JPH06319063A - Picture contour emphasizing circuit - Google Patents

Abstract

PURPOSE:To clear the contour of a picture displayed on a screen by properly emphasizing front and rear edges in each step edge of a luminance signal. CONSTITUTION:A luminance signal (a) is inputted to a front edge emphasizing circuit 21 and a rear edge emphasizing circuit 22 in parallel. A front edge emphasizing signal (e) outputted from the circuit 21 provided with an inverter 5 and the 1st high pass filter 6 and a rear edge emphasizing signal (c) outputted from the circuit 22 provided with the 1st delay circuit 3 and the 2nd high pass filter 4 are synthesized by the 1st adder 7 to generate an edge emphasizing signal (f). A gain controlling amplifier (GCA) 8 applies an output (g) obtained by amplifying the signal (f) to the 2nd adder 9. The signal (a) is inputted also to the 2nd delay circuit 2 and delayed so as to compensate the delay of the output (g) of the GCA 8 from the signal (a) and the delayed signal is applied to the 2nd adder 9. The 2nd adder 9 generates an output signal (i) by synthesizing the two inputs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image contour emphasizing circuit for sharpening an image contour.

[0002]

2. Description of the Related Art Recently, an image contour emphasizing circuit has been applied to video signal processing.

The configuration of the conventional image contour emphasizing circuit shown in FIG. 4 will be described. In FIG. 4, 11 is a luminance signal input terminal, 12 is a delay circuit, 13 and 14 are first and second high-pass filters (high-pass filters, HPF), 15 is a gain adjustment amplifier (GCA), and 16 is an inverter. , 17 are adders, and 18 is an output terminal.

The luminance signal j is input to the input terminal 11 of the image contour emphasizing circuit having the above configuration. The input luminance signal j is processed by the two signal processing circuits. That is, in the first path that constitutes one of the signal processing circuits, the two stages of high-pass filters 13 and 1 are used to generate the edge emphasis signal l.
4, the gain is adjusted by the GCA 15, the signal is inverted by the inverter 16, and the output is added by the adder 1
Type in 7. In the second path that constitutes the other signal processing circuit, the time delay of the signal in the first path is calculated in advance, and the luminance signal j is delayed by that amount by the delay circuit 12 and input to the adder 17. Next, the adder 17 combines the respective signals and outputs the output signal p from the output end 18. Waveforms of the respective parts j to p in FIG. 4 are shown in FIG.

[0005]

The above-mentioned conventional image contour emphasizing circuit has a drawback that the front edge F can be emphasized but the rear edge R cannot be embossed so much as shown in the waveform of the output signal p in FIG. Had.

This point will be described with reference to the step response of the two-stage high-pass filter shown in FIG. Here, each of the high-pass filters 13 and 14 is a first-order filter composed of a resistor and a capacitor, and its transfer function is represented by H (s) = s / (s + 1 / RC). Step input of luminance signal j (j in FIG. 6)
In contrast, the output k of the first high-pass filter 13 is V1
It is represented by (t) = EXP (-t / CR), and its waveform is like k in FIG. Next, the output of the second high-pass filter 14, that is, the step response of the edge emphasis signal 1 is V2 (t) = (1-t / CR) * EXP (-t / CR)
The waveform is represented by l in FIG. Looking at the waveform of the edge enhancement signal l, it can be seen that the amplitude ratio between the front edge F and the rear edge R is significantly different, about 7: 1. These can explain the above drawbacks.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an image contour enhancement circuit capable of appropriately enhancing both the front edge and the rear edge of the step edge of the luminance signal. To do.

[0008]

In order to achieve the above object, two high-pass filters, which are conventionally connected in series with each other, are arranged in parallel in the present invention.

More specifically, in the image contour emphasizing circuit according to the present invention, as shown in FIG. 1, the luminance signal a is inputted in parallel to the front edge emphasizing circuit 21 and the rear edge emphasizing circuit 22. The front edge emphasis circuit 21 including the inverter 5 and the first high-pass filter 6 produces a front edge emphasis signal e from the luminance signal a. Rear edge enhancement circuit 22 including first delay circuit 3 and second high-pass filter 4
Produces a rear edge enhancement signal c from the luminance signal a. The first adder 7 produces an edge emphasis signal f which is a combination of the front edge emphasis signal e and the rear edge emphasis signal c. The gain adjustment amplifier (GCA) 8 gives an output g obtained by amplifying the edge emphasis signal f to the second adder 9. The luminance signal a is the second
Is also input to the delay circuit 2 of GCA for the luminance signal a.
It is delayed so as to correct the delay of the output g of 8 and is given to the second adder 9. The second adder 9 is
An output signal i is created by combining the two inputs.

[0010]

According to the present invention, as a result of the front edge enhancement processing and the rear edge enhancement processing being executed in parallel, the amplitude ratios of the front edge and the rear edge in the edge enhancement signal f become substantially equal. Thereby, for each step edge of the luminance signal a, both the front edge and the rear edge are appropriately emphasized.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an image contour emphasizing circuit according to an embodiment of the present invention. In FIG. 1, 1 is an input terminal of a luminance signal, 3 and 2 are first and second delay circuits, 6 and 4 are first and second high-pass filters, 5 is an inverter, 7,
Reference numeral 9 is a first and second adder, and 8 is a gain adjustment amplifier (GC
A) and 10 are output terminals. Among them, the inverter 5 and the first high-pass filter 6 are the front edge emphasizing circuit 21.
The first delay circuit 3 and the second high-pass filter 4 constitute the rear edge enhancement circuit 22, respectively.

FIG. 2 shows step responses of the respective parts a to f in FIG.
Shown in. The step response of the two signal processing circuits, that is, the leading edge enhancing circuit 21 and the trailing edge enhancing circuit 22, will be described with reference to FIG.

In the rear edge enhancement circuit 22, the luminance signal a
2 (a in FIG. 2) is delayed by the first delay circuit 3 (b in FIG. 2), and then the rear edge enhancement of the waveform like c in FIG. 2 is performed through the second high-pass filter 4. Get the signal for. In the example shown in FIG. 2, the delay time of the first delay circuit 3 is 200 ns. On the other hand, in the front edge emphasizing circuit 21, after the step input of the luminance signal a is inverted by the inverter 5 (d in FIG. 2), the front edge of the waveform like e in FIG. 2 is passed through the first high-pass filter 6. Get signal for emphasis. The first adder 7 outputs a signal having a waveform like f in FIG. 2 by adding the outputs e and c of the first and second high pass filters 6 and 4. Here, it is assumed that the resistors and capacitors forming the high-pass filters 6 and 4 are R = 5 kΩ and C = 14 pF. The output formula of each high-pass filter 6 and 4 is V (t) = E
Since it is XP (-t / CR), the amplitude ratio of the front edge F and the rear edge R in the output f of the first adder 7 is 1:
This is 0.94, and it can be understood that the above-mentioned drawbacks of the conventional circuit can be improved.

The operation of the entire image contour emphasizing circuit of the present embodiment configured as shown in FIG. 1 will be described below. FIG. 3 shows the waveform of each part a to i in FIG.

First, the luminance signal a is input from the input terminal 1 to the first delay circuit 3, the second delay circuit 2 and the inverter 5, respectively. The output b of the first delay circuit 3 is input to the second high pass filter 4. The output of the second high-pass filter 4 becomes the trailing edge enhancement signal c having a waveform like c in FIG. 3, and is input to the first adder 7. On the other hand, the output d of the inverter 5 is input to the first high pass filter 6. The output of the first high-pass filter 6 becomes a front edge emphasis signal e having a waveform like e in FIG. 3 and is input to the first adder 7. The first adder 7 synthesizes the rear edge emphasis signal c and the front edge emphasis signal e to generate an edge emphasis signal f for both edges of a waveform such as f in FIG. The edge emphasis signal f is gain-adjusted by the GCA 8 (g in FIG. 3) and then input to the second adder 9.

On the other hand, the time delay in the above signal processing is corrected by the second delay circuit 2. That is, the luminance signal h whose time is adjusted by the second delay circuit 2 and the output g of the GCA 8 that has been subjected to the above-described processing are added to the second adder 9
The output signal i having a waveform like i in FIG. The waveform of the output signal i output from the output terminal 10 is such that both the front edge F and the rear edge R are emphasized with respect to each step edge of the luminance signal a.

As described above, according to this embodiment, by providing two systems of signal processing circuits, the front edge enhancing circuit 21 and the rear edge enhancing circuit 22, the front edge and the rear edge are provided at each step of the luminance signal a. Both can be emphasized.

[0019]

As described above, according to the present invention, since the front edge enhancement processing and the rear edge enhancement processing are executed in parallel, the front edge and the rear edge of each step edge of the input luminance signal are Both are moderately emphasized. As a result, it is possible to realize a clear image quality in which the contour is emphasized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image contour enhancement circuit according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing a step response of each part in FIG.

3 is a waveform diagram of each part when a luminance signal is input to the image contour enhancement circuit of FIG.

FIG. 4 is a block diagram showing a configuration of a conventional image contour enhancement circuit.

5 is a waveform diagram of each part when a luminance signal is input to the image contour enhancement circuit of FIG.

FIG. 6 is a waveform diagram showing the step response of each part in FIG.

[Explanation of symbols]

 1,11 Input terminal 2,3,12 Delay circuit 4,6,13,14 High pass filter (HPF) 5,16 Inverter 7,9,17 Adder 8,15 Gain adjustment amplifier (GCA) 10,18 Output terminal 21 Front edge enhancement circuit 22 Rear edge enhancement circuit a, j Luminance signal c Rear edge enhancement signal e Front edge enhancement signal f, l Edge enhancement signal i, p Output signal F Front edge R Rear edge

Claims (1)

[Claims] 1. An inverter for inverting an input luminance signal, a first high-pass filter for generating a front edge emphasis signal from the output of the inverter, and a first delay for delaying the luminance signal. A circuit, a second high-pass filter for generating a rear edge enhancement signal from the output of the first delay circuit, a front edge enhancement signal output from the first high pass filter, and a second high pass filter A first adder for producing an edge emphasis signal by synthesizing the rear edge emphasis signal with the gain adjustment amplifier for amplifying the edge emphasis signal output from the first adder; A second delay circuit for delaying the luminance signal so as to correct the delay of the output of the gain adjustment amplifier with respect to the luminance signal; Image edge enhancement circuit characterized by comprising a second adder for producing an output signal by combining the output of said the output of the delay circuit gain adjustment amplifier.