JPH04137891A - Color signal generating circuit - Google Patents

Abstract

PURPOSE:To suppress power consumption and to generate a color signal while preventing production of a false color by providing an arithmetic mean circuit employing a comb-line filter to the generating circuit. CONSTITUTION:A line sequential color difference signal is subjected to simultaneous processing by a simultaneous processing circuit 10 and the result is modulated by using a carrier having a frequency passing through a comb-line filter circuit 31. The modulated signal is subjected to arithmetic mean processing by an arithmetic mean circuit 30 including the comb-line filter 31 used as a 1H delay circuit and demodulated further by a demodulation circuit 40. Then R, G, B color signals are generated at a matrix circuit 50 by using the color difference signal and the luminance signal after demodulation. In place of the arithmetic mean circuit employing a CCD requiring the drive current, since the arithmetic mean circuit using the comb-line filter not requiring the drive current as the 1H delay circuit is provided, the power consumption is reduced and the production of a false color is prevented.

Description

BACKGROUND OF THE INVENTION Technical Field The present invention relates to a luminance signal Y and a line sequential color difference signal B-Y,
The present invention relates to a color signal generation circuit that generates color signals R, G, and B by inputting R-Y.

Prior art and its problems From the luminance signal Y and the line sequential color difference signals B-Y, R-Y, R,
An example of a conventional circuit that generates three primary color signals of G and B is the second
As shown in the figure. The conventional circuit shown in FIG. 2 includes a synchronization circuit 10. It includes an arithmetic mean circuit BOA BOB and a matrix circuit 50.

The line sequential color difference signals B-Y and R-Y are applied to a synchronization circuit 10 and are synchronized. The synchronization circuit IO is composed of an IH delay circuit 11 (IH is a horizontal scanning period) and two changeover switches 12 and 13. Changeover switch 12.1
3 is linked and switched for each IH. Changeover switch 1
2 outputs a synchronized color difference signal B-Y, and a changeover switch 13 outputs a synchronized color difference signal RY. FIG. 3 shows an input signal to the synchronization circuit 10 (denoted by symbol e) and an IH-delayed signal (denoted by symbol f). In this time chart, the luminance signal Y
is given a pre-twist number indicating the order of horizontal scanning lines. In the synchronized color difference signals B-Y and R-Y, the first twist numbers of the luminance signal Y are the same (for example, B-Y and R
-Y and B Y2 and R-Y2) are generated from the same screen, so the colors match between them, but the luminance signals Y with different twist numbers (for example, R-Y and B-
If the three primary color signals of R, G, and B are generated using the three primary color signals of R, G, and B, false colors are likely to occur.

Conventionally, this problem has been dealt with by providing arithmetic averaging circuits 60A and BOB and taking the arithmetic mean of color difference signals between adjacent lines.

The arithmetic averaging circuit 8DA is connected to the IH delay circuit 61A and the IH
It is composed of an adder circuit 62A that adds a delayed signal and a non-delayed signal, and the arithmetic mean circuit 60B is similarly composed of an IH delay circuit 61B and an adder circuit 62B. These arithmetic mean circuits 60A.

The matrix circuit 50 generates color signals R, G,
B is created.

In such conventional averaging circuits BOA and SOB, IH delay circuits EilA and EilA and B are CCD (
This is realized using a Charge Coupled Device. However, CCDs are current-driven and have the problem that the driving current is large.

SUMMARY OF THE INVENTION OBJECTS OF THE INVENTION An object of the present invention is to provide a circuit that generates color signals R, G, and B while reducing power consumption and preventing the occurrence of false colors.

Structure 1 of the Invention Functions and Effects This invention provides a synchronization circuit for synchronizing line-sequential color difference signals;
It includes a modulation circuit that modulates the synchronized color difference signal using a carrier of a predetermined frequency, and a comb filter that delays the signal modulated by the modulation circuit by one horizontal scanning period. an arithmetic mean circuit that calculates the arithmetic mean of the signals; a demodulation circuit that demodulates the output signal of the arithmetic mean circuit; and a demodulation circuit that creates a color signal using the luminance signal and a color difference signal obtained from the demodulation circuit. It is characterized by having a matrix circuit.

According to this invention, line sequential color difference signals are synchronized by a synchronization circuit. The synchronized color difference signal is modulated using a carrier at a frequency that can pass through the C-shaped filter circuit. This modulated signal is arithmetic averaged by an arithmetic averaging circuit including a comb filter used as an IH delay circuit, and further demodulated by a demodulation circuit. R, G, and B color signals are created by a matrix circuit using the demodulated color difference signal and luminance signal.

According to this invention, an arithmetic mean circuit using a comb-shaped filter that does not require a drive current as an IH delay circuit is provided instead of an arithmetic mean circuit using a COD that requires a drive current, thereby reducing power consumption. It is possible to achieve this and prevent the occurrence of false colors.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 shows an embodiment of the present invention and is a block diagram of a color signal generation circuit. Components in FIG. 1 that are the same as those shown in FIG. 2 are given the same reference numerals.

The luminance signal Y is input to the matrix circuit 50.

The line sequential color difference signals B-Y and R-Y are input to the synchronization circuit 10 and applied to the IH delay circuit 11, the a terminal of the changeover switch 13, and the b terminal of the changeover switch 12, respectively. The delayed output signal of the IH delay circuit 11 is transferred to the selector switch 1.
2 and the b terminal of the selector switch 13, respectively. The changeover switches 12 and 13 are switched in conjunction with each IH using a changeover control signal. As a result, the synchronized color difference signals B-Y and R-Y are sent to the synchronization circuit 1.
Output from 0.

Color difference signal B-Y output from the synchronization circuit 10.

RY is applied to a balanced modulation circuit 20. The purpose of modulating the color difference signal is to change the frequency to a frequency that passes through a comb filter 3 including a glass delay line of an arithmetic averaging circuit 30, which will be described later. The subcarrier frequency f of the balanced modulation circuit 20 is f − f (2N+1)/2 (N is a positive SC
H integer). Generally speaking, fSC”fHX455
/ 2 = 3.58MHz is good. However, “5c=
It can also be N-fH. In this case, it is necessary to replace the subtraction circuit 32 included in the arithmetic averaging circuit 30, which will be described later, with an addition circuit.

The modulated color difference signals R-Y and B-Y are mixed in an adder circuit 21 and then fed to an arithmetic averaging circuit 30.

The arithmetic mean circuit 30 includes a comb filter 3 for IH delay and a subtraction circuit 32. Since the signals output from the balanced modulation circuit 20 are mutually inverted for each IH, the subtraction circuit 32 substantially performs addition processing. In this circuit 30, the arithmetic mean of the signals around 1H is taken to prevent the occurrence of false colors.

The signal output from the arithmetic mean circuit 30 is demodulated by the demodulation circuit 40 and output as one color difference signal B-Y and R-Y. These color difference signals B-Y and R-Y are input to the matrix circuit 50. and.

Color signals R, G, and B are created by the matrix circuit 50.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, and is a block diagram of a one-color signal generation circuit. FIG. 2 is a block diagram showing an example of a conventional color signal generation circuit. FIG. 3 is a time chart of color difference signals. 10...Synchronization circuit. 20...Balanced modulation circuit. 30...Arithmetic average circuit. 31...Comb filter. 40... Demodulation circuit. 50...Matrix circuit. that's all

Claims (1)

[Claims] A synchronization circuit that synchronizes line-sequential color difference signals, a modulation circuit that modulates the synchronized color difference signals using a carrier of a predetermined frequency, and a signal modulated by the modulation circuit for one horizontal scanning period. 1 of the input modulated signal, including a delayed comb filter.
A color signal is generated using an arithmetic mean circuit that calculates the arithmetic mean of signals before and after the horizontal scanning period, a demodulation circuit that demodulates the output signal of the arithmetic mean circuit, and a luminance signal and a color difference signal obtained from the demodulation circuit. A color signal generation circuit with a matrix circuit that creates a color signal.