EP1553553A2 - Liquid crystal display driver for compensating viewing angle - Google Patents

Liquid crystal display driver for compensating viewing angle Download PDF

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Publication number
EP1553553A2
EP1553553A2 EP04019705A EP04019705A EP1553553A2 EP 1553553 A2 EP1553553 A2 EP 1553553A2 EP 04019705 A EP04019705 A EP 04019705A EP 04019705 A EP04019705 A EP 04019705A EP 1553553 A2 EP1553553 A2 EP 1553553A2
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Prior art keywords
pixels
gray scales
adjusted
intensity value
original
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EP04019705A
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German (de)
French (fr)
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EP1553553A3 (en
Inventor
Ying-Hao c/o Chi Mei Optoelectronics Corp. Hsu
Ming-Chia c/o Chi Mei Optoelectronics Corp. Shih
Wang-Yang c/o Chi Mei Optoelectronics Corp. Li
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Innolux Corp
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Chi Mei Optoelectronics Corp
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    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3607Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611Control of matrices with row and column drivers
    • G09G3/3685Details of drivers for data electrodes
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G5/00Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
    • G09G5/02Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the way in which colour is displayed
    • G09G5/06Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the way in which colour is displayed using colour palettes, e.g. look-up tables
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00Aspects of the constitution of display devices
    • G09G2300/04Structural and physical details of display devices
    • G09G2300/0439Pixel structures
    • G09G2300/0443Pixel structures with several sub-pixels for the same colour in a pixel, not specifically used to display gradations
    • G09G2300/0447Pixel structures with several sub-pixels for the same colour in a pixel, not specifically used to display gradations for multi-domain technique to improve the viewing angle in a liquid crystal display, such as multi-vertical alignment [MVA]
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00Aspects of the constitution of display devices
    • G09G2300/04Structural and physical details of display devices
    • G09G2300/0439Pixel structures
    • G09G2300/0452Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00Control of display operating conditions
    • G09G2320/02Improving the quality of display appearance
    • G09G2320/0271Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
    • G09G2320/0276Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00Control of display operating conditions
    • G09G2320/02Improving the quality of display appearance
    • G09G2320/028Improving the quality of display appearance by changing the viewing angle properties, e.g. widening the viewing angle, adapting the viewing angle to the view direction
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00Control of display operating conditions
    • G09G2320/02Improving the quality of display appearance
    • G09G2320/0285Improving the quality of display appearance using tables for spatial correction of display data
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2007Display of intermediate tones
    • G09G3/2018Display of intermediate tones by time modulation using two or more time intervals
    • G09G3/2022Display of intermediate tones by time modulation using two or more time intervals using sub-frames

Definitions

  • the present invention generally relates to a monitor display and, more particularly, to a display method and device for compensating color shifting in direct and side image viewing.
  • Fig. 1 is a diagram that illustrates an example of a conventional display system having a liquid crystal display (“LCD”) panel 100.
  • LCD panel 100 comprises 1024 red, green and blue (“RGB”) data lines, namely, 1024 x 3 data lines, and 768 scan lines.
  • the data lines and scan lines are respectively driven by a plurality of data drivers 102 and scan drivers 104.
  • a controller 106 outputs a data control signal ("Cntl_D") to data drivers 102, which accordingly receive and process the pixel data (“PD”) from controller 106.
  • each of data drivers 102 outputs corresponding voltages for driving 384 data lines in LCD panel 100.
  • Scan drivers 104 at the control of a scan control signal ("Cntl_S") from controller 106, respectively output scan signals and control 256 scan lines. A pixel is then defined at each intersection of a data line and a scan line. After scanning all of the scan lines, all of the pixels have been driven for completing the display of an image frame.
  • Cntl_S scan control signal
  • one embodiment of the present invention is directed to a liquid crystal display system and method that obviate one or more of the problems due to limitations and disadvantages of the related art.
  • a system comprising a liquid crystal display comprising a plurality of pixels having corresponding original luminance values, a plurality of data lines in the display, a plurality of data drivers for driving the data lines, and an adjusted gray scale generator for adjusting gray scales of the pixels and outputting adjusted gray scales to the pixels, to result in adjusted luminance values of the pixels.
  • Embodiments consistent with the present invention can include a method comprising the steps of driving a plurality of data lines in the display, measuring original luminance values corresponding to a plurality of pixels in the display, adjusting gray scales of a plurality of pixels in the display, and adjusting the original luminance values of the pixels according to the adjusted gray scales, wherein the original luminance values and the adjusted luminance values of the pixels when the display is viewed from a front view point are generally the same.
  • FIG. 1 For embodiments consistent with the present invention, can include a method comprising the steps of generating an original signal corresponding to a first intensity value for a pixel element in a display at a first frequency, converting the original signal into two correction signals corresponding to a second intensity value and a third intensity value respectively at double the first frequency, wherein the first intensity value is between the second and the third intensity value, and sequentially outputting the two correction signals into the pixel element.
  • Additional embodiments consistent with the present invention can include a display device for generating luminance for a pixel element comprising a circuit for generating an original signal corresponding to a first intensity value for said pixel element at a first frequency, a converter for converting said original signal into two correction signals corresponding to a second intensity value and a third intensity value respectively at double the first frequency, wherein the first intensity value is between the second and the third intensity value, and a memory for storing and outputting the two correction signals.
  • one embodiment of the present invention provides a display device comprising a plurality of pixels in rows and columns having a first color, a second color and a third color, wherein two adjacent pixels in one of the rows have the same color.
  • the present invention provides a display device comprising a plurality of pixels in rows and columns having a first color, a second color and a third color, wherein two adjacent pixels in one of the rows have the same color.
  • Fig. 1 is a diagram that illustrates an example of a conventional display system having a liquid crystal display (“LCD”) panel;
  • LCD liquid crystal display
  • Fig. 2 is a diagram that illustrates a coordinate system representing an end user viewing an LCD at a viewing position
  • Figs. 3A, 38 and 3C are diagrams that illustrate a relationship between normalized luminance and gray scales of different viewing angles for red, green and blue light, respectively;
  • Fig. 4 is a diagram that illustrates an example of a LCD display system with color shifting compensation for front and side viewing according to one embodiment of the present invention
  • Figs. 5A and 5B are graphical views comparing luminance values of pixels in a conventional display system and a system according to the present invention
  • Figs. 6A and 6B are diagrams showing examples of two adjacent images in a conventional display system
  • Fig. 7 is a diagram showing an example of an image being displayed in a display system consistent with the present invention.
  • Figs. 8A and 8B are diagrams showing examples of pixel matrices having a number of different pixel arrangements consistent with the present invention.
  • Fig. 9 is a graphical representation of the display results of the relationship between blue normalized luminance and gray scales (Gamma Curve) at different viewing angles in one embodiment of a normally black LCD;
  • Fig. 10 is a diagram that illustrates an example of a conventional LCD display system having an application specific integrated circuit ("ASIC"); and
  • Fig. 11 is a diagram that illustrates an example of an LCD display system having an application specific integrated circuit ("ASIC") with color shifting compensation for front and side viewing according to one embodiment of the present invention.
  • ASIC application specific integrated circuit
  • the color displayed by a pixel in an image frame is divided into two colors having less color shifting being displayed in two subframes, or two colors having less color shifting being displayed in two adjacent pixels.
  • Fig. 2 is a diagram that illustrates a coordinate system representing an end user viewing an LCD 200 at a viewing point Q.
  • Figs. 3A, 3B and 3C are diagrams respectively illustrating the relationship between normalized transmittance (or luminance) and gray scales for different viewing angles for red, green and blue light, where gray scales for the pixels range from 0 to 255.
  • the normalized transmittance (or luminance) value for a gray scale is the luminance of a front view corresponding to that gray scale divided by the maximum luminance for the front view, e.g., a gray scale value of 255 for a normally black display.
  • the normalized transmittance (luminance) value for a gray scale of a side view is the luminance of the side view corresponding to that gray scale divided by the maximum luminance for the side view.
  • the front view of the maximum luminance is different from the side view of the maximum luminance.
  • an angle ⁇ is defined between the line from the center of LCD 200 to the viewing point Q and the Z axis
  • an angle ⁇ is defined between the line projected from point Q onto LCD 200 and the X axis.
  • ⁇ , ⁇ (0°, 0°)
  • LCD 200 is being directly viewed from the front.
  • ( ⁇ , ⁇ ) (0°, 45°) or (0°, 60°)
  • LCD 200 is being viewed from the side at 45- and 60-degree angles, respectively.
  • Fig. 4 illustrates an embodiment consistent with the present invention that employs adjusting the gray scale in the time domain and includes an LCD 400 display system with color shifting compensation for front and side viewing.
  • LCD 400 comprises a plurality of pixels (a pixel being represented by, e.g., P(i, j), i and j being positive integers), data drivers 402, scan drivers 404, and a controller 406.
  • Controller 406 further comprises an adjusted gray scale generator 407.
  • One image frame is displayed in the LCD for each frame period.
  • a frame period is divided into n subframes SFP 1 through SFP n , n being a positive integer.
  • the original gray scales of pixels P(i, j) are GRO(i, j).
  • a lookup table stored in adjusted gray scale generator 407 records all original gray scales (GR0) and at least one corresponding adjusted gray scale GR1 through GRn.
  • Line d in Figs. 3A, 3B and 3C illustrates that Fig. 3C (the blue color) has the greatest difference between the front view and side view of normalized luminance. In view of this, the blue color may be adjusted first.
  • Table 1 below shows an example of such a lookup table for the original and adjusted gray scales for blue color in a specific embodiment of a normally black, 20.1-inch, liquid crystal display (“LCD").
  • the "Gray” represents the original gray scales for blue color
  • "LUT 1" and “LUT 2" represent the adjusted gray scales for blue color GR1 and GR2, respectively.
  • generator 407 (shown in Fig. 4) generates n adjusted gray scales from original gray scales GR0(i, j) for pixel P(i, j), including GR1(i, j), GR2(i, j) ... GRn(i, j).
  • the n adjusted gray scales are input into corresponding data drivers 402 sequentially and accordingly displayed in n subframes.
  • data drivers 402 drive pixels P(i, j) with n drive voltages corresponding to n adjusted gray scales.
  • Original gray scales GR0(i, j) correspond to the original normalized luminance of front views ("L0(i, j)") and side views ("L0'(i, j)").
  • adjusted normalized luminance for the front views and side views is determined from corresponding adjusted gray scales.
  • the sum of the absolute value of the difference between the adjusted normalized luminance values for the front and side views should be less than the sum of the absolute value of the difference between the original normalized luminance values for the front and side views. Color shifting between the front and side views is advantageously minimized as a result.
  • all of the adjusted normalized luminance values for the front views are generally the same as the original normalized luminance values for the front views, thereby assuring similarity between the original frame and the adjusted frame.
  • Figs. 5A and 5B are graphical views comparing normalized transmittance values of pixels in a conventional display system and a system consistent with the present invention, respectively.
  • Fig. 5A is a graphical view showing normalized transmittance values T(%) for pixels P(i, j) corresponding to original gray scales GR0 as the pixels are voltage driven, versus time, in a conventional display system.
  • Fig. 5B is a graphical view showing the normalized transmittance values T(%) for pixels P(i, j) corresponding to adjusted gray scales GR1 through GRn as the pixels are voltage driven, versus time.
  • a frame period (“FP") is divided into two subframe periods, namely SFP1 and SFP2.
  • respective adjusted normalized luminance values L1(i, j) and L1'(i, j) for the front and side views, respectively, are determined from adjusted gray scales GR1(i, j).
  • respective adjusted normalized luminance values L2(i, j) and L2'(i, j) for the front and side views, respectively, are determined from adjusted gray scales GR2(i, j).
  • drive voltages corresponding to original gray scales GR0(i, j) are used to drive pixels P(i, j) for a frame period in a conventional display system, where the functions of normalized transmittance values T0(t) and T0'(t) respectively correspond to front and side views of pixels P(i, j).
  • Original normalized luminance values L0(i, j) for the front view correspond to the integrated value of T0(t) within frame period FP.
  • original normalized luminance values L0'(i, j) for the side view correspond to the integrated value of T0'(t) within frame period FP.
  • drive voltages corresponding to adjusted gray scales GR1(i, j) are used to drive pixels P(i, j), where T1(t) and T1'(t) respectively represent the time function of normalized transmittance values for front and side views of pixels P(i, j).
  • drive voltages corresponding to adjusted gray scales GR2(i, j) are used to drive pixels P(i, j) where T2(t) and T2'(t) respectively represent the time function of normalized transmittance values for front and side views of pixels P(i, j).
  • Adjusted normalized luminance values L1 (i, j) for the front views correspond to the integrated value of T1(t) within subframe period SFP1 when drive voltages corresponding to adjusted gray scales GR1(i, j) are used to drive pixels P(i, j).
  • Adjusted normalized luminance values L1'(i, j) for the side view correspond to the integrated value of T1'(t) within subframe period SFP1 when drive voltages corresponding to adjusted gray scales GR1(i, j) are used to drive pixels P(i, j).
  • Adjusted normalized luminance values L2(i, j) for the front view correspond to the integrated value of T2(t) within subframe period SFP2 when drive voltages corresponding to adjusted gray scales GR2(i, j) are used to drive pixels P(i, j).
  • Adjusted normalized luminance values L2'(i, j) for the side view correspond to the integrated value of T2'(t) within subframe period SFP2 when drive voltages corresponding to adjusted gray scales GR2(i, j) are used to drive pixels P(i, j).
  • adjusted gray scales GR1(i, j) and GR2(i, j) corresponding to the sum of normalized luminance values L1(i, j) and L2(i, j) for the front views are generally the same as normalized original luminance values L0(i, j) for the front views.
  • the luminance for the pixels is attributed to the cumulative effect of luminance values for adjusted gray scales GR1 (i, j) and GR2(i, j) respectively corresponding to subframe periods SFP1 and SFP2, which approximates the luminance of original gray scales GR0 corresponding to pixels within a frame period FP in a conventional display system.
  • each of SFP1 and SFP2 is advantageously one half of frame period FP.
  • original gray scales GR0(i, j) are advantageously between adjusted gray scales GR1(i, j) and GR2(i, j).
  • adjusted gray scales GR1(i, j) are greater than GR2(i, j).
  • the absolute value of the difference of the normalized luminance value between the front and side (from 60 degrees) views for gray scale 0 is very small, which is well suited to serve as GR2(i, j).
  • Image display is properly ascertained by dynamically and continuously adjusting GR1(i, j) and GR2(i, j) within a frame period FP to achieve optimal luminance.
  • GR1(i, j) and GR2(i, j) can be (190, 0) or (0, 190), respectively.
  • original gray scales GR0(i, j) are fixed and corresponding normalized luminance values L0(i, j) are measured.
  • the original frame period is divided into two equivalent subframe periods. Since the change between front and side views for gray scale 0 is the smallest, and for reducing response time for driving liquid crystal elements, gray scale 0 is selected to be GR2(i, j). Since the characteristics for driving liquid crystal elements are not rectangular waves, adjustment is needed for GR1(i, j) and GR2(i, j) so that the sum of normalized luminance values L1(i, j) and L2(i, j) is generally the same as original normalized luminance values L0(i, j).
  • the cumulative effect of the differences between normalized luminance values for the front and side views corresponding to gray scales GR1(i, j) in SFP1 and normalized luminance values for the front and side views corresponding to gray scales GR2(i, j) in SFP2 is less, compared with the difference between normalized luminance values for the front and side views corresponding to gray scales GR0(i, j) in a frame period FP in a conventional system.
  • GR1(i, j) and GR2(i, j) accordingly obtained for all gray scales are then used to form the lookup table.
  • a further embodiment consistent with the present invention is implemented in the space domain for changing the gray scales. Color shifting with respect to the front and side views is compensated by displaying an image within a single frame period ("FP").
  • the display system includes a liquid crystal display (“LCD") further comprising a display panel, a plurality of data drivers, a plurality of scan drivers and a controller.
  • the panel further comprises a plurality of pixels
  • the controller further includes an adjusted gray scale generator.
  • the adjusted gray scale generator For two pixels Pa and Pb, the adjusted gray scale generator generates adjusted gray scales GRa1 and GRb1 for original gray scales GRa0 and GRb0 for the pixels Pa and Pb, respectively.
  • GRa0 and GRb0 respectively correspond to the original normalized luminance values for the front and side views (La and La'), and the original normalized luminance values for the front and side views (Lb and Lb').
  • data drivers respectively drive the two pixels Pa and Pb with first and second drive voltages corresponding to adjusted gray scales GRa1 and GRb1.
  • pixel Pa is driven with the first drive voltage
  • Pa includes adjusted normalized luminance values Lc and Lc' for the front and side views, respectively.
  • pixel Pb is driven with the second drive voltage
  • Pb includes adjusted normalized luminance values Ld and Ld' for the front and side views, respectively.
  • the adjusted gray scale generator comprises a lookup table, from which adjusted gray scales GRa1 and GRb1 are generated.
  • the lookup table records original gray scales GRa0 and GRb0, and corresponding adjusted gray scales GRa1 and GRb1.
  • pixels Pa and Pb are adjacent to each other and have the same color.
  • Original gray scales GRa0 and GRb0 are between adjusted gray scales GRa1 and GRb1.
  • Adjusted normalized luminance values for the front and side views (Lc and Ld, respectively) are generally the same as the sum of original normalized luminance values for the front and side views La and Lb.
  • Figs. 6A and 68 are diagrams showing examples of two adjacent images M and M+1 in a conventional display system.
  • Fig. 7 is a diagram showing an example of an image being displayed in a display system consistent with the present invention.
  • Red, green and blue pixels are respectively represented by letters R, G and B.
  • Original gray scales for adjacent pixels are generally close, e.g., blue pixels B11 and B21 having the same original gray scale at 128.
  • Adjusted gray scales GRa1 at 174 and GRb1 at 0 are selected when blue pixels B11 and B21 have the same original gray scale 128.
  • gray scales for blue pixels B11 and B21 are 174 and 0, respectively, consistent with the present invention.
  • gray scales for B11 and B21 are 0 and 174, respectively.
  • pixels having different colors have relatively large gaps therebetween.
  • pixel matrices can have a number of different pixel arrangements.
  • one embodiment of the present invention provides a display device comprising a plurality of pixels in rows and columns having a first color, a second color and a third color, wherein two adjacent pixels in one of the rows have the same color.
  • the present invention provides a display device comprising a plurality of pixels in rows and columns having a first color, a second color and a third color, wherein two adjacent pixels in one of the rows have the same color.
  • Figs. 8A and 8B are diagrams showing examples of pixel matrices having a number of different pixel arrangements.
  • two adjacent pixels in a row can also be the same color, as shown in Fig. 8A, such as a row of pixels GRBBRGGRB.
  • There can be different arrangements of mixed order for every row such as the order of the two adjacent rows GRBBRGGRB and BRGGRBBRG.
  • pixels G and B have the same adjacent pixel, so the gap between the two single-color pixels (G and B) is advantageously reduced.
  • the order of the pixels can be arranged so that two pixels are diagonally adjacent one another in an LCD panel, as shown in Fig. 8B. Referring to Fig.
  • a pair of red pixels R and a pair of blue pixels B are horizontally arranged, whereas a pair of green pixels G is located above or below the pair of red pixels R and the pair of blue pixels B. Green pixels G is further located in a mixed manner below red pixels R and blue pixels B, so pixels of the same color are adjacent along the diagonal lines in the LCD panel. Gaps between the single-color pixels are advantageously reduced as a result, as shown in Figs. 8A and 8B, which is conducive to optimizing the resolution for the pixels.
  • Figs. 10 and 11 are diagrams illustrating examples of an LCD display system having an application specific integrated circuit ("ASIC"), respectively without color shifting compensation (Fig. 10), and with color shifting compensation (Fig. 11) for front and side viewing according to one embodiment of the present invention.
  • ASIC application specific integrated circuit
  • an LCD panel 100 comprises 1024 red, green and blue (“RGB") data lines, namely, 1024 x 3 data lines, and 768 scan lines, similar to the LCD panel shown in Fig. 1.
  • the data lines and scan lines are respectively driven by a plurality of data drivers 102 and scan drivers 104.
  • a power supply 103 supplies power to data drivers 102 and scan drivers 104.
  • An ASIC 101 includes timing controller 106 that outputs a data control signal to data drivers 102, which accordingly receive and process the pixel data from controller 106. After processing the received pixel data, each of data drivers 102 outputs corresponding voltages for driving 384 data lines in LCD panel 100.
  • Scan drivers 104 at the control of a scan control signal from controller 106, respectively output scan signals and control 256 scan lines. After scanning all of the scan lines, all of the pixels have been driven for completing the display of an image frame.
  • Fig. 11 is a diagram that illustrates an example of an LCD display system having an application specific integrated circuit ("ASIC 411") with color shifting compensation for front and side viewing according to one embodiment of the present invention.
  • LCD 400 comprises a plurality of pixels (a pixel being represented by, e.g., P(i, j), i and j being positive integers), data drivers 402, scan drivers 404, and a timing controller 406, similar to the LCD panel shown in Fig. 4.
  • One image is displayed in the LCD for each frame period.
  • a frame period is divided into n subframes SFP 1 through SFP n , n being a positive integer.
  • the original gray scales of pixels P(i, j) are GR0(i, j).
  • a lookup table LUT1 records the original gray scales (GR0) and the corresponding adjusted gray scales GR1.
  • a lookup table LUT2 records the original gray scales (GR0) and corresponding adjusted gray scales GR2.
  • a power supply 403 supplies power to data drivers 402 and scan drivers 404.
  • Timing controller 406 in ASIC 401 outputs a data control signal to data drivers 402, which accordingly receive and process the pixel data from controller 406.
  • ASIC 411 further includes a data selector 405, LUT 1 and LUT 2, an interface 408 provided between LUT 2 and a memory 409 (which is an EEPROM).
  • embodiments of display devices and methods consistent with the present invention for compensating color shifting between front and side views of images can advantageously minimize the effects of color shifting and optimize image quality of the display device.
  • One embodiment is advantageously implemented in a multi-domain vertically aligned LCD.
  • embodiments consistent with the present invention can be implemented in an LCD for all of its pixels, or specifically implemented to particular pixels, to reduce the adverse effects of color shifting.

Abstract

A system comprises a liquid crystal display viewable from front and side view points, and comprising a plurality of pixels having corresponding original luminance values, a plurality of data lines in the display, a plurality of data drivers for driving the data lines, and an adjusted gray scale generator for adjusting gray scales of the pixels and outputting two adjusted gray scales to the data drivers for driving the data lines at double the frequency. Original gray scales correspond to the original normalized luminance of front views and side views. For the adjusted gray scales stored in the look up table corresponding to the original gray scales, the sum of the absolute value of the difference between the adjusted normalized luminance values for the front and side views should be less than the sum of the absolute value of the difference between the original normalized luminance values for the front and side views in order to minimise color shifting between the front and side views.

Description

    BACKGROUND OF THE INVENTION FIELD OF THE INVENTION
  • The present invention generally relates to a monitor display and, more particularly, to a display method and device for compensating color shifting in direct and side image viewing.
  • DESCRIPTION OF THE RELATED ART
  • Fig. 1 is a diagram that illustrates an example of a conventional display system having a liquid crystal display ("LCD") panel 100. LCD panel 100 comprises 1024 red, green and blue ("RGB") data lines, namely, 1024 x 3 data lines, and 768 scan lines. The data lines and scan lines are respectively driven by a plurality of data drivers 102 and scan drivers 104. A controller 106 outputs a data control signal ("Cntl_D") to data drivers 102, which accordingly receive and process the pixel data ("PD") from controller 106. After processing the received pixel data, each of data drivers 102 outputs corresponding voltages for driving 384 data lines in LCD panel 100. Scan drivers 104, at the control of a scan control signal ("Cntl_S") from controller 106, respectively output scan signals and control 256 scan lines. A pixel is then defined at each intersection of a data line and a scan line. After scanning all of the scan lines, all of the pixels have been driven for completing the display of an image frame.
  • There are differences in luminance with respect to LCD panel 100 as it is viewed from its front and sides, since retardation values differ for light entering into the liquid crystal material at different angles. That is, different viewing angles result in differences in transmittance and retardation values. For RGB light being mixed together as LCD panel 100 is viewed directly and from the sides, color shifting may result as each of the red, green and blue light is subject to frontal and side views.
  • In U.S. Patent No. 5,711,474, displaying images at different viewing angles with respect to an end user includes the division of a single pixel into a plurality of areas having different characteristics. Since the different areas in a pixel correspond to different viewing angles, and the pixel elements cannot be adjusted after the display is made. Consequently, the display quality and effect may be adversely affected.
  • In U.S. Patent No. 5,847,688, original signals are separately input and processed at two time frames and two pixels using different drivers according to gamma curves correspond to two different viewing angles. However, there may be display flicker during transition between two time frames of image display. Moreover, the composite image may have only one half of a pixel directed to displaying an image at a specific viewing angle, which could not properly provide image viewing at multiple angles. Display resolution may be adversely affected as a result.
  • In US2002/0149598, 2 x 2 or more subpixels are used for displaying images. Original images are adjusted according to calculations of proportionalities of luminance in the pixels for image display. However, multiple pixels are needed for displaying images.
  • There is thus a general need in the art for a system and method overcoming at least the aforementioned shortcomings in the art. A particular need exists in the art for a system and method overcoming disadvantages with respect to color shifting when an LCD panel is viewed directly and from the sides.
  • BRIEF SUMMARY OF THE INVENTION
  • Accordingly, one embodiment of the present invention is directed to a liquid crystal display system and method that obviate one or more of the problems due to limitations and disadvantages of the related art.
  • To achieve these and other advantages, and in accordance with the purpose of the present invention as embodied and broadly described, there is provided a system comprising a liquid crystal display comprising a plurality of pixels having corresponding original luminance values, a plurality of data lines in the display, a plurality of data drivers for driving the data lines, and an adjusted gray scale generator for adjusting gray scales of the pixels and outputting adjusted gray scales to the pixels, to result in adjusted luminance values of the pixels.
  • Embodiments consistent with the present invention can include a method comprising the steps of driving a plurality of data lines in the display, measuring original luminance values corresponding to a plurality of pixels in the display, adjusting gray scales of a plurality of pixels in the display, and adjusting the original luminance values of the pixels according to the adjusted gray scales, wherein the original luminance values and the adjusted luminance values of the pixels when the display is viewed from a front view point are generally the same.
  • Further embodiments consistent with the present invention can include a method comprising the steps of generating an original signal corresponding to a first intensity value for a pixel element in a display at a first frequency, converting the original signal into two correction signals corresponding to a second intensity value and a third intensity value respectively at double the first frequency, wherein the first intensity value is between the second and the third intensity value, and sequentially outputting the two correction signals into the pixel element.
  • Additional embodiments consistent with the present invention can include a display device for generating luminance for a pixel element comprising a circuit for generating an original signal corresponding to a first intensity value for said pixel element at a first frequency, a converter for converting said original signal into two correction signals corresponding to a second intensity value and a third intensity value respectively at double the first frequency, wherein the first intensity value is between the second and the third intensity value, and a memory for storing and outputting the two correction signals.
  • In one aspect, one embodiment of the present invention provides a display device comprising a plurality of pixels in rows and columns having a first color, a second color and a third color, wherein two adjacent pixels in one of the rows have the same color. In another aspect, the present invention provides a display device comprising a plurality of pixels in rows and columns having a first color, a second color and a third color, wherein two adjacent pixels in one of the rows have the same color.
  • Additional features and advantages of the present invention will be set forth in part in the detailed description which follows, and in part will be obvious from the detailed description, or may be learned by practice of the present invention. The features and advantages of the present invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
  • It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present invention, as claimed.
  • The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the present invention and together with the description, serve to explain the principles of the present invention.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • Fig. 1 is a diagram that illustrates an example of a conventional display system having a liquid crystal display ("LCD") panel;
  • Fig. 2 is a diagram that illustrates a coordinate system representing an end user viewing an LCD at a viewing position;
  • Figs. 3A, 38 and 3C are diagrams that illustrate a relationship between normalized luminance and gray scales of different viewing angles for red, green and blue light, respectively;
  • Fig. 4 is a diagram that illustrates an example of a LCD display system with color shifting compensation for front and side viewing according to one embodiment of the present invention;
  • Figs. 5A and 5B are graphical views comparing luminance values of pixels in a conventional display system and a system according to the present invention;
  • Figs. 6A and 6B are diagrams showing examples of two adjacent images in a conventional display system;
  • Fig. 7 is a diagram showing an example of an image being displayed in a display system consistent with the present invention;
  • Figs. 8A and 8B are diagrams showing examples of pixel matrices having a number of different pixel arrangements consistent with the present invention;
  • Fig. 9 is a graphical representation of the display results of the relationship between blue normalized luminance and gray scales (Gamma Curve) at different viewing angles in one embodiment of a normally black LCD;
  • Fig. 10 is a diagram that illustrates an example of a conventional LCD display system having an application specific integrated circuit ("ASIC"); and
  • Fig. 11 is a diagram that illustrates an example of an LCD display system having an application specific integrated circuit ("ASIC") with color shifting compensation for front and side viewing according to one embodiment of the present invention.
  • DESCRIPTION OF THE EMBODIMENTS
  • Reference will now be made in detail to present embodiments of the invention, 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.
  • When the original red, green and blue colors have different grayscales in an LCD panel, the respective levels of color shifting will be different. Consistent with the present invention, in order to reduce color shifting, the color displayed by a pixel in an image frame is divided into two colors having less color shifting being displayed in two subframes, or two colors having less color shifting being displayed in two adjacent pixels.
  • Fig. 2 is a diagram that illustrates a coordinate system representing an end user viewing an LCD 200 at a viewing point Q. Figs. 3A, 3B and 3C are diagrams respectively illustrating the relationship between normalized transmittance (or luminance) and gray scales for different viewing angles for red, green and blue light, where gray scales for the pixels range from 0 to 255. The normalized transmittance (or luminance) value for a gray scale is the luminance of a front view corresponding to that gray scale divided by the maximum luminance for the front view, e.g., a gray scale value of 255 for a normally black display. The normalized transmittance (luminance) value for a gray scale of a side view is the luminance of the side view corresponding to that gray scale divided by the maximum luminance for the side view. In general, the front view of the maximum luminance is different from the side view of the maximum luminance. In view of the color shifting, it is necessary to compare the respective normalized luminance (or transmittance) values of any two viewing angles. Referring to Fig. 2, an angle  is defined between the line from the center of LCD 200 to the viewing point Q and the Z axis, and an angle  is defined between the line projected from point Q onto LCD 200 and the X axis. Figs. 3A, 3B and 3C illustrate the respective relationships between normalized transmittance (luminance) and gray scales at angle (, )=(0°, 0°), (0°, 45°) and (0°, 60°). When (, ) = (0°, 0°), LCD 200 is being directly viewed from the front. When (, ) = (0°, 45°) or (0°, 60°), LCD 200 is being viewed from the side at 45- and 60-degree angles, respectively. Line a in Figs. 3A, 3B and 3C represents the front view (=0°, =0°) of the relationship between the red, green, blue normalized luminance, respectively, and gray scales. Line b in Figs. 3A, 3B and 3C represents the side view (=0°, =45°) of the relationship between the red, green, blue normalized luminance, respectively, and gray scales. Line c in Figs. 3A, 3B and 3C represents the side view (=0°, =60°) of the relationship between the red, green, blue normalized luminance, respectively, and gray scales. Line d in Figs. 3A, 3B and 3C represents the difference between the front view (=0°, =0°) and the side view (=0°, =60°) of the red, green and blue normalized luminance, respectively, in the relationship between such difference and gray scales.
  • As shown in Figs. 3A, 3B and 3C, frontal and side viewing of light having different colors at the same gray scale will have different normalized luminance values, resulting in color shifting. The difference between normalized luminance values for the front and side views is small (i.e., close to 0%) when the gray scale is close to 0 or 255. Consistent with the present invention, for an original gray scale at a value of 128, for example, an adjusted gray scale is determined so that the difference between normalized luminance values for the side and front views and normalized luminance values for the original gray scale of 128 is small. Moreover, an end user, when viewing the LCD panel, will still enjoy generally the same brightness, notwithstanding the adjusted gray scales for minimizing color shifting with respect to the side and front views.
  • Fig. 4 illustrates an embodiment consistent with the present invention that employs adjusting the gray scale in the time domain and includes an LCD 400 display system with color shifting compensation for front and side viewing. LCD 400 comprises a plurality of pixels (a pixel being represented by, e.g., P(i, j), i and j being positive integers), data drivers 402, scan drivers 404, and a controller 406. Controller 406 further comprises an adjusted gray scale generator 407. One image frame is displayed in the LCD for each frame period. A frame period is divided into n subframes SFP1 through SFPn, n being a positive integer. The original gray scales of pixels P(i, j) are GRO(i, j). A lookup table stored in adjusted gray scale generator 407 records all original gray scales (GR0) and at least one corresponding adjusted gray scale GR1 through GRn. Line d in Figs. 3A, 3B and 3C illustrates that Fig. 3C (the blue color) has the greatest difference between the front view and side view of normalized luminance. In view of this, the blue color may be adjusted first. Table 1 below shows an example of such a lookup table for the original and adjusted gray scales for blue color in a specific embodiment of a normally black, 20.1-inch, liquid crystal display ("LCD"). The "Gray" represents the original gray scales for blue color, and "LUT 1" and "LUT 2" represent the adjusted gray scales for blue color GR1 and GR2, respectively. The display results in such a normally black LCD for the blue color of the relationship between normalized luminance of blue and gray scales (Gamma Curve), which are shown in graphical form in Fig. 9. Line a of Fig. 9 represents the front view (=0°, =0°) of the relationship between the original normalized luminance and gray scales. Line b of Fig. 9 represents the 60° side view (=0°,  =60°) of the relationship between original normalized luminance of blue and gray scales. Line c of Fig. 9 represents the front view (=0°,  =0°) of the relationship between adjusted normalized luminance of blue (using adjusted gray scales such as those in Table 1) and gray scales. Line d of Fig. 9 represents the 60° side view (=0°, =60°) of the relationship between adjusted normalized luminance of blue (using adjusted gray scales such as those in Table 1 below) and gray scales.
    Gray LUT 1 LUT 2
    0 0 0
    1 5 0
    2 5 0
    3 5 0
    4 6 0
    5 33 0
    6 34 0
    7 54 0
    8 66 0
    9 84 0
    10 94 0
    11 112 0
    12 122 0
    13 133 0
    14 141 0
    15 147 0
    16 152 0
    17 156 0
    18 159 0
    19 162 0
    20 164 0
    21 166 0
    22 168 0
    23 169 0
    24 171 0
    25 172 0
    26 173 0
    27 175 0
    28 176 0
    29 177 0
    30 178 0
    31 179 0
    32 180 0
    33 181 0
    34 182 0
    35 182 0
    36 183 0
    37 184 0
    38 185 0
    39 186 0
    40 186 0
    41 187 0
    42 187 0
    43 188 0
    44 189 0
    45 189 0
    46 190 0
    47 191 0
    48 191 0
    49 192 0
    50 192 0
    51 193 0
    52 193 0
    53 194 0
    54 194 0
    55 195 0
    56 195 0
    57 196 0
    58 196 0
    59 197 0
    60 197 0
    61 197 0
    62 198 0
    63 198 0
    64 199 0
    65 199 0
    66 200 0
    67 200 0
    68 201 0
    69 201 0
    70 202 0
    71 202 0
    72 203 0
    73 203 0
    74 204 0
    75 204 0
    76 205 0
    77 205 0
    78 206 0
    79 206 0
    80 207 0
    81 207 0
    82 208 0
    83 208 0
    84 209 0
    85 209 0
    86 210 0
    87 210 0
    88 211 0
    89 211 0
    90 212 0
    91 212 0
    92 213 0
    93 213 0
    94 214 0
    95 214 0
    96 215 0
    97 215 0
    98 216 0
    99 216 0
    100 217 0
    101 217 0
    102 218 0
    103 218 0
    104 219 0
    105 219 0
    106 220 0
    107 220 0
    108 221 0
    109 221 0
    110 222 0
    111 222 0
    112 223 0
    113 223 0
    114 223 0
    115 224 0
    116 224 0
    117 224 0
    118 224 0
    119 225 0
    120 225 0
    121 225 0
    122 225 0
    123 226 0
    124 226 0
    125 226 0
    126 225 2
    127 225 2
    128 225 2
    129 225 3
    130 225 3
    131 225 3
    132 225 4
    133 225 4
    134 225 5
    135 225 5
    136 225 6
    137 225 6
    138 225 7
    139 225 7
    140 225 8
    141 225 8
    142 225 9
    143 225 9
    144 225 10
    145 225 10
    146 225 11
    147 225 12
    148 225 13
    149 225 13
    150 225 14
    151 225 15
    152 225 16
    153 225 17
    154 225 18
    155 225 19
    156 225 20
    157 225 21
    158 225 22
    159 225 23
    160 225 24
    161 225 26
    162 225 27
    163 225 28
    164 225 29
    165 225 30
    166 225 32
    167 225 33
    168 225 34
    169 225 36
    170 225 37
    171 225 39
    172 225 40
    173 225 42
    174 225 43
    175 225 45
    176 225 47
    177 225 48
    178 225 50
    179 225 52
    180 225 53
    181 225 55
    182 225 57
    183 225 58
    184 225 60
    185 225 62
    186 225 65
    187 225 70
    188 225 74
    189 225 79
    190 225 83
    191 225 88
    192 225 93
    193 225 97
    194 225 102
    195 225 107
    196 225 112
    197 225 116
    198 225 121
    199 225 126
    200 225 131
    201 225 135
    202 225 140
    203 225 144
    204 225 148
    205 225 152
    206 225 156
    207 225 160
    208 225 163
    209 225 167
    210 225 170
    211 225 174
    212 225 177
    213 225 180
    214 225 183
    215 225 187
    216 225 190
    217 225 193
    218 225 195
    219 225 198
    220 225 200
    221 225 203
    222 225 205
    223 225 208
    224 225 211
    225 225 214
    226 225 216
    227 225 219
    228 225 221
    229 225 224
    230 225 225
    231 226 226
    232 227 227
    233 227 227
    234 228 228
    235 229 229
    236 230 230
    237 231 231
    238 232 232
    239 233 233
    240 234 234
    241 235 235
    242 236 236
    243 237 237
    244 239 239
    245 240 240
    246 241 241
    247 242 242
    248 243 243
    249 244 244
    250 246 246
    251 247 247
    252 249 249
    253 251 251
    254 253 253
    255 255 255
  • From such a lookup table, generator 407 (shown in Fig. 4) generates n adjusted gray scales from original gray scales GR0(i, j) for pixel P(i, j), including GR1(i, j), GR2(i, j) ... GRn(i, j). The n adjusted gray scales are input into corresponding data drivers 402 sequentially and accordingly displayed in n subframes.
  • Referring back to Fig. 4, for n subframe periods, data drivers 402 drive pixels P(i, j) with n drive voltages corresponding to n adjusted gray scales. Original gray scales GR0(i, j) correspond to the original normalized luminance of front views ("L0(i, j)") and side views ("L0'(i, j)"). For each subframe period, adjusted normalized luminance for the front views and side views is determined from corresponding adjusted gray scales. For the adjusted gray scales GR1 through GRn stored in the lookup table corresponding to original gray scales GR0, the sum of the absolute value of the difference between the adjusted normalized luminance values for the front and side views should be less than the sum of the absolute value of the difference between the original normalized luminance values for the front and side views. Color shifting between the front and side views is advantageously minimized as a result. Moreover, all of the adjusted normalized luminance values for the front views are generally the same as the original normalized luminance values for the front views, thereby assuring similarity between the original frame and the adjusted frame.
  • Figs. 5A and 5B are graphical views comparing normalized transmittance values of pixels in a conventional display system and a system consistent with the present invention, respectively. Fig. 5A is a graphical view showing normalized transmittance values T(%) for pixels P(i, j) corresponding to original gray scales GR0 as the pixels are voltage driven, versus time, in a conventional display system. Fig. 5B is a graphical view showing the normalized transmittance values T(%) for pixels P(i, j) corresponding to adjusted gray scales GR1 through GRn as the pixels are voltage driven, versus time. A frame period ("FP") is divided into two subframe periods, namely SFP1 and SFP2. For SFP1, respective adjusted normalized luminance values L1(i, j) and L1'(i, j) for the front and side views, respectively, are determined from adjusted gray scales GR1(i, j). For SFP2, respective adjusted normalized luminance values L2(i, j) and L2'(i, j) for the front and side views, respectively, are determined from adjusted gray scales GR2(i, j). For SFP1 and SFP2,|L1(i, j)-L1'(i, j)|+|L2 (i, j)-L2'(i, j)| < |L0(i, j)-L0'(i, j)|.
  • Referring to Fig. 5A, drive voltages corresponding to original gray scales GR0(i, j) are used to drive pixels P(i, j) for a frame period in a conventional display system, where the functions of normalized transmittance values T0(t) and T0'(t) respectively correspond to front and side views of pixels P(i, j). Original normalized luminance values L0(i, j) for the front view correspond to the integrated value of T0(t) within frame period FP. Similarly, original normalized luminance values L0'(i, j) for the side view correspond to the integrated value of T0'(t) within frame period FP.
  • Referring to Fig. 5B, for subframe period SFP1, drive voltages corresponding to adjusted gray scales GR1(i, j) are used to drive pixels P(i, j), where T1(t) and T1'(t) respectively represent the time function of normalized transmittance values for front and side views of pixels P(i, j). For SFP2, drive voltages corresponding to adjusted gray scales GR2(i, j) are used to drive pixels P(i, j) where T2(t) and T2'(t) respectively represent the time function of normalized transmittance values for front and side views of pixels P(i, j). Adjusted normalized luminance values L1 (i, j) for the front views correspond to the integrated value of T1(t) within subframe period SFP1 when drive voltages corresponding to adjusted gray scales GR1(i, j) are used to drive pixels P(i, j). Adjusted normalized luminance values L1'(i, j) for the side view correspond to the integrated value of T1'(t) within subframe period SFP1 when drive voltages corresponding to adjusted gray scales GR1(i, j) are used to drive pixels P(i, j). Adjusted normalized luminance values L2(i, j) for the front view correspond to the integrated value of T2(t) within subframe period SFP2 when drive voltages corresponding to adjusted gray scales GR2(i, j) are used to drive pixels P(i, j). Adjusted normalized luminance values L2'(i, j) for the side view correspond to the integrated value of T2'(t) within subframe period SFP2 when drive voltages corresponding to adjusted gray scales GR2(i, j) are used to drive pixels P(i, j).
  • For adjusted gray scales GR1(i, j) and GR2(i, j), L 1(i, j)-L1'(i, j)|+|L2(i, j)-L2'(i, j)| < |L0(i, j)-L0'(i, j)|. When an end user views pixels P(i, j), the cumulative effect of differences between normalized luminance values for the front and side views corresponding to gray scales GR1(i, j) in SFP1 and normalized luminance values for the front and side views corresponding to gray scales GR2(i, j) in SFP2 is less, compared with the difference between normalized luminance values for the front and side views corresponding to gray scales GRO(i, j) in a frame period FP in a conventional system. Color shifting for pixels P(i,.j) is thus advantageously minimized consistent with the present invention.
  • In addition, consistent with the present invention, adjusted gray scales GR1(i, j) and GR2(i, j) corresponding to the sum of normalized luminance values L1(i, j) and L2(i, j) for the front views are generally the same as normalized original luminance values L0(i, j) for the front views. When an end user views pixels P(i, j), the luminance for the pixels is attributed to the cumulative effect of luminance values for adjusted gray scales GR1 (i, j) and GR2(i, j) respectively corresponding to subframe periods SFP1 and SFP2, which approximates the luminance of original gray scales GR0 corresponding to pixels within a frame period FP in a conventional display system.
  • Furthermore, in one aspect, each of SFP1 and SFP2 is advantageously one half of frame period FP. In a further aspect, original gray scales GR0(i, j) are advantageously between adjusted gray scales GR1(i, j) and GR2(i, j). In another aspect, adjusted gray scales GR1(i, j) are greater than GR2(i, j). For example, when the original gray scale for blue pixels P(i, j) is 128, adjusted gray scale GR1(i, j) can be 190, where GR2(i, j) is 0, assuming SFP1 = SFP2 = (1/2) FP. In view of Fig. 5B, once original gray scale 128 is adjusted to gray scale 190 and 0 respectively corresponding to SFP1 and SFP2, the absolute value of the difference between normalized luminance values for the front and side (at 60 degrees) views will be less than that of original gray scale 128. Thus, consistent with the present invention, differences in pixel luminance for the front and side views are advantageously less than those in a conventional display system, thereby minimizing the effect of color shifting.
  • The absolute value of the difference of the normalized luminance value between the front and side (from 60 degrees) views for gray scale 0 is very small, which is well suited to serve as GR2(i, j). Image display is properly ascertained by dynamically and continuously adjusting GR1(i, j) and GR2(i, j) within a frame period FP to achieve optimal luminance. For example, when the original gray scale is 128, GR1(i, j) and GR2(i, j) can be (190, 0) or (0, 190), respectively.
  • According to an embodiment of the lookup table, original gray scales GR0(i, j) are fixed and corresponding normalized luminance values L0(i, j) are measured. In one aspect, the original frame period is divided into two equivalent subframe periods. Since the change between front and side views for gray scale 0 is the smallest, and for reducing response time for driving liquid crystal elements, gray scale 0 is selected to be GR2(i, j). Since the characteristics for driving liquid crystal elements are not rectangular waves, adjustment is needed for GR1(i, j) and GR2(i, j) so that the sum of normalized luminance values L1(i, j) and L2(i, j) is generally the same as original normalized luminance values L0(i, j). The cumulative effect of the differences between normalized luminance values for the front and side views corresponding to gray scales GR1(i, j) in SFP1 and normalized luminance values for the front and side views corresponding to gray scales GR2(i, j) in SFP2 is less, compared with the difference between normalized luminance values for the front and side views corresponding to gray scales GR0(i, j) in a frame period FP in a conventional system. GR1(i, j) and GR2(i, j) accordingly obtained for all gray scales are then used to form the lookup table.
  • A further embodiment consistent with the present invention is implemented in the space domain for changing the gray scales. Color shifting with respect to the front and side views is compensated by displaying an image within a single frame period ("FP"). In one aspect, the display system includes a liquid crystal display ("LCD") further comprising a display panel, a plurality of data drivers, a plurality of scan drivers and a controller. The panel further comprises a plurality of pixels, and the controller further includes an adjusted gray scale generator. For two pixels Pa and Pb, the adjusted gray scale generator generates adjusted gray scales GRa1 and GRb1 for original gray scales GRa0 and GRb0 for the pixels Pa and Pb, respectively. GRa0 and GRb0 respectively correspond to the original normalized luminance values for the front and side views (La and La'), and the original normalized luminance values for the front and side views (Lb and Lb').
  • Within the frame period FP, data drivers respectively drive the two pixels Pa and Pb with first and second drive voltages corresponding to adjusted gray scales GRa1 and GRb1. As pixel Pa is driven with the first drive voltage, Pa includes adjusted normalized luminance values Lc and Lc' for the front and side views, respectively. As pixel Pb is driven with the second drive voltage, Pb includes adjusted normalized luminance values Ld and Ld' for the front and side views, respectively. For pixels Pa and Pb, |Lc - Lc'| + |Ld - Ld'| < |La - La'| + |Lb - Lb'|.
  • In one aspect, the adjusted gray scale generator comprises a lookup table, from which adjusted gray scales GRa1 and GRb1 are generated. The lookup table records original gray scales GRa0 and GRb0, and corresponding adjusted gray scales GRa1 and GRb1.
  • In one aspect, pixels Pa and Pb are adjacent to each other and have the same color. Original gray scales GRa0 and GRb0 are between adjusted gray scales GRa1 and GRb1. Adjusted normalized luminance values for the front and side views (Lc and Ld, respectively) are generally the same as the sum of original normalized luminance values for the front and side views La and Lb.
  • Figs. 6A and 68 are diagrams showing examples of two adjacent images M and M+1 in a conventional display system. Fig. 7 is a diagram showing an example of an image being displayed in a display system consistent with the present invention. Red, green and blue pixels are respectively represented by letters R, G and B. Original gray scales for adjacent pixels are generally close, e.g., blue pixels B11 and B21 having the same original gray scale at 128. Adjusted gray scales GRa1 at 174 and GRb1 at 0 are selected when blue pixels B11 and B21 have the same original gray scale 128. Thus, as shown in Fig. 7, gray scales for blue pixels B11 and B21 are 174 and 0, respectively, consistent with the present invention. For the next image being displayed, gray scales for B11 and B21 are 0 and 174, respectively. According to the embodiment shown in Fig. 7, pixels having different colors have relatively large gaps therebetween.
  • Consistent with the present invention, pixel matrices can have a number of different pixel arrangements. In one aspect, one embodiment of the present invention provides a display device comprising a plurality of pixels in rows and columns having a first color, a second color and a third color, wherein two adjacent pixels in one of the rows have the same color. In another aspect, the present invention provides a display device comprising a plurality of pixels in rows and columns having a first color, a second color and a third color, wherein two adjacent pixels in one of the rows have the same color.
  • Figs. 8A and 8B are diagrams showing examples of pixel matrices having a number of different pixel arrangements. In addition to the coloring pixel arrangement shown in Fig. 7, two adjacent pixels in a row can also be the same color, as shown in Fig. 8A, such as a row of pixels GRBBRGGRB. There can be different arrangements of mixed order for every row, such as the order of the two adjacent rows GRBBRGGRB and BRGGRBBRG. For this particular embodiment, pixels G and B have the same adjacent pixel, so the gap between the two single-color pixels (G and B) is advantageously reduced. Moreover, the order of the pixels can be arranged so that two pixels are diagonally adjacent one another in an LCD panel, as shown in Fig. 8B. Referring to Fig. 8B, a pair of red pixels R and a pair of blue pixels B are horizontally arranged, whereas a pair of green pixels G is located above or below the pair of red pixels R and the pair of blue pixels B. Green pixels G is further located in a mixed manner below red pixels R and blue pixels B, so pixels of the same color are adjacent along the diagonal lines in the LCD panel. Gaps between the single-color pixels are advantageously reduced as a result, as shown in Figs. 8A and 8B, which is conducive to optimizing the resolution for the pixels.
  • Figs. 10 and 11 are diagrams illustrating examples of an LCD display system having an application specific integrated circuit ("ASIC"), respectively without color shifting compensation (Fig. 10), and with color shifting compensation (Fig. 11) for front and side viewing according to one embodiment of the present invention.
  • Referring to Fig. 10, an LCD panel 100 comprises 1024 red, green and blue ("RGB") data lines, namely, 1024 x 3 data lines, and 768 scan lines, similar to the LCD panel shown in Fig. 1. The data lines and scan lines are respectively driven by a plurality of data drivers 102 and scan drivers 104. A power supply 103 supplies power to data drivers 102 and scan drivers 104. An ASIC 101 includes timing controller 106 that outputs a data control signal to data drivers 102, which accordingly receive and process the pixel data from controller 106. After processing the received pixel data, each of data drivers 102 outputs corresponding voltages for driving 384 data lines in LCD panel 100. Scan drivers 104, at the control of a scan control signal from controller 106, respectively output scan signals and control 256 scan lines. After scanning all of the scan lines, all of the pixels have been driven for completing the display of an image frame.
  • Fig. 11 is a diagram that illustrates an example of an LCD display system having an application specific integrated circuit ("ASIC 411") with color shifting compensation for front and side viewing according to one embodiment of the present invention. Referring to Fig. 11, LCD 400 comprises a plurality of pixels (a pixel being represented by, e.g., P(i, j), i and j being positive integers), data drivers 402, scan drivers 404, and a timing controller 406, similar to the LCD panel shown in Fig. 4. One image is displayed in the LCD for each frame period. A frame period is divided into n subframes SFP1 through SFPn, n being a positive integer. The original gray scales of pixels P(i, j) are GR0(i, j). A lookup table LUT1 records the original gray scales (GR0) and the corresponding adjusted gray scales GR1. A lookup table LUT2 records the original gray scales (GR0) and corresponding adjusted gray scales GR2. A power supply 403 supplies power to data drivers 402 and scan drivers 404. Timing controller 406 in ASIC 401 outputs a data control signal to data drivers 402, which accordingly receive and process the pixel data from controller 406. ASIC 411 further includes a data selector 405, LUT 1 and LUT 2, an interface 408 provided between LUT 2 and a memory 409 (which is an EEPROM).
  • The above embodiments of display devices and methods consistent with the present invention for compensating color shifting between front and side views of images can advantageously minimize the effects of color shifting and optimize image quality of the display device. One embodiment is advantageously implemented in a multi-domain vertically aligned LCD. Furthermore, embodiments consistent with the present invention can be implemented in an LCD for all of its pixels, or specifically implemented to particular pixels, to reduce the adverse effects of color shifting.
  • Other embodiments of the present invention will be apparent to those skilled in the art from consideration of the specification and practice of the present invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present invention being indicated by the following claims.

Claims (21)

  1. A display device for generating luminance for a pixel element, the display device comprising:
    a circuit for generating an original signal corresponding to a first intensity value for the pixel element at a first frequency;
    a converter for converting the original signal into two correction signals corresponding to a second intensity value and a third intensity value, respectively, at double the first frequency, wherein the first intensity value is between the second and the third intensity values; and
    a memory for storing and outputting the two correction signals.
  2. The display device of claim 1 further comprising a lookup table for storing the first intensity value, the second intensity value, and the third intensity value.
  3. The display device of claim 1 or 2 further comprising:
    a plurality of data lines;
    a plurality of scan lines;
    a plurality of data drivers for driving the data lines; and
    a plurality of scan drivers for driving the scan lines.
  4. The display device of any of claims 1 to 3 wherein the original signal and the correction signals with respect to a front view of the display device are generally the same.
  5. A method for generating luminance for a pixel element on a display device, the method comprising:
    generating an original signal corresponding to a first intensity value for the pixel element at a first frequency;
    converting the original signal into two correction signals corresponding to a second intensity value and a third intensity value, respectively, at double the first frequency, wherein the first intensity value is between the second and the third intensity values; and
    sequentially outputting the two correction signals to the pixel element.
  6. The method of claim 5 further comprising:
    driving a plurality of data lines in the display device; and
    driving a plurality of scan lines in the display device.
  7. The method of claim 5 or 6 further comprising providing a lookup table for storing the first intensity value, the second intensity value, and the third intensity value.
  8. The method of any of claims 5 to 7 wherein the original signal and the correction signals with respect to a front view of the display device are generally the same.
  9. A display device comprising:
    a plurality of pairs of pixels in rows and columns, each pair having one of a first color, a second color and a third color;
       wherein two adjacent ones of the pixels in one of the rows have the same color.
  10. The display device of claim 9 further comprising:
    a circuit for generating an original signal corresponding to a first intensity value for the pair of pixels at a first frequency;
    a converter for converting the original signal into two adjusted signals corresponding to a second intensity value and a third intensity value, respectively, wherein the first intensity value is between the second and the third intensity values; and
    a memory for storing and outputting the two correction signals to the pairs of pixels.
  11. A display device comprising:
    a plurality of pixels in rows and columns, each having one of a first color, a second color and a third color;
    wherein two diagonally adjacent ones of the pixels have the same color.
  12. A method for driving a display comprising:
    driving a plurality of data lines in the display;
    measuring original luminance values corresponding to a plurality of pixels in the display;
    adjusting gray scales of a plurality of pixels in the display; and
    adjusting the original luminance values of the pixels according to the adjusted gray scales;
       wherein the original luminance values and the adjusted luminance values of the pixels when the display is viewed from a front view point are generally the same.
  13. The method of claim 12 wherein the gray scales of the pixels are between two of the adjusted gray scales corresponding to two subframe periods in a frame period.
  14. The method of claim 12 or 13 further comprising driving the data lines with a plurality of drive voltages corresponding to the adjusted gray scales.
  15. The method of any of claims 12 to 14 further comprising arranging one of the pixels having a same coloring along diagonal lines in the display.
  16. The method of any of claims 12 to 15 wherein adjusting gray scales further comprises continuously adjusting the gray scales.
  17. A system comprising:
    a display further comprising a plurality of pixels having corresponding original luminance values;
    a plurality of data lines in the display;
    a plurality of scan lines in the display;
    a plurality of data drivers for driving the data lines;
    a plurality of scan drivers for driving the scan lines; and
    an adjusted gray scale generator for adjusting gray scales of the pixels and outputting adjusted gray scales to the pixels for adjusting the original luminance values;
       wherein the original luminance values of the pixels are adjusted according to the adjusted gray scales.
  18. The system of claim 17 wherein the original luminance values and the adjusted luminance values of the pixels when the display is viewed from a front view point are generally the same.
  19. The system of claim 17 or 18 wherein the data drivers generate a plurality of drive voltages corresponding to the adjusted gray scales.
  20. The system of any of claims 17 to 19 further comprising a lookup table storing the original luminance values and the adjusted gray scales.
  21. The system of claim 17 to 20 wherein the gray scales are continuously and dynamically adjusted.
EP04019705A 2004-01-07 2004-08-19 Liquid crystal display driver for compensating viewing angle Ceased EP1553553A3 (en)

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US8508449B2 (en) 2008-12-18 2013-08-13 Sharp Corporation Adaptive image processing method and apparatus for reduced colour shift in LCDs
WO2016045251A1 (en) * 2014-09-26 2016-03-31 京东方科技集团股份有限公司 Image display method and display device
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WO2022213699A1 (en) * 2021-04-07 2022-10-13 深圳Tcl数字技术有限公司 Method and apparatus for displaying image, display device, and storage medium
CN114613314A (en) * 2022-05-10 2022-06-10 深圳市时代华影科技股份有限公司 Picture display control method, device, equipment and medium
WO2023217199A1 (en) * 2022-05-10 2023-11-16 深圳市时代华影科技股份有限公司 Picture display control method, apparatus, and device, and medium
CN115083365B (en) * 2022-07-07 2023-06-27 Tcl华星光电技术有限公司 Picture display method and picture display device

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