Increasing the number of colors output by an active liquid crystal display

• US 6,295,041 B1
• Filed: 03/05/1997
• Issued: 09/25/2001
• Est. Priority Date: 03/05/1997
• Status: Expired due to Term

• Current Assignee: ATI Technologies Incorporated (Advanced Micro Devices, Inc.)
• Original Assignee: ATI Technologies Incorporated (Advanced Micro Devices, Inc.)
• Inventors: Leung, Charles, Lee, Keith
• Primary Examiner(s): Saras, Steven
• Assistant Examiner(s): ENGLISH, ALECIA DIANE
• Application Number:
  US08/811,866
• Time in Patent Office: 1,665 Days
• Field of Search: 345/147, 345/148, 345/149, 345/88, 345/89, 345/199
• US Class Current: 345/89
• CPC Class Codes: G09G 2340/0428 Gradation resolution change
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/2051 with use of a spatial dither pattern
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A technique increases the number of colors output by an active color display by providing an increased number of grey levels for each pixel component. An M×N matrix pattern of pixel components is generated having a ratio of pixel components at a particular color level to pixel components at a different color level to achieve a particular grey level, where M and N are greater or equal to two. The M×N matrix pattern is repeated for X frames, and at least one pixel component is at the particular color level in each frame. At the end of the Nth frame, the matrix pattern from frame zero is repeated.

Claims

1. A method to reducing flicker while increasing number of colors output by an active color LCD display, the method comprising:

receiving data for a particular color component;

utilizing a first portion of the data for selecting one of a plurality of gray level pattern generators, where each of the plurality of gray level pattern generators includes;

a corresponding plurality of matrix patterns, where each matrix pattern of the corresponding plurality of matrix patterns is associated with a frame of a

set of frames and is a 3×

3 matrix, and each matrix pattern includes;

a first gray level indicator,

a second gray level indicator,

a plurality of rows and a plurality of columns, wherein each row and column of the plurality of rows and columns have the same number of first gray level indicators as each other row and column in the plurality of rows and the plurality of columns;

utilizing a second portion of the data and the corresponding plurality of matrix patterns to produce a color component display output for the set of frames;

wherein the plurality of gray level pattern generators further comprise a gray level 10 generator, a gray level 7 generator, and a gray level 4 generator.

2. An apparatus for increasing the number of colors output by an active color LCD display, comprising:

a frame buffer that stores color component data;

a set of generator circuits, the set consisting of a gray level 15 generator circuit, a gray level 10 generator circuit, a gray level 7 generator circuit, and a gray level 4 generator,

wherein each generator circuit of the set of generator circuits includes a plurality of matrix patterns, wherein each matrix pattern of the plurality of matrix patterns is associated with a corresponding frame of a set of frames, wherein a matrix pattern of the plurality of matrix patterns includes a first grey level indicator and a second grey level indicator, wherein the matrix pattern has a same number of pixels having the first gray level indicator in each column and each row of the matrix pattern as each other matrix pattern of the plurality of matrix patterns;

a selector circuit operably coupled to receive a first portion of the color component data and to select a generator circuit of the set of generator circuits based on the first portion, wherein the selector circuit receives, on a pixel-by-pixel and frame-by-frame basis, the first or second grey level indicator from the selected generator circuit; and

a subtract circuit operably coupled to receive the first or second grey level indicator from the selector circuit and to receive a second portion of the color component data from the frame buffer, wherein the subtract circuit passes, as a digital output signal, the second portion when the first grey level indicator is received for a particular pixel and alters the second portion by a given value when the second grey level indicator is received for the particular pixel.

3. The apparatus of claim 2, wherein each grey level generator circuit comprises a memory for storing M×

N matrix pattern data.