JP2785492B2 - Color separation prism and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color separation prism used in an optical system of an optical apparatus and a method of manufacturing the same.

[0002]

2. Description of the Related Art A color separation prism for separating image light into a plurality of color component lights, which has been generally used as a three-plate type color image pickup apparatus, will be described with reference to FIGS.

As shown in FIG. 1, a conventional color separation prism includes three prism members 13a, 13b, and 13c.
Usually, optical glass (BK7, F5, etc.) is used as the material, and is optically polished to the shape shown in the figure.

In order to decompose the imaging light 4 into green, blue and red color component lights, the prism 13a is vacuum-deposited for each of the prism members 13a and 13b, and the prism 13a has an antireflection film 3a and a green reflection film for reflecting the green component. 3b are formed, and the prism member 13
On b, a blue reflection film 3c for reflecting blue component light is formed.

[0005] Then, each prism member 13a, 13b,
13c, the green, blue, and red solid-state image pickup devices 5a, 5a, and 5c are positioned at the focal position of an image pickup lens (not shown) at each component light emission unit.
b and 5c are arranged.

In order to dispose them at the focal position, the color separation prism is assembled such that the green, blue, and red color optical path lengths (nd) from the incident portion of the imaging light 4 to each solid-state imaging device are the same.

Each of the prism members 13a, 13b, 13
c is optically polished by itself, but each has a processing error. Therefore, when the prisms are assembled, they are adjusted by using an assembling jig or the like by using an adhesive portion of the three prisms, so that green, blue, and red are adjusted. The optical path length of each color is the same.

The prism members 13a, 13b, 13c are fixedly integrated with the adhesives 14a, 14b. In addition, the solid-state imaging devices 5a, 5b, and 5c aligned with the optical axis of each component light on the flat portion of the emission part of each color component light.
5c is fixed by an adhesive.

[0009]

In the above-described conventional color separation prism, each prism member is manufactured by grinding and optical polishing from an optical glass material, but the shape is not a parallel plane but a plane which intersects at different angles. It is difficult to process and requires a long working time, and errors are likely to occur.

Since it is necessary to use three prism members and make the optical path length of each component light the same, it is necessary to assemble each prism member with a higher precision (error 30 μm or less) using an assembling jig or the like. The assembly time is also long.

In addition, since the price of the prism member alone is high, a loss due to a defect in forming an optical film such as an antireflection film and a reflection film is large. Due to the problems of workability and mass productivity as described above, the overall manufacturing cost increases.

Apart from that, since the prism material is an optical glass, it is heavy and easily damaged, so that care must be taken in handling. In addition, a special adhesive is required to fix each prism member, and the relative position of each prism member is likely to be displaced due to environmental conditions, resulting in poor stability and lack of reliability.

Further, on the processing surface, the optical polishing surface of the prism member is mainly a flat surface, and it is difficult to form the optical polishing surface in the concave portion.

The present invention solves the above-mentioned problems, and can reduce the assembly cost without the necessity of assembling with an assembling jig. Since the grinding and polishing of a single prism is not required, the processing cost can be reduced, and various shapes can be obtained. It is an object of the present invention to provide a color separation prism which is easy to process, is lightweight, and is not easily damaged, and a method for manufacturing the same.

[0015]

In order to achieve the above object, the present invention uses a glass plate and a transparent resin having the same or similar refractive index as a color separation prism for separating imaging light into a plurality of color component lights. An optical interference film is formed on a glass plate, and a transparent resin forms a shape as a base material of the color separation prism and fixes the glass plate.

Specifically, a glass plate on which an optical interference film is formed is disposed at a predetermined position in a mold for forming an outer shape of a color separation prism at a position where image pickup light is separated, and then a molten transparent resin is formed. It is poured into a mold, cooled and solidified to form a shape, and a glass plate is fixed to form a color separation prism.

[0017]

According to the present invention, since the transparent resin is used as the base material of the color separation prism according to the above-described structure, the injection molding can be performed at a time using a molding die having the shape of the color separation prism. The glass plate on which is formed is disposed in a molding die at a predetermined position of the reflection part of the imaging light.

As for the thermal properties, since the heat resistance temperature of the glass plate and the optical interference film is higher than the melting temperature of the transparent resin of about 250 ° C., damage due to heat hardly occurs. The mold temperature at the time of injection molding can be set at around 100 ° C. where the transparent resin easily flows.

By injecting the molten transparent resin into the mold, the glass plate is wrapped in the transparent resin, and by cooling the mold, the transparent resin is solidified to form the color separation prism shape and the optical interference film. Is fixed at a predetermined position.

Since the refractive indices of the glass plate and the transparent resin are substantially equal, no light beam is bent at the interface between the glass plate and the transparent resin.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. 1 and 2 are a front sectional view and a plan view, respectively, of a color separation prism used in a three-plate type color image pickup device, and are formed from a transparent resin 1 and glass plates 2a, 2b, 2c as shown in the drawings. The glass plates 2a, 2b, and 2c on which the antireflection film 3a, the green reflection film 3b, and the blue reflection film 3c are formed are arranged at positions where the imaging light 4 reflects the three colors of green, blue, and red, respectively. It is wrapped and held and fixed by injection molding or the like with a transparent resin 1 forming the base of the decomposition prism.

The imaging light 4 passes through the anti-reflection film 3a and the glass plate 2
a, only green is reflected by the green reflection film 3b and the glass plate 2b, and is totally reflected by the glass plate 2a to be incident on the solid-state imaging device 5a.

Next, the remaining imaging light is transmitted through the green reflection film 3b and the glass plate 2b, is reflected by the blue reflection film 3c and the glass plate 2c, and is incident on the solid-state imaging device 5b. Then, the remaining red light enters the solid-state imaging device 5c.

Each of the solid-state imaging devices 5 from the incident surface of the imaging light 4
Although it is necessary to make the relative optical path lengths a, 5b, and 5c equal, the solid-state imaging devices 5a, 5a,
The optical path lengths b and 5c are determined without the necessity of assembly adjustment.

Transparent resin 1 and glass plates 2a, 2b, 2c
Means that the imaging light 4 has the same refractive index and the transparent resin 1 and the glass plate 2
There is no bending at the interfaces a, 2b and 2c.

The mounting surfaces of the solid-state imaging devices 5a, 5b, and 5c are provided with concave portions 6a, 6b, and 6c each having a simple positioning optical plane.

FIGS. 3 and 4 are a sectional view and a front view, respectively, of a molding die for producing a color separation prism according to an embodiment of the present invention.

Convex portions 7a, 7 for forming a concave surface of the color separation prism
The glass plate 2 is inserted into the glass plate disposing grooves 9a, 9b, 9c arranged at appropriate positions in the lower mold 8 for injection molding having b, 7c.
a, 2b, and 2c are placed, and the upper mold 10 for injection molding is mounted while being aligned with the upper and lower mold setting holes 11;
The molten transparent resin 1 is injected into the lower molds 10 and 8 after being heated to about 100 ° C. at which the transparent resin 1 easily flows.

After the filling, the upper and lower molds 10, 8 are cooled to solidify the transparent resin 1 therein. After solidification, the transparent resin 1 is taken out of the upper and lower molds 10 and 8 so that the transparent resin 1 forms the base of the color separation prism and simultaneously fixes the glass plates 2a, 2b and 2c arranged at appropriate positions.

[0030]

As is apparent from the above embodiments, according to the present invention, the relative position from the entrance of the imaging light to the exit of each of the green, blue and red component lights in the color separation prism is determined by the accuracy of the molding die. Therefore, it is not necessary to assemble each prism member using an expensive assembling jig as in the related art, and the relative position does not vary due to the assembling.

Therefore, the quality is stabilized and the production yield is greatly improved. In addition, since the color separation prism can be formed instantaneously, the number of manufacturing steps is reduced, the productivity is improved, and the cost can be significantly reduced.

Further, since the prism matrix is made of a transparent resin, it is lightweight, hardly damaged, and easy to handle. In addition, since injection molding is used, optical polishing of a surface having an angle as in the related art is unnecessary, and the processing cost can be reduced. Furthermore, since a concave optically polished surface can be formed on the emission surface of the imaging light, simple positioning of the solid-state imaging device is possible.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a color separation prism according to an embodiment of the present invention.

FIG. 2 is a plan view of a color separation prism according to one embodiment of the present invention.

FIG. 3 is a sectional view of an upper mold for injection molding for manufacturing a color separation prism according to one embodiment of the present invention.

FIG. 4 is a front view of an injection mold for manufacturing a color separation prism according to an embodiment of the present invention.

FIG. 5 is a front sectional view of a conventional color separation prism.

FIG. 6 is a plan view of a conventional color separation prism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent resin 2a, 2b, 2c Glass plate 3a Antireflection film (optical interference film) 3b Green reflection film (optical interference film) 3c Blue reflection film (optical interference film) 6a, 6b, 6c Concave parts 9a, 9b, 9c Glass plate Placement groove

Claims (4)

(57) [Claims] 1. A color separation prism for separating imaging light into a plurality of color components, comprising a glass plate and a transparent resin having the same or approximate refractive index, and an optical interference film formed on the glass plate. A color separation prism in which a transparent resin forms a prism shape as a base material and a glass plate is fixed. 2. The color separation prism according to claim 1, wherein a concave portion on an optical plane is provided in an emission portion of the color-separated imaging light. 3. A glass plate on which an optical interference film is formed is disposed at a position for reflecting image pickup light in a mold for forming image separation light into a shape of a color separation prism, and then a molten transparent resin is injected into the mold. And a method for producing a color separation prism that cools and solidifies to form a prism shape and fixes a glass plate. 4. A method for manufacturing a color separation prism according to claim 3, wherein a transparent resin is injected into a mold having a shape for forming a concave portion on an optical plane at an emission portion of the color-separated imaging light.