JPH04367190A - Color solid-state imaging device - Google Patents

Abstract

PURPOSE:To shorten an optical path length of a prism by the length equal to a trimming filter thickness and to obtain a good color separation characteristic by effectively suppressing a crosstalk light using a signal trimming filter plate with a simple configuration a color solid-state image pickup device such as a three-plate color television camera. CONSTITUTION:A three-color separation prism 20 is constituted of prism members 21, 22 and 23, and a dichroic mirror 24 reflecting a green light and a dichroic mirror 25 which permits a red light to go through it but reflects a blue light are provided. A luminous flux 26 is separated in color into a green light 27, a blue light 28 and a red light 29 by the dichroic mirrors 24 and 25. A trimming filter 30 is provided only for the red light 29, and is used as a low-pass type color filter which shuts off a crosstalk light whose wave length is shorter than a specified red color wave length on a short wave length side. Thus, a good color separation characteristic accompanied by a simple constitution are obtained and an optical path length of a prism can be shortened.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a television camera,
The present invention relates to color solid-state imaging devices such as video cameras.

0002

2. Description of the Related Art In recent years, a three-chip color camera (hereinafter referred to as a three-panel camera) using three solid-state image sensors has been developed and is used as a professional camera. FIG. 6 is a sectional view of a color separation optical system of a conventional three-panel camera. In the figure, 1 is the light flux that passed through the imaging lens (more precisely, the optical axis), 1
A and 1B are the ranges of the luminous flux, 2 are prism members 2A and 2
This is a three-color separation prism consisting of B and 2C, and is described, for example, in Japanese Patent Publication No. 38-23724.

The light beam 1 is divided into three primary color light beams 5 by dichroic mirrors 3 and 4 deposited on the three-color separation prism 2.
Trimming filters 8, 9, and 1 are separated into colors (blue), 6 (red), and 7 (green), and are further attached to the output surface.
The wavelength band is corrected by 0, and each solid-state image sensor 11
, 12, and 13.

Reference numeral 14 is an infrared cut filter that cuts off infrared light, and 15 is a crystal filter that cuts off high spatial frequencies. The trimming filters 8, 9, and 10 are made of colored glass that absorbs light in a specific wavelength band, and a reflective filter formed of an optical multilayer film that reflects light in a specific wavelength band.

The solid-state image sensor 11 is hermetically sealed and mounted in a ceramic package 11B having a colorless and transparent protective glass 11A on the front surface, and is attached to the output surface of the prism member 2A via a connecting member 16. Fixed. The same applies to the solid-state image sensors 12 and 13.

Prism members 2B and 2C are closely joined, and prism members 2A and 2B are joined with a spacer 17 interposed therebetween, with an air gap of several tens of microns between them. Reflected light fluxes 5 and 6 at dichroic mirrors 3 and 4
By being reflected again by total reflection, the light beam is emitted as a light beam that forms a front image rather than an inverted image (mirror image). A color television signal is obtained by combining the imaging signals of the solid-state imaging devices 11, 12, and 13.

[0007]

In such a conventional three-chip camera, trimming filters 8, 9, and 10 are required for each color output surface, resulting in a complicated configuration and an expensive product. In addition, in a three-chip camera, the imaging lens requires a long back focus due to the three-color separation prism, but the prism optical path length and back focus become longer due to the thickness of the trimming filters 8, 9, and 10, and the imaging lens make it larger and more expensive. However, if the trimming filters 8, 9, and 10 are removed, the configuration becomes simpler, but if left as is, crosstalk light will occur between each color and the color separation characteristics will deteriorate.

In view of these points, the present invention can effectively suppress crosstalk light with a single trimming filter, achieve good color separation characteristics with a simple configuration, and reduce the amount of light equivalent to the thickness of the trimming filter. It is an object of the present invention to provide a color solid-state imaging device that can also shorten the prism optical path length.

[0009]

[Means for Solving the Problems] The present invention includes first, second, and third prism members and first and second dichroic mirrors from the incident side to separate imaging light into three primary colors. 3
It includes a color separation prism and three solid-state imaging devices each receiving light of three primary colors emitted from the three-color separation prism, and the first dichroic mirror reflects and separates the green light from the imaging light. The blue light is emitted from the first prism member, the blue light is reflected and separated by the second dichroic mirror, the blue light is emitted from the second prism member, and the red light transmitted through the second dichroic mirror is sent to the third prism member. A low-pass type color filter is provided for blocking crosstalk light having a wavelength shorter than a predetermined short-wavelength red wavelength only for the red light.

0010

[Operation] In the present invention, green light and blue light, which are lights with shorter wavelengths than red light, are reflected by a dichroic mirror, and red light is transmitted, thereby separating the colors. As a result, it is possible to specifically generate crosstalk light on the short wavelength side only for red light among the three colors, and a low-pass color filter to block this is provided only for red light, resulting in good color separation. To realize these characteristics with a single trimming filter. Further, the trimming filter can be arranged at the rearmost part of the three-color separation prism, and the front and intermediate prism members are not provided with trimming filters. This also makes it possible to shorten the prism optical path length by the thickness of the conventional trimming filter.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a color solid-state imaging device of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a color separation optical system according to an embodiment of the present invention.
20 is a three-color separation prism, and 21, 22, and 23 are prism members. 24 is a dichroic mirror that reflects light in the green wavelength band, and 25 is a dichroic mirror that transmits red and infrared wavelength bands and reflects blue wavelength band. The prism members 21, 22, and 23 are all closely bonded and have a simple structure without air gaps.

26 is an imaging light flux emitted from an imaging lens and an infrared cut filter (not shown); 26A, 2
6B indicates the range of luminous flux. The light beam 26 is color-separated into a green light beam 27, a blue light beam 28, and a red light beam 29 by dichroic mirrors 24 and 25. Note that the blue light beam 28 is reflected once and then emitted, so the subject image is an inverted image (mirror image).
However, the image is flipped upside down using an electric circuit.

A trimming filter 30 is adhesively fixed to the exit surface of the prism member 23 from which the red light beam 29 exits. Note that the dimensions of the prism members 21, 22, and 23 are determined so that the optical path lengths of the respective light beams 27, 28, and 29 are equal. The prism member 23 is made smaller in advance by the thickness of the trimming filter 30. Solid-state imaging devices 31, 32, and 33 have the same structure as the conventional solid-state imaging device 11 shown in FIG.

FIG. 2 shows the spectral characteristics of the dichroic mirror 24, and the center wavelength position of the half-value (position where the transmittance is half) of the boundary between the short wavelength side and the long wavelength side of the reflection band is point A. This is set between 520 and 540 nm.

FIG. 3 shows the spectral characteristics of the dichroic mirror 25, and the half-value wavelength position of the boundary of the reflection band is point B, which is set at 530 to 550 nm. The spectral characteristics of the dichroic mirrors 24 and 25 vary depending on the configuration of the optical multilayer film, but since they have a predetermined range at oblique incidence as shown in the beams 26A and 26B in FIG. 1, the average characteristics there are Also, as shown in FIGS. 2 and 3, the slope of the reflection zone boundary increases. Therefore, the dichroic mirror 24 that reflects green light is shifted to the short wavelength side, and the dichroic mirror 25 that reflects blue light is shifted to the long wavelength side, and the above characteristics are set.

If they are combined in this manner, three-color separation characteristics without the trimming filter 30 are obtained, and including the characteristics of the infrared cut filter, the characteristics are as shown by the solid line in FIG. 4. As shown in Fig. 4, among the three colors, green light and blue light can be used only with dichroic mirrors 24 and 25 to ensure a good wavelength band with relatively little crosstalk light without using a trimming filter. Only in this case, as shown in the shaded area, crosstalk light can be generated specifically on the short wavelength side. If a low-pass color filter as shown by the dotted line in FIG. 4 is provided for red light in order to block this crosstalk light, good color separation characteristics can be achieved for all three colors.

In this embodiment, as shown in FIG.
It is simplified to one sheet and placed behind the three-color separation prism 20 and immediately before the solid-state image sensor 33. It is desirable that the optical path length of the three-color separation prism 20 can be shortened as much as possible without waste. In that case, as shown in the figure, the entrance surface of the intermediate prism member 22 is fully used for the range of light beams 26A to 26B.

When the dimensions of the three-color separation prism 20 are reduced to the geometrically possible limit, the prism members 21 and 23
Although there is a dimensional margin for replacing with the trimming filter 30 near the exit surface of the prism member 22, there is no margin for replacing with a filter near the exit surface of the intermediate prism member 22 because the light beam 26B passes therethrough. If there is room, the prism dimensions should be able to be further reduced. Therefore, the blue light beam 28 is emitted from this intermediate prism member 22, and no trimming filter is provided here. In this way, the shortest prism optical path length can be achieved, and the red trimming filter 30 is absorbed into the original prism optical path length. Compared to the case where a trimming filter is provided in the intermediate prism member 22, the thickness thereof is reduced.

FIG. 5 is a cross-sectional view of a solid-state image sensor according to another embodiment of the color solid-state image sensor of the present invention, in which numeral 40 denotes a package case made of ceramic or the like;
41 is a CCD chip, 42 is a trimming filter film, which is an organic absorptive color filter film formed on the light-receiving surface of CCD 41, and its characteristics are only for red light, from a predetermined short wavelength side to red wavelength. It is also a low-pass color filter that blocks short-wavelength crosstalk light. 43 is a protective glass, and 44 is a lead terminal.

Instead of the trimming filter film 42, colored glass may be bonded to the CCD chip 41 or the protective glass 43. Further, the protective glass 43 itself may be used as a trimming filter. In this way, by providing the trimming filter in the solid-state image sensor itself, the configuration on the three-color separation prism side can be simplified. The assembly process of a three-color separation prism requires adhesion, which generally has poor manufacturability, but reducing the number of prism bonding points is effective in improving the manufacturability of the color solid-state imaging device as a whole. Further, the form of the three-color separation prism 20 used in the embodiment is not limited to the present invention, and the present invention can also be applied to the three-color separation prism configuration with an air gap shown in the conventional example.

[0021]

Effects of the Invention In the color solid-state imaging device of the present invention, the first dichroic mirror reflects and separates the green light from the imaging light, the second dichroic mirror reflects and separates the blue light, and the second dichroic mirror reflects and separates the blue light. By providing a low-pass color filter that blocks crosstalk light with wavelengths shorter than the predetermined short wavelength side red light transmitted through the red light, crosstalk light can be effectively suppressed with a single trimming filter. Therefore, good color separation characteristics can be achieved with a simple configuration. Furthermore, it is possible to shorten the prism optical path length by an amount equivalent to the thickness of the trimming filter, which is effective in reducing the size and cost of color solid-state imaging devices such as three-panel cameras, and its industrial value is high.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of a first embodiment of a color solid-state imaging device of the present invention.

[Figure 2] Spectral characteristic diagram of the first dichroic mirror in the same example

[Figure 3] Spectral characteristic diagram of the second dichroic mirror in the same example

[Figure 4] Comprehensive spectral characteristic diagram in the same example

FIG. 5 is a cross-sectional view of a solid-state image sensor according to another embodiment of the present invention.

[Fig. 6] Cross-sectional view showing the configuration of a conventional color solid-state imaging device

[Explanation of symbols]

20 3 color separation prism 21, 22, 23 Prism member 24, 25 Dichroic mirror 26 Luminous flux 27 Green luminous flux 28 Blue luminous flux 29 Red luminous flux 31, 32, 33 Solid-state image sensor 30, 42 Trimming filter 43 Protective glass

Claims (3)

[Claims] 1. A three-color separation prism having first, second, and third prism members and first and second dichroic mirrors from the incident side to separate the imaging light into three primary colors; Three solid-state imaging devices each receive light of three primary colors emitted from a color separation prism, the imaging light is separated by reflection of green light by the first dichroic mirror, and the green light is emitted from the first prism member. , the blue light is reflected and separated by the second dichroic mirror and emitted from the second prism member, the red light transmitted through the second dichroic mirror is emitted from the third prism member, and the red light is emitted from the third prism member. A color solid-state imaging device provided with a low-pass color filter that blocks crosstalk light having a wavelength shorter than a predetermined short-wavelength side red wavelength. 2. A three-color separation prism having first, second, and third prism members and first and second dichroic mirrors from the incident side to separate the imaging light into three primary colors; The solid-state imaging device includes three solid-state imaging devices each receiving light of three primary colors emitted from a color separation prism, and a color filter that blocks crosstalk light outside a predetermined wavelength band with respect to the three primary colors of light. A color solid-state imaging device installed in the element. 3. A three-color separation prism having first, second, and third prism members and first and second dichroic mirrors from the incident side to separate the imaging light into three primary colors; Three solid-state imaging devices each receive light of three primary colors emitted from a color separation prism, the imaging light is separated by reflection of green light by the first dichroic mirror, and the green light is emitted from the first prism member. , the blue light is reflected and separated by the second dichroic mirror and emitted from the second prism member; the red light transmitted through the second dichroic mirror is emitted from the third prism member; The center wavelength position of the half-value of the reflection band boundary of the second dichroic mirror is 520 to 540 nm, and the wavelength position of the half-value of the reflection band boundary of the second dichroic mirror is 530 nm.
Color solid-state imaging device set at ~550 nm.