Optics: image projectors – Polarizer or interference filter
Reexamination Certificate
2001-12-31
2003-09-23
Dowling, William C. (Department: 2851)
Optics: image projectors
Polarizer or interference filter
C359S487030, C359S506000
Reexamination Certificate
active
06623121
ABSTRACT:
This application claims the benefit of Japanese Patent application No. 2000-000720 which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polarization beam splitter used for polarization-splitting into an S-polarized light component and a P-polarized light component and synthesizing these light components, an optical device for a projection type display device including this beam splitter, a projection type display device, and a polarization beam splitter manufacturing method.
2. Related Background Art
A polarization beam splitter that is generally used is provided with dielectric substance multi-layered film in which a dielectric substance layer composed of a high refractive index substance and a dielectric substance layer composed of a low refractive index substance are so multi-layered as to be alternately stacked between two pieces of rectangular prisms. It is, however, difficult for the single dielectric substance multi-layered film to polarization-split and synthesize the light in a broad wavelength band. This being the case, a 2-tiered dielectric substance multi-layer film including a first tier for reflecting the light having a long wavelength and a second tier for reflecting the light having a short wavelength, is used in many cases. The thus constructed polarization beam splitter is disclosed in, e.g., Japanese Patent Application Laid-Open No. 7-281024.
FIG. 15
is a diagram showing a configuration of the conventional polarization beam splitter disclosed in Japanese Patent Application Laid-Open No. 7-281024. A tier
3
for reflecting the light in a long wavelength (680 nm) region and a tier
4
for reflecting the light in a short wavelength (420 nm) region, are provided between two pieces of rectangular prisms
1
,
2
. Then, the two prisms
1
,
2
are bonded by an optical bonding agent
5
through the tiers
3
,
4
.
A complex refractive index of the substance composing the dielectric substance multi-layered film may be expressed by n−ik, where n is a refractive index, and k is an attenuation coefficient. The refractive index n and the attenuation coefficient k have dispersions. Namely, the refractive index n and the attenuation coefficient k change depending on a wavelength &lgr;. Hence, the refractive index n and the attenuation coefficient k increase as the wavelength &lgr; decreases. Accordingly, the absorption by the dielectric substance multi-layered film becomes large in the short wavelength region. Therefore, this results in a large exothermic quantity due to the absorption. When the exothermic quantity increases, a glass constituting the prism is distorted due to a thermal stress, and a polarized state of the polarization beam splitter is disordered. As a result, there arises a problem of causing a decline of contrast of a projected image in the projection type display device using the polarization beam splitter.
SUMMARY OF THE INVENTION
It is a primary object of the present invention, which was devised to obviate the problems described above, to provide a polarization beam splitter having a high polarized light splitting ratio and a broad bandwidth of the wavelength to be used, a manufacturing method thereof, an optical device for a projection type display device capable of obtaining a high-contrast projected image with a less distortion, and a projection type display device.
To accomplish the above object, according to one aspect of the present invention, a polarization beam splitter comprises a first prism having a first aggregation layer formed on a predetermined surface of the first prism and reflecting S-polarized light in a first wavelength region, and a second aggregation layer so formed as to be stacked on the first aggregation layer and reflecting the S-polarized light in a second wavelength region longer than the first wavelength region, and a second prism fixed to the first prism through the first aggregation layer and the second aggregation layer.
According to another aspect of the present invention, an optical device for a projection type display device, comprises a polarized light splitting optical system for polarization-splitting the light emitted from a light source and letting the split light exit, and an analyzing optical system for letting light emitted from light valves for modulating incident light in accordance with an image signal enter its incidence surface, analyzing the same light and letting the light exit its exit surface, wherein the analyzing optical system includes a first aggregation layer reflecting S-polarized light in a first wavelength region and a second aggregation layer reflecting the S-polarized light in a second wavelength region longer than the first wavelength region between transparent optical members, and the first aggregation layer is provided closer to an incidence surface of the analyzing optical system than the second aggregation layer.
According to still another aspect of the present invention, an optical device for a projection type display device comprises a polarized light splitting optical system for polarization-splitting the light emitted from a light source and letting the split light exit, and an analyzing optical system for analyzed light emitted from light valves for modulating incident light in accordance with an image signal, wherein one polarization beam splitter functioning as the polarized light splitting optical system and as the analyzing optical system is provided, the polarization beam splitter contains a reflection layer reflecting S-polarized light in a first wavelength region, and a reflection layer reflecting the S-polarized light in a second wavelength region longer than the first wavelength region, and the light from the light source and the light from the light valves are incident at first upon the reflection layer reflecting the S-polarized light in the first wavelength region.
According to yet another aspect of the present invention, a projection type display device comprises a light source for supplying irradiation light, a polarized light splitting optical system for polarization-splitting the irradiation light from the light source and letting the split light exit, light valves for modulating the incident light in accordance with image signals, an analyzing optical system for making the exit light from the light valves incident upon its incidence surface, analyzing the incident light and letting the light exit its exit surface, and a projection optical system, disposed on the side of the exit surface of the analyzing optical system, for projecting an image from the light valves, wherein the analyzing optical system includes a first aggregation layer reflecting S-polarized light in a first wavelength region and a second aggregation layer reflecting the S-polarized light in a second wavelength region longer than the first wavelength region between transparent optical members, and the first aggregation layer is provided closer to an incidence surface of the analyzing optical system than the second aggregation layer.
According to a further aspect of the present invention, a projection type display device comprises a light source for supplying irradiation light, a polarized light splitting optical system for polarization-splitting the irradiation light from the light source and letting the split light exit, light valves for modulating the incident light in accordance with image signals, an analyzing optical system for analyzing the exit light from the light valves, a projection optical system, disposed on the exit side of the analyzing optical system, for projecting an image from the light valves, wherein one polarization beam splitter functioning as the polarized light splitting optical system and as the analyzing optical system is provided, the polarization beam splitter contains a reflection layer reflecting S-polarized light in a first wavelength region, and a reflection layer reflecting the S-polarized light in a second wavelength region longer than the first wavelength region, and the light
Dowling William C.
Nikon Corporation
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