JPS581871B2 - TV camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that can make the best use of the amount of bias light in an optical system that uses a dichroic mirror to separate three different types of light, and furthermore, it relates to a device that can improve the optical characteristics such as polarization of an interference film and improve the optical characteristics of a television camera. A bias illumination device is applied to the optical system to reduce the size of the optical system.

2. Description of the Related Art Conventionally, bias illumination of a television camera is known as a method of removing the afterimage phenomenon of television images by supplementally illuminating the light receiving surface of an image pickup tube at low illuminance with an appropriate light source.

Hereinafter, the optical system for a television camera of a well-known bias illumination device will be mentioned, and its problems will be explained.

Fig. 1 shows an optical system using three different resolving prisms, and Fig. 2 shows a relay lens system in which one relay lens is placed in each image pickup tube.

First, the configuration of the optical system shown in FIG. 1 will be explained.

In the figure, 10 is a photographing lens, 4, 5, and 6 are color separation prisms, and dichroic mirrors are sandwiched between prisms 4 and 5 and between prisms 5 and 6.

Further, 7, 8, and 9 are image pickup tubes.

On the other hand, the incandescent lamp 1, the color temperature correction filter 2, and the shutter rod 3 constitute a bias light illumination device.
The cladding rod 3 is made up of a core material 3a made of a high refractive index material and a covering material 3b made of a low refractive index material, and a portion of the cladding rod 3 is cut parallel to the axis to form a diffusion surface 3c and coated with white paint.

The cladding rod 3 is provided close to the entrance surface of the prism 4.

In this optical system, light emitted from a light source 1 passes through a color temperature correction filter 2 and enters the end face of a cladding rod 3.

The light transmitted through the cladding rod by total internal reflection is reflected by the diffusing surface 3c, passes through three different resolving prisms 4, 5, and 6, and is irradiated toward the light receiving surface of the image pickup tube of each channel.

This irradiated light flux (bias light) must match the set color temperature of the TV camera to achieve white bounce, so the light reaching the image pickup tube (R, G, B) of each channel is R:G:B= Must have a 1:1:1 power ratio.

(Here, R, G, and B are represented by red, green, and blue light, respectively.

) The output ratio of the normally available light source 1 tends to be high on the long wavelength side and low on the short wavelength side, as shown in Figure 4, while the output distribution of the image pickup tube is generally higher on the green wavelength side, as shown in Figure 5. Since there is a peak near the area, when the output distribution of the light source and the image pickup tube are considered, the characteristics as shown in FIG. 6 will be obtained.

Therefore, in order to obtain an output of R:G:B=1:1:1, it is necessary to regulate the output tendency of the light source with a color temperature correction filter.

However, due to the characteristics of filters that can actually be manufactured, it is difficult to reduce the output in the green region without reducing the output in the blue region. Therefore, if the output in the green region is cut, the output in the blue region will also decrease, or the output in the red region will also decrease. If you drop R:G, the green and blue regions will also be affected.
:B=1:1:1, as shown in FIG. 7, the output ratio is about 1/5 to 1/10 compared to FIG. 6 before the filter is inserted.

Therefore, if the output of the light source used is constant, the amount of bias light will be insufficient and a corresponding burden will be placed on the electrical system of the television camera, but the cause of this is due to the color temperature of the light source and the output distribution of the image pickup tube. This is because it is not possible to realize a color temperature correction filter that has characteristics that effectively regulate the three wavelength regions.

On the other hand, in the relay lens system shown in FIG.
18 or 19, the image is formed on the light receiving surface of each image pickup tube.

However, the relay lens type bias device also requires a color temperature correction filter 12 that regulates the R, G, and B regions, similar to the prism type bias device, so it has the disadvantage that the bias light output is likely to be insufficient, and the light source 11 When the bias light is guided through the color temperature correction filter 12,
It is affected by the vignetting of the lens system 17, 18 or 19, resulting in what is called a shading phenomenon in television cameras, so it is not suitable for use in television cameras with high specification performance such as those used in broadcasting stations.

The present invention aims to solve the above-mentioned problems, and embodiments of the present invention will be described below.

In FIG. 3, reference numeral 29 denotes a variable power section of the zoom lens, which is composed of a focusing lens 29a, a variator 29b, a compensator 29c, and an erector 29d.

30 is a zoom lens aperture, and 32 and 32' are fixed imaging lenses, which are usually called relay lenses.

31 is a first color separation system, which is a dichroic mirror that reflects blue.

The light that leaves the subject and passes through the variable magnification unit 29 of the zoom lens enters the first color separation system 31 and is first separated into two colors by reflection and transmission.The reflected light then passes through the fixed imaging system 32 and It passes through the reflection prism 35, becomes parallel to the optical axis of the zoom lens, and forms an image on the light receiving surface of the photographing tube 38 for blue color.

On the other hand, the light transmitted through the first color separation system 31 is transmitted to the fixed imaging system 32'.
The light then enters the second color separation systems 33 and 34.

The second color separation system consists of a red reflective dichroic film 33b sandwiched between the first prism 33 and the second prism 34, and further separates the light transmitted through the first color separation system into two different colors. The light reflected by the dichroic film is totally reflected on the inner surface of the entrance surface of the first prism 33 and forms an image in the receiving direction of the red photography tube 36, and the light transmitted through the dichroic film passes directly through the second prism 34. An image is formed on the light receiving surface of the green image pickup tube 37.

In this case, the angle between the dichroic film surface of the first color separation system and the optical axis is set to 45 degrees or more in terms of air, thereby preventing deterioration of the polarization characteristics among the optical characteristics of the color television camera.

A bias illumination device is provided close to the entrance surface 35a of the total reflection prism 35 of the optical system configured as described above and the entrance surface 33a of the first prism 33 of the second color separation system.

The bias illumination device consists of a clamp rod 28, 28' having a diffused surface, a color temperature correction filter 27 for regulating blue characteristics, a color temperature correction filter 27' for regulating green and red characteristics, and tungsten lamps 26, 26'.

The light emitted from the lamp 26 passes through a color temperature correction filter 27 and enters a cladding rod 28, is reflected by a diffusing surface, exits from the cladding rod 28, passes through a total reflection prism 35, and enters a light receiving surface of a photographing tube 38.

Also, the light exiting the lamp 26' is filtered through a color temperature correction filter 27.
It enters the cladding rod 28' through the cladding rod 28', is reflected by the diffusing surface, and exits from the cladding rod 28' through the first prism 3.
3 and the second prism 34, and enters the light-receiving surfaces of the photographing tube 36 and the photographing tube 37.

As described above, the present invention separates incident light into two colors, transmitted and reflected, using a color separation system provided between the front and rear groups of the photographic lens, and further separates the incident light into two different colors using another color separation system provided behind the rear group. an optical system for a color television camera that separates the imaging light flux into two and guides it to each image pickup tube, wherein a plurality of image pickup tube auxiliary illumination devices are arranged to add a bias light beam to each of the imaging light beams separated by the first color separation system; According to the embodiment of the present invention, the light beam reflected by the first color separation system is guided to the imaging lens, the bias light flux is guided between the imaging lens and the image pickup tube, and the light beam reflected by the first color separation system is guided to the imaging tube. Another bias light beam is guided between the group of imaging lenses and the image pickup tube.

Therefore, among the R, G, and B outputs shown in Figure 6, the B output and the R and G outputs can be corrected independently, so the R, G, and B outputs can be kept constant. In this case, bias light can be used effectively.

In the above-described embodiment, two bias illumination devices are provided, but a bias illumination device may be provided for each image pickup tube.

Furthermore, by adopting the optical system described in the embodiments of the present invention, it is possible to avoid deterioration of polarization characteristics due to the interference film, and in addition, since at least two image pickup tubes are parallel, it is possible to miniaturize the camera itself. It is something that can be done.

The first color separation system may be formed by prisms sandwiching dichroic films, and the bias device is not limited to illumination by clad rods.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of a well-known television camera optical system equipped with a bias illumination device, and FIG. 2 is a plan view showing another example. FIG. 3 is a plan view showing an embodiment of the present invention. Figure 4 is an output characteristic diagram of the light source of the image pickup tube auxiliary illumination device;
The figure shows the output characteristics of the image pickup tube, Figure 6 shows the output characteristics when bias light is received by the image pickup tube, and Figure 7 shows the output when the output shown in Figure 6 is corrected using a color temperature correction filter. Characteristic diagram. In the figure, 29 is a zoom unit, 31 is a dichroic mirror,
32 and 32' are relay lenses, 33 is a first prism, 3
3b is a dichroic film, 34 is a second prism, 35 is a total reflection prism, and 36, 37, and 38 are image pickup tubes.

Claims (1)

[Claims] 1 The photographing light flux that has passed through the objective lens is separated into transmission and reflection by the first color separation system, and further separated into two colors, transmission and reflection, by the second color separation system, and the three-color light is sent to each image pickup tube. In the color television optical system for guiding, a plurality of image pickup tube auxiliary illuminators are arranged, each adding a different bias light beam to the imaging light beam separated by the first color separation system, and an image pickup tube for blue light and an image pickup tube for green light are arranged. 1. An optical system for a television camera incorporating an image pickup tube auxiliary illumination device, characterized in that bias light beams for illuminating the image pickup tube are supplied from different image pickup tube auxiliary illumination devices.