Liquid crystal display with modulation for colored backlight

• US 8,400,396 B2
• Filed: 06/19/2009
• Issued: 03/19/2013
• Est. Priority Date: 05/04/2004
• 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, Daly, Scott J., Messing, Dean
• Primary Examiner(s): Snyder, Adam J
• Application Number:
  US12/456,601
• Publication Number:
  US 20090262067A1
• Time in Patent Office: 1,369 Days
• Field of Search: 345/102
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

A method of backlighting a liquid crystal display so as to improve the quality of the image displayed by the liquid crystal display. The method may vary the luminance of a light source illuminating a plurality of displayed pixels and vary the transmittance of a light valve of the display.

Claims

1. A method of illuminating a backlit display, said method comprising the step of varying the luminance of a light source illuminating a plurality of displayed pixels and varying the transmittance of first and second light valves of said display in a non-binary manner, wherein said light source is spatially displaced from said plurality of displayed pixels at a location at least partially directly beneath said plurality of pixels, wherein said light source includes a plurality of different colored light emitting elements, wherein each of said first and second light valves has a respective colored light emitting element substantially directly beneath it so as project light of a first non-white color through said first light valve and light of a second non-white color through said second light valve, and said step of varying the transmittance of said first and second light valves applies respective voltages to said first and second light valves to achieve respective target light outputs from said light valve, each voltage associated with a target code value, said voltages each calculated as a function of both the respectively associated said target code value and a wavelength of the light transmitted through the one of said first and second light valves driven by said voltage, such that different voltages are applied to said first and second light valve for the same target code value.

2. The method of claim 1 wherein said light emitting elements are light emitting diodes.

3. The method of claim 2 wherein said light emitting elements are red, green, and blue.

4. The method of claim 1 wherein some of said light emitting elements include a plurality of different colors and others of said light emitting elements include a substantially white light emitting element.

5. A method of illuminating a backlit display, said method comprising the step of varying the luminance of a light source illuminating a plurality of displayed pixels and varying the transmittance of a light valve of said display in a non-binary manner, wherein said light source is spatially displaced from said plurality of displayed pixels at a location at least partially directly beneath said plurality of pixels, and wherein said light source includes a plurality of different colored light emitting elements arranged in a multi-colored pattern that extends over a plurality of pixels of said display so as project light of a non-white color through said light valve, and wherein the signal to said light emitting diodes is sub-sampled in a manner to both maintain high resolution of spatially-varying luminance information and attenuate spatially-varying high frequency chromatic information of an image.

6. The method of claim 5 where said multi-colored pattern is a Bayer pattern.