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

• US 6,808,287 B2
• Filed: 11/18/2002
• Issued: 10/26/2004
• Est. Priority Date: 03/19/1998
• Status: Expired due to Term

• Current Assignee: Lemaire Illumination Technologies LLC
• Original Assignee: PPT Vision, Inc. (Datalogic S.p.A.)
• Inventors: Lebens, Gary A., Bourn, Charles T., Lemaire, Charles A.
• Primary Examiner(s): Husar, Stephen
• Assistant Examiner(s): Zeade, Bertrand
• Application Number:
  US10/299,609
• Publication Number:
  US 20030095406A1
• Time in Patent Office: 708 Days
• Field of Search: 362/184, 362/183, 362/159, 362/249, 362/157, 362/208, 362/800, 362/224, 362/307, 362/291, 362/312, 362/360, 362/362, 315/291, 315/207, 315/224
• US Class Current: 362/184
• CPC Class Codes: F21L 4/027 the light sources being a LED
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H04B 10/502 LED transmitters
• CPC Class Codes: H04B 10/564 Power control
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means
• 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 45/395 Linear regulators
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• 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

Improved method and apparatus for hand-held portable illumination. A flashlight and corresponding method are described. The flashlight includes a housing, a plurality of LEDs, and an electrical circuit that selectively applies power from the DC voltage source to the LED units, wherein the flashlight is suitable for handheld portable operation by a user. In one embodiment, the first electrical circuit further includes a control circuit for maintaining a predetermined light output level of the LED units as a charge on a battery varies. In another embodiment, the control circuit maintains an average predetermined light output level of the LED units as the charge on the battery cell varies by changing a pulse width or frequency as the charge on the battery cell varies to maintain a given average light output. Another aspect provides an illumination source that includes a light-emitting diode (LED) housing including one or more LEDs, and a control circuit that selectively applies power from a source of electric power to the LEDs, the control circuit substantially maintaining a light output characteristic of the LEDs as a voltage of the voltage source varies over a range that would otherwise vary the light output characteristic. Still another aspect provides an illumination source including a light-emitting diode (LED) housing including one or more LEDs; and a control circuit that selectively applies power from a source of electric power to the LEDs, thus maintaining or controlling a light output color spectrum of the LEDs.

Claims

1. A method of providing general-purpose illumination of such compact size and low weight as to be suitable for single-handed portable operation by a user, comprising the steps of:

(a) providing one or more first LED units that each emit light;

(b) selectively applying pulsed power from a DC voltage source to the LED units; and

(c) maintaining a predetermined light output level of the LED units as a charge on the DC voltage source varies by controlling the step (b).

2. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units as the charge on the battery cell varies by increasing a pulse width as the charge on the battery cell decreases.

3. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units as the charge on the battery cell varies by increasing a pulse energy as the charge on the battery cell decreases.

4. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units as the charge on the battery cell varies by increasing a pulse frequency as the charge on the battery cell decreases.

5. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units by sensing a battery voltage and adjusting a pulse width to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

6. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units by sensing a battery voltage and adjusting a pulse energy to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

7. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units by sensing a battery voltage and adjusting a pulse frequency to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

8. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units by sensing a light output and adjusting a pulse width to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

9. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units by sensing a light output and adjusting a pulse energy to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

10. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units by sensing a light output and adjusting a pulse frequency to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

11. A pulsed LED illumination source, comprising:

one or more LEDs; and

a control circuit that is operatively coupled to the one or more LEDs and that selectively applies power pulses from a DC voltage source to the LEDs, the control circuit substantially maintaining an average light output characteristic of the LEDs as a voltage of the voltage source varies over a range that would otherwise vary the light output characteristic by adjusting the pulses.

12. The illumination source of claim 11, wherein the light output characteristic that is maintained is light output intensity.

13. The illumination source of claim 12, wherein the control circuit maintains the light output intensity of the LED units as the voltage of the DC voltage source varies by increasing a pulse width as the voltage of the DC voltage source decreases.

14. The illumination source of claim 12, wherein the control circuit maintains the light output intensity of the LED units as the voltage of the DC voltage source varies by increasing a pulse energy as the voltage of the DC voltage source decreases.

15. The illumination source of claim 12, wherein the control circuit maintains the light output intensity of the LED units as the voltage of the DC voltage source varies by increasing a pulse frequency as the voltage of the DC voltage source decreases.

16. The illumination source of claim 12, wherein the control circuit maintains an average predetermined light output level of the LED units by sensing a voltage and adjusting a pulse width to maintain the average light output at the predetermined level.

17. The illumination source of claim 12, wherein the control circuit maintains an average predetermined light output level of the LED units by sensing a voltage and adjusting a pulse energy to maintain the average light output at the predetermined level.

18. The illumination source of claim 12, wherein the control circuit maintains an average predetermined light output level of the LED units by sensing a voltage and adjusting a pulse frequency to maintain the average light output at the predetermined level.

69. The illumination source of claim 11, wherein the light output characteristic that is maintained is light output color.

70. The illumination source of claim 12, wherein the control circuit maintains the light output color of the LED units as the voltage of the DC voltage source varies by increasing a pulse width as the voltage of the DC voltage source decreases.

71. The illumination source of claim 12, wherein the control circuit maintains the light output color of the LED units as the voltage of the DC voltage source varies by increasing a pulse energy as the voltage of the DC voltage source decreases.

72. The illumination source of claim 12, wherein the control circuit maintains the light output color of the LED units as the voltage of the DC voltage source varies by increasing a pulse frequency as the voltage of the DC voltage source decreases.

73. The illumination source of claim 12, wherein the control circuit maintains an average predetermined light output color of the LED units by sensing a voltage and adjusting a pulse width to maintain the average light output at the predetermined level.

74. The illumination source of claim 12, wherein the control circuit maintains an average predetermined light output color of the LED units by sensing a voltage and adjusting a pulse energy to maintain the average light output at the predetermined level.

75. The illumination source of claim 12, wherein the control circuit maintains an average predetermined light output color of the LED units by sensing a voltage and adjusting a pulse frequency to maintain the average light output at the predetermined level.

76. The illumination source of claim 12, wherein the light output color of the LEDs normally predominately is in the blue spectrum, and wherein the control circuit outputs to the LEDs pulses of sufficiently high current to blue-shift the output and sufficiently short duration to not destroy the LED in order to maintain a constant light intensity while shifting the color spectrum from blue to ultraviolet.

19. A battery-powered portable pulsed LED illumination source comprising:

one or more light-emitting devices (LEDs);

a switch; and

control means for maintaining a substantially constant perceived light output, the control means operatively coupled to a battery, the LEDs, and the switch,

wherein the control means drives the LEDs with electrical pulses at a frequency high enough that light produced by the LEDs has an appearance to a human user of being continuous rather than pulsed, and wherein the LEDs have proportion of on-time that increases as remaining battery power decreases.

20. The illumination source of claim 19, wherein the control means further comprise:

feedback means for controlling the pulses so that light intensity produced by the LEDs, as perceived by the human user, is substantially constant across a greater range of battery power than a corresponding range for which light intensity is equally constant without the feedback circuit.

21. The illumination source of claim 20, wherein the feedback means measures a battery voltage and the control means adjusts a pulse width based on the measured voltage.

22. The illumination source of claim 20, wherein the feedback means measures a battery voltage and the control means adjusts a pulse frequency based on the measured voltage.

23. The illumination source of claim 20, wherein the feedback means measures a light output of the LEDs and the control means adjusts a pulse width based on the measured light output.

24. The illumination source of claim 20, wherein the feedback means measures a light output of the LEDs and the control means adjusts a pulse frequency based on the measured light output.

25. The illumination source of claim 20, wherein the feedback means measures a light output of the LEDs and the control means adjusts both a pulse width and frequency based on the measured light output.

26. The illumination source of claim 20, wherein the feedback means measures a light output of the LEDs and the control means adjusts a pulse energy based on the measured light output.

27. The illumination source of claim 19, wherein the one or more LEDs include one or more LEDs having a first characteristic color spectrum output and one or more LEDs having a second characteristic color spectrum output, the first characteristic color spectrum output different than the second characteristic color spectrum output, and the control means controls a pulse characteristic in order to control a proportion of light output having the first characteristic color spectrum output to that having the second characteristic color spectrum output.

28. The illumination source of claim 19, wherein the one or more LEDs include one or more LEDs having a characteristic color spectrum output that varies based on applied current, and the control circuit controls a pulse current in order to control the characteristic color spectrum output.

29. The illumination source of claim 19, wherein the control means further include:

means for changing a current and changing a frequency of pulses to control a color of light output of a first LED of the one or more LEDs while maintaining as substantially constant a perceived light intensity from the first LED.

30. The illumination source of claim 19, wherein the control means further include:

means for controlling a temperature of a first LED of the one or more LEDs to control a color of light output of the first LED while maintaining as substantially constant a perceived light intensity from the first LED.

31. The illumination source of claim 19, further comprising a flashlight housing that holds the one or more LEDs, the switch and the control means.

32. The illumination source of claim 19, wherein a frequency of pulses from the control means to the LEDs increases as battery voltage decreases.

33. The illumination source of claim 19, wherein a pulse width of pulses from the control means to the LEDs increases as battery voltage decreases.

34. The illumination source of claim 19, wherein the control means further include:

means for changing a current and changing a frequency of pulses to control a color of light output of a first LED of the one or more LEDs while maintaining as substantially constant a perceived light intensity from the first LED.

35. The illumination source of claim 19, wherein the one or more LEDs include one or more LEDs having a first characteristic color spectrum output and one or more LEDs having a second characteristic color spectrum output, the first characteristic color spectrum output different than the second characteristic color spectrum output, and the control means changes at least a pulse width characteristic of pulses driving the one or more LEDs having the first characteristic color spectrum output to change the perceived color output of the illumination source.

36. The illumination source of claim 35, wherein the control means changes at least a pulse width characteristic of pulses driving the one or more LEDs having the second characteristic color spectrum output to change the perceived color output of the illumination source.

37. The illumination source of claim 19, wherein the one or more LEDs include one or more LEDs that output a first color of light, one or more LEDs that output a second color of light, and one or more LEDs that output a third color of light, the first, second, and third colors being different from one another, and wherein the control means changes pulse width characteristics of pulses driving the one or more LEDs that output the first color, the one or more LEDs that output the second color, and the one or more LEDs that output the third color in order to change the perceived overall color output of the illumination source.

38. The illumination source of claim 19, wherein the switch is one of one or more switches connected to the control means by which a user can change a color of the light output from the one or more LEDs.

39. A battery-powered portable pulsed LED illumination source comprising:

one or more light-emitting devices (LEDs); and

control means for maintaining a substantially constant perceived light output, the control means configured to receive power from a battery, the control means operatively coupled to the one or more LEDs,

wherein the control means drives the LEDs with electrical pulses at a frequency high enough that light produced by the LEDs has an appearance to a human user of being continuous rather than pulsed, and wherein the LEDs have proportion of on-time that increases as remaining battery power decreases.

40. The illumination source of claim 39, wherein the control means further comprise:

feedback means for controlling the pulses so that light intensity produced by the LEDs, as perceived by the human user, is substantially constant across a greater range of battery power than a corresponding range for which light intensity is equally constant without the feedback circuit.

41. The illumination source of claim 40, wherein the feedback means measures a battery voltage and the control means adjusts a pulse width based on the measured voltage.

42. The illumination source of claim 40, wherein the feedback means measures a battery voltage and the control means adjusts a pulse frequency based on the measured voltage.

43. The illumination source of claim 40, wherein the feedback means measures a light output of the LEDs and the control means adjusts a pulse width based on the measured light output.

44. The illumination source of claim 40, wherein the feedback means measures a light output of the LEDs and the control means adjusts a pulse frequency based on the measured light output.

45. The illumination source of claim 40, wherein the feedback means measures a light output of the LEDs and the control means adjusts both a pulse width and frequency based on the measured light output.

46. The illumination source of claim 40, wherein the feedback means measures a light output of the LEDs and the control means adjusts a pulse energy based on the measured light output.

47. The illumination source of claim 39, wherein the one or more LEDs include one or more LEDs having a first characteristic color spectrum output and one or more LEDs having a second characteristic color spectrum output, the first characteristic color spectrum output different than the second characteristic color spectrum output, and the control means controls a pulse characteristic in order to control a proportion of light output having the first characteristic color spectrum output to that having the second characteristic color spectrum output.

48. The illumination source of claim 39, wherein the one or more LEDs include one or more LEDs having a characteristic color spectrum output that varies based on applied current, and the control circuit controls a pulse current in order to control the characteristic color spectrum output.

49. The illumination source of claim 39, wherein the control means further include:

means for changing a current and changing a frequency of pulses to control a color of light output of a first LED of the one or more LEDs while maintaining as substantially constant a perceived light intensity from the first LED.

50. The illumination source of claim 39, wherein the control means further include:

means for controlling a temperature of a first LED of the one or more LEDs to control a color of light output of the first LED while maintaining as substantially constant a perceived light intensity from the first LED.

51. The illumination source of claim 39, further comprising a flashlight housing that holds the one or more LEDs and the control means.

52. The illumination source of claim 39, wherein a frequency of pulses from the control means to the LEDs increases as battery voltage decreases.

53. The illumination source of claim 39, wherein a pulse width of pulses from the control means to the LEDs increases as battery voltage decreases.

54. The illumination source of claim 39, wherein the control means further include:

means for changing a current and changing a frequency of pulses to control a color of light output of a first LED of the one or more LEDs while maintaining as substantially constant a perceived light intensity from the first LED.

55. The illumination source of claim 39, wherein the one or more LEDs include one or more LEDs having a first characteristic color spectrum output and one or more LEDs having a second characteristic color spectrum output, the first characteristic color spectrum output different than the second characteristic color spectrum output, and the control means changes at least a pulse width characteristic of pulses driving the one or more LEDs having the first characteristic color spectrum output to change the perceived color output of the illumination source.

56. The illumination source of claim 55, wherein the control means changes at least a pulse width characteristic of pulses driving the one or more LEDs having the second characteristic color spectrum output to change the perceived color output of the illumination source.

57. The illumination source of claim 39, wherein the one or more LEDs include one or more LEDs that output a first color of light, one or more LEDs that output a second color of light, and one or more LEDs that output a third color of light, the first, second, and third colors being different from one another, and wherein the control means changes pulse width characteristics of pulses driving the one or more LEDs that output the first color, the one or more LEDs that output the second color, and the one or more LEDs that output the third color in order to change the perceived overall color output of the illumination source.

58. The illumination source of claim 39, further comprising:

switch means for providing a user-interface input to the control means.

59. The illumination source of claim 39, further comprising a flashlight housing that holds the one or more LEDs and the control means, and wherein the one or more LEDs include a first LED and a second LED, and wherein an optical axis of the first LED is substantially parallel to an optical axis of the second LED.

60. The illumination source of claim 59, and wherein the first LED has an optical spread angle that is substantially equal to an optical spread angle of the second LED.

61. The illumination source of claim 60, wherein the one or more LEDs include a third LED and a fourth LED, and wherein the third LED has an optical spread angle that is substantially equal to an optical spread angle of the fourth LED and different than the optical spread angle of the first and second LEDs.

62. The illumination source of claim 59, wherein the one or more LEDs include a third LED and a fourth LED, and wherein an optical axis of the third LED and an optical axis of the fourth LED converge forwardly of the housing.

63. The illumination source of claim 59, wherein the one or more LEDs include a third LED and a fourth LED, and wherein an optical axis of the third LED and an optical axis of the fourth LED diverge forwardly of the housing.

64. The illumination source of claim 39, further comprising a flashlight housing that holds the one or more LEDs and the control means, and wherein the one or more LEDs include a first LED and a second LED, and wherein an optical axis of the first LED and an optical axis of the second LED converge forwardly of the housing.

65. The illumination source of claim 39, further comprising a flashlight housing that holds the one or more LEDs and the control means, and wherein the one or more LEDs include a first LED and a second LED, and wherein an optical axis of the first LED and an optical axis of the second LED diverge forwardly of the housing.

66. The illumination source of claim 39, wherein the one or more LEDs include a first LED and a second LED, and wherein the first LED has an optical spread angle that is substantially equal to an optical spread angle of the second LED.

67. The illumination source of claim 39, wherein the one or more LEDs include a plurality of LEDs connected in a parallel-series configuration.

68. The illumination source of claim 39, wherein the control means further include:

means for changing a current and changing a pulse width to control a color of light output while maintaining as substantially constant a perceived light intensity from one of the one or more LEDs.