JPH08168020A - Picture quality correcting device - Google Patents

Abstract

PURPOSE: To provide a picture quality correcting device which not only emphasizes the contour of an input image signal, but also removes a noise. CONSTITUTION: The input image signal having its high frequency range emphasized through an HPF 11 is inputted to a 1st nonlinear circuit 12 which removes a fine level and a 2nd nonlinear circuit 13 which limits a signal having a large amplitude to extract a signal corresponding to countour information and a noise component. Those signals are switched by an SW13 and an SW17 and then added to or subtracted from the input image signal to emphasize the countour and remove the noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image quality correction device for improving the image quality of image signals.

[0002]

2. Description of the Related Art As a conventional image quality correction device, for example, there is a contour emphasis circuit disclosed in Japanese Patent Laid-Open No. 61-71773. This is shown in FIG. This conventional example is composed of registers 1 and 2, multipliers 3, 4 and 5, adders 6 and 7, and a limiter circuit 8. When an input signal a is supplied, a signal b delayed by one stage by the register 1, 2 by register 2
A signal c delayed by a stage is created. The signal a is multiplied by the coefficient −1 in the multiplier 3, the signal b is multiplied by the coefficient 2 in the multiplier 4, the output signal c of the register 2 is multiplied by the coefficient −1 in the multiplier 5, and the respective outputs are added by the adder 6 Then, the contour enhancement signal ES is obtained by adding. The contour emphasis signal ES is input to the limiter circuit 8 and the output level of the signal E is limited.
S'becomes, which is added to the signal b in the adder 7 and is output as an edge-enhanced image signal.

[0003]

However, in the conventional example, although it is possible to enhance the contour of the input signal,
When noise is superimposed on the input signal, it is impossible to remove this noise.

The present invention has been made in order to solve the above problems, and not only enhances the contour of an input signal, but also
It is an object of the present invention to provide an image quality correction device that can also remove noise.

[0005]

According to a first aspect of the present invention, there is provided an image quality correction apparatus, wherein a high-frequency emphasis filter for emphasizing a high frequency band of an input image signal and a small amplitude component of the filter output or a small amplitude component and a large amplitude component are suppressed. A first non-linear circuit, a second non-linear circuit that suppresses a large amplitude component of the filter output, a first selection circuit that selects the output of the first or second non-linear circuit, and the input image signal And an arithmetic unit for outputting the addition result and the subtraction result of the output of the first selection circuit, and a second selection circuit for selecting the addition result or the subtraction result of the arithmetic unit.

According to another aspect of the image quality correction apparatus, when the first selection circuit selects the first nonlinear circuit, the second selection circuit selects an addition result, and the first selection circuit selects the addition result. When the second non-linear circuit is selected, the second selection circuit is provided with means for interlocking to select the subtraction result.

According to another aspect of the image quality correction device of the present invention, a mid-range emphasis filter for emphasizing a mid-range of an input image signal, a high-range emphasis filter for emphasizing a high range of the input image signal, the mid-range emphasis filter or the high-range emphasizing filter. A third selection circuit that selects the output signal of the band emphasis filter, a first nonlinear circuit that suppresses the minute amplitude component or the minute amplitude component and the large amplitude component of the selection signal, and a large amplitude component of the selection signal A second non-linear circuit, a first selection circuit that selects the output of the first or second non-linear circuit, and an addition result and a subtraction result of the input image signal and the output of the first selection circuit And a second selection circuit for selecting an addition result or a subtraction result of the above arithmetic unit.

According to another aspect of the image quality correction apparatus of the present invention, the first selection circuit selects the first non-linear circuit and the second selection circuit when the third selection circuit selects the mid-range emphasis filter. When the circuit selects the addition result and the third selection circuit selects the high-frequency emphasis filter, the first selection circuit selects the second nonlinear circuit and the second selection circuit subtracts the result. It is provided with a means for interlocking to select each.

An image quality correction apparatus according to a fifth aspect of the present invention is a mid-range emphasis filter that emphasizes a middle range of an input image signal, a high range emphasis filter that emphasizes a high range of the input image signal, the middle range emphasis filter, and the above-mentioned middle range emphasis filter. An adder that adds the outputs of the high-frequency emphasis filter, a fourth selection circuit that selects the output of the middle-frequency emphasis filter, the output of the high-frequency emphasis filter, or the output of the adder, and a small amplitude of this selection signal. A first nonlinear circuit for suppressing a component or a small amplitude component and a large amplitude component,
A second non-linear circuit for suppressing a large amplitude component of the selection signal, a first selection circuit for selecting the output of the first or second non-linear circuit, the input image signal and the first selection circuit An arithmetic unit for outputting the addition result and the subtraction result of the output and a second selection circuit for selecting the addition result or the subtraction result of the arithmetic unit are provided.

According to another aspect of the image quality correction apparatus of the present invention, when the fourth selection circuit selects the mid-range emphasis filter, the first selection circuit selects the first non-linear circuit and the second selection circuit. The circuit selects each addition result,
When the fourth selection circuit selects the output of the adder, the first selection circuit selects the first nonlinear circuit and the second selection circuit selects the addition result,
When the fourth selection circuit selects the high-frequency emphasis filter, the first selection circuit selects the second nonlinear circuit and the second selection circuit selects the subtraction result. It is equipped with a means to make it.

According to a seventh aspect of the present invention, in the image quality correction apparatus according to the first aspect, the third aspect or the fifth aspect, the portion formed by the arithmetic circuit and the second selection circuit is output from the first selection circuit. And a fifth selection circuit for selecting one of the signals obtained by inverting the output logic of the first selection circuit, a sixth selection circuit for selecting either one or 0 value, the input image signal and the above It is composed of an adder for adding the output of the fifth selection circuit and the output of the sixth selection circuit.

[0012]

According to the first aspect of the present invention, the signal extracted by the mid-high range emphasis filter is subjected to the non-linear processing by the non-linear circuit, and then added to the input image signal to enhance the contour and subtract the contour. Remove noise.

According to the second aspect of the present invention, by controlling the two selection circuits using one control signal, the two selection circuits operate in conjunction with each other.

According to the third aspect of the present invention, the signal extracted by the mid-range emphasis filter is subjected to non-linear processing by the non-linear circuit and then added to the input image signal to perform contour emphasis, and further high-frequency emphasis. The signal extracted by the filter is subjected to non-linear processing by a non-linear circuit and then subtracted from the input image signal to remove noise.

According to the fourth aspect of the invention, the three selection circuits are controlled by using one control signal, so that the three selection circuits operate in conjunction with each other.

According to the fifth aspect of the invention, the signal extracted by the mid-range emphasis filter is subjected to non-linear processing by the non-linear circuit and then added to the input image signal to perform contour emphasis and high-frequency emphasis. The signal extracted by the filter is subjected to non-linear processing by the non-linear circuit, noise is removed by subtracting it from the input image signal, and the signal obtained by adding the output of the mid-range emphasis filter and high-range emphasis filter is added to the non-linear circuit. After performing the non-linear processing by, the signal is added to the input image signal to correct the edge enhancement and the reduction of the high frequency signal caused by the aperture effect in the D / A converter inserted in the subsequent stage.

According to the sixth aspect of the invention, the three selection circuits are controlled by using one control signal, so that the three selection circuits operate in conjunction with each other.

According to the invention of claim 7, in one adder according to claim 1, 3 or 5, by inverting the logic of one input and further adding a value of 1, not only the adder but also the subtractor is subtracted. It also works as a container.

[0019]

【Example】

Example 1. A first embodiment according to the present invention will be described with reference to FIG. In the figure, 18 is an input terminal of an image signal, 11 is a high-frequency emphasis filter (hereinafter referred to as “HPF”) that emphasizes high frequencies, 10 is a delay correction circuit that delays the input signal by the same amount as the delay of the HPF 11, and 12 is A first non-linear circuit 13 having the characteristics shown in FIG. 2A or 2B is shown in FIG.
A second non-linear circuit having the characteristics shown in (a) or (b), and 14 is a selection circuit (hereinafter, referred to as “SW”) that selects and outputs an output signal of either one of the non-linear circuits 12 and 13.
15) is an adder, 16 is a subtractor, 17 is a SW for selecting and outputting an output signal of either the adder 15 or the subtractor 16, and 19 is an output terminal.

Next, the operation of the first embodiment will be described when the contour enhancement is performed. At this time, SW14 selects the non-linear circuit 12 side, and SW17 selects the adder 15 side. The image signal input to the input terminal 18 is input to the delay correction circuit 10 and the HPF 11. Since the delay amount of the delay correction 10 is adjusted so as to be the same as the delay amount of the HPF 11, the output signals of the delay correction 10 and the HPF 11 are temporally aligned. The high-frequency emphasized signal by the HPF 11 contains the contour information of the image and the noise component, and is input to the non-linear circuit 12. The characteristics of the nonlinear circuit 12 are
It is configured as shown in FIG. 2A or 2B, and a minute input signal is not output. In this case, since a minute input signal can be regarded as noise, it is possible to remove the noise component and extract only the contour information and output it.

The output of the non-linear circuit 12 is input to the SW 14, and is added to the output signal of the delay corrector 10 in the adder 15 to add a signal corresponding to contour information to the input signal. Outline enhancement is performed, and SW
It is output to the output terminal 19 through 17.

Next, the case of removing noise will be described. At this time, SW14 selects the non-linear circuit 13 side, and SW17 selects the subtractor 16 side. The image signal input to the input terminal 18 is input to the delay correction 10 and the HPF 11. Delay correction 1 so that it becomes the same as the delay amount of HPF 11.
Since the delay amount of 0 is adjusted, the output signals of the delay correction 10 and HPF 11 are aligned in time. HP
The signal subjected to high-frequency emphasis by F11 includes the contour information of the image and the noise component, and is input to the non-linear circuit 13. The characteristic of the non-linear circuit 13 is configured as shown in FIG. 3 (a) or (b), and a minute input signal is output as it is, but a large amplitude signal has a limited output or an output. Not done. This is because a minute input signal is noise and a signal with a large amplitude can be regarded as contour information, so that it is possible to remove the signal component corresponding to the contour information and extract only the noise component and output it.

The output of the non-linear circuit 13 is input to the SW 14, and the subtracter 16 subtracts it from the output signal of the delay compensator 10 to subtract a signal corresponding to the noise component from the input signal. Noise is removed and the signal is output to the output terminal 19 through SW17.

In order to control the SW14 and SW17 in the first embodiment, the respective control signals are usually required, but as shown by the broken line in FIG. Selects the adder 15 side, SW14 selects the non-linear circuit 13 side, and SW17 selects the subtractor 16 side when removing noise.
By linking the two SWs 14 and 17,
Operation is possible with only one control signal.

Example 2. FIG. 4 shows a second embodiment according to the present invention.
This will be described below. In the figure, the same reference numerals as those in FIG. Reference numeral 20 is a mid-range emphasis filter (hereinafter referred to as “BPF”) that emphasizes the mid-range of the input signal, and 21 is the BPF 20 and HP.
This is a SW that selects and outputs one of the output signals of the output of F11.

Next, the operation of the second embodiment will be described. The SW 21 selects the BPF 20 side when the contour enhancement is performed, and the HPF 11 side when the noise removal is performed. That is, the difference from the first embodiment is that the BPF 20 for contour enhancement and the HPF 11 for noise removal are separately provided, and these can be selected by the SW 21. The BPF 20 for contour enhancement has a characteristic of emphasizing the middle frequency range and suppressing the high frequency range. However, since the ratio of the noise component in the high frequency range is larger than that of the contour information, suppressing the high frequency range results in S / N
This is because contour information with good characteristics can be extracted. Except for the above, the same operation as that of the embodiment of claim 1 is performed, and thus the description thereof is omitted.

SW21, S in the second embodiment
For controlling W14 and SW17, normally, respective control signals are required, but as shown by the broken line in FIG. 4, SW21 is on the BPF20 side and SW14 on the edge enhancement during contour enhancement.
Is the non-linear circuit 12 side, SW17 is the adder 15 side, and when removing noise, SW21 is the HPF11 side and SW1
By linking the three SWs 21, 14 and 17 so that 4 is for selecting the non-linear circuit 13 side and SW 17 is for the subtractor 16 side, operation is possible with only one control signal.

Example 3. FIG. 5 shows a third embodiment according to the present invention.
This will be described below. In the figure, the same reference numerals as those in FIG. 1 or FIG. Reference numeral 22 is an adder that adds the outputs of the BPF 20 and HPF 11, and reference numeral 23 is a SW that selects and outputs any one of the outputs of the BPF 20, HPF 11 and adder 21.

Next, the operation of the third embodiment will be described. S
W23 selects the BPF 20 side when the contour enhancement is performed, and selects the HPF 11 side when the noise removal is performed.
Further, when the D / A converter 24 is provided in the subsequent stage of the output terminal 19, the high-frequency characteristic is deteriorated due to the aperture effect of the D / A converter 24, and therefore it is necessary to correct the deterioration of the high-frequency characteristic. . Therefore, when the high frequency characteristic is corrected in addition to the contour enhancement, the SW23 is added by the adder 2.
Select side 2. In this case, SW14 is the nonlinear circuit 12
Side, SW17 selects the adder 17 side. That is, this corresponds to using the output of the HPF 11 for correcting the high frequency characteristic and the output of the BPF 20 for enhancing the contour. In this way, by adding these outputs and suppressing the noise component by the non-linear circuit 12, a signal corresponding to the contour information and a signal for high frequency characteristic correction can be obtained, and this signal is added by the adder 15. By adding to the input signal, contour enhancement and correction of high frequency characteristics are possible. Except for the above operation, the same operation as that of the third embodiment is performed, and thus the description thereof is omitted.

SW23, S in the third embodiment
For controlling W14 and SW17, usually, respective control signals are required, but as shown by the broken line in FIG. 5, SW23 is on the BPF20 side and SW14 on the edge enhancement.
Is the nonlinear circuit 12 side, SW17 is the adder 15 side, and when the aperture effect of the D / A converter 24 is also corrected, SW23 is the adder 22 side, SW14 is the nonlinear circuit 12 side, and SW17 is the adder. When the noise removal is performed, SW23 selects the HPF11 side, SW14 selects the non-linear circuit 13 side, and SW17 selects the subtractor 16 side. Operation is possible only with signals.

Example 4. FIG. 6 shows a fourth embodiment according to the present invention.
This will be described below. In the figure, the same reference numerals as those in FIG. 25 is an inverter for inverting the logic of the input signal, 26
Is a SW that selects and outputs either the output signal of the SW 14 or the output signal of the inverter 25, 27 is a memory that holds a value of 0, 28 is a memory that holds a value of 1, 29 is a memory of 27 and 28 SW to select either output,
An adder 30 adds the output signal of the delay correction circuit and the outputs of the SWs 26 and 29.

Next, regarding the operation of the part different from the first embodiment, first, the case where the addition result of the output signal of the delay correction circuit 10 and the output signal of the SW 14 is output to the output terminal 19 will be described. At this time, SW26 is the output side of SW14, SW
29 selects the memory 27 side. That is, a signal obtained by adding the output of the delay correction circuit 10 and the output of the SW 14 by the adder 30 is input and output from the output terminal 19.

Next, the case of performing subtraction will be described. At this time, SW26 is the inverter 25 side, and SW29 is the memory 28.
Select the side. The output signal of SW14 is the inverter 25
Is converted to 1's complement and input to the adder 30. Further, the value 1 held in the memory 28 is also input to the adder 30, so that the output signal from the SW 14 becomes a complement of 2 and is added to the output signal of the delay correction circuit 10 and the adder 30. . That is, the result of subtracting the output signal of SW14 from the output signal of the delay correction circuit 10 is output to the output terminal 19. As described above, also in the fourth embodiment, the same signal processing as in the first embodiment can be performed.

Example 5. FIG. 7 shows a fifth embodiment according to the present invention.
This will be described below. In the figure, the same symbols as those in FIG. 4 and FIG. In the fifth embodiment, the output signal of the delay correction circuit 10
The addition and subtraction with the output signal of SW14 are performed by the same circuit as in the fourth embodiment.
When the memory 27 side is selected by SW29, the addition signal is output, and the inverter 25 side is switched by SW29.
When the memory 28 side is selected by, the subtraction signal is output.
As described above, also in the fifth embodiment, the same signal processing as in the second embodiment can be performed.

Example 6. FIG. 8 shows a sixth embodiment according to the present invention.
This will be described below. In the figure, the same symbols as those in FIG. 5 and FIG. The sixth embodiment is similar to the fifth embodiment in that the addition and subtraction of the output signal of the delay correction circuit 10 and the output signal of the SW14 are performed by the same circuit as the fourth embodiment. Signal processing can be performed.

[0036]

According to the first aspect of the present invention, the signal extracted by the high-frequency emphasis filter is subjected to the nonlinear processing by the nonlinear circuit and then added to the input image signal to enhance the contour. Further, it is possible to provide an image quality correction apparatus capable of removing noise by subtracting.

According to the invention of claim 2, two selectors can be controlled by one control signal.

According to the third aspect of the invention, the signal extracted by the mid-range emphasis filter is subjected to the nonlinear processing by the nonlinear circuit, and then added to the input image signal to enhance the contour. Furthermore, it is possible to provide an image quality correction device capable of removing noise by performing nonlinear processing on a signal extracted by a high-frequency emphasis filter by a nonlinear circuit and then subtracting the signal from an input image signal.

According to the invention of claim 4, three selectors can be controlled by one control signal.

According to the fifth aspect of the present invention, the signal extracted by the mid-range emphasis filter is subjected to nonlinear processing by the nonlinear circuit and then added to the input image signal to enhance the contour. The noise extracted by the high-frequency emphasis filter can be removed by performing non-linear processing by the non-linear circuit and then subtracting it from the input image signal. The signal obtained by adding the output of the above is subjected to nonlinear processing by a nonlinear circuit, and then added to the input image signal to correct the edge enhancement and the reduction of the high frequency signal caused by the aperture effect in the D / A converter inserted in the subsequent stage. It is possible to provide an image quality correction device that can perform the image quality correction.

According to the invention of claim 6, three selectors can be controlled by one control signal.

According to the invention of claim 7, the adder, the subtractor and the selector can be constructed with a small circuit scale.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an image quality correction apparatus according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram of the first nonlinear circuit of the first embodiment.

FIG. 3 is a characteristic diagram of the second nonlinear circuit of the first embodiment.

FIG. 4 is a block circuit diagram showing an image quality correction device according to a second embodiment of the present invention.

FIG. 5 is a block circuit diagram showing an image quality correction device according to a third embodiment of the present invention.

FIG. 6 is a block circuit diagram showing an image quality correction device according to a fourth embodiment of the present invention.

FIG. 7 is a block circuit diagram showing an image quality correction device according to a fifth embodiment of the present invention.

FIG. 8 is a block circuit diagram showing an image quality correction device according to a sixth embodiment of the present invention.

FIG. 9 is a block circuit diagram showing an image quality correction device in the related art.

[Explanation of symbols]

10 delay correction circuit, 11 HPF, 12, 13 non-linear circuit, 14, 17, 21, 26, 29 SW, 15,
22,30 Adder, 16 Subtractor, 20 BPF, 2
5 Inverter, 27, 28 memory.

[Procedure amendment]

[Submission date] February 28, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 7

[Correction method] Change

[Correction content]

Claims (7)

[Claims] 1. A high-frequency emphasis filter for emphasizing a high frequency band of an image signal, a first non-linear circuit for suppressing a minute amplitude component of the filter output or a minute amplitude component and a large amplitude component, and a large amplitude of the filter output. A second non-linear circuit that suppresses a component, a first selection circuit that selects the output of the first or second non-linear circuit, addition result and subtraction of the input image signal and the output of the first selection circuit An image quality correction apparatus comprising an arithmetic unit that outputs a result and a second selection circuit that selects an addition result or a subtraction result of the arithmetic unit. 2. When the first selection circuit selects the first nonlinear circuit, the second selection circuit selects an addition result, and the first selection circuit selects the second nonlinear circuit. 2. The image quality correction apparatus according to claim 1, further comprising means for interlocking the second selection circuit so as to select a subtraction result when selected. 3. A mid-range emphasis filter for emphasizing a middle range of an input image signal, a high-range emphasis filter for emphasizing a high range of the input image signal, and an output signal of the middle-range emphasis filter or the high-range emphasis filter. A third selecting circuit for selecting, a first non-linear circuit for suppressing the minute amplitude component or the minute amplitude component and the large amplitude component of the selecting signal, and a second nonlinear circuit for suppressing the large amplitude component of the selecting signal A first selection circuit for selecting the output of the first or second nonlinear circuit, an arithmetic unit for outputting the addition result and the subtraction result of the input image signal and the output of the first selection circuit, and the arithmetic operation Image quality correction device having a second selection circuit for selecting the addition result or the subtraction result of the digital signal processor. 4. When the third selection circuit selects the mid-range emphasis filter, the first selection circuit selects the first nonlinear circuit and the second selection circuit selects an addition result. When the third selection circuit selects the high-frequency emphasis filter, the first selection circuit selects the second nonlinear circuit and the second selection circuit selects the subtraction result. The image quality correction apparatus according to claim 3, further comprising: 5. A mid-range emphasis filter that emphasizes the mid-range of an input image signal, a high-range emphasis filter that emphasizes the high-range of the input image signal, and outputs of the middle-range emphasis filter and the high-range emphasis filter. An adder for adding, a fourth selection circuit for selecting the output of the above-mentioned mid-range emphasis filter, the output of the above-mentioned high-range emphasis filter or the output of the above-mentioned adder, and a minute amplitude component or a minute amplitude component of this selection signal A first non-linear circuit for suppressing an amplitude component, a second non-linear circuit for suppressing a large amplitude component of the selection signal, a first selection circuit for selecting the output of the first or second non-linear circuit, An image quality correction device comprising an arithmetic unit that outputs an addition result and a subtraction result of the input image signal and the output of the first selection circuit, and a second selection circuit that selects the addition result or the subtraction result of the arithmetic unit. 6. The fourth selection circuit selects the first non-linear circuit when the fourth selection circuit selects the mid-range emphasis filter, and the second selection circuit outputs the addition results respectively. When the fourth selection circuit selects the output of the adder, the first selection circuit selects the first nonlinear circuit and the second selection circuit selects the addition result, When the fourth selection circuit selects the high-frequency emphasis filter, the first selection circuit selects the second nonlinear circuit and the second selection circuit selects the subtraction result. The image quality correction apparatus according to claim 5, further comprising: 7. The part formed by the arithmetic circuit and the second selection circuit according to claim 1, claim 3 or claim 5, wherein the output of the first selection circuit and the first selection circuit. Output circuit of the fifth selection circuit for selecting any one of the inverted signals, a sixth selection circuit for selecting either one or a 0 value, the input image signal and the output of the fifth selection circuit. And an adder that adds the outputs of the sixth selection circuit.