Method and apparatus for pulsed L.E.D. illumination for a camera

• US 7,740,371 B1
• Filed: 07/01/2008
• Issued: 06/22/2010
• Est. Priority Date: 03/19/1998
• Status: Expired due to Fees

• Current Assignee: Lemaire Illumination Technologies LLC
• Original Assignee: Charles A. Lemaire
• Inventors: Lebens, Gary A., Bourn, Charles T., Lemaire, Charles A.
• Primary Examiner(s): Negron, Ismael
• Application Number:
  US12/166,315
• Time in Patent Office: 721 Days
• Field of Search: 362/157, 362/184, 362/205, 362/800, 362/802, 315/127
• US Class Current: 362/205
• CPC Class Codes: F21L 4/027 the light sources being a LED
• CPC Class Codes: F21Y 2101/00 Point-like light sources
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H04N 23/51 Housings
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/12 using optical feedback
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/32 Pulse-control circuits
• CPC Class Codes: H05B 45/397 Current mirror circuits
• CPC Class Codes: H05B 47/10 Controlling the light source
• 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: Y10S 362/80 Light emitting diode
• CPC Class Codes: Y10S 362/802 Position or condition responsive switch

Abstract

An illumination source for a camera includes one or more LEDs, and an electrical circuit that selectively applies power from the DC voltage source to the LEDs, wherein the illumination source is suitable for handheld portable operation. In some embodiments, the electrical circuit further includes a control circuit for driving the LEDs with electrical pulses at a frequency high enough that light produced has an appearance to a human user of being continuous rather than pulsed, the control circuit changing a pulse characteristic to adjust a proportion of light output having the first characteristic color spectrum output to that having the second characteristic color spectrum output. Some embodiments provide an illumination source including a housing including one or more LEDs; and a control circuit that selectively applies power from a source of electric power to the LEDs, thus controlling a light output color spectrum of the LEDs.

Claims

1. An electronic camera and LED-illumination apparatus, comprising:

a housing of such compact size and low weight as to be suitable for single-handed portable operation by a user, and configured to hold a battery;

an imaging device mounted to the housing, wherein the imaging device is configured to generate an electronic image signal based on light gathered during a time window;

at least one LED mounted to the housing; and

a control circuit having an electronic switch operatively coupled to alternately connect and disconnect electrical power from the battery to the control circuit, such that the control circuit selectively applies electrical power from the battery to the at least one LED in synchrony with the time window during which light is gathered, wherein the control circuit controls LED light output to obtain an accumulated light input characteristic to the imaging device as a voltage of the battery varies over a range that would otherwise vary the light input characteristic by adjusting a proportion of connect time to disconnect time of the electronic switch.

2. The apparatus of claim 1, wherein the control circuit selectively applies electrical power from the battery to the at least one LED without a series resistor between the battery and the at least one LED.

3. The apparatus of claim 1, wherein the battery provides a DC voltage source, and wherein the control circuit controls the light output of the at least one LED at a substantially constant average level by increasing a proportion of connect time of the connecting as the voltage of the DC voltage source decreases.

4. The apparatus of claim 1, wherein the battery provides a DC voltage source, and wherein the control circuit controls the light output intensity of the at least one LED as the voltage of the DC voltage source varies by increasing a connect time pulse width as the voltage of the DC voltage source decreases.

5. The apparatus of claim 1, wherein the battery provides a DC voltage source, and wherein the control circuit controls the light output intensity of the at least one LED as the voltage of the DC voltage source varies by increasing a pulse frequency as the voltage of the DC voltage source decreases.

6. The apparatus of claim 1, wherein the electronic camera includes a charge-coupled device (CCD), and wherein the control circuit generates a plurality of pulses for each CCD image frame of the CCD device.

7. The apparatus of claim 1, wherein the electronic camera includes a charge-coupled device (CCD), and wherein the control circuit generates one pulse for each CCD image frame of the CCD device.

8. The apparatus of claim 1, wherein the at least one LED includes at least one red LED, at least one green LED, and at least one blue LED, and wherein the control circuit controls at least a pulse characteristic to the at least one red LED, the at least one green LED, and the at least one blue LED, in order to change a proportion of red light output to green light output and blue light output.

9. An apparatus for providing general-purpose illumination of such compact size and low weight as to be suitable for single-handed portable operation by a user, comprising:

a housing configured to be held in a single hand;

at least one LED that emits light when driven by an electrical current, wherein the at least one LED is mounted to the housing;

a battery connection mounted to the housing for coupling electrical current from a battery;

an electronic camera mounted to the housing, wherein the camera is configured to generate an electronic image signal based on light gathered during a time window;

means for electronically switching to alternately connect and disconnect current in an electrical path between the battery and the at least one LED; and

means for selectively applying electrical current from the battery to the at least one LED synchronized with the time window, wherein the means for selectively applying electrical current controls LED light output to obtain an accumulated light input characteristic to the electronic camera as a voltage of the battery varies over a range that would otherwise vary the light input characteristic by adjusting a proportion of connect time to disconnect time of the electronic switch.

10. The apparatus of claim 9, wherein the means for selectively applying electrical current maintains an average predetermined light output level of the at least one LED by sensing a voltage of the battery and adjusting a pulse frequency to maintain the average light output at the predetermined level.

11. The apparatus of claim 9, wherein the means for selectively applying electrical current maintains an average predetermined light output level of the at least one LED by sensing a voltage of the battery and adjusting a pulse width to maintain the average light output at the predetermined level.

12. The apparatus of claim 9, wherein the means for selectively applying electrical current maintains an average predetermined light output level of the at least one LED by sensing a light output and adjusting a pulse frequency to maintain the average light output at the predetermined level.

13. The apparatus of claim 9, wherein the means for selectively applying electrical current maintains an average predetermined light output level of the at least one LED by sensing a light output and adjusting a pulse width to maintain the average light output at the predetermined level.

14. The apparatus of claim 9, wherein the electronic camera includes a charge-coupled device (CCD), and wherein the means for selectively applying electrical current generates a plurality of pulses for each CCD image frame of the CCD device.

15. The apparatus of claim 9, wherein the electronic camera includes a charge-coupled device (CCD), and wherein the means for selectively applying electrical current generates one pulse for each CCD image frame of the CCD device.

16. The apparatus of claim 9, wherein the at least one LED includes at least one LED having a first characteristic color spectrum output, at least one LED having a second characteristic color spectrum output, wherein the first characteristic color spectrum output different from the second characteristic color spectrum output, and wherein the means for electronically switching controls at least a pulse characteristic to the at least one LED having a first characteristic color spectrum output in order to change a proportion of light output having the first characteristic color spectrum output to that having the second characteristic color spectrum output.

17. A method of providing illumination for an electronic camera of such compact size and low weight as to be suitable for single-handed portable operation by a user, comprising:

providing at least one LED in a housing configured to be held in a single hand, wherein each of the at least one LED emits light when driven by an electrical current;

connecting a battery to the housing;

electronically switching to alternately connect and disconnect an electrical-current path between the battery and the at least one LED to control one or more pulses of electrical current to the at least one LED;

emitting light from the at least one LED based on the one or more pulses of electrical current to illuminate an object;

gathering light from the illuminated object during a time window and generating an electronic image signal of the object illuminated by the emitted light based on the light gathered during the time window;

synchronizing the emitting of light from the at least one LED with the time window for gathering light; and

controlling, across a battery-voltage range that would otherwise vary an intensity of LED light output, the electronic switching to generate an amount of light output from the at least one LED sufficient to provide a desired accumulation of the light gathered for the generating of the electronic image signal.

18. The method of claim 17, wherein the connecting of the battery includes receiving the battery into the housing.

19. The method of claim 17, wherein the connecting of the battery includes mounting the battery onto the housing.

20. The method of claim 17, wherein the controlling of the electronic switching includes varying a pulse width such that the pulse width increases as battery voltage decreases.

21. The method of claim 17, wherein the controlling of the electronic switching includes varying a pulse frequency such that the pulse frequency increases as battery voltage decreases.

22. The method of claim 17, wherein the controlling of the electronic switching includes maintaining an average predetermined light output level of the at least one LED by sensing a light output and adjusting a pulse width to the at least one LED, based on a voltage of the battery to produce the light output at the predetermined level.

23. The method of claim 17, wherein the controlling of the electronic switching includes measuring a color balance of the electronic image signal and controlling a color of the light output of the at least one LED to maintain the light output at a predetermined level based on the measuring of the color balance of the electronic image signal.

24. The method of claim 17, wherein the at least one LED includes at least one LED having a first characteristic color spectrum output, at least one LED having a second characteristic color spectrum output, wherein the first characteristic color spectrum output different from the second characteristic color spectrum output, and wherein the controlling of the electronic switching includes at least controlling a pulse characteristic to the at least one LED having a first characteristic color spectrum output in order to change a proportion of light output having the first characteristic color spectrum output to that having the second characteristic color spectrum output.