JPH0488792A - Skin color correction circuit - Google Patents

Abstract

PURPOSE:To attain skin color correction by adding a prescribed number of multiple of an absolute value component of a Q signal to an I signal so as to suppress a change in the color saturation after correction of a signal having a comparatively large phase difference from the I axis. CONSTITUTION:An output ¦Qo¦ of an absolute value circuit 18 is fed to a K multiple circuit 20, in which the signal is multiplied by K. The output is fed to an adder 24 together with an Io signal inputted to a terminal 12 via a switch 22. Moreover, the Qo signal is fed to a contact 26b of the switch 26 and a DC voltage 28 is fed to a contact 26a. When a phase deciding circuit 16 decides the lock range by a skin color correction circuit 10, the switch 22 is closed and a moving contact 26c of the switch 26 is switched to the contact 26a. Thus, since the output ¦Qo¦ of the absolute value circuit 18 is fed to the K multiple circuit 20, in which the signal is multiplied by K and the switch 22 is closed, the signal is fed to an adder 24. Thus, a current Io' (=Io+K¦Qo¦) is outputted at the output of the adder 24, that is, at a terminal 30.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a skin color correction circuit, and in particular, in a certain area of color signals (I signal and Q signal), the Q signal is set to zero and only one signal is output. The present invention relates to a skin color correction circuit that outputs.

[Prior art]

Generally, the color tone may change due to distortion in the television signal transmission path or in the receiver. Although some color shifts are not noticeable, humans are sensitive to skin color, which is the color they remember, and even slight changes are easily recognized. Therefore, it is desirable to automatically correct changes in signals that have a tone close to skin color.

Such skin color correction circuits have been proposed in Japanese Patent Laid-Open No. 58-4879 and Japanese Patent Publication No. 56-37757. This proposed skin color correction circuit uses internal division of vectors.

In FIG. 2, vector C represents the input color signal vector, and vector R represents the reference skin color signal vector. Here, the reference value vector [
) th, and the amplitude vector of color vector difference D= l
The ratio D/[)th with R-CI indicates how close the input color signal is to the reference skin color signal, and according to this ratio,
The input color signal and the reference skin color signal are mixed as shown in the following equation (1), and the skin color of the color signal is corrected.

C"= (1-[)/[)th) F2+[)/[)t
hcD≦[)tb =CID>Dth... (1) [Problem to be solved by the invention] According to the conventional skin color correction method as shown in FIG.
As shown by the dotted line in the figure, the color is drawn to the chromaticity point of skin color, but the color saturation also changes.

Therefore, a main object of the present invention is to provide a skin color correction circuit with less change in color saturation.

[Means to solve the problem]

Simply put, the present invention consists of an absolute value means that takes the absolute value of the Q signal, a phase determination means that receives the signal and the Q signal from the absolute value means, and determines whether or not it is in the skin color correction area, and an absolute value means. A skin color correction circuit comprising a predetermined multiplying means for multiplying the Q signal by a predetermined value, and a means for outputting an I signal corrected by adding the I signal and the output of the predetermined multiplying means according to the signal from the phase comparison means. It is.

[Effect]

The phase determination means determines whether or not it is in the skin color correction area,
A signal is output when it is in the skin color correction area. In response to this signal, the Q signal multiplied by a predetermined value from the predetermined multiplying means and the input I
The corrected signal (2) is output by adding the signal. In this way, by adding a predetermined times the absolute value component of the Q signal to the engineering signal, changes in color saturation after correction of a signal having a relatively large phase difference with the {circle around (2)} axis are suppressed.

〔Effect of the invention〕

According to this invention, even if skin color correction is performed, the color saturation before and after the correction can be made almost constant.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

〔Example] FIG. 1 is a bronc diagram showing an embodiment of the present invention.

The skin color correction circuit 10 of this embodiment has terminals 12 and 14.
The terminal 12 is supplied with an input I signal, which is an Io-fold signal, and the terminal 14 is supplied with an input Q signal, which is a Qo-fold signal. It is applied to the Io times signal phase determination circuit 16 and to the Qo times signal absolute value circuit 18. The absolute value circuit 18 outputs a QO multiplied signal absolute value 1Qol, which is applied to the phase determination circuit 16. The phase determination circuit 16 determines whether it is a skin color correction area. That is, if it is desired that the pull-in range of the skin color correction circuit 10 be within ±30° with respect to one axis, it is determined whether the following equation (2) is satisfied.

If it is within the pull-in range, the phase determination circuit 16 outputs a high-level control pulse.

The output IQOI of the absolute value circuit 18 is also given to the K multiplication circuit 20 and multiplied by K (0.25 in the embodiment). The output of the doubler circuit 20 passes through the switch 22 and is applied to the adder 24 together with the 0 signal input to the terminal 12.

In addition, the Qo multiplied signal input to the terminal 14, the switch 26
The contact 26a of this switch 26
b, and a DC voltage 28 is applied to the contact 26a of this switch 26. The output of the adder 24 is connected to the terminal 3o, and the movable contact 26c of the switch 26 is connected to the terminal 32.

When the phase determination circuit 16 determines that the current is within the pull-in range of the skin color correction circuit 1o, the switch 22 is closed and the movable contact 26c of the switch 26 is switched to the contact 26a side. Therefore, since the output IQOI from the absolute value circuit 8 is multiplied by the doubler circuit 20 and the switch 22 is turned on, the adder 24
is input. Therefore, the output of the adder 24, ie, the terminal 30, is Io' (=Io + KIQo 1). Corrected 1o' obtained in this way
The color saturation of the signal is as shown in the table below.

5'10"15@20"25° 30°I
o O,9960,9850,9660,9400
,9060,866Q o O,0870,175
0,2590,3420,4230,5K Q o
O,0220,0440,0650,0B60.106
0.125I o 1.01B 1.029 1
．． 031 1.0261.0120.991 As can be seen from the table above, when simply outputting only the Io times signal as in the past, the color saturation is 1.0 for a signal with a phase difference of lOo from the ■ axis. Although the change is only 5%, the color saturation of a signal with a phase difference of 30° changes by nearly 15%. On the other hand, as in the embodiment of FIG.
By adding , the change in color saturation of the IO° signal is ±
It falls within about 3%.

In addition, in the case of ±30″30°, the switch 26 is connected to the contact 26a.
Since it is switched to the side, it becomes zero in terms of AC,
Therefore, the Qo' signal is not output, and only the Io' signal, that is, the I-axis component, is output for skin color correction.

■When the axis is not ±30°, the signal of the phase determination circuit 16 becomes low level, the switch 22 is turned off, and the switch 2
The movable contact 26c of No. 6 is switched to the contact 26b side.

Therefore, the Io multiplied signal input to the terminal 12 and the Qo signal input to the terminal 14 are directly transmitted to the terminals 30 and 32 as I.

It is output as a "signal" and a Qo' signal. Therefore, there is no change in the signal when it exceeds the skin color correction area.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a vector diagram illustrating a skin color correction method using internal division of vectors. In the figure, 10 is a skin color correction circuit, 12, 14, 30 .
32 is a terminal, 16 is a phase determination circuit, 18 is an absolute value circuit,
20 is a doubler circuit, 22, 26 is a switch, and 24 is an adder. Patent Applicant Sanyo Electric Co., Ltd. Agent Patent Attorney Yama 1) Yoshihito Diagram 2

Claims (1)

[Scope of Claims] Absolute value means for taking the absolute value of the Q signal; phase determination means for receiving the I signal and the Q signal from the absolute value means to determine whether or not it is within a skin color correction region; and from the absolute value means. a predetermined multiplying means for multiplying the Q signal by a predetermined value, and a means for outputting an I signal corrected by adding the I signal and the output of the predetermined multiplying means according to the signal from the phase comparison means. , skin color correction circuit.