JPS61253752A - Image pickup device - Google Patents

Abstract

PURPOSE:To automatically control the variation of the black level which is caused by the variation of sensitivity resulting from temperature variation and differs for each channel by providing the face plate with a means for introducing reference light other than the external light of the subject and bias light onto a photoconductive film. CONSTITUTION:After the signal of reference light 10 is read from a small window area (B) during the system blanking, in a comparing circuit 15 the read signal is compared with the reference signal from a reference signal generator 14. Variation in the sensitivity of the photoconductive film 2 is detected by its temperature variation. The above comparison result is used to control the pedestal level of a pedestal-level-setting circuit 16 and the gain of a gain-setting circuit 17 before the controlled pedestal level and gain are delivered to a signal- treating system 18. The same operation is performed for the other channels. Accordingly, it is possible to automatically control the black level reference which conventionally needed to be recontrolled for each use due to the temperature characteristic specific to each channel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an imaging device in which the temperature dependence of photoconductive film sensitivity is improved.

[Background of the invention]

Generally, photoconductive films used in image pickup tubes have different temperature dependencies for each color. -Television cameras that use an image pickup tube usually use a bias light to reduce residual light.
Even in the state where external light is completely blocked, a signal current due to the bias light light still flows.For example, in a three-tube imaging device, the bias light light also passes through red, green, and blue color filters before entering the camera. Since the signals for these lights are flowing even after the aperture I) is closed, the state in which signal currents are flowing for each color is used as the reference for the black level.

However, as mentioned above, the temperature dependence of the sensitivity of the photoconductive film differs for each color, so in the past, it was necessary to adjust the black level standard appropriately when using an imaging device (for example,
Broadcasting Technology Book 1 "Broadcast System Overview" 1 Japan Broadcasting Corporation, 1st printing, see pages 49-53).

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging device that reduces fluctuations in black level due to temperature changes.

[Summary of the invention]

In order to achieve such an object, the present invention provides a means for injecting reference light onto a photoconductive film that is not irradiated with light, in addition to the incident light from the subject and the bias light light, on the face plate of the image pickup tube. The reference light is used to correct the amount of signal current caused by the severe slide light for each channel, thereby suppressing fluctuations in the black level due to temperature changes.

[Embodiments of the invention]

Next, embodiments of the present invention will be described in detail using the drawings.

Fig. wc1 is a diagram of one channel of the imaging tube of the ninth three-tube imaging device for explaining an example of the imaging device according to the present invention, and FIG. is a BB' cross-sectional view thereof. In the same figure.

1 is a face plate made of a translucent glass plate, 2 is a photoconductive film formed on the inner surface of the face plate 1, and 3 is a mesh electrode 4 inside.
An extraneous tube houses an electron gun structure such as a focusing electrode 5, an indium electrode 6 is connected to the photoconductive film 2 and hermetically seals the face plate 1 and the outer tube 3, and T is wound around the outer surface of the indium electrode 6. The tth target ring 8 takes out the signal current, and 8 is an effective scanning area A that introduces external light and bias light light into the front surface of the face plate 1, and a small window area B that introduces light other than external light and bias light light. It is a nine-black mask that is formed by applying black paint, etc. to the surface except for the area. Therefore, this face plate 1 has a configuration in which only the large effective scanning area and the small window area B are translucent and can transmit light. Reference numeral 9 denotes a light guide tube, which has an end face of, for example, fiberglass placed in close contact with the small window area B of the face plate 1, and guides only the reference light 10 other than external light and bias light light. In this case, it is desirable that the reference light 10 introduced from this small window area B has the same spectral spectrum as the bias light light incident on the image pickup tube of each channel.

FIG. 3 is a block diagram of an imaging device for one channel of the three-tube imaging device using the aforementioned imaging tube. In the figure, 11 is a next color filter arranged in front of the face plate 1;
Reference numeral 12 denotes external light and bias light light from the subject that enters the color filter 11, 13 a preamplifier that amplifies the ratio signal current output from the target ring 7, and 14 a reference signal generator that sets and outputs a predetermined reference signal. 15 is a comparison circuit, 16 is a pedestal level setting circuit, 17 is a gain setting circuit, and 1B is a signal processing system.

In such a configuration, the signal of the reference light 10 is read out from the small window area B during the system blanking period, and the signal is set in advance and compared with the reference signal of the nine reference signal generators 140 in the comparator circuit 15 to determine the temperature. The fluctuation in the sensitivity of the photoconductive film 2 is detected by the fluctuation, and the pedestal level setting circuit 1
6 and adjust the gain of the gain setting circuit 17.

It is output to the signal processing system 18. Do the same for other channels as well. This makes it possible to automatically adjust the black level standard, which previously had to be readjusted each time it is used due to the different temperature characteristics of each channel.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to automatically adjust black level fluctuations caused by temperature fluctuations with different sensitivities for each color channel, which is an extremely excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating an example of an imaging device according to the present invention, and FIG. 2 is a block diagram of its main parts. DESCRIPTION OF SYMBOLS 1... Face plate, 2... Photoconductive film, 3... Outer tube, 4... Mesh electrode, 5... Focusing electrode, 6...
...Indium electrode, T...Target ring,
8φ...black mask, 9...light guide tube, 1o...
・Reference light, 11... One color filter, 12--゛... External light and bias light light, 13... Preamplifier,
14...Reference signal generator, 15...Comparison@road. 16...Pedestal level setting circuit, 1T...
Gain setting circuit, 18...signal processing system. Figure 1 (Q) (b) Figure 2

Claims (1)

[Claims] In an imaging device including at least a plurality of image pickup tubes each having a photoconductive film on the inner surface side of the face plate and a black mask on the front side in a portion other than the effective scanning area, the face plate is provided with external light from a subject, bias light An imaging device comprising a reference light input means for introducing reference light other than light into a photoconductive film.