JPS6132874B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In order to stably reproduce a specific color, for example, skin tone, the present invention detects a difference signal between a reference color signal and a carrier color signal of the specific color, and uses the amplitude value of this difference signal to reproduce a carrier color signal. The present invention relates to a color stabilizing device for a color television receiver or the like configured to control the mixing ratio of a color signal and a skin color reference color signal.

The colors reproduced by color television receivers are often reproduced in colors that differ from the original colors due to differences in lighting at the broadcast station, differences in transmitting equipment, or differences in relay equipment. This is one of the causes of deterioration in the quality of reproduced images. In particular, distortion in color reproduction of skin tones is visually sensitive, and various methods for correction centered on skin tones have been studied.

One of the conventional examples is shown in FIG. In FIG. 1, the amplification factor of the carrier color signal 6 applied to the variable gain amplifier 1 is lowered by the luminance signal 8 on which the carrier color signal is superimposed when the luminance is high.
When the luminance is low, the amplification factor is increased and the signal 9 is output as a signal representing the chromaticity point in the reproduced color of the carrier color signal regardless of the difference in luminance. This output signal 9 and the reference color signal 7 having a phase and amplitude corresponding to the skin color are applied to a subtraction circuit 2, and subtraction is performed on both the amplitude and phase components.
In the subtraction circuit 2, if the signal 9 is equal to the reference color signal in both phase and amplitude, the output signal 10 will have zero amplitude, if the phases match, the difference in amplitude will be calculated, and if the phases are opposite, the output signal 10 will have zero amplitude. A sum calculation is performed, and when the phase approaches the skin color, the subtracted output 10 becomes small. The amplitude detector 3 envelope-detects the amplitude of the difference signal 10 and outputs a control signal 1 for controlling the mixer 5.
Set to 1.

On the other hand, the amplification factor of the reference color signal 7 applied to the variable gain amplifier 4 is increased by the luminance signal 8 when the luminance is high, and is lowered when the luminance is low, so that the mixing circuit 5, the skin color output 3 having a constant chromaticity point is controlled and output. The mixing circuit 5 mixes the reference color signal 12 controlled by luminance with the carrier color signal 6 when the amplitude of the control signal 11 falls below a certain value, and draws the carrier color signal around the reference color signal. This achieves stabilization of the conveyed color signal.

This conventional method has pull-in characteristics in both the phase direction and color saturation direction, and is highly effective from the perspective of stabilizing skin tone, but it does not pull light-toned lipstick into skin tone or brighten it. It has the disadvantage of adding more saturation than necessary to the skin tone, which erases the subtle nuances of the skin tone.

Therefore, in the mixing circuit, the present invention not only controls the amplitude of the reference color signal to be mixed using the luminance component, but also controls the amplitude of the reference color signal with a large amplitude when the saturation level is high. By mixing signals and, when the degree of saturation is low, mixing a reference color signal with a small amplitude, a stabilizing device is realized which solves the above-mentioned drawbacks of the conventional method.

The structure of an embodiment of the present invention is shown in FIG. 2, and FIGS. 3A and 3B show the stabilizing characteristics of the conventional structure, the structure of this embodiment, and the conventional structure. The difference from the conventional device is the addition of an amplitude detector 14 for the carrier color signal (encircled by a dashed line in FIG. 2) and a variable gain amplifier 15 that changes the magnitude of the reference color signal depending on the degree of color saturation. be.

The reference color signal 7 is applied to the variable gain amplifier 4;
When the amplitude of the luminance signal 8 is large, the amplification factor is increased, and when the amplitude is small, the amplification factor is reduced. As a result, the reference color signal 12 is modulated in proportion to the luminance, so that even if the luminance changes, the chromaticity point of the reference color signal to be mixed does not change. An amplitude detector 14 performs envelope detection on the carrier color signal 6 to obtain a control signal 16 proportional to the magnitude of the carrier color signal. The signal 12 modulated by luminance is applied to a variable gain amplifier 15, and when the amplitude of the carrier color signal 6 is large, the amplification factor is increased by a control signal 16 to increase the amplification factor of the reference color signal mixed in the mixer 5. The amplitude is controlled to be proportional to the saturation of the carrier color signals being mixed.

That is, in the case of the conventional example as shown in FIG. 3A, the same chromaticity point (amplitude) standard is used for the carrier color signal 19 with a high degree of saturation and the carrier color signal 21 with a low degree of saturation. The color signals 20 are mixed, and the combined signals 19 and 21 are subjected to pulling operations shown by arrows 22 and 23, respectively.

On the other hand, in the method of this apparatus shown in FIG. 3B, a reference color signal 24 with a large amplitude is mixed with a carrier color signal 19 with a high degree of saturation, and a reference color signal 24 with a large amplitude is mixed with a carrier color signal 21 with a low degree of saturation. mixes the reference color signal 25 with small amplitude. As a result, each arrow 2
6 and 27, and the above-mentioned conventional drawbacks are greatly improved.

By changing the gain of the variable gain amplifier 15 and the offset, that is, the always constant addition amount, the ratio of modulation of the reference color signal amplitude by the carrier color signal amplitude can be freely changed. This makes it possible to satisfy both the conditions of stabilizing the color and preserving the subtle nuances of skin color.

In addition, in FIG. 2, two variable gain amplifiers 4,
15, but it is also possible to add the signals 8 and 6 in advance and use one variable gain amplifier.

Furthermore, in contrast to the method shown in FIG. 1, a method has already been proposed in which the phase of the carrier color signal 6 is added to the reference color signal 7 to widen the color stabilization range. In this way, even with a method with a widened stabilization range, the present invention's function of modulating the amplitude of the reference color signal to be mixed with the carrier color signal amplitude can correct the nuance in the direction of saturation of the drawn color. It can be played back without any damage.

FIG. 4 shows a color stabilization device that has a widened color stabilization range, and which implements the present invention so that the amplitude of the reference color signal is controlled not only by the luminance signal but also by the amplitude of the carrier color signal. The block diagram of one Example is shown. The addition circuit 28 adds the constant amplitude reference color signal 7 to the reference color signal 7.
After making the amplitude of the carrier color signal 6 constant, the phase and amplitude are added. If this operation is shown on a Bertol diagram, it will be as shown in FIG. 5, and the result of adding the carrier color signal 36 with a constant amplitude to the reference color signal 37 becomes a vector moving on a circle 35. When this is added to the amplitude limiter 29 in FIG. 4, the circle 35 becomes 3 in FIG.
8, and a new reference color signal whose phase is changed according to the phase of the carrier color signal is obtained. As a result, if a certain carrier color signal is signal 39 in FIG. The stabilization range can be expanded from circle 44 to circle 45.

Even if the pull-in range is widened in this way, the method has the same drawbacks as the method shown in FIG. 1 because the reference color signal to be mixed is controlled only by the luminance signal and the reference color signal of a fixed chromaticity point is added. Therefore, as explained in FIG. 2, by controlling the reference color signal not only by the luminance signal but also by the amplitude of the carrier color signal, it is possible to stabilize the color while maintaining the color nuance. .

Colors can be stabilized by changing the mixing ratio of the carrier color signal and reference color signal depending on the vector difference between the carrier color signal and the reference color signal, but it is possible to subtly change the mixing ratio by changing the vector difference. Control requires high accuracy due to the circuit configuration, which may be difficult to achieve. On the other hand, if a circuit with low precision is set to perform sufficient pull-in, there will be a region where all the carrier color signals are replaced with the reference color signals, which will be a major cause of loss of color nuance. Therefore, by controlling the mixing ratio based on the vector difference between the carrier color signal and the reference color signal, and then always mixing a constant proportion of the carrier color signal, it is possible to prevent the reproduced color signal from concentrating on one point, and to improve the Natural color stabilization is possible. FIG. 7 shows the configuration of the color stabilizing device according to the embodiment. 46 is a mixer for mixing a certain proportion of the carrier color signals.

As described above, according to the present invention, it is possible to obtain a useful device that can stabilize reproduced colors while maintaining their subtle nuances.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional color stabilizing device, Fig. 2 is a block diagram of a color stabilizing device according to an embodiment of the present invention, and Fig. 3 A and B are a conventional color stabilizing device and a color stabilizing device according to the present invention. A vector diagram showing the color stabilizing operation by the color stabilizing device, FIG. 4 is a block diagram of the color stabilizing device in another embodiment of the present invention, and FIGS. 5 and 6 show the operation of the device in FIG. 4. The vector diagram shown in FIG. 7 is a block diagram of a color stabilizing device in yet another embodiment of the present invention. 1...Variable gain amplifier, 2...Subtractor, 3...
Amplitude detector, 4... Variable gain amplifier, 5... Mixer, 14... Amplitude detector, 15... Variable gain amplifier, 28... Adder, 29... Amplitude limiter, 46
...Mixer.

Claims (1)

[Claims] 1. A variable gain amplifier that controls the amplitude of the input carrier color signal by controlling its amplification factor to be small when the luminance signal is large; a reference color signal of a predetermined amplitude; A circuit that detects the difference signal in phase and amplitude from the output, and if the amplitude of the difference signal is within a certain range, the carrier color signal is considered to be within the pull-in range to the reference color signal and the reference color is controlled in amplitude. a circuit that stabilizes the carrier color signal by mixing the signal and the carrier color signal so that the carrier color signal approaches the chromaticity point of the reference color signal;
Color stabilization characterized by comprising a circuit that controls the amplitude of the reference color signal mixed with the carrier color signal in proportion to the amplitude of the luminance signal to which the carrier color signal belongs, and also in proportion to the amplitude of the carrier color signal. Device. 2. Claim No. 2 characterized in that the circuit for creating a reference color signal of a predetermined amplitude is constituted by an adding circuit for adding the reference color signal and a carrier color signal, and an amplitude limiting circuit for limiting the amplitude. The color stabilizing device according to item 1. 3. A patent claim characterized in that the circuit for stabilizing the carrier color signal is constituted by a circuit that always adds a fixed percentage of the carrier color signal to a mixture of the amplitude-controlled reference color signal and the carrier color signal. The color stabilizing device according to item 1 or 2.