JPH01185084A - Video camera - Google Patents

Abstract

PURPOSE:To avoid photographing an image with a bad S/N and to obtain a satisfactory image by suppressing the maximum gain of an automatic again control circuit to be small at the time of a high-speed shutter mode. CONSTITUTION:When a shutter speed is made high-speed, the maximum gain is suppressed to be small by a maximum gain control circuit 7. It means that, when a photographing place is dark, a signal output level is made small and the shutter speed is forced to be compulsorily switched to be low-speed. When the shutter speed is made low-speed in such a way, a sensitivity in an image pick-up element 1 is raised, and the image with the good S/N can be obtained. For example, when the low-speed shutter speed is 1/60sec and the high-speed shutter speed is 1/1000sec, a sensitivity difference is made 1000/60 17-fold. Since the maximum gain is suppressed, a defect such as a flaw can be made inconspicuous.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a video camera whose shutter speed can be switched between high and low shutter speeds.

[Prior Art] Fig. 2 is a block diagram showing the configuration of a conventional video camera. In the figure, (1) is an image sensor, and this image sensor (1) is composed of, for example, a COD, and receives optical signals. into an electrical signal. (2) is the image sensor drive circuit;
Controls timing generation such as printer speed. (3) is the shutter speed selector switch, the normal shutter speed is l/60.
It is said that it is possible to switch at high speeds such as 1/1000 seconds. (4) is an automatic gain control circuit, which either amplifies the signal photoelectrically converted by the image sensor (1), or reduces the gain if the electric signal is large, and If the electrical signal is small, increase the gain. (5) is a camera process circuit, and this camera process circuit (5) performs signal processing as a camera. (6) is an output terminal.

Next, we will explain the operation of the above configuration with 6 image sensors (1
), the electrical signal converted from the optical signal is input to the automatic gain control circuit (4) and amplified. At this time, if the electrical signal is large, the gain is reduced, and if the electrical signal is small, the gain is increased to maintain the output level constant.

However, it is not possible to obtain a gain greater than a certain value.

Next, the single-level signal output from the automatic gain control circuit (4) is input to the camera processing circuit (5), where it is processed by the camera, and then sent to the terminal (6).
is output from.

The operation as described in L is performed based on switching between low speed and high speed using the shutter speed changeover switch (3).

[Problems to be Solved by the Invention] In the conventional video camera configured as described above, when the shutter speed is increased, the amount of light decreases and the sensitivity decreases, so the gain of the automatic gain control circuit increases. ,
One of the drawbacks was that it was easy to shoot under poor S/N image conditions. In addition, when using the high-speed shutter mode, problems tend to occur in the transfer of the image sensor, and defects such as scratches are likely to occur.

This invention was made in order to solve the above-mentioned problems, and provides a video camera that can obtain images with good S/N and in which defects such as kisses are not noticeable even when set to high-speed shutter mode. The purpose is to

[Means for Solving the Problems] A video camera according to the present invention is characterized by being provided with a maximum gain control circuit that controls the automatic gain control circuit to suppress the maximum gain to a small value when the shutter speed is increased. do.

[Function] According to the present invention, when the shutter speed is increased, the maximum gain of the automatic gain control circuit is controlled to be small, thereby increasing the sensitivity of the image sensor and reducing the S/N.
#M shadow of a good image is possible.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a video camera according to an embodiment of the present invention.
) have the same structure as the conventional example shown in FIG. 2, so the same reference numerals are given and detailed explanation thereof will be omitted.

In FIG. 1, (7) is a maximum gain control circuit, and this maximum gain control circuit (7) operates to suppress the maximum gain of the automatic gain control circuit (4) when the shutter speed is increased.

Next, the operation of the above configuration will be explained.

The operations from photoelectric conversion by the image sensor (1) to signal processing by the camera process circuit (5) are the same as in the conventional example, but when the shutter speed is set to high speed, the maximum gain control circuit (7) This will keep the gain small.

This means that when the shooting location is dark, the signal output level decreases, forcing the shutter speed to be switched to a low speed. When the shutter speed is made low in this manner, the sensitivity of the image sensor (1) increases and an image with a good S/N ratio can be obtained.

For example, in the case of a slow shutter speed of 1/60 seconds and a high shutter speed of 1/1000 seconds, the sensitivity difference is 17 times that of 1000/60.

Also, since the maximum gain is suppressed, defects such as scratches become less noticeable.

Note that the high-speed shutter mode is limited to outdoor use where sufficient light can be obtained, such as when recording golf swings, so the sensitivity is sufficient and there will be no problem even if the maximum gain is limited. will not occur.

[Effects of the Invention] As described in E, according to the present invention, by suppressing the maximum gain of the automatic gain control circuit to a small value during the high-speed shutter mode, it is possible to avoid capturing images with poor S/N. Moreover, there is no problem with image pickup device transfer, and it is possible to obtain images that are free from defects such as scratches.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of a video camera according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a conventional video camera. (+)...Image sensor, (3)...Shutter speed selection switch, (4)...Automatic gain control circuit, (5)...
-Camera process circuit, (7)--maximum gain control circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) In a video camera equipped with an image sensor, a shutter speed changeover switch, and an automatic gain control circuit, when the shutter speed is set to a high speed by the changeover switch, the above automatic gain control circuit A video camera characterized in that a maximum gain control circuit is provided for controlling the maximum gain of the gain control circuit to be small.