JPH02135301A - Color separation optical system - Google Patents

Abstract

PURPOSE:To constitute an inexpensive, compact color separation optical system by joining color glass which is coated with a reflection preventive film with the projection surface of a prism for blue separation, and coating the projection surfaces of a prism for red separation and a prism for green separation direction with dichroic films. CONSTITUTION:The color glass 13 which is coated with the reflection preventive film 14 is used as a trimming filter for the projection surface 1C of the prism 1 for blue separation which easily generates reflected light, and the projection surfaces 2C and 3C of the prism 2 for red separation and prism 3 for green separation which hardly generate reflected light are coated directly with the dichroic films 15 and 16 without joining any trimming filter. Consequently, the color separation optical system which guide light beams in wavelength ranges of three colors to three solid image pickup elements 8, 10, and 12 can be formed at low cost and the shape of the 2nd prism 2 can be made small, so the 1st prism and 3rd prism 3 are also made small and compact.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a color separation device that is disposed between an objective lens and a solid-state image sensor of a color television camera, and is used to color-separate a luminous flux from an object. It is related to optical systems.

[Conventional technology]

-S, in a color television camera, the incident light flux from the subject is focused by an objective lens, and a color separation optical system consisting of three prisms arranged in front of the focal plane is used to produce red (R). , green (G), and blue (B), each wavelength range light is imaged on each solid-state image sensor, photoelectrically converted by each solid-state image sensor, and then processed. It forms an image signal.

Here, as a color separation optical system used to obtain light in three color wavelength ranges, for example, as shown in FIG. 2, three prisms l', 2', and 3' are used in combination.

First, a prism 1' separates blue light, a second prism 2' separates red light, and a third prism 3' separates green light. In addition, on the output surface of each prism, the separated three color wavelength range lights also contain other wavelength range light, so in order to prevent this transmitted light, a blue trimming filter 7' and a red trimming filter are used. 9
', a green trimming filter 11' is joined.

[Problem to be solved by the invention]

However, the blue trimming filter 7', red trimming filter 9', and green trimming filter 11' bonded to the end face of each prism are made by laminating dichroic films having wavelength selectivity corresponding to each colored glass. However, it is necessary to bond a glass plate laminated with a dichroic film to a prism, which is complicated and expensive, and it is not compact.

In view of the current situation, it is an object of the present invention to provide an inexpensive and compact color separation optical system for supplying light in three color wavelength ranges to three solid-state image elements.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a three-color separation optical system consisting of three prisms, in which a colored glass coated with an anti-reflection film is bonded to the exit surface of the blue separation prism, and a color glass coated with an anti-reflection film is bonded to the exit surface of the blue separation prism. This color separation optical system is characterized in that the exit surfaces of the prism and the green separation prism are each directly coated with a dichroic film.

[Function] In the present invention, colored glass coated with an anti-reflection film is used as a trimming filter on the exit surface of the prism for blue separation, where reflected light is likely to occur, and the prism for red separation and green separation, where reflected light is less likely to occur, is used as a trimming filter. The exit surface of each prism is directly coated with a dichroic film without bonding a trimming filter, so a color separation optical system is installed to supply three color wavelength range lights to three solid-state image sensors. It becomes possible to manufacture it at low cost and compactly.

(Examples) Hereinafter, the present invention will be explained in detail according to illustrated examples.

In FIG. 1, A is a color separation optical system, and the color separation optical system A is composed of a first prism l, a second prism 2, and a third prism 3.

First, in the first prism 1, the incident light beam from the objective lens 4 is made to enter through the incident surface 1a arranged perpendicularly to the tip axis of the first prism 1, and the reflective surface 1b forms an inclined surface with the optical axis of the incident light beam.
The dichroic layer 5 for reflecting light in the blue region formed on the dichroic layer 5 reflects the light in the blue region and transmits light in other wavelength regions. 2a, the red light is reflected by the red light reflecting dichroic layer 6 formed on the reflective surface 2b, and the green light is transmitted. Input and exit surface 3
By emitting light from b, the luminous flux from the subject is separated into three colors.

As described above, the blue light reflected by the dichroic layer 5 for reflecting blue light of the first prism 1 is totally reflected at the incident surface 1a of the first prism 1, and is reflected by the first prism l.
The light enters the solid-state image sensor 8 through the blue-band light trimming filter 7 bonded to the blue-band light exit surface 1c. The blue light trimming filter 7 is colored glass that absorbs green light and red light. In this blue region light trimming filter 7, an antireflection film 14 is coated on a colored glass 13 for transmitting blue region light, and a dichroic ink layer for blue region light trimming is not laminated on this portion.

This is because if a dichroic layer for trimming blue light is laminated thereon, part of the blue light will be reflected, and this will be mixed with other light to easily cause ghosts. The colored glass for transmitting blue light that is coated with an antireflection film minimizes the reflected light, and also removes the blue light present in the blue light reflected by the dichroic layer 5 for reflecting blue light. Light can be removed.

Between the first prism l and the second prism 2, there are 10 to 30
An air layer with a uniform thickness of μm is formed, so that the transmitted light is not obstructed in any way from the first prism 1 to the second prism 2, and is reflected by the dichroic ink layer 6 of the second prism 2. This means that the red-range light can be reliably totally reflected by the incident surface 2a of the second prism.

The red light that passes through the blue light reflecting dichroic layer 5 of the first prism 1 and is reflected by the red light reflecting dichroic layer 6 of the second prism 2 is completely absorbed by the incident surface 2a of the second prism 2. The red light trimming filter 9 is reflected and coated on the red light bleeding 2c of the second prism 2.
The light then enters the solid-state image sensor IO. Second
The red light trimming filter 9 provided on the red light exit surface 2C of the prism 2 is formed by laminating a dichroic film 15 for transmitting red light directly on the red light exit surface 2C. Since this dichroic film 15 does not reflect red light and reflects light in other regions well, some of the red light reflected by the red light reflecting dichroic ink layer 6 of the second prism 2 is The light outside the red range can be sufficiently removed without using a glass filter.
A trimming effect can be produced. Note that since there is no need to bond a glass filter to the exit surface 2C of the second prism 2, the second prism 2 can be made smaller by the thickness of the glass filter in the optical axis direction.

This dichroic film 15 is similar to those conventionally used in that two or more types of nonmetallic films with a high refractive index and nonmetallic films with a low refractive index are laminated alternately, but the thickness of the conventional dichroic film 15 is It is different from those conventionally used in that it does not reflect red region light and reflects other region lights B and G well by making it approximately twice as large as .

In this way, the green light that has passed through the blue light reflecting dichroic layer 5 of the first prism 1 and the red light reflecting dichroic ink layer 6 of the second prism 2 is transmitted to the third prism 3.
The light enters the solid-state image sensor 12 through the green trimming filter 11 coated on the green light exit surface 3b. The green light trimming filter 11 provided on the green light exit surface 3b of the third prism 3
A dichroic film 16 for reflecting light in the green region is directly laminated on b.

Furthermore, this dichroic film 16 is similar to those conventionally used in that two or more types of nonmetallic films with a high refractive index and nonmetallic films with a low refractive index are laminated alternately.
It is different from those used conventionally in that it does not reflect green light and reflects other light B and R well by making the film about twice as thick as the conventional one.

(Effects of the Invention) As is clear from the following description, according to the present invention, the exit surfaces of the red separation prism and the green separation prism are directly coated with dichroic films without bonding trimming filters. However, as shown in Figures 3 and 4, although it exhibits almost the same spectral characteristics as conventional expensive color separation optical systems, it can be manufactured at low cost, and the second prism Since the shape of the prism 2 can be made small, the first prism 1 and the third prism 3 can also be made small, so that excellent effects such as making it possible to manufacture a compact color separation optical system can be achieved. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a side view of a color separation optical system according to the present invention, FIG. 2 is a side view of a conventional color separation optical system, FIG. 3 is a spectral characteristic diagram of the color separation optical system of the present invention, and FIG. 4 is a side view of a color separation optical system according to the present invention. It is a spectral characteristic diagram of a conventional color separation optical system. 1: First prism 2: Second prism 3: Third prism 4: Objective lens 5: Dichroic layer for reflecting blue light 6: Dichroic layer for reflecting red light 7: Blue light trimming filter 8.10, 12: Solid-state image sensor 9: Red region light trimming filter 11: Green region light trimming filter 13: Colored glass for transmitting blue region light 14: Antireflection film 15: Dichroic film for transmitting red region light 16: Dichroic film for reflecting green region light Patent Applicant: Fuji Photo Co., Ltd., NFcX!

Claims (1)

[Claims] In a three-color separation optical system consisting of three prisms, colored glass coated with an antireflection film is bonded to the exit surface of the blue separation prism, and the exit surfaces of the red separation prism and the green separation prism are bonded to each other. A color separation optical system characterized by being directly coated with a dichroic film.