TWI404046B - Gamma curve compensation method, gamma curve compensation circuit and display system - Google Patents

Abstract

A gamma curve compensation method is adapted to a display system. A plurality of gray-scale images are inserted during a display process of the display system to adjust the display thereof. A gray-scale luminance of each of the gray-scale images is corresponding to one of gray levels and the gray-scale luminance of the gray-scale images are not completely the same. The gamma compensation method includes: providing a plurality of look up tables respectively corresponding to the gray levels; searching a particular look up table corresponding to a particular gray level from the look up tables when choosing the particular gray level from the gray levels to define the gray-scale luminance of one of the gray-scale images; and implementing a gamma compensation based upon the particular look up table to keep the gamma curve unchanged during the display process. The present invention also provides a gamma curve compensation circuit and a display system can perform the above-mentioned gamma compensation method.

Description

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

The present invention relates to an image display technology, and more particularly to a pulsed drive display system and a gamma curve compensation method and circuit therefor.

At present, one of the main ways to solve the motion blur phenomenon of the motion picture of the liquid crystal display system is Impulse-type Driving, which is a B1ack Insertion technology. However, in the pulsed drive mode, the Black Insertion technique causes the screen brightness to decay (Luminance Decay) and causes significant problems with flicker. In addition, the reaction time of the liquid crystal is nonlinear when pulled up by the zero gray scale. When the initial gray scale is lower gray scale, the pulling time is much higher than other higher gray scales, which is not conducive to improvement. Ghost phenomenon.

In order to improve the aforementioned brightness attenuation, flickering and the like and the transition speed of the liquid crystal to reduce the smear phenomenon, a Dynamic Gray Insertion technique is proposed, which determines the gray scale to be inserted according to different pictures. value.

However, in the process of dynamically inserting gray scales, there will be different gamma output when inserting different gray scale values, resulting in a bright and dark unevenness of the picture, even the same color will be in different areas. Get different color output.

It is an object of the present invention to provide a gamma curve compensation method to keep the gamma curve of the display system unchanged during display.

It is still another object of the present invention to provide a gamma curve compensation circuit to keep the gamma curve of the display system unchanged during display.

It is still another object of the present invention to provide a display system that is in the process of being displayed The gamma curve does not change.

Other objects and advantages of the present invention will become apparent from the technical features disclosed herein.

In order to achieve one or a part or all of the above or other purposes, an embodiment of the present invention provides a gamma curve compensation method, which is suitable for use in a display system to insert a plurality of grayscale images in a display process to adjust the display. The display performance of the system. The grayscale brightness of each grayscale image is formed by selecting one of a plurality of grayscale values, and the grayscale luminances of the grayscale images are not completely identical to each other. The gamma curve compensation method includes: providing corresponding plurality of lookup tables for different grayscale values; and selecting one of the grayscale values to form one of the grayscale images from the lookup table Selecting a particular lookup table that corresponds to a particular grayscale value; and using this particular lookup table as a basis for gamma curve compensation to keep the gamma curve of the display system unchanged during display.

Another embodiment of the present invention provides a gamma curve compensation circuit suitable for use in a display system. The gamma curve compensation circuit comprises: an image generation circuit, an insertion gray level decision circuit, a multiplexer, and a lookup and compensation circuit. The image generating circuit generates a corresponding original output image signal according to the input image signal received by the display system. The gray scale determining circuit is configured to determine the gray scale brightness of the gray scale image to be inserted according to the input image signal, and output the gray scale image. The multiplexer is electrically coupled to the image generation circuit and the insertion gray-scale determination circuit for selecting one of the original output image and the gray-scale 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 different lookup tables, and selects gray scales corresponding to the received original display signals in the lookup tables. A specific lookup table of grayscale brightness of the image, and gamma curve compensation of the original display signal according to the specific lookup table.

Another embodiment of the present invention provides a display system including: a power source, a video receiving end, the gamma curve compensation circuit, and a display screen. The power supply provides power for the display system to operate; the image receiving end is configured to receive the input image signal; and the display screen is used to display the result obtained by the gamma curve compensation of the original display signal through the lookup and compensation circuit of the gamma curve compensation circuit.

The embodiment of the present invention provides a plurality of lookup tables corresponding to different grayscale values, and selects one of the grayscale values to display one of a plurality of grayscale images to be inserted during display. For grayscale brightness, 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 uniform normalized gamma (Normalized Gamma) Value (eg Gamma2.4). Therefore, the gamma curve of the display system can be made unchanged during the display process, thereby improving the display performance of the display system.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

Please refer to FIG. 1, which is a circuit block diagram of a display system 10 in accordance with an embodiment of the present invention. In the present embodiment, the display system 10 includes a power source 11, a video receiving terminal 13, a gamma curve compensation circuit 15, and a display screen 17. The power source 11 provides power for the display system 10 to operate, the image receiving end 13 is for receiving an input image signal, and the display screen 17 is for displaying an image.

The gamma curve compensation circuit 15 includes an insertion gray scale decision circuit 150, an image generation circuit 152, a multiplexer 154, and a lookup and compensation circuit 156. The grayscale decision 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 receives the input image signal received by the image receiving end 13 And the corresponding original output image signal is generated. The multiplexer 154 is electrically coupled to the grayscale determination circuit 150 and the image generation circuit 152, thereby selecting the grayscale image output from the grayscale determination circuit 150 and the original output image signal generated by the image generation circuit 152. First, as the original display signal output by the multiplexer 154. The lookup 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 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 the lookup tables, and according to This particular lookup table performs gamma curve compensation on the original display signal to keep the gamma curve of display system 10 unchanged during display. The result of the gamma curve compensation by the original display signal via the lookup and compensation circuit 156 is sent to the display screen 17 for display.

Please refer to FIG. 2, which is a circuit block diagram of the gray scale decision circuit 150 according to an embodiment of the invention. The insertion grayscale decision circuit 150 includes a color space conversion module 1502, an analysis module 1504, an insertion grayscale restriction 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 data. The analysis module 1504 is electrically coupled to the color space conversion module 1502 to receive color space distribution data. The analysis module 1504 analyzes the distribution of the color space distribution data in the color space, and outputs a corresponding analysis signal. The grayscale generation module 1506 is configured to store the grayscale restriction module, and the grayscale generation module 1508 is electrically coupled to the analysis module 1504 and the grayscale restriction module 1506, thereby outputting according to the analysis module 1504. The gray signal intensity of the grayscale image to be inserted is determined and the grayscale image is outputted by analyzing the signal and matching the grayscale limiting parameter stored in the grayscale limiting module 1506.

Specifically, the grayscale image to be inserted is a single division. Bit, the same segmentation inserts the same grayscale value; each segmentation can be a line, a segment, a frame, or several frames. The analysis module 1504 can determine the pre-inserted gray scale value of each segment by using a histogram analysis method or other well-known analysis methods such as a Minimum Gray Insertion method and a Threshold method. The output analysis signal can represent this pre-inserted grayscale value. The grayscale value of the image can be generally divided into 256 levels, that is, the gray scale L0~L255; the insertion grayscale limiting module 1506 of this embodiment can limit the range of the inserted grayscale value to a specific range (for example, L0~ L30), and each adjacent segmentation limits the range of change of the inserted grayscale (that is, the level difference of the grayscales to be inserted between two adjacent segments is not greater than a preset value, such as 5 or 10) or the adjacent segmentation Do the smoothing process. The grayscale generation module 1508 can obtain the final grayscale value of the grayscale image to be inserted according to the pre-inserted grayscale value determined by the analysis module 1504 and the grayscale restriction parameter stored in the grayscale restriction module 1506. That is, gray scale 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, display system 10 can be a liquid crystal display device. Further, the display system 10 can include a backlight module control circuit 158 electrically coupled to the multiplexer 154 and controlled for driving according to the gray scale brightness of the grayscale image in the original display signal output by the multiplexer 154. The backlight module of the backlight module 19 drives the signal to adjust the brightness of the light source in the display system 10, so that the screen brightness of the display system 10 during the display process is consistent with different corresponding grayscales and corresponding lookup tables. That is, the brightness of the screen of the display system 10 is unchanged. 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 aforementioned display system 10 will be described below. The display system 10 inserts a plurality of grayscale images during the display process to adjust the display performance of the display system 10. The grayscale brightness of each grayscale image is formed by selecting a plurality of grayscale values, and the grayscale images are The grayscale brightness is not exactly the same for each other. The gamma curve compensation method can include the following steps: (1) providing a plurality of corresponding lookup tables for different of these grayscale values; wherein the lookup tables can be provided by the lookup and compensation circuit 156 of the gamma curve compensation circuit 150.

(2) When one of the grayscale values is selected to be the grayscale luminance of one of the grayscale images, the lookup and compensation circuit 156 selects from the lookup tables to correspond to the specific grayscale value. a specific lookup table; and (3) use this particular lookup table as a basis for gamma curve compensation to keep the gamma curve of display system 10 unchanged during the display, such as adjusting to a uniform normalized gamma value (eg Gamma 2.4).

Referring to FIG. 4, although the gamma curves after inserting different gray scales all conform to a normalized gamma value (such as Gamma 2.4), the actual brightness of the inserted gray scale images may still be different; therefore, this embodiment The gamma curve compensation method may further include a brightness correction step (4) of adjusting the brightness of the light source in the display system 10 to cause the picture brightness of the display system 10 to be unchanged during the display. Specifically, the correction of the brightness can be achieved by the backlight module control circuit 158 adjusting the backlight module driving signal used to drive the light source of the display system 10, such as a Pulse Width Modulation (PWM) signal; The higher insertion grayscale value corresponds to a smaller pulse width (Pulse Width), and the brightness curve of the grayscale image of the higher grayscale (for example, grayscale L15) is maintained by the appropriate pulse width modulation signal (also That is, without sacrificing the maximum brightness and without increasing the input power, the luminance curves of the grayscale images of the lower grayscales (for example, grayscales L10 and L5) are mapped upwards with a larger pulse width (see Figure 4). Dotted arrow As indicated, the brightness curve and the gamma curve will have consistent results after matching the corresponding lookup tables with different gray scales.

In addition, in the display process of inserting a plurality of grayscale images as described above, as the brightness of the highest grayscale increases, the minimum grayscale luminance also increases, thereby causing poor display contrast of the display system 10 during display. Therefore, as shown in FIG. 5, the gamma curve compensation method of the present embodiment may further include a contrast enhancement step (5) of turning off the light source during a partial period of the display process to suppress the brightness increase of the low grayscale picture. Specifically, when the picture belongs to a low gray level, the gray level insertion period is entered in one frame, and the backlight module driving signal provided by the backlight module control circuit 158 can be turned off (B/L OFF), such that To increase the contrast since the unnecessary brightness of low grayscale images can be filtered out. The B/L ON in FIG. 5 means that the light source is in the lighting state, and the first signal time Td and the second signal time Tb are the charging time of the display signal, and the Td+Tb maximum can be equal to one frame horizontal scanning line time ( 1 Line Time). The first signal time Td is the time for notifying the signal of the data, and the second time time Tb is the time for writing the black data signal.

In summary, the embodiment of the present invention provides a plurality of corresponding lookup tables for different grayscale values, and selects a plurality of grayscale values to display a plurality of grayscale values. When the grayscale brightness of one of the order images is selected, a specific lookup table corresponding to the specific grayscale value is selected from the lookup table and the specific lookup table is used as the basis for the gamma curve compensation to adjust to a uniform normalized gamma value. . Therefore, the gamma curve of the display system can be made unchanged during the display process, thereby improving the display performance of the display system. Further, the display performance of the display system can be better by controlling the light source to correct the brightness of the screen and suppressing the brightness increase of the low gray scale picture to increase the overall contrast.

Although the invention has been disclosed above in the preferred embodiments, it is not intended to be limiting In the present invention, it is to be understood that the scope of the invention is defined by the scope of the appended claims. In addition, any of the objects or advantages or features of the present invention are not required to be achieved by any embodiment or application of the invention. In addition, the abstract sections and headings are only used to assist in the search of patent documents and are not intended to limit the scope of the invention.

10‧‧‧Display system

11‧‧‧Power supply

13‧‧‧Image receiving end

15‧‧‧Gamma Curve Compensation Circuit

150‧‧‧Insert gray scale decision circuit

1502‧‧‧Color Space Conversion Module

1504‧‧‧Analysis module

1506‧‧‧Insert grayscale 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 values

Td, Tb‧‧‧ shows the charging time of the signal

1 is a circuit block diagram of a display system in accordance with an embodiment of the present invention.

2 is a block diagram of a circuit for inserting a gray scale decision circuit in accordance with an embodiment of the present invention.

3 is a circuit block diagram of a display system in accordance with another embodiment of the present invention.

4 is a graph of luminance for different interpolated grayscale values, in accordance with an embodiment of the present invention.

FIG. 5 illustrates a grayscale insertion period in one frame and a light source off when a picture belongs to a low gray level according to an embodiment of the invention.

10‧‧‧Display system

11‧‧‧Power supply

13‧‧‧Image receiving end

15‧‧‧Gamma Curve Compensation Circuit

150‧‧‧Insert gray scale decision circuit

152‧‧‧Image generation circuit

154‧‧‧Multiplexer

156‧‧‧Search and compensation circuit

17‧‧‧ display screen

Claims (13)

A gamma curve compensation method is applicable to a display system. The display system inserts a plurality of grayscale images in a display process to adjust display performance of the display system, and each of the grayscale image systems is correspondingly inserted into multiple segments. Previously, the grayscale brightness of each of the grayscale images is formed by one of a plurality of grayscale values, wherein each of the segments is a line and a segment on the input image of the display system. a frame (frame) or N frames, and N is an integer greater than 1, and the gamma curve compensation method includes: providing a plurality of corresponding lookup tables for different grayscale values; selecting the grays When one of the grayscale images is one of the grayscale images, a specific lookup table corresponding to the specific grayscale value is selected from the lookup tables; and the specific lookup table is used as the gamma Based on the basis of the curve compensation, the grayscale brightness of each of the grayscale images is determined to make the gamma curve of the display system unchanged during the display process. The gamma curve compensation method of claim 1, further comprising: adjusting brightness of a light source in the display system to make the brightness of the display system unchanged during the display process. The gamma curve compensation method of claim 2, wherein adjusting the brightness of the light source in the display system is achieved by adjusting a pulse width modulation signal used when driving the light source. The gamma curve compensation method as described in claim 2, further comprising: turning off the light source during a part of the display process. The gamma curve compensation method of claim 1, further comprising: turning off one of the light sources in the display system during a part of the display process. A gamma curve compensation circuit, which is suitable for use in a display system, comprising: an image generation circuit for generating a corresponding original output image signal according to an input image signal received by the display system; Determining a circuit, according to the input image signal, determining a grayscale brightness of a grayscale image to be inserted, and outputting the grayscale image before each segmentation, wherein the segmentation is performed on the input image a line, a segment, a frame, or N frames, and N is an integer greater than one; a multiplexer electrically coupled to the image generation circuit and the insertion gray-scale decision circuit, An original display signal outputted from the original output image and the grayscale image is outputted by the multiplexer; and a lookup and compensation circuit electrically coupled to the multiplexer to receive the original Displaying a signal, the lookup and compensation circuit providing a plurality of different lookup tables, and selecting, in the lookup tables, a grayscale brightness corresponding to the grayscale image of the grayscale image received in the original display signal A specific lookup table is used to determine the grayscale brightness of each of the grayscale images, and the original display signal is subjected to gamma curve compensation according to the specific lookup table. The gamma curve compensation circuit of claim 6, 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 for driving a backlight module in the display system. The gamma curve compensation circuit according to claim 6, wherein the insertion gray level decision circuit comprises: a color space conversion module, the input image signal received by the display system is converted into a color space distribution data; an analysis module is electrically coupled to the color space conversion module to receive the color space distribution data, The analysis module analyzes the distribution of the color space distribution data in the color space to output a corresponding analysis signal; inserts a gray scale limit module to store a gray scale limit parameter; and a gray scale generation module, the electricity The grayscale generation module is coupled to the analysis grayscale limit module, and the grayscale generation module stores the grayscale limit stored by the grayscale restriction module according to the analysis signal output by the analysis module. The grayscale brightness of the grayscale image to be inserted is determined by the parameter, and the grayscale image is output. The gamma curve compensation circuit of claim 6, wherein the display system comprises a liquid crystal display device. A display system includes: a power source for providing power for the display system to operate; an image receiving end for receiving an input image signal; and a gamma curve compensation circuit comprising: an image generating circuit, according to the display system Receiving an input image signal to generate a corresponding original output image signal; an insertion gray level determining circuit, determining the grayscale brightness of a grayscale image to be inserted according to the input image signal, and outputting the grayscale image The grayscale image is inserted in units of a segmentation before each segmentation, and the segmentation is a line, a segment, a frame, or a N frame on the input image. And N is an integer greater than 1; a multiplexer is electrically coupled to the image generation circuit and the insertion gray-scale determination circuit for selecting one of the original output image and the gray-scale image An original display signal output by the tool; a lookup and compensation circuit electrically coupled to the multiplexer to receive the original display signal, the lookup and compensation circuit providing a plurality of different lookup tables, and selecting, in the lookup tables, the original corresponding to the received Displaying a specific lookup table of the grayscale brightness of the grayscale image in the signal to determine the grayscale brightness of each of the grayscale images, and performing gamma curve compensation on the original display signal according to the specific lookup table; A display screen is used to display the result of the gamma curve compensation of the original display signal through the search and compensation circuit. The display system of claim 10, further comprising: a backlight module, providing a light source to illuminate the display screen. The display system of claim 11, further comprising: a backlight module control circuit electrically coupled to the multiplexer, and according to the gray in the original display signal output by the multiplexer The grayscale brightness of the image is controlled to drive a backlight module driving signal of the backlight module. The display system of claim 10, wherein the insertion gray scale determining circuit comprises: a color space conversion module, converting the input image signal received by the display system into a color space distribution data; The module is electrically coupled to the color space conversion module to receive the color space distribution data, and the analysis module analyzes the distribution of the color space distribution data in the color space to output a corresponding analysis signal; a grayscale limiting module stores a grayscale limiting parameter; and a grayscale generating module electrically coupled to the analyzing module and the inserted grayscale limiting module, the grayscale generating module according to the analyzing module The outputted analysis signal determines the grayscale brightness of the grayscale image to be inserted according to the grayscale limiting parameter stored in the grayscale limiting module, and outputs the grayscale image.