S wave), and a 180 ° reflection of the transmitted linearly polarized light and a reverse incidence on the polarized beam splitting means. And a linear polarization rotating means for rotating the polarization direction of the transmitted linearly polarized light (P wave) which is reflected by the reflecting means by 180 ° and transmitted through the polarized beam splitting means again by 45 °. The means is disposed between the light source means and the polarized beam splitting means so as to be orthogonal to the optical axis, and the transmitted linearly polarized light whose polarization direction is rotated by 45 ° by the linearly polarized light rotating means ( Waves) in the reflector 180
When the light is reflected and is incident back to the linear polarization rotation means and transmitted therethrough, the polarization direction is further rotated by 45 degrees in the same direction to enter the polarization beam splitting means and reflected in a direction orthogonal to the optical axis of natural light. Thus, the reflected linearly polarized light (S wave) is combined.

[0011]

In the present invention, the natural light which is converged and emitted from the light source means substantially in parallel does not affect the natural light and is transmitted through the linear polarized light rotating means for rotating the linear polarized light by 45 ° in the clockwise direction as it is. Incident on the polarized beam splitting means. The polarized beam splitting means reflects the incident natural light into reflected linearly polarized light (S wave) and transmitted linearly polarized light (P wave).
Wave). The S wave is reflected in the direction perpendicular to the optical axis of natural light, and the P wave is transmitted as it is. The P wave transmitted through the polarized beam splitting means is 180 ° by the reflecting means.
The reflected light returns through the original optical path, is incident back to the polarized beam splitting means, is transmitted therethrough, and is further incident on the linear polarization rotating means. The P-wave incident on the linearly polarized light rotating means is rotated by 45 ° in the clockwise direction and is transmitted therethrough.
After being reflected by 0 °, it is incident on the linearly polarized light rotating means again. The P wave incident on the linear polarization rotating means is further rotated clockwise by 45 ° so that its phase becomes the same phase as the S wave and enters the polarization beam splitting means, and is orthogonal to the optical axis of the P wave. By being reflected in the direction, it is combined on the same optical axis as the S wave previously dispersed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. FIG. 1 is a schematic view showing an embodiment of a polarized light source device according to the present invention. FIG. 2 is a conceptual diagram for explaining the transmission state of the polarized light in FIG. In these figures, 30 is a light source means, 32 is a linear polarization rotation means,
33 is a polarized beam splitting means, 37 is a reflecting means,
These constitute a polarized light source device. The light source means 30 includes an arc lamp 1 and a reflector 2 whose reflection surface is a parabolic surface, which is the same as the conventional one. Arc lamp 1
The natural light 31 emitted from the light source is converged by the reflector 2 substantially in parallel with the optical axis, and then enters the linearly polarized light rotating means 32. The linearly polarized light rotating means 32 rotates the linearly polarized light clockwise without affecting the natural light, and changes the phase of the transmitted light by the birefringence of the medium to rotate the polarization direction by 45 °. A quarter wave plate made of an optical crystal such as a quartz plate or a polyvinyl alcohol film stretched to cause birefringence is used. Therefore, the natural light 31 incident on the linearly polarized light rotating means 32 is transmitted as it is. Then, the natural light 3 transmitted through the linear polarization rotation means 32
1 is incident on the polarized beam splitting means 33, where the reflected linearly polarized light (S wave) 35 shown by the solid line in FIG. 1 and the transmitted linearly polarized light (P wave) 36 shown by the dotted line (hatched in FIG. 2). The S wave 35 is reflected in the direction perpendicular to the optical axis of the natural light 31, while P wave
The wave 36 is transmitted as it is. The polarized beam splitting means 33 is one in which a dielectric multilayer film 34 is vapor-deposited on one slanted surface of one of two right-angle prisms, and the slanted surfaces are joined together. The natural light 31 is two linearly polarized light beams whose polarization directions are orthogonal to each other. The light transmitted through the slope is P-polarized light, and the light reflected on the slope is S-polarized light. The linearly polarized light (S wave) 35 is linearly polarized light having a component that oscillates in the direction perpendicular to the paper surface in FIG. 1, and the linearly polarized light (P wave) 36 is parallel to the paper surface and is in the traveling direction. It is linearly polarized light having a component that oscillates in a direction orthogonal to.

The P-wave 36 transmitted through the polarized beam splitting means 33 is reflected by 180 ° by a reflecting means 37 such as a total reflection mirror arranged orthogonal to the optical axis of the P-wave, so that the original optical path is changed. The light beam passes through the polarized beam splitting means 33 through the reverse direction, passes through the polarized beam splitting means 33, and enters the linear polarization rotating means 32. The phase of this P wave 36 does not change even by reflection by the reflection means 37 and re-transmission of the polarized beam splitting means 33, but when it enters the linear polarization rotation means 32, it will be affected by the characteristics of the linear polarization rotation means 32 described above. The phase becomes a P wave 38 rotated clockwise by 45 °, passes through the linear polarization rotation means 32, is reflected 180 ° by the reflector 2 in the same phase, goes backward, and re-enters the linear polarization rotation means 32. ..

45 ° re-incident on the linear polarization rotating means 32
The P-wave 38, which is the rotating linearly polarized light, is further rotated clockwise by 45 °, and the phase thereof is the same as that of the S-wave 35, that is, the linearly-polarized light 3 having a phase rotation of 90 ° with respect to the P-wave 36.
9 is incident on the polarized beam splitting means 33,
The natural light 31 is reflected in a direction perpendicular to the optical axis and is combined on the same optical axis as the previously dispersed S wave 35. Therefore, all the natural light 31 emitted from the light source means 30 can be extracted as reflected linearly polarized light (S wave) without loss,
The amount of polarized light that enters the liquid crystal panel can be doubled. Further, unlike the conventional apparatus, since no polarizing plate is required, the problem of deterioration of the polarizing plate due to heat can be solved.

[0015]

As described above, according to the polarized light source device of the present invention, when the linearly polarized light is extracted from the natural light, all the light beams having different phases are polarized in a fixed direction without using the polarizing plate. Since it can be converted into light, the amount of light can be increased without loss of light, and the problem of deterioration of the polarizing plate caused by temperature rise due to light absorption that occurs when a polarizing plate is used as in the past Can also be resolved.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a polarized light source device according to the present invention.

FIG. 2 is a conceptual diagram for explaining a transmission state of polarized light in FIG.

FIG. 3 is a schematic view showing a conventional example of a liquid crystal color projection device.

FIG. 4 is a diagram showing a configuration of a liquid crystal panel and a polarizing plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 4, 11 Spectral dichroic mirror 7, 12, 15 Liquid crystal panel 13, 17, 31 Synthetic dichroic mirror 30 Light source means 32 Linearly polarized light rotation means 33 Polarized beam splitting means 37 Reflecting means

Claims (1)

Claim: What is claimed is: 1. A light source means having a reflector such as a rotating paraboloid, and a substantially parallel optical axis of the convergent light from the light source means. Polarized beam splitting means for splitting light (P-wave) and reflected linearly polarized light (S-wave), reflecting means for reflecting the transmitted linearly polarized light by 180 ° and making it enter the polarized beam splitting means in reverse, and this reflecting means. Linear polarization rotation means for rotating the polarization direction of the transmitted linearly polarized light (P wave) which is reflected by 180 ° by the above and re-transmitted through the polarized beam splitting means by 45 °,
The linearly polarized light rotating means is disposed between the light source means and the polarized beam splitting means so as to be orthogonal to the optical axis, and the transmitted linearly polarized light (P 18) with the reflector
When it is reflected by 0 ° and is incident back to the linearly polarized light rotating means and is transmitted therethrough, the polarization direction is further rotated by 45 ° in the same direction to enter the polarized beam splitting means and reflected in a direction orthogonal to the optical axis of natural light. The polarized light source device is characterized by being combined with the reflected linearly polarized light (S wave).