Brightness control for dynamic scanning backlight

• US 7,622,697 B2
• Filed: 06/10/2008
• Issued: 11/24/2009
• Est. Priority Date: 06/26/2007
• Status: Expired due to Fees

• Current Assignee: Polaris PowerLED Technologies, LLC (Microchip Technology Incorporated)
• Original Assignee: Microsemi Corp. - Analog Mixed Signal Group, Ltd. (Microchip Technology Incorporated)
• Inventors: Ferentz, Alon, Blaut, Roni, Korcharz, Dror, Peker, Arkadiy, Jacubovski, Migel
• Primary Examiner(s): Sohn; Seung C
• Application Number:
  US12/136,092
• Publication Number:
  US 20090001252A1
• Time in Patent Office: 532 Days
• Field of Search: 250/205, 250/201.1, 353/85, 353/88, 353/97, 353/121, 348/673, 348/687
• US Class Current: 250/205
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• 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 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources

Abstract

A method of controlling the luminance of a luminaire on an individual frame basis, without affecting a slow acting color loop controlling the color temperature of the luminaire, the method comprising: receiving a reference value representative of a target color; receiving a luminance signal defining the luminance of the luminaire per frame; adjusting a modulated signal driving the luminaire directly responsive to the received luminance signal, thereby controlling the luminance of the luminaire per frame; sampling the optical output of the luminaire per frame; comparing a value responsive to the sampled optical output with a value responsive to the received reference value to output a difference signal; and further adjusting the modulated signal driving the luminaire responsive to the compared value so as to reduce the difference signal.

Claims

1. A method of controlling the luminance of a luminaire on an individual frame basis, without affecting a color loop controlling the luminaire, the method comprising:

receiving a reference value defining a target correlated color temperature;

receiving a luminance setting defining a target luminance of the luminaire per frame;

adjusting, directly responsive to said received luminance setting, the modulation of a modulated signal driving the luminaire thereby controlling the luminance of the luminaire per frame; and

sampling the optical output of the luminaire at least once per frame.

2. A method according to claim 1, further comprising:

comparing a function of the sampled optical output with said received reference value to produce an error signal; and

adjusting said modulation of said modulated signal to reduce said error signal.

3. A method according to claim 1, further comprising:

scaling one of said received reference value and said sampled optical output by a value associated with said received luminance setting input signal;

comparing said scaled one of said received reference value and said sampled optical output with said non-scaled one of received reference value and said sampled optical output to produce an error signal; and

adjusting said modulation of said modulated signal to reduce said error signal.

4. A method according to claim 1, wherein the modulated signal is a pulse width modulated signal and wherein said adjusting the modulation of the modulated signal comprises adjusting a duty cycle of said pulse width modulated signal.

5. A method according to claim 3, wherein the luminaire comprises light emitting diodes of a plurality of colors, and wherein said adjusting the modulation of the modulated signal comprises adjusting a duty cycle of each of said light emitting diodes of said plurality of colors.

6. A method according to claim 1, wherein said sampling the optical output comprises converting said sampled output by a calibration matrix to be consonant with a colorimetric system of said received reference value.

7. A method according to claim 1, wherein the modulated signal is a pulse width modulated signal exhibiting a cycle, and wherein said sampling is per cycle of said pulse width modulated signal.

8. A backlight luminaire controller comprising:

a means for receiving a luminance setting signal defining a luminance of a backlight luminaire on an individual frame basis;

a means for receiving a reference value defining a target color temperature;

a feedback controller requiring a plurality of frames to converge;

a modulated signal generator immediately responsive to said received luminance setting signal and said feedback controller;

an optical sampler arranged to output a signal, on at least said individual frame basis, representative of the optical output of a backlight luminaire driven responsive to said modulated signal generator;

a scaler arranged to scale, by a scaling factor responsive to said received luminance setting signal, a first one of said received reference value and said output signal of said optical sampler to be consonant with a second one of said received reference value and said output signal of said optical sampler; and

a difference circuit, arranged to output a signal representative of the difference between the output of said scaler and the output of said second one of said received reference value and said output signal of said optical sampler,

said feedback controller responsive to said output signal of said difference circuit to output a signal operative to reduce said difference.

9. A backlight luminaire controller according to claim 8, wherein said modulated signal generator is a pulse width modulation generator, and wherein said feedback controller outputs a signal adjusting a duty cycle of said pulse width modulation generator.

10. A backlight luminaire controller according to claim 9, wherein said pulse width modulation generator exhibits a cycle and wherein said optical sampler is arranged to output a signal per cycle of said pulse width modulation generator.

11. A backlight luminaire controller according to claim 10, wherein said optical sampler comprises an integrator.

12. A backlight luminaire controller according to claim 9, wherein the backlight luminaire comprises light emitting diodes of a plurality of colors, and said pulse width modulation generator outputs a pulse width modulated signal exhibiting a duty cycle for each of said light emitting diodes of said plurality of colors.

13. A backlight luminaire controller according to claim 8, wherein said optical sampler comprises a calibration matrix operative to convert said sampled output to be consonant with a colorimetric system of said received reference value.

14. A method of controlling the luminance of a luminaire on an individual frame basis, without affecting a slow acting color loop controlling the color temperature of the luminaire, the method comprising:

receiving a reference value representative of a target color;

receiving a luminance signal defining the luminance of the luminaire per frame;

adjusting a modulated signal driving the luminaire directly responsive to said received luminance signal, thereby controlling the luminance of the luminaire per frame;

sampling the optical output of the luminaire per frame;

comparing a value responsive to said sampled optical output with a value responsive to said received reference value to output a difference signal; and

further adjusting said modulated signal driving the luminaire responsive to said compared value so as to reduce said difference signal.

15. A method according to claim 14, wherein said modulated signal is a pulse width modulated signal.

16. A method according to claim 15, wherein said adjusting the modulated signal comprises adjusting the duty cycle of said pulse width modulated signal.

17. A method according to claim 15, wherein the luminaire comprises light emitting diodes of a plurality of colors, and said adjusting the pulse width modulation signal comprises adjusting a duty cycle of each of said light emitting diodes of said plurality of colors.

18. A method according to claim 14, further comprising:

scaling one of said received reference value and said sampled optical value by a value associated with said received luminance signal, wherein said comparing a value comprises comparing said scaled one of said received reference value and said sampled optical value with said non-scaled one of received reference value and said sampled optical value.

19. A method according to claim 14, wherein said sampling the optical output comprises converting said sampled output by a calibration matrix to be consonant with a colorimetric system of said received reference value.

20. A method according to claim 14, wherein the modulated signal is a pulse width modulated signal exhibiting a cycle, and wherein said sampling is per cycle of said pulse width modulated signal.

21. A backlight luminaire controller comprising:

a feedback controller requiring a plurality of frames to converge;

a modulated signal generator immediately responsive to a received luminance setting signal and said feedback controller;

an optical sampler arranged to output a signal, on at least said individual frame basis, representative of the optical output of a backlight luminaire driven responsive to said modulated signal generator;

a scaler arranged to scale a first one of a received reference value and said output signal of said optical sampler to be consonant with a second one of said received reference value and said output signal of said optical sampler, said received reference value defining a target color temperature; and

a difference circuit, arranged to output a signal representative of the difference between the output of said scaler and the output of said second one of said received reference value and said output signal of said optical sampler,

said feedback controller responsive to said output signal of said difference circuit to output a signal operative to reduce said difference.