CN1936676A - Adaptive Backlight Modulation System and Modulation Method - Google Patents

Abstract

An adaptive backlight modulation system and a modulation method thereof comprise a brightness matching distribution device, a brightness compensation module, an image frame adjusting device, a backlight control device and a backlight module. The luminance pair distribution device generates a luminance pair distribution value for each frame. The brightness compensation module calculates a dark state proportion value and a brightness index value of the image frame according to the brightness matching distribution value to generate a brightness compensation signal. The image frame adjusting device adjusts the brightness of the image frame according to the brightness compensation signal. The backlight control device updates the brightness index value according to the brightness index value and the brightness matching distribution value to generate a backlight control signal corresponding to the current image frame. The backlight control device adjusts the backlight of the backlight module according to the backlight control signal, so that the brightness of the image frame is adaptively matched with the light-emitting curve of the backlight module.

Description

Adaptive Backlight Modulation System and Modulation Method

technical field

The present invention relates to a modulation system and a modulation method thereof, in particular to an adaptive backlight modulation system and a modulation method thereof.

Background technique

Liquid crystal displays are generally divided into transmissive liquid crystal displays, reflective liquid crystal displays, and semi-transmissive/semi-reflective liquid crystal displays. The transmissive liquid crystal displays are provided with a backlight module (Backlight Module). The light sources used in the backlight module can be roughly divided into cold cathode fluorescent lamps (Cold Cathode Fluorescent Lamp, CCFL), hot cathode fluorescent lamps, light emitting diodes or other electroluminescent devices (Electro Luminescent Device, EL device), the current The mainstream is the cold cathode fluorescent lamp (CCFL).

The light leakage effect is more obvious when the liquid crystal display is in a dark state (that is, the gray scale value is lower). Moreover, with the ever-increasing demands of the size of the liquid crystal display panel and its application in the TV system, the viewing angle of the display is required to be much higher than that of the previous computer system application, so the phenomenon of light leakage in the dark state of each viewing angle is becoming more and more strict requirements. In addition, in order to improve the viewing quality of the panel by improving the dynamic contrast, it is necessary to dynamically adjust the backlight in real time. However, the traditional backlight adjustment often only considers factors such as the ambient light source and ignores the above-mentioned problems. Therefore, the traditional adjustment method is likely to cause flickering phenomena on the LCD, and uneven light emission on the LCD screen makes the image quality of the LCD screen unstable.

Therefore, it is necessary to develop a backlight modulation system to improve the image quality of the display.

Contents of the invention

An object of the present invention is to provide a backlight modulation system and a modulation method thereof, which can adaptively adjust the brightness of the image frame by using the brightness compensation signal and adjust the brightness of the light source of the backlight module by using the backlight control signal, so that the image frame can be displayed on the liquid crystal display device. The image presented on the LCD maintains consistency and saves power, thereby reducing the temperature of the liquid crystal display device and prolonging its service life.

Another object of the present invention is to provide a backlight modulation system and a modulation method thereof, which can calculate the dark state ratio value of the pixels of the image frame, improve the contrast of the image frame, and improve the picture quality of the liquid crystal display device.

According to the above purpose, the present invention proposes a backlight modulation system and a modulation method thereof. The backlight modulation system mainly includes a brightness matching distribution device, a brightness compensation module, an image frame adjustment device, a backlight control device and a backlight module. The brightness pair distribution device receives a plurality of image frames to generate a brightness pair distribution value corresponding to each image frame, wherein each image frame has a plurality of pixels. The brightness compensation module is connected to the brightness pair distribution device, and the brightness compensation module calculates the dark state ratio value of all pixels in the current image frame according to the brightness pair distribution value of the current image frame, and uses the dark state ratio value to calculate the current image The brightness index value of the frame is used to generate a brightness compensation signal corresponding to the current image frame according to the dark state ratio value and the brightness index value. The image frame adjustment device is connected to the brightness compensation module, and adjusts the brightness of the pixels in the current image frame according to the brightness compensation signal from the brightness compensation module.

The backlight control device is respectively connected to the brightness pair distribution device and the brightness compensation module, and the backlight control device updates the brightness index of the current image frame according to the brightness index value of the previous image frame and the brightness pair distribution value of the current image frame value to generate the backlight control signal corresponding to the current image frame. The backlight modules are respectively connected to the backlight control device, and the backlight control device adjusts the backlight brightness of the backlight module according to the generated backlight control signal, so that the brightness of the current image frame is adaptively matched with the light emission curve of the backlight module.

According to the above, the parameters of the brightness compensation signal can be obtained by processing the brightness pair distribution curve of the image frame image and the brightness index value of the previous backlight brightness emission curve through the brightness compensation module. This parameter is used to correct the image data of the image frame to compensate The image consistency of the backlight module during the adjustment process and the need to improve the image contrast. At the same time, the parameters of the backlight control signal can be obtained by processing the brightness pair distribution curve of the image frame image and the brightness index value of the previous backlight brightness emission curve through the backlight control device. This parameter is used to generate a new brightness index value to adjust the backlight module. Therefore, the present invention utilizes these two parameters to adaptively adjust the image frame image and project the backlight on the display device displaying the image frame image, so as to maintain the consistency of the image presented on the liquid crystal display device, improve the picture quality, and save power. Lower the operating temperature of the LCD monitor.

The backlight modulation method of the present invention first receives a plurality of image frames; then generates a brightness pair distribution value corresponding to each image frame, wherein each image frame has a plurality of pixels; and then calculates according to the brightness pair distribution value of the current image frame The dark ratio value of the pixels in the current image frame, and using the dark ratio value to calculate the brightness index value of the current image frame, so as to generate a brightness compensation signal corresponding to the current image frame according to the dark ratio value and the brightness index value.

After that, adjust the brightness of these pixels in the current image frame according to the brightness compensation signal from the brightness compensation module; then update the brightness of the current image frame according to the brightness index value of the previous image frame and the brightness pair distribution value of the current image frame brightness index value to generate a backlight control signal corresponding to the current image frame; finally adjust the backlight of the backlight module according to the generated backlight control signal, so that the brightness of the current image frame and the luminous curve of the backlight module adaptively match each other.

The backlight modulation system and its modulation method of the present invention use the brightness compensation signal to adaptively adjust the brightness of the image frame and the backlight control signal to adjust the brightness of the light source of the backlight module, so that the images presented by the image frame on the liquid crystal display device maintain consistency , and save power, thereby reducing the temperature of the liquid crystal display device and prolonging its service life.

Description of drawings

FIG. 1 shows a block diagram of a backlight modulation system according to an embodiment of the present invention.

FIG. 2A shows a schematic diagram of brightness pair distribution values of an image frame according to an embodiment of the present invention.

FIG. 2B shows a schematic diagram of a dark state compensation curve according to an embodiment of the present invention.

FIG. 2C shows a schematic diagram of the gamma controller in FIG. 1 using the dark compensation curve in FIG. 2B to generate a new dark compensation curve according to the present invention.

FIG. 3 shows a detailed block diagram of the image frame detection module in the backlight control device of FIG. 1 according to the present invention.

FIG. 4A shows that the image frame detection module gradually adjusts the current brightness index value to the target brightness index value according to the difference ratio between the current brightness index value and the target brightness index value according to an embodiment of the present invention. schematic diagram.

FIG. 4B shows a schematic diagram of the image frame detection module gradually adjusting the current brightness index value to the target brightness index value at a fixed ratio according to an embodiment of the present invention.

FIG. 5 shows a schematic diagram of an image frame that may be different in generating a target brightness and determining a current brightness in accordance with an embodiment of the present invention.

FIG. 6A shows a schematic diagram of a lookup table according to an embodiment of the present invention.

FIG. 6B shows a schematic diagram of waveform output in a frequency conversion form according to an embodiment of the present invention.

FIG. 7 shows a flow chart of the backlight modulation method according to the present invention.

Detailed ways

The invention provides a backlight modulation system and a modulation method thereof. The brightness of the image frame is adaptively adjusted by using the brightness compensation signal and the brightness of the light source of the backlight module is adjusted by the backlight control signal, so that the image presented by the image frame on the display device is maintained. Consistency, and save the power consumed by the display device, thereby reducing its operating temperature and prolonging the service life of the display device. In addition, the backlight modulation system calculates the dark ratio value of the pixels of the image frame to increase the contrast of the image frame to improve the picture quality of the display device. The backlight modulation system and modulation method thereof of the present invention are suitable for backlight modules of liquid crystal displays (LCDs) and liquid crystal televisions, or for display devices with backlight modules.

FIG. 1 shows a block diagram of a backlight modulation system according to an embodiment of the present invention. The backlight modulation system 100 is suitable for a liquid crystal display device, and mainly includes a brightness matching distribution device 102 , a brightness compensation module 104 , an image frame adjustment device 106 , a backlight control device 108 and a backlight module 110 . The intensity-pair distribution device 102 receives a plurality of image frames for generating an intensity-pair distribution (Intensity-pair Distribution) value corresponding to each image frame, wherein each image frame has a plurality of pixels. The brightness compensation module 104 is connected to the brightness pair distribution device 102. The brightness compensation module 104 calculates the dark state ratio value of all pixels in the current image frame according to the brightness pair distribution value of the current image frame, and uses the dark state ratio value to calculate the current image frame. The brightness index value of the frame is used to generate a brightness compensation signal corresponding to the current image frame by using the dark state ratio value and the brightness index value 118b. The image frame adjustment device 106 is connected to the brightness compensation module 104, and adjusts the brightness of all pixels in the current image frame according to the brightness compensation signal from the brightness compensation module. In a preferred embodiment of the present invention, the data of the brightness compensation signal is stored in the brightness compensation storage device 112, and the brightness compensation data can be expressed as a brightness compensation curve.

The backlight control device 108 is respectively connected to the brightness pair distribution device 102 and the brightness compensation module 104. The backlight control device 108 updates the brightness of the current image frame according to the brightness index value 118a of the previous image frame and the brightness pair distribution value of the current image frame. The index value 118b is used to generate the backlight control signal corresponding to the current image frame. The backlight modules 110 are respectively connected to the backlight control device 108, and the backlight control device 108 adjusts the backlight brightness of the backlight module 100 according to the generated backlight control signal, so that the brightness of the current image frame is adaptively matched with the light emission curve of the backlight module 100.

According to the above, the backlight modulation system 100 of the present invention can process the brightness compensation module 104 to obtain the parameters of the brightness compensation signal by processing the brightness pair distribution curve of the image frame image and the brightness index value 118b of the previous backlight brightness emission curve. The image data of the image frame is corrected to compensate for the image consistency of the backlight module 100 during the adjustment process and to improve the image contrast. At the same time, the parameters of the backlight control signal can be obtained by processing the brightness pair distribution curve of the image frame image and the brightness index value 118b of the previous backlight brightness emission curve through the backlight control device 108, and this parameter is used to generate a new brightness index value 118a to Adjust the backlight module. Therefore, the present invention uses these two parameters to adaptively adjust the image frame image and project the backlight on the display device 114 displaying the image frame image, so as to maintain the consistency of the image presented on the display device 114, improve the picture quality, and save power To reduce the operating temperature of the display device 114 .

FIG. 2A shows a schematic diagram of a brightness pair distribution curve of an image frame according to an embodiment of the present invention. The coordinates on the horizontal axis of the brightness pair distribution curve represent the grayscale value, and the vertical axis represents the number of pixels corresponding to the grayscale value. The dark state ratio value (Black Ratio, BR) in the brightness compensation module means that in each image frame, the gray scale value is lower than the number of pixels (m) of a reference value (n) and the total number of pixels of the image frame The ratio (m/o) of the number (o) is multiplied by the gray scale resolution (expressed as k, the value of which can be 255 or any positive integer, for example).

Further, the brightness index value of the present invention is the sum of the maximum pixel gray scale value multiplied by the first weighted value and the dark state ratio value multiplied by the second weighted value in each image frame. That is to say, when calculating the brightness pair distribution value of each image frame to obtain the gray scale value k of the brightest point, define the brightness index value (Brightness Index, BI) as BI=q×k+(1-q)×BR, where q is an adjustable first weighted value, for example between 0 and 1 or any positive integer, and (1-q) is a second weighted value. The brightness index value is used to represent the proportional relationship between dark and bright pixels of each image frame, which is used as a parameter for correcting image data and adjusting backlight.

FIG. 2B shows a schematic diagram of a dark state compensation curve according to an embodiment of the present invention. In one embodiment, in order to compensate for the change of the gray scale value caused by the reduction of the brightness of the backlight, the present invention uses a method of correcting the brightness curve of the image frame to compensate, as shown in FIG. 2B. The horizontal axis coordinate of the brightness curve 200 represents the gray scale value before the change, and the vertical axis represents the gray scale value after the change corresponding to the gray scale value before the change, that is, the dark state ratio value BR is multiplied by the constant R (arbitrary positive integer ) is defined as R_BR, which is used as the lifting point of the gray scale value, so that the n of the gray scale value on the horizontal axis is converted into (n+R_BR) of the gray scale value on the vertical axis, and the conversion point is linearly extended with 0 and 255 points (or any positive integer) are connected to generate a new dark state compensation curve. It should be noted that the dotted line 202 represents the original dark state compensation curve 202 before adjusting the backlight.

FIG. 2C shows a schematic diagram of the gamma controller 116 in FIG. 1 using the dark compensation curve in FIG. 2B to generate a new dark compensation curve according to the present invention. In FIG. 1, the backlight modulation system 100 includes a gamma controller 116 connected to the brightness compensation module 104. The gamma controller 116 receives the brightness compensation signal from the brightness compensation module 104, and then multiplies the brightness compensation signal by The first adjustment parameter is summed by multiplying the gamma signal 204 by the second adjustment parameter to generate a new dark state compensation curve 206 as a brightness compensation signal of the brightness compensation module 104 . That is, the original gamma curve is multiplied by (1-p), and then the dark state compensation curve is multiplied by p, wherein the adjustable parameter p is between 0 and 1, or any positive integer.

Referring to FIG. 1 and FIG. 3, FIG. 3 shows a detailed block diagram of the image frame detection module 108a in the backlight control device of FIG. 1 according to the present invention. The image frame detection module 108a is connected to the brightness pairing distribution device 102, uses the pairing distribution difference between the brightness pairing distribution value of the current image frame and the brightness pairing distribution value of the previous image frame, and divides the pairing distribution difference by the The brightness pair distribution value of the current image frame is used to detect the image frame difference between the current image frame and the previous image frame, and judge whether to directly change the brightness index value 118a of the current image frame to Target brightness index value. In a preferred embodiment of the present invention, the brightness index value 118a of the current image frame and the brightness index value 118b of the previous image frame are stored in the index data storage device 118 .

Specifically, the background change detection mechanism of the image frame is based on the brightness pair distribution diagram of the front/back two image frames, assuming that the brightness pair distribution trend diagrams of the nth page and the n+1th page are respectively:

Hn(0), Hn(1), ..., Hn(a);

Hn+1(0), Hn+1(1), . . . , Hn+1(a); wherein a is a positive integer, such as the above-mentioned gray scale value resolution k.

$\mathrm{D.}\_S=\underset{i=0}{\overset{a}{\mathrm{\Σ}}}|h_{\mathrm{no}}\left(i\right)-h_{\mathrm{no}+1}\left(i\right)|$ Expressed as the sum D_S of pairwise distribution differences.

$S=\underset{i=0}{\overset{a}{\mathrm{\Σ}}}{h}_{\mathrm{no}}\left(i\right)$ Expressed as the sum S of the overall brightness pair distribution values.

According to the above, the image frame difference hist_diff_ratio=D_S/S, when the image frame difference is greater than a threshold value (Threshold Value), the brightness index value of the current image frame is directly changed to the target brightness index value, for example, when the scene changes rapidly, Often accompanied by significant flickering, the backlight can be adjusted to the final brightness once at this moment. On the contrary, in a smooth scene, the brightness index value is changed gradually to avoid the flickering phenomenon detected by the human eye.

Continuing to refer to FIG. 1, the backlight modulation system 100 of the present invention also includes a contrast comparison module 108b, which is connected to the brightness pair distribution device 102, and uses the brightness pair distribution values of the current image frame and the previous image frame to calculate the current image respectively. frame and the contrast ratio of the previous image frame, and compare the contrast ratios of the two image frames to determine whether to adjust the backlight according to the comparison result. Since the human eye is more sensitive to "contrast", it cannot detect the approximate difference in absolute brightness. Therefore, when the contrast of the image frame is consistent, the original brightness will be retained without any change to avoid flickering caused by overall brightness changes. Specifically, contrast is defined as the highest brightness minus the lowest brightness for each image frame: CR=max(Y)min(Y). The difference between CR_n and CR_n+1 of the image frames on the current and subsequent pages (image frame N and image frame N+1) is smaller than the threshold CR_th, indicating that the contrast of the two pages is almost the same. At this time, do not adjust the backlight, otherwise adjust the backlight .

In an embodiment of the present invention, when the brightness index value of the current image frame is different from the target brightness index value, the image frame detection module gradually adjusts the current brightness index value to the target brightness according to the difference ratio of the image frame difference index value. The range of each change is defined as BR_INC, which can be based on (a) screen difference ratio; (b) brightness difference ratio; and (c) fixed ratio, examples are as follows:

(a) Screen gap ratio:

Here the frame difference is defined as the image frame difference hist_diff_ratio. When the screen difference is K, the upper limit of each change is a fixed ratio value c, which means that c×K is used as the interval of each change. If the current luminance index is BR_curr and the target luminance index is BR_dest, then the next luminance index is BR_curr+c×K until BR_dest.

For example, the current brightness is 100, the target brightness is 127, and the screen difference is 20. If the fixed ratio value c is 0.5, after the first change, the brightness index is 100+20×0.5=110; the second change: 110+20×0.5=120; third change: 120+20×0.5=130>127, then output 127.

If the target brightness is lower than the current brightness, the brightness will gradually decrease. For example, the current brightness is 100, the target brightness is 87, the screen difference is 20, and the ratio value is 0.5, then the first change: 100-20×0.5=90; Secondary change: 90-20×0.5=80<87, then output 87.

(b) Brightness difference ratio:

As shown in Figure 4A, it shows that according to an embodiment of the present invention, the image frame detection module gradually adjusts the current brightness index value to the target brightness index according to the difference ratio between the current brightness index value and the target brightness index value Value diagram. When the brightness index value of the current image frame is different from the target brightness index value, the image frame detection module gradually adjusts the current brightness index value to the target brightness index value according to the difference ratio between the current brightness index value and the target brightness index value .

When the difference between the current brightness and the target brightness is larger, the jump range is larger each time, and the range of change is (Br_dest Br_curr) multiplied by a fixed ratio value c, for example: c=0.5, the current brightness=100, the target brightness is 150, the first The first change: 100+0.5×(150-100)=125; the second change: 125+0.5×(150-125)=138; the third change: 138+0.5×(150-138)=144.

(c) Fixed ratio:

As shown in FIG. 4B , it shows a schematic diagram of the image frame detection module gradually adjusting the current brightness index value to the target brightness index value at a fixed ratio according to an embodiment of the present invention. When the brightness index value of the current image frame is different from the target brightness index value, the image frame detection module gradually adjusts the current brightness index value to the target brightness index value in a fixed ratio.

Regardless of the image difference, the fixed adjustment ratio is k until the final brightness BR_dest is reached. For example, current brightness BR_curr=100, target brightness BR_dest=117, adjustment ratio c=10, first change: 100+10=110; second change: 110+10=120>117, then output 117.

FIG. 5 shows a schematic diagram of an image frame that may be different in generating a target brightness and determining a current brightness in accordance with an embodiment of the present invention. After generating the target brightness and determining the current brightness, the image frame can be in different pages. After the target brightness switching function is determined to be F_dest and the current brightness switching function F_curr, the final output brightness index is determined every F_dest page, and the current brightness Change to a new brightness index after every F_chg (representing the change process of the brightness index of the page with the time axis), which means that when the scene changes drastically, the current brightness can be directly converted to the target brightness index, otherwise, the brightness will be gradually changed index.

FIG. 6A shows a schematic diagram of a lookup table according to an embodiment of the present invention. The backlight modulation system of the present invention also includes a look-up table, which is queried by using the calculated brightness index value to generate low-level parameters and high-level parameters to adjust the pulse width modulation signal to adjust the backlight module brightness of the light source. Specifically, the present invention queries a look-up table (Look-up Table, LUT) with a luminance index, and obtains two independent coefficients Pa and Pb through the aforementioned calculated luminance index, and the control signal generator 600 combines the two coefficients accordingly A modulating signal with variable width is output, wherein Pa represents the time length of the signal level being high, and Pb represents the time length of the signal level being low. The backlight module 110 can adjust the brightness of the light source according to the combination ratio of Pa and Pb. In a preferred embodiment, the control signal generator 600 can be, for example, a control circuit composed of a counter (Counter) and a comparator (Comparator) components.

In another embodiment, the luminance index value can be a value that changes with time, and at the same time indicates that the combination of Pa/Pb can change with time, thereby forming a waveform output in the form of frequency conversion, so as to achieve the purpose of dynamic backlight adjustment, as shown in Section 6B As shown in the figure, it shows a schematic diagram of waveform output in a frequency conversion form according to an embodiment of the present invention.

FIG. 7 shows a flowchart of a backlight modulation method according to an embodiment of the present invention. Firstly, in step S700, a plurality of image frames are received; then in step S702, a brightness pair distribution value corresponding to each image frame is generated, wherein each image frame has a plurality of pixels; and then in step S704, according to the brightness pair distribution value of the current image frame, Calculate the dark ratio value of the pixels in the current image frame, and use the dark ratio value to calculate the brightness index value of the current image frame, so as to generate a brightness compensation signal corresponding to the current image frame by using the dark ratio value and the brightness index value.

Then in step S706, adjust the brightness of the pixels in the current image frame according to the brightness compensation signal from the brightness compensation module; then in step S708, update the brightness index value of the previous image frame and the brightness pair distribution value of the current image frame The brightness index value of the current image frame to generate a backlight control signal corresponding to the current image frame; finally in step S710 adjust the backlight brightness of the backlight module according to the generated backlight control signal, so that the brightness of the current image frame is consistent with the luminescence curve of the backlight module Adaptively match each other.

The backlight modulation system and its modulation method of the present invention use the brightness compensation signal to adaptively adjust the brightness of the image frame and the backlight control signal to adjust the brightness of the light source of the backlight module, so that the images presented by the image frame on the liquid crystal display device maintain consistency , and save power, thereby reducing the temperature of the liquid crystal display device and prolonging its service life. And the backlight modulation system calculates the dark ratio value of the pixels of the image frame, so as to enhance the contrast of the image frame and improve the image quality of the liquid crystal display device.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore The scope of protection of the present invention should be defined by the scope of the appended patent application.

Claims (22)

1. An adaptive backlight modulation system, suitable for liquid crystal display devices, the backlight modulation system at least includes: A luminance pair distribution device receives a plurality of image frames to generate a luminance pair distribution value corresponding to each of the image frames, wherein each of the image frames has a plurality of pixels; A brightness compensation module, connected to the brightness pair distribution device, the brightness compensation module calculates the dark state ratio value of the pixel in the current image frame according to the brightness pair distribution value of the current image frame, and uses the dark state ratio value to calculate the brightness index value of the current image frame, so as to generate a brightness compensation signal corresponding to the current image frame according to the dark state ratio value and the brightness index value; An image frame adjustment device, connected to the brightness compensation module, to adjust the brightness of the pixel in the current image frame according to the brightness compensation signal from the brightness compensation module; a backlight control device, respectively connected to the brightness pair distribution device and the brightness compensation module, the backlight control device updates the current image frame according to the brightness index value of the previous image frame and the brightness pair distribution value of the current image frame a brightness index value to generate a backlight control signal corresponding to the current image frame; and A backlight module is respectively connected to the backlight control device, and the backlight control device adjusts the backlight source of the backlight module according to the generated backlight control signal, so that the brightness of the current image frame is adaptively matched with the luminescence curve of the backlight module. 2. The backlight modulation system according to claim 1, wherein the dark state ratio value of the brightness compensation module is the number of pixels whose gray scale value is lower than a reference value in each image frame and the total number of pixels in the image frame The ratio of the two numbers. 3. The backlight modulation system according to claim 2, wherein the brightness index value of the brightness compensation module is multiplied by the maximum pixel gray scale value in each image frame multiplied by the first weighted value and the dark state ratio value The sum of the two with the second weighted value. 4. The backlight modulation system according to claim 1, further comprising a gamma controller, connected to the brightness compensation module, receiving a brightness compensation signal from the brightness compensation module, and the gamma controller takes the brightness compensation signal multiplied by the first adjustment parameter and summed by multiplying the gamma signal by the second adjustment parameter to adjust the brightness compensation signal from the brightness compensation module. 5. The backlight modulation system according to claim 1, further comprising an image frame detection module connected to the brightness pair distribution device, using the brightness pair distribution value of the current image frame and the brightness pair distribution of the previous image frame The pairing distribution difference between the two values, and divide the pairing distribution difference by the brightness pairing distribution value of the current image frame to detect the image frame difference between the current image frame and the previous image frame, according to the The image frame difference determines whether to change the brightness index value of the current image frame to a target brightness index value. 6. The backlight modulation system according to claim 5, when the brightness index value of the current image frame is different from the target brightness index value, the image frame detection module converts the current brightness to The index value is gradually adjusted to the target brightness index value. 7. The backlight modulation system according to claim 5, when the brightness index value of the current image frame is different from the target brightness index value, the image frame detection module uses the difference between the current brightness index value and the target brightness index value The current luminance index value is gradually adjusted to the target luminance index value according to the gap ratio between them. 8. The backlight modulation system according to claim 5, when the brightness index value of the current image frame is different from the target brightness index value, the image frame detection module gradually adjusts the current brightness index value to The target brightness index value. 9. The backlight modulation system according to claim 1, further comprising a contrast comparison module connected to the brightness pair distribution device, and using the brightness pair distribution values of the current image frame and the previous image frame to calculate the current image respectively. frame and the contrast ratio of the previous image frame, and compare the contrast ratios of the two image frames to determine whether to adjust the backlight according to the comparison result. 10. The backlight modulation system as claimed in claim 1, wherein generating target brightness and determining current brightness are different image frames. 11. The backlight modulation system as claimed in claim 1, further comprising a look-up table, which is queried by using the calculated brightness index value to generate a low-level parameter and a high-level parameter to adjust the pulse width modulation signal to adjust the brightness of the light source of the backlight module. 12. A modulation method for an adaptive backlight system, the modulation method comprising the following steps: Receive plural image frames; generating luminance pair distribution values corresponding to each of the image frames, wherein each of the image frames has a plurality of pixels; Calculate the dark state ratio value of these pixels in the current image frame according to the brightness pair distribution value of the current image frame, and use the dark state ratio value to calculate the brightness index value of the current image frame, so as to combine the dark state ratio value and The brightness index value generates a brightness compensation signal corresponding to the current image frame; adjusting the brightness of the pixels in the current image frame according to the brightness compensation signal from the brightness compensation module; updating the brightness index value of the current image frame according to the brightness index value of the previous image frame and the brightness pair distribution value of the current image frame, so as to generate a backlight control signal corresponding to the current image frame; and The backlight of the backlight module is adjusted according to the backlight control signal, so that the brightness of the current image frame matches the luminous curve of the backlight module. 13. The modulation method according to claim 12, wherein the dark state ratio value is the ratio of the number of pixels whose gray scale value is lower than a reference value in each image frame and the total number of pixels in the image frame ratio. 14. The modulation method according to claim 13, wherein the brightness index value is equal to the maximum pixel gray scale value multiplied by the first weighted value and the dark state ratio value multiplied by the second weighted value in each image frame. sum of those. 15. The modulation method according to claim 12 , further comprising multiplying the brightness compensation signal by a first adjustment parameter and multiplying the gamma signal by a second adjustment parameter to make a sum to adjust the brightness from the brightness compensation module compensation signal. 16. The modulation method according to claim 12, further comprising using the pairing distribution difference between the brightness pairing distribution value of the current image frame and the brightness pairing distribution value of the previous image frame, and the pairing distribution difference value divided by the brightness pairing distribution value of the current image frame to detect the image frame difference between the current image frame and the previous image frame, and judge whether to use the brightness index value of the current image frame according to the image frame difference Change to target brightness index value. 17. The modulation method according to claim 16, when the luminance index value of the current image frame is different from the target luminance index value, the image frame detection module uses the difference ratio of the image frame difference to index the current luminance index The value is gradually adjusted to the target brightness index value. 18. The modulation method according to claim 16, when the brightness index value of the current image frame is different from the target brightness index value, the image frame detection module uses the distance between the current brightness index value and the target brightness index value Gradually adjust the current brightness index value to the target brightness index value. 19. The modulation method according to claim 16, when the brightness index value of the current image frame is different from the target brightness index value, the image frame detection module gradually adjusts the current brightness index value to the target brightness index value in a fixed ratio. Target brightness index value. 20. The modulation method according to claim 12, further comprising calculating the contrast ratios of the current image frame and the previous image frame by using the brightness pair distribution values of the current image frame and the previous image frame, and comparing the The contrast ratio of the two image frames is used to determine whether to adjust the backlight according to the comparison result. 21. The modulation method as claimed in claim 12, wherein generating target brightness and determining current brightness are different image frames. 22. The modulation method as claimed in claim 12, further comprising querying a look-up table using the calculated brightness index value to generate a low-level parameter and a high-level parameter to adjust the pulse width modulation signal to adjust the backlight The brightness of the module's light source.

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