COLOR MANAGEMENT FOR FIELD-SEQUENTIAL LCD DISPLAY

• US 20100207531A1
• Filed: 01/28/2010
• Published: 08/19/2010
• Est. Priority Date: 02/19/2009
• Status: Active Grant

• Current Assignee: Polaris PowerLED Technologies, LLC (Microchip Technology Incorporated)
• Original Assignee: Microsemi Corp. - Analog Mixed Signal Group, Ltd. (Microchip Technology Incorporated)
• Inventors: LANGER, Tamir, PEKER, Arkadiy, KORCHARZ, Dror
• Granted Patent: US 8,324,830 B2
• Time in Patent Office: Days
• US Class Current: 315/152
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 47/11 by determining the brightness or colour temperature of ambient light
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

A method of color control for a backlight utilizing colored light emitting diodes (LEDs), the method constituted of: providing a plurality of colored LED strings constituted of at least three different colors; lighting each of the plurality of colored LED strings to provide a backlight; providing a period wherein none of the colored LED strings are lit; obtaining during the provided period when none of the colored LED strings are lit, an indication of an ambient light; obtaining during the provided period when the colored LED strings are lit, an indication of the optical output of the colored LED strings; and controlling the lighting of the provided plurality of colored LED strings responsive to the received indication of ambient light and the received indication of the output of the colored LED strings. Preferably, the method is performed in cooperation with an on-board color sensor.

Claims

1. A color control system for a backlight utilizing colored light emitting diodes (LEDs), the color control system comprising:

a color controller;

an LED driver responsive to said color controller;

a plurality of colored LED strings constituted of at least three different colors responsive to said LED driver; and

a color sensor, exhibiting a tri-stimulus output, in optical communication with said plurality of colored LED strings, said color controller coupled to said tri-stimulus output of said color sensor,

wherein said color controller is operative to;

light each of said plurality of colored LED strings via said LED driver;

provide a period wherein none of said colored LED strings are lit;

receive from said color sensor, during said provided period when none of said colored LED strings are lit, an indication of an ambient light received at said color sensor;

receive from said color sensor, during said provided period when said colored LED strings are lit, an indication of the optical output of said colored LED strings; and

control said LED driver responsive to said received indication of ambient light and said received indication of the output of said colored LED strings.

2. A color control system according to claim 1, wherein said lighting of said plurality of colored LED strings and said received indication of the optical output of said colored LED strings is sequential.

3. A color control system according to claim 2, wherein said color controller is operative to control said LED driver responsive to said received indication of ambient light and said received indication of the output of said colored LED strings by compensating said received indication of the output of said colored LED strings by said received indication of ambient light.

4. A color control system according to claim 3, wherein said color controller is operative to control said LED driver responsive to said received indication of ambient light and said received indication of the output of said colored LED strings by further implementing a function of said received indication of ambient light on one of said compensated received indication and a target light value.

5. A color control system according to claim 1, wherein said color controller is operative to control said LED driver responsive to said received indication of ambient light and said received indication of the output of said colored LED strings by compensating said received indication of the output of said colored LED strings by said received indication of ambient light.

6. A color control system according to claim 1, wherein said color controller is operative to control said LED driver responsive to said received indication of ambient light and said received indication of the output of said colored LED strings by implementing a function of said received indication of ambient light on one of said received indication of the output of said colored LED strings and a target light value.

7. A color control system according to claim 1, wherein said control of said LED driver is by pulse width modulation.

8. A color control system according to claim 1, wherein said color controller comprises:

a compensation functionality operative to receive said indication of the optical output of said colored LED strings and said indication of ambient light and output an ambient light compensated indication of the optical output of said colored LED strings;

a source of target color and luminance information;

a difference generator functionality, a first input of said difference generator functionality coupled to the output of said source of target color and luminance information;

a feedback controller functionality coupled to the output of said difference generator; and

a calibration matrix functionality in communication with said compensation functionality and operative to convert said compensated indication of the optical output of said colored LED strings to a pre-determined color space consonant with said target color and luminance information received at said first input of said difference generator, the output of said calibration matrix functionality coupled to a second input of said difference generator.

9. A color control system according to claim 8, wherein said compensated indication comprises a gain function.

10. A color control system according to claim 1, wherein said color controller comprises:

a source of target color and luminance information;

a difference generator functionality, a first input of said difference generator functionality coupled to the output of said source of target color and luminance information;

a calibration matrix functionality operative to receive the output of said color sensor and convert said received indication of the optical output of said colored LED strings and said received indication of ambient light to a pre-determined color space consonant with said target color and luminance information received at said first input of said difference generator functionality;

a feedback controller coupled to the output of said difference generator functionality; and

a compensation unit functionality coupled to the output of said calibration matrix functionality and operative to receive said converted indication of the optical output of said colored LED strings and said converted indication of ambient light and output an ambient light compensated indication of the optical output of said colored LED strings.

11. A color control system according to claim 10, wherein said compensated indication comprises a gain function.

12. A method of color control for a backlight utilizing colored light emitting diodes (LEDs), the method comprising:

providing a plurality of colored LED strings constituted of at least three different colors;

lighting each of said plurality of colored LED strings to provide a backlight;

providing a period wherein none of said colored LED strings are lit;

obtaining during said provided period when none of said colored LED strings are lit, an indication of an ambient light;

obtaining during said provided period when said colored LED strings are lit, an indication of the optical output of said colored LED strings; and

controlling said lighting of said provided plurality of colored LED strings responsive to said received indication of ambient light and said received indication of the output of said colored LED strings.

13. A method according to claim 12, wherein said lighting of said plurality of colored LED strings is sequential, and wherein said obtained indication of the optical output of said colored LED strings is an indication of the optical output of each color of said colored LED strings.

14. A method according to claim 13, wherein said controlling said lighting responsive to said obtained indication of ambient light and said received indication of the output of said colored LED strings comprises compensating said obtained indication of the output of said colored LED strings by said obtained indication of ambient light.

15. A method according to claim 14, wherein said controlling said lighting responsive to said obtained indication of ambient light and said received indication of the output of said colored LED strings further comprises implementing a function of said obtained indication of ambient light on one of said compensated obtained indication and a target light value.

16. A method according to claim 12, wherein said controlling said lighting responsive to said obtained indication of ambient light and said received indication of the output of said colored LED strings comprises compensating said obtained indication of the output of said colored LED strings by said obtained indication of ambient light from.

17. A method according to claim 12, wherein said controlling said lighting responsive to said obtained indication of ambient light and said received indication of the output of said colored LED strings comprises implementing a function of said obtained indication of ambient light on one of said obtained indication of the output of said colored LED strings and a target light value.

18. A method according to claim 12, wherein said controlling comprises:

compensating said obtained indication of the optical output of said colored LED strings by said obtained indication of ambient light; and

converting said compensated indication of the optical output of said colored LED strings to a pre-determined color space consonant with target color and luminance information.

19. A method according to claim 18, further comprising adjusting said compensated obtained indication by a function of said obtained indication of ambient light.

20. A method according to claim 12, wherein said controlling comprises:

converting said obtained indication of the optical output of said colored LED strings to a pre-determined color space consonant with a target color and luminance information;

converting said obtained indication of ambient light to the pre-determined color space; and

compensating said converted obtained indication of the optical output of said colored LED strings by said converted obtained indication of ambient light.

21. A method according to claim 20, further comprising adjusting said compensated converted obtained indication by a function of said obtained indication of ambient light.