Regulating a light source using a light-to-frequency converter

• US 20050276033A1
• Filed: 05/25/2004
• Published: 12/15/2005
• Est. Priority Date: 05/25/2004
• Status: Active Grant

• Current Assignee: Document Security Systems, Inc.
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Lee, Joon Chok, Lim, Kevin Len Li, Jaffar, Rizal
• Granted Patent: US 7,262,560 B2
• Time in Patent Office: Days
• US Class Current: 362/85
• CPC Class Codes: H05B 39/042 by measuring the incident light
• CPC Class Codes: H05B 41/3922 and measurement of the incident light
• CPC Class Codes: H05B 45/22 using optical feedback

Abstract

An apparatus and method thereof for regulating a light source are described. The apparatus includes a light-to-frequency converter that converts light received from the light source into a signal having a corresponding frequency. A circuit coupled to the light-to-frequency converter uses the frequency to regulate light that is emitted from the light source.

Claims

1. An apparatus comprising:

a light source;

a light-to-frequency converter that converts light received from said light source into a signal having a corresponding frequency;

a circuit coupled to said light-to-frequency converter that uses said frequency to regulate light emitted from said light source.

2. The apparatus of claim 1 wherein said circuit regulates the brightness of said light.

3. The apparatus of claim 1 wherein said circuit controls a color produced by said light source.

4. The apparatus of claim 1 wherein said circuit comprises a frequency counter, said frequency counter for determining said frequency of said signal.

5. The apparatus of claim 4 wherein said circuit further comprises a frequency scaler coupled between said light-to-frequency converter and said frequency counter, said frequency scaler for adjusting said frequency of said signal to within a range of said frequency counter.

6. The apparatus of claim 1 wherein said circuit comprises a signal processor, said signal processor using said frequency of said signal to determine whether to adjust said light source.

7. The apparatus of claim 1 further comprising a pulse width modulator generator that drives said light source.

8. The apparatus of claim 1 wherein said light source is used to back-light a display.

9. A device used with a light source, said device comprising:

a light-to-frequency converter that generates a first signal at a frequency that corresponds to the output of said light source; and

circuitry coupled to said light-to-frequency converter and to said light source, said circuitry regulating said light source by adjusting a second signal that drives said light source, said second signal adjusted according to said frequency of said first signal.

10. The device of claim 9 wherein said second signal drives the brightness of light from said light source.

11. The device of claim 9 wherein said second signal controls the color of light produced by said light source.

12. The device of claim 9 further comprising a frequency counter coupled to said light-to-frequency converter, said frequency counter for determining said frequency of said first signal.

13. The device of claim 12 further comprising a frequency scaler coupled between said light-to-frequency converter and said frequency counter, said frequency scaler for adjusting said frequency of said first signal to within a range of said frequency counter.

14. The device of claim 9 further comprising a signal processor coupled to said light-to-frequency converter, said signal processor for adjusting said second signal according to said frequency of said first signal.

15. The device of claim 9 further comprising a pulse width modulator generator that receives said second signal and drives said light source.

16. A method of regulating a light source, said method comprising:

receiving light that is emitted from said light source;

converting said light into a first signal having a frequency corresponding to the output of said light source; and

regulating said light source by manipulating a second signal that drives said light source, said second signal adjusted according to said frequency of said first signal.

17. The method of claim 16 wherein said regulating comprises changing the brightness of said light.

18. The method of claim 16 wherein said regulating comprises controlling a color produced by said light source.

19. The method of claim 16 further comprising counting said frequency of said first signal.

20. The method of claim 19 further comprising adjusting said frequency of said first signal to within a range of a frequency counter.

21. The method of claim 16 further comprising processing said first signal to determine whether an adjustment to said second signal is needed.

22. The method of claim 16 further comprising:

determining the period of said first signal using said frequency of said first signal.