JPH03218195A - Coor correcting device for reproduced chroma signal - Google Patents

Abstract

PURPOSE:To reduce the size of a circuit and to prevent an S/N ratio from being deteriorated by forming a white balance correcting signal based upon a reproduced brightness signal and adding the white balance correcting signal to a reproduced chroma signal to execute white balance correction. CONSTITUTION:The gain and polarity of a reproduced brightness signal converted into the same band as a color difference signal are individually controlled by gain control parts 14, 15, their output signals are respectively modulated by subcarriers mutually having a 90 deg. phase difference and the modulated outputs are added to each other to form a white balance correcting signal. On the other hand, burst signal forming parts 8, 22 falsely form color burst signals by controlling the phases and levels of subcarriers, a color burst signal included in a reproduced chroma signal is substituted for the burst signal by a burst signal substituting part 24, the white balance correcting signal is added to the substituted signal, and then the reproduced brightness signal is added to form a composite video signal. Consequently, color correction such as white balance correction can be executed without modulating/demodulating the reproduced chroma signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color correction device for reproduced chroma signals, and is used, for example, in video tape recorders, camera-integrated video tape recorders (video movies), and the like.

(Prior art) As a color correction device for reproduced chroma signals, the second
A circuit with the configuration shown in the figure has been proposed.

In the figure, the Y/C separation circuit 32 separates the input reproduced video signal into a luminance signal Y and a chroma signal C, and sends the luminance signal Y to the first matrix circuit 34, and also sends the chroma signal C to the first matrix circuit 34. It is sent to demodulator 33 and crystal oscillator 39. In the demodulator 33, the derived chroma signal C. from,
RY color difference signal which is a difference signal between red signal R and luminance signal Y, and B which is a difference signal between blue signal B and luminance signal Y.
-Y color difference signal and sends it to the first matrix circuit 34. Then, the first matrix circuit 34 creates a red signal R, a blue signal B, and a green signal G from the luminance signal Y, the R-Y color difference signal, and the B--Y color difference signal, and converts these color signals into white. After inputting to the balance correction circuit 35 and performing white balance correction,
the second matrix circuit 36. Then, in the second matrix circuit 36, a luminance signal Y, an R-Y color difference signal, and a B-Y color difference signal are again created from the white balance corrected red signal R, blue signal B, and green signal G. The luminance signal Y is applied to one input of the adder 38, and the R-Y color difference signal and the B-Y color difference signal are input to the chroma modulator 37, where the 3.58M signal from the crystal oscillator 39 is input.
}Iz subcarrier and then supplied to the other input of the adder 38.

The adder 38 adds the luminance signal Y and the chroma signal C, and outputs the resultant signal to a subsequent signal processing system as a decoded video signal.

(Problem to be Solved by the Invention) As described above, in the conventional color correction device, the reproduced chroma signal C is demodulated into the haphazard signal of the R-Y color difference signal and the B-Y color difference signal, and after white balance correction, the reproduced chroma signal C is demodulated again into the R -Y
Since signal processing is performed such as combining the color difference signal and the B-Y color difference signal and modulating this, there is a problem that the circuit configuration becomes large-scale. Also, since the chroma signal C passes through the demodulation circuit and the modulation circuit, the S
There was a problem that /N deteriorated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a color correction device for a reproduced chroma signal that can perform color correction such as white balance correction without modulating or demodulating the reproduced chroma signal. It's about doing.

(Means for Solving the Problems) In order to solve the above problems, the color correction device for reproduced chroma signals according to the present invention is capable of individually controlling the gain and polarity of the reproduced luminance signals converted to the same band as the color difference signals. The two types of gain control sections and the respective outputs of each gain control section are
Two types of modulators that each modulate using 3.58 MHz subcarriers having a phase difference of 90 degrees from each other, a correction signal creation section that creates a white balance correction signal by adding the outputs of each modulator, and a 3.58 MHz a burst signal creation section that artificially creates a color burst signal by controlling the phase and level of the subcarrier of the subcarrier; and a burst signal creation section that replaces the output of this burst signal creation section with the color burst signal included in the reproduced chroma signal. A configuration is adopted that includes a burst signal replacement section and an addition section that adds a white balance correction signal from the correction signal creation section to the reproduced chroma signal whose color Hurst signal has been replaced by the burst signal replacement section.

(Operation) The gain and polarity of the reproduced luminance signal converted to the same band as the color difference signal are individually controlled by two types of gain control sections.

The output signals of each of the controlled gain control sections are
A white balance correction signal is created by modulating each subcarrier with a 3.58 MHz subcarrier having a phase difference of 100 degrees, and adding the modulated outputs. On the other hand, the Hurst signal creation section creates a pseudo color Hurst signal by controlling the phase and level of the 3.58 MHz subcarrier. Then, the output of this color burst signal creation section is replaced by a color burst signal included in the reproduced chroma signal by a burst signal replacement section, and a white balance correction signal is added to the reproduced chroma signal in which this color burst signal has been replaced. At the same time, a reproduced luminance signal is added to create a decoded video signal.

That is, it is possible to perform color correction such as white balance correction without modulating or demodulating the reproduced chroma signal.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a prosochometric diagram showing the electrical configuration of a color correction device for reproduced chroma signals according to the present invention.

At the same time, the output of the demodulator 2 from which the reproduced luminance signal has been led is led to the first low-pass filter 3 that removes unnecessary Takagi components, and the output of the first low-pass filter 3 is the noise It is led to a noise removal circuit 4 that removes the component. Further, the output of the noise removal circuit 4 is transmitted to the first adder 1
1, and is also guided to a second low-pass filter 13 for matching the band of the chroma signal.

The output of the second low-pass filter 13 is processed by two types of gain control circuits 14.
It is guided by 15. The gain control circuits 14 and 15 are controlled by volumes VRI and VR2 provided respectively. Further, the output of each gain control circuit 14.15 is guided to a corresponding modulator 16.17. Then, one modulator 16 receives a reference signal of 3.58 from the crystal oscillator 8.
3. A MHz subcarrier f SCI is introduced to the other modulator l7 through a phase shifter 20.
A subcarrier r scz is derived by shifting the phase of the 58 MHz subcarrier f SCI by 90 degrees. Further, the output of each modulator 16, 17 is led to the respective input of the second adder l9, and the output of the second adder l9 is input to the first switch 21 as a white balance correction signal. The input signal is guided to one input of the third adder 26 by the input signal.

On the other hand, the output of the frequency converter 6 to which the low frequency converted reproduced chroma signal is guided is guided to a comb-shaped filter, and the output of the comb-shaped filter is sent to the burst signal replacement unit 24 via the second switch 23. and is also guided to the crystal oscillator 8.

Also, the 3.58MHz signal from the crystal oscillator 8 is the fourth
For example, 6 30 KHz is guided to one terminal of the adder 27, and the other terminal of the fourth adder
The output of the voltage controlled oscillator 9 which sends out a low frequency signal of 40 [H: in the case of VHS system] is guided, and the output of this fourth adder 27 is guided to the frequency converter 6. There is. Further, the output of the crystal oscillator 8 is guided to a phase shifter 22 whose phase and level can be controlled, and the output of the phase shifter 22 is guided to a burst signal replacement section 24. The output of the Hurst signal replacement unit 24, which sends out a reproduced chroma signal in which the color burst signal included in the reproduced chroma signal is replaced with a pseudo color burst signal from the phase shifter 22, is output from the other side of the first adder 11. is guided by the input. Further, the output of the first adder 11 is led to the other terminal of the third adder 26 via a delay circuit 25 that performs a delay for time adjustment, and the output of the third adder 26 is is transmitted as a decoded video signal in which the color correction of the chroma signal has been performed.

In other words, in conventional white balance correction, when a black and white subject is photographed, it is sufficient that the color difference signal becomes zero, so the gain control circuit is adjusted so that R-Y±αY=O, B-Y±βy=o. However, the color correction device of the present invention creates a White Halance correction signal from the reproduced luminance signal without converting this control into a color difference signal, so that the reproduced chroma signal is directly output as it is. It has been made possible to do so.

Next, the operation of the color correction device having the above configuration will be explained.

The reproduced video signal read from the recording tape is separated into a reproduced luminance signal and a reproduced chroma signal in a Y/C separation circuit (not shown). Then, the separated reproduced luminance signal is subjected to processing such as an equalizer, a limiter, FM detection, and de-emphasis in a demodulator 2, and then unnecessary Takagi components are removed in a first low-pass filter 3. , after being time-aligned with the reproduced chroma signal separated from the reproduced video signal, and then input to the noise removal circuit 4. After the noise component is removed by the noise removal circuit 4, the signal is applied to one terminal of the first adder 11 and the second low-pass filter 13.

The reproduced luminance signal input to the second low-pass filter 13 is limited to the same band as the reproduced chroma signal, and then input to each gain control circuit 14.15. After its gain and polarity are individually adjusted in 15, it is manually applied to each corresponding modulator l6, 17.

A 3.58 MHz subcarrier r sc+ serving as a reference from the crystal oscillator 8 is guided to one modulator l6,
Furthermore, since the subcarrier r scz obtained by shifting the phase of the subcarrier f SCI of 3.58 MHz by 90 degrees is guided to the other modulator 17 via the phase shifter 20 , each modulator 16 . 17, each of these subcarriers fsc
l+'SC2 modulates the signals from each gain control circuit 14, 15, and the third adder 19 adds the modulated signals to create a White Halance correction signal. This white balance correction signal is applied to one terminal of the third adder 26 via the first switch 21.

On the other hand, the low frequency converted chroma signal separated in the Y/C separation circuit is converted to 3.58 MHz in the frequency converter 6. That is, in the fourth adder 27, 3.58 MHz from the crystal oscillator 8 and 630 KHz (40 f,1: in case of VHS system) from the voltage controlled oscillator 9 are added to create 4.2 MHz. , the frequency converter 6 subtracts 630 KHz of the low frequency converted chroma signal from this 4.2 MI{z to obtain a reproduced chroma signal high-converted to 3.58 MHz.

This Takashiro-transformed reproduced chroma signal is applied to the burst signal replacement unit 24 via the second switch 23 after removing crosstalk between adjacent track patterns in a comb filter. The burst signal replacement unit 24 includes a subcarrier f sent out from the crystal oscillator 8 in the phase shifter 22.
By adjusting the level and phase of scl, a pseudo color burst signal whose color level and phase are relatively corrected is derived. The pseudo color burst signal is replaced with this pseudo color burst signal and is supplied to the other terminal of the first adder 11.

Therefore, in the first adder 11, the reproduced luminance signal and
The W-converted reproduced chroma signal is added to the pseudo color burst signal, and after being time-aligned with the white balance correction signal from the third adder 19 in the delay circuit 25, in the third adder 26, By being added to the white balance correction signal, the output is a decoded video signal that has been subjected to the replacement of the pseudo-Larhurst signal and the White Halance correction and is sent to the subsequent signal processing system. Become.

In other words, when performing white balance correction, the color correction device of the present invention creates a white balance correction signal from the reproduced luminance signal, and can directly perform the white balance correction using the reproduced chroma signal without converting it into a color difference signal. be. Further, although each of the switches 21 and 23 is normally in an ON state, by turning only the second switch 23 into an OFF state, it is possible to perform a monochrome image using a White Halance correction signal.

(Effects of the Invention) The color correction device of the present invention has a configuration that performs white balance correction by creating a white balance correction signal based on a reproduced luminance signal and adding this white balance correction signal to a reproduced chroma signal. Therefore, there is no need to modulate and demodulate the reproduced chroma signal as in conventional color correction devices, so the circuit scale can be reduced accordingly, and the S/N deterioration that occurs during modulation and demodulation can be reduced accordingly. can also be prevented. In addition, since the color burst signal included in the reproduced chroma signal is replaced with a color burst signal created suspiciously, the color burst signal is stabilized, so a high-quality reproduced image can be obtained. There is also.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the electrical configuration of a reproduced chroma signal color correction device according to the present invention, and FIG. 2 is a block diagram showing the electrical configuration of a conventional color correction device. 2... Demodulator 3... First low pass filter 4... Noise removal circuit 6... Frequency converter 7... Comb filter 8... Crystal oscillator 9... Voltage controlled oscillator 11... . . . first adder 13 . . . second low-pass filter 14 . 15... Gain control circuit 16. 17...Modulator l9...Second adder 20.22...Phase shifter 24...Burst signal replacement section 26...Third adder 27...Fourth adder

Claims (1)

[Claims] 1) Two types of gain control sections capable of individually controlling the gain and polarity of the reproduced luminance signal converted to the same band as the color difference signal; two types of modulators that each modulate with a 3.58 MHz subcarrier having a phase difference of 3.5 degrees, a correction signal creation section that adds the outputs of each modulator to create a white balance correction signal, and a 3.58 MHz subcarrier. A burst signal creation section that creates a pseudo color burst signal by controlling the phase and level of the carrier wave, and a burst signal replacement that replaces the output of this burst signal creation section with the color burst signal included in the reproduced chroma signal. and an addition section that adds a white balance correction signal from the correction signal generation section to the reproduction chroma signal whose color burst signal has been replaced by the burst signal replacement section. correction device.