JPS6157193A - Dynamic color amending circuit - Google Patents

Abstract

PURPOSE:To see a white color beautifully by obtaining an amended output having 0 level during the time of skin color and amending a color signal of a specific channel among R, G, B channels by the amended output. CONSTITUTION:A TV signal is converted into red to blue signals SR-SB by a processor 3, fed to cathodes 6R-6B corresponding to a CRT 4 through resistances 7R-7B and also to a dynamic color amending circuit 10. Since an output from the circuit 10 is subtracted from a white color detecting output EW to a skin color detecting output ES in a subtracter 14, the amended output EP is maximum during a time of white, reduced in level according to moving from the white color to the skin color, and becomes O during a time of skin color. The output EO is fed to adders 8R, 8G through amended volumes VG, VB. When a white color signal is fed, signal levels R, G channels are subtracted by the output EO and only a signal SB is strengthened to see white visually beautifully.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dynamic color correction circuit that is used in television receivers and the like and is capable of correcting images so that white appears visually clear.

[Conventional technology]

It is well known that when there is white in a television image, increasing the color temperature to make it a slightly bluish white makes the white visually more beautiful.

In this way, a dynamic color correction circuit aω as shown in FIG. 6 is used to correct the white component on the image sending side to provide a visually preferable color.

In FIG. 6, the television signal Sv supplied to the terminal (2) is supplied to the video processor (3) and converted into primary color signals SR-SR, and these primary color signals Sl? -S
R (its level is ER and EB) is the receiver (CRT) (
4) is supplied to the corresponding cathodes 6R to 6B. Dynamic color correction circuit QOI for R and G channels
is provided to perform specific color corrections.

The dynamic color correction circuit (UO) has non-linear circuits (5R) and (5G) provided in each channel, and the non-linear circuit (5R) has a non-linear circuit (5R) which has a non-linear circuit (5R) which has a non-linear circuit (5R) which has a non-linear circuit (5R) which has a non-linear circuit (5R). It is selected so that its input/output characteristics are nonlinear from the input level. In addition, other nonlinear circuits (5G) also have a level L as shown by the curve LG.
It is selected so that it becomes nonlinear when the input level is equal to or higher than a.

Therefore, at an input level higher than the current level La, each level of the R and G channels is suppressed, whereas the input level itself is output for the B channel level, so the blue signal SB is higher than the red and green signals SR and SG. Since the image is supplied to the CRT (4) in an enhanced state, the color temperature increases and the image is reproduced as a bluish white. For this reason, the white color visually appears beautiful.

[Problem that the invention seeks to solve]

Now, with the dynamic color correction circuit αω configured as described above, although it is possible to correct white color so that it looks visually beautiful, even colors other than white are corrected according to the characteristics shown in FIG. The following problems arise.

That is, the level La is set at a relatively low level even in terms of the white level. On the other hand, when skin color has a relatively high level, it has a level near level La, so
As a result of this level of skin color sensitivity, the skin color becomes bluish, which is not a very desirable color correction.

It is possible to set the level La low so that the skin tone does not have a bluish tinge, but this would also correct many colors other than white, so this is not an effective solution. .

This invention solves these problems,
This makes it possible to visually make white look beautiful, and also prevents color correction, that is, color temperature correction, from being performed for skin tones.

[Means for solving problems]

Therefore, in this invention, in order to solve the above problems,
As shown in FIG. 1, a white detection means (IOA) that can mainly detect white components and a skin color detection means (10B') that can mainly detect skin color components are provided. Signals SR-Sa are supplied.

Then, the white detection output E- obtained from the white detection means (IOA) and the skin color detection output BS obtained from the skin color detection means (IOB') are supplied to a subtractor (14), and when the color is white, the white color detection output BS is at most shifted from white Accordingly, the level thereof decreases accordingly, and a correction output EO is formed whose level becomes zero for skin color. This correction output EO corrects the color signal of a specific channel among the R, G, and B channels, in the example of FIG. 1, the R and G channels.

[Effect]

As shown in Fig. 4, the correction output EO is at its maximum when the color is white, and decreases as the color deviates from white, and becomes zero when the color is dark skin, so when a white signal is input, it is corrected to a bluish white as before. In addition, when a skin color signal is input, no correction is made at all, so the inconvenient color correction unlike the conventional method is not performed.

〔Example〕

FIG. 1 shows a dynamic color correction circuit α according to the present invention.
This shows an example of ω, and terminals (2R) to -(2B)
The television signal sv supplied to the video processor (3) is converted into red to blue signals 5R-3B, and these are connected to the C through resistors (7R) to (7B).
These red to blue signals sR-sB are supplied to the corresponding cathodes 6R to 6B of RT (4), and further supplied to the dynamic color correction circuit αl.

As shown in the figure, the dynamic color correction circuit αω is composed of white and milky color detection means (IOA), (10B) and a subtractor (14), and a white color detection means (104).
In this example, a minimum value calculation circuit is used. The skin color detection means (10B) includes coefficient means (IIR') to (1iB) provided for each channel and a minimum value calculation circuit (12
).

The minimum value calculation circuit (IOA) (12) has a PNP type transistor QrxQb with common emitter and collector as shown in Fig. 2, and has a red to blue signal 5R at each base.
-5R is supplied to the output terminal 01 from its common emitter.
1T is derived.

Since the transistor QrxQb turns on only the transistor to which the minimum level signal among the red to blue signals SR-SR is supplied, the minimum level signal among the red to blue signals SR to SR is outputted to the output terminal OUT.

For each coefficient of coefficient means (IIR) to (11B), 3 to
is a normalization means determined according to the specific color to be detected. Since this invention detects skin color, when the constants of the red to blue signals SR-SR are R to KB, the constants for the red to blue signals 5R-SB are minimum when the skin color is detected for each level ER to EB of the red to blue signals 5R-SB. The other signal levels ER and EC are normalized by the level EB of the green signal SB.

Normalized red to blue signals S11', SG', , SR
If the respective signal levels of ' are ER', EG', and EB', then = ER: K2EG: K3 EB・
...(.Here, is .In the case of skin color, if yellow skin is the standard, it is digit, so for each coefficient of coefficient hand IR (IIR) ~ (11B), 3 is as follows. is set to

Now, the levels ER~EB of the red~blue signals S R~SB supplied to the input terminals (2R)~(2B) are shown in Figure 3A~
Assuming that the input shown in D is input, the minimum value calculation circuit (IOA) detects the following color from (12).
Outputs EW and ES are obtained.

Figure 3 A shows the level relationship CER for skin color: EG:
EB = 1: 0.85: 0.7), and B in the same figure shows the level relationship when white (ER:EG・,:εB
-1:1:l), and C in the same figure shows the level relationship when any other color is input (in this example, ER=EB > EG), and the same figure shows the level relationship when only blue is input. (E
Since the R-EG=0 channel is not provided with coefficient means (113) to (IIB) like the skin color detection means (IOB), the coefficients of each channel are all 1. Therefore, when the signals SR-SB shown in FIG. 3A-D are input, a signal having the minimum level of the input signal levels ER-EB is output as shown by the broken line in FIG. 3E-H. . In the case of A in the figure, a blue signal SR is output, and this is used as the white detection output EW. Figure B
In this case, since the human power is applied at the same level, one of the signals (for example, red light SR) is output.

Similarly, in the case of C in the same figure, a green signal SG is output,
In this figure, the first color detection output EW becomes zero.

As is clear from Fig. 3 E-H, the output level from the white detection means (IOA) is maximum when the color is white, and when a signal with a color component that deviates from white is input, the output level decreases. However, when a single color or an intermediate color consisting of two colors with a saturation level of 100% is input, an output whose output level is zero is obtained. Therefore, the white detection output E- is a triangular output curve as shown in the curve LH of FIG. 4. Three points in FIG.

On the other hand, since the skin color detection means (IOB) is provided with coefficient means (1, IR) to (11B), the signal SR-S having the level relationship shown in FIG. 3A-D is
Even if B is input, the levels ER' to EB of the normalized signals SR' to S8' obtained from each.

will be as shown in Figure 3 - L. In the case of skin color, each level ER' to EB' becomes equal due to normalization (I in the same figure).
, when the color is white, the result is J in the same figure, and a red signal SR' is obtained, and when the colors C and D in the figure are input, the results are as shown in K and L in the figure.

Here, the normalized level ER'~EB for skin color
The minimum value of ' is equal to the level ER' when the color is white, and as the input color component deviates from white and skin color, the output level decreases, resulting in a monochromatic color with a saturation of 100% or a two-dimensional color.
Since it becomes zero when it is a color, the skin color detection output εS is the fourth
This results in a trapezoidal output curve like curve LS in the figure.

Then, in the subtracter (14), the skin color detection output ES is subtracted from the white detection output EW, so that the subtracted output EO becomes a triangular wave-like output curve as shown by the curve LO in FIG. 4B. In other words, it is maximum when the color is white, and the level decreases as you move from white to skin tone, reaching zero at skin tone.
Furthermore, when the color deviates from white in a direction other than skin color, it similarly decreases and becomes zero at point a.

In this way, the correction output EO, which is the subtraction output, has an input/output characteristic such that it is at the maximum level only when inputting white color, and becomes zero when inputting skin color.

Correction output EO is correction volume AV for R and G channels.
It is supplied to adders (8R) and (8G) via GSVB. Even if the same white signal is input, the output level of the correction output EO differs depending on the input level, so if you adjust the volumes VR and VG to appropriate values, the correction output EO will always be output when the white signal is supplied. c: Yo-
)7:, RlGf-p 72) LtO) @'1fLz
<tLl)<@ is calculated, so in this case, the green signal SR
only will be emphasized.

This makes white look visually beautiful.

On the other hand, when it is a skin color signal, the correction output EO becomes zero, so the red to blue signals 5R-5B are not corrected at all and the input level itself is output and supplied to the CRT (41), so the skin color is red. There are no inconveniences such as correction to dark skin tone.

Furthermore, as is clear from the characteristic curve in Figure 4B, the range from white to skin tone decreases with a predetermined slope. Even if there is a skin-colored area, an unbalanced correction is not performed where that area becomes completely bluish and other areas are not corrected at all. This is because correction is performed such that the bluish tone gradually becomes lighter starting from skin-colored areas that are close to white.

If you set the correction output EO such that it is maximum for white and completely zero from white to skin tone, then the upper!
This results in an inconvenient correction result as described above.

In the embodiment shown in Fig. 1, a coefficient is applied to the red signal SR and the green signal SG, but in actual broadcasting, skin tones often have a pinkish tone, so skin color detection is performed from the skin color point of the memory color to the red one. It may be configured such that only the red signal is multiplied by a coefficient and the green signal SR is emphasized.

In this case, as shown in FIG. 5, the phase of the corrected output EO is inverted by the inverter (30) and the red signal S
In addition to R, the correction output EO may be added to the blue signal SB via the amplifier (31).

In this embodiment, red and blue signals SR,
In the case where the level of SB is corrected, variable current sources (33), ' (34) and fixed current sources (35) are used, respectively.
), one variable current source (33) performs current subtraction, and the other variable current source (34) performs current addition.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain a correction output EO such that the level is maximum when the color is white, the level decreases as the color deviates from white, and becomes zero when the color is skin tone. Upper whites are displayed beautifully, and skin tones are not corrected at all, so there is no visual discomfort.

In addition, in the conventional example, the color temperature is not corrected for white with small amplitude (below level La), so it looks reddish and CR
The color unevenness of T (4) was easy to stand out, but in this invention, regardless of the size of the amplitude or the size of the white area on the screen,
If it is white, the color temperature will be high (so there will be no such drawbacks,
Moreover, no matter how high the white color temperature is, the skin color does not change, so the white color temperature can be made higher than before.

Furthermore, the current video processor (3) can be used without modification, and the circuit is relatively simple and can be integrated into an IC.

[Brief explanation of drawings]

1 and 5 are system diagrams showing an example of the dynamic color correction circuit according to the present invention, FIG. 2 is a connection diagram showing an example of the minimum value calculation circuit, and FIG. 3 is used to explain the operation of skin color detection. Similarly, FIG. 4 is a characteristic diagram of the skin color detection output, FIG. 6 is a system diagram for explaining the conventional method, and FIG. 7 is a characteristic curve diagram thereof. (101 is a dynamic color correction circuit, (IOA'
), (IOB) are white and skin color detection means, (14
) is an adder, (IIR) to (IIB) are coefficient means, (
8R) to (8B) are adders, and VR-VB is a volume for level adjustment. Figure 3 Procedural Amendment Document October 22, 1980 Patent Application No. 178835 3, Relationship with the case of the person making the amendment Patent Applicant Address No. 6-7-35, Kitashinyo, Tokyo Parts Ward Name ( 21
8) Norio Ohga, representative director of Sony Corporation, 5, date of amendment order: 6, month, 1939.
Number of inventions increased by amendment 7, subject of amendment Number of strong and detailed explanations of inventions in the specification (1) In the specification, page 4, lines 4 to 6, "lower... amended" is changed to the following: Correct it as follows. "You could consider setting it higher, but that way only high-level whites will be corrected." (2) Same, page 12, line 6, ``Redness'' is corrected to ``Ikumi''. that's all

Claims (1)

[Claims] Three primary color signals are supplied to each of a white detection means that can mainly detect white components and a skin color detection means that can mainly detect skin color components, and the skin color detection output and skin color detection obtained from the white color detection means are supplied. The skin color detection output obtained from the means is supplied to a subtracter, and a correction output is obtained in which the level is maximum when the color is white, the level decreases as the color deviates from white, and the level becomes zero when the color is skin color. A dynamic color correction circuit that corrects the color signal of a specific channel among R, G, and B channels.