JPS63172576A - Picture signal processor - Google Patents

Abstract

PURPOSE:To attain appropriate picture correction by controlling outline emphasis and high frequency noise suppression in accordance with S/N. CONSTITUTION:An S/N detection circuit 60 and a discrimination circuit 80 are provided. Totally different control is executed on the output characteristic of a high-pass filter (HPF) 20 in accordance with S/N, and the output signal is added to an original input signal. Outline emphasis is executed on the picture signal of satisfactory S/N, and high frequency noise suppression and outline emphasis are executed on that of unsatisfactory S/N. Thus, appropriate picture signal correction corresponding to the S/N of an input picture signal can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an image signal processing device for video equipment.

BACKGROUND OF THE INVENTION A conventional image signal processing device is, for example, the one developed in 1982.
2NHK Giken Monthly Report Pso-P66 "Digital contour corrector for high-quality television cameras".

FIG. 5 shows a block diagram of this conventional image signal processing device. 10 is an input terminal for an image signal. 2o
is an HPF (high pass filter) that extracts only high frequency components of an image signal. 30 is a conversion circuit that imparts non-linear characteristics to the output signal of the HPF 20 and outputs the same. 40 is an addition circuit that adds the output signal of the conversion circuit 30 and the input image signal. 50 is a corrected image signal output terminal.゛In the conventional image signal processing device configured as described above, the input terminal 10II'1HPF20 and the addition circuit 4o
The image signals are input to each circuit.

The HPF 20 extracts only the high frequency component of the input image signal and outputs it to the conversion circuit 3o.The 0 conversion circuit 30 extracts only the high frequency component of the input image signal and outputs it to the conversion circuit 3o.
If a is from, output 0; if less than -a,
When the input is X, the yt ratio output is expressed by Equation 7=X+IL, and when it is greater than a, y is outputted as expressed by Equation y=14. FIG. 6 shows the input/output characteristics of the conversion circuit 3o. In the figure, the X axis is the input of the conversion circuit 3o, that is, H
The output of the PF 20 is 0, and the τ axis is the output of the conversion circuit 3o.The output signal of the HPF 20 is divided into an image contour component and a high frequency noise component. In general, with respect to level changes in the contour part of the input image signal, level changes due to high frequency noise are
Since the amount of noise is very small, the output signal of the HPF 2o with a small amplitude can almost be regarded as a high-frequency noise component. The input/output characteristics shown in FIG. 6 indicate that if the level of the input signal is between the set value and the level a, it is considered to be a high frequency noise component, and is removed and output. Here, the reason why offsets of a and -a are provided when the input level is smaller than -a or larger than B is to eliminate discontinuous points in the output level, and at the setting value -a and around a, This is to eliminate visual discomfort. As a result of the above, the output signal of the conversion circuit 3o is an image contour component signal from which high frequency noise components have been removed.

The addition circuit 40 adds the output signal of the conversion circuit 3o and the original input image signal. The output of the adder circuit 40 is a correction signal that emphasizes only the outline of the input image signal, and is output to the correction signal output terminal 5o.

Problems to be Solved by the Invention However, with the above configuration, the high frequency noise of the input image signal is neither emphasized nor suppressed. The problem was that high frequency noise was noticeable.

In view of the above, the present invention provides an image signal processing device that controls contour enhancement and high frequency noise suppression according to S/N and performs appropriate image correction.

Means for Solving the Problems The present invention provides an S/N detection circuit that detects the S/N of an input image signal, an HPF that extracts high frequency components of the input image signal,
A first conversion circuit outputs 0 when the output of the HPF is below a certain set level, and outputs a signal with the same polarity as the output of the HPF when the output is above the set level, and when the output of the HPF is below a certain set level. a second conversion circuit that outputs a signal with the polarity of the output of the HPF inverted, and outputs a signal with the same polarity as the output of the HPF when the output is equal to or higher than a set level;
a selection circuit that switches the output of the conversion circuit and the second conversion circuit; a determination circuit that determines the output of the S/N detection circuit and outputs a signal for controlling the selection circuit; This is an image signal processing device including an addition circuit that adds the output of the image signal and the input image signal.

Operation The present invention has the above-described configuration, and the S/N of the input image signal is
If the signal is good, the signal is added to the input image signal only when the output amplitude level of the HPF is equal to or higher than a certain setting level, thereby enhancing the contour.
If N is bad, if the HPF output amplitude level is above a certain setting level, it is added, and if the amplitude level is below a certain setting level, the polarity is reversed and added to the input image signal, thereby enhancing the contour. It is controlled to suppress high frequency noise, making it possible to perform appropriate image correction according to the input image signal.

Embodiment FIG. 1 shows a configuration diagram of an image signal processing apparatus in a first embodiment of the present invention. In Figure 1, the fifth
Components that are the same as those in the conventional example shown in the figures are given the same numbers, and description thereof will be omitted. 31 is a first conversion circuit having the same characteristics as the conventional example 3o, and 32 is a second conversion circuit having characteristics different from 31, each of which receives the output of the HPF 20 as an input. 60 is an S/N detection circuit that detects the SN of the input image signal. 70 is a selection circuit which receives the output of the first conversion circuit and the output of the second conversion circuit and outputs only one of them. Reference numeral 80 denotes a discrimination circuit that discriminates the output of the S/N detection circuit and outputs a control signal to the selection circuit 7o.

The operation of the image signal processing apparatus of this embodiment configured as described above will be explained below.

The input terminal 10 is connected to the S/N detection circuit @Q, the HPF 2o, and the addition circuit 40, and the oS/N detection circuit 6o, which inputs the image signal to each circuit, detects the S/N of the input image signal. A 0 discrimination circuit 8o that detects N and outputs a detection signal to the discrimination circuit 80 discriminates the S/N'i of the image signal based on the detection signal, and a 0 selection circuit 70 that outputs a control signal to the selection circuit To. selects the output of either the first conversion circuit or the second conversion circuit according to the control signal and outputs it to the addition circuit 40.

First, if the S/N of the input image signal is good, the selection circuit T
o selects the output of the first conversion circuit 31.

Like the conventional example, the first conversion circuit 31 has the input/output characteristics shown in FIG. 6, and outputs a contour component signal from which high frequency noise components have been removed. The adder 40 adds the input image signal and the output signal of the first conversion circuit 31. Since the input image signal is a signal with a good signal to noise ratio, the addition circuit 41 outputs a correction signal with less noise and edge enhancement to the correction image signal output terminal 50.

Next, if the S/N of the input image signal is poor, the selection circuit 7
o is the second conversion circuit 3 that selects the output of the second conversion circuit 32;
2 outputs y expressed by the formula y=-x when the input is X when the setting value is -1%m to 1Aa, and -1
If it is less than /12a, y expressed by the formula y=x+a is output, and if it is greater than %a, y expressed by the formula y=x-a is output. FIG. 2 shows the input/output characteristics of the second conversion circuit 32. In the figure, the X axis is the input of the second conversion circuit 32, that is, the output of the HPF 20, and the Y axis is the output of the second conversion circuit 32.

In the characteristics shown in FIG. 2, when the input is between 1 and 0, the output is positive for a negative input level. Further, between O and a, the output is negative for a positive input level. In other words, when the input level is from -1 to ILν, the output polarity of the HPF is inverted. As explained in the prior art section, a signal with a small amplitude in the HPF output signal can be regarded as a high-frequency noise component, so the input/output characteristics shown in FIG. If it is from a to a, it is regarded as a high frequency noise component, and its polarity is inverted and output.

Here, the reason why the characteristics are not set as the input/output characteristics as shown in FIG. 3 is to eliminate discontinuous points in the output level and to eliminate visual discomfort. As a result of the above, the second conversion circuit 32
The output signal is a high-frequency noise component signal with inverted polarity,
and the contour component signal of the image.

The adder circuit 40 receives the output signal of the second conversion circuit 32, and
The zero high frequency noise component that is added to the input image signal is added to the input image signal with its polarity reversed, so the component is
suppressed. Furthermore, since the contour component is added to the original input image signal with the same polarity, the component is emphasized. Although the original input image signal is a signal with a poor S/N ratio, the addition circuit 4o suppresses its high frequency noise component and outputs a correction signal with contour emphasis to the correction signal output terminal 6°.

As described above, according to this embodiment, the S/N detection circuit 6o,
By providing a discrimination circuit 8o, applying completely different control to the output characteristics of the HPF according to the S/N, and adding the output signal to the original input signal, for an image signal with a good S/N, Contour enhancement is performed, and for a bad image signal of 87H, high frequency noise suppression and contour enhancement can be performed. That is, it is possible to perform appropriate image signal correction corresponding to the S/N of the input image signal.

In this embodiment, control based on S/N is limited to two cases, but intermediate processing is also possible. For example,
Control such as changing the set value & in FIGS. 2 and 6 is easy using S/H. Furthermore, the input/output characteristics of the adjustment circuit are not limited to only combinations of negative-order functions, but may also include characteristics that combine quadratic or higher-order functions, as shown in FIG. 4, for example.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, as described in detail, the S/
Appropriate image signal correction corresponding to H is possible, and its practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an image signal processing device according to an embodiment of the present invention, FIG. 2 is an input/output characteristic diagram of the second conversion circuit of the same device, and FIG. 3 is an input/output characteristic diagram for comparison with FIG. Output characteristic diagram, Figure 4 is an input/output characteristic diagram of the conversion circuit of the image signal processing device in the embodiment of the same location, Figure 6 is a block diagram of the conventional image signal processing device, Figure 6 is the conventional image signal processing FIG. 2 is an input/output characteristic diagram of the conversion circuit in the device and the first conversion circuit in the embodiment shown in FIG. 1; 10... Image signal input terminal, 20...
HPF (high pass filter), 3o... Conversion circuit, 31... First conversion circuit, 32...
Second conversion circuit, 4°...addition circuit, 5o...
...Corrected image signal output terminal, 6o...S/N
Detection circuit, 70... Selection circuit, 80...
・Discrimination circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Sumire Figure 2 Figure 3rl! J Figure 4

Claims (1)

[Claims] An S/N detection circuit that detects the S/N of an input image signal, an HPF (high pass filter) that extracts high frequency components of the input image signal, and outputs 0 when the output of the HPF is below a certain setting level. , a first conversion circuit that outputs a signal with the same polarity as the output of the HPF when the level is higher than the set level;
A second conversion circuit outputs a signal with the polarity of the output of the HPF inverted when the output is below a certain set level, and outputs a signal with the same polarity as the output of the HPF when the output is above the set level. , a selection circuit that switches the outputs of the first conversion circuit and the second conversion circuit, and a determination circuit that determines the output of the S/N detection circuit and outputs a signal for controlling the selection circuit; An image signal processing device comprising: an addition circuit that adds an output from the selection circuit and an input image signal.