JPH0652949B2 - Color signal sharpness improvement device - Google Patents

Description

The present invention relates to an apparatus for improving the sharpness of color signals in a color television receiver, a video tape recorder, or the like.

[Prior Art] FIG. 2 is a block circuit diagram of a color signal sharpness improving device. In the figure, (11) is an input terminal to which the carrier color signal (Cin) is input, (12) is a demodulator that demodulates the carrier color signal and outputs two color difference signals RY and BY. ), (14) are sharpness improving circuits for improving the transients of the input color difference signals RY, BY, and (15) are sharpness improving circuits (13), (1).
A modulator for balance-modulating the color subcarrier with the output color difference signals RY and BY of 4), and (16) is an output terminal of the carrier color signal (Cout).

FIG. 3 is a block circuit diagram of an example in which the contour correcting device of Japanese Patent Application No. 62-127830 filed by the present applicant is applied to the sharpness improving circuits (13) and (14). Color difference signal RY
Or input terminal of BY (hereinafter referred to as "input signal"), (2) and (3) are delay circuits that delay the input signal by time D, (4) is every time, output of delay circuit (2) A subtracter that calculates the amplitude difference between the signal and the input signal, (5) is a subtractor that calculates the amplitude difference between the output signal of the delay circuit (2) and the output signal of the delay circuit (3), and (6) is the subtractor ( The absolute value circuit that outputs the absolute value A of the output of 4), (7) is the absolute value circuit that outputs the absolute value B of the output of the subtractor (5), and (8) is the absolute value circuit (6), (7 ) Output A,
A comparator that compares the magnitude of B and outputs a switching control signal based on the result, (9) compares the input signal and the output signals of the delay circuits (2) and (3) based on this switching control signal. This is a switching switch that switches and outputs to the output terminal (10).

FIG. 4 is a signal waveform diagram of each part for explaining the operation of the circuit of FIG. 3, FIG. 5 is a waveform diagram of the carrier color signal of the color bar in one horizontal period, and FIG. 4 (a) is the input carrier color. The waveform diagram of the signal, and FIG. 6B is the waveform diagram of the output carrier color signal in which the sharpness of the signal waveform is improved. Further, FIG. 6 is a waveform diagram for explaining the operation of the ACC circuit (automatic saturation control circuit) not shown, and FIGS. 6 (a) and 6 (b) are respectively shown in FIG.
Of the carrier color signals of (a) and (b), the figure showing the envelope waveform of the color burst signal part, and the figures (c) and (d) are the color burst of Figure 6 (a) and (b), respectively. ACC of signal
It is a figure which shows a detection output voltage waveform.

Next, the operation of the sharpness improving circuit will be described. In FIG. 3, the color difference signal input from the input terminal (1) is delayed by time D in the delay circuit (2), and then delayed by time D in the delay circuit (3).
Be delayed. Therefore, the three input terminals a, b, c of the changeover switch (9) are simultaneously input with the three signals of the input signal at the current time and the input signals at time D and time 2D before. If the output signal of the delay circuit (2) is f (t), the current input signal is f (t + D) and the output signal of the delay circuit (3) is f (tD). FIG. 4 shows the relationship between these three signals. The subtractor (4) calculates (amplitude of the signal f (t))-(amplitude of the signal f (t + D)) (hereinafter, "f (t) -f (t +
D) ”), and the absolute value circuit (6) outputs the absolute value A of the subtraction result. Similarly, the subtractor (5) has f
(t) -f (tD) is calculated, and the absolute value circuit (7) outputs the absolute value B of the subtraction result. The comparator (8) compares the absolute values A and B, and during the period of A <B, the selector switch (9) is switched to the terminal a to output the signal f (t + D), and A = B During the period, the terminal is switched to the terminal b to output the signal f (t), and during the period A> B, the terminal is switched to the terminal c to output the switching control signal to output the signal f (tD) to switch the selector switch (9). As a result, the signal g (t) indicated by the thick solid line in FIG. 4 is output from the output terminal (10).
Is output.

The arithmetic operation in the above conventional example is expressed by the formula: A = | f (t) -f (t + D) | B = | f (t) -f (tD) | The output signal g (t) is Can be expressed as

[Problems to be Solved by the Invention] When the contour correction device according to the prior application is applied to a sharpness improving circuit for color difference signals, a carrier color signal of a color bar as shown in FIG. As shown in (b), the waveform of the color burst signal is also squared with a sharp transient. This carrier color signal is input to the ACC circuit before being displayed on a monitor such as a color television receiver. The ACC circuit detects the magnitude of the color burst signal, and the detection output amplifies the color burst signal and the carrier color signal so that the magnitude of the color burst signal becomes a constant level. However, if sharpness improvement is also applied to the color burst signal, if the ACC detection output voltage of the color burst signal is not improved as shown in Fig. 6 (c) as shown in Fig. 6 (d). Compared with this, the amount of the shaded area becomes larger (note that the shaded area in Figure (c) is cut by the dead zone)
Nevertheless, the peak amplitude of the carrier color signal other than the color burst signal is constant. Therefore, the level (amplitude) of the carrier color signal is relatively suppressed, the saturation degree of the flat portion other than the color change point becomes small, and the color becomes slightly lighter than that when no sharpness is applied. There was a problem.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a color signal sharpness improving device capable of improving the sharpness of a waveform of a carrier color signal without changing the saturation of the color signal. To aim.

[Means for Solving the Problems] A color signal sharpness improving apparatus according to the present invention is a circuit for generating a gate pulse signal including a color burst signal period based on a signal synchronized with a horizontal scanning cycle of a television signal. And a gate circuit that outputs a control signal that causes the switching switch to select the input signal f (t) of the input terminal b during a period in which the gate pulse signal is significant.

[Operation] The gate pulse generating circuit according to the present invention generates a gate pulse signal including a color burst signal period based on a horizontal synchronizing signal or a signal synchronized with the horizontal synchronizing signal. The switch is controlled to select the input signal f (t) for a significant period. As a result, the color burst signal is output in the original waveform in which the sharpness is not improved, and the color saturation of the output color signal does not change.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block circuit diagram of a sharpness improving circuit which is an essential part of the present invention. The same reference numerals as in FIG. 3 indicate the same components. In the figure, (21) is a horizontal synchronizing signal (HD) input terminal of a television signal, (22) is a circuit for generating a gate pulse including a color burst signal period, (2)
3) is a gate circuit in which the switching switch (9) outputs the switching control signal for selecting the terminal b regardless of the content of the switching control signal input from the comparator (8) while the gate pulse signal is significant. .

Next, the operation will be described.

In the figure, the operation from delay circuit (2) to comparator (8) is
Since it is the same as the explanation of the example shown in FIG. 3, the explanation is omitted here.

The changeover control signal output from the comparator (8) is a signal for controlling the changeover switch (9) to select one of the terminals a, b and c when an input signal is present, and is a gate circuit (23).
Input to the switch (9) via. On the other hand, the terminal (2
The horizontal synchronizing signal input from 1) is input to the gate pulse generating circuit (22), and a gate pulse signal including a color burst signal period is created. This gate pulse signal is input to the gate circuit (23), and the changeover control signal for causing the changeover switch (9) to select the terminal b is output regardless of the contents of the changeover control signal during the period when the gate pulse signal is significant. In this way, the switching switch (9) selects the signal f (t) during the period when the gate pulse signal is significant, and the signal f (t + D) during the period A <B during other periods. , A = B, the signal f (t) is selected, and during the period of A> B, the signal f (tD) is selected. As a result, the transient of the carrier color signal is improved and the sharpness is improved, and the color burst signal is obtained by delaying the time D while maintaining the sharpness of the input signal. Therefore, when the carrier color signal modulated by this color difference signal is reproduced, the color does not become thin,
In addition, a reproduced image in which the contours of different colors are emphasized can be obtained.

Although the gate pulse signal is generated from the horizontal synchronizing signal in the above embodiment, it may be generated from the color burst sampling signal generated from the horizontal synchronizing signal.

As described above, according to the present invention, during the burst signal period, the signal selecting operation for improving the sharpness is stopped to stop the signal f.
Since (t) is selected, the waveform of the burst signal in the output carrier color signal does not change.
CC detection output voltage does not increase. Therefore, there is an effect that a color signal sharpness improving device capable of improving the sharpness of only the carrier color signal without changing the color saturation is obtained.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a sharpness improving circuit which is a main part of the present invention, FIG. 2 is a block circuit diagram of a color signal sharpness improving device, and FIG. 3 is a sharpness improving applying the invention of the prior application. A block circuit diagram of the circuit, FIG. 4 is a signal waveform diagram of each part for explaining the operation of this circuit, and FIG. 5 is a waveform diagram of input / output carrier color signals of the color signal sharpness improving device of FIG. FIG. 6 is a diagram showing an envelope waveform of a color burst signal of an input / output carrier color signal and an ACC detection voltage waveform. (2), (3) ... delay circuit, (4), (5) ... subtractor, (6)
, (7) ... absolute value circuit, (8) ... comparator, (9) ... switching switch, (12) ... demodulator, (13), (14) ... sharpness improving circuit, (15) ) …… Modulator, (22) …… Gate / pulse generator, (23) …… Gate circuit. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A color signal sharpness improving device for demodulating a carrier color signal of a television signal into two color difference signals, improving sharpness of waveforms of these color difference signals, and then again modulating the carrier color signal for output. In the above, the sharpness improving means delays the input color difference signal f (t + D) twice by time D, and outputs three signals f (t + D), f.
(T), f (t−D), and a delay circuit that creates two difference absolute values A = | f (t) from these three signals.
-F (t + D) | and B = | f (t) -f (t-D)
An arithmetic circuit for calculating | is compared with the magnitude of absolute values A and B, and the signal f
(T + D), the signal f (t) during the period A = B, A> B
During the period, a comparator that generates a control signal that selects the signal f (t-D), a changeover switch that is controlled by this control signal to select the three signals, and a horizontal synchronizing signal of the television signal or this A circuit for generating a gate pulse signal including a color burst signal period from a signal synchronized with the gate pulse signal, and a gate circuit for outputting a control signal for selecting the signal f (t) to the changeover switch during a period in which the gate pulse signal is significant. An apparatus for improving the sharpness of a color signal, comprising: