JPH0345095A - Picture contour exaggeration circuit - Google Patents

Abstract

PURPOSE:To improve the picture quality by relating the saturation of a chrominance signal to a second order differentiating characteristic obtaining a high frequency component (contour component) of a luminance signal and controlling a picture so as to increase the level of the high frequency component when the saturation is high. CONSTITUTION:A second order differentiating output (high frequency component) of a luminance signal Yin is obtained from an adder 15 and its output is inputted to a picture quality adjustment circuit 16 and a multiplier 17 and each output is fed to an adder 18. On the other hand, a chrominance signal Cin is subject to absolute processing by na absolute value circuit 21 and only a low frequency component is led out from the absolute value output by a low pass filter 22 and the low frequency component is inputted to a slice circuit 23 and compared with a slice level set by a slice level control signal. Then only a signal larger than the slice level is used as a control signal for the multiplier 17. When the saturation of the chrominance signal is high, the amplification factor in the multiplier 17 is increased accordingly. Thus, when the saturation is high, the contour is automatically exaggerated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an image contour enhancement circuit incorporated in a video signal processing device of a television receiver or a video tape recorder.

(Prior Art) Generally, in a video signal processing device, aperture compensation is performed on a video signal output from an image pickup tube or a solid-state image sensor (COD, MOS, etc.) because high-frequency components are reduced. Aperture compensation refers to extracting and correcting a portion of an image where the luminance changes frequently, that is, an image contour portion.

As a method for correcting the image contour, there is a method of second-order differentiating the luminance signal, extracting a high-frequency component, adjusting the level of this high-frequency component, and adding it to the low-frequency component of the luminance signal.

(Problem to be Solved by the Invention) By the way, in conventional video signal processing devices, for example, when converting camera output into a composite signal (NTSC system or PAL system), band limitation of color difference signals is performed, and γ correction is also performed. Therefore, when demodulating the composite signal, there is a problem that the high frequency components of each R, G, and B signal deteriorate. Especially when the color is highly saturated, the brightness signal has few high-frequency components, so almost no contour correction is performed.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image contour enhancement circuit that can perform contour correction of a luminance signal according to the level of saturation even when the color is highly saturated.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a means for extracting a high frequency component of a luminance signal, a means for obtaining an absolute value output of a low frequency component of a carrier color signal, and a means for extracting the absolute value output of a low frequency component of a carrier color signal. slicing means for determining whether or not the amplitude of the amplitude is larger than a preset value, and outputting a control signal corresponding to the magnitude of the amplitude when the absolute value output is larger than the preset value; A multiplication device for multiplying a high frequency component of a signal by the control signal, and a device for adding the multiplication output from the multiplication device and the amplitude adjustment output of the luminance signal and its high frequency component. .

(Function) By the above means, the saturation of the color signal is associated with the second-order differential characteristic for obtaining the high-frequency component (contour component) of the luminance signal,
When the saturation is high, high-quality contour correction is possible because the level of the high-frequency component is controlled to be high.

(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 luminance signal Y1n is supplied to the input terminal 11, and a color signal C is supplied to the input terminal 12.
1n is supplied.

The luminance signal Yin is supplied to a delay circuit 13, a (-1/2) coefficient multiplier 19, and a delay circuit 20. The delay circuit 20 has a delay amount of a predetermined time τ, and the delay circuit 13 has a delay amount of a predetermined time τ.
It has a delay amount of τ. The output of the delay circuit 13 is (-1/2)
is supplied to the adder 15 via the coefficient unit 14. The outputs of the coefficient multiplier 19 and the delay circuit 20 are also supplied to the adder 15 .

The adder 15 obtains a second-order differential output (high frequency component) of the luminance signal Yin.

The output of the adder 15 is sent to the image quality adjustment circuit 16 and the multiplier 17.
is input. The multiplier 17 is given a control signal, which will be described later, and amplifies the signal accordingly. Further, the image quality adjustment circuit 16 is given a control signal according to an external operation, and the signal is amplified accordingly.

The outputs of the image quality adjustment circuit 16 and the multiplier 17 are sent to the adder 18
supplied to The output of the aforementioned delay circuit 20 is also supplied to this adder 18 .

On the other hand, the absolute value of the color signal C1n is taken by the absolute value circuit 21, and only the low frequency component of the absolute value output is derived by the low pass filter 22. This low frequency component is input to the slice circuit 23 and compared with the slice level set by the slice level control signal. Then, only signals larger than the slice level are derived from the slice circuit 23 and used as control signals for the multiplier 17.

As a result, the second-order differential output obtained from the adder 15 is associated with the color signal in the multiplier 17.

That is, when the saturation of the color signal is high, the amplification factor in the multiplier 17 is increased according to its magnitude. Therefore, when the saturation is high, contour enhancement is automatically obtained.

FIG. 2 shows signal waveforms at various parts of the above circuit.

FIG. 2(A) shows the luminance signal Y supplied to the input terminal 11.
1n, the same figure (B) shows the color signal C supplied to the input terminal 12.
It is 1n. Further, (C) in the figure is the output of the adder 15, and (D) in the figure is the output of the slice circuit 23. Further, (E) in the same figure shows the output of the multiplier 17, whose amplitude is controlled according to the control signal from the slice circuit 23. (F) in the figure is the final output from the adder 18.

FIG. 3 shows another embodiment of the invention. The same parts as in the previous embodiment are given the same reference numerals. This embodiment demodulates the color signal Cin into a (RY) signal and a (B-Y) signal,
Each color difference signal is supplied to a respective low pass filter 35,36. Demodulation processing is performed as follows. The demodulated carrier fsc at the input terminal 50 is supplied to the multiplier 34 via the transferer 31 and is also supplied to the multiplier 3 via the transferer 32.
3.

Then, from the multiplier 33, the (RY) signal, the multiplier 3
4, a (B-Y) signal is obtained. This color difference signal (R
-Y) and (B-Y) are low pass filters 35.36 respectively
supplied to The output of the low-pass filter 35.36 is then supplied to an absolute value circuit 37.38 to obtain an absolute value, and the absolute value output is supplied to a slice circuit 39.40.

The slice circuits 39 and 40 compare the input signal with the slice level set by the slice level control signal,
The input signal is derived only when it is larger than the slice level. The outputs of each of the three slice circuits 40 are both supplied to a minimum value circuit 41 and a maximum value circuit 42.

The outputs of the maximum value circuits 41 and 42 are output to terminals S and C of a multiplexer 43. The outputs from the previous three slice circuits and 40 are supplied to terminals a and d of this multiplexer 43, respectively.

According to the above embodiment, it is possible to obtain edge enhancement separately for each color signal component. For example, the selector 43
When selecting , contour enhancement is obtained when the saturation of the (RY) component is high, that is, when the red color is strong.

Further, when the selector 43 selects the terminal d (B
-Y) Edge enhancement is obtained when the saturation of the signal component is high, that is, when the blue color is strong. Furthermore, when terminal C is selected, when the saturation of the color signal is high, edge emphasis can be slightly suppressed to obtain the overall hue, and when terminal C is selected, maximum emphasis can be obtained. .

[Effects of the Invention] As explained above, the present invention can perform contour correction of a luminance signal according to the level of saturation even when the color is highly saturated, thereby further improving image quality. I can do it.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the invention, FIG. 2 is a diagram showing signal waveforms at various parts of FIG. 1, and FIG. 3 is a circuit diagram showing another embodiment of the invention. 13.20...Delay circuit, 14.One...Coefficient unit,
16... Image quality adjustment circuit, 17.33.34... Multiplier, 21.37.38... Absolute value circuit, 23.39.
40...Slice circuit, 15.18...Adder, 3
5.36...Low pass filter.

Claims (2)

[Claims] (1) means for extracting high-frequency components of a luminance signal; means for obtaining an absolute value output of a low-frequency component of a carrier color signal; and determining whether the amplitude of the absolute value output is larger than a preset value. and a slicing means for outputting a control signal corresponding to the magnitude of the amplitude when the absolute value output is larger than the set value, and a multiplication unit for multiplying the high frequency component of the luminance signal by the control signal. An image contour enhancement circuit comprising: means for adding the multiplication output from the multiplication means and the amplitude adjustment output of the luminance signal and its high frequency component. (2) means for extracting high-frequency components of the luminance signal; means for demodulating the color signal into first and second color difference signals; and means for obtaining the absolute value outputs of the low-frequency components of each demodulated output; It is determined whether the amplitude of the value output is larger than a preset value, and if the amplitude of each absolute value output is larger than the set value, a control signal corresponding to the magnitude of the amplitude is sent to each of the absolute value outputs. first and second slicing means that generate the signal; a minimum value circuit that receives each control signal of the first and second slicing means and selects and derives the smaller signal; and the first and second slicing means. a maximum value circuit which receives each control signal of the slicing means and selects and derives the larger signal; and selectively outputs the outputs of the first and second slicing means, the minimum value circuit or the maximum value circuit. multiplexer means for outputting; means for multiplying the high frequency component of the luminance signal by using the output of the multiplexer means as a control signal; a multiplication output from the multiplication means; and an amplitude adjustment output of the luminance signal and its high frequency component. What is claimed is: 1. An image contour enhancement circuit comprising: means for adding .