JPH03167994A - White balance device - Google Patents

Abstract

PURPOSE:To attain white balance correction with less signal deterioration by adjusting a 1st subcarrier signal and a 2nd subcarrier signal to a proper level at positive or negative polarity, adding the result to a modulation chroma signal and adjusting the white balance. CONSTITUTION:A 1st control section 8 adjusts the level in positive and negative polarity by adjusting a 1st variable resistor VR1 with respect to a 1st subcarrier signal (I axis signal) to be led. Moreover, a 2nd control section 9 adjusts the level tn positive and negative polarity by adjusting a 2nd variable resistor VR2 with respect to a 2nd subcarrier signal (Q axis signal) to be led. Since the I axis signal and the Q axis signal adjusted in this way are respectively led to 1st and 2nd adders 1, 2, the I axis signal is added to a modulated chroma signal inputted to the 1st adder 1 and the Q axis signal is added to the modulation chroma signal inputted to the 2nd adder 2 to adjust the white balance (the white level is moved to the center).

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a white balance device, which can be used in color video cameras, video tape recorders for recording, playing back, or editing video signals, and various editing devices. .

(Prior art) In general, in color video cameras, etc., when the illumination light of a subject changes, it is necessary to adjust the white balance to follow the change so that a white subject is reproduced as white on the monitor. .

FIG. 4 shows an example of the electrical structure of a conventional white balance device for such a color video camera or the like.

This white balance device has a structure that first demodulates the input modulated chroma signal into a color difference signal, adjusts the white balance by performing offset correction on the color difference signal, and then modulates it again with a subcarrier. ing.

That is, the input modulated chroma signal is sent to the B-Y axis demodulator 21, which creates a B-Y signal, which is a difference signal indicating the difference between the blue signal and the luminance signal, and the BY-axis demodulator 21, which indicates the difference between the red signal and the luminance signal. The output of the B-Y axis demodulator 21 is input to one input of the adder 28, and the R-Y axis demodulator 22 generates an RY signal which is a differential signal. The outputs of the demodulators 22 are each led to one input of an adder 29.

The output of a control section 27 that controls the offset of each color difference signal to be zero is led to the other manual input of each adder 28, 29. The control unit 27 includes a transistor Qll whose collector is connected to the power supply voltage ycc through a resistor, whose emitter is connected to ground through a resistor, and whose base is given a blanking pulse, and the collector of the transistor Qll. A first volume VRII and a second volume VR1 connected in parallel between the
2, the sliding terminal of the first volume VRII is connected to the other input of the adder 28, and the sliding terminal of the second volume VR12 is connected to the other input of the adder 29. There is. The output of each adder 28, 29 is outputted to a corresponding B-Y axis modulator 30.
and R-Y axis modulator 31, each B-Y axis modulator 3
The output of the 0,RY axis modulator 31 is led to each input of an adder 32.

On the other hand, the modulated chroma signal is also guided to one input of the phase comparator 23. The phase comparator 23 extracts a burst signal from the modulated chroma signal using a burst gate pulse, and compares this burst signal with a signal from a voltage controlled crystal oscillator (VCXO) 24 to achieve phase synchronization. As a result, the voltage controlled crystal oscillator 24 sends out a color subcarrier signal which is a 3.58 MHz continuous wave phase-locked to the burst signal. This color subcarrier signal is passed through a first phase shifter 2 having a predetermined phase (θ).
5, and here, as the first subcarrier signal with an angle θ with respect to the burst signal, the B-Y axis demodulator 2
1 and B-Y axis modulator 30, and 90°
is guided to a second phase shifter 26 having a phase of . Then, the output of the second phase shifter 26 is output as a second subcarrier signal having a phase of 90'' with respect to the first subcarrier signal, and is output to the R-Y axis demodulator 22 and the R-Y axis modulator. 31. That is, the modulated chroma signal input to the BY axis demodulator 2l is demodulated into a BY color difference signal by the first subcarrier signal from the first phase shifter 25, It is input to the adder 28. Since the white balance deviation of the B-Y color difference signal at this time appears as an offset, the user can adjust the voltage applied to the base of the transistor Q11 by adjusting the first volume VRII. The ranking pulse is given as positive or reverse polarity to the other input of the adder 28. As a result, the output of the adder 28 is a B-Y color difference signal on which white balance correction has been performed with the offset set to zero. Therefore, in the B-Y axis modulator 30,
The first subcarrier signal from the first phase shifter 25 is modulated by this BY color difference signal and then sent to one input of the adder 32. On the other hand, the modulated chroma signal input to the R-Y axis demodulator 22 is demodulated into an R-Y color difference signal by the second subcarrier signal from the second phase shifter 26, and is input to the adder 29. Since the white balance deviation of the R-Y color difference signal at this time appears as an offset, the user can change the blanking pulse applied to the base of the transistor Qll to positive or reverse polarity by adjusting the second volume VR12. is given to the other input of the adder 29 as . As a result, the output of the adder 29 is the R-Y color difference signal that has been subjected to white balance correction with the offset set to zero. The second subcarrier signal of R
-Y color difference signal and then sent to the other input of the adder 32.

Then, by mixing both modulated signals in an adder 32, the modulated chroma signal is sent to a subsequent signal processing system.

(Problems to be Solved by the Invention) However, the conventional white balance device described above requires a circuit that demodulates and modulates two types of signals, the B-Y color difference signal and the R-Y color difference signal. There were problems in that the number of circuit components increased and it also hindered miniaturization. There is also a problem that demodulation and modulation cause signal deterioration (that is, a decrease in S/N, a decrease in bandwidth, an increase in hue error, etc.).

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a white balance device that can adjust white balance without demodulating and modulating two types of color difference signals.

(Means for Solving the Problems) In order to solve the above problems, the white balance device of the present invention creates a color subcarrier signal that is a continuous wave whose phase is synchronized with a burst signal included in an input modulated chroma signal. a color subcarrier signal generation unit that generates a color subcarrier signal, and a phase shifter unit that generates a first subcarrier signal and a second subcarrier signal having different phases based on the color subcarrier signal generated by the color subcarrier signal generation unit. , a level adjustment section that adjusts the first subcarrier signal and the second subcarrier signal created by the phase shifter section to appropriate levels with positive polarity or reverse polarity; A structure including an addition section that adds a correction vector based on the first subcarrier signal and the second subcarrier signal to the modulated chroma signal is adopted.

(Operation) The color subcarrier signal creation section creates a color subcarrier signal that is a continuous wave that is phase-synchronized with the burst signal included in the manually generated modulated chroma signal. This color subcarrier signal generation section is composed of a phase comparator to which a burst gate pulse is introduced and a voltage controlled crystal oscillator.

Then, based on the color subcarrier signal created by the color subcarrier signal creation section, a first subcarrier signal and a second subcarrier signal having different phases are created in a phase shifter section. The first subcarrier signal is, for example, an I-axis signal having a phase of 33° relative to the burst, and the second subcarrier signal is, for example, a Q-axis signal having a phase of 1236 relative to the burst. However, it is not always necessary to set this phase difference and it may be set arbitrarily.

The first subcarrier signal and the second subcarrier signal thus created by the phase shifter section are adjusted to appropriate levels with positive or reverse polarity by the level adjustment section.

Then, by adding a correction vector based on the level-adjusted first subcarrier signal and second subcarrier signal to the modulated chroma signal, white balance correction is performed by vector aggregation.

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

FIG. 1 is a block diagram showing the electrical structure of the white balance device of the present invention.

In the figure, the input modulated chroma signal is guided to one input of the first adder 1, and the phase comparator 3
is guided by one input. Further, the output of the first adder 1 is led to one input of the second adder 2,
The output of the second adder 2 is sent to a subsequent signal processing system (not shown).

Further, the output of the first control section 8 is led to the other input of the first adder 1, and the output of the second control section 9 is led to the other input of the second adder 2. is being guided.

On the other hand, the phase comparator 3 extracts a burst signal from the modulated chroma signal using a burst gate pulse,
This burst signal is compared with the signal from the voltage controlled crystal oscillator 4 to achieve phase synchronization.

Thereby, the voltage controlled crystal oscillator 4 sends out a color subcarrier signal which is a 3.58 MHz continuous wave phase-locked to the burst signal. This color subcarrier signal is guided to a planking circuit 5 controlled by a planking pulse, and the output of the planking circuit 5 is sent to a first phase shifter 6 having a predetermined phase θ (for example, 33°). I am guided by. Then, the output of the first phase shifter 6 is output to the first control unit 8 as a first subcarrier signal (I-axis signal) having an angle of θ (33'') with respect to the burst signal. It is sent to the base of the transistor Q1 and is also guided to a second phase shifter 7 having a phase of 90 degrees.The output of the second phase shifter 7 has a phase shift of 90 degrees with respect to the first subcarrier signal. The second subcarrier signal (Q-axis signal) having a phase of `` is sent to the base of the transistor Q2 that constitutes the second control section 9.

The first control unit 8 has a collector connected to a power supply voltage V via a resistor.
cc, the transistor Q1 is connected to the ground through a resistor, and the output of the first phase shifter 6 is led to the base, and this transistor Q
The first volume VRI is connected between the first collector emitter and the first volume VRI.
The sliding terminal of is connected to the other input of the first adder 1. In addition, the second control unit 9 has a collector connected to the power supply voltage Vcc via a resistor, an emitter connected to the ground via a resistor, and a base connected to the output of the second phase shifter 7. A second transistor connected between the transistor Q2 and the collector terminal of the transistor Q2.
The sliding terminal of the second volume VR2 is connected to the other input of the second adder 2.

Next, the operation of the white balance device having the above configuration will be explained as follows.
This will be explained with reference to the signal waveform diagram of each part shown in the figure and the vector display diagram of each of the above-mentioned signals shown in FIG. However, FIG. 3 shows the vectors of each signal when the burst signal is aligned with the left horizontal line.

Suppose now that the white portion of the input modulated chroma signal [FIG. 2(a)] is shifted from the center by a vector OA as shown in FIG. 3(a). This modulated chroma signal is input to the first adder 1 with the white balance shifted, and is also input to the phase comparator 3. The phase comparator 3 extracts a burst signal from the modulated chroma signal using a burst gate pulse (see FIG. 2(b)), compares this burst signal with the signal from the voltage-controlled crystal oscillator 4, and determines the phase. Synchronize. As a result, the voltage controlled crystal oscillator 4 has a 3.58 MHz phase locked to the burst signal.
A color subcarrier signal that is a continuous wave of MHz is transmitted. This color subcarrier signal is subjected to planking by a planking pulse [FIG. 2(C)] in a planking circuit 5, and then guided to a first phase shifter 6 having a predetermined phase (θ). Here, the first subcarrier signal having an angle of θ with respect to the burst signal [engine axis signal:
As shown in FIG. 2(d), the light is guided to the base of the transistor Q1 that controls the first control section 8, and is also guided to the second phase shifter 7 having a phase of 90°. The output of the second phase shifter 7 is a blown second subcarrier signal [Q-axis signal: Fig. 2 (e)] having a phase of 90° with respect to the ■-axis signal.
It is guided to the base of the transistor Q2 which controls the second control section 9.

The first control unit 8 controls the first
By adjusting the volume VRI of the signal, its level is adjusted in positive/reverse polarity, resulting in a -axis signal having the magnitude and direction shown by the vector OC in FIG. 3(b). Also, the second
The control unit 9 adjusts the level of the guided Q-axis signal by adjusting the second volume VR2.
Adjustments are made with opposite polarity to produce a Q-axis signal having the magnitude and direction shown by the vector ○D in FIG. 3('b). That is, the resultant vector (correction vector) OR of the vector OC and the vector ○D is adjusted so that it becomes a vector that is the same in size and opposite in direction to the vector OA indicating the deviation of the white part. Since the thus adjusted ■-axis signal and Q-axis signal are guided to the first adder 1 and the second adder 2, respectively, the modulated chroma signal input to the first adder 1 This ■
The axis signal is added, and then this Q-axis signal is added to the modulated chroma signal input to the second adder 2, and the white balance is adjusted (the white part is moved to the center), as shown in Fig. 2(f).
The modulated chroma signal shown in FIG. 1 with no white balance shift is sent from the output of the second adder 2 to a subsequent signal processing system (not shown).

In this manner, the white balance device of the present invention handles the modulated chroma signal as it is, thereby preventing signal deterioration, and since there is no need to perform demodulation or modulation, the number of circuit components can be reduced.

In the above embodiment, the ■-axis signal and the Q-axis signal are used as two types of subcarrier signals with different phases, but the ■-axis and the Q-axis do not necessarily have to match, and can be set arbitrarily. be. Also, the phase of the second phase shifter 7 is set to 9.0"
Therefore, the phase difference between the two types of subcarrier signals is 90°, but it is not limited to 90@ and can be set arbitrarily.

(Effects of the Invention) The white balance device of the present invention creates a color subcarrier signal that is phase-synchronized with a berth leaf signal, and fills this color subcarrier signal with a first subcarrier signal and a second subcarrier signal having different phases. The first subcarrier signal and the second subcarrier signal are adjusted to appropriate levels with positive or reverse polarity and added to the modulated chroma signal to adjust the white balance. Since the modulated chroma signal is handled as is, white balance correction with less signal deterioration is possible. Additionally, it requires fewer circuit components than conventional white balance devices that perform demodulation and modulation.
Manufacturing costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the electrical structure of the white balance device of the present invention, FIG. 2 is a signal waveform diagram of each part of the device, and FIG. 3 is a vector representation diagram of each signal shown in FIG. Fourth
The figure is a block diagram showing an example of the electrical configuration of a conventional white balance device. ...First adder...Second adder...Phase comparator...Voltage controlled crystal oscillator...Planking circuit...First phase shifter...Second phase Device...First control part...Second control part 2nd part (b) Hurst Tate Halsu' L1111111 (d) ■ Axis signal (e) Q axis signal,' ko3

Claims (1)

[Claims] 1) A color subcarrier signal creation section that creates a color subcarrier signal that is a continuous wave phase-synchronized with a burst signal included in an input modulated chroma signal; and the color subcarrier signal creation section. a phase shifter unit that creates a first subcarrier signal and a second subcarrier signal having different phases based on the color subcarrier signal created by the color subcarrier signal; and a first subcarrier signal created by the phase shifter unit. and a level adjustment unit that adjusts the second subcarrier signal to an appropriate level with positive polarity or reverse polarity, and a correction vector based on the first subcarrier signal and the second subcarrier signal whose levels have been adjusted by the level adjustment unit. A white balance device comprising: an adder that adds to the modulated chroma signal.