Method and apparatus for L.E.D. illumination

• US 6,305,818 B1
• Filed: 07/28/2000
• Issued: 10/23/2001
• 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: Lemaire, Charles A., Lebens, Gary A., Bourn, Charles T.
• Primary Examiner(s): O'Shea, Sandra
• Assistant Examiner(s): Zeade, Bertrand
• Application Number:
  US09/627,268
• Time in Patent Office: 452 Days
• Field of Search: 362/184, 362/183, 362/157, 362/159, 362/208, 362/800, 362/249, 315/224, 315/307, 315/291, 315/312, 315/360, 315/362, 250/223.B, 356/239.4
• 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. An apparatus having an illumination source for providing light for a video camera, the apparatus comprising:

(a) a housing, the housing being suitable for at least one of receiving therein and mounting thereon a DC voltage source;

(b) a light-emitting diode (LED) housing connected the flashlight housing, the LED housing comprising a first plurality of LED units that each emit light and have a reflector for collimating the emitted light forwardly therefrom generally along an optical axis of one of the plurality of LED units; and

(c) a first electrical circuit that selectively applies pulsed power from the DC voltage source to the LED units;

wherein the illumination source is of such compact size and low weight as to be suitable for single-handed portable operation by a user.

2. The apparatus of claim 1, wherein the DC voltage source including at least one battery cell, and wherein the first electrical further includes a control circuit for maintaining a predetermined light output level of the LED units as a voltage on the battery cell varies.

3. The apparatus of claim 1, wherein the DC voltage source includes at least one battery cell, and wherein the first electrical circuit further includes a circuit for maintaining a predetermined light output level of the LED units based on a measured electrical current through the LED units.

4. The apparatus of claim 1, further comprising:

a video camera having a light-sensing pixel array, wherein the DC voltage source includes at least one battery cell, and wherein the first electrical circuit further includes a control circuit to provide light pulses from the LED units synchronized to a frame rate of the video camera.

5. The apparatus of claim 4, wherein the light pulses from the LED units are on substantially only when the light-sensing pixel array of the video camera is collecting light.

6. The apparatus of claim 1, wherein

the LED units are connected in a parallel-series configuration with at least two LED units coupled in parallel to one another and in series with at least one other LED unit;

and

the DC voltage source includes at least three battery cells connected in series.

7. The apparatus of claim 1, wherein the first electrical circuit maintains an average predetermined light output level of the LED units as the charge on the battery cell varies by increasing a pulse width to the LED units as the charge on the battery cell decreases.

8. The apparatus of claim 1, wherein the first electrical circuit maintains an average predetermined light output level of the LED units by measuring 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.

9. The apparatus of claim 1, wherein the first electrical circuit maintains an average predetermined light output level of the LED units by measuring an average light output and adjusting a pulse width to the LED units based on the measured light output to maintain the measured average light output at the predetermined level.

10. The apparatus of claim 1, further comprising:

a machine-vision system that includes;

a video camera having a light-sensing pixel array;

an image processor coupled to receive image data from the video camera; and

a feedback circuit coupled to the first electronic circuit that obtains a control parameter input, wherein the first electrical circuit further includes a control circuit to provide light pulses, that vary based on the control parameter input, from the LED units.

14. The method of claim 1, wherein the step of maintaining maintains a predetermined light output level of the LED units by measuring a light output and adjusting one or more pulse characteristics selected from the group consisting of

(1) a pulse width,

(2) a pulse energy, and

(3) a pulse frequency to the LED units based on the measured light output to maintain an average light output at the predetermined level.

11. A method of providing illumination for a video camera 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 and have a reflector for collimating the emitted light forwardly therefrom generally along an LED optical axis;

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

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

12. The method of claim 11, wherein the step of maintaining maintains an average predetermined light output level of the LED units as a voltage of the battery cell varies by increasing one or more pulse characteristics selected from the group consisting of

(1) a pulse width,

(2) a pulse energy, and

(3) a pulse frequency as the voltage of the battery cell decreases.

13. The method of claim 11, wherein the step of maintaining maintains a predetermined light output level of the LED units by measuring a battery voltage and adjusting one or more pulse characteristics selected from the group consisting of

(1) a pulse width,

(2) a pulse energy, and

(3) a pulse frequency to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

15. The method of claim 11, wherein the step of maintaining maintains a predetermined light output level of the LED units by measuring a current through the LED units and adjusting one or more pulse characteristics selected from the group consisting of

(1) a pulse width,

(2) a pulse energy, and

(3) a pulse frequency to the LED units based on the measured current to maintain an average light output at the predetermined level.

16. The method of claims 11, wherein the step of maintaining maintains a predetermined light output level of the LED units by measuring a light output and adjusting one or more pulse characteristics selected from the group consisting of

(1) a pulse width,

(2) a pulse energy, and

(3) a pulse frequency to the LED units based on the measured light output to maintain an average light output at the predetermined level.

17. The method of claim 11, wherein the step of maintaining maintains a predetermined light output level of the LED units by measuring a signal from a video camera and adjusting one or more pulse characteristics selected from the group consisting of

(1) a pulse width,

(2) a pulse energy, and

(3) a pulse frequency to the LED units based on the measured signal to maintain an average light output at the predetermined level.

18. An apparatus including an illumination source, comprising:

(a) a light-emitting diode (LED) housing comprising one or more LED units; and

(b) a control circuit that selectively applies pulsed power from a source of electric power to the LEDs, the control circuit controlling a pulse characteristic to the LED units to generate a first light color spectrum characteristic of the LED units at a first time and a second different light color spectrum characteristic of the LED units at a second time.

19. The apparatus of claim 18, wherein the controlled pulse characteristic includes a current amount, and wherein one of the one or more the LED units changes its color spectrum based on the current amount.

20. The apparatus of claim 18, wherein the one or more LED units comprise 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 from the second characteristic color spectrum output, and wherein the control circuit controls the pulse characteristic in order to control the proportion of light output having the first characteristic color spectrum output to that having the second characteristic color spectrum output.