Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
1999-02-19
2001-06-26
Adams, Russell (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S032000, C353S034000, C353S081000, C359S584000
Reexamination Certificate
active
06250764
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a polarizing beam splitter for splitting incident light into two types of polarized light, and a polarizing conversion element and a projection display apparatus which are provided with the polarizing beam splitter.
2. Description of Related Art
Generally, a projection display apparatus includes an element referred to as “a light valve” for modulating light in response to picture signals. In many cases, a transmissive liquid crystal panel or a reflective liquid crystal panel is used as a light valve, in which only one type of linear polarized light is employed. In such a projection display apparatus that employs one type of linear polarized light, a polarizing conversion element is included for converting unpolarized incident light emitted from a light source into one type of linear polarized light (e.g., s-polarized light).
SUMMARY OF THE INVENTION
In order to increase luminance of images displayed on a projection screen, it is desirable that unpolarized light entered into a polarizing conversion element be efficiently converted into one type of linear polarized light. That is, the transmission and reflection properties of a polarization separating film and the reflection property of a reflecting film, which are provided on the polarizing conversion element, are desirably enhanced as much as possible. Also, with respect to polarizing beam splitters or polarizing conversion elements used for other devices than projection display apparatuses, improvement in the transmission property and the reflection property have been desired.
The present invention overcomes the problems noted above with respect to the related art. It is an object of this invention to provide a technique for improving properties of polarizing beam splitters and polarizing conversion elements. It is another object of this invention to provide projection display apparatuses having high light utilization efficiency using such polarizing beam splitters.
In order to solve at least one problem described above, a first element of the present invention is a polarizing beam splitter for splitting incident light into two types of polarized light, the polarizing beam splitter including a light transmissive substrate having a refractive index ranging from approximately 1.48 to 1.58, and a polarization separating film formed on the light transmissive substrate. The polarization separating film is provided with a multilayered structural section including MgF
2
layers and MgO layers alternately arranged.
This polarizing beam splitter can improve the transmission property with respect to one polarized light and the reflection property with respect to other polarized light by using the multilayered structural section composed of MgF
2
and MgO.
In the polarizing beam splitter described above, the polarization separating film preferably includes a coating layer composed of SiO
2
on the multilayered structural section.
Thereby, when the polarization separating film formed on the substrate is adhered to other member by an optical adhesive, adhesion between the polarization separating film and the other member can be increased.
A second element of the present invention is a polarizing beam splitter, for splitting incident light into two types of polarized light, the polarizing beam splitter including a light transmissive substrate having a refractive index ranging from approximately 1.48 to 1.58, and a polarization separating film formed on the light transmissive substrate. The polarization separating film is provided with a multilayered structural section including a plurality of layers, and a coating layer composed of SiO
2
formed on the multilayered structural section.
Since the polarizing beam splitter is provided with the coating layer composed of SiO
2
formed on the multilayered structural section, when the polarization separating film formed on the substrate is adhered to another member by an optical adhesive, adhesion between the polarization separating film and the other member can be increased.
A third element of the present invention is a polarizing conversion element for converting incident light into one type of polarized light, the polarizing conversion element including a polarizing beam splitter for splitting incident light into a first type and a second type of polarized light, and a selective phase plate for converting the first type of polarized light into the second type of polarized light. The polarizing beam splitter includes a plurality of light transmissive substrates placed along a given direction, and a plurality of polarization separating films and a plurality of reflecting films alternately placed between the plurality of light transmissive substrates. Each of the light transmissive substrates has a refractive index ranging from approximately 1.48 to 1.58, and each of the polarization separating films is provided with a multilayered structural section including MgF
2
layers and MgO layers alternately arranged.
Since the polarizing conversion element employs the multilayered structural section composed of MgF
2
and MgO as the polarization separating film, incident light can be efficiently converted into one type of polarized light.
A fourth element of the present invention is a polarizing conversion element for converting incident light into one type of polarized light, the polarizing conversion element including a polarizing beam splitter for splitting incident light into a first type and a second type of polarized light, and a selective phase plate for converting the first type of polarized light into the second type of polarized light. The polarizing beam splitter includes a plurality of light transmissive substrates placed along a given direction, and a plurality of polarization separating films and a plurality of reflecting films alternately placed between the plurality of light transmissive substrates. Each of the light transmissive substrates has a refractive index ranging from approximately 1.48 to 1.58. Each of the polarization separating films is provided with a multilayered structural section including a plurality of layers, and a coating layer composed of SiO
2
formed on the multilayered structural section.
Since the polarizing beam splitter in the polarizing conversion element is provided with the coating layer composed of SiO
2
formed on the multilayered structural section, when the polarization separating film formed on the substrate is adhered to another member by an optical adhesive, adhesion between the polarization separating film and the other member can be increased.
In accordance with the third or fourth polarizing conversion element described above, the reflecting film may have the same structure as that of the polarization separating film.
This makes it possible to use both the polarization separating film and the reflecting film as either film because of their same structure, and thereby, the fabrication of the films is facilitated.
In accordance with the polarizing conversion element described above, the reflecting film may include a multilayered structural section having a first layer and a second layer alternately arranged, the first layer having a lower refractive index and the second layer having a higher refractive index in comparison with a refractive index of the light transmissive substrate. The first layer of the reflecting film may be composed of SiO
2
, and the second layer may be composed of Ta
2
O, or TiO
2
.
As described above, by using the multilayered structural section composed of SiO
2
and Ta
2
O
5
or a reflection film including the multilayered structural section composed of SiO
2
and TiO
2
as the reflecting film, a higher reflectance can be obtained with a smaller number of layers in comparison with a case in which the polarization separating film has the same structure as that of the reflecting film as described above.
In the polarizing conversion element described above, the second layer is preferably a TiO
2
layer formed by placing evaporated TiO
2
in a plasm
Aoki Kazuo
Endo Yukihiro
Adams Russell
Brown Khaled
Oliff & Berridg,e PLC
Seiko Epson Corporation
LandOfFree
Polarization beam splitter, polarization converter, and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polarization beam splitter, polarization converter, and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polarization beam splitter, polarization converter, and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2511194