Patent Publication Number: US-7903066-B2

Title: Image processing device and method thereof and image display device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of U.S. provisional application Ser. No. 60/864,977, filed on Nov. 9, 2006. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image processing device and a method thereof. More particularly, the present invention relates to a method and device for dynamically adjusting and improving image display contrast. 
     2. Description of Related Art 
     As the rapid development of electronic devices having display panels (e.g., wireless communication devices or PDAs), the demand for high-quality display on the electronic device becomes increasingly high. Therefore, it has become an issue to reduce the cost and to improve the image display quality. 
     Recently, adjustment of display brightness and color saturation has been developed. When a digital image data is input, a decoder converts the digital image data into an analog voltage signal based on voltages generated by a gray scale voltage generation circuit. It can be known that the gray scale voltages may affect brightness and color saturation of image display. In the state of the art, for example, U.S. Pat. No. 6,275,207 discloses that different setting of a register may change voltages generated by the gray scale voltage generation circuit, so as to increase the display brightness. 
     In US patent application publication 2003/0169248 A1, a contrast adjustment method is provided to calculate an average brightness Y of input images, in which Y=CR*R+CG*G+CB*B, R, G, and B are respectively average values of red, green, and blue gray scale values, and CR, CG, CB are respectively weights for the red, green, and blue. According to Y value, the brightness of the image frame is identified as being dark, bright, or normal. According to the determination result, gamma curve is modified to achieve the optimal display contrast. In the state of art, it requires complex average value calculation, so a larger integrated circuit area is required, and as a result, the circuit area and the manufacturing cost are increased. 
     Therefore, it is to provide an image processing device and a method thereof capable of dynamically adjusting and improving display contrast and display quality without complex architectures, so as to reduce the cost. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an image processing and a display mechanism, capable of improving image dynamic contrast and displaying high-quality image through simple operations and simple hardware architecture. 
     The present invention is also directed to an image processing and display mechanism, capable of displaying an image via a suitable gamma curve, by image recognition and threshold value comparison according to image characteristics, so as to dynamically adjust the image contrast. 
     The present invention is further directed to an image processing and display mechanism, capable of obtaining more suitable gamma curves by intensity analysis and approximation calculation in addition to the image recognition and threshold value comparison, so as to dynamically adjust the display contrast. 
     In an embodiment of the present invention, an image processing device is provided, which includes a gray scale distribution calculation unit, for receiving an input image signal which including color gray signals such as R, G, B gray scale values, and obtaining a gray scale distribution of the input image signal in a plurality of blocks; an image characteristic determination unit, for comparing the gray scale distribution of the input image signal in the blocks with a threshold value to obtain a comparison result, so as to determine a contrast characteristic of the input image signal; a look-up table unit, for storing a plurality of sets of gamma curve setting values, and outputting a set of gamma curve setting values in response to the comparison result; a register unit, for registering and outputting the set of gamma curve setting values output by the look-up table unit to a gray scale voltage generation circuit to generate a gray scale voltage. The gamma curve can be dynamically adjusted, so as to improve the display contrast and to enhance the frame quality. The image processing device may further includes an interpolation calculation unit, for performing interpolation on the set of gamma setting values output by the look-up table unit to obtain a new set of gamma setting values, so as to perform fine adjustment on the gamma curve. The gray scale voltage generation circuit further generates the gray scale voltage according to the fine-adjusted gamma curve. The gamma curve may be dynamically adjusted, so as to improve the display contrast and to enhance the display quality. 
     In another embodiment of the present invention, an image display device is provided, which includes a driving circuit, for receiving an input image and obtaining a suitable gamma curve by image recognition and threshold value comparison and/or intensity analysis, so as to dynamically adjust the image contrast; and a display panel, for displaying the input image according to a gray scale voltage generated by the driving circuit. The image display device is capable of dynamically adjusting the image contrast, and thus achieving an image display with high display contrast and high definition. 
     In still another embodiment of the present invention, an image processing method is provided, which includes: receiving an input image signal; obtaining a gray scale distribution of all pixels of the input image signal in a plurality of blocks; comparing the gray scale distribution of the input image signal with a threshold value to obtain a comparison result, so as to determine a contrast characteristic of the input image signal; selecting a set of gamma curve setting values from a plurality of sets of pre-stored gamma curve setting values in response to the comparison result; and generating a gray scale voltage in response to the selected set of gamma curve setting values. The image processing method further includes performing interpolation on the selected set of gamma curve setting values to obtain another set of gamma curve setting values, for performing the fine adjustment on the gamma curve. 
     In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a schematic view of an adaptive gamma control unit according to a first embodiment of the present invention. 
         FIG. 2  is a schematic view of gray scale distribution. 
         FIG. 3  is a schematic view of image characteristic comparison result. 
         FIG. 4  is a schematic view of a preset gamma curve. 
         FIG. 5  is a schematic view of an adaptive gamma control unit according to a second embodiment of the present invention. 
         FIG. 6  is a schematic view of gray scale distribution. 
         FIG. 7  is a schematic view of image characteristic determination result. 
         FIG. 8  is a schematic view of calculation result for gamma interpolation. 
         FIG. 9  is a block diagram of an image display device according to a third embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     In embodiments of the present invention, gray scale distribution of input image data is analyzed to predict gamma setting values, so as to change voltages generated by the gray scale voltage generation circuit. In this manner, the gamma curve may be dynamically adjusted, so as to improve brightness and color saturation of image display. 
     First Embodiment 
     In the first embodiment of the present invention, according to gray scale distribution characteristics of input images, an adaptive gamma control unit may dynamically change the gamma curve, so as to improve display contrast.  FIG. 1  is a schematic block view of the adaptive gamma control unit according to the first embodiment of the present invention. Referring to  FIG. 1 , the adaptive gamma control unit  110  in the first embodiment of the present invention includes a gray scale distribution calculation unit  111 , an image characteristic determination unit  112 , a look-up table unit  113 , and a register unit  114 . 
     Referring to  FIGS. 2 to 4 , the operation of the first embodiment of the present invention is illustrated. 
     The gray scale distribution calculation unit  111  calculates the gray scale distribution of the input image IN. In the following description, it is assumed that the input image IN has 24 bit, in which the red gray scale value, green gray scale value, and blue gray scale value each has 8 bit. Therefore, the gray scale distribution corresponding to the input image IN is 0-255. The gray scale range of 0-255 is classified into a plurality of blocks. For example, gray scales 0 to 63 are classified as Block  1 , gray scales 64 to 127 are classified as Block  2 , gray scales 128 to 191 are classified as Block  3 , and gray scales 192 to 255 are classified as Block  4 . Of course, the way for block classification is not limited here. 
     In  FIG. 2 , an accumulative value of a block to which the gray scale of the input image IN belongs is added by 1. When all the R, G, B gray scale values of the input image are classified, the accumulative value of each block of the input image is obtained. For example, it is assumed that R, G, B gray scale values of a certain pixel of the input image IN are respectively 60, 100, and 150, and the accumulative values of Block  1 , Block  2 , and Block  3  are respectively added by 1. If the RGB gray scale values of a certain pixel of the input image IN are respectively 50, 60, and 70, the accumulative value of Block  1  is added by 2, and the accumulative value of Block  2  is added by 1. Further, as for an input image having resolution of 320*240, the sum of the accumulative values of Blocks  1 - 4  should be (320*240*3). 
     The image characteristic determination unit  112  determines the contrast characteristic of the input image. According to preset threshold values, the image characteristic determination unit  112  determines the gray scale distribution result obtained by the gray scale distribution calculation unit  111 . If the accumulative value of the block is greater than the threshold value, the comparison result is set to be “1”. If the accumulative value of the block is smaller than the threshold value, the comparison result is set to be “0”. In this manner, the contrast characteristic of the input image is obtained. As shown in  FIG. 3 , the accumulative values of the Block  1  to Block  4  of  FIG. 2  are compared with the threshold value  1  and the comparison result is [1, 0, 0, 0]. The accumulative values of the Block  1  to Block  4  are compared with the threshold value  2  and the comparison result is [1, 0, 1, 0]. According to the comparison results, the brightness of the input image can be known. 
     By looking up a table, the look-up table unit  113  selects one set from a plurality of sets of preset gamma setting values stored therein. The look-up table unit  113  pre-stores a plurality of sets of gamma setting values. Through a different gamma setting value, the gamma curve may be different, so the display contrast may be changed. As described above, the image characteristic determination unit  112  compares the block accumulative values with the threshold values to obtain the comparison result (for example, “10001010” as shown in  FIG. 3 ). According to the comparison result, the look-up table unit  113  may select one set of gamma setting values from the sets of preset gamma setting values stored therein. The selected gamma setting values may be used to change the gray scale voltage, that is, to change the gamma curve. 
     In  FIG. 4 , the dashed line represents the preset gamma curve, and the solid line represents the gamma curve selected in this embodiment. The drawing on the left represents that the brightness is adjusted to be lower, the drawing in the middle represents that the brightness is adjusted to be higher, and the drawing on the right represents that dark pixels in the image are displayed as being darker than original and the bright pixels in the image are displayed as being brighter than original (i.e. contrast is to be higher). 
     The register unit  114  registers the set of gamma setting values selected by the look-up table unit  113 . The register unit  114  outputs the selected set of gamma setting values to the gray scale voltage generation circuit  120 . In this manner, the voltages generated by the gray scale voltage generation circuit  120  may be changed. 
     The gray scale voltage generation circuit  120  may include, for example, a plurality of sets of variable resistors connected in series. Each set of variable resistors is formed by serially connecting a plurality of parallel combinations of switches and resistors. In response to control signals (i.e., the selected gamma setting values), the switches are turned on or turned off, such that the resistance of the variable resistor is changed. Therefore, the gray scale voltage generation circuit  120  may set or change the generated gray scale voltages according to the gamma setting values output by the register unit  114 . 
     According to this embodiment, the gamma curve may be dynamically adjusted according to the image characteristic of the input image, so as to improve the display contrast and to enhance the display quality. 
     Second Embodiment 
     In the first embodiment, the display contrast is adjusted through using the gamma curve. Therefore, the number of the sets of the gamma setting values determines (limits) degree for the contrast fine-adjustment. In the second embodiment, approximate calculation is used to obtain more sets of gamma setting values, such that the flexibility for the display contrast adjustment becomes higher.  FIG. 5  is a schematic block view of an adaptive gamma control unit  510  according to the second embodiment of the present invention. Referring to  FIG. 5 , the adaptive gamma control unit  510  in the second embodiment of the present invention includes a gray scale distribution calculation unit  511 , an image characteristic determination unit  512 , a look-up table unit  513 , a gamma approximation calculation unit  514 , and a register unit  515 . 
     Referring to  FIG. 4  and  FIGS. 6-8 , the operation of the second embodiment of the present invention is illustrated. 
     The operations of the gray scale distribution calculation unit  511  are similar to that of the gray scale distribution calculation unit  111 , so the details are not repeated here. 
     Most operations of the image characteristic determination unit  512  are similar to that of the image characteristic determination unit  112 , so the details are not repeated here. However, the image characteristic determination unit  512  obtains the maximum value of the accumulative values of all blocks, and the maximum value is defined as shown in  FIG. 6 . 
     By looking up a table, the look-up table unit  513  selects one set from a plurality of sets of preset gamma setting values. The image characteristic determination unit  512  compares the block accumulative values with the threshold values to obtain comparison result (for example, 10001010 as shown in  FIG. 3 ). According to the comparison result, the look-up table unit  513  may select one set of gamma setting values from the plurality of sets of preset gamma setting values stored therein. The selected gamma setting values may be used to change the gray scale voltages, that is, to change the gamma curve. 
     The gamma approximation calculation unit  514  achieves fine adjustment on the gamma curve through approximation calculation (e.g., interpolation or extrapolation). The gamma approximation calculation unit  514  may perform approximation calculation according to the maximum value of the gray scale blocks, so as to obtain another set of gamma setting values that may represent the fine-adjusted gamma curve. The gamma curves corresponding to the gamma setting values approximated by the gamma approximation calculation unit  514  are shown by solid lines of  FIG. 8 . 
     The register unit  515  registers the gamma setting values calculated by the gamma approximation calculation unit  514  and outputs the set of gamma setting values to the gray scale voltage generation circuit  520 , so as to change the voltages generated by the gray scale voltage generation circuit  520 . 
     The architecture and operation of the gray scale voltage generation circuit  520  may be similar to that of the gray scale voltage generation circuit  120  of the first embodiment, so it is not repeated here. 
     According to this embodiment, the gamma curve can be dynamically adjusted according to the image characteristics of the input image and the gamma curves may be fine-tuned via approximation calculation, so as to further improve the display contrast and to further enhance the display quality. 
     Third Embodiment 
       FIG. 9  is a block diagram of an image display device according to a third embodiment of the present invention. Referring to  FIG. 9 , an image display device  900  includes a driving circuit  910  and a display panel  920 . The driving circuit  910  further includes an adaptive gamma control unit  911  and a gray scale voltage generation unit  912 . In this embodiment, the architecture and operation of the adaptive gamma control unit  911  may be similar to that of the adaptive gamma control unit  110  or  510  of the above embodiments, so it is not repeated here. That is, the driving circuit  910  not only drives the display panel  920  to display the image, but also has a function of dynamically adjusting gamma curves. 
     The display panel  920  displays the input image signal according to the gray scale voltages generated by the gray scale voltage generation unit  912 . The display panel  920  may display the high-contrast color image. 
     To sum up, in the embodiments of the present invention, the image processing device and method thereof are provided. The gray scale distribution is determined through image recognition and the comparison result is sent to the look-up table unit to find out the corresponding gamma setting values, and meanwhile, the image intensity is determined through the image recognition, so as to obtain a set of gamma setting values. Even, approximation calculation (interpolation calculation or extrapolation calculation) may be performed on the above obtained gamma setting values, so as to obtain new gamma setting values for being stored into the register. Then, according to the looked-up or approximated gamma setting values, the gray scale voltages are changed. The gray scale distribution calculation unit utilizes simple accumulative calculation, without division, so the required space of the memory is saved and thereby cost is further reduced. The gamma curve is dynamically adjusted through look-up table and simple approximation calculation, so as to improve display quality and to achieve the optimal display contrast. In addition, the above embodiment of the present invention further provide an image display device with function of dynamically adjusting the gamma curve, which can achieve high display contrast and high definition. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.