JP2000115633A - Video camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video camera capable of correcting the difference in input light quantity between the center part and peripheral part of an image pickup element generated by the characteristics of an image pickup lens. SOLUTION: In this video camera provided with a diaphragm adjustment mechanism for automatically and/or manually adjusting a stop value, in order to correct the difference in the input light quantity between the center pat and peripheral part of the image pickup element generated by the characteristics of the image pickup lens, a control circuit 30 for controlling an AGC circuit 21 and/or a γ-correction circuit 22 is provided. In this case, the control circuit 30 controls the AGC circuit 21 and the γ-correction circuit 22, so as to correct the difference in the input light quantities between the center part and the peripheral pat of the image pickup element 13 generated by the characteristics of the image pickup lens 11 when the stop value is an open value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a video camera.

[0002]

2. Description of the Related Art When light is input to an image pickup device such as a CCD through an image pickup lens, the amount of light input to the image pickup device is smaller than the central portion of the image pickup lens due to the characteristics of the image pickup lens. Less. Therefore, in the obtained video, the screen has a bright central portion and a dark peripheral portion. Such a phenomenon is affected by the aperture of the imaging lens, and becomes more conspicuous as the aperture is closer to the open value.

For this reason, as the aperture becomes closer to the open value, the difference in brightness between the central portion and the peripheral portion of the obtained image becomes large, and the subject cannot be reproduced faithfully. In addition, when the aperture is set to an open value, the subject generally has low illuminance in many cases, and thus the subject reflected in the peripheral portion of the screen is often dark and invisible.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a video camera capable of correcting a difference in input light amount between a central portion and a peripheral portion of an image pickup device caused by characteristics of an image pickup lens. .

According to the present invention, the subject can be faithfully reproduced when the difference between the amounts of light incident on the central portion and the peripheral portion of the image pickup device becomes large due to the characteristics of the image pickup lens as the aperture approaches the open value. The aim is to provide a video camera.

[0006]

According to the present invention, there is provided a video camera provided with an aperture adjustment mechanism for automatically and / or manually adjusting an aperture value. And a control means for controlling the AGC circuit and / or the γ correction circuit so as to correct the difference in the input light amount between the peripheral portion and the peripheral portion.

For example, the control means may correct the difference in the input light amount between the central portion and the peripheral portion of the image pickup device caused by the characteristics of the image pickup lens in accordance with the aperture value adjusted by the aperture adjustment mechanism. The one that controls the AGC circuit and / or the γ correction circuit is used.

The control means corrects, for example, a difference in the amount of input light between the central portion and the peripheral portion of the image sensor caused by the characteristics of the image pickup lens when the aperture value adjusted by the aperture adjustment mechanism is an open value. For controlling the AGC circuit and / or the γ-correction circuit, a control circuit is used.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a video camera used in a surveillance system will be described below with reference to the drawings.

FIG. 1 shows a monitoring system.

The surveillance system includes a video camera 1, a VTR 2 for recording a video signal output from the video camera 1, and a monitor 3 for displaying a video signal output from the video camera 1.

The video camera 1 includes an image pickup lens 11, an aperture mechanism 12, an image pickup device 13 such as a CCD, and a signal processing circuit 14, similarly to a normal video camera. As is well known, the signal processing circuit 14 includes circuits such as an AGC circuit, a color separation circuit, a matrix circuit, a γ correction circuit, and an encoder. Only the circuit 21 and the γ correction circuit 22 are shown. Also, unlike the ordinary video camera, the video camera 1 has a control circuit 30 that controls the AGC circuit 21 and the γ correction circuit 22 based on the aperture value.
Is provided.

The control circuit 30 controls the AGC circuit 21 so as to correct the difference in the amount of input light between the central portion and the peripheral portion of the image pickup device 13 caused by the characteristics of the image pickup lens 11 when the aperture value is an open value. And the gamma correction circuit 22.

That is, the AGC circuit 21 changes the gain between the peripheral portion of the screen and the central portion of the screen, and the γ correction circuit 22 changes the gamma correction value between the peripheral portion of the screen and the central portion of the screen, thereby obtaining the image. The decrease in the amount of light to the periphery of the element 13 is corrected. This makes it possible to obtain a video output that is faithful to the brightness of the subject.

In the above embodiment, when the aperture value is an open value, the AGC circuit is configured to correct the difference in the amount of input light between the central portion and the peripheral portion of the image pickup device 13 caused by the characteristics of the image pickup lens 11. 21 and the γ correction circuit 22 are controlled, but are divided into a plurality of stages according to the aperture value to correct the difference in the input light amount between the central portion and the peripheral portion of the image sensor 13 caused by the characteristics of the image sensor 11. A
The GC circuit 21 and the γ correction circuit 22 may be controlled.

In the above embodiment, the imaging lens 1
Both the AGC circuit 21 and the γ correction circuit 22 are controlled in order to correct the difference in the input light amount between the central part and the peripheral part of the imaging device 13 caused by the characteristic of 1.
Only one of them may be controlled.

[0017]

According to the present invention, it is possible to correct the difference in the amount of input light between the central part and the peripheral part of the image sensor, which is caused by the characteristics of the image pickup lens.

Further, according to the present invention, even when the difference between the amounts of light incident on the central portion and the peripheral portion of the image pickup device becomes large due to the characteristics of the image pickup lens due to the aperture approaching the open value, the subject can be faithfully reproduced. You will be able to play it.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a monitoring system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Video camera 11 Imaging lens 12 Aperture mechanism 13 Image sensor 21 AGC circuit 22 γ correction circuit 30 Control circuit

Claims (3)

[Claims] 1. A video camera having an aperture adjustment mechanism for automatically and / or manually adjusting an aperture value, wherein a difference in input light amount between a central portion and a peripheral portion of an image sensor caused by characteristics of an imaging lens is corrected. AGC
A video camera provided with control means for controlling a circuit and / or a gamma correction circuit. 2. An AGC system according to claim 1, wherein said control means corrects a difference in input light amount between a central portion and a peripheral portion of the image sensor, which is caused by characteristics of the image pickup lens, according to the aperture value adjusted by the aperture adjusting mechanism. 2. The video camera according to claim 1, wherein the video camera controls a circuit and / or a gamma correction circuit. 3. The control means corrects a difference in input light amount between a central portion and a peripheral portion of an image sensor caused by characteristics of an image pickup lens when an aperture value adjusted by an aperture adjusting mechanism is an open value. 2. The video camera according to claim 1, wherein the video camera controls the AGC circuit and / or the gamma correction circuit.