Patent Publication Number: US-7218301-B2

Title: System and method of performing dot inversion with standard drivers and backplane on novel display panel layouts

Description:
RELATED APPLICATIONS 
     The present application is related to commonly owned (and filed on even date) U.S. Patent Applications: (1) U.S. patent publication Ser. No. 2004/0246213 (“the &#39;213 application”) [United States patent application Ser. No. 10/455,925] entitled “DISPLAY PANEL HAVING CROSSOVER CONNECTIONS EFFECTING DOT INVERSION”; and (2) U.S. patent publication Ser. No. 2004/0246278 (“the &#39;278 application”) [U.S. patent application Ser. No. 10/455,927] entitled “SYSTEM AND METHOD FOR COMPENSATING FOR VISUAL EFFECTS UPON PANELS HAVING FIXED PATTERN NOISE WITH REDUCED QUANTIZATION ERROR”; (3) U.S. patent publication Ser. No. 2004/0246279 (“the &#39;279 application”) [U.S. patent application Ser. No. 10/456,806] entitled “DOT INVERSION ON NOVEL DISPLAY PANEL LAYOUTS WITH EXTRA DRIVERS”; (4) U.S. patent publication Ser. No. 2004/0246404 (“the &#39;404 application”) [U.S. patent application Ser. No. 10/456,838] entitled “LIQUID CRYSTAL DISPLAY BACKPLANE LAYOUTS AND ADDRESSING FOR NON-STANDARD SUBPIXEL ARRANGEMENTS”; and (5) U.S. patent publication Ser. No. 2004/0246280 (“the &#39;280 application”) [U.S. patent application Ser. No. 10/456,839] entitled “IMAGE DEGRADATION CORRECTION IN NOVEL LIQUID CRYSTAL DISPLAYS,” which are hereby incorporated herein by reference. 
     BACKGROUND 
     In commonly owned U.S. Patent Applications: (1) U.S. patent publication Ser. No. 2002/0015110 (“the &#39;110 application”) [U.S. patent application Ser. No. 09/916,232], entitled “ARRANGEMENT OF COLOR PIXELS FOR FULL COLOR IMAGING DEVICES WITH SIMPLIFIED ADDRESSING,” filed Jul. 25, 2001; (2) U.S. patent publication Ser. No. 2003/0128225 (“the &#39;225 application”) [U.S. patent application Ser. No. 10,278,353], entitled “IMPROVEMENTS TO COLOR FLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS FOR SUB-PIXEL RENDERING WITH INCREASED MODULATION TRANSFER FUNCTION RESPONSE,” filed Oct. 22, 2002; (3) U.S. patent publication Ser. No. 2003/0128179 (“the &#39;179 application”) [U.S. patent application Ser. No. 10/278,352], entitled “IMPROVEMENTS TO COLOR FLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS FOR SUB-PIXEL RENDERING WITH SPLIT BLUE SUB-PIXELS,” filed Oct. 22, 2002; (4) U.S. patent publication Ser. No. 2004/0051724 (“the &#39;724 application”) [U.S. patent application Ser. No. 10/243,094], entitled “IMPROVED FOUR COLOR ARRANGEMENTS AND EMITTERS FOR SUB-PIXEL RENDERING,” filed Sept. 13, 2002; (5) U.S. patent publication Ser. No. 2003/0117423 (“the &#39;423 application”) [U.S. patent application Ser. No. 10/278,328], entitled “IMPROVEMENTS TO COLOR FLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS WITH REDUCED BLUE LUMINANCE WELL VISIBILITY,” filed Oct. 22, 2002; (6) U.S. patent publication Ser. No. 2003/0090581 (“the &#39;581 application”) [U.S. patent application Ser. No. 10/278,393], entitled “COLOR DISPLAY HAVING HORIZONTAL SUB-PIXEL ARRANGEMENTS AND LAYOUTS,” filed Oct. 22, 2002; (7) U.S. patent publication Ser. No. 2004/0080479 (“the &#39;479 application”) [U.S. patent application Ser. No. 10/347,001] entitled “IMPROVED SUB-PIXEL ARRANGEMENTS FOR STRIPED DISPLAYS AND METHODS AND SYSTEMS FOR SUB-PIXEL RENDERING SAME,” filed Jan. 16, 2003, novel sub-pixel arrangements are therein disclosed for improving the cost/performance curves for image display devices and herein incorporated by reference. 
     These improvements are particularly pronounced when coupled with sub-pixel rendering (SPR) systems and methods further disclosed in those applications and in commonly owned U.S. Patent Applications: (1) U.S. patent publication Ser. No. 2003/0034992 (“the &#39;992 application”) [U.S. patent application Ser. No. 10/051,612] entitled “CONVERSION OF A SUB-PIXEL FORMAT DATA TO ANOTHER SUB-PIXEL DATA FORMAT,” filed Jan. 16, 2002; (2) U.S. patent publication Ser. No. 2003/0103058 (“the &#39;058 application”) [U.S. patent application Ser. No. 10/150,355], entitled “METHODS AND SYSTEMS FOR SUB-PIXEL RENDERING WITH GAMMA ADJUSTMENT,” filed May 17, 2002; (3) U.S. patent publication Ser. No. 2003/0085906 (“the &#39;906 application”) [U.S. patent application Ser. No. 10/215,843], entitled “METHODS AND SYSTEMS FOR SUB-PIXEL RENDERING WITH ADAPTIVE FILTERING,” filed Aug. 8, 2002; (4) U.S. patent publication Ser. No. 2004/0196302 (“the &#39;302 application”) [U.S. patent application Ser. No. 10/379,767] entitled “SYSTEMS AND METHODS FOR TEMPORAL SUB-PIXEL RENDERING OF IMAGE DATA” filed Mar. 4, 2003; (5) U.S. patent publication Ser. No. 2004/0174380 (“the &#39;380 application”) [U.S. patent application Ser. No. 10/379,765] entitled “SYSTEMS AND METHODS FOR MOTION ADAPTIVE FILTERING,” filed Mar. 4, 2003; (6) U.S. patent publication Ser. No. 2004/0174375 (“the &#39;375 application”) [U.S. patent application Ser. No. 10/379,766] entitled “SUB-PIXEL RENDERING SYSTEM AND METHOD FOR IMPROVED DISPLAY VIEWING ANGLES” filed Mar. 4, 2003; (7) U.S. patent publication Ser. No. 2004/0196297 (“the &#39;297 application”) [U.S. patent application Ser. No. 10/409,413] entitled “IMAGE DATA SET WITH EMBEDDED PRE-SUBPIXEL RENDERED IMAGE” filed Apr. 7, 2002, which are hereby incorporated herein by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in, and constituted a part of this specification illustrate exemplary implementations and embodiments of the invention and, together with the description, serve to explain principles of the invention. 
         FIG. 1A  depicts a typical RGB striped panel display having a standard 1×1 dot inversion scheme. 
         FIG. 1B  depicts a typical RGB striped panel display having a standard 1×2 dot inversion scheme. 
         FIG. 2  depicts a novel panel display comprising a subpixel repeat grouping that is of even modulo. 
         FIG. 3  depicts the panel display of  FIG. 2  with one column driver skipped to provide a dot inversion scheme that may abate some undesirable visual effects. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to implementations and embodiments, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 1A  shows a conventional RGB stripe structure on panel  100  for an Active Matrix Liquid Crystal Display (AMLCD) having thin film transistors (TFTs)  116  to activate individual colored subpixels—red  104 , green  106  and blue  108  subpixels respectively. As may be seen, a red, a green and a blue subpixel from a repeating group of subpixels  102  that comprise the panel. 
     As also shown, each subpixel is connected to a column line (each driven by a column driver  110 ) and a row line (e.g.  112  and  114 ). In the field of AMLCD panels, it is known to drive the panel with a dot inversion scheme to reduce crosstalk and flicker.  FIG. 1A  depicts one particular dot inversion scheme—i.e. 1×1 dot inversion—that is indicated by a “+” and a “−” polarity given in the center of each subpixel. Each row line is typically connected to a gate (not shown in  FIG. 1A ) of TFT  116 . Image data—delivered via the column lines—are typically connected to the source of each TFT. Image data is written to the panel a row at a time and is given a polarity bias scheme as indicated herein as either ODD (“O”) or EVEN (“E”) schemes. As shown, row  112  is being written with ODD polarity scheme at a given time while row  114  is being written with EVEN polarity scheme at a next time. The polarities alternate ODD and EVEN schemes a row at a time in this 1×1 dot inversion scheme. 
       FIG. 1B  depicts another conventional RGB stripe panel having another dot inversion scheme—i.e. 1×2 dot inversion. Here, the polarity scheme changes over the course of tow rows as opposed to every row, as in 1×1 dot inversion. In both dot inversion schemes, a few observations are noted: (1) in 1×1 dot inversion, every two physically adjacent subpixels (in both the horizontal and vertical direction) are of different polarity; (2) in 1×2 dot inversion, every two physically adjacent subpixels in the horizontal direction are of different polarity; (3) across any given row, each successive colored subpixel has an opposite polarity to its neighbor. Thus, fore example, two successive red subpixels along a row will be either (+, −) or (−, +). Of course, in 1×1 dot inversion, two successive red subpixels along a column will have opposite polarity; whereas in 1×2 dot inversion, each group of two successive red subpixels will have opposite polarity. This changing of polarity decreases noticeable visual effects that occur with particular images rendered upon an AMLCD panel. It is generally known that the visual defects vertically will be minimal if the polarity of the same-color pixels changes frequently, but not necessarily every row; thus the 1×2 dot inversion is acceptable. 
       FIG. 2  shows a panel comprising a repeat subpixel grouping  202 , as further described in the &#39;225 application. As may be seen, repeat subpixel grouping  202  is an eight subpixel repeat group, comprising a checkerboard of red and blue subpixels with two columns of reduced-area green subpixels in between. If the standard 1×1 dot inversion scheme is applied to a panel comprising such a repeat grouping (as shown in  FIG. 2 ), then it becomes apparent that the property described above for RGB striped panels (namely, that successive colored pixels in a row and/or column have different polarities) is now violated. This condition may cause a number of visual defects noticed on the panel—particularly when certain image patterns are displayed. This observation also occurs with other novel subpixel repeat grouping—for example, the subpixel repeat grouping in  FIG. 1  of the &#39;179 application—and other repeat groupings that are not an odd number of repeating subpixels across a row. Thus, as the traditional RGB striped panels have three such repeating subpixels in its repeat group (namely, R, G and B), these traditional panels do not necessarily violate the above noted conditions. However, the repeat grouping of  FIG. 2  in the present application has four (i.e. an even number) of subpixels in its repeat group across a row (e.g. R,G,B, and G). It will be appreciated that the embodiments described herein are equally applicable to all such even modulus repeat groupings. 
     In the &#39;110 co-pending application, there is disclosed various layouts and methods for remapping the TFT backplane so that, although the TFTs of the subpixels may not be regularly positioned with respect to the pixel element itself (e.g. the TFT is not always in the upper left hand corner of the pixel element), a suitable dot inversion scheme may be effected on a panel having an even modulo subpixel repeat grouping. Other possible solutions are disclosed in the co-pending applications noted above. 
     One possible implementation that would not necessarily require a redesign of the TFT backplane or column driver chips is shown below in  FIG. 3 . Panel  300  comprises the subpixel repeating group as shown in  FIG. 2 . Column driver chip  302  connects to panel  300  via column lines  304 . Chip  302 , as shown, effects a 1×2 dot inversion scheme on panel  300 —as indicated by the “+” and “−” polarities indicated in each subpixel. The phase of pluses and minuses are indicated by the nomenclature φ 1  and φ 2 . 
     As may be seen, at certain points along chip  302 , there are column drivers that are not used (as indicated by short column line  306 ). “Skipping” a column driver in such a fashion on creates the desirable effect of providing alternating areas of dot inversion for same colored subpixels. For example, on the left side of dotted line  310 , it can be seen that the red colored subpixels along a given row have the same polarity. However, on the right side of dotted line  310 , the polarities of the red subpixels change. This change may have the desired effect of eliminating or abating any visual shadowing effects that might occur as a result of same-colored subpixel all having the same polarity. 
     This column driver skipping may be accomplished often enough across an entire panel to reduce or eliminate shadowing effects. How many times and in any given pattern may be determined heuristically. One possible side effect of skipping column drivers might be that at the columns where the driver is skipped, those adjoining columns have the same polarities going down the column line. This may have an undesirable visual effect, such as producing a darker or lighter column at this point—as depicted as oval  308 . 
     As is known upon manufacture of the panel itself where these skipped column drivers are on the panel, it is possible to compensate for any undesirable visual effect. As described in copending and commonly assigned U.S. patent application Ser. No. 10/455,927, entitled “SYSTEM AND METHOD FOR COMPENSATING FOR VISUAL EFFECTS UPON PANELS FIXED PATTERN NOISE WITH REDUCED QUANTIZATION ERROR” which is published as U.S. patent application Ser. No. 2004/0246278 and incorporated herein by reference, there are techniques that may be employed to reduce or possibly eliminate these visual effects. For example, a noise pattern may be introduced to the potential effected columns such that known or estimated darkness or brightness produced by such columns is adjusted. For example, if the column in question is slightly darker than those surrounding columns then the darker column may be adjusted to be slightly more ON than its neighbors. 
     It will be appreciated that, although it might be the easiest to skip one driver in the sequence of drivers along the driver circuit—and thereby having two adjacent columns of subpixels driven with the same polarity (thus, creating different regions of same colored subpixel polarity along a row), that there are other ways (perhaps less easy) to implement this effect. For example, it is possible to skip several (e.g. 3, 5, etc) drivers along a driver circuit to accomplish the same result. Additionally, it might be possible to skip drivers that are not in sequence and achieve the same desired effect with crossover connections or other interconnects. It suffices for the purposes of the present invention that a certain number of drivers are not used to create a more visually appealing panel. 
     Additionally, the technique of skipping drivers along a driver circuit is easily implemented with standard driver circuits wherein drivers in a sequence alternate polarity themselves. However, it is within the scope of the present invention whereby specialty driver circuits are constructed such that at least two adjacent drivers have the same polarity and thus the regions of different polarities of same colored subpixels may be effected by connecting these specialty drivers sequentially along the driver circuit. 
     The number of places or regions where same colored subpixel polarity is reversed can be determined heuristically or empirically. It suffices that such polarity reversals occur often enough to produce a panel that has user acceptability.