JPS5924231Y2 - color encoder - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a color encoder, and an object of the present invention is to provide a color encoder that shares an automatic color temperature correction circuit and an automatic carrier balance circuit, and whose circuit can be made compact.

FIGS. 1 and 2 show block diagrams of an embodiment of an automatic color temperature correction circuit and an automatic carrier balance circuit, respectively, of a conventional color television camera.

In Fig. 1, the input terminal 1°2 is taken out from the image pickup tube.
．． The red color voltage ER1, the green color voltage E6, and the blue color voltage EB input from 3 are supplied to the voltage comparators 6 and 7 and compared with the reference color voltage E6, and the difference voltage is applied to the switches 8 and 9.
, negative feedback is provided to variable gain amplifiers 4 and 5 via voltage holding (memory) devices 10 and 11, so that the ratio of each color voltage is 1:1:
The gains of amplifiers 4 and 5 are automatically adjusted so that
white balance adjustment), when automatic adjustment is completed, open switches 8 and 9 to disconnect the feedback loop, and voltage holder 10
．． The control voltage is held at 11.

Each color voltage E'R, Ec, E held in this way
's is calculated by the linear matrix circuit 12, and the color difference signal EB is output from the output terminals 13, 14, and 15.

Ec-y, EB-Y, and output terminals 32 output the luminance signal EY.

On the other hand, in FIG. 2, the carrier signal input to the input terminal 16 and the signal obtained by shifting the carrier wave signal by 90° in the 90° phase circuit 17 are transferred to a third carrier signal having a modulation axis R-Y and a modulation axis B-Y, respectively. Balanced modulator 18 constituted by a ring modulator as shown in the figure.
．． 19, which are amplitude-modulated by the color difference signal ER-y and the color difference signal EBY that come in from the input terminals 20 and 21, and are combined in the combiner 22, and then combined with the burst signal that comes in from the input terminal 23 and the combiner. 24 and output terminal 2.
Taken from 5.

At this time, the modulated signals synthesized by the synthesizer 22 are sent to the synchronous detectors 28, 28, and 28 via the gate circuits 27, which are opened by the signals input from the input terminals 26 during the horizontal blanking period.
29 (that is, a leakage component is detected during the blanking period) and is synchronously detected by the phase of the carrier signal from the input terminal 16, smoothed by a low-pass filter 30, 31, and then balanced by the balanced modulator 18. Negative feedback is given to .19 to automatically adjust the balance.

However, as shown in FIGS. 1 and 2, in this conventional color encoder, the automatic color temperature correction circuit and the automatic carrier balance circuit are each configured as independent circuits, so the circuit becomes large and large. The drawback is that it requires space and is particularly unsuitable for small color television cameras.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described below with reference to FIG. 4.

FIG. 4 shows a circuit diagram of an embodiment of the color encoder according to the present invention, in which parts having the same functions as those in FIGS. 1 and 2 are given the same numbers.

In the figure, the carrier wave signal entering the input terminal 16 is
Similar to the conventional circuit shown in FIG. After being amplitude-modulated by the color difference signals ER and EBY, which are combined in a combiner 22, a burst signal is added in a combiner 24 and taken out from an output terminal 25.

The modulated signals synthesized by the synthesizer 22 are respectively supplied to synchronous detectors 28 and 29, where they are synchronously detected by the phase of the carrier signal from the input terminal 16, and the switches 8 and 9 and voltage holders 10 and 11 are synchronously detected. Negative feedback is provided to the variable gain amplifiers 4' and 5' via the signal, thereby making the gains of the amplifiers 4' and 5' variable, respectively.

Let us now consider the relationship between the color difference signals ER and EBY extracted from the linear matrix circuit 12 and the white balance.

The color difference signals ERY and EB are then provided with a negative feedback system so as to vary the gains of the variable gain amplifiers 4' and 5' so that both the color difference signals ERY and EB taken out from the linear matrix circuit 12 become zero. If configured, ER2EG=
Each color voltage E'R, EG, and E'B can be automatically adjusted as shown in E8.

When the automatic white balance adjustment is completed, the switches 8 and 9 are opened to remove the negative feedback loop, and the voltage holders 10 and 11 hold the control voltage.

On the other hand, the signals synchronously detected by the phase of the carrier signal in the synchronous detectors 28 and 29 are passed through gate circuits 27a and 27b which are opened by the signal input from the input terminal 26 during the horizontal blanking period. low pass filter 30.3
1 (that is, the leakage component is detected during the blanking period), the signal is smoothed, and is negatively fed back to the balance modulators 18 and 19 to automatically adjust the balance thereof.

As described above, the color encoder according to the present invention is provided with a color temperature correction circuit that balances color signals by varying the gain of a variable gain amplifier, and when white balance is performed, the color difference signals ER and E are adjusted.
Since the gain of the variable gain amplifier is controlled by the synchronous detection output used to adjust the balance of the automatic carrier balancing circuit so that both BY becomes zero, the synchronous detection output used to adjust the balance of the balanced modulator can be directly used. It can be used as a control signal for white balance adjustment, and therefore the automatic color temperature correction circuit and the automatic carrier balance circuit can be used in common, and for example, the voltage comparator used in the conventional automatic color temperature correction circuit can be omitted. The circuit can be easily and compactly configured, requiring only a small space, and is especially suitable for small color television cameras.Also, since there is no need for a voltage comparator, there is no need to align the zero level, making it easy to handle. It has features such as being easy to use.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams of examples of conventional automatic color temperature correction circuits and automatic carrier balance circuits, respectively, and FIG. 3 is a specific circuit diagram of a circuit that performs balanced modulation of the balanced modulator shown in FIG. 2. ,
FIG. 4 is a circuit diagram of an embodiment of the color encoder according to the present invention. 1~3...Color signal input terminal, 4', 5'...
... Variable gain amplifier, 10.11 ... Voltage holder, 12 ... Linear matrix circuit, 16.
...Carrier wave input terminal, 18.19...Balanced modulator, 22...Synthesizer, 25...
Carrier color signal output terminal, 26... gate signal input terminal, 27 a, 27 b... blanking period gate circuit, 28, 29... synchronous detection circuit.

Claims (1)

[Scope of utility model registration request] Automatic carrier balancing that performs amplitude balanced modulation of the color subcarrier signal with the color difference signals EB-Y and EB-Y, and during the modulation, performs synchronous detection of the modulated output and returns the obtained synchronous detection output to the balanced modulator to adjust the balance. A color encoder having a circuit is provided with a color temperature correction circuit that is supplied with color signals ER, Eo, and E and adjusts the gain of a variable gain amplifier to balance each color signal, and when correcting the color temperature, the color difference is A color encoder comprising a circuit for controlling the gain of the variable gain amplifier using the synchronous detection output so that both the signal EBa and the color difference signal E8a become zero.