Patent Publication Number: US-9837047-B2

Title: Flat panel display having dynamic adjustment mechanism and image display method thereof

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a flat panel display and an image display method thereof, and more particularly, to a flat panel display having dynamic adjustment mechanism and an image display method thereof. 
     2. Description of the Prior Art 
     Along with the advantages of thin appearance, low power consumption, and low radiation, flat panel displays (FPDs) have been widely applied in various electronic products such as computer monitors, mobile phones, personal digital assistants (PDAs), or flat-panel televisions. Among existing flat panel displays, liquid crystal displays have gained higher popularity because of lower power consumption. Traditional liquid crystal display employs a three-color display technology based on RBG pixels to illustrate colors. However, while displaying images having high brightness, the performance of traditional liquid crystal display is unsatisfied. With the aim of enhancing image brightness, a four-color display technology is developed to illustrate colors based on RBGW pixels having white-color pixels. As the display technology of a liquid crystal display is switching from the three-color display technology to the four-color display technology, the areas available for disposing RGB pixels are reduced because of adding white-color pixels. For that reason, the liquid crystal display is incapable of accurately illustrating desirable brightness and chroma of the colors which are pure colors or close to pure colors. Furthermore, since the addition of white-color pixels causes lower brightness and chroma of the colors which are pure colors or close to pure colors, it is hard to achieve high reproducibility of images displayed based on the four-color display technology. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment of the present invention, a flat panel display having dynamic adjustment mechanism is provided for achieving high reproducibility of images displayed based on four color image signals. The flat panel display comprises a four-color conversion unit, a dynamic backlight control unit, a backlight module, a source driver, and a pixel array unit. The four-color conversion unit comprises a preliminary conversion lookup table. The four-color conversion unit is utilized for providing a first set of four color image signals corresponding to three color image input signals based on the preliminary conversion lookup table and providing a plurality of corresponding conversion scaling factors. Further, the four-color conversion unit is employed to convert the three color image input signals into a second set of four color image signals according to a backlight adjusting signal. The dynamic backlight control unit, electrically connected to the four-color conversion unit, is utilized for generating the backlight adjusting signal according to the conversion scaling factors. The backlight module, electrically connected to the dynamic backlight control unit, functions to provide a backlight output having an intensity adjusted according to the backlight adjusting signal. The source driver, electrically connected to the four-color conversion unit, is employed to provide a plurality of data signals based on the second set of four color image signals. The pixel array unit, electrically connected to the source driver, is put in use for displaying an image according to the data signals in coordination with the backlight output. 
     In accordance with another embodiment of the present invention, a flat panel display having dynamic adjustment mechanism is provided for achieving high reproducibility of images displayed based on four color image signals. The flat panel display comprises a four-color conversion unit, a dynamic backlight control unit, a compensation unit, a backlight module, a source driver, and a pixel array unit. The four-color conversion unit comprises a preliminary conversion lookup table. The four-color conversion unit is utilized for providing a first set of four color image signals corresponding to three color image input signals based on the preliminary conversion lookup table and providing a plurality of corresponding conversion scaling factors. The dynamic backlight control unit, electrically connected to the four-color conversion unit, is utilized for generating a backlight adjusting signal according to the conversion scaling factors. The compensation unit, electrically connected to the four-color conversion unit and the dynamic backlight control unit, is utilized for compensating the first set of four color image signals to become a second set of four color image signals according to the backlight adjusting signal. The backlight module, electrically connected to the dynamic backlight control unit, functions to provide a backlight output having an intensity adjusted according to the backlight adjusting signal. The source driver, electrically connected to the compensation unit, is employed to provide a plurality of data signals based on the second set of four color image signals. The pixel array unit, electrically connected to the source driver, is put in use for displaying an image according to the data signals in coordination with the backlight output. 
     The present invention further provides an image display method for use in a flat panel display for achieving high reproducibility of images displayed based on four color image signals. The image display method comprises: receiving a set of three color image input signals; providing a first set of four color image signals corresponding to the set of three color image input signals based on a preliminary conversion lookup table and providing a plurality of corresponding conversion scaling factors; providing a backlight adjusting signal according to the conversion scaling factors; adjusting the intensity of a backlight output according to the backlight adjusting signal; generating a second set of four color image signals according to the backlight adjusting signal; and displaying an image according to the second set of four color image signals in coordination with the backlight output. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a structural diagram schematically showing a flat panel display in accordance with a first embodiment of the present invention. 
         FIG. 2  is a structural diagram schematically showing a flat panel display in accordance with a second embodiment of the present invention. 
         FIG. 3  is a structural diagram schematically showing a flat panel display in accordance with a third embodiment of the present invention. 
         FIG. 4  is a flowchart depicting an image display method for use in a flat panel display according to a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Here, it is to be noted that the present invention is not limited thereto. Furthermore, the step serial numbers regarding the image display method are not meant thereto limit the operating sequence, and any rearrangement of the operating sequence for achieving same functionality is still within the spirit and scope of the invention. 
       FIG. 1  is a structural diagram schematically showing a flat panel display  100  in accordance with a first embodiment of the present invention. As shown in  FIG. 1 , the flat panel display  100  comprises a four-color conversion unit  110 , a dynamic backlight control unit  120 , a backlight driving unit  130 , a backlight module  140 , a source driver  170 , a gate driver  180 , and a pixel array unit  190 . The pixel array unit  190  comprises a plurality of pixel units  195 . Each pixel unit  195  includes a data switch Qd, a liquid crystal capacitor Clc, and a storage capacitor Cst. The source driver  170  is employed to provide plural data signals SD 1 ˜SDm. The gate driver  180  is employed to provide plural gate signals SG 1 ˜SGn for controlling related writing operations of the data signals SD 1 ˜SDm. And the pixel array unit  190  is put in use for displaying an image according to the data signals SD 1 ˜SDm in coordination with a backlight output provided by the backlight module  140 . 
     The four-color conversion unit  110 , electrically connected to the dynamic backlight control unit  120  and the source driver  170 , is utilized for converting three color image input signals Ri, Gi, Bi into four color image signals having a white-color image signal. The four-color conversion unit  110  includes a preliminary conversion lookup table  111  which is utilized for providing a first set of four color image signals corresponding to the three color image input signals Ri, Gi, Bi. That is, the preliminary conversion lookup table  111  provides a mapping relationship between the three color image input signals Ri, Gi, Bi and the first set of four color image signals. The four-color conversion unit  110  is further employed to provide a plurality of conversion scaling factors Ssca corresponding to the conversion of the three color image input signals Ri, Gi, Bi into the first set of four color image signals. The conversion scaling factors Ssca are forwarded to the dynamic backlight control unit  120 . In one embodiment, the conversion scaling factor Ssca of each set of three color image input signals Ri, Gi, Bi is determined according to whether the set of three color image input signals Ri, Gi, Bi is a pure color or close to a pure color and/or according to the brightness thereof. For instance, if a set of three color image input signals Ri, Gi, Bi is employed to display a blue color, which is one of three primitive colors and both the values of the signals Ri and Gi are zero, the corresponding conversion scaling factor Ssca can be set to zero. 
     The dynamic backlight control unit  120  includes a scaling factor analysis unit  121  and a backlight adjusting lookup table  123 . The scaling factor analysis unit  121  functions to generate an analysis value Sana through analyzing the conversion scaling factors Ssca corresponding to plural sets of three color image input signals Ri, Gi, Bi of each frame. In one embodiment, the scaling factor analysis unit  121  is employed to perform a statistical operation on the conversion scaling factors Ssca corresponding to the sets of three color image input signals Ri, Gi, Bi of each frame for providing plural counting values. Each of the counting values is corresponding to one conversion scaling factor Ssca. And an accumulation value is calculated through adding the counting values sequentially following an incremental order of the conversion scaling factors Ssca until the accumulation value approximates a preset value. Then, the greatest conversion scaling factor Ssca of the conversion scaling factors Ssca with the corresponding counting values being added is fetched, and the backlight output of the backlight module  140  is adjusted to be greater as the greatest conversion scaling factor Ssca is smaller. It is noted that the preset value can be the number of a preset percentage of total frame pixels, e.g. the number of 20% of total frame pixels. 
     The backlight adjusting lookup table  123  is used to provide a backlight adjusting signal Sadj corresponding to the analysis value Sana. That is, the backlight adjusting lookup table  123  provides a mapping relationship between the analysis value Sana and the backlight adjusting signal Sadj. In other words, the dynamic backlight control unit  120  is employed to provide the backlight adjusting signal Sadj corresponding to an analysis result of analyzing the conversion scaling factors Ssca by the scaling factor analysis unit  121 . The dynamic backlight control unit  120  is further employed to generate a conversion correction signal Scorr according to the backlight adjusting signal Sadj. The conversion correction signal Scorr is furnished to the four-color conversion unit  110 , and the four-color conversion unit  110  is further utilized for generating a corrected conversion lookup table according to the conversion correction signal Scorr and the preliminary conversion lookup table  111 . Moreover, the four-color conversion unit  110  employs the corrected conversion lookup table to provide a second set of four color image signals R′, G′, B′, W′ corresponding to the three color image input signals Ri, Gi, Bi. It is noted that W′ represents a white-color image signal. The second set of four color image signals R′, G′, B′, W′ is forwarded to the source driver  170  for generating the data signals SD 1 ˜SDm accordingly. The backlight driving unit  130 , electrically connected between the dynamic backlight control unit  120  and the backlight module  140 , employs the backlight adjusting signal Sadj to generate a pulse width modulation (PWM) signal Spwm for driving the backlight module  140  to emit a desirable backlight output. The backlight driving unit  130  includes a duty cycle adjusting unit  135  for adjusting the duty cycle of the PWM signal Spwm according to the backlight adjusting signal Sadj. 
     In one embodiment, regarding the image signals of each frame to be displayed, if the quantity of image signals which are pure colors or close to pure colors is greater, i.e. the quantity of the conversion scaling factors Ssca less than a predetermined threshold is greater, the backlight adjusting signal Sadj provided by the backlight adjusting lookup table  123  is also greater for enhancing the backlight output of the backlight module  140 . Further, the image signal which is neither a pure color nor close to a pure color is adjusted according to the backlight adjusting signal Sadj. However, the adjustment of the image signal which is a pure color or close to a pure color is optional. In another embodiment, the backlight adjusting signal Sadj is roughly proportional to the quantity of image signals which are pure colors or close to pure colors, and the increase of the backlight output is roughly proportional to the backlight adjusting signal Sadj. Also, the conversion correction signal Scorr is roughly proportional to the backlight adjusting signal Sadj. That is, the decrease of the image signal which is neither a pure color nor close to a pure color is roughly proportional to the increase of the backlight output. 
     In summary, the flat panel display  100  enhances the backlight output according to the quantity of image signals which are pure colors or close to pure colors, and lowers the value of the image signal which is neither a pure color nor close to a pure color according to the increase of the backlight output, for achieving high reproducibility of images displayed based on four color image signals. 
       FIG. 2  is a structural diagram schematically showing a flat panel display  200  in accordance with a second embodiment of the present invention. As shown in  FIG. 2 , the structure of the flat panel display  200  is similar to that of the flat panel display  100  shown in  FIG. 1 , differing in that the four-color conversion unit  110  is replaced with a four-color conversion unit  210 . The four-color conversion unit  210  includes a preliminary conversion lookup table  211  and a plurality of input conversion lookup tables  215 _ 1 ˜ 215 _N. The functionality of the preliminary conversion lookup table  211  is substantially identical to that of the preliminary conversion lookup table  111  shown in  FIG. 1  and, for the sake of brevity, further similar discussion thereof is omitted. After the four-color conversion unit  210  receives the conversion correction signal Scorr from the dynamic backlight control unit  120 , the four-color conversion unit  210  will select one corresponding input conversion lookup table out of the input conversion lookup tables  215 _ 1 ˜ 215 _N according to the conversion correction signal Scorr. The corresponding input conversion lookup table selected is then utilized for providing the second set of four color image signals R′, G′, B′, W′ corresponding to the three color image input signals Ri, Gi, Bi. In comparison with the four-color conversion unit  110 , the four-color conversion unit  210  is not required to perform related calculation operations for generating the aforementioned corrected conversion lookup table according to the conversion correction signal Scorr and the preliminary conversion lookup table  111 , for enhancing signal processing speed. 
       FIG. 3  is a structural diagram schematically showing a flat panel display  300  in accordance with a third embodiment of the present invention. As shown in  FIG. 3 , the flat panel display  300  comprises a four-color conversion unit  310 , a dynamic backlight control unit  320 , a backlight driving unit  330 , a backlight module  340 , a compensation unit  350 , a source driver  370 , a gate driver  380 , and a pixel array unit  390 . The pixel array unit  390  comprises a plurality of pixel units  395 . Each pixel unit  395  includes a data switch Qd, a liquid crystal capacitor Clc, and a storage capacitor Cst. The source driver  370  is employed to provide plural data signals SD 1 ˜SDm. The gate driver  380  is employed to provide plural gate signals SG 1 ˜SGn for controlling related writing operations of the data signals SD 1 ˜SDm. And the pixel array unit  390  is put in use for displaying an image according to the data signals SD 1 ˜SDm in coordination with a backlight output provided by the backlight module  340 . 
     The four-color conversion unit  310 , electrically connected to the dynamic backlight control unit  320  and the compensation unit  350 , is utilized for converting three color image input signals Ri, Gi, Bi into a first set of four color image signals R 1 , G 1 , B 1 , W 1 , where W 1  represents a white-color image signal. The four-color conversion unit  310  includes a preliminary conversion lookup table  311  for providing the first set of four color image signals R 1 , G 1 , B 1 , W 1  corresponding to the three color image input signals Ri, Gi, Bi. That is, the preliminary conversion lookup table  311  provides a mapping relationship between the three color image input signals Ri, Gi, Bi and the first set of four color image signals R 1 , G 1 , B 1 , W 1 . The first set of four color image signals R 1 , G 1 , B 1 , W 1  is delivered to the compensation unit  350 . The four-color conversion unit  310  is further employed to provide a plurality of conversion scaling factors Ssca corresponding to the conversion of the three color image input signals Ri, Gi, Bi into the first set of four color image signals R 1 , G 1 , B 1 , W 1 . The conversion scaling factors Ssca are forwarded to the dynamic backlight control unit  320 . 
     The dynamic backlight control unit  320  includes a scaling factor analysis unit  321  and a backlight adjusting lookup table  323 . The scaling factor analysis unit  321  functions to analyze the conversion scaling factors Ssca for generating an analysis value Sana. And the backlight adjusting lookup table  323  is used to provide a backlight adjusting signal Sadj corresponding to the analysis value Sana. That is, the backlight adjusting lookup table  323  provides a mapping relationship between the analysis value Sana and the backlight adjusting signal Sadj. The dynamic backlight control unit  320  is further employed to generate a conversion correction signal Scorr according to the backlight adjusting signal Sadj. The conversion correction signal Scorr is furnished to the compensation unit  350 . 
     The compensation unit  350  includes a plurality of compensation lookup tables  355 _ 1 ˜ 355 _N. After the compensation unit  350  receives the conversion correction signal Scorr from the dynamic backlight control unit  320 , the compensation unit  350  will select one corresponding compensation lookup table out of the compensation lookup tables  355 _ 1 ˜ 355 _N according to the conversion correction signal Scorr. The corresponding compensation lookup table selected is then utilized for compensating the first set of four color image signals R 1 , G 1 , B 1 , W 1  to become a second set of four color image signals R 2 , G 2 , B 2 , W 2 . The second set of four color image signals R 2 , G 2 , B 2 , W 2  is forwarded to the source driver  370  for generating the data signals SD 1 ˜SDm accordingly. The backlight driving unit  330 , electrically connected between the dynamic backlight control unit  320  and the backlight module  340 , employs the backlight adjusting signal Sadj to generate a pulse width modulation (PWM) signal Spwm for driving the backlight module  340  to emit a desirable backlight output. The backlight driving unit  330  includes a duty cycle adjusting unit  335  for adjusting the duty cycle of the PWM signal Spwm according to the backlight adjusting signal Sadj. 
     In one embodiment, regarding the image signals of each frame to be displayed, if the quantity of image signals which are pure colors or close to pure colors is greater, i.e. the quantity of the conversion scaling factors Ssca less than a predetermined threshold is greater, the backlight adjusting signal Sadj provided by the backlight adjusting lookup table  323  is also greater for enhancing the backlight output of the backlight module  340 . Further, the image signal which is neither a pure color nor close to a pure color is compensated according to the backlight adjusting signal Sadj. However, the compensation of the image signal which is a pure color or close to a pure color is optional. In another embodiment, the backlight adjusting signal Sadj is roughly proportional to the quantity of image signals which are pure colors or close to pure colors, and the increase of the backlight output is roughly proportional to the backlight adjusting signal Sadj. Also, the conversion correction signal Scorr is roughly proportional to the backlight adjusting signal Sadj. That is, the compensation of the image signal which is neither a pure color nor close to a pure color is roughly proportional to the increase of the backlight output. 
     In summary, the flat panel display  300  enhances the backlight output according to the quantity of image signals which are pure colors or close to pure colors, and compensates the value of the image signal which is neither a pure color nor close to a pure color according to the increase of the backlight output, for achieving high reproducibility of images displayed based on four color image signals. 
       FIG. 4  is a flowchart depicting an image display method for use in a flat panel display according to a preferred embodiment of the present invention. The image display method regarding the flow  900  shown in  FIG. 4  is implemented based on the flat panel display  100  shown in  FIG. 1 , the flat panel display  200  shown in  FIG. 2 , or the flat panel display  300  shown in  FIG. 3 . The image display method illustrated in the flow  900  comprises the following steps: 
     Step S 910 : receiving three color image input signals; 
     Step S 920 : providing a first set of four color image signals corresponding to the three color image input signals based on a preliminary conversion lookup table and providing a plurality of corresponding conversion scaling factors; 
     Step S 930 : providing a backlight adjusting signal according to the conversion scaling factors; 
     Step S 940 : adjusting the intensity of a backlight output according to the backlight adjusting signal; 
     Step S 950 : generating a conversion correction signal according to the backlight adjusting signal; 
     Step S 960 : generating a second set of four color image signals according to the conversion correction signal; and 
     Step S 970 : displaying an image according to the second set of four color image signals in coordination with the backlight output. 
     In the flow  900  of the image display method, each set of four color image signals may comprise a white-color image signal. If the image display method disclosed in the flow  900  is implemented based on the flat panel display  100  shown in  FIG. 1 , the step S 960  of generating the second set of four color image signals according to the conversion correction signal comprises: generating a corrected conversion lookup table according to the conversion correction signal and the preliminary conversion lookup table; and providing the second set of four color image signals corresponding to the three color image input signals based on the corrected conversion lookup table. If the image display method disclosed in the flow  900  is implemented based on the flat panel display  200  shown in  FIG. 2 , the step S 960  of generating the second set of four color image signals according to the conversion correction signal comprises: selecting one corresponding input conversion lookup table out of plural input conversion lookup tables according to the conversion correction signal; and providing the second set of four color image signals corresponding to the three color image input signals based on the corresponding input conversion lookup table selected. If the image display method disclosed in the flow  900  is implemented based on the flat panel display  300  shown in  FIG. 3 , the step S 960  of generating the second set of four color image signals according to the conversion correction signal comprises: selecting one corresponding compensation lookup table out of plural compensation lookup tables according to the conversion correction signal; and compensating the first set of four color image signals to become the second set of four color image signals based on the corresponding compensation lookup table selected. 
     The step S 930  of providing the backlight adjusting signal according to the conversion scaling factors comprises: analyzing the conversion scaling factors for generating a corresponding analysis value; and providing the backlight adjusting signal according to the analysis value. In one embodiment, the analysis value is a quantity of the conversion scaling factors less than a predetermined threshold, i.e. the analysis value can be the quantity of the image signals which are pure colors or close to pure colors. The step S 940  of adjusting the intensity of the backlight output according to the backlight adjusting signal comprises: adjusting the duty cycle of a pulse width modulation signal according to the backlight adjusting signal; and providing the backlight output according to the pulse width modulation signal. In one embodiment, the increase of the duty cycle is roughly proportional to the backlight adjusting signal, i.e. the increase of the backlight output is roughly proportional to the quantity of the image signals which are pure colors or close to pure colors. 
     In conclusion, the flat panel display of the present invention enhances backlight output according to the quantity of image signals which are pure colors or close to pure colors, and lowers the value of the image signal which is neither a pure color nor close to a pure color according to the increase of backlight output, for achieving high reproducibility of images displayed based on four color image signals. 
     The present invention is by no means limited to the embodiments as described above by referring to the accompanying drawings, which may be modified and altered in a variety of different ways without departing from the scope of the present invention. Thus, it should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alternations might occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.