JP4768510B2 - Image quality improving apparatus and image quality improving method - Google Patents

Description

  The present invention relates to an apparatus for improving the image quality of a display device represented by a liquid crystal display device.

  A two-dimensional low-pass filter that extracts a two-dimensional low-frequency component from the input video signal is provided, and the two-dimensional low-frequency component extracted by the two-dimensional low-pass filter is subtracted from the original input video signal. An image quality improving apparatus that improves the sharpness of an image by adding a correction signal (high frequency component) that is an edge component of the image to the original input video signal is known (see Patent Document 1). ).

  FIG. 9 shows a schematic configuration of a conventional image quality improvement apparatus including a two-dimensional low-pass filter. Referring to FIG. 9, the image quality improving apparatus includes a two-dimensional low-pass filter 12, a subtracter 13, a multiplier 14, an adder 15, and a correction gain setting unit 16.

  The video signal S input from the input terminal YIN is supplied to each of the two-dimensional low-pass filter 12, the subtractor 13, and the adder 15. Here, the video signal supplied to the two-dimensional low-pass filter 12 is S1, the video signal supplied to the subtractor 13 is S2, and the video signal supplied to the adder 15 is S3.

  The two-dimensional low-pass filter 12 is composed of a known linear phase FIR filter or IIR filter, and cuts off the high-frequency component for each of the horizontal direction and the vertical direction of the video signal S1 to perform a two-dimensional operation. The low frequency component of is extracted. The two-dimensional low-frequency component extracted by the two-dimensional low-pass filter 12 is supplied to the subtractor 13. Here, the horizontal direction and the vertical direction of the video signal refer to the horizontal direction and the vertical direction of an image displayed by the video signal.

  The subtractor 13 subtracts the two-dimensional low-frequency component extracted from the video signal S1 supplied from the two-dimensional low-pass filter 12 from the video signal S2 supplied from the input terminal YIN, thereby A high frequency component which is an edge component is extracted. The high frequency component extracted by the subtractor 13 is supplied to the adder 15 via the multiplier 14.

  The multiplier 14 adjusts the amplitude of the output (high frequency component) of the subtractor 13 according to the control signal supplied from the correction gain setting unit 16. The adder 15 adds the high frequency component whose amplitude is adjusted by the multiplier 14 to the video signal S3 supplied from the input terminal YIN. The amount of the high frequency component added to the video signal S3 can be freely adjusted by a control signal supplied to the multiplier 14.

  The correction gain setting unit 16 provides an amplitude adjustment amount in the multiplier 14. The user can freely set the amplitude adjustment amount with the correction gain setting unit 16, and can thereby freely set the image quality improvement amount by the present apparatus.

  Since the two-dimensional low-pass filter 12 passes only the low-frequency band, its output waveform is shown in FIG. 10 (a) as shown in FIG. 10 (b). The input signal waveform has a rounded edge (low frequency component signal waveform). Since the subtracter 13 subtracts the output waveform of the two-dimensional low-pass filter 12 shown in FIG. 10B from the input signal waveform shown in FIG. 10A, the output waveform is shown in FIG. As shown in (c), an edge signal waveform (signal waveform of a high frequency component) for emphasizing rising edges and falling edges of the input video signal is obtained.

  Since the adder 15 adds the edge signal waveform shown in FIG. 10C to the input signal waveform shown in FIG. 10A, the output waveform is as shown in FIG. The waveform emphasizes the rising edge and falling edge of the input video signal. By enhancing the edges of the input video signal in this way, the sharpness of the boundary (contour) between the white area and the black area on the display image is improved.

  The amplitude of the output waveform (edge signal) of the subtracter 13 is adjusted by the multiplier 14. The multiplier 14 adjusts the amplitude of the output waveform (edge signal) of the subtractor 13 according to the control signal from the correction gain setting unit 16. When the amplitude is increased, the edge enhancement degree in the output waveform of the adder 15 increases, and as a result, the effect of improving the edge sharpness on the display image increases. On the other hand, when the amplitude is reduced, the edge enhancement degree in the output waveform of the adder 15 is reduced, so that the effect of improving the edge sharpness on the display image is reduced.

  By the way, in a display apparatus represented by a liquid crystal display device, blurring of a moving image due to a retina afterimage may occur. Moving image blur due to a retina afterimage is a phenomenon in which when a moving image with a fast motion is displayed, a retina afterimage of a current frame image overlaps with a next frame image and the moving image looks blurred.

  In order to improve the blurring feeling of the moving image due to the above-mentioned retinal afterimage, there is an image quality improvement apparatus shown in FIG. 9 in which a frame memory is provided at the input stage of the two-dimensional low-pass filter 12. According to this configuration, the subtracter 13 extracts the two-dimensional low-frequency signal extracted from the video signal S1 delayed from the video signal S1 supplied from the two-dimensional low-pass filter 12 from the video signal S2 supplied from the input terminal YIN. A three-dimensional high frequency component is extracted by subtracting the high frequency component. Here, the three-dimensional high frequency component includes three elements, a horizontal component, a vertical component, and a temporal component.

Since the video signal S1 is delayed by n frames with respect to the video signal S3, the adder 15 converts the three-dimensional high-frequency component into the video signal S3 inputted n frames after the video signal S1. Will be added. For example, in the case where the video signal S1 is delayed by one frame with respect to the video signal S3 in the frame memory, the subtractor 13 extracts the two-dimensional low-frequency component extracted from the video signal of the nth frame, When a three-dimensional high-frequency component is extracted by subtracting from the video signal of the (n + 1) th frame, the adder 15 uses the three-dimensional high-frequency component extracted by the subtracter 13 as the video of the (n + 1) th frame. Will be added to the signal. In this way, by adding the three-dimensional high frequency component to the video signal, the blurring feeling of the moving image is reduced.
JP 2003-46810 A

  According to the image quality improvement apparatus shown in FIG. 9, a correction signal (high frequency component) obtained by subtracting a two-dimensional low frequency component from the input video signal is added to the input video signal, thereby sharpening the video. The degree can be improved. However, since this image quality improvement apparatus is adapted to perform appropriate image quality correction in conformity with the input video, the image quality may deteriorate depending on the input video. Hereinafter, an example that causes image quality deterioration will be described in detail.

  When the correction signal (high frequency component) that is the edge component of the image is added to the input video signal to improve the sharpness, the level of the input video signal is the black level (the darkest level of the video signal) or the white level (video If the signal is in the vicinity of the brightest level of the signal, the output video signal is saturated at the black level or the white level due to the addition of the correction signal, and the gradation of the video is lost.

  Further, when a correction signal is added to a video with a large high frequency component (that is, an image having a strong edge), the edge portion is further emphasized. On the contrary, excessive edge enhancement may cause a sense of incongruity. In other words, for an image including a certain high frequency component, it is possible to provide an image having a natural edge if the correction signal is not added.

  Furthermore, when the sharpness is improved by adding the high-frequency component of the input video signal to the input video signal as a correction signal, if the input video signal contains noise, the noise component is also added by adding the correction signal. As a result, the image quality deteriorates.

  Even in the image quality improvement apparatus in which the frame memory is provided in the input stage of the two-dimensional low-pass filter 12, the above-described problem occurs because appropriate image quality correction is performed in accordance with the input video. In addition, there are the following problems.

  When the screen is switched to a completely different screen, such as a video scene change, the correction signal (3) is obtained by subtracting the two-dimensional low-frequency component extracted from the video signal before screen switching from the video signal after screen switching. Dimensional high-frequency component). In this case, since the images before and after the screen switching are not related, a large correction signal is acquired over the entire screen. Therefore, when the adjustment amount of the sharpness in the correction gain setting unit 16 is set to be large, a correction signal having a large amplitude is added to the input video signal as it is due to screen switching, and as a result, excessive sharpness is obtained. The image quality is degraded instead.

  An object of the present invention is to provide an image quality improving apparatus capable of solving the above-described problems and performing appropriate image quality correction in conformity with an input video.

  In order to achieve the above object, the present invention comprises any one of the following first to fourth modes as a configuration for controlling the amplitude of a correction signal in conformity with an input video.

In the first aspect, a low-pass filter that extracts a low-frequency component related to at least one of a vertical direction and a horizontal direction of an image displayed by the input video signal from the input video signal, and the input video signal A subtractor that subtracts the low-frequency component extracted by the low-pass filter to acquire a high-frequency component, and an adder that adds the high-frequency component acquired by the subtractor to the input video signal as a correction signal And an input level adaptive control unit that controls the amplitude of the correction signal added to the input video signal based on the level of the input video signal to which the input video signal is input. The input level adaptive control unit determines a first range from a black level indicating the darkest level to a first reference level higher than the black level and a brightest level of the input video signal input. It is added to the input video signal when it is within any one of a second range from a white level shown to a second reference level lower than the white level and higher than the first reference level. The amplitude of the correction signal is reduced .

  The second embodiment is an apparatus for improving the image quality of an input video signal input in units of frames, and extracts a high frequency component for extracting a high frequency component related to the video signal of the nth (n is a natural number) frame. Means, an adder for adding the high frequency component extracted by the high frequency component extraction means to the video signal of the n + m (m is a natural number) frame as a correction signal, and the video signal of the n + m frame A first range from a black level indicating the darkest level to a first reference level higher than the black level, and a white level indicating the brightest level, lower than the white level, the first reference The amplitude of the correction signal added to the video signal of the n + m-th frame is reduced when it is within any of the second range up to the second reference level higher than the level. It has an input level adaptive control unit that, the.

  According to the first and second embodiments, when the input video signal level is near the black level or the white level, the input level adaptive control unit decreases the amplitude of the correction signal, so that the output video signal is It is possible to suppress saturation at the black level or the white level.

The third form is the correction signal added to the input video signal when the absolute value of the amplitude of the high frequency component acquired by the subtracter exceeds a reference value in the first form. A correction level adaptive control unit for reducing the amplitude is further included .

  According to the third aspect, when the absolute value of the amplitude of the correction signal exceeds the reference value, the correction level adaptive control unit decreases the amplitude of the correction signal, so that an image with a large high frequency component ( That is, it is possible to suppress an excessive sharpness correction for an image having a strong edge.

  The fourth embodiment is an apparatus for improving the image quality of an input video signal input in units of frames, and extracts a high frequency component for extracting a high frequency component related to the video signal of the nth (n is a natural number) frame. Means, an adder for adding the high frequency component extracted by the high frequency component extraction means as a correction signal to the video signal of the n + m (m is a natural number) frame, and extraction by the high frequency component extraction means A correction level adaptive control unit that reduces the amplitude of the correction signal added to the video signal of the n + m-th frame when the absolute value of the amplitude of the high frequency component thus generated exceeds a reference value.

  According to the fourth aspect, when the absolute value of the amplitude of the correction signal exceeds the reference value, the correction level adaptive control unit decreases the amplitude of the correction signal, so that an image with a large high-frequency component ( That is, it is possible to suppress an excessive sharpness correction for an image in which the screen is switched to a completely different screen such as an image having a strong edge or a scene change.

  In each of the first to fourth embodiments described above, a noise reducer that removes noise that is a high-frequency minute amplitude component from a high-frequency component signal added to the video signal as a correction signal may be provided. In this case, the noise component of the correction signal is reduced in advance, and then the correction signal is added to the input video signal. Therefore, even if a noise component is present in the input video signal, the noise is enhanced by adding the correction signal. There is no end to it.

  According to the present invention, the configuration that controls the amplitude of the correction signal in accordance with the input video has the following effects.

  According to the first and second aspects of the present invention, when the level of the input video signal is near the black level or the white level, the sharpness correction is suppressed, so that the output video signal is It can be suppressed that the gradation of the video is lost due to saturation. Therefore, it is possible to provide a video screen with excellent gradation as compared with a conventional image quality improving apparatus.

  According to the third aspect of the present invention, since an excessive edge emphasis can be suppressed for a video with a large high frequency component (that is, an image having a strong edge), it has a natural edge without a sense of incongruity. Video can be provided.

  According to the fourth aspect of the present invention, in addition to the effect of the third aspect, with respect to a video that switches to a completely different screen such as a scene change, the image quality deteriorates due to an excessive correction signal. Can be suppressed. Therefore, it is possible to provide a video screen with higher image quality than the conventional one.

  Moreover, in the present invention, the one having a noise reducer can remove the noise contained in the correction signal, thereby providing a video screen with less noise.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of an image quality improvement apparatus according to an embodiment of the present invention. Referring to FIG. 1, the image quality improvement apparatus includes a frame memory 11, a two-dimensional low-pass filter 12, a subtractor 13, a multiplier 14, an adder 15, a correction gain setting unit 16, a noise reducer 21, and a correction level adaptation. It comprises a control unit 22, a multiplier 23, an input level adaptive control unit 24, and a multiplier 25. The two-dimensional low-pass filter 12, the subtractor 13, the multiplier 14, the adder 15, and the correction gain setting unit 16 are the same as those described in the conventional image quality improving apparatus shown in FIG.

  The video signal S input from the input terminal YIN is supplied to each of the frame memory 11, the subtractor 13, the adder 15, and the input level adaptive control unit 24. Here, the video signal supplied to the frame memory 11 is S1, the video signal supplied to the subtractor 13 is S2, the video signal supplied to the adder 15 is S3, and the video signal supplied to the input level adaptive control unit 24. The signal is S4.

  The frame memory 11 delays the video signal S1 supplied from the input terminal IN in units of frames. In the frame memory 11, the video signal S1 can be delayed by n (n is a natural number) frames. The video signal S1 is delayed by the frame memory 11, and then supplied to the two-dimensional low-pass filter 12.

  The two-dimensional low-pass filter 12 is composed of a known linear phase FIR filter or IIR filter, and is inputted from the frame memory 11 in the horizontal and vertical directions of the frame-delayed video signal S1. For each, a high-frequency component is blocked and a two-dimensional low-frequency component is extracted. The two-dimensional low-frequency component extracted by the two-dimensional low-pass filter 12 is supplied to the subtractor 13. Here, the horizontal direction and the vertical direction of the video signal refer to the horizontal direction and the vertical direction of an image displayed by the video signal.

  The subtractor 13 subtracts the two-dimensional low-frequency component extracted from the frame-delayed video signal S1 supplied from the two-dimensional low-pass filter 12 from the video signal S2 supplied from the input terminal YIN. Then, a three-dimensional high frequency component is extracted. Here, the three-dimensional high frequency component includes three elements, a horizontal component, a vertical component, and a temporal component. The three-dimensional high-frequency component extracted by the subtracter 13 is supplied to the adder 15 via the multiplier 14 after the noise component is reduced by the noise reducer 21.

  Based on the amplitude of the three-dimensional high-frequency component supplied from the subtractor 13, the correction level adaptive control unit 22 performs correction that is added by the adder 15 when the absolute value of the amplitude exceeds the reference value. A signal for controlling the multiplier 23 is output so that the amplitude of the signal (three-dimensional high-frequency component) becomes small.

  When the level of the video signal S4 supplied from the input terminal YIN is near the white level or the black level, the input level adaptive control unit 24 specifically, the level of the video signal S4 is the black level indicating the darkest level. To a first reference level higher than the black level and a white level indicating the brightest level to a second reference level lower than the white level and higher than the first reference level. 2, a signal for controlling the multiplier 25 is output so that the amplitude of the correction signal (three-dimensional high-frequency component) added by the adder 15 becomes small. To do. Here, the first and second ranges define a range in which the output video signal is saturated at the black level or the white level due to the addition of the correction signal. The first and second reference levels are determined based on a result obtained by performing display based on a video signal using a display device to which the image quality improving apparatus is applied.

  The three multipliers 14, 23, and 25 are supplied from the control signal supplied from the correction gain setting unit 16, the control signal supplied from the correction level adaptive control unit 22, and the input level adaptive control unit 24. The amplitude of the output of the noise reducer 21 (noise-reduced three-dimensional high-frequency component) is adjusted according to the control signal.

  The adder 15 adds the correction signal of the three-dimensional high-frequency component whose amplitude is adjusted by the multiplier 14 to the video signal S3 supplied from the input terminal YIN. The amplitude (edge adjustment amount) of the correction signal (three-dimensional high-frequency component) added to the video signal S3 is adjusted by a control signal supplied to the multiplier.

  The correction gain setting unit 16 provides an amplitude adjustment amount in the multiplier 14. The user can freely set the improvement amount of the image quality by this apparatus using the correction gain setting unit 16.

  According to the image quality improving apparatus of the present embodiment described above, the video signal supplied from the input terminal YIN is supplied to each of the frame memory 11, the subtracter 13, the adder 15, and the input level adaptive control unit 24. The video signal S1 is delayed by n frames from the video signal S3 by the frame memory 11. Therefore, the adder 15 adds the three-dimensional high frequency component to the video signal S3 input n frames after the video signal S1. For example, in the case where the video signal S1 is delayed by n frames with respect to the video signal S3 in the frame memory 11, the subtractor 13 extracts the two-dimensional low-frequency component extracted from the video signal of the nth frame. , N + m (m is a natural number) When the three-dimensional high-frequency component is extracted by subtracting from the video signal of the frame, the adder 15 extracts the three-dimensional high-frequency component extracted by the subtractor 13, This is added to the video signal of the (n + m) th frame. In this way, by adding the three-dimensional high-frequency component to the video signal, an effect of improving the sharpness of the edge on the display image can be obtained, and the blurring feeling of the moving image can be reduced.

  Also, the level of the video signal of the (n + m) th frame is in any one of the first range from the black level to the first reference level and the second range from the white level to the second reference level. In this case, the input level adaptive control unit 24 reduces the amplitude of the correction signal added to the video signal of the (n + m) th frame. Thereby, when the level of the input video signal is near the black level or the white level, it is possible to suppress the output video signal from being saturated at the black level or the white level due to the addition of the correction signal.

  Furthermore, when the absolute value of the amplitude of the three-dimensional high-frequency component extracted by the subtracter 13 exceeds the reference value, the correction level adaptive control unit 22 decreases the amplitude of the correction signal. Thereby, it is possible to suppress an excessive sharpness correction for a video with a large high frequency component (that is, an image having a strong edge) or a video in which the screen is switched to a completely different screen such as a scene change.

  Further, since the noise reducer 21 removes noise (high-frequency minute amplitude component) included in the correction signal of the three-dimensional high-frequency component extracted by the subtracter 13, the noise component is added together by adding the correction signal. Will not be enhanced.

  Note that the input level adaptive control by the input level adaptive control unit 24, the correction level adaptive control by the correction level adaptive control unit 22, and the noise removal by the noise reducer 21 may be performed in any order.

  Next, a specific configuration of the input level adaptive control unit 24 will be described.

  FIG. 2 is a block diagram illustrating a configuration example of the input level adaptive control unit 24. Referring to FIG. 2, the input level adaptive control unit 24 includes a white side inversion unit 31, a multiplier 32, a limiter 33, and a table conversion unit 34. The white side inversion unit 31 inverts the white signal from the intermediate luminance level for the input signal IN. By this inversion processing, all input signals IN are converted into signals from the black side to the intermediate luminance level. The video signal output from the white side inversion unit 31 (the signal in which the white side is inverted) is multiplied by A by the multiplier 32 and then output through the limiter 33. The limiter 33 limits the maximum value of the output signal. The table conversion unit 34 includes a table indicating the relationship between the correction gain and the coefficient A of the multiplier 32. With reference to this table, the multiplier 32 calculates the correction gain value supplied from the correction gain setting unit 16. The value of the coefficient A supplied to is determined. In the input level adaptive control unit 24 shown in FIG. 2, the white side processing is shared with the black side processing, thereby reducing the circuit scale and facilitating circuit realization. it can.

  FIG. 3 is a diagram illustrating input / output characteristics of the input level adaptive control unit 24. When the input signal IN is from the black side to the X level, the output value increases in proportion to the input (the portion of slope A in FIG. 3). However, when the input level exceeds X, the output value is limited to 1 (maximum value).

  The output signal of the input level adaptive control unit 24 is a signal indicating a control amount for adjusting the amplitude of the three-dimensional high-frequency component by the multiplier 25 connected in the subsequent stage. When the output value of the input level adaptive control unit 24 is set to “0”, the amplitude of the three-dimensional high-frequency component becomes “0”. When the output value of the input level adaptive control unit 24 is set to “1”, the amplitude of the three-dimensional high frequency component becomes maximum. When the input signal is on the white side of the intermediate luminance level, the target operation is performed based on the intermediate luminance level.

  The inclination A is set to a value that suppresses the sharpness improving effect on the black side or the white side. The set value of the slope A changes according to the input value (correction gain supplied from the correction gain setting unit 16). Specifically, as the input value (correction gain) is smaller, the start position X of the slope A is closer to the black side or the white side. Conversely, the larger the input value (correction gain), the closer the start position X of the slope A is to the intermediate luminance level. Although it is possible to obtain an output value from the correction gain by calculation based on the slope A, in this embodiment, the table conversion unit 34 refers to the table in order to make the circuit simpler. It has become.

  Next, a specific configuration of the correction level adaptive control unit 22 will be described.

  FIG. 4 is a block diagram illustrating a configuration example of the correction level adaptive control unit 22. Referring to FIG. 4, the correction level adaptive control unit 22 includes an absolute value processing unit 41, a multiplier 42, a limiter 43, and an inversion unit 44. The absolute value processing unit 41 acquires the absolute value of the input signal IN (correction signal). The multiplier 42 multiplies the output of the absolute value processing unit 41 by a coefficient B. The output of the multiplier 42 is supplied to the inversion unit 44 via the limiter 43. The inverting unit 44 performs an inverting process on the signal input via the limiter 43. In this inversion process, for example, when the output of the subtracter 13 shown in FIG. 10C is used as the input signal IN, the negative part is inverted so that it becomes the negative side.

  In the correction level adaptive control unit 22 shown in FIG. 4, the input signal IN is converted into an absolute value by the absolute value processing unit 41, multiplied by B by the multiplier 42, the maximum value is limited by the limiter 43, and the inversion unit 44 After being inverted, it is output as an output signal OUT.

  FIG. 5 is a diagram illustrating input / output characteristics of the correction level adaptive control unit 22. In the range where the absolute value of the amplitude of the input signal IN ranges from zero to X, the output value gradually decreases from “1” in inverse proportion to the input value, as indicated by the slope B in FIG. When the absolute value of the input amplitude exceeds X, the output value is fixed at 0 (minimum value).

  The output signal of the correction level adaptive control unit 22 is a signal indicating a control amount for adjusting the amplitude of the correction signal (three-dimensional high frequency component) by the multiplier 23 connected in the subsequent stage. When the output value of the correction level adaptive control unit 22 is “0”, the amplitude of the correction signal (three-dimensional high frequency component) is “0”. When the output value of the correction level adaptive control unit 22 is “1”, the amplitude of the correction signal (three-dimensional high frequency component) is maximized.

  FIG. 6 is a diagram illustrating input / output characteristics of the correction signal (three-dimensional high-frequency component) in the multiplier 14. In FIG. 6, the solid line indicates the characteristic when the correction level adaptive control is performed, and the broken line indicates the characteristic when the correction level adaptive control is not performed.

  When the correction level adaptive control does not work, the input / output is in a one-to-one relationship as shown by the straight line shown by the dotted line in FIG. On the other hand, when correction level adaptive control is performed, as shown by the solid line in FIG. 6, the output of the three-dimensional high-frequency component is large depending on the input until X1. As the signal amplitude increases, the output signal amplitude decreases. When the amplitude of the three-dimensional high frequency component exceeds X2 (corresponding to X in FIG. 5), the amplitude of the output signal becomes zero. As a result, when a large amplitude is generated in the three-dimensional high-frequency component due to a scene change or large amplitude change of the video, it is added to the input signal, and excessive sharpness correction is applied. Can not be.

  Next, a specific configuration of the noise reducer 21 will be described.

  FIG. 7 is a block diagram illustrating a configuration example of the noise reducer 21. Referring to FIG. 7, the noise reducer 21 includes a high-pass filter 51, a subtracter 52, a coring 53, and an adder 54. The input signal IN (output of the subtractor 13) is supplied to the high-pass filter 51 and the subtractor 52. The high-pass filter 51 extracts a high-frequency component from the input signal IN and supplies the extracted high-frequency component signal to the subtractor 52 and the coring 53. The subtracter 52 subtracts the signal extracted by the high-pass filter 51 from the input signal IN and supplies the subtracted signal to the adder 54. The coring 53 supplies a signal obtained by removing a minute amplitude component from the high-frequency component signal extracted by the high-pass filter 51 to the adder 54. The adder 54 adds the signal from which the high frequency component has been subtracted by the subtracter 52 and the signal from which the high amplitude component has been removed by the coring 53. As a result, a signal obtained by removing a high-frequency minute amplitude component from the input signal IN is obtained. The high-frequency minute amplitude component is often a noise component, and therefore the noise component can be reduced by the configuration of FIG.

  The noise reducer 21 is not limited to the configuration shown in FIG. As long as the noise reducer 21 can remove noise included in the correction signal of the three-dimensional high-frequency component extracted by the subtractor 13, a circuit using another generally established technique is used. May be used.

  The configuration of the image quality improvement apparatus shown in FIG. 1 is to improve the sharpness of a luminance signal when the input signal is a luminance color difference signal. When the input signal is an RGB three primary color signal, the configuration of FIG. 1 may be provided for each of the three primary color signals. However, when the configuration of FIG. 1 is provided for each of the three primary color signals, the circuit scale is tripled. In order to realize a device with a small circuit scale, it is effective to apply the configuration of FIG. 1 only to the G signal that has the greatest influence on the luminance signal component.

  It is also effective to obtain a luminance signal from the three primary color signals and apply the configuration of FIG. 1 to this luminance signal. Below, other embodiment of this invention which has such a structure is described.

  FIG. 8 is a block diagram showing a schematic configuration of an image quality improvement apparatus according to another embodiment of the present invention. Referring to FIG. 8, the image quality improvement apparatus includes an inverse matrix circuit 61, a matrix circuit 62, a luminance component extraction unit 63, and a black and white maximum value detection unit 64 in addition to the configuration of FIG. In FIG. 8, blocks having the same configuration as in FIG. 1 and necessary for each RGB signal are given R, G, or B characters at the end of the reference numerals.

  The input signal RIN is supplied to the subtractor 13R and the adder 15R, the input signal GIN is supplied to the subtractor 13G and the adder 15G, and the input signal BIN is supplied to the subtractor 13B and the adder 15B. The input signals RIN, GIN, and BIN are supplied to the inverse matrix circuit 61 and the black and white maximum value detection unit 64, respectively.

  The inverse matrix circuit 61 converts the input RGB three primary color signals into YUV luminance color difference signals and outputs them. In general, conversion coefficients necessary for inverse matrix conversion vary depending on the television signal system. Here, the inverse matrix circuit 61 has any configuration as long as it can obtain the luminance signal component from the RGB three primary color signals and restore the RGB three primary color signals from the converted luminance color difference signals. There may be, and it is not particular about the circuit of a specific television signal system. A two-dimensional low-frequency component is extracted from the luminance signal Y supplied from the inverse matrix circuit 61 by the frame memory 11 and the two-dimensional low-pass filter 12.

  The matrix circuit 62 receives the two-dimensional low-frequency component of the luminance signal extracted by the frame memory 11 and the two-dimensional low-pass filter 12 and the two types of color difference signals U and V supplied from the inverse matrix circuit 61. , Converted into RGB primary color signals and supplied to RGB subtracters 13R, 13G, and 13B.

  The subtractor 13R subtracts the frame-delayed two-dimensional low-frequency component from the input signal RIN to extract a three-dimensional high-frequency component, and the extracted three-dimensional high-frequency component is sent to the noise reducer 21R. Supply. The subtractor 13G subtracts the frame-delayed two-dimensional low-frequency component from the input signal GIN to extract a three-dimensional high-frequency component, and outputs the extracted three-dimensional high-frequency component to the noise reducer 21G. Supply. The subtractor 13B subtracts the frame-delayed two-dimensional low-frequency component from the input signal BIN to extract a three-dimensional high-frequency component, and outputs the extracted three-dimensional high-frequency component to the noise reducer 21B. Supply. The signals of the three-dimensional high frequency components from the subtracters 13R, 13G, and 13B are also supplied to the luminance component extraction unit 63, respectively.

  The luminance component extraction unit 63 obtains a luminance component from the RGB individual three-dimensional high-frequency components, and supplies the obtained luminance component signal to the correction level adaptive control unit 22. Thereby, the amount of improvement in sharpness is adjusted by the amplitude of the luminance component of the RGB three-dimensional high-frequency component that improves the sharpness.

  The black-and-white maximum value detection unit 64 obtains the level of the signal on the most black side or white side of the RGB signals with reference to the intermediate luminance level for each level of the input signals RIN, GIN, and BIN, and determines the level as the input level. The data is output to the adaptive control unit 24. As a result, the amount of improvement in the sharpness of the entire RGB signal is adjusted according to the level of the signal that is most black or white among the RGB signals, that is, the signal that is most likely to saturate the output signal when the sharpness is improved. The

  According to the image quality improvement apparatus shown in FIG. 8, it is possible to suppress the improvement of sharpness and the bias control of the improvement amount being biased toward a specific color signal.

  The image quality improvement apparatus of each embodiment described above is an example of the present invention, and the configuration and operation thereof can be changed as appropriate without departing from the spirit of the invention.

  For example, the image quality improvement apparatus shown in FIG. 1 may be configured without the frame memory 11. Hereinafter, the operation when the frame memory 11 is not provided will be briefly described.

  The subtractor 13 extracts a high-frequency component by subtracting the two-dimensional low-frequency component extracted from the video signal of the nth frame from the video signal of the n-th frame. Then, the adder 15 adds the high frequency component extracted by the subtracter 13 to the video signal of the nth frame. In this way, by adding the high frequency component to the video signal, an effect of improving the sharpness of the edge on the display image is obtained.

  Further, the level of the video signal of the nth frame is in any one of the first range from the black level to the first reference level and the second range from the white level to the second reference level. In some cases, the input level adaptive control unit 24 reduces the amplitude of the correction signal added to the video signal of the nth frame. Thereby, when the level of the input video signal is near the black level or the white level, it is possible to suppress the output video signal from being saturated at the black level or the white level due to the addition of the correction signal.

  Furthermore, when the absolute value of the amplitude of the correction signal of the high frequency component extracted by the subtracter 13 exceeds the reference value, the correction level adaptive control unit 22 decreases the amplitude of the correction signal. Thereby, it is possible to suppress an excessive sharpness correction for a video with a large high frequency component (that is, an image having a strong edge).

  Moreover, in the image quality improvement apparatus of each embodiment, from the viewpoint of suppressing excessive sharpness correction, the input level adaptive control unit may be omitted.

  Furthermore, in the image quality improvement apparatus of each embodiment, from the viewpoint of suppressing the output video signal from being saturated at the black level or the white level, the correction level adaptive control unit may be omitted.

  Further, the three-dimensional high-frequency component extracting means comprising the frame memory 11, the two-dimensional low-frequency filter 12 and the subtractor 13 extracts and extracts the high-frequency component relating to the video signal of the nth frame. Any configuration may be used as long as the high frequency component can be added to the video signal of the (n + m) th frame. For example, the frame memory 11 may be provided on the output stage side of the two-dimensional low-pass filter 12, between the subtractor 13 and the multiplier 14, or on the output stage side of the multiplier 14.

  Further, although the high frequency component is extracted for both horizontal and vertical, the high frequency component may be extracted for either horizontal or vertical. In this case, improvement of sharpness and blurring of moving images are suppressed with respect to one of horizontal and vertical, and the amplitude of the correction signal is adjusted by the input level adaptive control unit and the correction level adaptive control unit.

  The image quality improving apparatus of the present invention described above can be applied to display devices in general. Further, the image quality improving apparatus of the present invention can be applied to an interlaced display device in which a frame includes an odd field and an even field in addition to a noninterlaced display device. When applied to the interlace method, the operation can be described by replacing “frame” with “field” in the above description.

1 is a block diagram illustrating an overall configuration of an image quality improvement apparatus according to an embodiment of the present invention. It is a block diagram which shows the structure of the input level adaptive control part shown in FIG. FIG. 3 is a characteristic diagram showing input / output characteristics of the input level adaptive control unit shown in FIG. 2. It is a block diagram which shows the structure of the correction level adaptive control part shown in FIG. FIG. 5 is a characteristic diagram showing input / output characteristics of the correction level adaptive control unit shown in FIG. 4. It is a figure for demonstrating the operation | movement of correction level adaptive control. It is a block diagram which shows the structure of the noise reducer shown in FIG. It is a block diagram which shows the structure of the image quality improvement apparatus which is other embodiment of this invention. It is a block diagram which shows the structure of the conventional image quality improvement apparatus. FIG. 10 is a waveform diagram showing outputs of a two-dimensional low-pass filter, a subtracter, and an adder shown in FIG. 9.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Frame memory 12 Two-dimensional low-pass filter 13 Subtractor 14 Multiplier 15 Adder 16 Correction gain setting part 21 Noise reducer 22 Correction level adaptive control part 23 Multiplier 24 Input level adaptive control part 25 Multiplier

Claims (14)

A low-pass filter that extracts, from an input video signal, a low-frequency component relating to at least one of a vertical direction and a horizontal direction of an image displayed by the input video signal;
A subtractor for obtaining a high frequency component by subtracting a low frequency component extracted by the low frequency filter from the input video signal;
An adder for adding the high frequency component acquired by the subtractor to the input video signal as a correction signal;
The input video signal is input, based on the level of the inputted input video signal, have a, an input level adaptive control unit for controlling the amplitude of the correction signal is added to the input video signal,
The input level adaptive control unit determines a first range from a black level indicating the darkest level to a first reference level higher than the black level and a brightest level of the input video signal input. It is added to the input video signal when it is within any one of a second range from a white level shown to a second reference level lower than the white level and higher than the first reference level. An image quality improving apparatus for reducing the amplitude of the correction signal .   A correction level adaptive control unit that reduces the amplitude of the correction signal added to the input video signal when the absolute value of the amplitude of the high frequency component acquired by the subtracter exceeds a reference value; The image quality improving apparatus according to claim 1. A noise reducer for removing noise that is a high-frequency minute amplitude component from the high-frequency component signal acquired by the subtractor;
The adder adds the high frequency components from which noise is removed in the input video signal as a correction signal in the noise reducing apparatus, the image quality improving apparatus according to claim 1 or 2. An apparatus for improving the image quality of an input video signal input in units of frames,
high-frequency component extraction means for extracting a high-frequency component relating to the video signal of the nth (n is a natural number) frame;
An adder for adding the high frequency component extracted by the high frequency component extraction means to the video signal of the (n + m) th frame (m is a natural number) as a correction signal;
From the black level indicating the darkest level to the first reference level higher than the black level, and from the white level indicating the brightest level, the level of the video signal of the n + mth frame The correction signal added to the video signal of the (n + m) th frame when it is within any of the second range up to a second reference level that is lower than the first reference level and higher than the first reference level And an input level adaptive control unit that reduces the amplitude of the image quality improvement device. When the absolute value of the amplitude of the high-frequency component extracted by the high-frequency component extraction means exceeds a reference value, the correction signal added to the video signal of the n + m (m is a natural number) frame The image quality improvement apparatus according to claim 4 , further comprising a correction level adaptive control unit that reduces the amplitude. An apparatus for improving the image quality of an input video signal input in units of frames,
high-frequency component extraction means for extracting a high-frequency component relating to the video signal of the nth (n is a natural number) frame;
An adder for adding the high frequency component extracted by the high frequency component extraction means to the video signal of the (n + m) th frame (m is a natural number) as a correction signal;
Correction for reducing the amplitude of the correction signal added to the video signal of the n + m-th frame when the absolute value of the amplitude of the high-frequency component extracted by the high-frequency component extraction means exceeds a reference value And an image quality improving apparatus. A noise reducer for removing noise that is a high-frequency minute amplitude component from the high-frequency frequency component correction signal extracted by the high-frequency component extraction means;
The image quality improvement according to any one of claims 4 to 6 , wherein the adder adds a high frequency component from which noise has been removed by the noise reducer to a video signal of the n + m-th frame as a correction signal. apparatus. The high frequency component extraction means is
A frame memory for delaying the input video signal in units of frames;
A low-pass filter for extracting a low-frequency component relating to at least one of a horizontal direction and a vertical direction of an image displayed by the input video signal from the video signal of the n-th frame output from the frame memory; ,
The subtractor which subtracts the low frequency component extracted by the low frequency filter from the video signal of the n + m-th frame and acquires a high frequency component, according to any one of claims 4 to 7. The image quality improvement apparatus described. A frequency component extraction step of extracting a low frequency component relating to at least one of a vertical direction and a horizontal direction of an image displayed by the input video signal from the input video signal;
A high frequency component acquisition step for acquiring a high frequency component by subtracting the low frequency component extracted in the frequency component extraction step from the input video signal;
A correction signal addition step of adding the high frequency component acquired in the high frequency component acquisition step to the input video signal as a correction signal;
The inputs the input video signal, based on the level of the input the input video signal, look including a input level adaptive control step of controlling the amplitude of the correction signal is added to the input video signal,
In the input level adaptive control step, the level of the input video signal that has been input is selected from a black level indicating the darkest level to a first reference level higher than the black level, and a brightest level. It is added to the input video signal when it is within any one of a second range from a white level shown to a second reference level lower than the white level and higher than the first reference level. A method for improving image quality , comprising reducing the amplitude of the correction signal . A correction level adaptive control step for reducing the amplitude of the correction signal added to the input video signal when the absolute value of the amplitude of the high frequency component acquired in the high frequency component acquisition step exceeds a reference value ; The image quality improvement method according to claim 9 , further comprising: The noise reduction step of removing noise is small amplitude component of the high band from the signal of the high frequency component obtained in the high frequency components acquisition step, further comprising, an image quality improving method according to claim 9 or 10. A method for improving the image quality of an input video signal input in units of frames,
a high-frequency component extraction step for extracting a high-frequency component relating to the video signal of the nth (n is a natural number) frame;
A correction signal addition step of adding the high frequency component extracted in the high frequency component extraction step as a correction signal to the video signal of the n + m (m is a natural number) frame;
From the black level indicating the darkest level to the first reference level higher than the black level, and from the white level indicating the brightest level, the level of the video signal of the n + mth frame The correction signal added to the video signal of the (n + m) th frame when it is within any of the second range up to a second reference level that is lower than the first reference level and higher than the first reference level And an input level adaptive control step for reducing the amplitude of the image quality improvement method. A method for improving the image quality of an input video signal input in units of frames,
a high-frequency component extraction step for extracting a high-frequency component relating to the video signal of the nth (n is a natural number) frame;
A correction signal addition step of adding the high frequency component extracted in the high frequency component extraction step as a correction signal to the video signal of the n + m (m is a natural number) frame;
A correction level for reducing the amplitude of the correction signal added to the video signal of the n + m-th frame when the absolute value of the amplitude of the high-frequency component extracted in the high-frequency component extraction step exceeds a reference value And an adaptive control step. The image quality improvement method according to claim 12 or 13 , further comprising a noise reduction step of removing noise, which is a high-frequency minute amplitude component, from the high-frequency component signal extracted in the high-frequency component extraction step.

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