JPH087743Y2 - Video camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a video camera.

[Conventional technology]

FIG. 3 is a block diagram showing the structure of a conventional video camera. (1) is a lens, (2) is an automatic diaphragm device,
(3) is a solid-state image sensor, (4) is an automatic gain control circuit,
(5) is a signal processing circuit, (6) is a drive circuit, and (7) is a synchronization signal generation circuit.

 Next, the operation will be described.

The light incident from the lens (1) has an appropriate amount of light by the automatic diaphragm device (2) and forms an image on the solid-state image sensor (3).
If the brightness of the subject decreases here, the automatic diaphragm device (2)
The diaphragm at is close to opening. If the brightness of the subject further decreases after the aperture is fully opened, the solid-state image sensor (3)
The output signal of is amplified to an appropriate level by the automatic gain control circuit (4). After that, the signal processing circuit (5) performs signal processing such as gamma correction, white clipping, and addition of a sync signal.

[Problems to be solved by the invention]

Since the conventional video camera is configured as described above, when the temperature of the solid-state image sensor (3) rises when the brightness of the subject is low and the gain of the automatic gain control circuit (4) is high, There is a problem in that the variation in dark current of each pixel formed by means of appears as fixed noise on the screen and significantly deteriorates the image quality. On the contrary, if the maximum gain of the automatic gain control circuit (4) is set small considering the influence of dark current at high temperature,
There is a problem that it is connected to something with low sensitivity.

The present invention has been made in order to solve the above problems, and an object thereof is to provide a video camera capable of ensuring high sensitivity and obtaining good image quality regardless of temperature.

[Means for solving problems]

The video camera according to the present invention is provided with a temperature detector for detecting the temperature of the solid-state image sensor or the temperature around the solid-state image sensor, and the maximum value set in the automatic gain control circuit in inverse proportion to the temperature detected by the temperature detector. The gain is changed.

[Action]

In this invention, even when the brightness of the subject is low and the maximum gain of the automatic gain control circuit is large, if the temperature of the solid-state image sensor becomes high, the maximum gain is reduced and the dark current of the solid-state image sensor is decreased. Is less likely to appear on the screen, in other words, the maximum gain is kept at an appropriate value at room temperature, so that the sensitivity at room temperature is not lowered.

[Example of device]

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

FIG. 1 is a block diagram showing an example of a video camera according to the present invention. The same parts as those in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted.

In the figure, (10) is a temperature detector for detecting the temperature of the solid-state imaging device (3) or the temperature around the same,
It is set so that the maximum gain of the automatic gain control circuit (4) is changed in inverse proportion to the detected temperature. (4a) is a maximum gain setting terminal in the automatic gain control circuit (4).

Next, the operation of the above configuration will be described with reference to FIG.

Figure 2 shows the brightness of the subject and the automatic gain control circuit (4).
It is a figure which shows the relationship with the gain of. In FIG. 2, the solid line shows the gain of the automatic gain control circuit (4) when the temperature is low and the dark current is small. When the temperature of the solid-state image sensor (3) rises and the dark current increases, the temperature detector (10) detects this rise in temperature and the maximum gain setting terminal (4a) of the automatic gain control circuit (4) maximizes the maximum gain. Is decreased as the temperature rises as indicated by the dotted line.

As a result, variations in the dark current of the solid-state image sensor (3) at the time of high temperature are less likely to appear as fixed noise on the screen, and good image quality can be maintained. This can be avoided by setting the maximum gain of the automatic gain control circuit (4) to a small value in consideration of dark current at high temperature, so that there is no fear of lowering the sensitivity at room temperature.

In the above embodiment, the relationship between the temperature increase and the maximum gain is as long as the relationship between the temperature increase and the dark current increase is taken into consideration.
It may be a linear change, an exponential change, or a stepwise change.

[Effect of device]

As described above, according to the present invention, the maximum gain of the automatic gain control circuit is changed in inverse proportion to the detected temperature by detecting the temperature of the solid-state image sensor or the temperature around the solid-state image sensor. The image is not disturbed and the sensitivity at room temperature can be increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a video camera according to the present invention, FIG. 2 is a diagram showing a relationship between brightness of a subject and maximum gain, and FIG. 3 is a block diagram showing a configuration of a conventional video camera. . (3) ... Solid-state image sensor, (4) ... Automatic gain control circuit,
(10)… Temperature detector. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] 1. A solid-state image pickup device for forming an image of a subject, and an automatic operation which receives an output signal from the solid-state image pickup device and controls a gain with respect to a change in the brightness of the subject so that an output level becomes constant. A gain control circuit; and a temperature detector that detects the temperature of the solid-state imaging device or the temperature around the device and changes the maximum gain of the automatic gain control circuit in inverse proportion to the detected temperature. A video camera.