JP3969414B2 - Video signal processing device - Google Patents

Description

  The present invention relates to a video signal processing apparatus of an image display apparatus that displays a color image.

  In recent years, with the widespread use of video disc players and personal computers, there is an increasing demand for image display devices that can make powerful presentations and advertisements on a large screen.

  The image display device is configured to display an image with good image quality by correcting the video signal input to the display device by the video signal processing device according to the electro-optical conversion characteristics of the device used for display. Yes.

  As a conventional video signal processing device of an image display device, for example, there is one described in Patent Document 1. FIG. 7 is a configuration diagram showing an example of the configuration of a video signal processing device of a conventional image display device.

  101 is an A / D conversion unit for converting an input analog video signal into a digital signal, 102 is a scaling processing unit for converting an image area of the input video signal into one suitable for the display area of the display device 106, 103 is a video image quality processing unit for adjusting the image quality of the video signal, 104 is a gamma correction unit for adjusting the input / output characteristics of the video signal to the characteristics of the display device 106, 105 is a display device driving unit, 106 is a display device, Reference numeral 107 denotes a CPU, and 108 denotes a timing generator that generates a clock signal for controlling the operation of each block.

  The operation of one example of the conventional video signal apparatus configured as described above will be described below.

  The input primary color analog video signals of red (R), green (G), and blue (B) are converted into digital video signals by the A / D converter 101. Since the input video signal has different numbers of pixels in the horizontal direction and vertical direction and the frequency of the synchronization signal depending on the signal source to be used, a certain pixel suitable for displaying the video on the display device 106 by the scaling processing unit 102. Number, converted to sync frequency. The video image quality processing unit 103 performs image quality adjustment such as black level, brightness, and edge enhancement of the video signal, and the gamma correction unit 104 changes the output characteristics of the video signal to the characteristics that match the electro-optical conversion characteristics of the display device 106. The corrected value is input to the display device driving unit 105. The display device driving unit 105 converts the video signal into a signal format suitable for driving the display device 106 and inputs the signal to the display device 106. The CPU 107 sends a control signal for controlling the operation state to each block to control the processing state of the video signal. The timing generator 108 generates a clock signal for synchronizing the operation of each block.

In a conventional video signal processing apparatus, in order to improve the color reproducibility of a displayed video, a method of improving color reproducibility by adjusting input / output characteristics of a video signal in the gamma correction unit 104, so-called gamma correction characteristics Is used.
JP 2001-16602 A (third page)

  Gamma correction is a linear light source with respect to the level of the input video signal by giving nonlinear input / output characteristics to the video signal input to the display device and canceling the electro-optical conversion characteristics of the imaging system and display device. This is performed in order to obtain a natural display image by obtaining output characteristics. In general, the input signal is corrected to the power of 2.2 to 2.4.

  This gamma correction can provide a linear light output characteristic with respect to the input signal. However, when the displayed image is viewed as it is, it may be felt that the brightness of the screen is insufficient. Therefore, in order to give a sense of brightness to the display image, a method of increasing the output by increasing the gain of the gamma correction characteristic from the low range to the intermediate range may be used.

  However, if the gain in the low to mid range of the gamma correction characteristic is increased, the output signal will saturate faster, so conversely, it is necessary to reduce the high range gain so that there is a gradation change up to the high range. There is. For this reason, in the intermediate color, there is a problem that the luminance difference of the primary color signals constituting the intermediate color becomes smaller than the original luminance difference, and the displayed color looks different.

  FIG. 8 is a conceptual diagram showing input / output characteristics of gamma correction for explaining this problem.

  In FIG. 8, a gamma correction curve GM1 indicated by a broken line indicates a characteristic obtained by raising the input signal level to the power of 2.2. On the other hand, a gamma correction curve GM2 indicated by a solid line in FIG. 8 is a curve obtained by doubling the gain of the gamma correction curve GM1 halfway and correcting so that the output is not saturated from there.

  As an example, consider a case where a cyan video signal having a blue input signal level b and a green input signal level g is input. When the gamma correction curve is GM1, since the output level of the blue signal is GM1 (b) and the output level of the green signal is GM1 (g), the difference between the two signal levels is GM1 (b) −GM1 (g). = S.

  On the other hand, when the gamma correction curve is GM2, since the output level of the blue signal is GM2 (b) and the output level of the green signal is GM2 (g), the signal level difference between them is GM2 (b) -GM2 ( g) = t, but since the slope of the gamma correction curve GM2 with respect to the input signal level is gentle, the level difference t between the blue signal and the green signal is the signal level when the gamma correction curve is GM1. It is smaller than the difference s. Thus, when the gamma correction curve GM2 is used, a cyan video signal having a blue input signal level b and a green input signal level g is greener than when the gamma correction curve GM1 is used by gamma correction. Since the component becomes stronger, the displayed color looks different.

  Whether the color of the displayed image is correctly reproduced with respect to the actual color is not obvious by just looking at the displayed image, but the human skin color yellow, sky and water cyan As for colors that are common to everyone and store the actual colors sensuously (hereinafter referred to as “memory colors”), if the color of the displayed image is different from the stored colors Will feel that the color reproduction is different.

  To cope with this problem, it is possible to make the green component smaller by making the gain of the green gamma correction curve smaller than the gain of the gamma correction curves of other colors. In the case of other colors as well, since the green component is uniformly reduced, there is another problem that the brightness of the display image is impaired.

  The present invention is for solving the above-described conventional problems, and in a video signal processing device of an image display device, a video signal capable of obtaining good color reproducibility while ensuring a feeling of brightness of a display image. An object is to provide a processing apparatus.

The invention according to claim 1 of the present invention provides
A video signal processing device of an image display device having at least one display element driven based on a color video signal,
A difference between the first primary color video signal and the second primary color video signal is detected from a video signal including at least two primary color video signals among the three primary color video signals of red, blue and green constituting the color video signal. First difference detecting means for
A first correction signal generating means for generating a first correction signal from the output signal and the second primary color video signals the Ru contained in the video signal from the first difference detection means,
Minimum value detecting means for detecting a minimum value of the first and second primary color signals;
Second difference detection means for detecting a difference between an output signal from the minimum value detection means and a third primary color video signal ;
Second correction signal generating means for generating a second correction signal from the output signal from the second difference detecting means;
Video signal level modulation signal creating means for creating a video signal level modulation signal from the first correction signal and the second correction signal;
Video signal level modulation means for modulating the first primary color video signal with the video signal level modulation signal;
The first correction signal is a difference obtained by subtracting the signal level of the first primary color video signal from the signal level of the second primary color video signal for each display pixel in the first difference detection unit. A function of the output and the signal level of the second primary color video signal,
As the differential output increases from 0, the correction amount of the correction signal is increased, the correction amount is decreased in a region where the differential output is equal to or higher than the first set level, and the differential output is equal to or higher than the second set level. controlled so as to zero again in the region, and is obtained by the features that you have been configured to control the correction amount by a signal level of the second primary color video signals, characteristic information of the video signal to detect, to improve color reproducibility by modulating the primary color video signal that is part of to the video signal, and the display image becomes overcorrected by controlling the extent to modulate the primary color video signal level Can be avoided .

The invention according to claim 2 is a video signal processing device of an image display device having at least one display element driven based on a color video signal,
A difference between the first primary color video signal and the second primary color video signal is detected from a video signal including at least two primary color video signals among the three primary color video signals of red, blue and green constituting the color video signal. First difference detecting means for
First correction signal generating means for generating a first correction signal from the output signal from the first difference detection means and the second primary color video signal included in the video signal;
Minimum value detecting means for detecting a minimum value of the first and second primary color video signals;
Second difference detection means for detecting a difference between an output signal from the minimum value detection means and a third primary color video signal;
Second correction signal generating means for generating a second correction signal from the output signal from the second difference detecting means;
Video signal level modulation signal creating means for creating a video signal level modulation signal from the first correction signal and the second correction signal;
Video signal level modulation means for modulating the first primary color video signal with the video signal level modulation signal;
The second correction signal is a difference output function obtained by subtracting the third video signal from the minimum value of the first and second primary color video signals for each display pixel in the second difference detection means. There,
When the difference output is smaller than a set level, the modulation amount of the video signal level modulation signal is controlled to be small,
By controlling the degree to which the primary color video signal level is modulated in the boundary region where the video signal is corrected, it is possible to prevent the display image from becoming abnormal.

  As described above, according to the video signal processing apparatus of the image display apparatus of the present invention, it is possible to obtain a good color reproducibility while ensuring the brightness of the display image in the image display apparatus.

  Embodiments of the present invention will be described below with reference to FIGS.

(Embodiment 1)
FIG. 1 is a block diagram showing an example of the configuration of a video signal processing apparatus of an image display apparatus according to an embodiment of the present invention. In FIG. 1, the same components as those of the conventional video signal processing apparatus shown in FIG. 7 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In FIG. 1, 101 is an A / D conversion unit, 102 is a scaling processing unit, 103 is a video image quality processing unit for adjusting the image quality of a video signal, and 104 matches the input / output characteristics of the video signal with the characteristics of the display device 106. A gamma correction unit 105, a display device driving unit 105, a display device 106, a CPU 107, a timing generation unit 108, and a video signal modulation unit 10 for modulating an intermediate color video signal.

  FIG. 2 is a block diagram showing a part of the configuration of the video signal modulator 10 in FIG. FIG. 2 is a block diagram of a video signal modulation circuit that modulates to a cyan color as an intermediate color as a part of the configuration of the video signal modulation unit 10 for the sake of explanation. This can be realized by applying the video signal modulation circuit for cyan shown in FIG.

  In FIG. 2, 11 is a first difference detection circuit for detecting the difference between the blue primary color video signal and the green primary color video signal, and 12 is a correction signal corresponding to the output signal of the first difference detection circuit 11 and the blue primary color video signal. A first correction signal generation circuit 13 for generating, a minimum value detection circuit 13 for detecting the minimum value of the blue primary color video signal and the green primary color video signal, and 14 for an output signal of the minimum value detection circuit 13 and the red primary color video signal A second difference detection circuit for detecting a difference, 15 is a second correction signal generation circuit for generating a second correction signal in accordance with an output signal of the second difference detection circuit 14, and 16 is a first correction. A multiplier for generating a video signal level modulation signal from the signal and the second correction signal, 17 an adder for modulating the level of the green primary color video signal by the modulation signal generated by the multiplier 16, and K1 a first 1 correction signal, K Is the second correction signal.

  The operation of the video signal processing apparatus configured as described above will be described with reference to FIGS.

  The primary color video signals of red, green, and blue that have undergone image quality adjustment such as black level, brightness, and edge enhancement in the video image quality processing unit 103 are input to the video signal modulation unit 10. The intermediate color is displayed centering on two primary color video signals among the three primary color video signals. In the case of the cyan color whose configuration is shown in FIG. 2, the primary color video signals of blue and green are the center.

  The first difference detection circuit 11 subtracts the level of the green primary color video signal from the level of the blue primary color video signal to obtain the difference between the two signals. The difference signal created by the first difference detection circuit 11 is input to the first correction signal generation circuit 12. The first correction signal generation circuit 12 generates a first correction signal K1 for modulating the video signal.

  FIG. 3 is a characteristic diagram showing an example of the first correction signal K1 generated by the first correction signal generation circuit 12. As shown in FIG. As shown in FIG. 3, the first correction signal K1 has a correction amount of 0 (region a) and a differential signal level from 0 while the differential signal level from the first differential detection circuit 11 is negative. As the value increases, the correction amount is increased (region b). When the differential signal level reaches the first set level, the correction amount is set to a constant value (region c), and the correction amount is decreased in the region of the second set level or higher (region c). Region d). The correction signal is such that the correction amount is set to 0 again (region e) in the region where the difference signal level is equal to or higher than the third set level.

  Here, the characteristic of the first correction signal K1 generated by the first correction signal generation circuit 12 is not limited to the characteristic shown in FIG. 3, and any characteristic can be used as long as the above-described conditions are satisfied. Such characteristics may be used.

  The reason why the first correction signal K1 generated by the first correction signal generation circuit is nonlinearly controlled as described above is that a color with a strong level is displayed in a region where the level difference between the blue primary color video signal and the green primary color video signal is large. This is based on the result that the color change due to the change in the output video signal level difference due to the gamma correction is not noticeable and the color change is noticeable at about 1/4 of the whole gradation. In the region where the level difference is small, the correction signal is decreased in order to maintain continuity with the color that is not modulated.

  The first correction signal generation circuit 12 performs the first correction as shown in FIG. 3 based on the difference output between the blue primary color video signal and the green primary color video signal detected by the first difference detection circuit 11 as described above. Although the signal K1 is generated, if the correction signal is generated based only on the differential output, the correction amount becomes constant regardless of the signal level, so that the correction in the low range is overcorrected. There is a possibility that. In this embodiment, in order to avoid this problem, the correction amount generated in the first correction signal generation circuit 12 is adjusted according to the level of the input blue primary color video signal, thereby reducing the correction amount in the low frequency range. It is controlled to become.

  Then, based on the first correction signal K1 generated by the first correction signal generation circuit 12, the green primary color video signal is modulated by the adder 17 to improve the color reproducibility of the cyan color. .

  In the above description, when improving the color reproducibility of the cyan color, it has been described that the green primary color video signal is modulated when the level of the blue primary color video signal is greater than the level of the green primary color video signal. The color of water and sky, which are memory colors, are strong blue, and image display devices generally have a high green luminance, so modulating the green primary color video signal improves color reproducibility. This is because it is effective.

  FIG. 4 is a characteristic diagram showing an example of the modulation state of the green primary color video signal by the video signal processing apparatus of the present embodiment. 4A shows output characteristics when no modulation is performed, and FIG. 4B shows output characteristics when modulation is performed. When modulation is not performed as shown in FIG. 4A, the output characteristic (G ′) of the green primary color video signal is linear with respect to the differential signal (BG), but FIG. When modulation is performed as shown, the green output signal is modulated so as to decrease as the difference signal (BG) increases from 0 (area b), and is constant when the first set level is exceeded. (Region c), and when the level of the differential signal (BG) further increases, the modulation amount decreases in the region above the second set level (region d), and the modulation amount becomes 0 again. (Region e) is modulated.

  As described above, in the video signal processing apparatus of this embodiment, in order to improve cyan color reproducibility, a difference signal between the blue primary color video signal and the green primary color video signal is detected, and a correction signal is generated therefrom. In this case, the green primary color video signal is modulated, but the display image becomes abnormal due to the modulation in the boundary region where the level of the red primary color video signal is close to the level of the other primary color video signal. Sometimes. Therefore, in the video signal processing apparatus according to the present embodiment, as a condition for modulating the green primary color video signal, the display image becomes abnormal by performing control so that the modulation is performed when the color of the pixel is sufficiently cyan. Is preventing.

  The minimum value detection circuit 13 detects the smaller value of the level of the input blue primary color video signal and green primary color video signal. The minimum value detected by the minimum value detection circuit 13 is input to the second difference detection circuit 14, and the difference between the two signals is obtained by subtracting the level of the red primary color video signal from the level of the input minimum value. Here, when the difference signal created by the second difference detection circuit 14 is small, it indicates that the level of the red primary color video signal is close to the level of the signal having the smaller level of the blue or green primary color video signal. Therefore, the color of the pixel is a color in which a white component is mixed. On the other hand, when the difference signal created by the second difference detection circuit 14 is large, it indicates that the level of the red primary color video signal is small, and therefore it can be determined that the color of the pixel is sufficiently cyan.

  The second correction signal generation circuit 15 corrects the correction signal generated by the first correction signal generation circuit 12 when the difference signal level is small according to the difference signal generated by the second difference detection circuit 14. A second correction signal K2 that reduces the amount is generated.

  FIG. 5 is a characteristic diagram showing an example of the second correction signal K2 generated by the second correction signal generation circuit 15. As shown in FIG. The characteristic of the second correction signal K2 generated by the second correction signal generation circuit 15 is not limited to the characteristic shown in FIG. 5, and any characteristic is used as long as the above conditions are satisfied. May be.

  Then, the multiplier 15 multiplies the first correction signal K1 generated by the first correction signal generation circuit 12 and the second correction signal K2 generated by the second correction signal generation circuit 15 by the first correction signal K1. The first correction signal K1 generated by the correction signal generation circuit 12 is further corrected to create a video signal level modulation signal, and when the color of the pixel is sufficiently cyan, the green primary color video signal is modulated. Is controlling.

  FIG. 6 is a relationship diagram in which the conditions of the video signal level modulation signal generated by the first correction signal K1 and the second correction signal K2 are summarized.

  As described above, according to the present embodiment, the green primary color video signal is generated by the first correction signal K1 generated by the first correction signal generation circuit 12 in accordance with the difference signal detected by the first difference detection circuit 11. Is modulated so that the level difference between the blue primary color video signal and the green primary color video signal is widened. In addition, the second correction signal generation circuit 15 generates the second correction signal K2 in accordance with the difference signal from the red primary color video signal detected by the second difference detection circuit 14 to generate the first correction signal. The first correction signal K1 generated in the circuit 12 is corrected. As described above, the modulation for the primary color video signal is dynamically controlled so that the modulation is performed when the color of the pixel is sufficiently cyan. Therefore, good color reproducibility can be obtained without impairing the feeling of brightness in the video signal processing apparatus of the image display apparatus.

  In the video signal processing apparatus according to the present invention, the circuit configuration for modulating the green primary color video signal in order to improve the color reproducibility of the cyan color which is a memory color has been described. However, the present invention is not limited to this. It is obvious that the primary color video signal may be modulated using the same method for other intermediate colors such as yellow and magenta.

  The video signal processing apparatus of the image display apparatus according to the present invention can improve the color reproducibility while ensuring the brightness of the display image of the image display apparatus. It can be applied to the use of the video signal processing apparatus.

The block diagram which showed an example of the structure of the video signal processing apparatus in embodiment of this invention The block diagram which showed the structure of the video signal modulation circuit with respect to the cyan color of the video signal modulation part in Embodiment 1 A characteristic diagram showing an example of the first correction signal K1 generated by the first correction signal generation circuit 12 The characteristic view which showed an example of the modulation | alteration state of the green primary color video signal in the video signal modulation part in Embodiment 1 A characteristic diagram showing an example of the second correction signal K2 generated by the second correction signal generation circuit 15 Relationship diagram summarizing video signal level modulation signal conditions The block diagram which showed an example of the structure of the conventional video signal processing apparatus Conceptual diagram showing input / output characteristics of gamma correction

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Video signal modulation | alteration part 11 1st difference detection circuit 12 1st correction signal generation circuit 13 Minimum value detection circuit 14 2nd difference detection circuit 15 2nd correction signal generation circuit 16 Multiplier 17 Adder

Claims (2)

A video signal processing device of an image display device having at least one display element driven based on a color video signal,
A difference between the first primary color video signal and the second primary color video signal is detected from a video signal including at least two primary color video signals among the three primary color video signals of red, blue and green constituting the color video signal. First difference detecting means for
A first correction signal generating means for generating a first correction signal from the output signal and the second primary color video signals the Ru contained in the video signal from the first difference detection means,
Minimum value detecting means for detecting a minimum value of the first and second primary color video signals;
Second difference detection means for detecting a difference between an output signal from the minimum value detection means and a third primary color video signal ;
Second correction signal generating means for generating a second correction signal from the output signal from the second difference detecting means;
Video signal level modulation signal creating means for creating a video signal level modulation signal from the first correction signal and the second correction signal;
Video signal level modulation means for modulating the first primary color video signal with the video signal level modulation signal;
The first correction signal is a difference obtained by subtracting the signal level of the first primary color video signal from the signal level of the second primary color video signal for each display pixel in the first difference detection unit. A function of the output and the signal level of the second primary color video signal,
As the differential output increases from 0, the correction amount of the correction signal is increased, the correction amount is decreased in a region where the differential output is equal to or higher than the first set level, and the differential output is equal to or higher than the second set level. controlled so as to zero again in the region, and a video signal processing apparatus characterized that you have been configured to control the correction amount by a signal level of the second primary color video signals. A video signal processing device of an image display device having at least one display element driven based on a color video signal,
A difference between the first primary color video signal and the second primary color video signal is detected from a video signal including at least two primary color video signals among the three primary color video signals of red, blue and green constituting the color video signal. First difference detecting means for
First correction signal generating means for generating a first correction signal from the output signal from the first difference detection means and the second primary color video signal included in the video signal;
Minimum value detecting means for detecting a minimum value of the first and second primary color video signals;
Second difference detection means for detecting a difference between an output signal from the minimum value detection means and a third primary color video signal;
Second correction signal generating means for generating a second correction signal from the output signal from the second difference detecting means;
Video signal level modulation signal creating means for creating a video signal level modulation signal from the first correction signal and the second correction signal;
Video signal level modulation means for modulating the first primary color video signal with the video signal level modulation signal;
The second correction signal is obtained by subtracting the third video signal from the minimum value of the first and second primary color video signals for each display pixel in the second difference detection means. A differential output function,
A video signal processing apparatus for controlling the video signal level modulation signal to have a small modulation amount when a differential output is smaller than a set level.

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