Method for overdriving a backlit display

• US 7,898,519 B2
• Filed: 09/06/2005
• Issued: 03/01/2011
• Est. Priority Date: 02/17/2005
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Feng, Xiao-Fan
• Primary Examiner(s): Lefkowitz; Sumati
• Assistant Examiner(s): HORNER, JONATHAN R
• Application Number:
  US11/219,888
• Publication Number:
  US 20060181503A1
• Time in Patent Office: 2,002 Days
• Field of Search: 345/690, 345/103, 345/89, 345/204
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2340/16 Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A backlight display has improved display characteristics. An image is displayed on the display which includes a liquid crystal material with a light valve. The display receives an image signal, modifies the light valve with an overdrive for a first region of the image based upon the timing of the illumination of the region, and modifies the light valve with an overdrive for a second region of the image based upon the timing of the illumination of the second region.

Claims

1. A method for displaying an image on a liquid crystal display including first and second light valves, each in a respectively different region of said display, said method comprising:

(a) receiving an image signal;

(b) recursively overdriving said first light valve based upon sequential values retrieved from a first look-up table; and

(c) recursively overdriving said second light valve based upon sequential values retrieved from a second look-up table;

where

(d) said first and second look-up tables are respectively produced by interpolation along one axis of a 3-dimensional table stored in memory accessible to said liquid crystal display, where said three-dimensional table provides respective values for the output response of said first and second light valves, respectively, as a function of a variable driving value for a current frame, a variable driving value for a previous frame, and a variable response time of said first and second light valves, each variable represented on an axis of said three-dimensional table.

2. The method of claim 1 wherein said interpolation is along an axis representing said variable response time of said first and second light valves.

3. The method of claim 1 wherein said first and second light valves are both illuminated by the same respective one of a plurality of backlight elements sequentially activated to be generally synchronous with a writing signal to said liquid crystal display.

4. The method of claim 1 wherein said display includes a plurality of backlights.

5. The method of claim 1 wherein said display is illuminated with a plurality of backlights in a temporally spaced manner during a frame.

6. A method for displaying an image on a display including a light valve comprising:

(a) receiving an image signal; and

(b) modifying a first pixel of said light valve with a first overdrive signal for said first pixel of said light valve changing from a first value to a second value, said first overdrive signal different than a second overdrive signal for a second pixel of said light valve changing from said first value to said second value, wherein said display includes a plurality of light emitting diodes forming a backlight providing light to said light valve, where said overdrive signal is based on a pre-determined dynamic gamma of said display representing the dynamic input-output relationship of said display as a function of a variable transition time between said first value and said second value, and wherein said dynamic gamma is represented in a three-dimensional lookup table stored in memory accessible to said liquid crystal display and used to calculate overdrive values, where said three-dimensional table provides respective values for the output response of said first and second light valves, respectively, as a function of a variable driving value for a current frame, a variable driving value for a previous frame, and a variable response time of said first and second light valves, each variable represented on an axis of said three-dimensional table.

7. A method for displaying an image on a liquid crystal display including first and second light valves, each in a respectively different region of said display, said method comprising:

(a) receiving an image signal;

(b) overdriving said first light valve based upon sequential values determined from a three-dimensional look-up table and stored in a first frame buffer, where said three-dimensional table provides respective values for the output response of said first and second light valves, respectively, as a function of a variable driving value for a current frame, a variable driving value for a previous frame, and a variable response time of said first and second light valves, each variable represented on an axis of said three-dimensional table;

(c) overdriving said second light valve based upon sequential values determined from said look-up table and stored in a second frame buffer; and

(d) simultaneously illuminating said first pixel and said second pixel while not illuminating at least one other pixel of said display;

where

(e) said values determined from said look-up table are automatically calculated based on an interpolation along an axis of said look-up table, said axis representing the temporal response of a backlight of said display measured at sequential intervals over a frame cycle of said display.