JPH0923356A - Outline correction circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a quite natural picture which has a distinct outline and has fine details emphasized by providing plural differentiating circuits, limiters, correlation logics, and addition circuits. SOLUTION: A signal A inputted from an input terminal 1 is subjected to quadratic differential in a circuit 2, and its high band component is taken out as a signal B and is sent to a limiter 3. The signal B has the amplitude limited by the limiter 3 and is outputted as a signal C. A circuit 4 receives the signal C and subjects it to differential to output a signal D. The signal A delayed by a circuit 7 is inputted to a circuit 9 and is outputted as a signal E. A correlation logic 5 receives the input of signals D and E; and only when both of signals have the same polarity, this logic 5 outputs the signal of the circuit 4 as a signal F. A signal G is generated in a circuit 6 by the signal F. The signal G is added to the signal A passing a circuit 8 by a circuit 10 to generate a signal H after outline correction, and this signal H is outputted to a terminal 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour correction circuit for performing image enhancement on a video signal of a VTR, a television, a television camera or the like.

[0002]

2. Description of the Related Art Conventionally, there has been a method of using an aperture circuit as one of the methods for correcting the contour of an image. This is to make a signal delayed by a short time (for example, Δt) and repeat addition and subtraction to make the contour of the image. To preshoot and overshoot.

FIG. 12 shows a first conventional example of a conventional contour correction circuit, and is a block diagram of a horizontal contour correction circuit in video luminance signal processing. In the figure, 1A is an input terminal to which a signal I is input, 2A is a delay circuit that receives the input of the signal I, delays the signal I by Δt, and outputs a signal J,
The delay circuit 3A receives the signal J, delays the signal J by Δt and outputs the signal K, and 4A receives the signals I and J, subtracts the signal I from the signal J, and outputs the signal L. A subtracting circuit 5A for outputting outputs a signal J and a signal K, and a subtracting circuit for subtracting the signal K from the signal J and outputting a signal M. A 6A receives an input for the signal L and signal M and outputs a signal L and a signal. An adder circuit for adding M and outputting a signal N, an attenuator 7A for attenuating the signal N at a predetermined ratio and outputting a signal O,
8A receives the signals J and O and receives the signals J and O.
9A is a signal P
Is an output circuit for outputting.

The signal processing of the contour correction circuit configured as described above will be described below with reference to the waveform diagram of FIG.

First, when the video luminance signal I shown in FIG. 13 (a) is input to the input terminal 1A, the delay circuit 2A outputs the delay signal J shown in FIG. 13 (b) delayed by Δt, and the delay circuit 2A. 3A further outputs the delayed signal K shown in FIG. 13C, which is further delayed by Δt.

Next, the subtraction circuit 4A subtracts the video luminance signal I from the delay signal J to obtain the inverted waveform of the differential waveform of the video luminance signal I. The first differential signal L shown in FIG. 13 (d). Then, the subtraction circuit 5A outputs the second differential signal M shown in FIG. 13 (e), which is a waveform obtained by differentiating the delayed signal J by subtracting the signal K delayed by Δt from the delayed signal J. .

Next, the adder circuit 6A outputs the first differential signal L
And the second differential signal M are added, a third differential signal N shown in FIG. 13 (f), which is a waveform that vertically vibrates, is output.

Since the third differential signal N has the same amplitude as the level change amount of the video luminance signal I, the attenuator 7
The third differential signal N is attenuated by A to a predetermined ratio, for example, 1/2 to obtain the horizontal contour correction signal O shown in FIG.

Further, the adder circuit 8A outputs the corrected video luminance signal P shown in FIG. 13 (h), which is contour-corrected by adding the delay signal J and the horizontal contour correction signal O, and the corrected video luminance signal P is output. P is output from the output terminal 9A.

Further, FIG. 14 is a schematic view of JP-A-6-245103.
FIG. 3 is a block diagram of a horizontal contour correction circuit in the video luminance signal processing disclosed in Japanese Patent No. 312058, which is a second conventional example. In the figure, 1B is an input terminal to which a signal Q is input, and 2B is a signal Q.
And a delay circuit for delaying the signal Q by Δt and outputting a signal R, a delay circuit 3B for receiving the input of the signal R, delaying the signal R by Δt and outputting a signal S, 4
B receives the signal Q and the signal R, and receives the signal Q from the signal R
A subtraction circuit for subtracting the signal R and the signal S, and a subtraction circuit for subtracting the signal S from the signal R and outputting the signal U; and 6B, an input of the signal T and the signal U And an adder circuit 7 for adding the signal T and the signal U and outputting the signal V, 7 receives the input of the signal V, rectifies both sides of the signal V to detect the peak value of the signal V, and outputs the peak value signal. Is a detection circuit for outputting a signal V and a peak value signal, and a gain control circuit for setting a gain so that the peak value level of the peak value signal is inversely proportional and outputting a signal W. It is an output terminal that receives inputs of R and the signal W, adds the signal R and the signal W in the adder circuit 9B, and outputs the signal X.

The signal processing of the contour correction circuit configured as described above will be described below with reference to the waveform diagram of FIG.

When the video luminance signal Q shown in FIG. 15 (a) is input to the input terminal 1B, the delay circuit 2B outputs the delay signal R shown in FIG. 15 (b) delayed by Δt, and the delay circuit 3B outputs. Further, the delay signal S shown in FIG. 15C delayed by Δt is output.

Next, the subtraction circuit 4B subtracts the video luminance signal Q from the delay signal R to invert the differential waveform of the video luminance signal Q, which is the first waveform shown in FIG. 15 (d).
The differential circuit 5B outputs the differential signal T, and the subtraction circuit 5B subtracts the delay signal S from the delay signal R to form a waveform obtained by differentiating the delay signal R. The second differential signal U shown in FIG.
Is output.

Next, the first adder circuit 6B has a third differential shown in FIG. 15 (f), which is a waveform oscillating up and down by adding the first differential signal T and the second differential signal U. The signal V is output.

Next, when the detection circuit 7B receives the third differential signal V which is a horizontal contour correction signal, it performs double-wave rectification of the contour correction amount to detect the peak value, and the detected peak value is obtained. It is output to the gain control circuit 8B as a peak value signal.

Next, when the gain control circuit 8B receives the third differential signal V and the peak value signal, it receives the first differential signal T based on the peak value level of the third differential signal V.
The contour correction amounts of the parts a ₀ , b ₀ , c ₀ in FIG.
The gain setting is performed so that the contour correction amounts of the parts a ₁ , b ₁ , c _{1 in} the signal W shown in (g) are obtained, that is, the peak value level of the third differential signal V is inversely proportional. The gain setting signal W having the waveform shown in FIG.

Further, the adder circuit 9B performs contour correction by adding the delay signal R and the gain setting signal W in FIG.
The corrected video luminance signal X having the waveform shown in 5 (h) is output, and the corrected video luminance signal X is output from the output terminal 10B.

FIG. 16 is a block diagram of a contour correction circuit for a video color difference signal disclosed in JP-A-6-269021, which is a third conventional example. In the figure, 1C is an input terminal to which the (RY) color difference signal a shown in FIG. 17A is input, and 2C receives the input of the signal a, and the signal a is changed by Δt.
The delay circuit 3C that delays the signal b to output the signal b shown in FIG. 17B receives the signal b, and outputs the signal b by Δt.
It is a delay circuit which delays only by and outputs the signal c shown in FIG. Supplied to input terminal 1C (RY)
The color difference signal a is multiplied by 1/4 in the coefficient multiplying circuit 4C, and the (RY) color difference signal b output from the delay circuit 2C is multiplied by 1/2 in the coefficient multiplying circuit 5C and output from the delay circuit 3C. (RY) color difference signal c is 1 /
It is multiplied by 4.

The (RY) color difference signals output from the coefficient multiplication circuits 4C, 5C and 6C are output by the arithmetic circuit 7C.
The signals shown in FIG. 17D are obtained by subtracting the outputs of the coefficient multiplying circuits 4C and 6C from the output of the coefficient multiplying circuit 5C. After that, the output signal of the arithmetic circuit 7C is amplified by the amplifier circuit 8.
By being amplified to the required level by C,
A contour correction signal e as shown in FIG. 17 (e) is generated.

The contour correction signal e is added with the (RY) color difference signal b output from the delay circuit 2C by the adder circuit 9C, so that the contour is corrected as shown in FIG. -Y) The color difference signal f is generated.

The contour-corrected (RY) color difference signal f output from the adder circuit 9C is the minimum value output circuits 10C and 1C.
1C is supplied to each one input terminal. Of these, the minimum value output circuit 10C is supplied with the (RY) color difference signal a supplied to the input terminal 1C at the other input terminal thereof, and is supplied with the (RY) color difference signal to the input terminal 1C. The signal a and the (RY) color difference signal f output from the adding circuit 9C
And are compared in level, and the one with the lower level is output as shown in FIG.

The minimum value output circuit 11C has a (R-Y) color difference signal c output from the delay circuit 3C at the other input terminal.
Is supplied and is output from the delay circuit 3C (R-
(Y) Color difference signal c and (R-
Y) The level of the color difference signal f is compared, and the one with the lower level is output as shown in FIG.

In addition, the voltage supplied to the input terminal 1C (R-
Y) The color difference signal a and (R-
Y) The color difference signal c is supplied to both input ends of the minimum value output circuit 12C. The minimum value output circuit 12C compares the level of the (RY) color difference signal a supplied to the input terminal 1C with the (RY) color difference signal c output from the delay circuit 3C, and FIG. As shown, the lower level is output.

Each minimum value output circuit 10C, 11C, 12C
The respective output signals of are supplied to the maximum value output circuit 13C. Then, the maximum value output circuit 13C compares the output signals of the minimum value output circuits 10C, 11C, and 12C with each other, and outputs the highest level signal, as shown by the solid line in FIG. 17 (j). The contour was corrected (R-
Y) The color difference signal j is generated and taken out through the output terminal 14C. The dotted line in FIG. 17 (j) is the (RY) color difference signal b output from the delay circuit 2C. Further, the same result is obtained even when the maximum value output circuit and the minimum value output circuit are exchanged.

[0025]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The third conventional example has the following features. First conventional example: The contour is emphasized by increasing the gain in the high frequency range. In principle, a pre-shoot and an overshoot are provided according to the amount of emphasis, so that a "glittering" image is obtained. Since it is a linear process, it works uniformly regardless of the amplitude, contour, and detail. Second conventional example ... This is a system in which the emphasis amount of the circuit of the first conventional example is changed according to its level. At an edge with a large amplitude, the preshoot and overshoot levels caused by the emphasis are also noticeable, so the amount of emphasis is reduced. Therefore, the "glittering" feeling, which is the drawback of the first conventional example, can be suppressed, but the effect also decreases accordingly. Third conventional example ... The contour part (rising, falling) is the first
Using the waveform corrected in the conventional example, the pre-shoot and the over-shoot are performed by using the signals whose timings are deviated except for the contour portion (the parts that are the pre-shoot and the over-shoot in the first and second conventional examples). A waveform with no noise is obtained. However, this method is non-linear processing for edge correction when the signal a is a step wave. Therefore, when the signal a has a waveform (pulse wave or the like) other than that, the signal j has a waveform as shown by the solid line in FIG. However, a malfunction may occur, and the effect of improving the feeling of detail is not as great as in the first and second conventional examples.

Therefore, in the first conventional example, a preshoot and an overshoot according to the amount of emphasis are generated and the image becomes sharp and "glittered". In the second conventional example, the preshoot of a portion having a large amplitude, Overshoot is reduced, but at the same time, the amount of emphasis at that location is also reduced. Furthermore, in the third conventional example, the edge portion can be corrected without preshoot and overshoot.
Other than that can not be corrected (detail feeling is not improved,
There is a problem that it becomes an unnatural picture). SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a contour correction circuit that solves the above problems and can appropriately enhance an image.

[0027]

In order to solve the above-mentioned problems, the present invention provides a secondary differential circuit 2 for performing a secondary differential on an input video signal A, and an amplitude of an output signal B of the secondary differential circuit 2. Limiter 3, a first differentiating circuit 4 for differentiating the output signal C of the limiter 3, a second differentiating circuit 9 for differentiating the input video signal A, and the first differentiating circuit 9. The output signal D of the circuit 4 and the output signal E of the second differentiating circuit 9 are received, and the output signal D of the first differentiating circuit 4 is correlated with the output signal of the second differentiating circuit 9. Correlation logic 5 for extracting a certain portion, third differentiation circuit 6 that differentiates the output signal F of the correlation logic 5, correction signal G that is the output of the third differentiation circuit 6, and the input video signal. And an adder circuit 10 for adding A Providing a contour correction circuit.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram of a horizontal contour correction circuit in image luminance signal processing according to an embodiment of the present invention. In the figure, 1 is an input terminal to which the signal A is input,
Reference numeral 2 denotes a second-order differentiating circuit that receives the signal A and performs second-order differentiation on the signal A. The high-frequency component of the target signal is extracted as a second-order differentiating waveform using an aperture circuit as shown in FIG. The characteristics of the circuit at this time are determined according to the band of the target signal. A reference numeral 3 is a limiter which receives the input of the signal B which is the output of the secondary differentiating circuit 2 and limits the amplitude when the amplitude of the signal B is large. Reference numeral 4 is a differentiating circuit which receives the signal C which is the output from the limiter 3 and differentiates it. For example, a circuit as shown in FIG. 3 is used. The signal A delayed by the delay circuit 7 for a predetermined time is further input to the differentiating circuit 9, and the signal E is output. The differentiating circuit 9 is connected for the purpose of extracting a primary differential signal from the target signal, and the circuit shown in FIG. 4 is used, for example. Reference numeral 5 is a correlation logic that receives the signals D and E and outputs the signal of the differentiating circuit 4 only when the polarities of the signals D and E are the same.
For example, the configuration shown in FIG. 5 is used. Here, as the amplitude is large and the amount limited by the limiter 3 is large, a differential waveform sharper than the original differential waveform (signal E) is output. Reference numeral 6 denotes a differentiating circuit which receives the input of the signal F and differentiates it by a structure as shown in FIG. 6, for example. A delay circuit 8 delays the signal A for a predetermined time.

In the following, regarding the signal processing of the contour correction circuit configured as described above, FIG. 9 is a waveform diagram when the amplitude is large, and FIG. 10 is a waveform diagram when the amplitude is small.
This will be described with reference to FIG.

The input terminal 1 is shown in FIG. 9 (a) or FIG. 10 (a).
When the video luminance signal A shown in FIG.
Extracts the high frequency component of the signal A as the second derivative waveform shown in FIG. 9 (b) or FIG. 10 (b).

Next, the limiter 3 which receives the input of the signal B output from the secondary differentiating circuit 2 limits the amplitude of the signal C having a large amplitude as shown in the waveform of FIG. 9C. For a signal with a small amplitude, the signal C is passed as it is, as shown in the waveform of FIG. Then, the differentiation circuit 4 receiving the input of the signal C which is the output of the limiter 3 generates the signal D having the differential waveform shown in FIG. 9D or 10D. At this time, a sharper differential waveform is obtained for a signal with a larger amplitude than for a signal with a small amplitude. As the circuit used for the differentiating circuit 4, for example, the differentiating circuit shown in FIG. 3 is used. This is the input signal 1
The signal delayed by 00 ns is subtracted from the input signal.

The video luminance signal A is also input to the differentiating circuit 9 via the delay circuit 7. The purpose of the differentiating circuit 9 is to extract a first-order differential signal from the target signal.
The signal E having the waveform shown in (e) or FIG. 10 (e) is output. As the differentiating circuit 9, for example, the differentiating circuit shown in FIG. 4 is used.

Next, the output signal D of the differentiating circuit 4 and the output signal E of the differentiating circuit 9 are input to the correlation logic 5. Here, the logic of outputting the signal of the differentiating circuit 4 only when the output of the differentiating circuit 4 and the output of the differentiating circuit 9 have the same polarity, for example, the correlation logic having the configuration shown in FIG. 5 is used. In the correlation logic shown in FIG. 5, the signal D and the signal E are input to the minimum value output circuit 12, and the signal D and the signal E shown in FIG.
The signal D shown in (d) is output. On the other hand, among the signals D and E input to the maximum value output circuit 13, FIG.
The signal E shown in (e) or FIG. 10 (e) is output from the maximum value output circuit 13. Then, the maximum value output circuit 14 compares the signal D with the DC input (= 0) and outputs the maximum value. The minimum value output circuit 15 compares the signal E with the DC input (= 0) and outputs 0. Further, the output of the minimum value output circuit 15 is added to the output of the maximum value output circuit 14 by the addition circuit 16, and the result is shown in FIG. 9 (f) or FIG. 10 (f).
The signal F having the waveform shown in is output. In the correlation logic 5, a signal having a larger amplitude and a larger amount limited by the limiter 3 has a sharper waveform than the original differential signal (output of the differentiating circuit 9).

Next, a correction signal G is generated from the output signal F of the correlation logic 5 through a differentiating circuit as shown in FIG.
The video luminance signal A that has passed through the delay circuit 8 is added by the addition circuit 10. Then, the output terminal 11 is shown in FIG.
A video luminance signal H having a waveform shown in 0 (h) and having undergone contour correction is output. When the amplitude is large and the width of the waveform of the output signal F of the correlation logic 5 is narrow, the width of the generated correction signal G is also narrow and the preshoot and overshoot do not occur as shown in the waveform of FIG. A correction signal is obtained. On the other hand, as the amplitude becomes smaller, the correlation logic 5
The width of the waveform of the output signal F becomes wider, and preshoot and overshoot occur as shown in the waveform of FIG.

FIG. 11 uses a pulse wave instead of the above step wave as an input signal.
The waveform of (h) appears at the same place as the step wave. According to this, the waveform shown in FIG.
As shown in FIG. 8, the waveform is contour-corrected by the third conventional example, and the waveform is properly emphasized without malfunction.

In the above embodiment, the contour correction is performed on the horizontal video luminance signal, but the present invention can be applied to the case where the contour correction is performed on the color difference signal. It can also be applied to an RGB signal whose domain components are attenuated. Furthermore, in the above-described embodiment, the contour correction is performed in the horizontal direction, but it can be applied in the vertical direction. Specifically, as shown in FIG. 7, a line memory is used for the delay circuit, or as shown in FIG. 8, + 90 ° and −90 are provided on the front and rear sides of the block of the embodiment shown in FIG.
This can be realized by inserting the video phase rotation circuits of ° respectively. As described above, the present invention is not limited to the above-described embodiments, but can be implemented with various modifications within the scope of the gist thereof.

[0037]

According to the present invention, the contour can be emphasized in both the step wave and the pulse wave without producing preshoot and overshoot in a portion having a large amplitude. Malfunctions are less likely to occur as the area emphasis aperture characteristics change. This is because the non-linear processing is not suitable for the small amplitude portion. In addition, the image is not glaring, the contour is sharp, and fine details are emphasized, so that natural image emphasis can be performed.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing an example of a secondary differentiating circuit 2 used in the embodiment of the present invention.

FIG. 3 is a block diagram showing an example of a differentiating circuit 4 used in the embodiment of the present invention.

FIG. 4 is a block diagram showing an example of a differentiating circuit 9 used in the embodiment of the present invention.

FIG. 5 is a block diagram showing an example of correlation logic 5 used in an embodiment of the present invention.

FIG. 6 is a block diagram showing an example of a differentiating circuit 6 used in the embodiment of the present invention.

FIG. 7 is an example of a differentiating circuit used in another embodiment of the present invention.

FIG. 8 is a block diagram showing another embodiment of the present invention.

FIG. 9 is a diagram showing a signal waveform of each part when the amplitude is large in the embodiment of the present invention.

FIG. 10 is a diagram showing a signal waveform of each part when the amplitude is small in the embodiment of the present invention.

FIG. 11 is a diagram showing a signal waveform of each part when a pulse wave is used in the example of the present invention.

FIG. 12 is a block diagram showing a first conventional example.

FIG. 13 is a diagram showing signal waveforms of respective parts of the first conventional example.

FIG. 14 is a block diagram showing a second conventional example.

FIG. 15 is a diagram showing a signal waveform of each part of a second conventional example.

FIG. 16 is a block diagram showing a third conventional example.

FIG. 17 is a diagram showing a signal waveform of each part of a third conventional example.

FIG. 18 is a diagram showing a signal waveform when a malfunction occurs by using a pulse wave in the third conventional example.

[Explanation of symbols]

 1 Input Terminal 2 Secondary Differentiation Circuit 3 Limiter 4, 6, 9 Differentiation Circuit 5 Correlation Logic 7, 8 Delay Circuit 10 Adder Circuit 11 Output Terminal

Claims (1)

[Claims] 1. A secondary differentiating circuit 2 for performing a second differential on an input video signal A, a limiter 3 for limiting the amplitude of an output signal B of the secondary differentiating circuit 2, and a differential signal C for an output of the limiter 3. , A second differentiating circuit 9 for differentiating the input video signal A, an output signal D of the first differentiating circuit 4 and an output of the second differentiating circuit 9. Signal E
Of the output signal D of the first differentiating circuit 4 from the output signal D of the first differentiating circuit 4, and a correlation logic 5 for extracting a portion having a correlation with the output signal of the second differentiating circuit 9; It is provided with a third differentiating circuit 6 for differentiating F and an adder circuit 10 for adding the correction signal G which is the output of the third differentiating circuit 6 and the input video signal A. Contour correction circuit.