JPH0750934B2 - Digital video camera - Google Patents

Description

The present invention relates to digital signal processing for video cameras.

<Prior Art> FIG. 3 shows an example of a configuration of a video camera by analog signal processing.

Conventionally, signal processing of video cameras has been performed by analog signals, but with the progress of IC technology, digital ICs can be miniaturized and highly integrated, and signal processing that until now could only be done with analog signals was also performed. Recently, digital signal processing has become possible.

FIG. 4 shows a camera system in which the analog processing circuit configuration shown in FIG. 3 is digitized as it is. In the figure, the signal output from CCD1 is CDS in amplifier 2.
After being processed and AGC processed, the level is adjusted so as to match the input of the AD converter 3. Then, the AD converter 3 converts the digital signal, and the pixel separation circuit 4 separates the signal for each CCD filter. Then, the white balance circuit 5 adjusts the white balance, and the subtractor 6 produces a coloring signal. Then, a high-pass component is dropped by a low-pass filter (hereinafter referred to as “LPF”) 7, and RY and BY by a delay line 8 for one horizontal scanning period (hereinafter referred to as 1H).
Is converted into an NTSC signal by the encoder 9.

The CPU 10 sets the coefficient of the multiplier in the white balance circuit 5 and initializes the LPF 7.

<Problems to be Solved by the Invention> As described above, due to the remarkable progress in semiconductor technology, it has become possible to digitize and process various signals which were conventionally processed in an analog state. However, there is a problem in that simply replacing analog processing with digital processing makes the circuit scale very large and no practical advantage can be obtained.

That is, when the white balance circuit 5 is configured as shown in FIG. 5, the video signals from the pixel separation circuit 4 are respectively multiplied by the coefficients of the CPU 10 by the multipliers 5a and 5b, and subtracted by the subtractor 6 to obtain the color difference. It becomes a signal and the high frequency component is dropped by LPF7. Unlike the analog filter, the digital filter that composes the LPF7 has a coefficient that can be set from the outside so that the filter characteristics can be changed relatively easily.

In the conventional camera system described above, the coefficients of the multipliers 5a and 5b of the white balance circuit 6 are 8 bits and the AD converter 3 is 8b.
If it and data are changing at 10MHz, the input of LPF7 is 16pit or more, the data change is 10MHz, and the circuit scale becomes significantly large.

The present invention has been made in view of the above problems, and provides a digital video camera in which signal processing is devised as much as possible to reduce the circuit scale and simplify the circuit.

<Means for Solving the Problems> For the above-mentioned purpose, the present invention digitizes the output of the image sensor in a digital video camera which digitally processes the output of the image sensor to form a camera output signal. A first converter including an AD converter, a circuit for separating a digitized image sensor output into pixels corresponding to color components of an image sensor filter, and a multiplier to which each separated component is input and which has a predetermined coefficient. And a second low-pass filter, and a control circuit for controlling the coefficients of the multipliers of the first and second low-pass filters so that the output difference between the achromatic parts is zero. The present invention provides a digital video camera.

<Operation> In the present invention described above, even if an LPF is provided for each separated filter component to perform white balance, the circuit scale of the LPF does not increase from the conventional configuration, and the white balance circuit of the conventional configuration does not increase. Multiplier becomes unnecessary.

<Example> An example of the present invention is shown in FIG.

The signal output from CCD1 is CDS processed by amplifier 2 and AG
The signal is adjusted so as to match the input of the AD converter 3 while being subjected to C processing, and is converted into a digital signal by the AD converter 3. Then, the digitized video signal is separated by the pixel separation circuit 4 for each color filter provided in the CCD 1, and is input to LPF12 and LPF13 for each separated color signal.

The LPF12 and LPF13 drop the high frequency components contained in each color signal, and the separated color signals have different signal levels for each color, so the achromatic portion (LPF12 output)-(L
The white balance is adjusted by changing the respective coefficients of the LPF 12 and LPF 13 by a control signal from the CPU 10 so that the output of the PF 13) becomes 0. At this time, the characteristic of the digital filter that constitutes the LPF changes as shown in FIG. 2, and even if the output level is changed by changing the coefficient, the frequency characteristic does not change. It is not damaged as a video camera output.

The outputs of the LPF 12 and LPF 13 are converted into color difference signals by the subtracter 6, and the output line sequential color difference signals of RY and BY are 1
The H delay line 8 separates the R-Y and B-Y synchronized signals, and further, through an encoder 9, the signals are converted into NTSC television signals.

In the digital video camera system with the above configuration, LPF1
The input of 2 and LPF13 is 8 bits, and the data change is 5MHz. Even if the LPF is divided into two systems, the circuit scale of the LPF does not increase from the conventional system, and the multiplier required by the conventional system is It becomes unnecessary.

<Effects> As described above, according to the present invention, it is possible to eliminate the need for a white balance multiplier when digitizing a video camera system, prevent the circuit scale from increasing, and further improve the practicality of the digital video camera. You can

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of a video camera system showing an embodiment according to the present invention, and FIG. 2 is an LP applied to the embodiment.
Fig. 3 is a diagram showing characteristics of F, Fig. 3 is a block diagram showing a main part of a conventional video camera, Fig. 4 is a block diagram showing a system in which the configuration of Fig. 3 is digitized, and Fig. 5 is a white balance circuit. FIG. 3: AD converter, 4: Pixel separation circuit 6: Subtractor, 10: CPU, 12, 13: LPF

Claims (1)

[Claims] 1. A digital video camera for digitally processing an output of an image sensor to form a camera output signal, an AD converter for digitizing the output of the image sensor, and a color of the image sensor filter for digitizing the output of the image sensor. A circuit for pixel-separating corresponding to the component, first and second low-pass filters each having a multiplier having a predetermined coefficient to which the separated component is input, and the first and second low-pass filters And a control circuit for controlling the coefficient of the multiplier of 1 to a coefficient such that an output difference between achromatic parts becomes zero.