JPH07236152A - Video camera - Google Patents

Abstract

PURPOSE:To stably correct white balance by surely fixing a clamp level by an optical black pulse for prescribing the clamping period of a color difference signal. CONSTITUTION:During the optical black period of a CCD 12, an optical black pulse is inputted from a timing generating circuit 14 to respective clamp circuits 32a, 32b. Al though the optical black pulse is originally used for setting up the DC potential of a black level in a video signal, the pulse is inputted also to the circuits 32a, 32b, so that the DC potential of the black levels of respective color difference signals R-Y, B-Y can be set up. The white balance of a video is corrected by color difference signals outputted from the circuits 32a, 32b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera, and more particularly to a video camera that clamps color difference signals to generate a signal for white balance correction.

[0002]

2. Description of the Related Art In order to correct the white balance of an image using a color difference signal, it is first necessary to clamp the color difference signal and set a DC potential of the black level of the color difference signal. Therefore, in the conventional video camera, the clamp pulse is created based on the composite blanking pulse, and the color difference signal is clamped by the clamp pulse.

[0003]

However, in such a conventional video camera, since the clamp pulse rises for a predetermined period in synchronization with the rise of the composite blanking pulse, the clamp circuit clamps the video signal portion of the color difference signal. However, the clamp level of the color difference signal may differ depending on the level of the video signal. That is, in the conventional video camera, the white balance is corrected at different clamp levels,
There is a problem that the white balance correction operation becomes unstable.

Therefore, a main object of the present invention is to provide a video camera which can reliably make a clamp level constant and perform stable white balance correction.

[0005]

According to the present invention, in a video camera for clamping a color difference signal to generate a signal for white balance correction, an optical black pulse is used for defining a clamp period. It is a video camera.

[0006]

In the optical black period immediately before the horizontal blanking period of the CCD (Charge Coupled Device), for example, an optical black pulse is input from the timing generating circuit to the color difference signal clamping circuit. This optical black pulse is originally a pulse used to clamp the video signal in the signal processing circuit and set the DC potential of the black level of the video signal, and this pulse is input to the clamp circuit of the color difference signal. As a result, the black level DC potential of the color difference signal is set. Then, the white balance of the image is corrected based on the color difference signal output from the clamp circuit.

[0007]

According to the present invention, since the optical black pulse is used to define the clamp period of the color difference signal, the clamp potential can be reliably made constant and stable white balance correction can be performed. . The above objects, other objects, features and advantages of the present invention are
It will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a video camera 10 of this embodiment includes an image pickup device, that is, a CCD 12. CCD
From 12, a video signal is output according to the timing pulse output from the timing generation circuit 14, and this video signal is taken into the signal separation / color separation / matrix circuit 16 according to the timing pulse output from the timing generation circuit 14. Here, the CCD 12 is, for example, an integrated circuit "ICX055A" manufactured by Sony Corporation.
K ”is used as the timing generation circuit 14, for example, an integrated circuit“ CXD1257A ”manufactured by Sony Corporation.
R ″ can be used.

In such a CCD 12, for example, the total number of pixels is 537 (horizontal direction) × 597 (vertical direction), and the number of effective pixels is 500 (horizontal direction) × 582 (vertical direction). Then, as shown in FIG. 2, optical black images are arranged in the front end 7 pixels and the rear end 30 pixels in the horizontal direction and in the front end 1 pixel and the rear end 14 pixels in the vertical direction.

The level of the video signal taken in by the color separation circuit 16 is adjusted based on the optical black pulse output from the timing generation circuit 14 in the optical black period immediately before the horizontal blanking period, and the signal is separated and separated. The color separation / matrix circuit 16 separates the luminance signals Y, R, G and B signals. Of these signals, the G signal is directly input, and the R signal and B signal are input to the color process circuit 22 via the amplifier circuits 18 and 20, respectively. In the color system process circuit 22, the input R signal, G signal, and B signal are clamped based on the optical black pulse, and the color difference signal R
-Y and BY are created, and the color difference signal signals RY and BY are input to the video circuit 24. The luminance signal Y output from the signal separation / color separation / matrix circuit 16 is clamped in the luminance system process circuit 21 based on the optical black pulse, and then,
It is input to the video circuit 24.

The color difference signals RY and BY are also clamp circuits 32a and 32 included in the standard cell IC 30 via amplifiers 28a and 28b, respectively.
Input to b. In the clamp circuits 32a and 32b, the output of the timing generation circuit 14 shown in FIG.
Based on the optical black pulse shown in (B),
The black level DC potentials of the color difference signals RY and BY shown in FIG. 3A are set. The color difference signals RY and BY output from the clamp circuits 32a and 32b are
The integrating circuits 34a and 34b perform integration for one frame period, and the integration results of the integrating circuits 34a and 34b are given to the gain control circuits 36a and 36b. Based on this, gain control signals are applied from the gain control circuits 36a and 36b to the amplification circuits 18 and 20, the amplification factors of the amplification circuits 18 and 20 are adjusted, and the white balance of the image is corrected.

The standard cell IC30 is an integrated circuit "LC97000" manufactured by Sanyo Electric Co., Ltd.
A "can be used. In operation, the CCD 12
The video signal output from the video signal is separated by a signal separation / color separation / matrix circuit 16 into luminance signals Y, R signals, B signals, and G signals, of which the luminance signal Y passes through a luminance system process circuit 21 to a video circuit. 24 is input. Also, G
The R signal and the B signal are input to the color process circuit 22 through the amplifier circuits 18 and 20 as they are.
Then, the color difference signals R-Y and B-Y output from the color system process circuit 22 are input to the video circuit 24 as they are. The color difference signals R-Y and B-Y are also sent to the amplifier 28.
clamp circuits 32a and 32b through a and 28b
Entered in. Then, the clamp circuits 32a and 32
The color difference signal in which the DC potential of the black level is set based on the optical black pulse in b is integrated in the integrating circuits 34a and 34b. In the integrating circuits 34a and 34b, the color distribution of the image for one frame is averaged,
The color components that make up the color distribution are canceled. Based on the integration result, the gain control signals output from the gain control circuits 36a and 36b are used to amplify the amplifier circuits 18 and 20.
Is adjusted to correct the white balance of the image.

According to this embodiment, the color difference signals R-Y and B-Y are clamped by using the optical black pulse, so that the color difference signals R-Y and B-Y are clamped.
Since the DC potential of the black level is set, stable white balance correction can be performed. That is, since the clamp level does not change according to the video signal level, the clamp level can be reliably kept constant and stable white balance correction can be performed.

Although the present invention has been described as a video camera, it goes without saying that the video camera includes not only a general video camera but also an electronic still camera and a surveillance camera (industrial camera). .

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is an illustrative view showing a part of the embodiment in FIG.

FIG. 3A is a waveform diagram showing a color difference signal, and FIG.
FIG. 4 is a waveform diagram showing an optical black pulse.

[Explanation of symbols]

 10 ... Video camera 12 ... CCD 14 ... Timing generation circuit 18, 20 ... Amplification circuit 32a, 32b ... Clamp circuit 34a, 34b ... Integration circuit 36a, 36b ... Gain control circuit

Claims (1)

[Claims] 1. A video camera for clamping a color difference signal to generate a signal for white balance correction, wherein an optical black pulse is used to define a clamp period.