JPH05292527A - Digital video camera - Google Patents

Abstract

PURPOSE:To obtain a correct color signal independently of the difference of luminance value with respect to the digital video camera used in a VTR integrated camera or the like. CONSTITUTION:An output signal of a solid-state image pickup element 1 is separated into a luminance signal and a color signal, and the luminance signal is subjected to gamma correction by a gamma correction circuit 3, and the signal obtained by synthesizing the luminance signal subjected to gamma correction and the color signal in a luminance/color synthesizing circuit 4 is converted to a digital signal by an A/D converter 6 and is processed by a digital signal processing circuit 6 and is outputted. Thus, the correct color signal is obtained independently of the difference of luminance value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video camera used in a VTR integrated camera or the like.

[0002]

2. Description of the Related Art In recent years, with the development of digital signal processing technology, a digital video camera has been developed which performs signal processing of a video camera by digital signal processing. In a digital video camera, it is necessary to perform analog-to-digital conversion in order to perform digital signal processing, but when performing γ correction in digital signal processing, considering the gradation reproduction in the low-luminance part, the bit of the analog-to-digital converter is considered. The number must be larger than the number of bits of the signal after γ correction. However, since the power consumption and cost increase as the number of bits of the analog-digital converter increases, the conventional digital camera employs a method of performing γ correction before the analog-digital converter.

An example of a conventional digital camera will be described below with reference to the drawings. FIG. 6 is a block diagram showing the structure of a conventional digital camera. FIG. 7 is a waveform diagram showing the waveforms of the signals in FIGS. 6a and 6b when the color bar is imaged, FIG. 8 is a block diagram showing the internal processing of the digital signal processing circuit 6 of FIG. 6, and FIG. It is a waveform diagram when the output signal of the digital circuit at the time of imaging is displayed on the vectorscope.

In FIG. 6, 1 is a solid-state image sensor, 3 is γ
A correction circuit, 5 is an analog-digital converter, and 6 is a digital signal processing circuit. In FIG. 7, the horizontal axis is the time axis,
The vertical axis represents the signal voltage level. In FIG. 8, 7 is a luminance color separation circuit, 8 is a white balance circuit, 10 is a matrix circuit, 11 is a luminance signal output terminal, and 12 is a color difference signal output terminal.

In the single-chip camera as shown in FIG. 6, the output signal of the solid-state image pickup device 1 is a signal obtained by adding the modulation component of the color signal to the luminance signal. The luminance signal is Y and the modulation component of the color signal is C. Then, it is represented by (Y + C). In this signal, for example, when a color bar is imaged, the signal of one line has a waveform as shown in FIG. 7a. The colors are arranged in the order of white, yellow, cyan, green, magenta, red, and blue from the top of the staircase waveform in FIG. 7. The .gamma. Correction circuit 3 performs .gamma. Correction on such a signal, and the characteristics of the .gamma. Correction circuit 3 are generally obtained by setting the standard level of the input signal to 1 by the .gamma.th power of the signal level. Therefore, the output signal of the γ correction circuit 3 is represented by (Y + C) to the γth power, and the waveform when the color bar is imaged is as shown in FIG. 7B.

A point to be noted here is that the color components of each signal represented by an AC waveform are compressed in yellow or cyan having a high luminance level and expanded in red or blue having a low luminance level. is there. This signal is converted into a digital signal by the analog-digital converter 5 and input to the digital signal processing circuit 6. In the digital signal processing circuit 6, the luminance signal and the color signal are separated in the luminance color separation circuit 7 of FIG. 8, and the luminance signal is output from the luminance signal output terminal 11. Next, the separated color signals are subjected to white balance processing by the white balance circuit 8 and input to the matrix circuit 10. The color signals input to the matrix circuit 10 are converted into color difference signals and output from the color difference signal output terminal 12.

FIG. 9 shows an output color difference signal when a color bar having different brightness is picked up in three stages is displayed on a vector scope. Originally the brightest signal, that is, the outermost signal on the vectorscope must enter the so-called field pattern.

[0008]

However, in the conventional structure as described above, the color signals of yellow and cyan signals having a high luminance value are compressed by γ correction, while red and red signals having a low luminance value are compressed. Since the color signal of the blue signal is expanded, the saturation of the yellow and cyan signals becomes smaller than it really is, and the saturation of the red and blue signals becomes larger than it really was.

In view of the above point, the present invention has an object to provide a digital video camera used for a VTR integrated camera or the like which can obtain a correct color signal regardless of a difference in luminance value.

[0010]

To achieve the above object, the present invention provides a solid-state image pickup device, a luminance color separation circuit section for separating an output signal of the solid-state image pickup device into a luminance signal and a color signal, and the luminance. A γ correction circuit that performs γ correction on the signal,
A luminance color synthesis circuit section for synthesizing the γ-corrected luminance signal and the color signal; an analog-digital converter for converting an output signal of the luminance color synthesis circuit section into a digital signal;
And a digital signal processing circuit for processing the converted digital signal and outputting the digital signal.

[0011]

According to the present invention, with the above-described structure, the output signal of the solid-state image pickup device is separated into the luminance signal and the color signal in the luminance color separation circuit section, and the luminance signal is subjected to the γ correction in the γ correction circuit to synthesize the luminance color. An analog-to-digital converter converts the output signal obtained by synthesizing the luminance and chrominance signals that have been gamma-corrected in the circuit section into a digital signal, and the digital signal processing circuit outputs the digital signal after processing it. Since the γ-correction is not applied to the color signal before digital conversion, a correct color signal can be obtained regardless of the difference in luminance value.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital video camera according to an embodiment of the present invention will be described below with reference to the drawings. 1 is a block diagram showing the configuration of a digital video camera according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing the signal waveforms in FIGS. 1A and 1B, and FIG. 3 shows the inside of the digital signal processing circuit in FIG. FIG. 4 is a waveform diagram when the output signal of the digital signal processing circuit of FIG. 2 is displayed on a vector scope, and FIG. 5 is a diagram of the luminance color separation circuit unit, the gamma correction circuit, and the luminance color synthesis circuit unit of FIG. It is a block diagram showing an example of composition.

In FIG. 1, 1 is a solid-state image pickup device, 2 is a luminance / color separation circuit section for separating an output signal of the solid-state image pickup device 1 into a luminance signal and a color signal, and 3 is a γ correction for the luminance signal. A correction circuit 4, a luminance color synthesis circuit section for synthesizing the γ-corrected luminance signal and the color signal, 5 an analog-digital converter for converting the output signal of the luminance color synthesis circuit section 4 into a digital signal, 6 Is a digital signal processing circuit for performing digital signal processing on the converted digital signal and outputting it. In FIG. 2, the horizontal axis represents time and the vertical axis represents signal voltage level. In FIG. 3, 7 is a luminance color separation circuit, and 8
Is a white balance circuit, 9 is a γ correction circuit, 10 is a matrix circuit, 11 is a luminance signal output terminal, and 12 is a color difference signal output terminal. In FIG. 5, reference numeral 2 is a luminance color separation circuit section, 3 is a γ correction circuit, 4 is a luminance color synthesis circuit section, 13 is a low pass filter, 14 is a band pass filter, and 15 is an addition circuit.

The operation of this embodiment having the above-described structure will be described. First, in the single-chip camera as shown in FIG. 1, the output signal of the solid-state image pickup device 1 is a luminance signal and a modulation component of a color signal. When the luminance signal is Y and the modulation component of the chrominance signal is C, the signal is expressed by (Y + C). For example, when the color bar is imaged, the signal of one line has a waveform as shown in FIG. 2a. The colors are arranged in the order of white, yellow, cyan, green, magenta, red, and blue from the top of the stepped waveform in FIG. The luminance / color separation circuit unit 2 separates such a signal into a luminance signal and a color signal. The luminance signal Y output from the luminance color separation circuit unit 2 is subjected to γ correction by the γ correction circuit 3,
The characteristic of the γ correction circuit 3 is that the standard level of the input signal is generally 1
Then, the signal level is obtained by the power of γ. Therefore γ
The output signal of the correction circuit 3 is represented by Y to the power of γ. The luminance color synthesis circuit unit 4 synthesizes the luminance signal subjected to the γ correction and the color signal output from the luminance color separation circuit unit 2 which is not subjected to the γ correction, and outputs the synthesized signal.

This signal is expressed by (Y to the power of γ + C), and the waveform when the color bar is imaged is as shown in FIG. 2b.
What should be noted here is that the color components of each signal represented by the AC waveform are constant regardless of whether the brightness level is high or low. This signal is converted into a digital signal by the analog-digital converter 5 and input to the digital signal processing circuit 6. In the digital signal processing circuit 6, the luminance signal and the color signal are separated in the luminance color separation circuit 7 of FIG.
The brightness signal is output from the brightness signal output terminal 11. Next, the separated color signals are subjected to white balance processing by the white balance circuit 8, and the color signals are first subjected to γ correction by the γ correction circuit 9 and input to the matrix circuit 10. The color signals input to the matrix circuit 10 are converted into color difference signals and output from the color difference signal output terminal 12.

FIG. 4 shows an output color difference signal when a color bar having different brightness is imaged and displayed on the vectorscope. Originally, the brightest signal, that is, the outermost signal on the vector scope must enter the so-called "tagata", but in Fig. 4, the outermost signal enters the so-called "tagata".

In the present embodiment, as the luminance / color separation circuit section 2, as shown in FIG. 5, the luminance separation circuit has a low-pass filter 13, the color separation circuit has a bandpass filter 14, and the luminance / color synthesis circuit section. 4 can be easily realized by using the adder circuit 15.

[0018]

As described above, according to the present invention, the output signal of the solid-state image pickup device is separated into the luminance signal and the color signal in the luminance color separation circuit section, and the γ correction circuit performs γ correction on the luminance signal. , An output signal obtained by synthesizing the luminance signal and the chrominance signal subjected to γ correction in the luminance color synthesizing circuit unit,
The analog-to-digital converter converts the signal to a digital signal, and the digital-signal processing circuit processes the digital signal to output it, so the color signal before analog-to-digital conversion is not gamma-corrected, so regardless of the difference in luminance value. The correct color signal can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a digital video camera according to an embodiment of the present invention.

2A is a waveform diagram showing a signal waveform in FIG. 1A, and FIG. 2B is a waveform diagram showing a signal waveform in FIG. 1B.

FIG. 3 is a block diagram showing the inside of the digital signal processing circuit in FIG.

FIG. 4 is a waveform diagram when the output of the digital signal processing circuit of FIG. 2 is displayed on a vectorscope.

FIG. 5 is a block diagram showing an example of a luminance color separation circuit unit, a γ correction circuit, and a luminance color synthesis circuit unit.

FIG. 6 is a block diagram showing the structure of a conventional digital camera.

7A is a waveform diagram showing a waveform of a signal in FIG. 6A when a color bar is imaged, and FIG. 7B is a waveform diagram showing a waveform of a signal in FIG. 6B when a color bar is imaged.

8 is a block diagram showing the internal processing of the digital signal processing circuit 6 of FIG.

FIG. 9 is a waveform diagram when the digital circuit output during color bar imaging is displayed on a vectorscope.

[Explanation of symbols]

 1 Solid-state image sensor 2 Luminance color separation circuit section 3 γ correction circuit 4 Luminance color synthesis circuit section 5 Analog-digital converter 6 Digital signal processing circuit 7 Luminance color separation circuit 8 White balance circuit 9 γ correction circuit 10 Matrix circuit 11 Luminance signal output Terminal 12 Color difference signal output terminal 13 Low pass filter 14 Band pass filter 15 Adder circuit

Claims (2)

[Claims] 1. A solid-state image sensor, a luminance color separation circuit section for separating an output signal of the solid-state image sensor into a luminance signal and a color signal, and a γ correction circuit for performing γ correction on the luminance signal.
A luminance color synthesis circuit section for synthesizing the γ-corrected luminance signal and the color signal; an analog-digital converter for converting an output signal of the luminance color synthesis circuit section into a digital signal;
A digital video camera, comprising: a digital signal processing circuit that processes the converted digital signal and outputs the digital signal. 2. The luminance color separation circuit section comprises a low pass filter for luminance separation and a band pass filter for color separation, and the luminance color combination circuit section comprises an addition circuit. Item 1. A digital video camera according to item 1.