Method of color image display for a field sequential liquid crystal display device

• US 20020057253A1
• Filed: 11/09/2001
• Published: 05/16/2002
• Est. Priority Date: 11/09/2000
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Philips LCD Company Limited (LG Display Co., Ltd.)
• Inventors: Hong, Hyung-Ki, Lim, Moo-Jong
• Granted Patent: US 7,053,880 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G09G 2300/0491 Use of a bi-refringent liquid crystal, optically controlled bi-refringence [OCB] with bend and splay states, or electrically controlled bi-refringence [ECB] for controlling the color
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607

Abstract

A field sequential liquid crystal display device comprises a liquid crystal panel having an upper substrate, a lower substrate and a liquid crystal layer disposed therebetween, a back light disposed under the liquid crystal panel for irradiating a light to the liquid crystal panel and having 3 different light sources Red, Green and Blue sequentially driven; and an image signal processor controlling a lighting speed of each of the light sources Red, Green and Blue.

A method of color image display for a field sequential liquid crystal display device including an image signal processor, comprises steps of dividing a frame into four sub-frames having a period of one-fourth of one frame period, driving each of light sources Red, Green and Blue sequentially at a first, a second and a third sub-frame, driving a light source combination with three or fewer colors of Red, Green and Blue at a fourth sub-frame, classifying each component R, G and B of a color image input signal using a gray level having 256 levels, deciding a maximum luminance value of the field sequential liquid crystal display device using the gray level, obtaining an average luminance value of each of component R, G and B from the image input signal, turning on one of light sources Red, Green and Blue having an average luminance value greater than the maximum luminance value at the fourth sub-frame, and converting the input luminance value of component R, G and B and an input luminance value of the fourth sub-frame using the image signal processor.

Additionally, the method provides a time interval between driving sections of a previous light source and a next light source.

Claims

1. A field sequential liquid crystal display device, comprising:

a liquid crystal panel having an upper substrate, a lower substrate and a liquid crystal layer therebetween;

a back light under the liquid crystal panel for irradiating light to the liquid crystal panel and having different light sources for each of the colors Red, Green and Blue; and

an image signal processor controlling a lighting speed of each of light sources Red, Green and Blue, whereby the light sources are sequentially driven.

2. The device according to claim 1, wherein the liquid crystal layer mode is Optical Compensated Birefringent (OCB) mode.

3. The device according to claim 1, wherein the liquid crystal layer mode is Ferroelectric Liquid Crystal (FLC) mode.

4. The device according to claim 1, wherein each of the light sources is disposed at a down edge of the liquid crystal panel.

5. The device according to claim 1, wherein each of the light sources is disposed directly under of the liquid crystal panel in a repeated sequence of Red, Green and Blue.

6. The device according to claim 1, wherein the back light further includes a fourth light source.

7. The device according to claim 6, wherein a color of the fourth light source is within a color range from Green to Blue.

8. A method of color image display for a field sequential liquid crystal display device including an image signal processor, comprising:

dividing a frame into four sub-frames, each sub-frame having a period of one-fourth of one frame period;

driving each of light sources Red, Green and Blue sequentially at a first, a second and a third sub-frame, and

driving a combination of the light sources the combination having up to three colors at a fourth sub-frame.

9. The method according to claim 8, wherein the combination of light sources turned on at the fourth sub-frame is one of combinations consisting of all off, R, G, B, G+B, R+B, R+G, and all on.

10. The method according to claim 8, wherein one frame period is {fraction (1/60)} second.

11. The method according to claim 10, wherein a lighting time of the light source at each sub-frame is shorter than {fraction (1/240)} second.

13. The method of claim 12 further comprising:

converting the input luminance value of component R, G and B and an input luminance value of the fourth sub-frame using the image signal processor.

14. The method according to claim 12, wherein a combination of light sources and R, G, and B turned on at the fourth sub-frame is one of combinations consisting of all off, R, G, B, G+B, R+B, R+G, and all on.

15. The method according to claim 12, wherein the light source which is to be turned on at the fourth sub-frame is decided on the basis of a maximum luminance value of R, G and B.

16. The method according to claim 12, wherein the frame period is {fraction (1/60)} second.

17. The method according to claim 13, wherein a lighting time of the light source at each sub-frame is less than {fraction (1/240)} second.

19. The method according to claim 18, wherein the time interval is formed from a second divided driving area.

20. The method according to claim 18, wherein if an Optically Compensated Birefringence (OCB) mode is selected for a liquid crystal, the time interval may be 0.5 msec˜

1 msec.

21. The method according to claim 18, wherein the number n of divided driving areas is dependent on a degree of a resolution of a liquid crystal display device and a response time of the liquid crystal.

22. The method according to claim 18, wherein a lighting time of a back light is dependent on a degree of resolution of the liquid crystal display device and a response time of the liquid crystal.

12. A method of color image display for a field sequential liquid crystal display device including an image signal processor, comprising:

dividing a frame having a frame period into four sub-frames having a period of one-fourth of one frame period;

driving each of light sources Red, Green and Blue sequentially at a first, a second and a third sub-frame, respectively;

driving a light source combination with a combination of colors Red, Green and Blue at a fourth sub-frame;

classifying a color image input signal into color components R, G and B using a gray level having 256 levels;

deciding a maximum luminance value of the field sequential liquid crystal display device using the gray level;

obtaining an average luminance value of each of the components R, G and B from the color image input signal; and

turning on light sources Red, Green and Blue corresponding to the one of the color components R, G and B having an average luminance value greater than the maximum luminance value at the fourth sub-frame.

18. A method of color image display for a field sequential liquid crystal display device including an image signal processor, comprises:

dividing a liquid crystal panel into n numbers of driving areas;

turning on each of light sources Red, Green and Blue sequentially for every divided driving area; and

providing a time interval between driving sections of a previous light source and a next light source.