JPH088651B2 - Contour correction device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour correction apparatus for enhancing the sharpness of an image by enhancing the contour of a video signal in a color television receiver, a video tape recorder or the like.

[Prior Art] FIG. 3 is a block circuit diagram of a configuration example of a contour correcting device of Japanese Patent Application No. 62-127830, which is a prior application of the present applicant, and (1) shows an input terminal to which a video signal is inputted, (3) and (4) are delay circuits that delay the input signal by time 3D, (9) is a subtracter that calculates the amplitude difference between the output signal of the delay circuit (3) and the input signal, and (10) at each time. Is the output signal of the delay circuit (3),
A subtractor for calculating the amplitude difference between the output signals of the delay circuit (4),
(11) is an absolute value circuit that outputs the absolute value A of the output of the subtractor (9), (12) is an absolute value circuit that outputs the absolute value B of the output of the subtractor (10), and (13) is an absolute value A comparator that compares the magnitudes of the outputs A and B of the circuits (11) and (12) and outputs a switching control signal based on the result, (14) is a delay signal based on this switching control signal This is a switching switch that switches the output signals of the circuits (3) and (4) and outputs them to the output terminal (15).

 Next, the operation will be described.

The input signal input from the input terminal (1) is delayed by the delay circuit (3) for time 3D, and then delayed by the delay circuit (4) for time 3D. Therefore, the three input terminals a, b, and c of the switching switch (14) have the input signal of the current time and the time 3
Three signals, D and the input signal 6D before the time, are simultaneously input. Now, assuming that the output signal of the delay circuit (3) is f (t), the current input signal is f (t + 3D), and the output signal of the delay circuit (4) is f (t-3D). FIG. 4 (a) shows the positional relationship of these three signals. The subtractor (9) outputs (amplitude of signal f (t))-(amplitude of signal f (t + 3D)) (hereinafter, "f (t) -f (t +)" every time.
3D) ”)) and calculate the absolute value circuit (11)
Outputs the absolute value A of the subtraction result. Similarly, the subtractor (1
0) calculates f (t) -f (t-3D), and the absolute value circuit (1
2) outputs the absolute value B of the subtraction result. The comparator (13) compares the absolute values A and B, and during the period of A <B, switches the switching switch (14) to the terminal a and outputs the signal f (t + 3D),
When A = B, the signal is switched to the terminal b and outputs the signal f (t). During the period of A> B, the signal is switched to the terminal c and the signal f (t-3D).
The switch (14) is switched by outputting a switching control signal for outputting. As a result, the output terminal (15) outputs the signal g (t) shown by the thick solid line in FIG. 4 (b). The waveform of the output signal g (t) is a signal obtained by correcting the input signal f (t) having a slow rise time and the signal waveform having a fast rise time.

When the calculation in the above embodiment is expressed by an equation, A = | f (t) -f (t + 3D) | B = | f (t) -f (t-3D) | The output signal g (t) is Is represented as

[Problems to be Solved by the Invention] The contour correction device according to the prior application has a predetermined time
When the S / N of the switched signal is bad, that is, the input signal When a noise having a large amplitude is included in, for example, when a video signal including noise as shown in FIG. 5 (a) is input, as shown in FIG. 5 (b),
Since the signals are switched at an undesired time point, the waveform of the output signal g (t) is distorted and the desired contour correction effect cannot be obtained.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a contour correction device that is less susceptible to noise.

[Means for Solving the Problem] A contour correction device according to the present invention extracts a first delay signal delayed by a predetermined time from an input video signal and a second delay signal delayed by a time longer than the predetermined time. With respect to the first and second delay means, the input signal to the first delay means, the first delay signal and the second delay signal, a signal delayed by a unit time smaller than the predetermined time and a lead, respectively. First to third adding means for creating an additional signal and calculating an addition value or an average value for each of the three signals, and an absolute value X of a value obtained by subtracting the first addition value from the second addition value. , And means for calculating the absolute value Y of the value obtained by subtracting the third added value from the second added value, and the magnitudes of the absolute values X, Y are compared, and the period of X <Y is the first value. Select the input signal to the delay means, and set X = Y Selects the first delay signal, the period of X> Y is obtained by a means for outputting as a video signal and selecting the second delay signal.

[Operation] As the calculated values of the first to third adding means, the input signal to the first delay means, the first delayed signal and the second delayed signal are delayed by unit time and advanced, respectively. Since it is an addition value or an average value of and, even if noise is included, it is averaged, and the change of the value due to noise is reduced. Therefore, when selecting the input signal and the first and second delay signals based on the magnitude comparison of the absolute values of the differences between these three added values or the average value, a wrong signal is selected due to noise. Less often.

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

In FIG. 1, the same reference numerals as those in FIG. 3 indicate the same components, and (2) and (5) are delay circuits for delaying the input signal by the time D, (3) and (4), respectively.
Is a delay circuit that delays the input signal by 1D, 2D, and 3D,
(6), (7) and (8) are adders. When the 3D delayed output signal of the delay circuit (3) is f (t), the input signal is f (t + 4D) and the output signal of the delay circuit (2) is f (t + 3).
D), the 2D delay output signal of the delay circuit (3) is f (t +
D), 1D delay output signal is f (t + 2D), delay circuit (4)
3D delay output signal is f (t-3D), 2D delay output signal is f
The (t-2D) and 1D delayed output signals can be expressed as f (t-D), and the output signal of the delay circuit (5) can be expressed as f (t-4D). Further, the adders (6), (7) and (8) are respectively (f (t + 4
D) + f (t + 3D) + f (t + 2D)), (f (t + D)
+ F (t) + f (t-D)) and (f (t-2D) + f
(T-3D) + f (t-4D)) is added and the added value is output to the subtracters (9) and (10).

Next, the operation will be described. The video signal f (t + 4D) input from the input terminal (1) is supplied to the delay circuit (2),
The signal f (t + 3D), f (t), f passes through (3) and (4).
(T-3D), which is switched by the switch circuit (14) and the output signal g (t) is obtained at the output terminal (15). The switching control signal of the switch circuit (14) is created as follows. The adder (6) receives the input signal f (t + 4D)
And the 1D delay output signal f (t + 3D) of the delay circuit (2),
Sum with 1D delay output signal f (t + 2D) of delay circuit (3) (I = −1,0,1), and the adder (7) outputs the 2D delayed output signal f (t + D) of the delay circuit (3) and the 3D delayed output signal f (t). Sum with 1D delay output signal f (t-D) of delay circuit (4) The adder (8) calculates the 2D delay output signal f (t-2D) of the delay circuit (4) and the 3D delay output signal f (t-3D),
Sum of output signals f (t-4D) of delay circuit (5) To calculate. The subtractor (9) outputs the output of the adder (7) every time. And the output of the adder (6) Difference And the absolute value circuit (11) outputs the absolute value X of the subtraction result. Similarly, the subtractor (10) And the absolute value circuit (12) outputs the absolute value Y of the subtraction result.

The comparator (13) compares the magnitudes of absolute values X and Y,
In the period of X <Y, the switching switch (14) is switched to the terminal a to output the signal f (t + 3D), and when X = Y, it is switched to the terminal b to output the signal f (t). Is terminal C
And a switching control signal for outputting the signal f (t-3D). As a result, the output terminal (15) is shown in FIG. 2 (a).
The signal g (t) shown in FIG. 2B is output even when a video signal containing a noise component as shown in FIG. This output g (t) is the output g shown in FIG. 4 (b) when there is no noise without the generation of an undesired signal caused by a selection error due to noise as shown in FIG. 5 (b). The waveform is almost similar to that of (t), which prevents the selection error due to noise and improves the signal rise (transient) time.

In addition, when the calculation in the above embodiment is expressed by an equation, Is represented as

In the above embodiment, the three switched signals are the signals f (t + 3D), f (t), f (t-3D) having a 3D time difference, but the time interval is three signals. If there is a correlation, any time difference may be set.

Further, in the above embodiment, in order to reduce the influence of noise, the added value of the signal to be switched and the two signals before and after it is used.
The average value may be used, and the effect of noise can be further reduced by increasing the number of signals (samples) that are added or averaged.

[Effects of the Invention] As described above, according to the present invention, the input signal is delayed to create three switched signals having different delay amounts, and each of these three switched signals is smaller than the delay amount. A configuration in which a signal delayed by unit time and a signal advanced by each time are created to calculate an added value or an average value, and a switching signal is created based on the added value or the average value to switch the above three switched signals Therefore, even if the input signal contains noise, the effect of noise is reduced because the amplitude comparison is performed with the added value or average value of the signal delayed by the unit time and the signal advanced. There is an effect that a selection error is reduced and a contour correction device for a video signal with less influence of noise can be obtained.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an embodiment of the present invention, FIG. 2 is a signal waveform diagram of each part for explaining the operation of this embodiment, and FIG. 3 is a structural example of a contour correction device according to the prior application. FIG. 4 is a block circuit diagram, and FIGS. 4 and 5 are signal waveform diagrams of respective parts for explaining the operation of this configuration example. (2), (3), (4), (5) ... Delay circuit,
(6), (7), (8) ... Adder, (9), (10) ...
… Subtractor, (11), (12) …… Absolute value circuit, (13) ……
Comparator, (14) ... Switching switch. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A first delay means for extracting a first delay signal delayed by a predetermined time from an input video signal, and a second delay delayed by a time longer than the predetermined time from the input video signal. Second delay means for extracting a signal, and a signal delayed by a unit time smaller than the predetermined time and a signal advanced from the input signal to the first delay means, and the added value of these signals and the input signal. Alternatively, a first addition means for calculating an average value and a signal delayed by the unit time and a signal advanced from the first delay signal are taken out, and an addition value or an average value of these signals and the first delay signal is taken out. And a signal which is delayed by the unit time from the second delay signal and a signal which has advanced, and the addition of these signals and the second delay signal. A third adding means for calculating a value or an average value, an absolute value X of a value obtained by subtracting the calculated value of the first adding means from the calculated value of the second adding means, and the second adding means. The means for calculating the absolute value Y of the value obtained by subtracting the third adding means from the calculated value is compared with the magnitude of the absolute values X, Y, and input to the first delay means for the period of X <Y. A contour correcting apparatus comprising: a signal selecting unit for selecting the first delay signal during the period X = Y and selecting and outputting the second delay signal during the period X> Y.