Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
1997-11-12
2002-05-28
Metjahic, Safet (Department: 2858)
Optics: image projectors
Composite projected image
Multicolor picture
C353S020000
Reexamination Certificate
active
06394607
ABSTRACT:
TECHNICAL FIELD
This invention relates to a polarized light separation device, a method of fabricating the device and a projection display apparatus that uses this polarized light separation device.
BACKGROUND ART
FIG. 26
is a perspective drawing of a conventional polarization beam splitter. This device comprises triangular prisms to which polarized light separation films and aluminum reflective films are vapor-deposited and then the prisms are pasted together. To wit, prisms
71
,
72
,
73
and
74
are polished prisms made of the material BK7, and these four prisms form a unit that is repeated to make up the entire device. A polarized light separation film
75
is formed by vapor deposition as inorganic thin films on that surface of the prism
72
which is facing the prism
71
. In addition, an aluminum reflective film
76
is vapor-deposited on that surface of the prism
73
which is facing the prism
74
. The prisms
71
,
72
,
73
and
74
are pasted to each other's surfaces with adhesive. When a light beam
77
enters the prism
72
, at the polarized light separation film
75
, the P-polarized light component with respect to the plane of incident light passes through the prism
71
as transmitted light
77
and exits. On the other hand, the S-polarized light component is reflected by the polarized light separation film
75
then enters the prism
73
, is reflected by the reflective film
76
and leaves the device as an S-polarized light beam
78
. In this manner, a conventional polarization beam splitter is formed by pasting together prisms each of that has a polarized light separation film or a reflective film in a repetitive structure.
In the conventional method, the triangular prisms are each individually polished, vapor-deposited and pasted together, so it is not possible to reduce the size of the repetitive structure of polarized light separation film and reflective film to give the entire device a thin structure. This is because, were the size of the repetitive structure to be reduced, even smaller triangular prisms would need to be manufactured, and the edges of the prisms would be lost due to polishing so no light will pass through them, resulting in the problem of decreased brightness. In addition, achieving uniform heights among the prisms becomes more difficult the smaller the prism becomes. In addition, problems at the time of pasting the prisms together include angular misalignment, unevenness and bumpiness in the surfaces of light entry and exit, and other problems. Therefore, the edge areas that stick out due to unevenness are susceptible to cracking, and it is difficult to attach other optical elements to the surfaces of light entry and exit. In addition in the event of angular misalignment at the time that the prisms are pasted together, problems occur in which the optic axes of the incident light and emitted light change. The present invention gives proposed solutions to these problems.
DISCLOSURE OF THE INVENTION
In order to solve at least part of the above problems, a first method of the present invention is a method of manufacturing a polarized light separation device that separates light having random directions of polarization into two types of polarized light, comprising the steps of: forming a substrate block having a repetitive structure of a first substrate plate, a polarized light separation layer, a second substrate plate and a reflective layer; and cutting the substrate block at a predetermined angle with respect to surfaces of the substrate plates.
The above method has the meritorious effect that there is no need to polish the surfaces for the individual polarized light separation layers and reflective layers. In addition, it has the meritorious effect that the degree of parallelism between the repeated polarized light separation layers and reflective layers is higher than that of a structure wherein individual tetrahedral prisms are pasted together. Moreover, polarized light separation devices of the same structure with the same characteristics can be manufactured easily in large numbers by cutting them out of the substrate block.
In the first method, the step of forming a substrate block preferably comprises the steps of: forming the polarized light separation layers upon the first substrate plates; forming the reflective layers upon the second substrate plates; and alternately stacking the first substrate plates upon which the polarized light separation layers are formed and the second substrate plates upon which the reflective layers are formed. In this manner, the substrate block can be formed easily.
Further in the first method, in the step of alternately stacking the first substrate plates upon which the polarized light separation layers are formed and the second substrate plates upon which the reflective layers are formed, it is preferable that the first substrate plates and the second substrate plates are stacked alternately with their ends slightly offset by an amount depending on an angle at which the substrate block is to be cut.
By stacking the substrates with their ends slightly offset, the amount of substrate waste generated at the time of cutting of the substrate blocks can be reduced.
In the first method, the step of forming a substrate block preferably comprises the steps of: forming the polarized light separation layers upon the first substrate plates; forming the reflective layers upon the second substrate plates; stacking together one of the first substrate plates upon which the polarized light separation layers are formed and one of the second substrate plates upon which the reflective layers are formed, to thereby form a basic block; and stacking together a plurality of the basic blocks. In this manner, by merely stacking multiple substrate blocks, substrate blocks of the desired size can be formed easily.
In the step of stacking together a plurality of the basic blocks, the basic blocks are preferably stacked with their ends slightly offset by an amount depending on an angle at which the substrate block is to be cut. In this manner, the amount of substrate waste generated at the time of cutting of the substrates can be reduced.
Preferably the first method further comprises the step of: polishing a cut surface after the step of cutting the substrate block at a predetermined angle. The two cut surfaces polished in this manner will become flat surfaces of light entry and exit.
Preferably the first method further comprises the step of: stacking a dummy substrate upon at least one of the substrates making up both surfaces of the substrate block after the substrate block is formed. In this manner, the periphery is not damaged by cracking or breakage, and the loss of light passing through the periphery can be reduced.
Preferably, in the first method, the first substrate plate and the second substrate plate are polished glass plates. The polished glass plate is preferably white glass plates or non-alkali glass. Alternately, the first substrate plate and the second substrate plate are preferably float glass. By using polished plate glass or float glass, the precision of repetition of the polarized light separation film and reflective film can be easily improved inexpensively.
In the first method, one of the first substrate plate and the second substrate plate is preferably a colored light-transparent substrate and the other is a colorless light-transparent substrate. In this manner, the positions of the polarized light separation layers and reflective layers can be easily distinguished.
The reflective film may be made of a thin aluminum film or a thin dielectric film. Alternatively, the reflective film may be made of a thin aluminum film and a thin dielectric film.
A first polarized light separation device according to the present invention is manufactured by any one of the above methods of manufacturing a polarized light separation device. By means of this polarized light separation device, the repetitive structure of polarized light separation layers and reflective layers can be set depending on the thickness and q
Hashizume Toshiaki
Itoh Yoshitaka
Yajima Akitaka
LeRoux E P
Metjahic Safet
Seiko Epson Corporation
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