Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1997-07-25
2001-01-09
Vargot, Mathieu D. (Department: 1732)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C264S001700, C349S005000, C359S634000, C359S831000
Reexamination Certificate
active
06171421
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a prism assembly and a method for producing the prism assembly. More specifically, the present invention relates a prism assembly which performs color separation and color synthesis in, for example, an optical system in a liquid crystal projector or the like.
2. Description of the Related Art
Conventionally, in an optical system in a liquid crystal projector or the like, a prism assembly which performs color separation and color synthesis is used.
As shown in
FIGS. 23A and 23B
, a conventional prism assembly
90
of this type includes, for example, prisms
91
to
94
made of glass, and dichroic layers
96
and
97
formed on specific planes of the prisms
91
to
94
.
In the conventional prism assembly
90
, as shown in
FIGS. 23A and 23B
, red light is introduced through a light incidence plane denoted by the reference symbol “R light incidence plane”; green light is introduced through a light incidence plane denoted by the reference symbol “G light incidence plane”; and blue light is introduced through a light incidence plane denoted by the reference symbol “B light incidence plane”. Also, red, green and blue lights are emitted through a light emission plane denoted by the reference symbol “RGB lights emission plane”. Incidentally, each of these reference symbols denotes the same plane in the following description.
The conventional prism assembly
90
having the above-mentioned constitution is produced by the following method.
Incidentally, in the following description, each of the prisms constituting the prism assembly has five planes: three rectangular side planes and two right-angled-triangle-shaped base planes. Of these side planes, two side planes including the sides forming the right angle of the right-angled-triangle-shaped base plane are referred to as a “first plane” and a “second plane”, while the side plane including the hypotenuse of the triangle serving as the base plane is referred to a “third plane”.
Firstly, a glass block is roughly processed by pressing or cutting so as to form a rough contour of a prism of the prism assembly
90
.
Next, the roughly processed glass block is attached on a plate by means of paraffin, and then the first plane of the prism is processed.
The processing of the first plane includes rough shaving to a predetermined thickness, semi-finishing, and finishing, performed in this order. In the rough shaving, abrasive grains of C# 80 are used; in the semi-finishing, abrasive grains of A# 120 to 280 are used; and in the finishing, abrasive grains of A# 400 to 600 are used.
Thereafter, the paraffin is removed from the prism, and the prism is washed.
After the first plane is processed, the second plane and then the third plane are processed in the same steps as in the first plane.
In this way, the prisms
91
to
94
are produced.
Incidentally, a stock allowance for sanding and polishing each of the side planes is expected to be 0.07 to 0.1 mm for each of the side planes.
Thereafter, dichroic films
96
and
97
are directly coated on specific planes of the glass prism
92
. Then, the glass prisms
91
to
94
are joined to form the prism assembly
90
.
However, in the glass prisms
91
to
95
thus processed, the opposed sides of each plane are unfavorably liable to fail to be in parallel, so that pyramidal errors (falling-down errors) are liable to occur.
To avoid such errors, the producer must process the prisms
91
to
94
while paying attention to the following points in each of the steps of rough shaving, semi-finishing, and finishing. That is, in the processing of the third plane performed after processing the first and second planes, the producer must pay attention to causing the two angles formed between the third plane and the first and second planes (i.e., the two angles formed at both ends of the hypotenuse of the right-angled triangle-shaped base plane) to become equal to each other, and to causing the angles formed between the first to third planes and the upper and lower base planes to become right angles.
Because of the constitution and the production method as described above, in the conventional prism assembly and the conventional method for producing the prism assembly, a skilled expert needs to take a long time in order to produce a prism assembly having satisfactory precision in prism angles and planes. Consequently, according to the conventional method, it is difficult to produce such a prism assembly efficiently.
SUMMARY OF THE INVENTION
The present invention is accomplished in view of the above-mentioned problems of the conventional prism assembly and the conventional method for producing a prism assembly.
It is therefore an object of the present invention to provide a prism assembly which has stable precision in prism angles and planes and is suitable for mass-production.
It is another object of the present invention to provide a method for preferably producing such a prism assembly.
To achieve the above-mentioned objects, a first aspect of the invention provides a prism assembly including: a prism made of plastics having light transmittivity; and a glass plate which is joined to a plane of the prism obliquely intersecting a light incidence plane of the prism and whose one plane carries a dichroic layer formed thereon.
In the prism assembly according to the first aspect of the present invention, since the prisms are made of plastics which allows the prism angles and the dimensions of the prism to be changed easily, the prism assembly can take various shapes and dimensions.
Also, since the dichroic layer is formed on a glass plate which exhibits excellent plane precision, the dichroic layer can exhibit excellent plane precision. Accordingly, the prism assembly according to the first aspect of the present invention can realize dichroic properties of the same level as in the conventional prism assembly.
Further, a second aspect of the present invention provides a prism assembly having the features of the first aspect of the present invention and a feature that at least one of a plane serving as a light incidence plane of the prism assembly and a plane serving as a light emission plane of the prism assembly is shaped in the form of a lens.
In the prism assembly according to the second aspect of the present invention, since the prism assembly itself serves as a lens, the optical system placed after the prism assembly can have simple constitution.
Specifically, when the prism assembly according to the second aspect of the present invention is used for, for example, a liquid crystal projector having a lens group serving as a projection optical system for projecting the light emitted from the prism assembly to the screen, the number of lenses in the lens group can be reduced by at least one.
Further, a third aspect of the present invention provides a method for producing a prism assembly, including: a first step of forming a prism by injection-molding plastics having light transmittivity; a second step of forming a dichroic layer on a surface of a glass plate; and a third step of joining the glass plate carrying the dichroic layer formed thereon to a specific plane of the prism.
In the method for producing a prism assembly according to the third aspect of the present invention, since the prism is formed by injection-molding plastics having light transmittivity at the first step, the prism can be easily formed into a prism in conformity with desired specifications of the prism in prism angle and dimension.
Also, in the method for producing a prism assembly according to the third aspect of the present invention, the dichroic layer is formed on a glass plate at the second step performed before, after, or in parallel with the first step, and the glass plate carrying the dichroic layer formed thereon is joined to a specific plane of the prism at the third step. Accordingly, the prism assembly according to the first aspect of the present invention can be produced preferably.
Further, a fourth aspect of the present invention provid
Murata Kazuhiko
Sekine Kumajiro
Yokota Akihiro
Oliff & Berridg,e PLC
Sekinos Co., Ltd.
Vargot Mathieu D.
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