Field-sequential display system utilizing a backlit LCD pixel array and method for forming an image

• US 5,337,068 A
• Filed: 02/01/1993
• Issued: 08/09/1994
• Est. Priority Date: 12/22/1989
• Status: Expired due to Fees

• Current Assignee: Iljin Diamond Co.,Ltd. (Iljin Holdings Company Limited)
• Original Assignee: David Sarnoff Research Center, Inc.
• Inventors: Stewart, Roger G., Roach, William R.
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): FATAHI YAR, MAHMOUD
• Application Number:
  US08/012,981
• Time in Patent Office: 554 Days
• Field of Search: 345/87, 345/88, 345/90, 345/92, 345/94, 345/102, 348/761, 348/766, 348/790, 348/792, 348/793
• US Class Current: 345/88
• CPC Class Codes: G02F 1/133622 Colour sequential illumination
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• 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 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: H04N 9/30 using solid-state colour display devices

Abstract

A back-lighted color LCD display is formed by placing a single matrix of liquid crystal devices (LCDs) over a bank of red, green and blue fluorescent lamps. The LCD matrix is operated to sequentially form separate red, green and blue images synchronous with the illumination of the respective red, green and blue lamps. The flashing of the sequential red, green and blue images is perceived as a color image. The images are scanned, one line at a time, onto the LCD matrix. The bank of fluorescent lamps includes several lamps of each color which are arranged in parallel with the lines of the LCD matrix. The different lamps of each color are activated in synchronism with the scanning of the LCD matrix. Each LCD in the matrix includes a rapidly varying liquid crystal material, sandwiched between conductive plates. The electric field between the conductive plates may be controlled by a polysilicon thin-film transistor.

Claims

1. Apparatus for generating a color image, comprising;

display panel means, including a matrix of light valves the light transmissive properties of which can be selectively controlled wherein, single-color images representing separate components of the color image are formed by sequentially activating successive lines of light valves in the matrix of light valves;

a plurality of single color light sources which are alternately strobed to directly emit light for transmission through the matrix of light valves, wherein each of said single color light sources may be selectively activated to emit light in at least first and second distinct spatial locations corresponding to respectively different lines of said light valves; and

means for activating, in synchronism, each of the single color light sources in spatial correspondence with the scanning of the lines of the light valve matrix to sequentially illuminate said first and second spatial locations with each one of said single color light sources at respectively different instants;

wherein;

each of the light valves in said matrix of light valves is a liquid crystal device, the light transmissive properties of which are externally controlled;

each of said plurality of single color light sources includes a plurality of individual single color light sources which my be independently activated; and

the individual single color light sources of each one of said plurality of single color light sources are spatially interleaved with the individual single color light sources of the other ones of said plurality of single color light sources.

2. The apparatus of claim 1 wherein each of said individual single color light sources includes a fluorescent lamp which has a hollow translucent form having a long dimension and a short dimension, said form being coated with a fluorescent material which emits light of said color.

3. The apparatus of claim 2 wherein each of said fluorescent lamps is coated with a fluorescent material except for a stripe parallel to the long dimension which is not coated.

4. The apparatus of claim 1 wherein,

the color image is updated at a frame rate of not less than 50 Hz;

and

each of said liquid crystal devices includes a twisted nematic liquid crystal material sandwiched between first and second control electrodes which are separated by a distance of less than four micrometers.

5. The apparatus of claim 1 wherein the light transmissive properties of each of the light valves is controlled by an associated thin-film transistor.

6. Apparatus for generating a color image, comprising:

display panel means, including a matrix of light valves the light transmissive properties of which can be individually controlled, wherein, single-color images representing separate components of the color image are formed by activating the light valves in the matrix of light valves in a predetermined sequence; and

a plurality of single color light sources each including a plurality of separately operable light sources which directly emit light of a single color wherein the separately operable light sources of said plurality of single color light sources are interleaved; and

means for sequentially and selectively strobing each of said plurality of separately operable light sources of each of said plurality of single color light sources in synchronism with the formation of each respective single-color image on said matrix of light valves to provide light for transmission through the matrix of light valves.

7. The apparatus of claim 6 wherein:

the light valves in said matrix of light valves are arranged in rows and columns and said single color images are formed by activating successive rows of light valves in said matrix; and

said apparatus further comprises means for sequentially activating successive ones of said separately operable light sources of each of said plurality of single color light sources in synchronism with the activation of successive rows of light valves in said matrix.

8. The apparatus of claim 7 wherein each of said separately operable light sources of each of the single color light sources includes a fluorescent lamp which has a hollow translucent form having a long dimension and a short dimension, said form being coated with a fluorescent material which emits light of said single color.

9. The apparatus of claim 8 wherein each of said fluorescent lamps is coated with a fluorescent material except for a stripe parallel to the long dimension which is not coated.

10. The apparatus of claim 6 wherein:

the color image is updated at a frame rate of not less than 50 Hz;

each of the light valves in said matrix of light valves is a liquid crystal device, the light transmissive properties of which are externally controlled; and

each of said liquid crystal devices includes a twisted nematic liquid crystal material sandwiched between first and second control electrodes which are separated by a distance of less than four micrometers.

11. The apparatus of claim 10 wherein the light transmissive properties of each of the light valves is controlled by an associated thin-film transistor.

12. Apparatus for generating a color image, comprising:

an image forming region comprising a matrix of liquid crystal light valves the light transmissive properties of which can be individually controlled wherein, single-color images representing separate components of the color image are formed by sequentially activating successive lines of light valves in the matrix of light valves;

first backlighting means including at least first and second light sources which may be sequentially and selectively activated to directly emit light of a first color to illuminate respective first and second distinct spatial locations corresponding to respectively different lines of said light valves synchronism with the sequential activation of the lines of light valves; and

second backlighting means including at least first and second further light sources, interleaved with the first and second light sources, said first and second further light sources being sequentially and selectively activated to directly emit light of a second color, substantially exclusive of said first color, to illuminate respective ones of said first and second distinct spatial locations in synchronism with the sequential activation of the lines of light valves;

wherein, the first light source illuminates the first spatial location at the same time that the second further light source illuminates the second spatial location.

13. The apparatus of claim 12 wherein:

the light valves in said matrix of light valves are arranged in rows and columns and said images are formed by activating successive rows of light valves in said matrix.

14. Apparatus for generating a color image, comprising;

a display panel including a matrix of light valves having transmissive properties, wherein each of the light valves in said matrix of light valves is a liquid crystal device, the light transmissive properties of which are externally controlled;

means for selectively controlling the light transmissive properties of the matrix of light valves in the display panel wherein, single-color images representing separate components of the color image are formed by sequentially activating successive lines of light valves in the matrix of light valves;

a plurality of single color light sources wherein, each of said plurality of single color light sources includes a plurality of individual colored light sources which may be independently activated; and

individual colored light sources of each one of said plurality of single color light sources are spatially interleaved with the individual colored light sources of the other ones of said plurality of single color light sources;

means for strobing the plurality of single color light sources to directly emit light for transmission through the matrix of light valves, wherein each of said single color light sources may be selectively activated to provide light in at least first and second distinct spatial locations corresponding to respectively different lines of said light valves; and

means for activating each of the individual single color light sources to emit light of the single color at said first and second distinct spatial locations at respectively different times, in spatial correspondence with the scanning of the lines of the light valve matrix.

15. The method of claim 14 wherein the plurality of colored light sources of each of the plurality of single color light sources are configured to be alternately strobed in synchronism with the formation of single-color images on said matrix of light valves.

16. The method of claim 14 wherein each of said plurality of single color light sources includes a plurality of separately operable monochrome light sources and the separately operable monochrome light sources of said plurality of single color light sources are interleaved to provide illumination for said matrix of light valves.