JPH0495488A - Color edge enhancer - Google Patents

Abstract

PURPOSE:To enhance the contour of chrominance components by adding the edge of inputted luminance signals to the chrominance components after making the edge of the luminance signals coincident with that of the chrominance components and fetching intermediate signals by means of an intermediate value selecting means. CONSTITUTION:Digital luminance signals are led to an input terminal 210 and inputted to a high-pass filter 211 and differentiation circuit 215. The output of the filter 211 is inputted to one input terminal of a selector 214 and an inverter 213. The output of the inverter 213 is supplied to the other input terminal of the selector 214. The output of the circuit 215 is inputted to one input terminal of a code comparator 216. Digital color difference signals led from an input terminal 310 are supplied to the other input terminal of the comparator 216. The comparator compares the polarity of the luminance signals with that of the differentiated waveform of I signals and obtains a discriminated output which is supplied to the selector 214. When the polarities coincide with each other, the selector 214 leads the output of the filter 212 and, when the polarities do not coincide with each other, leads the output of the inverter 213.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a color edge enhancer that enhances horizontal contours of a color signal in, for example, a television receiver.

(Prior Art) A television receiver is provided with an outline enhancement circuit that emphasizes the outline of an image in order to improve image quality.

As a contour enhancement circuit, the edge component of the luminance signal is extracted,
There is a technique for enhancing color edges by adding this to the color signal. This technology is known, for example, in US Pat. No. 4,504,855.
It is disclosed in No. 3.

FIG. 5 is a block diagram of the contour enhancement circuit. A chroma signal is input to the input terminal 101 and is input to the band pass filter 102 . The eight filters of the band-pass filter 102 are input to a delay device 103 (having a delay amount of 1/2 cycle of one cycle of the chroma signal) and a delay device 104, and are also input to an adder 105. The output of the delay device 103 is also introduced into the adder 105 . As a result, the high frequency component of the chroma signal is extracted from the adder 105.
It is input to quadrant multiplier 06.

On the other hand, a luminance signal is input to the input terminal 111. The luminance signal is passed through a low-pass filter 112 to a differentiating circuit 1.
13, and its differential output is rectified by a rectifier circuit 114. The output of the rectifier circuit 114 is input to a differentiation circuit 115 and further differentiated. The output of this differentiating circuit 115 is further input to a limiter 116 to limit the amplitude.
The signal is input to a two-phase pump waveform generator 117. The output of this two-phase pump waveform generator 117 is then output from the four-quadrant multiplier 1.
06 and is added to the high frequency component of the chroma signal output from the adder 105.

The output of the four-quadrant multiplier 106 is input to an adder 118 and added to the chroma signal output from the delay device 104. As a result, a chroma signal component with an enhanced high frequency range is obtained from the adder 118 and is output to the output terminal 119.

Signal waveforms A to 0 of the above sections are shown in FIG.

(Problems to be Solved by the Invention) The systems described above detect edge components of a luminance signal and utilize these edge components to emphasize the high range of a chroma signal. In this circuit, the high-frequency component of the chroma signal is input to one input terminal of the four-quadrant multiplier 106, and the edge component of the luminance signal is input after nonlinear processing to the other input terminal. In other words, the high-frequency component of the chroma signal is modulated by the edge switching section of the luminance signal.

For this purpose, it is necessary to ensure that the center of the edge of the luminance signal and the center of change in the high frequency component of the chroma signal coincide accurately in time. In addition, the high-frequency components of the clock signal are controlled by detecting the edge components of the luminance signal, but if the edge components are incorrectly detected, the hue of the color edge changes and the color becomes visually unnatural. Occur. In order to improve these problems, a complicated and expensive circuit is required to improve the performance of the circuit for detecting edge components of a luminance signal. Furthermore, if a four-quadrant multiplier is implemented using a digital circuit, the hardware will increase and the circuit scale will increase.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a color edge enhancer that can realize edge enhancement of a color signal with a simple circuit, and that also achieves stable operation without false detection when obtaining the luminance signal edge component necessary for edge enhancement. shall be.

[Structure of the Invention] (Means for Solving the Problems) The present invention comprises: a first delay means for delaying an input color difference signal; a second delay means for delaying an output color difference signal of the first delay means; , a first addition means to which the output signal of the first delay means is input; and a first addition means to which the input color difference signal, the output color difference signal of the addition means, and the output color difference signal of the second delay means are input; An intermediate value selection means for selecting and deriving an intermediate value signal from among the signals, a luminance signal edge component extraction means for detecting an edge component of an input luminance signal, and an edge component output from the luminance signal edge component extraction means. and a means for inputting the output of the polarity matching means to the first addition means.

(Operation) By the above means, first, the edges of the input luminance signal are matched in polarity with the edges of the input color signal, and are added to the color signal. Furthermore, a signal having an intermediate value in the vicinity of this added output color signal is extracted by an intermediate value selection means.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. A digital luminance signal is introduced into the input terminal 210, and the high-pass filter 21
1 (HPF) and is input to the differentiation circuit 215.

The output of the high-pass filter 211 (luminance signal high-frequency component) is input to one input terminal of the selector 214 and the inverter 213 via the low-pass filter 212. The output of this inverter 213 is supplied to the other input terminal of the selector 214.

The output of the differentiation circuit 215 is input to one input terminal of the sign comparator 216. The other input terminal of the sign comparator 216 is supplied with the digital color difference signal introduced from the input terminal 310, for example, the l signal differentiated by the differentiation circuit 311. Therefore, the sign comparator 216 compares the polarities of the differential waveform of the luminance signal and the differential waveform of one signal, and obtains a determination output indicating whether they match or do not match. This determination output is supplied to the control terminal of the selector 214.

If the signs match, the selector 214 derives the output from the low-pass filter 212 as is, and if the signs differ, it derives the output of the inverter 213.

The operations of the code comparator 216, selector 214, etc. described above maintain a normal polarity relationship between the high-frequency component of the luminance signal and the l signal, which emphasizes edges. This is because when the edges of the l signal are emphasized by the high frequency components of the luminance signal, if the polarities of the edges of the l signal and the high frequency components are different, the emphasis cannot be obtained properly.

The input l signal is passed through the delay device 313 and the median filter 31
6 is supplied to the first input terminal. The output of delay device 313 is input to adder 314 and delay device 315. The output of adder 314 is supplied to a first input terminal of median filter 316, and the output of delayer 315 is supplied to a third input terminal of the median filter.

The median filter 316 derives the intermediate value of the three input signals, and its output is supplied to one input terminal of the low-pass filter 317 and the selector 319. The output of the delay device 313 is supplied to the other input terminal of the selector 319, and one of them is selectively derived. The output of comparator 318 determines this selection.

One input terminal of the comparator 318 is supplied with the output of the median filter 316 via a low-pass filter 317, and the other input terminal is supplied with the output of the delay device 313. The comparator 318 calculates a difference value between two input signals, and outputs a determination signal indicating whether the difference value is larger or smaller than a preset value. This determination signal is supplied to a control terminal of selector 319. If the difference value is large, the selector 319 assumes that the output of the median filter 316 is a signal with an undesired waveform, and selects and derives the output of the delay device 313. If the difference value is small, the output of the median filter 316 is selected and derived. Select and derive outputs.

The output of selector 319 is further supplied to one input terminal of selector 400. The output of the delay device 313 is supplied to the other input terminal of the selector 400. The selector 400 includes an edge detection signal generation circuit 312
The edge detection signal generating circuit 312 uses the differential waveform of the l signal output from the differentiating circuit 311 to output an edge detection signal indicating the edge position of the color difference signal. There is. As a result, the selector 400 is activated by the selector 3 only at the edge portion of the l signal.
Select and derive one signal whose contour has been corrected from the signals from No. 19,
In parts other than the edges, the output of the delay device 313 is selectively driven.

FIG. 2 shows signal waveforms at various parts of the above circuit. In the part where the signal waveforms shown in (a) to (k) of the figure are obtained, the first
The same reference numerals are also used in the figures.

The l signal in FIG. 2(a) is supplied to input terminal 310. When this l signal is delayed by delay devices 313 and 315, it becomes as shown in (b) and (c) in the same figure. Also, the differential circuit 31
], the waveform shown in FIG. 3(d) is obtained. The edge detection signal generation circuit 312 switches the negative polarity of the differential waveform to the positive polarity, compares it with the reference level A, regards the position exceeding the reference level A as an edge of one signal, and outputs the detection signal. (Figure 2(e)).

On the other hand, the luminance signal of the input terminal 210 (FIG. 2(f)) is
The edge component (high frequency component) is extracted in the luminance signal edge extraction circuit 100 which is composed of a high pass filter 211 and a low pass filter 212 (FIG. 2(g)).

This high frequency component is input to one terminal of the selector 214 and is inverted by the inverter 213 (Fig. 2 (h)
)) is input to the other input terminal of the selector 214.

The selector 214 and the like constitute a polarity matching circuit 200 that matches the polarity of the edge component extracted from the luminance signal with the polarity of one signal at the same time.

The luminance signal edge components with matched polarities are sent to an adder 31.
4 and added to the output of the delay device 313 (FIG. 2(b)). Therefore, from the adder 313, as shown in FIG.
), a signal with high frequency components added to the edges of the color signal is obtained.

The median filter 316 and the like constitute the intermediate value selection circuit 300, and derive the intermediate value of the three input signals (FIG. 2(k)).

FIG. 3 is a signal waveform diagram shown to explain the operation of the median filter 316. The signal shown in (3a) in the same figure (
If the intermediate value among j), (a), and (c) is selected, the same figure (
A signal as shown in 3b) is obtained. This is the output signal of this median filter 316.

This signal is sent to the output terminal 40 via the selector 319.4oo when the contour correction of the color signal is normally performed.
1.

According to the above embodiment, the edges of the input luminance signal are matched in polarity with the edges of the input color signal and added to the color signal. Furthermore, a signal having an intermediate value in the vicinity of this added output color signal is extracted by an intermediate value selection means.

As a result, with a simple circuit configuration, there is no error in the edge correction direction, and edge correction of the l signal is performed at an appropriate position by selecting the intermediate value.

Furthermore, in this system, depending on the waveform of the l signal, edge component addition may create an undesired waveform, so when such an undesired waveform occurs, it is controlled so that it is not output. There are means to do so.

That is, the low-pass filter 317 and the like connected after the intermediate value selection circuit 300 constitute the high-quality waveform selection circuit 400.

FIG. 4 is a signal waveform diagram shown to explain the operation of the high-quality waveform selection circuit 400.

For example, assume that the l signal has a waveform as shown in FIG. 4 (4a). When the high frequency component of the luminance signal is added to such a waveform, a signal as shown by the solid line in FIG. 4(4b) may be obtained. If an intermediate value signal is derived using a median filter, an undesirable signal with color distortion as shown in FIG. 4(c) will be obtained. This signal is passed through the low-pass filter 317 into a waveform as shown by the solid line in FIG. If the level difference between the solid line signal and the broken line signal is large, this means that the above-mentioned unwanted signal has been obtained from the median filter 316. If an unwanted signal is not obtained, the comparator 31
8, the level difference does not become large.

As mentioned above, if the signal waveform output from the median filter 316 is an unwanted waveform, the selector 31
9 selectively derives the output of the delay device 313. Therefore, it is possible to obtain an appropriate edge enhancement output, and it is possible to prevent image quality from being disturbed due to edge enhancement.

The above explanation is about the contour correction processing for the (2) signal, but it goes without saying that the same circuit can be used for the Q signal as well.

According to the embodiment described above, the polarity of the edge component of the luminance signal is aligned with the polarity of the color difference signal, and the erron part of the color difference signal is replaced with the edge component of the luminance signal to enhance the outline of the color signal. The contour correction is performed by inputting the two color difference signals and the emphasized color difference signal to a median filter and extracting the intermediate value signal. This makes the rise and fall of the waveform more rapid. Selection of an intermediate value at this time can remove ringing around edges. Furthermore, since intermediate value selection is performed, it is easy to set the effect vs. noise malfunction characteristics.

Furthermore, it determines whether the signal output from the median filter is an appropriate signal, and if it is an unwanted signal,
I try to select and derive waveforms with good quality. Furthermore, an edge detection signal of the color difference signal is obtained, and only when this detection signal is present, a color difference signal subjected to contour correction is derived.

For this reason, it is possible to obtain a color difference signal in which the edge correction operation has been performed extremely accurately.

[Effects of the Invention] As explained above, according to the present invention, edge enhancement of color signals can be realized with a simple circuit, and moreover, stable operation can be achieved without false detection to obtain the luminance signal edge components necessary for edge enhancement. can be obtained.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Figs. 2 to 4 are diagrams showing signal waveforms of various parts shown to explain the circuit operation of the invention, and Fig. 5 is a circuit diagram of a conventional color edge. FIG. 6 is a circuit diagram showing the enhancer. FIG. 6 is a diagram showing signal waveforms of various parts of the circuit of FIG. 211... High pass filter, 212... Low pass filter, 213... Inverter, 214... Selector, 215... Differentiating circuit, 216... Sign comparator, 3
DESCRIPTION OF SYMBOLS 11... Differentiation circuit, 312... Edge detection signal generation circuit, 313.315... Delay device, 314... Adder, 316... Median filter, 317... Low pass filter, 318 ...Comparator, 319...Selector. I believe 2 r: 1 L En 11 Yoshiu Applicant's agent Patent attorney Takehiko Suzue No. 2 Figure Figure Figure (G) Figure 2

Claims (3)

[Claims] (1) a first delay means for delaying the input color difference signal; a second delay means for delaying the output color difference signal of the first delay means; and a second delay means for delaying the output color difference signal of the first delay means; 1 adding means; an intermediate adding means for receiving the input color difference signal, the output color difference signal of the adding means and the output color difference signal of the second delay means, and selecting and deriving a signal having an intermediate value from among these signals; a value selection means; a brightness signal edge component extraction means for detecting an edge component of an input brightness signal; and a polarity of the edge component outputted from the brightness signal edge component extraction means to match the polarity of the input color difference signal at the same time. 1. A color edge enhancer comprising: a polarity matching means for adjusting the polarity; and a means for inputting an output of the polarity matching means to the first addition means. (2) The output of the intermediate value selection means is supplied to one input terminal via a low-pass filter, the output of the first delay means is supplied to the other input terminal, and the difference between the quantity inputs is set to a predetermined value. a comparison means for obtaining a judgment signal indicating whether or not the above is the same; an output of the intermediate value selection means is supplied to one input terminal, an output of the first delay means is supplied to the other input terminal, and the judgment signal a first selector that selects and derives the output of the first delay means when the value is greater than or equal to the predetermined value, and selects and derives the output of the intermediate value selection means when the value is less than or equal to the predetermined value. A color edge enhancer according to claim 1, characterized in that: (3) edge detection signal generating means for obtaining an edge detection signal indicating an edge position of the color difference signal from a differential output of the input color difference signal; an output of the first selector is supplied to one input terminal; The output of the delay means is supplied to the other input terminal, and the second selector selectively derives the output of the selector only at a timing when the edge detection signal indicates an edge position of the color difference signal. Color edge enhancer.