JPS5919514B2 - Color stabilization device for color television receivers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color stabilizing device for a color television receiver capable of reproducing stable skin tones, and in particular, the present invention relates to a color stabilizing device for a color television receiver capable of reproducing stable skin tones. The signal is detected and the amplitude and phase of the carrier color signal are incorporated into the skin color signal based on the detection signal.

The most important thing in the color reproduction of a color television receiver is the reproduction characteristic of skin color, but this skin color is reproduced differently from the original color due to various factors.

For example, these include changes in lighting in a studio, characteristics of the three primary color filters of a television camera, characteristics of transmission lines, detection characteristics of a receiver, and nonlinear distortion of an amplifier. In order to reduce the skin color distortion caused by these factors, conventionally a circuit (such as the RCA integrated circuit CA3137) has been used that pulls a carrier color signal having a phase close to the skin color phase into the skin color phase. FIG. 1 is a block diagram showing a conventional example, and FIG. 2 is a vector diagram for explaining its operation.

To explain this, in FIG. 1, the I-axis signal generator 1
The subcarrier having the skin color phase (I-axis phase) output from the subcarrier is supplied to the phase detector 2. The phase detector 2 outputs a phase difference signal corresponding to the phase difference between the separately supplied carrier color signal and the subcarrier, and supplies it to the variable gain amplifier 3. The variable gain amplifier 3 is supplied with a carrier color signal in addition to the phase difference signal, and when the phase difference signal level is small (
In other words, the gain for the carrier color signal is increased when the carrier color signal phase approaches the skin color phase. The adder 4 is supplied with the carrier color signal whose level is controlled by the variable gain amplifier 3 and the I-axis phase subcarrier, adds both signals, and supplies the added signal to the amplitude limiter 5 . The amplitude limiter 5 limits the amplitude of the added signal to a constant value and directly supplies it to one terminal of the demodulator 7.
The signal is supplied to the other terminal of the demodulator 7 via the 0° phase shifter 6.

The demodulator 7 demodulates the separately supplied carrier color signal by referring to the phases of both signals supplied from the amplitude limiter 5 and the 90 phase shifter 6, and outputs an l signal and a Q signal. With the above configuration, when the carrier color signal phase is significantly different from the skin color phase (I-axis phase), the output of the variable gain amplifier 3 becomes zero, so the output signal of the amplitude limiter 5 is changed to the I-axis phase. When the carrier color signal phase approaches the skin color phase (I-axis phase), the carrier color signal is output from the variable gain amplifier 3 according to the proximity, and the carrier color signal becomes a sub-carrier with the I-axis phase. Because of the mixing, the output signal phase of the amplitude limiter 5 approaches the phase of the carrier color signal rather than the original I-axis phase.

Since the demodulator 7 determines the phase of the subcarrier supplied from the amplitude limiter 5 as the skin color phase (I-axis phase) and demodulates the carrier color signal, the demodulation is performed as if the phase of the carrier color signal was drawn into the skin color phase. Output a signal.

FIG. 2 is a vector diagram showing the operation. Through the above operations, colors with a hue close to skin color are drawn into the skin color hue on the screen of the receiver, so variations in skin color hue are reduced, and stable skin color reproduction can be achieved.

As described above, although the conventional structure had the effect of stabilizing the hue of skin color, it had the following drawbacks.

First, in conventional color stabilization devices, when only the phase of the carrier color signal approaches the skin tone phase, the phase height is pulled in, so even highly saturated colors with a phase close to the skin tone phase can be stabilized. Phase entrainment occurs, and as a result, highly saturated red and yellow all turn into orange, making the viewer feel uncomfortable. Second, since no saturation pull-in operation is performed, variations in the depth of skin color are not reduced, and as a result, very dark skin tones or very pale skin tones appear on the screen. The present invention aims to eliminate such drawbacks of the conventional example and provide a color stabilizing device that brings the saturation level and hue to the skin tone and prevents changes in highly saturated reds and yellows. . The present invention can be described in detail below. FIG. 3 is a block diagram of a main part of an embodiment of the present invention.

In the figure, a reference color signal generator 10 is composed of a modulator 11 and a color signal generator 12. The color signal generator 12 generates a color signal having a constant amplitude and a skin color phase, and supplies it to the modulator 11. The modulator 11 modulates the constant amplitude color signal using a separately supplied luminance signal. That is, the reference color signal generator 10 generates a large-level reference color signal in the case of a large-level luminance signal, and generates a small-level reference color signal in the case of a small-level luminance signal, thereby performing modulation. The ratio between the reference color signal amplitude and the luminance signal level output from the device 11 is maintained at a constant value. Thereby, the reference color signal output from the modulator 11 becomes a skin color reference signal for any luminance signal. A subtracter 13 subtracts the carrier color signal from the reference color signal from the reference color signal generator 10. FIG. 4 is a vector diagram for explaining the subtraction. In the same figure, is the reference color signal a vector? If the carrier color signal is expressed as a vector, then the output of the subtracter 13 can be expressed as a vector F-C.

The magnitude of the vector F-C represents the difference between the reference color signal and the carrier color signal including amplitude and phase, that is, the difference between the sent color and the skin color. The amplitude detector 14 detects the amplitude of the output → → output signal (vector FC) of the subtracter 13 and supplies the detected signal to the gain control terminal 16 a of the variable gain amplifier 16 .

When the detection signal is larger than a certain value (when the difference between the sent color and the skin color is large), the variable gain amplifier 16
The signal supplied from the subtracter 13 is not output, but when the detection signal becomes smaller than the above-mentioned constant value (when the difference between the sent color and the skin color becomes small to some extent), the signal supplied from the subtracter 13 is output to the adder 17. supply to. Adder 17 adds the signal supplied from variable gain amplifier 16 and the carrier color signal. A, B, and C in Fig. 5 are vector diagrams for explaining the operation. A represents the case where the sent color and the skin color are significantly different, and B represents the case where the two colors are relatively similar. and C indicates a case where both colors are very similar.

In FIG. 5, vector 3 is a vector representing the output signal of adder 17, and vector d is a vector representing the output signal of variable gain amplifier 16.

With the above configuration, when a color close to a skin color including hue and saturation is transmitted, that color is drawn into the skin color.

FIG. 6 is a vector diagram for making it easier to understand the effects of the embodiment of the present invention described above.

Comparing this with Figure 2, which shows the effect of the conventional color stabilizing device, the color stabilizing device of the present invention pulls in not only the hue but also the saturation. no change. Therefore, skin tones with stable density and tone are always reproduced on the screen, and it can be seen that the effect is great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main part showing a conventional example, FIG. 2 is a vector diagram showing the effect of the conventional example, FIG. 3 is a block diagram of the main part showing an embodiment of the present invention, and FIGS. 4 and 5 A, B, C
6 is a vector diagram for explaining signal processing according to the embodiment of the present invention, and FIG. 6 is a vector diagram showing the effects of the embodiment of the present invention. 6...90° phase shifter, 1...Demodulator, 10...Reference color signal generator, 11...
・Modulator, 12... Color signal generator, 13...
...Subtractor, 14...Amplitude detector, 15...
...Controller, 16...Variable gain amplifier, 1
T... Adder.

Claims (1)

[Scope of Claims] 1. A color signal transmission section of a color television receiver is provided with a reference color signal generator, a subtracter, an amplitude detector, and a controller, and the reference color signal generator is configured to transmit a reference amplitude and a reference color signal. A reference color signal having a phase is generated, the subtracter is configured to be supplied with a carrier color signal and the reference color signal and output a difference signal between the two signals, and the amplitude detector is configured to output a difference signal between the two signals. The controller is configured to receive a signal and output a detection signal corresponding to the amplitude thereof, and the controller includes a variable gain amplifier and an adder, and the variable gain amplifier outputs a detection signal corresponding to the amplitude of the detection signal and the difference signal. and is configured to control the amplification factor for the difference signal according to the level of the detected signal, and to supply the controlled signal to the adder, and the adder adds the controlled signal and the carrier color signal. A color stabilizing device for a color television receiver, characterized in that it is configured as follows. 2. The reference color signal generator includes a modulator and a color signal generator, and the color signal generator generates a color signal having a skin color phase at a certain level, and the modulator generates a color signal that has a skin color phase of a certain level, and the modulator generates a color signal that has a skin color phase of a certain level. 2. A color stabilizing device for a color television receiver according to claim 1, wherein said color stabilizing device is arranged to modulate said color signal with said luminance signal.