JPS63292776A - Contour correcting device - Google Patents

Abstract

PURPOSE:To emphasize a contour without generating a saturation by switching three signals and outputting based on a result obtained by comparing the abso lute values A, B of an amplitude difference of an original input signal, a signal advancing by a prescribed time to this signal and a signal delayed by a pre scribed time. CONSTITUTION:Delay means 2, 3 for delaying the input signal by the prescribed time, means 4, 6 for calculating the absolute value A of the amplitude difference of the output signal and the input signal of the delay means 2, means 5, 7 for calculating the absolute value B of the amplitude difference of the output of the delay means 2 and the output signal of the delay means 3 and a means for comparing the scale of the two absolute values A, B and selecting the input signal during the period of A<B, selecting the output signal of the delay means 2 at the time of A=B and selecting and outputting the output signal of the delay means 3 during the period of A>B are provided. Thereby, a signal in which the amplitude of the input signal is not exceeded but the contour is emphasized is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a contour correction device for improving the sharpness and definition of video signals in color television receivers, video tape recorders, and the like.

[Prior art] Figure 3 is from the journal of the Institute of Electronics and Communication Engineers (July 1983 issue Vol.
8B-BNo. 7) (7) It is a diagram showing four stages of the rising edge of a step waveform by conventional edge enhancement shown in the paper "A method for calculating sharpness in television images."

It is well known that enhancing the contours of a television image improves its sharpness, and is often applied to luminance signals that determine the shape of objects.

As shown in Figure 3, the conventional correction means for emphasizing the contour is configured to obtain a second-order differential signal of the original signal waveform, multiply this signal by a certain coefficient, and then add it to the original signal waveform. be.

To explain with a diagram, the step waveform I 2 (= Q (ri), which is the original signal that has been band-limited, is the second differential waveform Q'' (ri), and the waveform I is obtained by multiplying this by a certain coefficient -a.
d to the original signal waveform ■2 and contour correction signal 9 waveform I 2+
This is to obtain Id.

If the amount of improvement in rise time by this contour correction means is expressed in terms of amplitude change in time, then for the original signal waveform I2, V +
/X + , whereas the contour correction signal waveform I 2
+I d becomes V2/X2, and it can be seen that the rise time is considerably improved.

The sharpness of the image is improved by changing the rise of the signal corresponding to the outline of the television image, that is, by emphasizing the outline.

[Problems to be Solved by the Invention] Conventional contour correction means calculates the second derivative of the original signal waveform,
This signal waveform is multiplied by a certain coefficient and then added to the original signal waveform, so as shown in the shaded area in Figure 3, the original signal waveform exceeds the level of the original signal waveform, so the original signal waveform exceeds the dynamic range of the transmission system. When the amplitude is at its maximum, there is a problem in that it causes waveform saturation.

This invention was made in order to solve the above-mentioned problems, and provides a contour correction device that can enhance contours and change the sharpness of an image without causing saturation of the original signal waveform. The purpose is to

[Means for Solving the Problems] The contour correction means according to the present invention includes a first delay means for delaying an input signal by a predetermined time, and a second delay means for delaying the input signal by a longer time than the first delay means. 2 delay means, means for calculating the absolute value A of the amplitude difference between the output signal of the first delay means and the input signal, and the output signal of the first delay means and the output of the second delay means. Means for calculating the absolute value B of the amplitude difference with the signal, and these two absolute values A.

The magnitude of B is compared, and during the period A<B, the output signal of the second delay means is selected, when A=B, the input signal is selected, and during the period A>H, the output signal of the second delay means is selected. and means for selecting and outputting an output signal of the means.

[Function] The means for selecting and outputting three signals is configured such that when A=B, the rising portion of the signal changes from a low level signal with a large amount of delay to a high level 8 undelayed signal. In the falling portion of the signal, a similar selection is made and the falling time is conversely shortened. Therefore, a signal whose contour is emphasized without exceeding the amplitude of the input signal can be obtained.

[Embodiments of the invention] FIG. 1 is a block circuit diagram of an embodiment of the present invention.

In the figure, (1) is the input terminal to which the luminance signal is input, (
2), (3) are delay circuits that delay the input signal by a time interval, (4) are subtracters that calculate the amplitude difference between the output signal of the delay circuit (2) and the input signal every time, and (5) is a delay circuit. A subtracter that calculates the amplitude difference between the output signal of the circuit (2) and the output signal of the delay circuit (3), (6) an absolute value circuit that outputs the absolute value A of the output of the subtracter (4), (7) is an absolute value circuit that outputs the absolute value B of the output of the subtracter (5), and (8) is an absolute value circuit (6).

A comparator (7) compares the magnitude of the outputs A and H and outputs a switching signal based on the result, and (9) outputs an input signal based on this switching signal, and a delay circuit (2), (3).
) is a selector switch that switches the output signal of the output terminal (lO) and outputs it to the output terminal (lO).

Next, the operation will be explained.

The input signal input from the input terminal (1) is passed through the delay circuit (
2), and then delayed by a delay circuit (3). Therefore, the three input terminals a, b, and c of the changeover switch (8) are simultaneously input with three signals: an input signal at the current time, and an input signal one hour ago and a time 2D ago. Now, the output signal of the delay circuit (2) is f (t)
Then, the current input signal is represented by f (t4-D), and the output signal of the delay circuit (3) is represented by f (t-D). Figure 2 shows the positional relationship of these three signals.
The subtracter (4) calculates (the amplitude of the signal f (t) + 11
1) - (amplitude of signal f (tan)) (hereinafter r'f
(t) −f (tan) J) is calculated, and the absolute value circuit (6) outputs the absolute value A of the subtraction result. Similarly, the subtractor (5) is f (t) − f (
t-D), 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 when A<B, the selector switch (9) is switched to the terminal a and the signal f (t+D) is output, and when A=B, the signal f (t+D) is output. The terminal C is switched to output a signal f (t), and during the period A>B, a switching control signal is output that switches to the terminal C and outputs a signal f (-RO) to switch the changeover switch (9). As a result, a signal g(t) shown by a thick solid line in FIG. 2 is output from the output terminal (lO). This output signal g(t)
The waveform is a signal obtained by correcting the input signal f(t) with a slow rise time to a signal waveform with a fast rise time, and since the amplitude does not exceed the amplitude of the original signal, no saturation phenomenon occurs. .

In addition, when the calculation in the above example is expressed by the formula, A = I f (t) - f (t◆D) l
...(1) B = l f (t
)-f (t-D) l...(2
), and the output signal g(t) is expressed as L-f (t-D)...(period of A>B)-, I.

In the above embodiment, the present invention is applied to a time-continuous signal, that is, an analog signal waveform, but the same effect can be obtained even if it is applied to a discrete signal, that is, a digital signal waveform.

In addition, in the above embodiment, two delay circuits (
2), (3) were used to create three signals delayed by time, but three signals were created using the first delay circuit with a delay time of 2D and the second delay circuit with a delay time of 2D. You may.

Further, in the above embodiment, the three signals are arranged at intervals equal to the delay time, but the delay time intervals do not necessarily have to be the same.

[Effects of the Invention] As described above, according to the present invention, the results of comparing the amplitude difference absolute values A and B between the original human input signal, a signal that is ahead of this signal by a predetermined time, and a signal that is delayed by a predetermined time with respect to this signal are obtained. Since these three signals are switched and outputted based on This has the effect of providing a contour correction device that can perform correction.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram showing the configuration of an embodiment of the present invention, Fig. 2 is a signal waveform diagram of each part to explain the operation of this embodiment, and Fig. 3 is a signal waveform by a conventional contour correction means. FIG. 3 is a waveform diagram for explaining the processing of FIG. (2), (3)...Delay circuit, (4), (5)
... Subtractor, (8), (7) ... Absolute value circuit, (8) ... Comparator, (8) ... Changeover switch. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) a first delay means for delaying the input video signal for a predetermined time; a second delay means for delaying the input video signal for a time longer than the first delay time; and an output signal of the first delay means; means for calculating the absolute value A of the amplitude difference with the input video signal; means for calculating the absolute value B of the amplitude difference between the output signal of the first delay means and the output signal of the second delay means; Comparing the magnitudes of the two absolute values A and B, the input video signal is selected during the period when A<B, the output signal of the first delay means is selected when A=B, and A>B. and means for selecting and outputting the output signal of the second delay means during the period.