JP2823096B2 - Color separation optics - 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 optical system, and more particularly to a color separation optical system used for a TV camera or the like.

[0002]

2. Description of the Related Art In many cases, a color television camera performs image processing by dividing an image forming light beam into R, G, and B components. A color separation prism is used to separate the image forming light beam into R, G, and B components. Used. Such a color separation prism usually includes a plurality of prisms, that is, first, second, and third prisms from an incident side of an image forming light beam.
Consists of a prism. A dichroic coat that reflects only the BLUE component is applied to the light exit surface of the first prism, and the BLUE component reflected light reflected on the exit surface of the first prism is the difference between the refractive index of air and the prism glass at the entrance surface of the first prism. After being totally reflected by the light source and emitted from the emission surface of the BLUE channel and passed through a blue trimming filter (colored glass) to remove color components other than the BLUE component, CC
An image is formed on D.

The remaining light flux other than the BLUE component passes through the first prism and enters the second prism, and only the RED component is reflected by the exit surface of the second prism to which a dichroic coat that reflects only the RED component is attached. This reflected light is the second due to the difference in the refractive index between the air layer and the prism glass.
After being totally reflected by the entrance surface of the prism, exiting from the exit surface of the RED channel, and passing through a red trimming filter (color glass) to remove color components other than the RED component, the CC
An image is formed on D.

The remaining green component is emitted from the exit surface of the third prism, passes through a green trimming filter (color glass) to remove color components other than the green component, and forms an image on a CCD. . Such a conventional color separation optical system is configured such that a trimming filter such as bonding a color glass to the exit surface of each prism is provided to transmit only light of a necessary wavelength component, and to guide image light to each solid-state imaging device. Have been.

[0005]

However, in the color separation optical system, since the reflectance of the CCD is high, light reflected on the CCD surface is reflected on the surface of the trimming filter and the junction interface between the prism exit surface and the trimming filter. The light is reflected, and the reflected light again enters the CCD, which causes a flare phenomenon. In addition, the provision of a color glass as a trimming filter by bonding is an obstacle to making the color separation optical system compact, and also takes a lot of man-hours for bonding, thus preventing the provision of an inexpensive and compact color separation optical system. It has become. The present invention has been made in view of such circumstances, and has as its object to provide an inexpensive and compact color separation optical system that does not cause a flare phenomenon.

[0006]

According to the present invention, in order to achieve the above object, a solid-state image pickup device is attached to an output end of a color separation prism for separating subject light from a photographing lens into a plurality of wavelength band components. In the color separation optical system, an antireflection film is directly attached to each emission surface of the color separation prism facing the solid-state imaging device.

[0007]

According to the present invention, an antireflection film is attached to the exit surface of the color separation prism. As a result, the reflected light from the CCD surface is transmitted without being reflected on the prism exit surface,
No flare phenomenon occurs. Also, since there is no trimming filter bonded, there is no interface reflection between the colored glass filter and the prism. In addition, the CCD can be made closer to the exit end of the prism by the thickness of the color glass filter, so that the color separation optical system can be made compact.

Incidentally, it is possible to electrically treat color blurring or the like caused by removing the trimming filter.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the color separation optical system according to the present invention will be described below in detail with reference to the accompanying drawings. The first shown in FIG.
In a three-color separation prism composed of a prism 10, a second prism 12, and a third prism 14, the first prism 1
A dichroic coat that reflects only the BLUE component is applied to the light flux exit surface 16 of the zero, and the BLUE component reflected light reflected by the light flux exit surface 16 is reflected on the first prism entrance surface 18 by the difference in refractive index between air and prism glass. Total reflection B
The light is emitted from the emission surface 20 of the LUE channel, and the CCD 22
Image on top.

When the light of the BLUE component is incident on the surface of the CCD 22, a part of the light is reflected and directed toward the emission surface 20. An antireflection film 24 is attached to the light exit surface 20. Therefore CC
The reflected light from D22 returns into the prism, and most of the reflected light does not enter the CCD 22 again. In this way, the flare phenomenon that has conventionally occurred can be prevented.

The remaining light flux other than the BLUE component passes through the first prism 10 and enters the second prism 12, where
Only the RED component is reflected by the exit surface 26 of the second prism to which the dichroic coat that reflects only the D component is attached.
Is totally reflected by the entrance surface 30 of the second prism due to the difference in refractive index from the second prism, exits from the exit surface 32 of the RED channel, and
An image is formed on CD34.

An anti-reflection film 36 is attached to the emission surface 32 in the same manner as the emission surface 18 of the BLUE channel.
4 transmits the reflected light. The last remaining component is GR
The light exits from the exit surface 40 of the third prism 14 as an EEN component and forms an image on the CCD 38. An anti-reflection film 42 is attached to the emission surface 40 of the third prism 14, and the CCD 38
Transmits reflected light from

The antireflection films 24, 36 and 42 are B,
The film is configured to transmit broadband light including R and G color lights, or the antireflection films 24, 36, and 42 are each formed of BL.
It is configured to transmit UE light, RED light, and GREEN light. One specific configuration of this antireflection film is as follows, where the fundamental wavelength is λ, alumina (Al
₂ O ₃ ), zircon (ZrO ₂ ), and fuccamagnesium (MgF ₂ )

[0014]

(Equation 1) Is laminated in three layers. This three-layer antireflection film transmits visible light with a reference wavelength λ of usually 550 nm. This reference wavelength λ may be adjusted to the center wavelength of each of the B, R, and G color lights.

[0015]

As described above, according to the color separation optical system of the present invention, the anti-reflection film is directly attached to each of the emission surfaces of the color separation prism, so that the color separation prism is disposed to face the emission surface of the color separation prism. The reflected light that is reflected on the imaging surface of the solid-state imaging device and then reflected on the exit surface of the opposing color separation prism and re-enters the solid-state imaging device can be reduced as much as possible, thereby preventing the flare phenomenon and the like. According to the color separation optical system of the present invention, there is no color glass or the like, and the reflected light from the CCD returns to the color separation prim emission surface side, passes through the antireflection film, and is reflected again at the color glass bonding surface. There is nothing. Furthermore, in the present invention, without using colored glass, since the antireflection film was directly attached to each emission surface of the color separation prism,
The color separation optical system becomes compact and can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a drawing showing an embodiment of the present invention.

DESCRIPTION OF SYMBOLS 10 ... First prism 12 ... Second prism 14 ... Third prism 16 ... Blue reflection dichroic film 18 ... Antireflection film 20 ... BLUE channel emission surface 22 ... CCD 24 ... Antireflection film 26 ... Red reflection dichroic Film 30: anti-reflection film 32: RED channel emission surface 34: CCD 36: anti-reflection film 38: CCD 40: GREEN channel emission surface 42: anti-reflection film

Claims (1)

(57) [Claims] 1. A color separation optical system in which a solid-state image pickup device is attached to an output end of a color separation prism that separates subject light from a photographing lens into a plurality of wavelength range components. Each output of the color separation prism
A color separation optical system characterized in that an antireflection film is directly attached to the projection surface .