JPH0276479A - Picture quality correcting device - Google Patents

Abstract

PURPOSE:To decrease a noise at a video with a small detailed part and to obtain a more powerful video at a video with a large detailed part by providing an outline emphasizing circuit and a detailed part emphasizing circuit at a picture quality correcting device and controlling by a detailed part detecting part. CONSTITUTION:A full wave rectifying circuit 16 rectifies an input video luminance signal (a) through a high pass filter circuit 15. This, after a noise is removed through a first clip circuit 17, is inputted to a second clip circuit 19 and a limiter circuit 18. An output (p) of the circuit 19 is the higher signal of the outline part and an output (n) of the circuit 18 becomes a higher signal to mix the detailed part and the outline part. When the output (p) of the circuit 19 is subtracted from the output (n) of the circuit 18, a high area signal (q) of the detailed part is taken out. This is smoothed by a smoothing circuit 21, inputted as a control voltage (r) of a variable amplifier 14 to control a detailed emphasizing signal (h), and thus, the detailed part emphasis is strengthened by the signal having many detailed parts, the detailed part emphasis is weakened by the signal having small detailed parts and a noise feeling can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image quality correction device including a video detail enhancement circuit.

Conventional technology Traditionally, image quality correction devices such as television receivers have used detail enhancement circuits and contour enhancement circuits to make images appear clearer, but as television receivers have become larger in recent years, these circuits have been used. There is a growing desire to strongly emphasize details in order to make images look clearer. However, if it is emphasized too strongly, noise will also increase, and countermeasures are considered important.

Hereinafter, a conventional image quality correction device as described above will be explained with reference to the drawings.

FIG. 3 shows a conventional image quality correction device. Moreover, FIG. 4 shows the waveforms of each part. In FIG. 3, l is an image quality emphasizing circuit that performs second-order differentiation of the input video luminance signal a to generate an image quality correction signal S. Reference numeral 2 denotes a variable amplification circuit that amplifies the image quality correction signal C according to the level of the image quality adjustment signal C. Reference numeral 3 denotes an image quality adjustment volume that generates an image quality adjustment signal C for determining the gain of the variable amplifier circuit 2. 4 is a delay circuit that synchronizes the timing of the image quality correction signal d obtained by the image quality emphasis circuit 1 and the variable amplification circuit 2 with the input video luminance signal a.

Reference numeral 5 denotes an addition circuit that adds the delayed input video luminance signal e obtained by the delay circuit 4 and the amplified image quality correction signal to obtain an output video luminance signal f.

The operation of the image quality correction device configured as described above will be explained below. First, the input video luminance signal a of the image quality correction device is input to the image quality enhancement circuit 1. As shown in FIG. 4, the video luminance signal is second-order differentiated to create an image quality correction signal. Next, this image quality correction signal S is amplified by the variable amplification circuit 2 according to the magnitude of the image quality adjustment signal C set by the image quality adjustment volume 3. The input video luminance signal a is delayed in a delay circuit 4 in order to match the timing with the image quality correction signal d, and added in an adder circuit 5 to obtain an output video luminance signal f whose image quality has been corrected.

Problems to be Solved by the Invention However, in the above configuration, once the image quality adjustment volume 3 is set, the amount of image quality correction does not change no matter what kind of video is input, and the image quality adjustment volume 3 is adjusted so that there are no details. The problem with this method is that only noise is noticeable in images that are similar to the original image.

In view of the above-mentioned problems, the present invention provides an image quality correction device that can reduce noise in images by automatically changing the amount of image quality correction depending on the amount of detail in an input video signal. .

Means for Solving the Problems To achieve this object, the image quality correction device of the present invention includes a detail emphasis circuit, an edge emphasis circuit, a high-pass filter circuit, first and second clip circuits, a limiter circuit, a full wave It consists of a rectifier circuit, a subtraction circuit, a smoothing circuit, an addition circuit, and a variable amplification circuit.

Function: With this configuration, a detail emphasizing circuit that selectively emphasizes only the small signal bones of the image and a contour emphasizing circuit that selectively emphasizes only the large signal parts of the image are provided, and the effect of the detail emphasizing circuit can be changed depending on the image. There is.

First, the input video luminance signal is passed through a high-frequency filter circuit to extract the high-frequency video signal. This is then rectified by a full-wave rectifier circuit. This is passed through a first clip circuit to remove noise, and then input to a second clip circuit and a limiter circuit. The output of the second clipping circuit is a high frequency signal of the contour portion, and the output of the limiter circuit is a high frequency signal containing a mixture of details and contour portions. Therefore, by subtracting the output of the second clip circuit from the output of the limiter circuit, detailed high-frequency signals can be extracted. By smoothing this with a smoothing circuit and inputting it as the control voltage of the variable amplifier that controls the detail emphasis signal, the detail emphasis is strengthened for signals with a lot of detail, weakened for signals with little detail, and noise It can reduce the feeling.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows an image quality correction device in one embodiment of the present invention. In FIG. 1, 3 is an image quality adjustment volume, and 4 is a delay circuit, which is the same as the configuration shown in FIG. 3. Reference numeral 5 denotes an adder circuit that adds the output of the delay circuit 4, the outputs of the first variable amplifier circuit 13, and the outputs of the second variable amplifier circuit 14. Reference numeral 11 denotes an edge enhancement circuit, which selectively emphasizes mainly high contrast ratio edges, that is, edge portions of the input video luminance signal, and outputs an edge enhancement signal. Reference numeral 13 denotes a first variable amplifier circuit that controls the amplitude of the contour emphasis signal according to the voltage of the image quality adjustment volume 3. Reference numeral 12 denotes a detail emphasizing circuit that selectively emphasizes a signal with a small contrast ratio of the input video luminance signal, that is, detail information, and outputs a detail emphasizing signal. 14 is a second variable amplifier circuit, which controls the amplitude of the detail emphasis signal according to the output voltage of the image quality adjustment volume 3 and the smoothing circuit 21. 15 is a high-pass filter circuit that extracts only a high-pass video signal from the input video luminance signal.

Reference numeral 16 denotes a full-wave rectifier circuit, which aligns the polarities of the high-frequency video signals and outputs a rectified high-frequency video signal. A first clipping circuit 17 removes only the noise component near zero of the rectified high-frequency video signal and outputs the clipped rectified high-frequency video signal. 18 is a limiter circuit that extracts only a small signal portion corresponding to details from the clip rectified high-frequency video signal and outputs a detail video signal. A second clip circuit 19 extracts only a large signal portion corresponding to a high contrast ratio edge, that is, a contour portion, from the clip rectified high-frequency video signal and outputs a contour video signal. 20 is a subtraction circuit which subtracts the contour video signal from the detail video signal and outputs a detail control pulse signal.

21 is a smoothing circuit which smoothes the detailed control pulse signal and outputs it as a detailed control voltage.

The operation of the image quality correction device configured as described above will be explained below.

First, FIG. 2 shows the operating waveforms of each part in this embodiment. The input video luminance signal a input to the image quality correction device is input to a delay circuit 3, an edge enhancement circuit 11, a detail enhancement circuit 12, and a high-pass filter circuit 15, respectively.

First, the delay circuit 4 adjusts the timing of the input video luminance signal a to the delay of each circuit system and outputs the delayed video luminance signal e to the addition circuit 5. Next, the edge enhancement circuit 11 extracts edges (
A contour emphasis signal g is generated for the contour portion) and outputted to the first variable amplification circuit 13. The noise component included in the input video luminance signal a is not outputted to this contour emphasis signal g because it is a small signal. The first variable amplifier circuit 13 controls the amplitude of the contour correction signal g according to the voltage set by the image quality adjustment volume 3, and outputs it to the addition circuit 5 as an amplified contour emphasis signal i.

Next, the detail emphasizing circuit 12 generates a detail emphasizing signal for a small amplitude portion (detail noise) of the input video luminance signal a, and sends it to the second variable amplification circuit 14 . This variable amplification circuit 14 includes an image quality adjustment volume 3 and a smoothing circuit 2.
The amplitude of the detail emphasis signal is controlled according to the sum of the output voltages (detail control voltage r). Then, the amplified contour emphasizing signal i output from the l-th variable amplifying circuit 13 and the amplified detail emphasizing signal j output from the second variable amplifying circuit 14 are combined into a delayed video luminance signal e by an adder circuit 5.
is added to obtain an enhanced video luminance signal f.

Next, in order to obtain the detailed control signal r, first, the input video luminance signal a is passed through the high-frequency filter circuit 15 to extract only the high-frequency component, thereby obtaining the high-frequency video signal k.

Next, the full-wave rectifier circuit 16 performs full-wave rectification on the high-frequency video signal k to obtain a rectified high-frequency video signal l. Next, this signal l
A first clipping circuit 17 removes a minute signal portion (mainly noise components) from the signal to obtain a clip rectified high-frequency video signal m.

Next, this signal m is input to the limiter circuit 18 and the second clip circuit 19, and the limiter circuit 18 selects only the detail signal to obtain the detail video signal n. Further, the second clipping circuit 19 selects only the contour portion having a high contrast ratio and obtains a contour video signal p. Strictly speaking, the detailed video signal n obtained here includes contours in addition to the details,
Therefore, in order to obtain accurate detail signal components, the contour video signal p is subtracted from the detail video signal n. This is performed by a subtraction circuit 20, and a detailed control pulse signal q is obtained as an output signal. When this signal q is smoothed by the smoothing circuit 21, a voltage (detail control signal r) corresponding to the amount of detail is obtained. In other words, the voltage decreases where there is little detail signal, and the voltage increases where there is a lot of detail signal, and by controlling the amplitude of the detail emphasis signal, the detail emphasis is not performed as much in images with little detail. It reduces noise, and conversely, in videos with a lot of detail, the details are strongly emphasized, increasing the power of the video.

As described above, according to this embodiment, the details of the video are detected,
By controlling detail emphasis according to this amount,
It reduces noise in images with little detail, and conversely, makes images with a lot of detail more powerful.

In this embodiment, although the outline enhancement circuit 11 was explained,
This may be a beam velocity modulation circuit. Further, the clip circuit may be a coring circuit. In addition, high-pass filter circuit 1
5 may be a differential circuit. Further, the full-wave rectifier circuit 16 may be a half-wave rectifier circuit. Furthermore, in this embodiment, a full-wave rectifier circuit 16 is inserted after the high-pass filter circuit 12, but this is eliminated and a full-wave rectifier circuit is installed on the output side of the limiter circuit and the second clip circuit 19. It may be inserted.

Effects of the Invention As described above, the present invention provides an image quality correction device with an edge enhancement circuit and a detail enhancement circuit, and performs detail enhancement using a high-pass filter circuit, a rectification circuit, a clip circuit, a limiter circuit, a subtraction circuit, and a smoothing circuit. Controlled by a detail detection section consisting of a circuit, etc., it is possible to reduce noise in images with few details, and to obtain more powerful images in images with many details, which has a great practical effect. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an image quality correction device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of each part of FIG. 1, FIG. 3 is a block diagram of a conventional image quality correction device, and FIG. , FIG. 4 is a waveform diagram of each part of FIG. 3. 3... Image quality adjustment volume, 4... Delay circuit, 5... Addition circuit, 11... Contour emphasis circuit, 12... Details Emphasis circuit, 13...
...First variable amplification circuit, 14...Second variable amplification circuit, 15...High frequency filter circuit, 16.
...Full wave rectifier circuit, 17...First clip circuit, 18...Limiter circuit, 19...
. . . second clip circuit, 20 . . . subtraction circuit, 21 . . . smoothing circuit. Name of agent: Patent attorney Shigetaka Awano Haka 1 person a - Ichikushi Kaka video i Minatoho No. 1 1A - Ichikameuki cast image signal Q-1 difference Takashi blowing image No. 4 m --- gu F'' 8. Contribution to 1 to 1 to Yūryoku γ --- Gaya Gorge Torture No. p - 11 traces! No. and 1111
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Claims (2)

[Claims] (1) A detail enhancement circuit that emphasizes detailed information of a video luminance signal, an edge enhancement circuit that emphasizes edges with a high contrast ratio such as the contour of a video luminance signal, and a high-frequency filter that extracts only high-frequency components of the video luminance signal. a wave circuit or a differentiating circuit, a first clipping circuit that removes noise components from a high-frequency video signal obtained by the high-frequency filter circuit, and a noise-removed high-frequency video signal output from the first clipping circuit. a limiter circuit that extracts only the small signal portion of the noise-removed high-frequency video signal, a second clip circuit that extracts the large-signal portion of the noise-removed high-frequency video signal, and a first clip circuit that rectifies the small-signal high-frequency video signal output from the limiter circuit. a second rectifier circuit that rectifies the large-signal high-frequency video signal output from the second clip circuit, a subtraction circuit that takes the difference between the output signals of these rectification circuits, and this subtraction circuit. It has a smoothing circuit that smoothes the output signal of the output signal, and is equipped with a variable amplification circuit that controls the effect of the detail enhancement circuit using the output voltage of this smoothing circuit. An image quality correction device that reduces the effect of detail enhancement in images with few detail signals. (2) A detail enhancement circuit that emphasizes detailed information of the video luminance signal, an outline enhancement circuit that emphasizes edges with a high contrast ratio such as the contour of the video luminance signal, and a high-frequency filter that extracts only the high-frequency components of the video luminance signal. a rectifier or a differentiator circuit; a rectifier circuit that rectifies the high-frequency video signal obtained by the high-pass filter; a first clip circuit that removes noise components from the rectified high-frequency video signal of the rectifier circuit; a clip circuit that extracts only the small signal portion of the noise-removed rectified high-frequency video signal output from the clip circuit; a second clip circuit that extracts the large-signal portion of the noise-removed rectified high-frequency video signal; and a limiter circuit. A subtraction circuit that takes the difference between the small signal part and the large signal part of the second clipping circuit, a smoothing circuit that smoothes the output signal of this subtraction circuit, and an output voltage of this smoothing circuit that enhances the effect of the detail enhancement circuit. An image quality correction device comprising a variable amplification circuit for controlling the image quality, and increasing the effect of detail emphasis in images with many detail signals and decreasing the effect of detail emphasis in images with few detail signals.