ADAPTIVE FEEDBACK CONTROL METHOD OF FSC DISPLAY

• US 20100214327A1
• Filed: 02/02/2010
• Published: 08/26/2010
• Est. Priority Date: 02/24/2009
• Status: Active Grant

• Current Assignee: Chunghwa Picture Tubes Limited
• Original Assignee: Chunghwa Picture Tubes Limited
• Inventors: Chien, Shih-Hsun, Chiou, Shian-Jun, Tai, Wen-Chih, Shieh, Han-Ping, Lin, Fang-Cheng, Chen, Chun-Ho, Huang, Yi-Pai
• Granted Patent: US 8,368,728 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

An adaptive feedback control method of a field sequential color display includes converting gray-scale values of a three primary color field of an input image into gray-scale values of a new three primary color field and a dominated color field (D-field); performing sampling; performing a pixel by pixel sum operation for each separated color through color gamut conversion to obtain a color difference sum; performing a feedback control at a bit precision to obtain a minimum color difference sum; and then performing a liquid crystal/backlight synchronization step of synchronizing a liquid crystal signal and a backlight gray-scale value of the input image; or dividing the input image into a plurality of blocks; performing feedback control operations; obtaining a minimum sum in each block to serve as an optical backlight value, thereby reducing a CBU phenomenon, and minimizing or controlling the generated CBUs to reduce the operation loads.

Claims

1. An adaptive feedback control method of a field sequential color (FSC) display, comprising:

a reset step, wherein gray-scale values of a three primary color field of an input image are converted into gray-scale values of a new three primary color field and a dominated color field (D-field);

a sampling step, wherein a pixel sampling is performed on a resolution of the input image in a sampling interval;

a feedback control step, wherein a pixel by pixel sum operation is performed for each separated color on a color break-up (CBU) color value and a color value of the input image in a Lu′

v′

color space to obtain a color difference sum, and a feedback control is performed at a bit precision on the color difference sum, thereby obtaining a minimum color difference sum; and

a liquid crystal/backlight synchronization step, wherein a liquid crystal signal (LC signal) and a backlight gray-scale value of the input image are synchronized according to the minimum color difference sum.

2. The adaptive feedback control method according to claim 1, wherein the sampling interval is a 2×

4 pixel by pixel interval.

3. The adaptive feedback control method according to claim 2, wherein the interval generates 8 groups of CBU color difference sums (CBU-Δ

E_sum).

4. The adaptive feedback control method according to claim 1, wherein the color difference sum Δ

E_sum is represented in the following equation;

5. The adaptive feedback control method according to claim 1, wherein the bit precision is a 3-bit precision.

6. The adaptive feedback control method according to claim 1, wherein new gray-scale values r′

, g′

, b′ and

d in the reset step are represented in the following equations;

7. An adaptive feedback control method of a field sequential color (FSC) display, comprising a color difference sum acquisition step and a signal synchronization step, wherein:

the color difference sum acquisition step comprises;

converting an image of a n^th frame into a Lu′

v′

color space;

sampling on 8 groups of 1-bit backlights and sub-images in a 2×

4 sampling interval to include a CBU image, and performing 8 groups of color break-up (CBU) color difference sum operations synchronously through comparing with an input image;

filtering the color difference sums and determining a bit number of a next frame; and

considering to be the minimum color difference sum of new 7 sets of 2-bit groups from each two adjacent 1-bit groups of color backlight having minimum a color difference sum respectively; and

the signal synchronization step comprises;

processing a liquid crystal signal (LC signal) of the input image by a frame buffer, so as to obtain a LC signal of a (n-1)^th frame;

processing a minimum CBU color difference sum of a color backlight by a backlight buffer (BL buffer), so as to obtain a backlight gray-scale value of the (n-1)^th frame; and

using a lookup table (LUT) to generate a new LC gray-scale value through using the synchronized LC signal and backlight gray-scale value of the (n-1)^th frame.

8. The adaptive feedback control method according to claim 7, wherein a filtering condition N for the color difference sums is listed as follows:

9. The adaptive feedback control method according to claim 7, wherein in the step of consider to be the minimum color difference sum of new 7 sets of 2-bit groups from each two adjacent 1-bit groups of color backlight having minimum a color difference sum respectively, all 8 groups of color backlights are processed by a BL buffer and then used in the step of performing a CBU color difference sum operation of 8 groups synchronously, and the buffer is a signal register used for performing synchronization between the LC signal and the backlight gray-scale value.

10. The adaptive feedback control method according to claim 7, wherein the color difference sum Δ

E_sum is represented in a following equation;

11. An adaptive feedback control method of a field sequential color (FSC) display, applicable to an original image of an input image divided into a plurality of blocks, comprising:

a sampling step, wherein the original image is sampled to obtain a sampling image with a resolution smaller than that of the original image;

a reset step, wherein liquid crystal signals of three primary color fields of the input image are converted into backlight signals corresponding to liquid crystal signals of new three primary color fields and a dominated color field (D-field),

a feedback operation step, further comprising;

a time delay step, wherein the liquid crystal signals of the new three primary color fields are delayed for different time intervals,

a subtract step, wherein the liquid crystal signals corresponding to the color fields are subtracted from each other, and absolute values of subtracting results are obtained, and

a sum-up step, wherein a sum-up operation is performed on each color field in the subtract step, so as to obtain sums of each block,

wherein the sampling step, the reset step, and the feedback operation step are performed from an initial block to a final block among the blocks, and a minimum sum is obtained from the sums calculated for each block to serve as a backlight signal of each block and is provided for operations of a next block.

12. The adaptive feedback control method according to claim 11, wherein new gray-scale values r′

, g′

, b′ and

d in the reset step are represented in following equations;

13. The adaptive feedback control method according to claim 11, wherein new gray-scale values r′

, g′

, b′ and

d in the reset step are represented in following equations;