JPS60139085A - Anti-radiation color itv camera - Google Patents

Abstract

PURPOSE:To stabilize a white balance when radiant rays are exposed by providing a filter made of an anti-radiation glass which transmits the visible light having a wavelength range between the specific value and larger value to a color ITV containing a lens made of the anti-radiation glass. CONSTITUTION:Image pickup tubes 4-6 are provided to a color ITV camera, and a color separating optical system 3 is provided to these image pickup tubes. An anti-radiation lens 2 is set at the front of the system 3, and a filter 1 made of the anti-radiation glass which transmits the visible light having a wavelength range between the specific value and longer value is provided to the lens 2. The outputs of each color which are converted into electric signals by tubes 4-6 are amplified by preamplifiers 7-9, and the color components of each color are controlled to the same value by differential amplifiers 10-12 and applied to an encoder circuit 15 via process amplifiers 13-15. The specific wavelength of the filter 1 is set at 0.48mum. Thus a white balance is stabilized when the radiant rays are exposed.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to radiation-resistant color IT used in a gamma ray environment.
V (Industry Television,
The present invention relates to industrial television cameras, and particularly to radiation-resistant color ITV cameras with improved white balance stability.

[Background of the invention]

ITV cameras are used to monitor equipment 2, such as nuclear reactor equipment, in an environment where radiation is present.
ITV camera lenses are affected by exposure to radiation, such as changes in their characteristics. Special, general ITV
Camera lenses may turn black due to radiation exposure, resulting in extremely poor light transmittance. In order to eliminate such inconveniences, lenses using radiation-resistant glass are manufactured.

Although the transmittance of radiation-resistant lenses does not significantly attenuate due to radiation exposure, it does not mean that there is no attenuation at all, and a large change occurs depending on the exposure dose in the wavelength region from 0.4 μm to 0.5 μm. There is. FIG. 1 shows an example of changes in spectral transmittance when a radiation-resistant lens is exposed to radiation. Curve a is the characteristic curve 1 before exposure, or the characteristic after exposure to a radiation dose of 1o'R (X-ray).

When the spectral transmittance characteristics change due to exposure to radiation, the absorption of blue component light by the lens increases, so when a white object is displayed with a color ITV camera, a color image lacking the blue component is displayed on the TV monitor.

When a color ITV camera images a white object.

A state in which the color of the image is faithfully white is considered to be a well-balanced state and is one of the standards for color adjustment.

Therefore, if the blue component of the image is missing, the image will be in an unbalanced and inappropriate state.

In a color ITV, light transmitted through a lens is separated into blue component, line component, and red component light by, for example, a color separation optical system, and the light of each color component is converted into an electrical signal by an image pickup tube. If the amount of light of each color component passing through the lens is uneven, by adjusting the amplification factor of the amplification circuit for the electric signal, it is possible to equalize the intensity of each color signal and achieve white balance.

However, with this adjustment method, the white balance needs to be adjusted each time depending on the radiation intensity to which the color ITV camera is exposed, and a stable white balance cannot be maintained.

[Object of the Invention] The object of the present invention is to eliminate the above-mentioned disadvantages of the prior art,
To provide a color ITV camera whose white balance is stable even when exposed to radiation.

[Summary of the invention]

A feature of the present invention is that a color ITV camera equipped with a lens made of radiation-resistant glass is provided with a filter made of radiation-resistant glass that transmits visible light at a certain wavelength, for example, 0.48 μm, and on the longer wavelength side. It is in the configuration.

The present invention was made based on the following experimental findings. The experiment was conducted as follows. First, a lens with high transmittance over the entire visible light range was attached to the color ITV camera body.

Perform white balance adjustment. Next, sharp-cut color glass filters with different cutoff wavelengths are attached to the lens of the color ITV camera. A sharp-cut colored glass filter is a filter that has the characteristic of transmitting light with wavelengths longer than the cutoff wavelength. Since the sharp cutoff filter removes light on the short wavelength side and disrupts the white balance, it is necessary to adjust the amplification factor of the amplifier circuit to restore the white balance. However, there is a limit to the amplification factor of the amplifier circuit used to restore white balance.

Depending on the value of the cutoff wavelength of the sharp cut filter, it may not be possible to restore the white balance.

The results of experiments with two different cutoff wavelengths where the maximum amplification factor of the amplifier circuit is 20 (Ib).

The maximum cutoff wavelength that can restore white balance is 0.4
The result was 8 μm.

When a radiation-resistant lens is exposed to radiation, a large change in transmittance occurs on the short wavelength side of visible light, and the change is small on the long wavelength side. In the wavelength range of about 0.5 μm or more,
The transmittance at each wavelength is approximately equal. When a filter with a cutoff wavelength of 0848 μm is attached to a radiation-resistant lens, the light that passes through the filter and enters the lens is 0.48 μm.
The light has a wavelength longer than μm. Even if a radiation-resistant lens is exposed to radiation and its characteristics change, the radiation that enters the lens
For light with wavelengths longer than 8 μm, the change in transmittance is small, and the rate of change is almost the same.
The light amount ratio of each color component of green and red hardly changes.

Therefore, if a color ITV camera is equipped with a filter with a cut-off wavelength of 048 μm to achieve white balance, if the lens is made radiation resistant, the white balance will not deteriorate even when exposed to radiation, and the white balance will be stable. It will be a color ITV camera.

As described above, one aspect of the present invention is to cut off light on the shorter wavelength side than a certain wavelength from the light incident on the radiation-resistant lens of a color ITV camera, thereby destroying the white balance, and in this state, the white balance is adjusted using a circuit. This was done based on the results of experimentally determining the limits to which white balance can be reproduced when .

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a configuration diagram of a color ITV camera embodying the present invention, and FIG. 3 shows spectral transmittance characteristics of a filter attached to a lens in an embodiment of the present invention. This filter is a multilayer thin film made of radiation-resistant glass and a high refractive index material such as cerium oxide or zinc sulfide, and a low refractive index material such as magnesium fluoride alternately stacked on top. Figure 4 is the second
This is the spectral transmittance characteristic of the color separation optical system of the color TV camera shown in the figure.

In Fig. 2, the light that passes through the filter 1 and enters the radiation-resistant lens 2 has a wavelength range longer than 048 μm because the transmittance characteristics of the filter 1 are as shown in Fig. 3. . The light transmitted through the radiation-resistant lens 2 is separated by a color separation optical system 3 into blue (to) and green (to). Separated into red 0 color components. Of the separated color component lights, the blue component light has light in the wavelength range of 048 μm or less removed by the action of the filter 10.

The amount of light is significantly lower than that of green and red component light.

Each color component light is converted into an electrical signal by the image pickup tubes 4, 5.6, respectively. Among these electrical signals, the blue component electrical signal has a small amount of light, so it is smaller than the green and red component electrical signals.

The output signal from each image pickup tube is amplified by a preamplifier 7.8.9 and then amplified by a differential amplifier 10.degree. 11.12, respectively. At this time, the amplification factor of the differential amplifier is adjusted so that the signal values of each color component have the same value. In the embodiment, the amplification factor of the differential amplifier for the blue component was set to be 12 db larger than the amplification factors for the green and red components.

The electrical signals of each color component are amplified by a differential amplifier.

After gamma correction and signal level adjustment are performed by the process amplifiers 13, 14, and 15, the encoder circuit 16 further performs NTSC (National
i-sion System Cotrmi tee
(color one-way) signal. The NTSC signal is sent to a color TV monitor to display a white-balanced image on the screen.

Next, consider a case where the color ITV camera adjusted in this manner is exposed to radiation and the characteristics of the radiation-resistant lens change as shown by the curve in FIG. Since the light incident on the radiation-resistant lens passes through the filter 1, it has a wavelength range longer than 048 μm. The transmittance of a radiation-resistant lens that has been exposed to radiation is 048 μm or more.In the two wavelength ranges, the rate of change in transmittance at each wavelength is almost the same, so the light intensity ratio of each color component of blue, green, and red is It will be the same as in the previous case. Therefore,
Even if the transmittance in the wavelength range of 048 μm or less changes greatly due to radiation exposure, the white balance is kept constant in the color ITV camera of the 9th embodiment.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to stabilize the change in white balance of a color ITV camera caused by radiation exposure.

0, which has a very large effect when remotely observing the state of objects in a radiation environment with correct color information.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the spectral transmittance characteristics of a radiation-resistant lens, and FIG. 2 is a configuration diagram of a color ITV camera implementing the present invention.
FIG. 3 is a spectral transmittance characteristic diagram of the filter in FIG. 2, and FIG. 4 is a curve diagram showing the separation characteristics of the color separation optical system. <Explanation of symbols> 1...Filter 2°°° Radiation resistant lens 5...Color separation optical system 4-6... Image pickup tube-Am α■ 1n
Pu-mll J ^-4^ --1 Science Self-drawing Cap Intestine α13-15...Process amplifier 16...Encoder circuit representative patent attorney Junnosuke Nakamura 1 figure 2 figures 1 and 3 figures! j'4 figure jjl length 5tt Kugan

Claims (2)

[Claims] (1) A radiation-resistant color ITV characterized in that a color ITV camera equipped with a lens made of radiation-resistant glass is provided with a filter made of radiation-resistant glass that transmits visible light with wavelengths longer than a certain wavelength. camera. (2) The radiation-resistant color IT according to claim 1, wherein the specific wavelength is 0.48 μm.
V camera.