CN101261821B - Gamma curve compensation method, gamma curve compensation circuit and display system - Google Patents

Abstract

The present invention provides a gamma curve compensation method, a gamma curve compensation circuit and a display system, which are suitable for inserting multiple grayscale images in the display process of the display system to adjust the display performance of the display system, and the grayscale brightness of each grayscale image is formed by selecting one of multiple grayscale values. The gamma curve compensation method includes: providing multiple corresponding lookup tables for different grayscale values; when selecting a specific grayscale value among these grayscale values to form one of these grayscale images, selecting a specific lookup table corresponding to the specific grayscale value from the lookup table, and using this specific lookup table as the basis for gamma curve compensation, so as to keep the gamma curve of the display system unchanged during the display process. The present invention also provides a gamma curve compensation circuit and a display system for executing the above method.

Description

Gamma curve compensation method, gamma curve compensation circuit and display system

technical field

The invention relates to an image display technology, and in particular to a pulse-driven display system and its gamma curve compensation method and circuit.

Background technique

At present, one of the main ways to solve the motion blur (Motion Blur) phenomenon of the dynamic image of the liquid crystal display system is the impulse-type driving (Impulse-type Driving), which is the fixed black insertion (BlackInsertion) technology. However, in the impulsive driving method, the fixed black insertion (Black Insertion) technology will cause the screen brightness to attenuate (Luminance Decay) and cause obvious problems of flicker (Flicker). In addition, the response time of liquid crystal is not linear when pulling up from zero grayscale. When the initial grayscale is a lower grayscale, the pull-up time is much longer than that of other higher grayscales, which is not conducive to improving Smear (ghost) phenomenon.

In order to improve the above-mentioned problems of brightness attenuation, flicker, etc. and the transition speed of liquid crystal to reduce the phenomenon of smearing, a dynamic gray insertion technology (Dynamic Gray Insertion) is proposed, which determines the gray level to be inserted according to different pictures value.

Although, in the process of dynamically inserting gray scale, different gamma (Gamma) output will be obtained by inserting different gray scale values, resulting in uneven brightness and dark parts of the picture, and even the same color will appear in different areas. to get a different color output.

Contents of the invention

The purpose of the present invention is to provide a gamma curve compensation method so that the gamma curve of the display system remains unchanged during the display process.

Another object of the present invention is to provide a gamma curve compensation circuit to keep the gamma curve of the display system unchanged during the display process.

Another object of the present invention is to provide a display system whose gamma curve does not change during the display process.

Other purposes and advantages of the present invention can be further understood from the technical features disclosed in the present invention.

In order to achieve one or part or all of the above objectives or other objectives, an embodiment of the present invention proposes a gamma curve compensation method, which is suitable for a display system to insert multiple grayscale images during the display process to adjust Display the display performance of the system. The gray-scale brightness of each gray-scale image is formed by selecting one of a plurality of gray-scale values, and the gray-scale brightness of these gray-scale images are not completely identical to each other. This gamma curve compensation method includes: providing corresponding multiple look-up tables for different gray scale values; when selecting a specific gray scale value in these gray scale values to form one of these gray scale images, from the lookup table Selecting a specific lookup table corresponding to a specific grayscale value; and using the specific lookup table as a basis for gamma curve compensation, so as to keep the gamma curve of the display system unchanged during the display process.

Another embodiment of the present invention provides a gamma curve compensation circuit suitable for a display system. The gamma curve compensation circuit includes: an image generation circuit, an insertion gray scale determination circuit, a multiplexer and a search and compensation circuit. The image generation circuit generates corresponding original output image signals according to the input image signals received by the display system. The insertion grayscale determination circuit determines the grayscale brightness of the grayscale image to be inserted according to the input image signal, and outputs the grayscale image. The multiplexer is electrically coupled to the image generating circuit and inserted into the grayscale determination circuit, and is used to select one of the original output image and the grayscale image as the original display signal output by the multiplexer. The lookup and compensation circuit is electrically coupled to the multiplexer to receive the original display signal, and the lookup and compensation circuit provides a plurality of different lookup tables, and selects among the lookup tables corresponding to the received original display signal A specific look-up table for the gray-scale brightness of the gray-scale image, and perform gamma curve compensation on the original display signal according to this specific look-up table.

Yet another embodiment of the present invention provides a display system, including: a power supply, an image receiving end, the above-mentioned gamma curve compensation circuit, and a display screen. The power supply provides power for the display system to operate; the image receiving end is used to receive the input image signal; the display screen is used to display the original display signal after the gamma curve compensation is performed by the search and compensation circuit of the gamma curve compensation circuit.

Embodiments of the present invention provide corresponding multiple lookup tables for different grayscale values, and one of the multiple grayscale images to be inserted during the display process is selected by selecting a specific grayscale value among these grayscale values When the brightness of the grayscale is the same, select a specific lookup table corresponding to a specific grayscale value from the lookup table, and use this specific lookup table as the basis for gamma curve compensation to adjust to a consistent normalized gamma (Normalized Gamma) value (such as Gamma2.4). Therefore, the gamma curve of the display system can be kept unchanged during the display process, thereby improving the display performance of the display system.

In order to make the above and other objects, features and advantages of the present invention more comprehensible, preferred embodiments will be described in detail below together with the accompanying drawings.

Description of drawings

FIG. 1 is a circuit block diagram of a display system according to an embodiment of the invention.

FIG. 2 is a circuit block diagram of an insertion grayscale determination circuit according to an embodiment of the present invention.

FIG. 3 is a circuit block diagram of a display system according to another embodiment of the present invention.

FIG. 4 is a graph of brightness curves for different interpolated grayscale values according to an embodiment of the present invention.

FIG. 5 shows that according to an embodiment of the present invention, when the frame is of low grayscale, a grayscale insertion period is entered in one frame, and the light source is turned off.

Wherein, the reference signs are explained as follows:

10: Display system

11: Power

13: Image receiving end

15: Gamma curve compensation circuit

150: Insert grayscale determination circuit

1502: Color space conversion module

1504: Analysis module

1506: Insert gray scale limit module

1508: grayscale generation module

152: Image generation circuit

154: Multiplexer

156: Search and Compensation Circuit

158: Backlight module control circuit

17: Display screen

19: Backlight module

L15, L10, L5: gray scale value

Td, Tb: display the charging time of the signal

Detailed ways

Please refer to FIG. 1 , which is a circuit block diagram of a display system 10 according to an embodiment of the present invention. In this embodiment, the display system 10 includes a power supply 11 , an image receiving terminal 13 , a gamma curve compensation circuit 15 and a display screen 17 . The power supply 11 provides power for the display system 10 to operate, the image receiving terminal 13 is used for receiving input image signals, and the display screen 17 is used for displaying images.

The gamma curve compensation circuit 15 includes an interpolation grayscale determination circuit 150 , an image generation circuit 152 , a multiplexer 154 and a search and compensation circuit 156 . Wherein, the insertion grayscale determination circuit 150 determines the grayscale brightness of the grayscale image to be inserted according to the input image signal, and outputs the grayscale image after determining the grayscale brightness. The image generating circuit 152 generates a corresponding original output image signal according to the input image signal received by the image receiving end 13 . The multiplexer 154 is electrically coupled to the insertion grayscale determination circuit 150 and the image generation circuit 152, so that the grayscale image output from the insertion grayscale determination circuit 150 and the original output image signal generated by the image generation circuit 152 are included. Choose one as the original display signal output by the multiplexer 154 . The search and compensation circuit 156 is electrically coupled to the multiplexer 154 to receive the original display signal. It should be noted that the lookup and compensation circuit 156 provides a plurality of different lookup tables, and selects a specific lookup table corresponding to the grayscale brightness of the grayscale image in the received original display signal among these lookup tables, and according to This specific look-up table is used to perform gamma curve compensation on the original display signal, so as to keep the gamma curve of the display system 10 unchanged during the display process. The original display signal is sent to the display screen 17 for display after the gamma curve compensation is performed by the search and compensation circuit 156 .

Please also refer to FIG. 2 , which is a circuit block diagram of the insertion grayscale determination circuit 150 according to an embodiment of the present invention. The inserted grayscale determination circuit 150 includes a color space conversion module 1502 , an analysis module 1504 , an inserted grayscale limitation module 1506 and a grayscale generation module 1508 . The color space conversion module 1502 converts the input image signal received by the image receiving end 13 into color space distribution information. The analysis module 1504 is electrically coupled to the color space conversion module 1502 to receive color space distribution information. The analysis module 1504 analyzes the distribution of the color space distribution information in the color space, and outputs a corresponding analysis signal. The inserted gray scale limiting module 1506 stores gray scale limiting parameters, while the gray scale generating module 1508 is electrically coupled to the analysis module 1504 and the inserted gray scale limiting module 1506, so that the analysis signal output by the analyzing module 1504 and the inserted The gray-scale limiting parameters stored in the gray-scale limiting module 1506 determine the gray-scale brightness of the gray-scale image to be inserted and output the gray-scale image.

Specifically, the grayscale image to be inserted above is based on division (Division), and the same division inserts the same grayscale value; each division can be a line, a segment (Segment), a frame (Frame) or a number frames. The analysis module 1504 can adopt the histogram analysis method or other known analysis methods such as the minimum gray-scale insertion (Minimum Gray Insertion) method and the threshold (Threshold) method to determine the pre-inserted gray-scale value of each segment, and its output The analysis signal of can represent this pre-interpolated gray scale value. Since the grayscale value of an image can usually be divided into 255 levels, that is, grayscale L0-L255; the inserted grayscale limiting module 1506 of this embodiment can limit the range of inserted grayscale values to a specific range (for example, L0-L30 ), and limit the change range of the inserted gray scale for each adjacent segment (that is, the level difference between the gray levels to be inserted between two adjacent segments is not greater than a preset value, such as 5 or 10) or do a smoothing process. The grayscale generation module 1508 can obtain the final grayscale value of the grayscale image to be inserted (that is, grayscale brightness), and output this grayscale image.

Referring to FIG. 3 , the display system 10 in this embodiment may further include a backlight module 19 to provide a light source (not shown) to illuminate the display screen 17 . In this case, the display system 10 may be a liquid crystal display device. Further, the display system 10 may include a backlight module control circuit 158, which is electrically coupled to the multiplexer 154 and controls the grayscale brightness of the grayscale image in the original display signal output by the multiplexer 154. The backlight module driving signal used to drive the backlight module 19 is used to adjust the brightness of the light source in the display system 10, so that the brightness of the picture in the display system 10 during the display process will be consistent after different inserted gray scales and the corresponding look-up table. As a result, the screen brightness of the display system 10 does not change. Wherein, the backlight module control circuit 158 can be integrated into the gamma curve compensation circuit 150 (as shown in FIG. 3 ), or can be a circuit structure independent of the gamma curve compensation circuit 150 .

A gamma curve compensation method of the above-mentioned display system 10 will be described below. The display system 10 inserts a plurality of gray-scale images during the display process to adjust the display performance of the display system 10. The gray-scale brightness of each gray-scale image is determined by how many One of the grayscale values is selected, and the grayscale brightness of these grayscale images is not exactly the same as that of each other. The gamma curve compensation method may include the following steps:

(1) A plurality of corresponding lookup tables are provided for different gray scale values; wherein, these lookup tables can be provided by the lookup and compensation circuit 156 of the gamma curve compensation circuit 150 .

(2) When selecting a specific gray-scale value in these gray-scale values to form the gray-scale brightness of one of these gray-scale images, select the corresponding gray-scale value from these look-up tables by the lookup and compensation circuit 156 a specific lookup table; and

(3) Use this specific lookup table as the basis for gamma curve compensation, so as to keep the gamma curve of the display system 10 unchanged during the display process, such as adjusting to a consistent standardized gamma value (such as Gamma 2.4).

Please refer to FIG. 4, although the gamma curves after inserting different gray scales all conform to a standardized gamma value (such as Gamma 2.4), the actual brightness of the inserted multiple gray scale images may still have differences; therefore, in this embodiment The gamma curve compensation method can also include a brightness correction step (4): adjusting the brightness of the light source in the display system 10, so that the brightness of the screen of the display system 10 remains unchanged during the display process. Specifically, the brightness correction can be achieved by adjusting the backlight module driving signal used to drive the light source of the display system 10 through the backlight module control circuit 158, such as a pulse width modulation (Pulse Width Modulation, PWM) signal; The grayscale value corresponds to a smaller pulse width (PulseWidth), and the brightness curve of the grayscale image with a higher inserted grayscale (for example, grayscale L15) is maintained by using an appropriate pulse width modulation signal (that is, without sacrificing the maximum luminance without increasing the input power), and then map the luminance curve of the gray-scale image with a lower inserted gray-scale (for example, gray-scale L10 and L5) upward using a larger pulse width (as indicated by the dotted arrow in Figure 4 ), so that the luminance curve and the gamma curve will get consistent results after matching the corresponding lookup table with different interpolation gray levels.

In addition, during the display process of inserting multiple grayscale images, as the brightness of the highest grayscale increases, the brightness of the lowest grayscale also increases, which makes the image contrast of the display system 10 poor during the display process. Therefore, as shown in FIG. 5 , the gamma curve compensation method of this embodiment may further include a contrast enhancement step (5): turning off the light source during a part of the display process, so as to suppress the brightness increase of the low-gray-scale picture. Specifically, when the picture is of low grayscale, the grayscale insertion period is entered in one frame, and the light source can be turned off (B/L OFF) through the backlight module driving signal provided by the backlight module control circuit 158, so that the filter can be filtered. Increases contrast by removing unnecessary brightness from low-grayscale images. B/L ON in Figure 5 means that the light source is on, while Td and Tb are the charging time of the display signal, and Td+Tb can be equal to a maximum horizontal scanning line time of one frame (1H Time).

To sum up, the embodiment of the present invention provides a plurality of corresponding lookup tables for different gray scale values, and selects a specific gray scale value among these gray scale values to form a plurality of gray scale values to be inserted during the display process. When adjusting the grayscale brightness of one of the images, select a specific lookup table corresponding to a specific grayscale value from the lookup table and use this specific lookup table as the basis for gamma curve compensation to adjust to a consistent standardized gamma value . Therefore, the gamma curve of the display system can be kept unchanged during the display process, thereby improving the display performance of the display system. Further, by controlling the light source to correct the brightness of the picture and suppressing the increase of the brightness of the low-gray-scale picture to increase the overall contrast, the display performance of the display system can be made better.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any skilled person in this technical field should be able to make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, this The scope of protection of the invention should be determined by the scope defined by the appended claims.

Claims (13)

1. A gamma curve compensation method, suitable for a display system, the display system inserts a plurality of grayscale images in a display process to adjust the display performance of the display system, the grayscale of each grayscale image Brightness is obtained by selecting one of several grayscale values. The gamma curve compensation method includes: providing a plurality of corresponding lookup tables for different gray scale values; When selecting a specific gray-scale value among the gray-scale values to form one of the gray-scale images, selecting a specific look-up table corresponding to the specific gray-scale value from the look-up tables; and The specific look-up table is used as the basis for gamma curve compensation to keep the gamma curve of the display system unchanged during the display process. 2. The gamma curve compensation method according to claim 1 , further comprising: adjusting the brightness of a light source in the display system, so that the brightness of the display system does not change during the display process. 3. The gamma curve compensation method as claimed in claim 2, wherein adjusting the brightness of the light source in the display system is achieved by adjusting a pulse width modulation signal used to drive the light source. 4. The gamma curve compensation method as claimed in claim 2, further comprising: turning off the light source during a part of the display process. 5. The gamma curve compensation method as claimed in claim 1 , further comprising: turning off a light source in the display system during a part of the display process. 6. A gamma curve compensation circuit suitable for use in a display system, characterized in that it comprises: an image generation circuit that generates a corresponding original output image signal according to an input image signal received by the display system; An insertion grayscale determination circuit, which determines the grayscale brightness of a grayscale image to be inserted according to the input image signal, and outputs the grayscale image; a multiplexer, electrically coupled to the image generation circuit and the inserted grayscale determination circuit, for selecting one of the original output image and the grayscale image as the output of the multiplexer an original display signal of ; and A look-up and compensation circuit, electrically coupled to the multiplexer to receive the original display signal, the look-up and compensation circuit provides a plurality of different look-up tables, and selects in the look-up tables corresponding to the received A specific look-up table of the gray-scale brightness of the gray-scale image in the original display signal, and performing gamma curve compensation on the original display signal according to the specific look-up table. 7. The gamma curve compensation circuit as claimed in claim 6, further comprising: a backlight module control circuit electrically coupled to the multiplexer, and according to the original display output by the multiplexer The grayscale brightness of the grayscale image in the signal controls a backlight module driving signal used to drive a backlight module in the display system. 8. The gamma curve compensation circuit as claimed in claim 6, wherein the insertion gray scale determination circuit comprises: A color space conversion module, which converts the input image signal received by the display system into a color space distribution information; An analysis module, electrically coupled to the color space conversion module to receive the color space distribution information, the analysis module analyzes the distribution of the color space distribution information in the color space to output a corresponding analysis signal; a grayscale limiting module is inserted, and a grayscale limiting parameter is stored; and a grayscale generation module, electrically coupled to the analysis module and the inserted grayscale limiting module, the grayscale generating module cooperates with the grayscale stored in the inserted grayscale limiting module according to the analysis signal output by the analyzing module The grayscale brightness of the grayscale image to be inserted is determined according to the scale limit parameter, and the grayscale image is output. 9. The gamma curve compensation circuit as claimed in claim 6, wherein the display system comprises a liquid crystal display device. 10. A display system comprising: a power supply, providing power for the display system to operate; an image receiving end, used for receiving an input image signal; A gamma curve compensation circuit, comprising: An image generating circuit, which generates a corresponding original output image signal according to an input image signal received by the display system; An insertion grayscale determination circuit, which determines the grayscale brightness of a grayscale image to be inserted according to the input image signal, and outputs the grayscale image; a multiplexer, electrically coupled to the image generation circuit and the inserted grayscale determination circuit, for selecting one of the original output image and the grayscale image as the output of the multiplexer an original display signal of ; and A look-up and compensation circuit, electrically coupled to the multiplexer to receive the original display signal, the look-up and compensation circuit provides a plurality of different look-up tables, and selects in the look-up tables corresponding to the received a specific look-up table of the gray-scale brightness of the gray-scale image in the original display signal, and perform gamma curve compensation on the original display signal according to the specific look-up table; and A display screen is used to display the gamma curve compensation result of the original display signal through the search and compensation circuit. 11. The display system as claimed in claim 10, further comprising: a backlight module providing a light source to illuminate the display screen. 12. The display system according to claim 11 , further comprising: a backlight module control circuit, electrically coupled to the multiplexer, and according to the original display signal output by the multiplexer The grayscale brightness of the grayscale image controls a backlight module driving signal used to drive the backlight module. 13. The display system according to claim 10, wherein the inserted gray scale determination circuit comprises: A color space conversion module, which converts the input image signal received by the display system into a color space distribution information; An analysis module, electrically coupled to the color space conversion module to receive the color space distribution information, the analysis module analyzes the distribution of the color space distribution information in the color space to output a corresponding analysis signal; a grayscale limiting module is inserted, and a grayscale limiting parameter is stored; and a grayscale generation module, electrically coupled to the analysis module and the inserted grayscale limiting module, the grayscale generating module cooperates with the grayscale stored in the inserted grayscale limiting module according to the analysis signal output by the analyzing module The grayscale brightness of the grayscale image to be inserted is determined according to the scale limit parameter, and the grayscale image is output.

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