Liquid crystal display with modulated black point

• US 7,612,757 B2
• Filed: 10/15/2004
• Issued: 11/03/2009
• 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: Daly, Scott J., Feng, Xiao-fan
• Primary Examiner(s): Nguyen; Chanh
• Assistant Examiner(s): Snyder; Adam J
• Application Number:
  US10/966,308
• Publication Number:
  US 20050248593A1
• Time in Patent Office: 1,845 Days
• Field of Search: 345/46, 345 87-107, 349/61, 348/687
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/0238 Improving the black level
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• 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 2320/062 Adjustment of illumination source parameters
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2330/10 Dealing with defective pixels
• 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 backlit display with improved dynamic range. The disclosed display illuminates a pixel of the display at respective non-zero illumination levels during each of a first frame and a second frame and decreases the illumination level of the pixel during the interval between the first frame and the second frame.

Claims

1. A method for displaying an image on a liquid crystal display comprising:

(a) illuminating a first pixel at a first maximum non-zero illumination level during a first frame;

(b) illuminating said first pixel at a second maximum non-zero illumination level during a second frame, wherein said second frame is the next frame immediately following said first frame, wherein said second maximum illumination level is greater than said first maximum illumination level;

(c) wherein said first pixel is decreased in illumination to an intermediate level less than said first maximum illumination level prior to illuminating said first pixel at said second maximum illumination level during said second frame; and

(d) wherein the magnitude and duration of said second maximum non-zero illumination level are automatically calculated as a function of said intermediate level and a target image brightness for said next frame, wherein said function is (Target Brightness−

Intermediate level*(frame duration−

second maximum illumination level duration))/second maximum illumination level duration and wherein said target image brightness for said second frame is achieved and said duration is as small as can be achieved given the brightest value obtainable by said pixel.