Title of Invention

"IMAGE DEGRADATION CORRECTION IN NOVEL LIQUID CRYSTAL DISPLAYS WITH SPLIT BLUE SUBPIXELS"

Abstract

Systems and methods are disclosed to correct for image degraded signals on a liquid crystal display panel are disclosed. Panels that comprise a subpixel repeating group having an even number of subpixels in a first direction may have parasitic capacitance and other signal errors due to imperfect dot inversion schemes thereon. Techniques for signal correction and localizing of errors onto particular subpixels are disclosed.

Full Text

The present invention relates to liquid crystal display device, and more particularly to image degradation correction in liquid crystal display device. BACKGROUND [01] In comknonly owned United States Patent Applications: (1) United States Patent Application Serial No. 09/916,232 ("the '232 application"), entitled "ARRANGEMENT OF COLOR PIXELS FOR FULL COLOR IMAGING DEVICES WITH SIMPLIFIED ADDRESSING," filed My 25, 2001; (2) United States Patent Application Serial No. 10/278,353 ("the '353 application"), entitled "IMPROVEMENTS TO COLOR FLAT PANEL DISPLAY SUB-PD03L ARRANGEMENTS AND LAYOUTS FOR SUB-PIXEL RENDERING WITH INCREASED MODULATION TRANSFER FUNCTION RESPONSE," filed October 22, 2002; (3) United States Patent Application Serial No. 10/278,352 ("the '352 application"), entitled "IMPROVEMENTS TO COLOR FLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS FOR SUB-PIXEL RENDERING WITH SPLIT BLUE SUB-PIXELS," filed October 22,2002; (4) United States Patent Application Serial No. 10/243,094 ("the '094 application), entitled "IMPROVED FOUR COLOR ARRANGEMENTS AND EMITTERS FOR SUB-PIXEL RENDERING," filed September 13, 2002; (5) United States Patent Application Serial No. 10/278,328 ("the '328 application"), entitled "IMPROVEMENTS TO COLOR FLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS WITH REDUCED BLUE LUMINANCE WELL VISIBILITY," filed October 22. 2002; (6) United States Patent Application Serial No. 10/278,393 ("flie '393 application"), entitled "COLOR DISPLAY HAVING HORIZONTAL SUB-PDCEL ARRANGEMENTS AND LAYOUTS," filed October 22, 2002; (7) United States Patent Application Serial No. 01/347,001 ("&e '001 application") entitled "IMPROVED SUB-PIXEL ARRANGEMENTS FOR STRIPED DISPLAYS AND METHODS AND SYSTEMS FOR SUB-PIXEL RENDERING SAME," filed January 16, 2003, each of which is herein incorporated by reference in its entirety, novel sub-pixel arrangements are disclosed for improving the cost/performance carves for image display devices. [02] These improvements are particularly pronounced when coupled with sub-pixel rendering (SPR) systems and methods further disclosed in those applications and in commonly owned United States Patent Applications: (1) United States Patent Application Serial No. 10/051,612 ("the '612 application"), entitled "CONVERSION OF RGB PIXEL FORMAT DATA TO PENT1LE MATRIX SUB-PIXEL DATA FORMAT " filed January 16, 2002; (2) United States Patent Application Serial No. 10/150,355 (l [03] The present application is related to commonly owned United States Patent Applications: (1) United States Patent Application Serial No. 10/455,925 entitled "DISPLAY PANEL HAVING CROSSOVER CONNECTIONS EFFECTING DOT INVERSION", filed on June 6, 2003; (2) United States Patent AppEcation Serial No. 10/455,931 entitled "SYSTEM AND METHOD OF PERFORMING DOT INVERSION WITH STANDARD DRIVERS AND BACKPLANE ON NOVEL DISPLAY PANEL LAYOUTS", filed on June 6,2003; (3) United States Patent Application Serial No. 10/455,927 entitled "SYSTEM AND METHOD FOR COMPENSATING FOR VISUAL EFFECTS UPON PANELS HAVING FIXED PATTERN NOISE WITH REDUCED QUANTIZATION ERROR", filed on June 6, 2003; (4) United States Patent Application Serial No.10/456,806 entitled "DOT INVERSION ON NOVEL DISPLAY PANEL LAYOUTS WITH EXTRA DRIVERS", filed on June 6, 2003; and (5) United States Patent AppKcation Serial No. 10/456,838 entitled "LIQUID CRYSTAL DISPLAY BACKPLANE LAYOUTS AND ADDRESSING FOR NON-STANDARD SUBPDGEL ARRANGEMENTS," which are hereby incorporated herein by reference in their entirety. BRIEF DESCRIPTION OF THE DRAW! NGS [04] The accompanying drawings, which are incorporated in, and constitute 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. [OS] FIG. 1A shows a conventional RGB stripe panel having a 1x1 dot inversion scheme. [06] FIG. IB shows a conventional ROB stripe panel having a 1x2 dot inversion scheme. [07] FIG. 2 shows a panel having a novel subpixel repeating group with an even number of pixels in a first (row) direction. [08] FIG. 3 depicts a panel having the repeating grouping of FIG. 2 with multiple standard driver chips wherein any degradation of the image is placed onto the blue subpixels. [09] FIG. 4 depicts the phase relationships for the multiple driver chips of FIG. 3. [010] FIG. 5 depicts « panel having the subpixel repeating group of FIG. 2 wherein the driver chip driving the panel is a 4-phase chip wherein any degradation of the image is placed onto the blue subpixels. [011 ] FIG. 6 depicts a panel having a subpixel repeating group having two narrow columns of blue subpixels wherein substantially all or most of the degradation of the image is placed onto the narrow blue subpixel columns. DETAILED DESCRIPTION [012] 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. [013] 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 form a repeating group of subpixels 102 that comprise the panel [014] 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 Imown to drive the panel with a dot inversion scheme to reduce crosstalk or flicker. FIG. 1A depicts one particular dot inversion scheme - i.e. 1x1 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 BIG. 1A) of TFT 116. Mage data - delivered via the column tines - 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 ("0") 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 mis 1x1 dot inversion scheme. [015] FIG. IB depicts another conventional ROB stripe panel having another dot inversion scheme - i.e. 1x2 dot inversion. Here, the polarity scheme changes over the course of two rows - as opposed to every row, as in Ixl dot inversion. In both dot inversion schemes, a few observations are noted: (1) in 1x1 dot inversion, every two physically adjacent subpixels (in bom the horizontal and vertical direction) are of different polarity; (2) in 1x2 dot inversion, every two physically adjacent subpixels hi the horizontal direction are of different polarity; (3) across any given row, each successive colored subpixel has an opposite polarity to its neighbor. Thus, for example, two successive red subpixels along a row will be either (+,-} or (-,+). Of course, in 1x1 dot inversion, two successive red subpixels along a column will have opposite polarity, whereas in 1x2 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 AMI-CD panel. [016] FIG. 2 shows a panel comprising a repeat subpixel grouping 202, as further described in the '353 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 1x1 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 dispkyed. This observation also occurs with other novel subpixel repeat grouping - for example, the subpixel repeat grouping in FIG, 1 of die '352 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. [017] To prevent visual degradation and other problems within AMLCDs, not only must the polarity of data line transitions be randomized along each select line, but the polarity of data line transitions must also be randomized also for each color and locality within the display. While this randomization occurs naturally with RGB triplet color sub-pixels in combination with commonly-used alternate column-inversion data driver systems, this is harder to accomplish when an even-number of sub-pixels are employed along row lines. [01 8] In one even modulo design embodiment, rows are formed from a combination of smaller green pixels and less-numerous-but-larger red and blue pixels. Normally, the polarity of data line transitions is reversed on alternate data lines so that each pixel is capacitively coupled about equally to the data lines on either side of it This way, these capacitor-induced transient errors are about equal and opposite and tend to cancel one another out on the pixel itself. However in this case, the polarity of same-color subpixels is the same and image degradation can occur. [019] FIG. 3 shows an even mocialo pixel layout which utilises 2x1 dot inversion. Vertical image degradation is eliminated since same color subpixels alternate in polarity. Horizontal image degradation due to same-color subpixels is reduced by changing the phase of dot ii&veraioij periodically. Driver chips 301A teoagh D provide data to die display; the driver outputs are driven V, V,... or -,+»-,+»... The phasing of tbe polarity is shown in FIG. 4 for the first 4 toes of the display. For example, the first column of chip 301B has the phase -,- .+.+ [020] hi one embodiment, a subpixel - bordered on either side by column lines driving •i the same polarity at a given time - may suffer a decreased luminance for any given image signal So, two goals are to reduce the number of effected subpixels - and to reduce the image degradation effects of any particular subpixel that cannot avoid having been so impacted. Several techniques in mis application and in other related applications incorporated herein are designed to minimize both the number and the effects of image degraded subpixels. [021] One such technique is to choose which subpixels are to be degraded, if degradation may not be avoided, hi FIG. 3, the phasing is designed so as to localize the same-polarity occurrence on the circled blue subpixels 302. hi this manner, the polarity of same color subpixels along a row is inverted every two driver chips, which will minimize or eliminate the horizontal image degradation. The periodic circled blue subpixels 302 will be slightly darker (i.e for normally-black LCD) or lighter (i.e. for nonnally-white LCD) than other blue subpixels in the array, but since the eye is not as sensitive to blue luminance changes, the difference should be substantially less visible. [022] Yet another technique is to add a correction signal to any effected subpixels. If it is known which subpixels are going to have image degradation, then it is possible to add a correction signal to the image data signal. For example, most of the parasitic capacitance mentioned in this and other applications tend to lower the amount of luminance for effected subpixels. It is possible to heuristically or empirically determine (e.g. by testing patterns on particular panels) the performance characteristics of subpixels upon the panel and add back a signal to correct for the degradation. In particular to Figure 3, if it is desired to correct the small error on the circled pixels, then a correction term can be added to the data for the circled blue subpixels. [023] In yet another embodiment of the present invention, it is possible to design different driver chips that will further abate the effects of image degradation. As shown in FIG. 5, a four-phase clock, for example, is used for polarity inversion. By the use of this pattern, or patterns similar, only the blue subpixels in the array will have the same-polarity degradation. However, since all pixels are equally degraded, it will be substantially less visible to the human eye. If desired, a correction signal can be applied to compensate for the darker or lighter blue subpixels. [024] These drive waveforms can be generated with a data driver chip that provides for a more complex power-supply switching system than employed in the relatively simple alternate polarity reversal designs. In this two-stage data driver design, the analog signals are generated as they are done now in the first stage. However, the polarity-switching stage is driven with its own cross-connection matrix in the second stage of the data driver to provide the more complex polarity inversions indicated. [025] Yet another embodiment of the techniques described herein is to localize the image degradation effect on a subset of blue subpixels across the panel in bom the row and column directions. For example, a "checkerboard" of blue subpixels (i.e. slopping every other blue subpixel in either the row and/or column direction) might be used to localize the image degradation signal. As noted above, the human eye - with its decreased sensitivity in blue color spatial resolution - will be less likely to notice the error. It will be appreciated that other subsets of blue subpixels could be chosen to localize the error. Additionally, a different driver chip with four or fewer phases might be possible to drive such a panel [026] FIG. 6 is yet another embodiment of a panel 600 comprised substantially of a subpixel repeating group 602 of even modulo. In this case, group 602 is comprised of a checkerboard of red 104 and green 106 subpixels interspersed with two columns of blue 108 subpixels. As noted, it is possible (but not mandatory) to have the blue subpixels of smaller width than the red or the green subpixels. As may be seen, two neighboring columns of blue subpixels may share a same column driver through m interconnect 604, possibly with the TFTs of the blue subpixels appropriately remapped to avoid exact data value sharing. [027] With standard column drivers performing 2x1 dot inversion, it can be seen that blue subpixel column 606 has the same polarity as the column of red and green subpixels to its immediate right Although mis may induce image degradation (which may be compensated for with some correction signal), it is advantageous that the degradation is localized on the dark colored (e.g. blue) subpixel column; and, hence, less visible to the human eye. We claim: 1. A liquid crystal display device comprising: a panel substantially comprising a matrix of pixels, each pixel within the said matrix of pixels comprising an even number of subpixels in a first direction of that matrix; and a driver circuit sending image data and polarity signals to the panel in a second direction of the matrix, characterised in that the driver circuit sends a correction signal to a plurality of subpixels which have a substantially consistent luminance error. 2. The liquid crystal display device as claimed in claim 1, wherein the polarity signals are a dot inversion scheme. 3. The liquid crystal display device as claimed in claim 2, wherein the polarity signal is a 1x1 dot inversion scheme. 4. The liquid crystal display device as claimed in claim 2, wherein the polarity signal is a 1x2 dot inversion scheme. 5. The liquid crystal display device as claimed in claim 1, wherein the polarity signal is a four phase dot inversion scheme. 6. The liquid crystal display device as claimed in claim 1, wherein the plurality of subpixels having substantially consistent luminance errors are blue colored subpixels. 7. A method for correcting image degradation in a liquid crystal display device claimed in claim 1 comprising a panel, the panel substantially comprising a matrix of pixels, each pixel within the said matrix of pixels comprising an even number of subpixels in a first direction of that matrix, said subpixels receiving image data signals and polarity signals in a second direction of the matrix, and characterised in that the method comprises: determining subpixels which have a substantially consistent luminance error; determining a correction signal to apply to the subpixels; and adding said correction signal to said image data signal to the subpixels. 8. The method as claimed in claim 7, wherein determining subpixels further comprises: measuring the error displayed by a subpixel with a test signal. 9. The method as claimed in claim 7, wherein determining a correction signal further comprises: empirically testing a correction signal and verifying if said correction signal substantially corrects the error.

Documents:

5583-delnp-2005-abstract-26-05-2008.pdf

5583-delnp-2005-abstract.pdf

5583-DELNP-2005-Claims-19-05-2008.pdf

5583-delnp-2005-claims-26-05-2008.pdf

5583-delnp-2005-claims.pdf

5583-delnp-2005-correspondence-others-26-05-2008.pdf

5583-delnp-2005-correspondence-others.pdf

5583-delnp-2005-description (complete)-19-05-2008.pdf

5583-delnp-2005-description (complete)-26-05-2008.pdf

5583-delnp-2005-description (complete).pdf

5583-DELNP-2005-Drawings-19-05-2008.pdf

5583-delnp-2005-drawings.pdf

5583-delnp-2005-form-1.pdf

5583-delnp-2005-form-18.pdf

5583-delnp-2005-form-2-26-05-2008.pdf

5583-delnp-2005-form-2.pdf

5583-delnp-2005-form-26.pdf

5583-DELNP-2005-Form-3-19-05-2008.pdf

5583-delnp-2005-form-3.pdf

5583-delnp-2005-form-5.pdf

5583-delnp-2005-pct-210.pdf

5583-DELNP-2005-Petition-137-19-05-2008.pdf

5583-DELNP-2005-Petition-137a-19-05-2008.pdf

5583-DELNP-2005-Petition-138-19-05-2008.pdf

5583-DELNP-2005-Petition-138a-19-05-2008.pdf