Contour correction device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a contour correction device, and more specifically, relates to a contour correction device for improving the image quality of an output video signal by correcting the contour of an input video signal.

【0002】

[Conventional technology]

When viewing a video signal on a display in a conventional television receiver, the video signal input to the display (in order to improve the deterioration of the frequency characteristics of the video signal processed by each circuit before the display and the visual image quality) A contour correction circuit is used to extract a high-frequency component of (brightness signal), add the high-frequency component to the input video signal, and make the rising and falling edges of the added video signal steep.

【0003】

This conventional contour correction circuit will be described with reference to FIG.

【0004】

In FIG. 5, the contour correction circuit 1 extracts a high frequency component (contour component) of the video signal (brightness signal) and outputs the high frequency component to the coring 3 with a bandpass filter (B, P, F) 2. Coring 3 that outputs the high frequency component to the adder 4 according to the level of the high frequency component extracted by the bandpass filter 2 and output by adding the high frequency component input from the coring 3 to the original input video signal. It is composed of an adder 4 to be used.

【0005】

The state of each signal waveform in the portions a, b, and c in the figure of the contour correction circuit 1 is shown in FIGS. 6 (a) to 6 (c). In FIG. 6, (a) shows the input video signal waveform of the part a of FIG. 5, (b) shows the case where the high frequency component of the part b of FIG. 5 is output, and (c) shows the case of FIG. The video signal waveform after the addition of the c part is shown.

【0006】

By adding the emphasis signal (high frequency component) to the input video signal and outputting it to the display in this way, the outline of the image displayed on the display is emphasized, and the visual image quality can be improved. In such a contour correction circuit 1, in order to avoid emphasizing low-level high-frequency components such as noise components contained in the input video signal, the gain is set to 0 for high-frequency components below a certain level by coring 3. "" To avoid contour enhancement, and for high-frequency components above a certain level, the gain is set to "1" to enhance the contour.

【0007】

[Problems to be Solved by the Invention]

However, in such a conventional contour correction circuit, for high frequency components below a certain level by coring, the gain is set to "0" to avoid contour enhancement, and for high frequency components above a certain level. Has a configuration in which contour enhancement is performed with a gain of "1" and this contour enhancement signal is added to the input image signal. Therefore, for high-frequency components close to a certain level, the portion where contour enhancement is performed and the contour Some parts are not emphasized, the displayed image becomes unnatural, and the outline-enhanced output image signal has an undershoot on the black side as shown in Fig. 6 (c) above. At the same time, overshoot occurs on the white side, which is closer to the white level or black level than the input image signal, and a white band is generated on the white side of the edge of the displayed image, or a black band is generated on the black side. There is a problem that the image quality is deteriorated.

【0008】

In addition, since all high-frequency components above a certain level are uniformly contour-enhanced, even high-frequency and low-level high-frequency components that cannot be removed by coring are uniformly contour-enhanced, which causes unnecessary flicker in the displayed image. Was generated, which was a cause of deterioration of image quality.

【0009】

Therefore, an object of the present invention is to provide a contour correction device that appropriately sets the contour correction amount according to the level of the contour component extracted from the luminance signal.

【0010】

[Means for solving problems]

A contour extraction means for extracting the contour component of the input luminance signal, an enhancement means for emphasizing the contour component based on the level of the contour component extracted by the contour extraction means, and a contour component emphasized by the enhancement means. It is provided with an over-emphasis correction means for correcting the over-emphasized portion of the above, and a synthesis means for synthesizing and outputting the input luminance signal and the emphasis signal whose over-emphasis portion is corrected by the over-emphasis correction means. It is a feature.

【0011】

Further, the enhancement means according to claim 1 performs non-linear correction so that the correction amount increases as the level of the contour component extracted by the contour extraction means increases, and the over-emphasis correction means is described. The characteristic is that the correction amount is gradually reduced in the section where the input luminance signal level reaches the black level and the white level, and the non-linear correction is performed so that the correction amount is constant in the section between the black level and the white level.

【0012】

[Action]

In the present invention, a contour component is extracted from a luminance signal input by the contour extracting means, the contour component is emphasized by the enhancing means based on the level of the extracted contour component, and the emphasized contour component is supported. The over-emphasis portion is corrected by the over-emphasis correction means, and the input luminance signal and the over-emphasis portion corrected emphasis signal are combined and output by the synthesis means. Further, in the enhancement means, non-linear correction is performed so that the correction amount increases as the level of the extracted contour component increases, and in the over-emphasis correction means, the section where the input luminance signal level reaches the black level and the white level. The correction amount is gradually reduced, and the non-linear correction can be performed so that the correction amount is constant in the section between the black level and the white level.

【0013】

Therefore, the contour enhancement can be appropriately performed according to the level of the contour component of the input luminance signal, and the image quality of the displayed image can be improved.

【0014】

[Example]

Hereinafter, examples will be described with reference to FIGS. 1 to 4.

【0015】

1 to 4 are diagrams showing an embodiment of the contour correction device of the present invention.

【0016】

First, the configuration will be described. FIG. 1 is a block configuration diagram of the contour correction device 10. In this figure, the contour correction device 10 is composed of a horizontal bandpass filter 11, a vertical bandpass filter 12, an adder 13, an absolute value amplifier 14, a non-linear processing circuit 15, 16, a multiplier 17, 18 and an adder 19. To.

【0017】

The horizontal bandpass filter 11 extracts the high frequency component in the horizontal direction from the input video signal (luminance signal) a and outputs it to the adder 13, and the vertical bandpass filter 12 extracts the input video signal (luminance signal). The high frequency component in the vertical direction is extracted from and output to the adder 13. The adder 13 adds the horizontal high frequency component input from the horizontal bandpass filter 11 and the vertical high frequency component input from the vertical bandpass filter 12, and adds the addition result to the absolute value amplifier 14 and the multiplier 17. Output to.

【0018】

The absolute value amplifier 14 obtains the absolute value | x | of the high frequency component b (referred to as x for convenience), which is the addition result input from the adder 13, and outputs it to the nonlinear processing circuit 15. The non-linear processing circuit 15 has the characteristics shown in FIG. 2 based on the absolute value | x | input from the absolute value amplifier 14, that is, the correction coefficient α whose value increases as the absolute value | x | increases. Select and output to multiplier 17. The non-linear processing circuit 16 has the characteristics shown in FIG. 3 based on the level change of the input video signal (luminance signal) a (referred to as y for convenience), that is, the level of the luminance signal y is the black level and the white level. In the section up to, the value gradually decreases, and in the section between the black level and the white level, the correction coefficient β whose value is constant is selected and output to the multiplier 18.

【0019】

The multiplier 17 multiplies the addition result b of the horizontal and vertical high-frequency components input from the adder 13 by the correction coefficient α input from the nonlinear processing circuit 15, and outputs the multiplication result c to the multiplier 18. .. The multiplier 18 multiplies the multiplication result c input from the multiplier 17 by the correction coefficient β input from the non-linear processing circuit 16, and outputs the multiplication result, that is, the emphasis signal d for emphasizing the contour to the adder 19. .. The adder 19 adds the emphasis signal d input from the multiplier 18 to the input video signal, and outputs the addition result as an output video signal.

【0020】

The absolute value amplifier 14 and the non-linear circuit 15 correspond to the coring 3 in the conventional contour correction circuit 1.

【0021】

Next, the operation of this embodiment will be described.

【0022】

In this embodiment, when a video signal a (brightness signal) as shown in FIG. 4A is input to the contour correction device 10, the input video signal a is a horizontal bandpass filter 11 and a vertical band. It is input to the pass filter 12, the nonlinear processing circuit 16 and the adder 19, and the horizontal and vertical high frequency components are extracted from the input video signal a by the horizontal bandpass filter 11 and the vertical bandpass filter 12, and the extracted horizontal The high frequency components in the direction and the direction perpendicular to the direction are added by the adder 13, and the addition result b as shown in FIG. 4 (b) is obtained.

【0023】

The absolute value | x | is obtained from the addition result b by the absolute value amplifier 14, and the correction coefficient α shown in FIG. 2 is selected by the nonlinear processing circuit 15 based on the obtained absolute value | x |, and the multiplier is used. It is output to 17. Further, the video signal y input to the nonlinear processing circuit 16 is output to the multiplier 18 by selecting the correction coefficient β shown in FIG. 3 based on the level change of the video signal y.

【0024】

The addition result b and the correction coefficient α are multiplied by the multiplier 17, and the multiplication result c and the correction coefficient β are multiplied by the multiplier 18, that is, the emphasis signal d is obtained. This emphasis signal d is added to the input video signal a by the adder 19, and is output to a cathode ray tube (not shown) as a contour-corrected output video signal as shown in FIG. 4 (c).

【0025】

Therefore, the high-frequency component extracted from the input video signal is corrected by multiplying the correction coefficient α according to the increase of the high-frequency component extracted by the nonlinear processing circuit 15, and the input video signal is corrected according to the black level, white level, and intermediate level. By multiplying the correction coefficient β and correcting it to create an emphasized signal, the black side undershoot and the white side overshoot like the outline-enhanced video signal shown in FIG. 6 (c) above. It is possible to create an outline-enhanced video signal as shown in Fig. 4 (c) without the above, and avoiding the outline enhancement of unnecessary high-frequency components, it is possible that unnecessary flicker occurs in the displayed image. This can be prevented and the image quality of the displayed image can be improved.

【0026】

As described above, the contour correction device 10 extracts the horizontal and vertical high frequency components from the input video signal by the horizontal band pass filter 11 and the vertical band pass filter 12, and the horizontal and vertical high frequency components are added by the multiplier 13. Add, find the absolute value | x | from the addition result with the absolute value amplifier 14, select the absolute value | x | with the non-linear processing circuit 15, that is, the correction coefficient α based on the level of the high frequency component, and use the multiplier 17 to select the correction coefficient α. By multiplying the high frequency component by the correction coefficient α, a natural contour enhancement component corresponding to the level of the high frequency component can be output. Further, the nonlinear processing circuit 16 can correct the over-emphasis component by selecting the correction coefficient β based on the level change of the video signal and multiplying the contour enhancement component by the correction coefficient β with the multiplier 18. By adding this corrected contour enhancement signal to the input video signal with the adder 19, it is possible to add the enhancement signal that appropriately enhances the contour to the input video signal according to the level of the contour component extracted from the input luminance signal. , The image quality of the displayed image can be improved.

【0027】

[Effect of the invention]

According to the present invention, a contour component is extracted from an input luminance signal, the contour component is emphasized by an enhancing means based on the level of the extracted contour component, and an overemphasized portion of the emphasized contour component is emphasized. The input luminance signal and the emphasis signal corrected by the over-emphasis portion are combined by the synthesis means and output. Further, in the enhancement means, non-linear correction is performed so that the correction amount is increased according to the increase in the level of the extracted contour component, and in the over-emphasis correction means, the section where the input luminance signal level reaches the black level and the white level is Since the correction amount is gradually reduced and the non-linear correction is performed so that the correction amount is constant in the section between the black level and the white level, the contour enhancement is appropriately performed according to the level of the contour component of the input luminance signal. This can be done and the image quality of the displayed image can be improved.

[Simple explanation of drawings]

[Figure 1]

The block block diagram of the contour correction apparatus of this invention.

[Figure 2]

The figure which shows the characteristic of the correction coefficient α processed by the nonlinear processing circuit of FIG.

[Fig. 3]

The figure which shows the characteristic of the correction coefficient β processed by the nonlinear processing circuit of FIG.

[Fig. 4]

The figure which shows the signal waveform in each part of the contour correction apparatus of FIG.

[Fig. 5]

Circuit block diagram of a conventional contour correction circuit.

[Fig. 6]

The figure which shows the signal waveform in each part of the contour correction circuit of FIG.

[Explanation of symbols]

10 Contour correction device 11 Horizontal bandpass filter 12 Vertical bandpass filter 13, 19 adder 14 Absolute value amplifier 15, 16 Non-linear processing circuit 17, 18 multiplier