JP2007266810A - Contour correction circuit - Google Patents

Abstract

A contour correction circuit for emphasizing a high frequency component of a video signal and correcting a contour of the video, without using a multiplier or the like, and applying a larger contour correction than before.
A delay circuit, an outline correction signal generation circuit, an inverse gamma correction circuit, and an adder are provided, and a gamma-corrected video signal is restored by the inverse gamma correction circuit and then contoured. By generating a contour correction signal by the correction signal generation circuit 3 and adding the gamma-corrected video signal delay-compensated by the delay circuit 2 and the contour correction signal by the adder 5, the contour correction can be greatly increased. .
[Selection] Figure 1

Description

  The present invention relates to a contour correction circuit that enhances a high frequency component of a video signal and corrects a contour of the video.

  As one of the image quality adjustment circuits, there is a contour correction circuit that emphasizes a high frequency component of a video signal and corrects a contour of the video. In general, the video signal is previously subjected to gamma correction in consideration of the characteristics of the CRT so that a natural gradation can be obtained on the CRT. FIG. 12 is a configuration diagram illustrating an example of a contour correction signal generation circuit that generates a contour correction signal in the contour correction circuit. In FIG. 12, reference numeral 51 denotes an input terminal, which receives a gamma-corrected video signal (a). The Reference numerals 52 and 53 denote delay circuits, which respectively delay the input video signals for T periods and output them. Reference numerals 54 and 56 denote inversion circuits which invert the amplitudes of the input signals and output them. 55 is a double circuit which doubles the amplitude of the input signal and outputs it. 57 is an adder, and 58 is an output terminal.

  The operation waveforms of the contour correction signal generation circuit configured as described above will be described with reference to FIG. In FIG. 13, (a) is an input video signal whose amplitude is A, (b) is a signal whose amplitude is -A obtained by inverting the input signal (a) by the inverting circuit 56, and (c) is the input signal (a). Is delayed by the delay circuit 52 for T period, and the amplitude is doubled by the double circuit 55, and the signal having the amplitude of 2A is delayed by 2T periods by the delay circuit 52 and the delay circuit 53, and the inverting circuit 54 is further delayed. A signal whose amplitude is inverted by -A is -A. (E) is a contour correction signal, which is obtained by adding the signals (b), (c) and (d) by the adder 57. The contour correction signal (e) becomes a signal that swings at the amplitude A of the input video signal (a) for the T period and the positive side and the negative side at the edge of the video signal, that is, the edge side of the video signal, respectively.

  As a conventional contour correction circuit using such a contour correction signal generation circuit, there is an invention disclosed in Patent Document 1.

FIG. 11 shows a conventional contour correction circuit described in Patent Document 1. In FIG. In FIG. 11, reference numeral 1 denotes a video signal input terminal to which a video signal (a) subjected to gamma correction is input. Reference numeral 3 denotes the above-described contour correction signal generation circuit which receives the gamma-corrected video signal (a) and generates and outputs a contour correction signal (e). A delay circuit 2 delays and outputs the video signal (a) in order to compensate for the difference in delay time between the video signal (a) and the contour correction signal (e). An amplitude increase / decrease circuit 13 increases or decreases the amplitude of the contour correction signal (e) according to the level of the output signal of the delay circuit 2 and the positive side, negative side, and amplitude of the contour correction signal (e). (N) is output. An adder 5 adds the contour correction signal (n) and the output signal of the delay circuit 2 to obtain a contour-corrected video signal (p). Reference numeral 14 denotes an output terminal. The contour correction circuit configured as described above enables contour correction in which the difference between the sizes of the positive and negative contours is substantially eliminated during video reproduction on a cathode ray tube.
JP-A-6-296243

  However, as described above, the contour correction signal (e) is generated from the gamma-corrected video signal (a), so that the contour correction signal (e) is generated from the original signal before gamma correction. In some cases, the amplitude of the contour correction signal (e) becomes small.

  This point will be described with reference to FIGS. 2, 4, 5, and 7 for a case where the dynamic range of gamma correction is 8 bits (0 to 255). The gamma characteristic at this time is calculated by output = 255 × (input / 255) (1 / 2.2).

  (A), (e), and (p) in FIG. 2 are operation waveforms of the conventional contour correction circuit described in Patent Document 1, for example, the level of the original signal before gamma correction is changed from 100 to 150. When the amplitude is 50, the level of the video signal (a) after the gamma correction is changed from 167 to 201 and the amplitude is reduced to 34. The input / output characteristics of the gamma correction at this time are shown in FIG. As a result, the amplitude of the contour correction signal (e) generated by the above-described contour correction signal generation circuit 3 is also reduced to 34 on both the positive side and the negative side, and when the multiplier gain of the amplitude increase / decrease circuit 13 is 1, the contour correction is performed. Becomes a small video signal (p).

  For example, as shown in FIG. 3, when the level of the original signal before gamma correction is an amplitude 20 that changes from 180 to 200, the level of the video signal (a) that has been gamma corrected is 218 to 229. And the amplitude becomes as small as 11. The input / output characteristics of the gamma correction at this time are shown in FIG. Also in this case, the amplitude of the contour correction signal (e) generated by the contour correction signal generation circuit 3 is as small as 11 on both the positive side and the negative side. Similarly, when the multiplier gain of the amplitude increase / decrease circuit 13 is set to 1, The video signal (p) is corrected slightly.

  The present invention solves the above-described conventional problems, and by generating a contour correction signal after restoring the gamma-corrected video signal (a) with an inverse gamma correction circuit, the amplitude of the contour correction signal is increased. An object of the present invention is to provide a contour correction circuit that requires a large amount of contour correction compared to the prior art without using a multiplier.

  In order to solve the above-described problems, a first contour correction circuit according to the present invention receives a gamma-corrected video signal and performs a reverse gamma correction circuit, and a contour from the output signal of the reverse gamma correction circuit. A contour correction signal generation circuit that generates a correction signal, a delay circuit that delays the gamma-corrected video signal for a predetermined time, an output that adds the output signal of the contour correction signal generation circuit, and the output signal of the delay circuit Have a container.

In order to achieve this object, the second contour correction circuit of the present invention receives a gamma-corrected video signal and performs reverse gamma correction, and an average of output signals of the reverse gamma correction circuit. An average luminance detection circuit for detecting luminance, a selection circuit that selects the gamma-corrected video signal and an output signal of the inverse gamma correction circuit according to a detection result of the average luminance detection circuit; and the selection circuit A contour correction signal generation circuit for generating a contour correction signal from the output signal of
A delay circuit that delays the gamma-corrected video signal for a predetermined time; an output signal of the contour correction signal generation circuit; and an adder that adds the output signal of the delay circuit.

  In order to achieve this object, the third contour correction circuit of the present invention receives a gamma-corrected video signal and performs reverse gamma correction, and a contour from the output signal of the reverse gamma correction circuit. A first contour correction signal generation circuit that generates a correction signal, a second contour correction signal generation circuit that generates a contour correction signal from the gamma-corrected video signal, and an output of the first contour correction signal generation circuit A signal level determination circuit that receives a signal and an output signal of the second contour correction signal generation circuit, and determines and outputs a signal level of a larger positive side and a smaller negative side of the input contour correction signal; A delay circuit that delays the gamma-corrected video signal for a predetermined time, an output signal of the signal level determination circuit, and an adder that adds the output signal of the delay circuit.

  The contour correction circuit according to the present invention increases the amplitude of the contour correction signal by returning the gamma-corrected video signal to the original by the inverse gamma correction circuit, thereby using a multiplier or the like. In addition, there is an effect that the contour correction can be greatly applied as compared with the conventional case.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a contour correction circuit according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a video signal input terminal to which the gamma-corrected video signal is input. Reference numeral 4 denotes an inverse gamma correction circuit which inputs a gamma-corrected video signal and performs inverse gamma correction. Reference numeral 3 denotes a contour correction signal generation circuit which receives the output signal of the inverse gamma correction circuit 4 and generates a contour correction signal. Reference numeral 2 denotes a delay circuit for inputting the gamma-corrected video signal, delaying it for a predetermined time, and outputting it. Reference numeral 5 denotes an adder which inputs and adds the output signal of the contour correction signal generation circuit 3 and the output signal of the delay circuit 2. 6 is an output terminal.

  The operation of the contour correction circuit configured as described above will be described with reference to FIGS. 1, 2, 3, 4, 5, 6, and 7. In FIG. 1, the same components as those in FIG. For simplicity, the case where the dynamic range of inverse gamma correction is 8 bits (0 to 255) will be described. The inverse gamma characteristic at this time is calculated by output = 255 × (input / 255) 2.2.

  (A), (f), (g), and (h) in FIG. 2 are operation waveforms of the contour correction circuit shown in FIG. 1. As an example, the level of the original signal before gamma correction changes from 100 to 150. The case where the amplitude is 50 will be described.

  As described above, the level of the gamma-corrected video signal (a) input from the video signal input terminal 1 changes from 167 to 201 and the amplitude is reduced to 34. The inverse gamma correction circuit 4 performs inverse gamma correction on the gamma-corrected video signal (a), and returns the signal having the amplitude 34 changing from 167 to 201 to the original signal having the amplitude 50 changing from 100 to 150. Output as an inverse gamma correction circuit output signal (f). FIG. 5 shows the input / output characteristics of gamma correction and inverse gamma correction at this time. The contour correction signal generation circuit 3 receives an inverse gamma correction circuit output signal (f) having an amplitude of 50, and outputs contour correction signals (g) having positive and negative amplitudes of 50, respectively. The delay circuit 2 receives the video signal (a) that has been gamma-corrected, and outputs the video signal (a) after a predetermined time delay to compensate for the delay time of the inverse gamma correction circuit 4 and the contour correction signal generation circuit 3. The adder 5 receives the output signal of the delay circuit 2 and the contour correction signal (g), and outputs a video signal (h) obtained by adding the contour correction signal of amplitude 50 to the positive side and the negative side to the video signal of amplitude 34. Output from terminal 6. Compared with the output signal (p) of the conventional contour correction circuit, the contour correction is greatly applied.

  For example, as shown in FIG. 3, when the level of the original signal before gamma correction is an amplitude 20 that changes from 180 to 200, the level of the video signal (a) that has been gamma corrected is as described above. Furthermore, the amplitude changes from 218 to 229, and the amplitude becomes as small as 11. The video signal (a) having an amplitude as small as 11 is subjected to inverse gamma correction by the inverse gamma correction circuit 4 and returned to the original signal of amplitude 20 that changes from 180 to 200. The input / output characteristics of gamma correction and inverse gamma correction at this time are shown in FIG. The amplitude of the contour correction signal (g) generated by the contour correction signal generation circuit 3 is 20 on both the positive side and the negative side, and the adder 5 outputs a video signal (h) on which the contour correction is larger than in the conventional case. Output from terminal 6. In this case as well, the contour correction is much larger than the output signal (p) of the conventional contour correction circuit.

  For example, as shown in FIG. 4, when the level of the original signal before gamma correction is an amplitude 50 that changes from 20 to 70, the level of the video signal (a) that has been gamma corrected is 80 to 142. And the amplitude increases to 62. The video signal (a) whose amplitude has increased to 62 is subjected to inverse gamma correction by the inverse gamma correction circuit 4 and returned to the original signal of amplitude 50 that changes from 20 to 70. The input / output characteristics of gamma correction and inverse gamma correction at this time are shown in FIG. The amplitude of the contour correction signal (g) generated by the contour correction signal generation circuit 3 is 50 on both the positive side and the negative side. In this case, the adder 5 uses the video signal (h ) Is output from the output terminal 6.

  As described above, the gamma-corrected video signal is returned to the original signal by the inverse gamma correction circuit and then the contour correction signal is generated, thereby increasing the amplitude of the contour correction signal and performing contour correction compared to the conventional case. There is an effect that it can be greatly applied. However, it may take a small amount depending on the level of the input video signal.

(Embodiment 2)
FIG. 8 is a block diagram showing a configuration of a contour correction circuit according to the second embodiment of the present invention. In FIG. 8, reference numeral 1 denotes a video signal input terminal to which a gamma-corrected video signal is input. Reference numeral 4 denotes an inverse gamma correction circuit which inputs a gamma-corrected video signal and performs inverse gamma correction. Reference numeral 9 denotes an average luminance detection circuit which receives the output signal of the inverse gamma correction circuit 4 and detects the average luminance. Reference numeral 10 denotes a selection circuit which inputs the gamma-corrected video signal and the output signal of the inverse gamma correction circuit 4 and selects one of the input signals according to the detection result of the average luminance detection circuit 9. Select and output. Reference numeral 3 denotes a contour correction signal generation circuit which receives the output signal of the selection circuit 10 and generates a contour correction signal. Reference numeral 2 denotes a delay circuit for inputting the gamma-corrected video signal, delaying it for a predetermined time, and outputting it. Reference numeral 5 denotes an adder which inputs and adds the output signal of the contour correction signal generation circuit 3 and the output signal of the delay circuit 2. 6 is an output terminal.

  The operation of the contour correction circuit configured as described above will be described with reference to FIGS. 2, 3, 4, and 8. In FIG. 8, the same components as those in FIG. For simplicity, the case will be described where the dynamic range of inverse gamma correction is 8 bits (0 to 255).

  (A), (f), (j), (k), and (h) in FIG. 2 are operation waveforms of the contour correction circuit shown in FIG. 8, and as described above, as an example, the original signal before gamma correction is performed. The case where the level is 50 and the amplitude changes from 100 to 150 will be described. The level of the gamma-corrected video signal (a) input from the video signal input terminal 1 changes from 167 to 201, and the amplitude is reduced to 34. The inverse gamma correction circuit 4 performs inverse gamma correction on the gamma-corrected video signal (a), and converts the signal having the amplitude 34 changing from 167 to 201 into the original signal having the amplitude 50 changing from 100 to 150. Return to the inverse gamma correction circuit output signal (f). The average luminance detection circuit 9 receives the output signal of the inverse gamma correction circuit 4, calculates the average luminance, and when the average luminance is high (here, 50 or more), “H” is low (here, less than 50). ) Output “L”. In this example, since the average luminance is 125, the output of the average luminance detection circuit 9 is “H”. The selection circuit 10 receives the video signal (a) subjected to the gamma correction and the output signal (f) of the inverse gamma correction circuit 4, and when the output signal of the average luminance detection circuit 9 is "H", the reverse gamma correction circuit 4 When the output signal (f) is “L”, the gamma-corrected video signal (a) is output as the output signal (j). In this example, since the output signal of the average luminance detection circuit 9 is “H”, the output signal (f) of the inverse gamma correction circuit 4 is selected as the output signal (j) of the selection circuit 10.

  The contour correction signal generation circuit 3 receives the inverse gamma correction circuit output signal (f) having an amplitude of 50 output from the selection circuit 10 and outputs a contour correction signal (k) having an amplitude of 50 on the positive side and 50 on the negative side. To do. The delay circuit 2 receives the video signal (a) that has been gamma-corrected, and outputs the video signal (a) after a predetermined time delay to compensate for the delay time of the inverse gamma correction circuit 4 and the contour correction signal generation circuit 3. The adder 5 receives the output signal of the delay circuit 2 and the contour correction signal (k), and outputs a video signal (h) obtained by adding the contour correction signal of amplitude 50 to the positive side and negative side to the video signal of amplitude 34. Output from terminal 6. Compared with the output signal (p) of the conventional contour correction circuit, the contour correction is greatly applied.

  Also, for example, as shown in FIG. 3, when the level of the original signal before gamma correction is an amplitude 20 that changes from 180 to 200, as described above, the level of the video signal (a) that has been gamma corrected. Changes from 218 to 229 and the amplitude decreases to 11. The video signal (a) having an amplitude as small as 11 is subjected to inverse gamma correction by the inverse gamma correction circuit 4 and returned to the original signal of amplitude 20 that changes from 180 to 200. The average luminance detection circuit 9 outputs “H” because the average luminance of the output signal (f) of the inverse gamma correction circuit 4 is 190. Since the output signal (j) of the selection circuit 10 is “H”, the output signal (f) of the inverse gamma correction circuit 4 is selected and input to the contour correction signal generation circuit 3. The Therefore, the amplitude of the contour correction signal (k) generated by the contour correction signal generation circuit 3 is 20 on both the positive side and the negative side, and the adder 5 is a video signal (h) on which the contour correction is larger than that of the conventional art. Is output from the output terminal 6. In this case as well, the contour correction is much larger than the output signal (p) of the conventional contour correction circuit.

  For example, as shown in FIG. 4, when the level of the original signal before gamma correction is an amplitude 50 that changes from 20 to 70, as described above, the amplitude of the video signal (a) that has been gamma corrected, as described above. Increases to 62. The video signal (a) whose amplitude has increased to 62 is subjected to inverse gamma correction by the inverse gamma correction circuit 4 and returned to the original signal of amplitude 50 that changes from 20 to 70.

  The average luminance detection circuit 9 outputs “L” because the average luminance of the output signal (f) of the inverse gamma correction circuit 4 is 45. As the output signal (j) of the selection circuit 10, since the output signal of the average luminance detection circuit 9 is "L", the video signal (a) whose amplitude has been increased to 62 is selected by the gamma correction, and the contour correction signal generation circuit is selected. 3 is input. Therefore, the amplitude of the contour correction signal (k) generated by the contour correction signal generation circuit 3 is 62 on both the positive side and the negative side, and the adder 5 is subject to a large amount of contour correction like the conventional video signal (p). The video signal (h ′) is output from the output terminal 6.

  As described above, the gamma-corrected video signal is returned to the original signal by the inverse gamma correction circuit and then the contour correction signal is generated, thereby increasing the amplitude of the contour correction signal and performing contour correction compared to the conventional case. There is an effect that it can be greatly applied. Further, by detecting the average luminance of the inverse gamma correction circuit and generating a contour correction signal by switching to a video signal subjected to gamma correction when the average luminance is low, the contour correction can always be greatly increased.

  In addition, although the detection level of average brightness was demonstrated with the fixed value of 50, it is good also as a structure which can be set from the outside.

(Embodiment 3)
FIG. 9 is a block diagram showing a configuration of a contour correction circuit according to the third embodiment of the present invention. In FIG. 9, reference numeral 1 denotes a video signal input terminal to which a gamma-corrected video signal is input. Reference numeral 4 denotes an inverse gamma correction circuit which inputs a gamma-corrected video signal and performs inverse gamma correction. Reference numeral 3 denotes a first contour correction signal generation circuit which receives an output signal of the inverse gamma correction circuit 4 and generates a contour correction signal. Reference numeral 11 denotes a second contour correction signal generation circuit which receives the gamma-corrected video signal and generates a contour correction signal. A signal level determination circuit 12 receives the output signal of the first contour correction signal generation circuit 3 and the output signal of the second contour correction signal generation circuit 11, and the positive side of the input contour correction signal is The larger signal is judged on the negative side and the smaller signal level is outputted. Reference numeral 2 denotes a delay circuit for inputting the gamma-corrected video signal, delaying it for a predetermined time, and outputting it. Reference numeral 5 denotes an adder that inputs and adds the output signal of the signal level determination circuit 12 and the output signal of the delay circuit 2. 6 is an output terminal.

  The operation of the contour correction circuit configured as described above will be described with reference to FIGS. 2, 3, 4, 9, and 10. In FIG. 9, the same components as those in FIG. For simplicity, the case will be described where the dynamic range of inverse gamma correction is 8 bits (0 to 255).

  (A), (e), (f), (g), (m), and (h) in FIG. 2 are the operation waveforms of the contour correction circuit shown in FIG. A case where the amplitude of the original signal level changes from 100 to 150 and the amplitude is 50 will be described. The amplitude of the gamma-corrected video signal (a) input from the video signal input terminal 1 is as small as 34. The inverse gamma correction circuit 4 performs inverse gamma correction on the gamma-corrected video signal (a), and returns the signal having an amplitude of 34 to the original signal having an amplitude 50 that changes from 100 to 150. Output as an output signal (f). The first contour correction signal generation circuit 3 receives an inverse gamma correction circuit output signal (f) having an amplitude of 50, and outputs contour correction signals (g) having positive and negative amplitudes of 50, respectively. The second contour correction signal generation circuit 11 receives the video signal (a) subjected to the gamma correction with the amplitude 34, and outputs the contour correction signal (e) with the positive side amplitude and the negative side amplitude 34 respectively. The contour correction signals (e) and (g) are input to the signal level determination circuit 12.

  A block diagram of the signal level determination circuit 12 is shown in FIG. Assuming that the contour correction signal (e) input to the input terminal 21 is A and the contour correction signal (g) input to the input terminal 22 is B, the comparator 23 is “H” when A> B, otherwise “L” is output, and the comparator 24 outputs “H” when B> A, and “L” otherwise. The switch circuit 28 receives A and B, uses the output signals of the comparators 23 and 24 as control signals, and the control signal is short when “H” and open when “L”, and as a result, the larger one is output. The comparator 25 outputs “H” when A <B, otherwise outputs “L”, and the comparator 26 outputs “H” when B <A and otherwise outputs “L”. The switch circuit 29 inputs A and B, uses the output signals of the comparators 25 and 26 as control signals, and the control signal is short when “H” and open when “L”, and as a result outputs the smaller one. The positive / negative detection circuit 27 inputs A and B, and outputs “H” if either one is positive and “L” if negative. The selection circuit 30 selects and outputs the output signal of the switch circuit 28 when the control signal is “H” and the output signal of the switch circuit 29 when it is “L”, using the output signal of the positive / negative detection circuit 27 as a control signal. As a result of the above operation, a larger signal is determined on the positive side of the contour correction signals (e) and (g), and a smaller signal is determined on the negative side and is output from the output terminal 31. In this example, the signal level determination circuit 12 receives the contour correction signal (e) and the contour correction signal (g) having a positive and negative amplitude of 34, respectively, and the positive and negative amplitudes are 50 and 50 respectively. Is output from the output terminal 31 as an output signal (m).

  The adder 5 receives the output signal of the delay circuit 2 and the output signal (m) of the signal level determination circuit 12, and adds a contour correction signal having an amplitude of 50 to the positive side and the negative side to the video signal having an amplitude of 34. (H) is output from the output terminal 6. Compared with the output signal (p) of the conventional contour correction circuit, the contour correction is greatly applied.

  For example, as shown in FIG. 3, when the level of the original signal before gamma correction is an amplitude 20 that changes from 180 to 200, the level of the video signal (a) that has been gamma corrected is as described above. Furthermore, the amplitude changes from 218 to 229, and the amplitude becomes as small as 11. The video signal (a) having an amplitude as small as 11 is subjected to inverse gamma correction by the inverse gamma correction circuit 4 and returned to the original signal of amplitude 20 that changes from 180 to 200.

  The first contour correction signal generation circuit 3 receives an inverse gamma correction circuit output signal (f) having an amplitude of 20, and outputs contour correction signals (g) having an amplitude of 20 on the positive side and 20 on the negative side. The second contour correction signal generation circuit 11 receives the video signal (a) subjected to the gamma correction with the amplitude 11 and outputs the contour correction signal (e) having the positive and negative amplitudes of 11, respectively. The contour correction signals (e) and (g) are input to the signal level determination circuit 12. As described above, the signal level determination circuit 12 outputs a contour correction signal having positive and negative amplitudes of 20 as the output signal (m). The adder 5 receives the output signal of the delay circuit 2 and the output signal (m) of the signal level determination circuit 12, and adds a contour correction signal with an amplitude of 20 to the positive side and the negative side to the video signal with an amplitude of 11. (H) is output from the output terminal 6. Compared with the output signal (p) of the conventional contour correction circuit, the contour correction is greatly applied.

  For example, as shown in FIG. 4, when the level of the original signal before gamma correction is an amplitude 50 that changes from 20 to 70, the level of the video signal (a) that has been gamma corrected is as described above. Then, the amplitude changes from 80 to 142, and the amplitude increases to 62. The video signal (a) whose amplitude has increased to 62 is subjected to inverse gamma correction by the inverse gamma correction circuit 4 and returned to the original signal of amplitude 50 that changes from 20 to 70. As described above, the first contour correction signal generation circuit 3 outputs the contour correction signal (g) having the positive and negative amplitudes of 50 respectively, and the second contour correction signal generation circuit 11 And a contour correction signal (e) having a negative amplitude of 62 is output. As described above, the signal level determination circuit 12 outputs a contour correction signal having positive and negative amplitudes of 62 as the output signal (m). The adder 5 receives the output signal of the delay circuit 2 and the output signal (m) of the signal level determination circuit 12 and adds a contour correction signal of amplitude 62 to the positive side and negative side to the video signal of amplitude 62. (H ′) is output from the output terminal 6. Similar to the output signal (p) of the conventional contour correction circuit, the contour correction is greatly applied.

  As described above, the gamma-corrected video signal is returned to the original signal by the inverse gamma correction circuit and then the contour correction signal is generated, thereby increasing the amplitude of the contour correction signal and performing contour correction compared to the conventional case. There is an effect that it can be greatly applied. Further, the level of the contour correction signal generated from the gamma-corrected video signal and the level of the contour correction signal generated from the inverse gamma-corrected video signal are determined by the signal level determination circuit, thereby converting the contour correction signal having a large amplitude into the video signal. It can be added, and the contour correction can always be greatly increased.

  The contour correction circuit according to the present invention increases the amplitude of the contour correction signal by returning the gamma-corrected video signal to the original by the inverse gamma correction circuit, thereby using a multiplier or the like. Therefore, it is possible to apply a large amount of contour correction as compared with the prior art, which is useful as a contour correction circuit that emphasizes the high frequency component of the video signal and corrects the video contour.

The block diagram which shows the structure of the outline correction circuit in Embodiment 1 of this invention. Operation waveform diagram for explaining the operation of the contour correction circuit Operation waveform diagram for explaining the operation of the contour correction circuit Operation waveform diagram for explaining the operation of the contour correction circuit Diagram showing gamma characteristics and inverse gamma characteristics Diagram showing gamma characteristics and inverse gamma characteristics Diagram showing gamma characteristics and inverse gamma characteristics The block diagram which shows the structure of the outline correction circuit in Embodiment 2 of this invention. The block diagram which shows the structure of the outline correction circuit in Embodiment 3 of this invention. Block diagram showing configuration of signal level determination circuit Block diagram showing the configuration of a conventional contour correction circuit Block diagram showing an example of a contour correction signal generation circuit Operation waveform diagram for explaining the operation of the contour correction signal generation circuit

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Video signal input terminal 2 Delay circuit 3 Contour correction signal generation circuit 4 Inverse gamma correction circuit 5 Adder 6 Output terminal 9 Average brightness detection circuit 10 Selection circuit 11 Second contour correction signal generation circuit 12 Signal level determination circuit 21, 22 , 51 Input terminal 23, 24, 25, 26 Comparator 27 Positive / negative detection circuit 28, 29 Switch circuit 30 Selection circuit 31, 58 Output terminal 52, 53 Delay circuit 54, 56 Inversion circuit 55 Double circuit 57 Adder

Claims (5)

A reverse gamma correction circuit that inputs a gamma corrected video signal and performs reverse gamma correction;
A contour correction signal generation circuit that inputs an output signal of the inverse gamma correction circuit and generates a contour correction signal;
A delay circuit for inputting the gamma-corrected video signal and delaying and outputting the signal for a predetermined time;
A contour correction circuit comprising: an output signal of the contour correction signal generation circuit; and an adder that inputs, adds and outputs the output signal of the delay circuit. A reverse gamma correction circuit that inputs a gamma corrected video signal and performs reverse gamma correction;
An average luminance detection circuit that receives an output signal of the inverse gamma correction circuit and detects average luminance;
A selection circuit that inputs the gamma-corrected video signal and an output signal of the inverse gamma correction circuit, and selects and outputs one of the input signals according to the detection result of the average luminance detection circuit;
An outline correction signal generation circuit that inputs an output signal of the selection circuit and generates an outline correction signal;
A delay circuit for inputting the gamma-corrected video signal and delaying and outputting the signal for a predetermined time;
A contour correction circuit comprising: an output signal of the contour correction signal generation circuit; and an adder that inputs, adds and outputs the output signal of the delay circuit. A reverse gamma correction circuit that inputs a gamma corrected video signal and performs reverse gamma correction;
A first contour correction signal generation circuit that receives the output signal of the inverse gamma correction circuit and generates a contour correction signal;
A second contour correction signal generation circuit that inputs the gamma corrected video signal and generates a contour correction signal;
The output signal of the first contour correction signal generation circuit and the output signal of the second contour correction signal generation circuit are input, and the positive side of the input contour correction signal is larger and the negative side is smaller. A signal level judgment circuit for judging and outputting the level;
A delay circuit for inputting the gamma-corrected video signal and delaying and outputting the signal for a predetermined time;
An outline correction circuit comprising: an adder that inputs, adds and outputs the output signal of the signal level determination circuit and the output signal of the delay circuit. A reverse gamma correction circuit that inputs a gamma corrected video signal and performs reverse gamma correction;
A contour correction signal generation circuit that adjusts the correction amount of the contour correction signal according to the amount of change in luminance of the input video signal;
A delay circuit for outputting a gamma-corrected video signal with a predetermined time delay;
An adder that adds the video signal output from the delay circuit and the contour correction signal output from the contour correction signal generation circuit;
A contour correction circuit characterized by increasing the amount of change in luminance of a video signal subjected to gamma correction by the inverse gamma correction circuit and increasing the correction amount of the contour correction signal output from the contour correction signal generation circuit. . 5. The contour correction signal generation circuit receives an output signal of an inverse gamma correction circuit and generates a contour correction signal only when the luminance of the video signal subjected to gamma correction is equal to or higher than a predetermined value. The contour correction circuit described.

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