Patent Grant
8120569
The present invention generally relates to an adjusting system and a method thereof, and more particularly to an apparatus and method for adaptively adjusting backlight luminance.
Generally, an liquid crystal display (LCD) mainly includes a transmissive type LCD, a reflective type LCD, and a semi-transmissive/semi-reflective type LCD. The transmissive type LCD has a backlight module, and the light source of the backlight module may be cold cathode fluorescent lamps (CCFLs), hot cathode fluorescent lamp (HCFLs), light emitting diodes (LEDs), or electro luminescent (EL) devices. Currently, the CCFL is widely used in most LCDs.
The light leakage of LCDs easily occurs in a dark-state having a low gray level. Further, because the LCD panel size is rapidly growing and the LCD panel is widely used in television sets, it is necessary to increase the viewing angle of LCD panels. However, the problem of light leakage associated with viewing angles should be strictly controlled. In addition, the backlight luminance is required to be adjusted dynamically because the dynamic contrast ratio of the LCD panel has to be increased to improve the display quality. However, conventionally, the above-mentioned problem is generally ignored when adjusting the luminance of the backlight because only the light in the environment is taken into account presently. Therefore, when employing a conventionally adjusting method, glimmer occurs easily in LCD panels. The luminance of LCD panels is not uniform, thereby degrading the display quality of LCD.
Consequently, there is a need to develop an adjusting system to improve the display quality of LCDs.
One object of the present invention is to provide a backlight adjusting system and method thereof for adaptively adjusting the intensity of image frame by a brightness compensating signal and adjusting the light intensity of the backlight module via the backlight control signal so that the image frame can uniformly be displayed on the LCD, and the power consumption of LCD is saved to decrease the operation temperature in order to extend the life span of the LCD.
Another object of the present invention is to provide a backlight adjusting system and method thereof for increasing the contrast ratio of the image frame by computing the dark-state ratio of the pixel data in the image frame to improve display quality of the LCD.
According to the above objects, the present invention sets forth an adjusting system and method thereof. The backlight adjusting system suitable for LCD display mainly includes an intensity-pair distribution device, a brightness compensation module electrically coupled to the intensity-pair distribution device, a frame-adjusting device electrically coupled to the brightness compensation module, a backlight control device electrically coupled to the intensity-pair distribution device and the brightness compensation module, and a backlight module electrically coupled to the backlight control device.
The intensity-pair distribution device receives a plurality of image frames to correspondingly generate a plurality of intensity-pair distribution values for each image frame, where each image frame is composed of a plurality of pixel data. The brightness compensation module computes a dark-state ratio of the pixel data of a current image frame in response to the intensity-pair distribution values of the current image frame, and computes a brightness index of the current image frame in response to the dark-state ratio for generating a brightness compensating signal based on the dark-state ratio and the brightness index of the current image frame. The frame adjusting device is used to adjust the brightness of the total pixel data of the current image frame in response to brightness compensating signals. In one embodiment, the data associated with the brightness compensating signals are stored into the brightness compensation storage unit and the brightness compensating data represent the brightness compensating profile.
The backlight control device is capable of updating the brightness index of the current image frame in response to the brightness index of a previous image frame and the intensity-pair distribution values of the current image frame for generating a backlight control signal of the current image frame. The backlight module adjusts the backlight of the backlight module in response to the backlight control signal from the backlight control device for adaptively matching the intensity of the current image frame with the luminance profile of backlight module.
According to the above-mentioned description, the brightness compensation module of the backlight adjusting system processes the intensity-pair distribution of image frame with the brightness index of the previous luminance profile of the backlight module to generate the compensating signal for modifying the image frame. Thus, the backlight module is compensated by the compensating signal to improve the frame uniformity and increase contrast ratio during the backlight adjustment. Further, the backlight control device processes the intensity-pair distribution of image frame with the brightness index of the previous luminance profile of the backlight module to generate the backlight control signal. The backlight control signal is used to generate new brightness index of the current luminance profile. Therefore, two signals, including the compensating signal and backlight control signal, are utilized to adaptively adjust the image frame and the backlight projected on the display device for showing the image frame. Consequently, the images are uniformly displayed on the display device to improve the display quality and the power consumption is saved for decreasing operation temperature of the display device.
In operation, the method of adjusting the backlight according to one embodiment of the present invention comprises the following steps: the intensity-pair distribution device receives a plurality of image frames; a plurality of intensity-pair distribution values of each of the frames are generated by the intensity-pair distribution device, wherein each of the image frames has a plurality of pixel data; the brightness compensation module computes a dark-state ratio of the pixel data in a current image frame in response to the intensity-pair distribution values of the current image frame, and computes a brightness index of the current image frame in response to the dark-state ratio for generating a brightness compensating signal based on the dark-state ratio and the brightness index of the current image frame; the brightness of the pixel data of the current image frame in response to the brightness compensating signal is adjusted by the frame-adjusting device; the brightness index of the current image frame in response to the brightness index of a previous image frame and the intensity-pair distribution values of the current image frame is updated by the backlight control device for generating a backlight control signal of the current image frame; and finally, the backlight module adjusts the backlight in response to the backlight control signal from the backlight control device for adaptively matching the intensity of the current image frame with the luminance profile of the backlight module.
The present invention provides a backlight adjusting system and method thereof for adaptively adjusting the brightness of image frame by a brightness compensating signal and adjusting the light intensity of the backlight module via the backlight control signal. Furthermore, the present invention provides a backlight adjusting system and method thereof for increasing the contrast ratio of the image frame.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
The present invention provides a backlight adjusting system and method thereof for adaptively adjusting the brightness of image frame by a brightness compensating signal and adjusting the light intensity of the backlight module via the backlight control signal. Furthermore, the present invention provides a backlight adjusting system and method thereof for increasing the contrast ratio of the image frame by computing the dark-state ratio of the pixel data in the image frame.
Please refer to
The intensity-pair distribution device 102 receives a plurality of image frames to correspondingly generate a plurality of intensity-pair distribution values of the image frames each, where each of the image frames is composed of a plurality of pixel data. The brightness compensation module 104 computes a dark-state ratio of the pixel data of a current image frame in response to the intensity-pair distribution values of the current image frame, and computes a brightness index of the current image frame in response to the dark-state ratio for generating a brightness compensating signal based on the dark-state ratio and the brightness index of the current image frame. The frame adjusting device 106 is used to adjust the brightness of the total pixel data of the current image frame in response to brightness compensating signal. In one embodiment, the data associated with the brightness compensating signal are stored into the brightness compensation storage unit 112 and the brightness compensating data represents the brightness compensating profile.
The backlight control device 108 is capable of updating the brightness index of the current image frame in response to the brightness index of a previous image frame and the intensity-pair distribution values of the current image frame for generating a backlight control signal of the current image frame. The backlight module 110 adjusts the backlight of the backlight module in response to the backlight control signal from the backlight control device for adaptively matching the intensity of the current image frame with the luminance profile of backlight module.
According to the above-mentioned description, the brightness compensation module 104 of the backlight adjusting system 100 processes the intensity-pair distribution of image frame with the brightness index of the previous luminance profile of the backlight module 110 to generate the compensating signal for modifying the image frame. Thus, the backlight module 110 is compensated by the compensating signal to improve the frame uniformity and increase contrast ratio during the backlight adjustment. Further, the backlight control device 108 processes the intensity-pair distribution of image frame with the brightness index 118b of the previous luminance profile of the backlight module 110 to generate the backlight control signal. The backlight control signal is used to generate new brightness index 118a of the current luminance profile. Therefore, two signals, including the compensating signal and backlight control signal, are utilized to adaptively adjust the image frame and the backlight projected on the display device for showing the image frame. Consequently, the images are uniformly displayed on the display device 114 to improve the display quality and the power consumption 114 is saved for decreasing operation temperature of the display device.
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Further, in the present invention, the brightness index of the current image frames is the sum of the largest gray level multiplying a first weighting value and the dark-state ratio multiplying a second weighting value for each image frames. That is, intensity-pair distribution values of the pixel data of image frame each are computed and the largest value of the pixel data having a gray level “k”, are generated. Then, brightness index (BI) is defined as follows: BI=q*k+(1−q)*BR, where q is a first weighting value and adjustable value in the range from 0 to 1. It should be noted that the first weighting value can be arbitrary positive integer. The expression of (1−q) is defined as a second weighting value. The brightness index (BI) represents the ratio between dark-state and brightness-state of the pixel data in an image frame. The brightness index (BI) further serves as the parameter for modifying the image frame and the backlight.
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In detail, the detection mechanism of background brightness of image frame is determined by the intensity-pair distribution profile between the current image frame and the previous image frame. When the intensity-pair distribution profile of the previous image frame and current image frame is (n) and (n+1), respectively, and represented as follows:
Hn(0), Hn(1), . . . , Hn(a);and
Hn+1(0), Hn+1(1), . . . , Hn+1(a),
where “a” is an arbitrary positive integer, such as gray level “k”.
Formula (1) represents that “D_S” is the sum of the intensity-pair distribution differences between the current image frame and the previous image frame.
Formula (2) represents that “S” is the total sum of the intensity-pair distributions.
According to the above-mentioned description, the frame difference “hist_diff_ratio” is represented as expression (D_S/S). When the brightness index of the previous image frame is different from the target brightness index, the frame detection module adjusts the brightness index of the current image frame to the target brightness index in response to the frame difference. For example, when the scene of the image frame is changed fast and thus obvious glimmer is accompanied with the scene of the image frame. Therefore, the brightness index can be directly adjusted to the desired brightness. On the contrary, when the scene of the image frame is changed smoothly, the brightness index is gradually adjusted to avoid obvious glimmer of the scene of the image frame.
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Since the user is sensitive to the contrast of the image frame but senses the brightness change of the image frame with difficulty, the brightness should be retained without change to avoid frame glimmer due to brightness change when the contrast of the image frame is invariant. Particularly, the contrast (CR) of the image frame is defined as the subtraction result of the highest brightness and lowest brightness in one image frame, i.e. the expression of CR=max(Y)−min(Y). When the contrast difference between the contrast (CR_n) of current image frame (n) and the contrast (CR_n+1) of previous image frame (n+1) is smaller than threshold value (CR_th), it means that the contrast between the current image frame (n) and previous image frame (n+1) is approximately the same and thus the backlight luminance is not adjusted. Conversely, when the contrast difference between the contrast (CR_n) of current image frame (n) and the contrast (CR_n+1) of previous image frame (n+1) is smaller than threshold value (CR_th), it is necessary to adjust the backlight luminance.
In one embodiment, when the brightness index of the previous image frame is different from the target brightness index, the frame detection module adjusts the brightness index of the current image frame to the target brightness index in response to the image frame difference. A change interval corresponding to the image frame difference is defined as “BR_INC” and includes: (a) frame difference ratio; (b) brightness difference ratio; and (c) predetermined difference ratio. They will be depicted in detail below.
(a) Frame Difference Ratio
The frame difference is defined as the difference “hist_diff_ratio” between the current image frame and the previous image frame. When the frame difference is “K” and change margin at a time is predetermined ratio “c”, the change interval is equal to the expression of “c*K”. For example, when the current brightness index is termed as “BR_curr” and the target brightness index is termed as “BR_dest”, the next brightness index is equal to the expression “BR_curr+(c*K)” so that the expression result is approximately equal to “BR_dest”.
For example, the brightness index “BR_curr” of current image frame is 100, the target brightness index is 127, frame difference is 20, the predetermined ratio “c” is 0.5, and the brightness change process is listed as follows:
The brightness index in first change is: 100+20*0.5=110;
The brightness index in second change is: 110+20*0.5=120; and
The brightness index in third change is: 120+20*0.5=130,
where the brightness index 130 in third change is greater than the target brightness index 127 and, hence, the target brightness index 127 is selected to be the output of brightness index.
When the current brightness index is greater than the target brightness index, the current brightness index should be decreased. For example, the current brightness index is 100, the target brightness index is 87, the frame difference is 20, the predetermined ratio “c” is 0.5, and the change process is listed as follows:
The brightness index in first change is: 100−20*0.5=90; and
The brightness index in second change is: 90−20*0.5=80,
where the brightness index 80 in second change is smaller than the target brightness index 87 and, hence, the target brightness index 87 serves as the output of brightness index.
(b) Brightness Difference Ratio
As shown in
When the difference between the current brightness and the target brightness index is more and more large, the frame difference should be increased and the frame difference is represented as the multiplication of the expression of (BR_dest−BR_curr) and predetermined ratio “c”. For example, the brightness index “BR_curr” of current image frame is 100, the target brightness index is 150, the predetermined ratio “c” is 0.5, and the change process is listed as follows:
The brightness index in first change is: 100+0.5*(150−100)=125;
The brightness index in second change is: 125+0.5*(150−125)=138; and
The brightness index in third change is: 138+0.5*(150−138)=144, where the result of brightness index 144 in third change is the brightness output.
(c) Predetermined Difference Ratio
As shown in
In a variety of frame difference, the brightness index reaches to the target brightness index by a predetermined difference ratio. For example, the current brightness index is 100, the target brightness index is 117, the predetermined ratio “c” is 0.5, and the change process is listed as follows:
The brightness index in first change is: 100+10=110; and
The brightness index in second change is: 110+10=120, where the brightness index 120 in second change is greater than the target brightness index 117 and, hence, the target brightness index 117 serves as the output of brightness index.
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In another embodiment, the brightness index is time-variant and the expression of (Pa/Pb) is time-variant. Therefore, the waveform output frequency of the brightness index is changeable for adjusting the backlight dynamically. As shown in
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In step S700, the intensity-pair distribution device 102 receives a plurality of image frames.
In step S702, a plurality of intensity-pair distribution values of each of the frames are generated by the intensity-pair distribution device 102, wherein each of the image frames has a plurality of pixel data.
In step S704, the brightness compensation module 104 computes a dark-state ratio of the pixel data in a current image frame in response to the intensity-pair distribution values of the current image frame, and computes a brightness index of the current image frame in response to the dark-state ratio for generating a brightness compensating signal based on the dark-state ratio and the brightness index of the current image frame.
In step S706, the brightness of the pixel data of the current image frame in response to the brightness compensating signal is adjusted by the frame-adjusting device 106.
In step S708, the brightness index of the current image frame in response to the brightness index of a previous image frame and the intensity-pair distribution values of the current image frame is updated by the backlight control device 108 for generating a backlight control signal of the current image frame.
Finally, in step S710, the backlight module 110 adjusts the backlight in response to the backlight control signal from the backlight control device 108 for adaptively matching the intensity of the current image frame with the luminance profile of the backlight module 110.
The present invention provides a backlight adjusting system and method thereof for adaptively adjusting the brightness of image frame by a brightness compensating signal and adjusting the light intensity of the backlight module via the backlight control signal so that the image frame can uniformly be displayed on the LCD and the power consumption of LCD is saved to decrease the operation temperature to extend the life span of LCD. Furthermore, the present invention provides a backlight adjusting system and method thereof for increasing the contrast ratio of the image frame by computing the dark-state ratio of the pixel data in the image frame to improve display quality of LCD.
As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrative rather than limiting of the present invention. It is intended that they cover various modifications and similar arrangements be included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures.
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