JPH1048406A - Dichroic prism and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dichroic prism having high accuracy at a low cost. SOLUTION: In the dichroic prism formed by joining four pieces of rectangular prisms which are formed with the required reflection films on the rectangular surfaces across the right angle and have approximately the same width respectively around the right angle parts, at least, the angle part formed by the rectangular surface of the second prism 2 which comes into contact with the first prism 1, and the surface orthogonal to this rectangular surface and the angle part formed by the rectangular surface of the fourth prism 4 which comes into contact with the third prism 3 and the surface orthogonal with this rectangular surface are subjected to chamfering 2d, 4d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dichroic prism used for a liquid crystal projector or the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the development of multimedia, various types of image devices are being developed and spread. Among them, liquid crystal projectors are used for presentations using personal computers, etc. It is expected to supply at low cost. In this liquid crystal projector, a dichroic prism for color synthesis is used, and the performance of this dichroic prism is one factor that determines the performance of the liquid crystal projector.

FIG. 4 is a view showing a dichroic prism for color synthesis disclosed in Japanese Patent Application Laid-Open No. 7-294845. In FIG. 4, reference numerals 21, 22, 23, and 24 denote first to fourth prisms each comprising a right-angle prism. 4 prisms. The width of the first and third prisms is the second width.
And the width of the fourth prism is wider than that of the fourth prism, and the end of the fourth prism is protruded.

In order to manufacture such a dichroic prism, first, a first prism 21 and a second prism 22
When the rectangular surfaces 21b and 22b are placed in contact with the flat jig, an adhesive is applied to the joint surface between the rectangular surfaces 21a and 22a, and similarly, the third prism 23 and the fourth When joining with the prism 24, the rectangular surface 23b
And 24b are brought into contact with the surface of the flat jig to form a rectangular surface 23a.
An adhesive is applied to the joint surface between the two right-angle prisms to form two joints in which two right-angle prisms are joined. After that, using the jig 30 as shown in FIG.
The protruding surface 21c of the first prism 23 and the protruding surface 23c of the third prism 23 are placed in contact with the reference surface 30a of the jig 30, and an adhesive is applied to the bonding surfaces of the respective bonded articles. By doing so, the surfaces of the first prism 21a and the surface 23a of the third prism can be made to be accurate planes, and the prism having the surface 22a of the second prism and the surface 24a of the fourth prism made accurate planes can be used. Obtainable.

That is, as shown in FIG. 6, one of the two faces sandwiching the right angle of the first prism and one face 24a of the two faces sandwiching the right angle of the fourth prism have a blue reflection which reflects blue. A film is formed, and a red reflection film that reflects red is formed on one surface 22a and 23a of the second prism and the fourth prism. The respective surfaces on which the red reflection film is formed can be accurately made the same plane, and the blue reflection film and the red reflection film can be joined in a state of being orthogonal to each other.

Therefore, the beam of the blue image image emitted from the blue liquid crystal panel 26B is uniformly reflected by the blue reflecting surfaces 21a and 24a, and the beam of the red image image emitted from the red liquid crystal panel 26R is also red reflected. Face 22
a, 23a, and are uniformly reflected, and the respective color components are emitted from the second prism 22. Furthermore, a green liquid crystal panel 26G
The green image emitted from the second prism 2 is not reflected by the reflection film provided on any of the bonding surfaces, and
2, a dichroic prism free from color misregistration can be obtained.

[0007]

However, in the above-described dichroic prism, the first prism and the third prism are not provided.
The width of the prism is wider than the width of the other prisms, so that extra materials are required as the prism, it is difficult to reduce the size, and it is necessary to process at least two types of prisms. Since the shapes are different, it is necessary to prepare a jig suitable for each of the vapor deposition jigs and the like required for forming the red or blue reflective film, and there is a problem that the manufacturing cost is increased. The present invention has been made to solve the above problems, and has as its object to provide a low-cost, high-precision dichroic prism.

[0008]

In order to achieve the above object, a dichroic prism according to the present invention and a method of manufacturing the same according to the present invention have substantially the same configuration in which a required reflecting film is formed on a rectangular surface sandwiching a right angle. In a dichroic prism in which four right-angle prisms each having a width are joined around their respective right-angled portions, at least a corner formed by a rectangular surface contacting the first prism of the second prism and a surface orthogonal to the rectangular surface; A corner formed between a rectangular surface of the prism contacting the third prism and a surface orthogonal to the rectangular surface is chamfered. According to a second aspect of the present invention, there is provided a method of manufacturing a dichroic prism comprising four rectangular prisms having substantially the same width and having a required reflection film formed on a rectangular surface sandwiching the rectangular at the right angles thereof. The second prism and the first prism, each of which has a chamfered corner formed by a rectangular surface that abuts and a surface that is orthogonal to the rectangular surface, are rectangular surfaces sandwiching a right angle and are not chamfered. In a state where the rectangular surface is brought into contact with a predetermined plane reference surface, the surface being chamfered and the surface facing it are joined to form a joint having a predetermined groove at the end of the joining surface, The fourth prism and the third prism, which are chamfered at a corner formed by a rectangular surface contacting the three prisms and a surface orthogonal to the rectangular surface, are rectangular surfaces sandwiching a right angle and are chamfered. Not each rectangle In a state in which the surface is brought into contact with a predetermined plane reference surface, the chamfered surface and the surface opposed thereto are joined to form a joint having a predetermined groove at an end of the joint surface, and the joint is formed. Of the grooves, the surfaces where the first prism and the third prism are exposed are brought into contact with a predetermined reference surface to join the joint composed of the first and second prisms and the joint composed of the third and fourth prisms A dichroic prism is obtained by this.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the drawings. FIG. 1 is a perspective view of a dichroic prism according to the present invention. Reference numerals 1, 2, 3 and 4 denote first to fourth right-angle prisms having substantially the same width. Further, as shown in the figure, rectangular surfaces are joined to each other at right angles of the right-angle prisms 1 to 4 to form a dichroic prism.

In the right-angle prism 2, a corner formed by a rectangular surface 2a in contact with the right-angle prism 1 and a surface 2c orthogonal to the right-angle prism 1 is chamfered, and as a result, a surface 2d is formed. The right-angle prism 4 also has a chamfered corner formed by a rectangular surface 4a and a surface 4c perpendicular to the rectangular surface 4a to form a surface 4d. In addition, it is necessary to previously form a blue or red reflective film on the joint surface of each prism by means of vapor deposition or the like. For example, one rectangular surface 1a sandwiching the right angle of the right angle prism 1 or the right angle of the right angle prism 2 The blue reflection film is formed on one of the rectangular surfaces 2a sandwiching the right angle and the rectangular surface 3a sandwiching the right angle of the right angle prism 3 or one of the rectangular surfaces 4a sandwiching the right angle of the right angle prism 4. In this case, when the right-angle prisms are bonded with an adhesive, the blue reflection film is on the same side of the bonding layer, that is, when the blue reflection film is formed on the rectangular surface 1 a of the right-angle prism 1, the rectangular shape of the right-angle prism 3 is used. A blue reflective film is formed on the surface 3a. Alternatively, the reflection film may be formed on the rectangular surfaces 2a, 4a of the right-angle prisms 2, 4, respectively.

Similarly, one of the rectangular surface 1b of the right-angle prism 1 and the rectangular surface 3b of the right-angle prism 3 and one of the rectangular surface 2b of the right-angle prism 2 and the rectangular surface 4b of the right-angle prism 4 reflect red light. When the red reflective film is formed on the same side of the adhesive layer, that is, when the red reflective film is formed on the rectangular surface 1b of the right-angle prism 1, the red reflective film is formed on the rectangular surface 2b of the right-angle prism 2. I do. Alternatively, the reflection film may be formed on the rectangular surfaces 3b and 4b of the right-angle prism 3 and the right-angle prism 4, respectively.

In this embodiment, the right-angle prisms 1 to 4 are processed into the same shape, and then, for example, the right-angle prisms 2 and 4 are shown in FIG. 1B (the right-angle prism 4 is shown as an example).
As shown in (1), surfaces (2d, 4d) are formed by scraping off two corners between one surface of a rectangular surface sandwiching the right angle of the right-angle prism and a surface orthogonal to the surface by means such as lapping. I do. In addition, the width to be shaved off is set to about several mm to several cm. Therefore, in a state where the right-angle prisms 1 to 4 are joined with each right angle as a center, a “レ” -shaped groove is formed diagonally on the end face of the joined object. FIG. 1C shows a side view of the dichroic prism viewed from the point P.
The “R” shaped groove is a surface 3ap which is a part of the surface 3a (1a).
(1ap) and 4d (2d).

The order in which the right-angle prisms 1 to 4 are joined to form a dichroic prism will be described with reference to FIG. In the figure, the red or blue reflective film is emphasized in comparison with its film thickness, while the adhesive is shown ignoring its thickness. First, as shown in FIG. 2A, the rectangular surface 1b of the right-angle prism 1 on which the red reflection film 5a is formed and the rectangular surface 2b of the right-angle prism 2 on which the red reflection film 5a is formed are connected to a plane jig P1. When the rectangular surface 1a of the right-angle prism 1 and the rectangular surface 2a of the right-angle prism 2 on which the blue reflecting film 5b is formed and the corners of which are chamfered are bonded using an adhesive or the like, as shown in FIG. ), The rectangular surface 1b and the rectangular surface 2b are accurate horizontal surfaces. Since the chamfered surface 2d is processed on the right-angle prism 2, a part (1ap) of the rectangular surface 1a and the surface 2d are formed on the front and rear surfaces of the joined body of the right-angle prisms 1 and 2. "-Shaped grooves are formed perpendicular to the rectangular surfaces 1b and 2b.

Next, as shown in FIG. 2 (c), the rectangular surface 3b of the right-angle prism 3 and the rectangular surface 4b of the right-angle prism 4 are brought into contact with the plane jig P1, and the rectangular surface of the right-angle prism 3 is contacted. 3a and the rectangular surface 4a of the right-angle prism 4 having two corners cut off and provided with the blue reflection film 5b are joined with an adhesive or the like. Therefore, the rectangular surface 3b and the rectangular surface 4b accurately become a horizontal plane. Since the surface 4d is machined as described above in the right-angle prism 4, a “レ” -shaped groove formed by a part 3ap of the rectangular surface 3a and the surface 4d is formed between the rectangular surfaces 3b and 4b. It is formed perpendicular to the horizontal plane.

Next, as shown in FIG. 2D, the surface 1ap of the right-angle prism 1 and the surface 3ap of the right-angle prism 3 are connected to a plane P2.
2 and the joint between the right-angle prisms 1 and 2 and the joint between the right-angle prisms 3 and 4 are joined together as shown in FIG.
As shown in (e), a dichroic prism in which the red and blue reflection films 5a and 5b are exactly on the same plane and are orthogonal to each other can be obtained.

More specifically, as shown in FIG. 3, a bonded object A composed of right-angle prisms 1 and 2 and a bonded object B composed of right-angle prisms 3 and 4 are combined with each other. Of the rectangular surface 1a of each of the “Le” -shaped grooves is inserted so that the groove of the “B” and the groove having a “Re” -shaped cross section of the joint B are loosely fitted into the plane portion P2 of the jig T, respectively. A jig T is formed by an elongate surface 1ap partially formed and an elongate surface 3ap similarly formed by a part of the rectangular surface 3a of the "R" -shaped groove.
Is placed so as to abut the elongated flat portions P2, P2 provided on both sides of. In this state, the opposing planes of the two joints A and B, that is, the plane composed of the planes 1b and 2b, and the plane composed of the planes 3b and 4b are joined with an adhesive to form the plane 1a. The plane 3a can form an accurate horizontal plane. At the same time, surfaces 1b (3b) and 2
b (4b) and the planes 1a (2a) and 3a (4a)
And can be configured to be orthogonal to each other. It should be noted that the P2 and P2 surfaces of the jig T shown in FIG. 4 are naturally configured to keep a horizontal plane.

As described above, according to the dichroic prism of the present invention, each of the surfaces on which the red reflection film and the blue reflection film are formed becomes completely flat, and the two surfaces on which the red and blue reflection films are formed are formed. The planes can be made orthogonal at right angles. In the above description, an example has been described in which the corner between the right-angle prisms 2 and 4 is cut off and chamfering is performed.
It goes without saying that the right-angle prisms 1 and 3 may be chamfered. In addition, since the orthogonal accuracy of the joining surface is determined by the planes 1ap and 3ap of the right-angle prism, the cut-off width or angle of the prism has no relation to the orthogonality of the joining surface. Furthermore, in the above description, the right angle prism 2
Although the description has been made using the case where the blue and red reflecting films are provided on the surface, considering that the thickness of each reflecting film and the thickness of the adhesive are small, two surfaces sandwiching the right angle of the four prisms Of these, a blue or red reflective film may be formed on one of the rectangular surfaces.

In the above description, two corners of the right-angle prism were machined so as to be cut off. However, the present invention is not limited to this, and the two rectangular prisms are chamfered and the rectangular surface of the prism without chamfering is formed. Instead of using a flat surface as a reference surface, a groove or the like is formed in two right-angle prisms, and even if joints A and B are joined using the surface of the groove, they are orthogonal.
The two joining surfaces can be accurately matched.

[0019]

According to the present invention, as described above, in manufacturing a right-angle prism constituting a dichroic prism, only prisms having the same shape are manufactured.
Then, the red or blue reflective film formed on the surface of the right-angle prism is made to be orthogonal to the right-angle prism by just chamfering two of the four prisms, and a mask for forming the reflective film on the right-angle prism is commonly used. Therefore, there is an effect that the material cost of the right-angle prism can be reduced, and the manufacturing cost for forming the dichroic prism can be reduced.

[Brief description of the drawings]

1A is a view showing an embodiment of a dichroic prism according to the present invention, FIG. 1B is a right-angle prism with two corners cut off, and FIG. 1C is an oblique side view of FIG. FIG.

FIG. 2A shows a jig and two right-angle prisms,
(B) is a diagram in which two right angle prisms are joined, (c) is a diagram showing a jig and two right angle prisms, (d) is a diagram in which a jig plane is joined to two joined objects, and (e) a dichroic prism FIG.

FIG. 3 is a diagram illustrating a procedure for joining two joints using a jig.

FIG. 4 is a diagram showing a conventional color combining dichroic prism.

FIG. 5 is a diagram showing a state in which a conventional color combining dichroic prism is joined using a jig.

FIG. 6 is a diagram showing a conventional color combining dichroic prism.

[Explanation of symbols]

1 1st right angle prism 2 2nd right angle prism 3 3rd right angle prism 4 4th right angle prism 1a, 1b, 2a, 2b, 2c, 3a, 3b, 4a, 4
b, 4c: prism rectangular surface, 2d, 4d: chamfered surface, 1ap, 3ap: slender plane, P1, P2: jig plane, A, B: joining Thing, T ... Jig.

Claims (2)

[Claims] 1. A dichroic prism in which four right angle prisms having substantially the same width and having a required reflection film formed on a rectangular surface sandwiching a right angle are joined around their respective right angles, wherein at least the first prism of the second prism and The chamfering is performed on a corner formed by the contacting rectangular surface and the surface orthogonal to the rectangular surface and a corner formed by the rectangular surface contacting the third prism of the fourth prism and the surface orthogonal to the rectangular surface. A characteristic dichroic prism. 2. A method for manufacturing a dichroic prism in which four right-angle prisms having substantially the same width and having a required reflection film formed on a rectangular surface sandwiching a right angle are joined around their respective right-angle portions. A second prism having a chamfered corner formed by a rectangular surface and a surface orthogonal to the rectangular surface;
With the prism, a rectangular surface sandwiching a right angle and each of the rectangular surfaces that are not chamfered are brought into contact with a predetermined plane reference surface, and the chamfered surface and the surface facing it are A fourth prism having a chamfered corner formed by a rectangular surface contacting the third prism and a surface orthogonal to the rectangular surface to form a bonded article having a predetermined groove at an end of the bonding surface; Third
With the prism, a rectangular surface sandwiching a right angle and each of the rectangular surfaces that are not chamfered are brought into contact with a predetermined plane reference surface, and the chamfered surface and the surface facing it are Bonding to form a bonded article having a predetermined groove at an end of the bonding surface; and, among the grooves of the bonded article, a surface where the first prism and the third prism are exposed is brought into contact with a predetermined reference surface to form a bonded object. 1st and 2nd
A method for manufacturing a dichroic prism, comprising joining a bonded article made of a prism and a bonded article made of a third and a fourth prism to obtain a dichroic prism.