JPH02248918A - 3-color color separation optical unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a three-color separation optical unit for a color camera using three solid-state image sensors, and in particular to a prism configuration that improves white tracking characteristics without reducing the dynamic range. This invention relates to a three-color color separation optical unit.

Compared to the conventional three-tube color camera that uses three image pickup tubes,
BACKGROUND ART The development and practical use of A-plate color cameras that use three solid-state image sensors, which have excellent characteristics such as mobility, quick response, and imaging characteristics, are gaining momentum.

The three white separation prisms used in this three-panel color camera are:
A three-white separation prism called the Phillips type, which is disclosed in Japanese Patent Publication No. 38-23724, which is the same as the A-tube system, is used. like this.

In a color camera using a three-white separation prism, an optical system is desired that has good color reproducibility from a low amount of light to a high amount of light.

Problems to be Solved by the Invention However, as shown in Figure 2, the photoelectric conversion characteristics of currently used solid-state image sensors are such that the output signal is mostly strong in the low-light region, and the amount of incident light is gradually reduced. As the value is increased, the output signal also increases linearly, but becomes saturated in the high illuminance region. The horizontal axis is the surface illuminance of the photosensitive part (unit: lx), and the vertical axis is C.
This is the output current of the CD (unit: nm). Although efforts are being made to widen the dynamic range, it cannot be said to be sufficient yet.

In a color camera using a solid-state image sensor having such photoelectric conversion characteristics, when white balance is taken at low illuminance (1adb) and grayscale is photographed, there is a problem in that white tracking characteristics are not ensured.

One possible solution to this problem is to irradiate additional light to each of the blue, green, and red channels, but since the amount of imaging light for green and red is larger than for blue, the output signal of the solid-state image sensor may become saturated. There is a problem in that this results in a decrease in the dynamic range.

In view of the above, an object of the present invention is to provide a three-color color separation optical unit for a three-panel color camera that can improve white tracking characteristics without reducing the dynamic range and is compact without requiring wasted space. .

Means for Solving the Problems In order to solve the above problems, the present invention provides a first prism that is provided with a dichroic film that reflects a tf color light component and takes out a blue light component, and a first prism disposed after the first prism. A second prism is provided with a dichroic film that mainly reflects light of the red light component, and is used to take out the red light component; a third prism;
A three-color color separation optical unit having trimming filters for blue, green, and red channels on each output surface, and a solid-state image pickup device provided after the trimming filter, wherein a part of an end face of the blue channel trimming filter is provided. niV
A white light source section is provided in this V-shaped cut section, and a part of the luminous flux from this light source section is made to enter the first prism. The reflected light is reflected by one side of the V-groove for ghost prevention, passes through the trimming filter again, and irradiates the light receiving surface of the solid-state image sensor for the blue channel with additional light different from the imaging light. The configuration is such that a part of the light flux from the image pickup section is transmitted through a trimming filter, and additional light different from the imaging light is irradiated onto the light receiving section of the solid-state image sensor for the blue channel.

According to the present invention, with the above-described configuration, it is possible to apply bias light consisting of a blue light component different from the imaging light to the light-receiving surface of the solid-state image sensor for the back channel, which has a smaller amount of light than green and red light. Furthermore, it is possible to linearly output weak imaging light, improve white tracking performance without reducing the dynamic range, and enable a compact, low-cost three-color separation optical unit configuration.

EXAMPLE Hereinafter, a three-color color separation optical unit used in a three-panel color camera, which is an example of the present invention, will be explained in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing the configuration of an embodiment of the present invention. In the figure, 1 is a camera lens, 2 is a three-color combining/separating optical prism, 3 is a light source, and 4, 5, and 6 are solid-state image sensors.

The three-color separation optical unit 2 includes a first prism 8 that takes out the blue light component and has a blue reflective dichroic film 7 that mainly reflects the blue light component, and a first prism 8 that is arranged after the first prism 8 and mainly reflects the red light component. a second prism 10 for extracting a red light component having a red reflective dichroic film 9;
The third prism 1 is bonded to the surface of the second prism 10 on which the red reflective dichroic film 9 is provided and extracts the green light component.
1, and a blue channel trimming filter 12, a green channel trimming filter 13, and a red channel trimming filter 14 provided on the light exit surface of each prism. In addition, the first prism 8
A microscopic air layer is provided between the second prism 10 and the second prism 10 by a spacer 16 in order to efficiently totally reflect the red light component.

In FIG. 1, the blue light component of the imaging light incident on the first prism 7 from the camera lens 1 is reflected by the blue reflecting dichroic film 7.
After being reflected, it is totally reflected on the first prism surface 16, passes through the blue channel trimming filter 12, and then reaches the solid-state image sensor 4 for the back. Of the light that has passed through the blue reflective dichroic film 7, mainly only the red light component is reflected by the red reflective dichroic film 9, then totally reflected by the second prism surface 17, and then passed through the red channel trimming filter 14. This leads to the solid-state image sensor 6 for red color. The light that has passed through the red reflective dichroic film 9 becomes a green light component and reaches the green solid-state image sensor 6 via the green channel trimming filter 13.

Each trimming filter ultimately regulates the wavelength range of colored light incident on each solid-state image sensor. Such trimming filters generally use both an absorption type (colored glass) and an interference film type (dielectric optical film).

The light source section 3 is a part 1 of the end face of the blue trimming filter 12.
8 is reflected by one surface 20 of the V-groove 19 for ghost prevention, and the light is mirror-finished so as to be perpendicular to the optical axis toward the center 21 of the light-receiving surface of the solid-state image sensor 4. is installed and fixed. The blue trimming filter 12 includes an absorption bitumen trimming filter 23 having the spectral transmittance characteristics shown in FIG. 3, and an interference film type (dielectric optical film) trimming film having the spectral transmittance characteristics shown in FIG. 4. The member 24 is also used. One surface 20 of the V-groove 19 for preventing ghosts is made to have a mirror surface to some extent, and is painted white 26 and then painted 26 black. If one surface 2o of the V-groove 19 for ghost prevention is not painted, metal film deposited, etc., the angle of incidence of the light beam on the surface 2o is small and the total reflection condition is not satisfied, and all light except for diffuse reflection is transmitted and exits the prism. However, white painting is low cost and easy to work with.

The blue light component of the luminous fluxes 30 to 31 from the light source section 3 passes through the absorption type trimming filter 23, is reflected by one surface 20 of the V-groove for ghost prevention, and is again transmitted to the absorption bituminous trimming filter 23 and interference. The light passes through the mold trimming filter 24 and illuminates the light receiving surface of the solid-state image sensor. Although some of the light beams 3o to 31 include green light components, they are reflected and absorbed by the absorption bituminous trimming filter 23 and the interference trimming filter 24.

Among the luminous fluxes 32 to 33 of the luminous flux from the light source section 3 that are not blocked by the black coating 26, the blue light component is reflected by the opposite dichroic film 7 and exits from the prism. In addition, although some green light components are included, the light beams 34 to 33 are subject to the total reflection condition 37.6 with respect to the back-to-back dichroic film 7.
Since the incident angle is above, the light beams 32 to 36 are reflected and emitted out of the prism, and pass through the opposite dichroic film 7 and head towards the red reflective dichroic film 94C, but the total reflection condition 66.1 is
Since the incident angle is greater than 100 degrees, the light is reflected and is not irradiated onto the light-receiving surface of the solid-state image sensor 6 for the green channel. Further, since the green light component is reflected and absorbed by the red trimming filter 14, it is not irradiated onto the light receiving surface of the solid-state image sensor 6 for the red channel.

The light beams 31 to 36 are repeatedly reflected and absorbed by the end face of the trimming filter 12, and are absorbed and attenuated by the trimming filter.

Next, a 3-white separation unit used in a 3-panel color camera, which is a second embodiment of the present invention, will be explained in detail with reference to the drawings, focusing on the light source section that is different from the first embodiment. .

FIG. 6 is a schematic sectional view showing the configuration of this embodiment.

The light source section 6o has a V-shaped notch 63 in a part of the end surface of the blue trimming filter 61, and one surface 64 is reflected by one surface 20 of the V-groove 19 for ghost prevention, and the light is received by the solid-state image sensor 4. The surface is mirror-finished so as to be perpendicular to the optical axis toward the center 21 of the surface, and the other surface 66 is formed to be perpendicular to the optical axis toward the center 21 of the light-receiving surface of the solid-state image sensor 4. . The V-shaped notch 5S31C is provided with a white light source 6o, and a part of the light beam incident on the surface 54 from the light source 60 is a blue light component of the light beam from the light source section 3, as in the first embodiment. is transmitted through the absorption type trimming filter 23 and reflected on one surface 2o of the V-groove for ghost prevention,
The light passes through the absorption type trimming filter 23 and the interference type trimming filter 24 again, and illuminates the light receiving surface of the solid-state image sensor. Further, a part of the light beam incident from the surface 66 is transferred to the absorption bituminous trimming filter 23 and the interference type trimming filter 2.
4 and irradiates the light receiving part of the solid-state image sensor. Of course, the 15th J! As in the example, only the blue light component of the light source can be irradiated onto the light receiving surface of the solid-state image sensor for the back channel, and the red,
The light receiving surface of the solid-state image sensor for the green channel is not illuminated.

In this way, even if a white light source with an emission spectrum in a wide wavelength range is used, a special filter is not required by using the end face of the blue trimming filter 61 and one side 2° of the V-groove for ghost prevention. You can easily irradiate the blue channel with bias light without having to change the conventional configuration.

In addition, it is necessary to prevent irradiation of the solid-state image sensors for the green channel and red channel because the dynamic range decreases; The structure is such that it cannot reach the light-receiving surface of the camera.

Of course, even if there is a certain degree of distribution in the amount of light irradiated within the light receiving surface of the solid-state image sensor, normal cameras are equipped with a shedding correction circuit).

Correction is easily possible. According to the second embodiment, the amount of light irradiated onto the light receiving section of the solid-state image sensor is made uniform, and furthermore, shedding correction becomes easier.

Further, the same effect can be obtained if the light source is a back-to-back light emitting diode having an emission spectrum with a wavelength of 400 to 500 mm, which can be easily obtained at low cost.

Effects of the Invention As described above, according to the present invention, it is possible to apply bias light only to the solid-state image sensor for the blue channel with a simple configuration, and the white tracking characteristics are significantly improved without reducing the dynamic range. To provide an inexpensive three-color separation prism without changing the conventional configuration of the color separation prism.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing a three-color separation optical unit according to the first embodiment of the present invention, Figure 2 is a COD photoelectric conversion characteristic diagram, and Figure 3 is a diagram showing COD photoelectric conversion characteristics.
The figure is a spectral transmission characteristic diagram of an actual channel absorption type trimming filter, FIG. 4 is a spectral transmission characteristic diagram of a back channel interference type trimming filter, and FIG. 6 is a schematic diagram showing a second embodiment of the light source section of the present invention. . 1...Camera lens, 2...3 White separation prism, 3...Light source section, 4,5.6...
... solid-state image sensor, 7 ... blue reflective dichroic film, 9 ... red reflective dichroic film, 8.
...1st prism, 1o...2nd prism, 11...3rd prism, 12...middle channel trimming filter, 1G...ghost countermeasure V-groove, 26...Painted white. Agent's name: Patent attorney Shigetaka Awano and 1 other person. ) Fuu *i Delicate Ladle Hit 1 F-Red 1 Yu〒Q'Ikuro 4 Muff Membrane + 1-One Oko Prism +2--・Betsu Chinkildrimisogefu 4 Ruda tq-f-
utr@tMV;1ll-511 length (ny'nn

Claims (4)

[Claims] (1) A first prism that is equipped with a dichroic film that reflects a blue light component and takes out the blue light component, and a dichroic film that is placed after the first prism and that mainly reflects a red light component that emits red light. a second prism for extracting the light component; a third prism bonded to the surface of the second prism on which the dichroic film is provided and for extracting the green light component; and a third prism for extracting the green light component on each exit surface for blue, green and red channels trimming filters, and a solid-state image sensor is provided after each of the trimming filters, the three-color color separation optical unit having a white light source section provided on a part of the end face of the trimming filter for the blue channel, making the light beam from the light source enter the first prism,
The reflected light is reflected by one surface of the anti-ghost V-groove provided in the first prism, and is transmitted through the blue channel trimming filter again to reach the light-receiving surface of the solid-state image pickup device for the blue channel. A three-color color separation optical unit characterized by irradiating additional light different from imaging light. (2) A first prism that includes a dichroic film that reflects blue light components and extracts the blue light component; and a dichroic film that is placed after the first prism and primarily reflects red light components. a second prism for extracting a red light component; a third prism bonded to the surface of the second prism on which the dichroic film is provided and for extracting a green light component; and a blue light component on each output surface.
A three-color color separation optical unit comprising trimming filters for green and red channels, and a solid-state image sensor is provided after each of the trimming filters, the trimming filter for the blue channel having a V-shaped part on a part of the end surface. A cutout is provided in the V-shaped cutout, a white light source is provided in the V-shaped cutout, a part of the luminous flux from the light source is made to enter the first prism, and the light source is provided in the first prism. The reflected light is transmitted through the trimming filter again, and the light receiving surface of the solid-state image sensor for the blue channel is irradiated with additional light different from the imaging light. , wherein a part of the light flux from the light source section is transmitted through a trimming filter to irradiate the light receiving section of the solid-state image sensor for the blue channel with additional light different from the imaging light. Resolving optical unit. (3) The three-color color separation optical unit according to claim 1, wherein one surface of the V-groove for preventing ghosts is coated with white paint. (4) The three-color color separation optical unit according to claim 2, wherein one surface of the V-groove for ghost prevention is coated with white paint.