IP Library › Granted Patent US 7,141,779
Granted Patent B1
US 7,141,779 · App. 11/230,708 · Granted Nov 28, 2006

System and method for emitting and detecting light using light emitting diode

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Quick Facts
Patent No.
US 7,141,779
App. No.
11/230,708
Filed
Sep 19, 2005
Granted
Nov 28, 2006
Kind
B1
Examiner
LEE, JOHN R
Art Unit
2878
USPC
250/205
Abstract

A system and method for emitting and detecting light uses a light emitting device, e.g., a light emitting diode, to emit light and to detect incident light. As an example, the system and method may be used in a digital camera, a camera phone or an illuminated device, such as a liquid crystal display device.

Claims (36)

1. A system for emitting and detecting light comprising:

a light emitting device configured to emit light in response to a driving signal and to generate a photo-signal in response to incident light;

a signal generator configured to provide said driving signal to activate said light emitting device;

an amplifier configured to amplify said photo-signal from said light emitting device;

a first switch connected between said light emitting device and said signal generator, said first switch being configured to selectively connect said signal generator to said light emitting device to transmit said driving signal from said signal generator to said light emitting device; and

a second switch connected between said light emitting device and said amplifier, said second switch being configured to selectively connect said light emitting device to said amplifier to transmit said photo-signal from said light emitting device to said amplifier.

2. The system of claim 1 wherein said light emitting device includes a light emitting diode.

3. The system of claim 1 wherein said signal generator includes a current source configured to provide said driving signal in the form of an electrical current.

4. The system of claim 1 wherein said photo-signal is a photocurrent and wherein said amplifier is a current-to-voltage amplifier configured to produce an amplified voltage signal in response to said photocurrent.

5. The system of claim 1 wherein said first switch is also connected to electrical ground, said first switch being configured to selectively connect said light emitting device to one of said signal generator and said electrical ground.

6. The system of claim 1 further comprising a driver circuit connected to said signal generator.

7. The system of claim 6 wherein said second switch is also connected to said driver circuit, said second switch being configured to selectively connect said light emitting device to one of said amplifier and said driver circuit.

8. The system of claim 1 wherein said light emitting device, said signal generator, said amplifier, said first and second switches are included in a device consisting of a digital camera, a camera phone and an illuminated device.

9. A system for emitting and detecting light comprising:

a light emitting diode having an anode and a cathode, said light emitting diode being configured to emit light in response to a driving current and to generate a photocurrent in response to incident light;

a current source configured to provide said driving current to activate said light emitting diode;

an amplifier configured to amplify said photocurrent from said light emitting diode;

a first switch connected between said anode of said light emitting diode and said current source, said first switch being configured to selectively connect said current source to said anode of said light emitting diode to transmit said driving current from said current source to said light emitting diode; and

a second switch connected between said cathode of said light emitting diode and said amplifier, said second switch being configured to selectively connect said cathode of said light emitting diode to said amplifier to transmit said photocurrent from said light emitting diode to said amplifier.

10. The system of claim 9 wherein said amplifier is a current-to-voltage amplifier configured to produce an amplified voltage signal in response to said photocurrent.

11. The system of claim 9 wherein said first switch is also connected to electrical ground, said first switch being configured to selectively connect said anode of said light emitting diode to one of said current source and said electrical ground.

12. The system of claim 9 further comprising a driver circuit connected to said current source.

13. The system of claim 12 wherein said second switch is also connected to said driver circuit, said second switch being configured to selectively connect said cathode of said light emitting diode to one of said amplifier and said driver circuit.

14. The system of claim 9 wherein said light emitting diode, said current source, said amplifier, said first and second switches are included in a device consisting of a digital camera, a camera phone and an illuminated device.

15. A method for emitting and detecting light, said method comprising:

connecting a signal generator to a light emitting device, including disconnecting an amplifier from said light emitting device;

transmitting a driving signal from said signal generator to said light emitting device;

generating light at said light emitting device in response to said driving signal;

connecting said amplifier to said light emitting device, including disconnecting said signal generator from said light emitting device;

generating a photo-signal at said light emitting device in response to incident light; and

transmitting said photo-signal from said light emitting device to said amplifier to amplify said photo-signal.

16. The method of claim 15 wherein said light emitting device includes a light emitting diode.

17. The method of claim 15 wherein said connecting said signal generator to said light emitting device includes also connecting said light emitting device to a driver circuit, said driver circuit being connected to said signal generator.

18. The method of claim 15 wherein said connecting said amplifier to said light emitting device includes also connecting said light emitting device to electrical ground.

19. The method of claim 15 wherein said connecting said signal generator to said light emitting device includes controlling a first switch connected between said signal generator and said light emitting device to connect said signal generator to said light emitting device.

20. The method of claim 19 wherein said connecting said amplifier to said light emitting device includes controlling a second switch connected between said amplifier and said light emitting device to connect said amplifier to said light emitting device.