Field sequential color encoding for displays

• US 8,773,480 B2
• Filed: 02/21/2013
• Issued: 07/08/2014
• Est. Priority Date: 09/22/2008
• Status: Expired due to Fees

• Current Assignee: Rambus Delaware
• Original Assignee: Rambus Delaware LLC (Rambus Inc.)
• Inventors: Van Ostrand, Daniel K., King, Carey, Cox, Berry Tod
• Primary Examiner(s): Wu, Xiao
• Assistant Examiner(s): BUTTRAM, ALAN T
• Application Number:
  US13/772,457
• Publication Number:
  US 20130235273A1
• Time in Patent Office: 502 Days
• Field of Search: 345/88, 345/597, 345/600, 345/690, 348/578, 348/456, 348/671
• US Class Current: 345/691
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• 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 2320/0266 Reduction of sub-frame artefacts
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3433 using light modulating elements actuated by an electric field and being other than liquid crystal devices and electrochromic devices using liquid crystal devices G09G3/36; using electrochromic devices G09G3/38
• CPC Class Codes: H04N 9/3111 for displaying the colours sequentially, e.g. by using sequentially activated light sources sequential projection in colour photography G03B33/08
• CPC Class Codes: H04N 9/3123 using pulse width modulation
• CPC Class Codes: H04N 9/3197 using light modulating optical valves
• CPC Class Codes: H04N 9/68 for controlling the amplitude of colour signals, e.g. automatic chroma control circuits H04N9/71, H04N9/73 take precedence; camera processing pipelines for controlling the colour saturation of colour signals H04N23/86

Abstract

The optical performance is enhanced of display systems that use field sequential color and pulse width modulation to generate color and color gray scale values. Such enhancement may be achieved by various data encoding methods disclosed herein that may include temporal redistribution of bit values to mitigate color motional artifacts associated with field sequential color-based display systems, selective combination of intensity modulation, pulse width modulation, and/or the noncontiguous sequencing of primary colors. There is further an intelligent real-time dynamic manipulation of gray scale values in portions of an image that are computationally determined to be images of objects moving against a global background, so as to temporally front load or concentrate the bits comprising such moving objects and thereby further mitigate said motional artifacts using both actual and virtual aggregate pulse truncation across all primary colors being modulated.

Claims

1. A method comprising:

displaying a video image using field sequential color encoded in a plurality of video frames;

receiving the plurality of video frames for displaying a foreground object and a background image in the video image;

determining in the received plurality of video frames that the foreground object of a video image of at least one of the video frames is in motion relative to the background image of the video image;

modifying a gray scale of the at least one of the video frames associated with the foreground object that is in motion relative to the background image of the video image to reduce the number of gray scales defining the foreground object;

encoding the plurality of video frames including the modified video frame for image generation; and

displaying the encoded plurality of video frames, including the modified video frame.

2. A method for removing field sequential color artifacts that arise in a display system that temporally segregates color components of a video image and presents each frame of video information by rapid consecutive generation of each color component when the color components of the video image making up a composite frame of video information do not all reach a same region of an observer'"'"'s retina due to relative motion of the retina and the video image to be displayed, the method comprising:

receiving a video signal for displaying the video image comprising a foreground object and a background image, the video signal further comprising a plurality of video frames, each video frame comprising a plurality of bits representing a gray scale of one of a plurality of the color components used by the display system to display the video image;

determining that the foreground object is moving relative to the background image; and

modifying a video frame containing color gray scale information associated with display of the foreground object to reduce the number of gray scales defining the foreground object.

3. A display system comprising:

a display panel for displaying a video image using field sequential color encoded in a plurality of video frames;

a video cache for receiving the plurality of video frames for determining whether the foreground object is moving relative to the background image;

a motion analyzer processing the plurality of video frames for determining whether the foreground object is moving relative to the background image;

the motion analyzer determining the foreground object is moving relative to the background image and further comprising circuitry for modifying a gray scale of the foreground object of at least one of the plurality of video frames in response thereto to reduce the number of gray scales defining the foreground object in the at least one of the plurality of video frames;

an encoder for encoding the plurality of video frames including the modified video frame for image generation; and

displaying the encoded plurality of video frames, including the modified video frame.