JPS60223278A - Digital color correcting device - Google Patents

Abstract

PURPOSE:To digitize a circuit for color correction by obtaining a color correction signal based on a color signal obtained by standardizing a burst signal with a clock signal of a frequency four times as much as a subcarrier frequency. CONSTITUTION:Both R-Y and B-Y signals are extracted by a color signal discriminator 3 out of the color signals supplied from an input terminal 1 and distributed in multiplex time axes. Then the discriminator 3 samples R-Y, B-Y, -(R-Y) and -(R-B) out of the burst signal with a discrimination signal synchronizing with the burt signal supplied from the terminal 1. Furthermore both R-Y and B-Y are sampled. These sampled signals are multiplied by the signals supplied from a corrected angle setting device 7 and a coefficient generator 8 through multipliers 5 and 6 and delivered as an R-Y signal that is corrected via an adder 9. While the B-U signal is delivered as it is through a terminal 11. Thus a digital circuit is obtained for color correction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a method for detecting red (R) from a composite color preview signal.
This invention relates to a digital color correction device that digitally performs signal processing up to the three colors of green (G) and blue ([3).

All signal processing in conventional technology television receivers is performed by analog signal processing, but there are problems that need to be improved, particularly in analog signal processing after the video stage, as described below. However, in terms of performance, this problem is caused by the processing performance on the time axis, which is considered to be a general weakness of analog signal processing.Specifically, it is a problem caused by the processing performance on the time axis, which is considered to be a general weakness of analog signal processing. These include signal separation performance, various image quality improvement performance, etc. On the other hand, from a cost and manufacturing perspective, there is a problem in that even if the circuit is integrated into an IC, there are many external parts and adjustment points. In order to solve these problems, it is being considered to completely digitalize the signal processing from the video stage up to color signal demodulation.

Problems to be Solved by the Invention In such so-called digital television receivers, colors (especially One of the important issues was how to implement a color correction circuit that corrects skin color errors using digital circuits.

Means to solve the problem Figure 3 shows the well-known color difference axis.
The color is expressed by a point on a plane formed by the two axes R-Y and [3-Y. Hail.

The skin color is in the direction of the l axis, which is offset by 33 degrees from the RY axis.

In order to correct the color error that has occurred, it is necessary to move the overall color a little closer to the l-axis (skin tone) direction.To do this, tilt the RY axis toward the 1-axis. This can be achieved with Figure 4 shows the case where the RY axis is tilted.
There is a color that appears at point A. R- before correction
The values of Y and 13-Y are the dimensions a1-γa, respectively. R-
The Y-axis tilted by the angle φ is defined as the (R-Y)' axis, and R
-Correct by changing the Y axis to the ('R-Y)' axis. The value of (RY)' is Ib. ■ku-Y
Calculate the value of (RY)' using the value of 113-Y. Fourth
As shown in the figure, each point of A-El and 0 is determined. 0B
=lLJal, 0E=I-X'al.

---12-- Bll = oE , , Q. fence, -p6.A 辣-11 ANG-m-- 侠i --~J -I) O゛1) Bpo&=βAC, 04Lfshi0ra1
-χal cQ spider-7+ l'dal, , ,
(,)-', l')4) l=CO=eoca<
, yf = 1-rat, Hesi ci, p + 1 Jal
c-n, (,,,ra) If we remove the absolute value from this, we get.

Next, the configuration of the color signal will be described. FIG. 5 shows the relationship between the burst signal, the clock signal, and the square wave SC having the same period as the burst signal. The burst, clock, and SC are all synchronized, and the clock frequency is four times the subcarrier (color subcarrier) frequency. As shown in FIG. 5, the phases of SC, the rising edge of the clock, and the burst signal are aligned and fixed. By setting the L1 clock frequency to four times that of the current carrier and matching the phase as shown in Figure 5, when sampling at the rising edge of the clock, IC Y%B is obtained.
-Y, , (RY), -(11-Y) are obtained, and the phase modulated subcarrier is converted to R-Y113-
Can be demodulated on the Y axis. (Figure 6) In this way, the demodulated R
The -Y and +3-Y color signals are time-base multiplexed as shown in FIG. Therefore, this RY, 13-Y is
R-Y by the color discrimination signal C1) and the inverted CD
113-Y can be selected.

Embodiment FIG. 1 is a block circuit diagram showing an embodiment of the present invention.
is an input terminal for the above-mentioned time axis multiplexed color signal, 2 is an input terminal for the color discrimination signal, 3 is a color signal discriminator, 4 is a clock delay device, 5 is a first multiplier, and 6 is a second multiplier. 7 is a correction angle setter, 8 is a coefficient generator, 9 is an adder, 10 is R-
The Y signal output terminal 11 is an output terminal 13-Y signal.

The color discrimination signal input to the input terminal 2 is obtained by frequency-dividing the clock signal shown in FIGS. 5 and 6 already mentioned. The color signal discriminator 3 is composed of a latch circuit and an exclusive OR circuit, where R-Y
ll) - Extract the Y signal. Since these circuits are well known, the details thereof will be omitted. In addition, the correction angle setting device 7
is constituted by a well-known keyboard or the like, and in response to the key operation, issues a command so that the next-stage coefficient generator 8 generates a correction coefficient in a predetermined signal form. The color signal is a digital signal that is time-based multiplexed according to the principle described above. A color signal multiplexed on one Terama axis is input to the color signal input terminal 1, and the color signal divider 3 outputs the R-Y signal,
Discriminate each into ny signals. R-Y signal is multiplier 5
Then, the 11-Y signal is input to the 1-clock delay device 4. Figure 2 shows a timing diagram. Color signal discriminator 3
The signals output from are ■ and @. By passing the signal of the B-Y system through the one-clock delay device 4, it becomes O. ■ and @ are temporally R-Y, -(+3-Y) or -
(RY), Summer 3-Y combination 1: No. 1 exists.

Now, φ in FIG. 2 is set using the correction angle setting device 7. The coefficient generator 8 outputs Φ set by 7 to the multiplier 5 as a coefficient, and to the multiplier 6 as a coefficient ρ夙φ. The coefficients thus generated and R-
The products of the signals of the Y system and the 13-Y system are calculated and added by an adder 9. The added signal is (RY)
'=(RY)X CS φ+(-(I3-Y)X
φ)=(R-Y) φ-(I3-Y)-φ, which coincides with equation (3). Thus obtained (RY)
' signal is output from I'lY output terminal 10, and B-Y
The system outputs the output of the color signal discriminator 3 as it is from the 13-Y output terminal 11.

Effects of the Invention The present invention can achieve skin color correction processing using a digital circuit, solving performance, cost, and other problems in conventional analog signal processing. Enables skin color correction processing without changing the signal phase,
The color difference axis can also be easily changed.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing one embodiment of the present invention, and FIG.
The figure is a waveform diagram that does not show the waveforms of each part of Figure 1, Figure 3 is a diagram representing the color difference axis, Figure 4 is a diagram representing the color difference axis after skin color correction processing, and Figure 5 is the time of the 13 main issues. Fig. 6 is a time chart showing the axis relationship, Fig. 6 is a time chart showing the correction processing, and Fig. 7 is a tie to show the arithmetic processing for skin color correction.・It is a chart diagram. 1... Color signal input terminal, 2... Color discrimination signal input terminal, 3... Color signal discriminator, 4. ...1 clock delay device, 5...1st multiplier, 6...2nd multiplier, 7--
Correction angle setter, 8... Coefficient generator, 9... Adder,
10...-RY signal output terminal, 11...B-Y signal output terminal. Patent applicant Representative director of NEC Home Electronics Co., Ltd.
Yozo Sasaki

Claims (1)

[Claims] A square wave signal with the same period as the burst signal synchronized with a clock signal having a frequency four times the subcarrier frequency is generated, and the rising edge of this square wave signal and the phase of the (R-Y) signal in the nif burst signal are and by sampling the burst signal using the clock signal, the (I(-Y) signal, (13-Y) signal, and -(
RY) signal and -(13-Y) signal, and from these calculated signals, a (RY) signal and a (13-Y) signal with a period of 1/2 of the square wave signal. A digital color correction device that extracts signals.