JPH0669215B2 - Vertical contour enhancement circuit of television receiver - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical contour enhancement circuit for enhancing the sharpness of an image by enhancing the vertical contour portion of the image in a television receiver.

[Background of the Invention]

As a means for obtaining high sharpness for a color television image, for example, as shown in Japanese Patent Publication No. 59-23973, there is a vertical contour enhancement circuit for enhancing the vertical contour portion of the image by preshooting and overshooting. Widely used.

The vertical edge enhancement of an image according to such a conventional technique will be described with reference to FIG.

FIG. 2 is a block diagram showing a conventional vertical contour emphasis circuit. In FIG. 2, 201 is a vertical contour signal generation circuit, 202 is a video signal, 203 and 204 are one horizontal period delay circuit, and 205 is The coefficient unit The coefficient unit to Coefficient unit, 208 is an adder, 209 is a vertical contour correction signal, 21
Reference numeral 0 is a delay compensation circuit that compensates for the delay amount of the vertical contour signal generation circuit 201, 211 is an adder, and 212 is a vertical contour emphasis signal.

The circuit operation of FIG. 2 will be described. First, as the video signal 202, consider a video signal of an image as shown in FIG. This signal has high brightness at the center of the screen and low brightness at the upper and lower ends. In FIG. 3 (a), the shaded portion is a portion having a luminance inclination, and FIG. 3 (b) shows the relationship between the coordinates in the vertical direction of the screen and the luminance. As shown in FIG. 3 (a), the luminance changes from the lower side to the higher side in the vertical direction of the screen at the upper end of the screen, while the luminance changes from the higher side to the lower side in the vertical direction of the screen at the lower end of the screen. The state of the video signal 202 at the upper end of the screen is shown in FIG.
The situation is shown in FIG. 4 (b).

Now, such a video signal 202 is divided into two as shown in FIG. 2 and one is inputted to the vertical contour signal generating circuit 201 and the other is inputted to the delay compensating circuit 210.

In the vertical contour signal generation circuit 201, the input video signal 202
Is delayed by each horizontal period by the delay circuits 203 and 204, and the input video signal and the delayed video signal are output by the coefficient units 205, 206 and 207. It is input to the adder 208, and then output as the vertical contour correction signal 209.

In the delay compensation circuit 210, the input video signal 202 is 1
The output is delayed by the horizontal period.

Now, for convenience of explanation, the waveform of the output of the delay compensation circuit 210 will be described below with reference to FIGS. 4 (a) and 4 (b).
Therefore, the video signal 202 is a signal obtained by advancing the waveforms shown in FIGS. 4A and 4B by one horizontal period. In this way, the waveform of the video signal 202 has the waveforms shown in FIGS. 4 (a) and 4 (b).
Assuming that the waveform has been advanced in the horizontal period, the waveform of the vertical contour correction signal 209, which is the output signal thereof, from the waveform of FIG. The waveform shown in (c) is obtained, and the waveform shown in FIG. 4 (d) is obtained in contrast to the waveform shown in FIG. 4 (b).

Next, the output from the delay compensation circuit 210 and the vertical contour correction signal 2
09 is input to the adder 211, added there, and output as the vertical contour emphasis signal 212. That is, when these signals are added by the adder 211, a vertical contour emphasis signal 212 as shown in FIG. 4 (e) is obtained for the signals of FIGS. Causes an undershoot in a portion where the luminance increases and an overshoot occurs in a portion where the luminance becomes constant and a high luminance. On the other hand, for the signals of FIGS. 4 (b) and 4 (d), the vertical contour emphasis signal 212 as shown in FIG. Shooting occurs, and undershoot occurs in a portion where the brightness gradually decreases and becomes a constant low brightness.
This state is shown on the screen as shown in FIG.
As described above, conventionally, overshoot and undershoot occur in the vertical contour portion of the image, as shown in FIG.
The brightness was changed as shown in, and the image was emphasized. In the vertical contour enhancement of an image by such a conventional vertical contour enhancement circuit, although the contour is visually clear and good for obtaining high sharpness, it is good, but the luminance level is changed to change the luminance level as shown in FIG. Since it is increased or decreased as shown in (), there are drawbacks such as (1) blooming is likely to occur and (2) beam spot is likely to be thick.

[Object of the Invention]

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a high-frequency emphasis circuit capable of emphasizing a vertical contour portion of an image in a television receiver without increasing or decreasing the brightness level. It is in.

[Outline of Invention]

In the present invention, in order to achieve the above-mentioned object, a first delay means for delaying an input video signal by a unit of an integral multiple of one horizontal period and an output signal of the first delay means are further added. Second delay means for delaying in units of a period that is an integral multiple of the horizontal period, a video signal input to the first delay means, an output signal of the first delay means, and an output signal of the second delay means. And a plurality of coefficient units for multiplying each of the coefficient units by a predetermined magnification, a calculation unit that calculates each output signal from the plurality of coefficient units, and an image of the image in the input video signal from the output signal of the calculation unit. A vertical contour detecting means for detecting a vertical contour position; and a switching means for switching respective output signals delayed by the first and second delay means according to an output signal from the vertical contour detecting means. Vertical wheel Selects the output signal of the second delay means when the detecting means does not detect the vertical contour position,
By switching the switching means so as to select the output signal of the first delay means during detection, a video signal in which the vertical contour portion of the image is emphasized is output.

Example of Invention

 An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, 101 is a vertical contour detection circuit, 102 is a video signal, 103 and 104 are delay circuits for one horizontal period, and 105 is an input signal. Coefficient unit, 106 is Coefficient unit, 107 is Coefficient unit, 108 is an adder, 109 is a video signal obtained by delaying the video signal 102 by one horizontal period, 110 is a video signal obtained by delaying the video signal 102 by two horizontal periods, and 111 is the absolute value of the output from the adder 108. An absolute value circuit, 112 is a comparison circuit that compares the output from the absolute value circuit 111 with a constant value 113, and 114 is the video signals 109 and 110.
Switching circuit for switching between and by the output of comparison circuit 113, 1
Reference numeral 15 is a vertical contour emphasis signal which is the output of the switching circuit 114, and 116
Is a vertical contour detection signal.

Next, the operation of the embodiment shown in FIG. 1 will be described with reference to FIGS. 6 and 7.

As the video signal 102, it is assumed that an image as shown in FIG. 3 (a) is converted into a video signal, as described in the conventional example.

Therefore, first, the case where the luminance gradually increases from the low luminance as shown in FIG. 3A will be described. That is, the case where a signal waveform as shown in FIG. 6A is input as the video signal 102. Such video signal 102
Is input, the signal waveform shown in FIG. 6B is obtained as the video signal 109 output from the one horizontal period delay circuit 103. Further, when the video signal 109 is delayed by the one horizontal period delay circuit 104, a waveform as shown in FIG. 6C can be obtained as the video signal 110. These video signals 102, 109, and 110 are sequentially processed by coefficient units 105 and 10 respectively.
Enter 6,107, Then, when input to the adder 108 and added, a vertical contour detection signal 116 in which the vertical contour position in the video signal 109 is detected can be obtained as shown in FIG. When this vertical contour detection signal 116 is converted into an absolute value by the absolute value circuit 111 and the code is removed, the vertical contour detection signal shown in FIG. 6 (f) is obtained. After that, when the comparator 112 compares it with the specific constant level value 113, it is possible to obtain a signal which becomes the'H 'level only at the vertical contour position as a result of the comparison. The signal waveform of this comparison result is the same as that of FIG. 6 (f). The output from the comparator 112 is the switching circuit 1
Entered in 14. The switching circuit 114 selects and outputs the video signal 109 when the output from the comparator 112 is at the “H” level.
At L'level, the video signal 110 is selected and output. The respective selection periods are shown in FIG. 6 (g). Then, the output of the switching circuit 114 has a waveform as shown in FIG. 6E, and as the vertical contour emphasis signal 115, a signal in which the transient region of the brightness level in the vertical direction of the screen is reduced can be obtained. As a result, the vertical contour portion of the image can be made steeper so that the image can be emphasized in the vertical direction. The above is the description of the case where the brightness gradually increases from the low brightness as shown in the upper part of FIG. Furthermore, a case where the brightness gradually decreases from the high brightness as shown in the upper part of FIG. 3A will be described.

That is, this time, a signal waveform as shown in FIG. 7A is input as the video signal 102. When such a video signal 102 is input, the waveform shown in FIG. 7B is obtained as the video signal 109 output from the one horizontal period delay circuit 103. Further, this video signal 109 is delayed by one horizontal period delay circuit 104.
7 (c) as the video signal 110 when delayed by
A waveform as shown in is obtained. These video signals 102,10
Input 9,110 into the coefficient multipliers 105, 106, 107 respectively and multiply the coefficients by
When the outputs are added by the adder 108, a vertical contour detection signal 116 as shown in FIG. 7 (d) can be obtained. Then, after the vertical contour detection signal 116 is converted into an absolute value by the absolute value circuit 111 to remove the code, when it is compared with a specific constant value level 113 in the comparator 112, the comparator 1
The signal output from 12 becomes a signal which becomes'H 'level only at the vertical contour position, and is input to the switching circuit 114. At this time, the waveform of the absolute value circuit 111 output is the same as the waveform of the comparator 112 output, and is shown in FIG. 7 (f). As described above, the switching means 114 selects and outputs the video signal 109 when the output from the comparator is the “H” level as shown in FIG. 7 (g), and the video signal 109 when the output is the “L” level. Since 110 is selected and output, the vertical contour emphasis signal 115 output from the switching circuit 114 has a waveform as shown in FIG. 7 (e). That is, also in this case, it is possible to obtain a signal with a reduced brightness level transient region as the vertical contour emphasis signal 115, and it is possible to emphasize the vertical contour portion of the image.

FIG. 8A is an explanatory view schematically showing an image when the present invention is carried out. As can be seen from comparison with FIG. 3 (a), it can be seen that the transient region of the brightness level is reduced and the vertical contour portion is more emphasized. Also,
As shown in FIG. 8 (b), the brightness level does not increase or decrease more than that shown in FIG. 3 (b), so that it is understood that there is no concern about blooming. further,
The beam spot size also does not become thick.

〔The invention's effect〕

According to the present invention, since the vertical contour portion of an image can be emphasized without increasing or decreasing the brightness level, blooming due to the increase or decrease of the brightness level, which is a drawback of the prior art, is solved, and It is possible to enhance the contour in the vertical direction without causing a change in the amplitude level, and there is an effect that a good sharpness improvement can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional vertical contour enhancement circuit, and FIG. 3 (a) is a schematic diagram showing an image before vertical contour enhancement. FIG. 3 (b) is a graph showing the luminance in the vertical direction of the image, FIG. 4 is a waveform diagram showing the signal waveform of the main part of FIG. 2,
FIG. 5 (a) is an explanatory diagram schematically showing an image after vertical contour enhancement according to the conventional technique, and FIG. 5 (b) is a graph showing the luminance of the image in the vertical direction, FIG. FIG. 7 is a waveform diagram showing a signal waveform of a main part of FIG. 1, FIG. 8 (a) is an explanatory diagram schematically showing an image after vertical contour enhancement according to the present invention, and FIG. b) is a graph showing the luminance of the image in the vertical direction. 101 ... vertical contour detection circuit 102 ... video signal 103, 104 ... 1 horizontal period delay circuit 105, 106, 107 ... coefficient unit 108 ... adder, 111 ... absolute value circuit 112 ... comparator, 114 ... switching circuit 115 ... ... Vertical contour enhancement signal

Claims (1)

[Claims] 1. A first delay unit for delaying an input video signal by a unit of a period that is an integral multiple of one horizontal period, and an output signal of the first delay unit that is a unit of an integral multiple of one horizontal period. Second delay means for delaying by, a video signal input to the first delay means, an output signal of the first delay means, and an output signal of the second delay means are respectively multiplied by a predetermined factor by a coefficient. A plurality of coefficient units, a calculating unit that calculates each output signal from the plurality of coefficient units, and a vertical contour that detects a vertical contour position of an image in the input video signal from the output signal of the calculating unit. A television receiver provided with a detecting means and a switching means for switching the respective output signals delayed by the first and second delay means in accordance with the output signal from the vertical contour detecting means. Vertical contour enhancement circuit.