Pulse-controlled light emitting diode source

• US 6,222,172 B1
• Filed: 02/04/1999
• Issued: 04/24/2001
• Est. Priority Date: 02/04/1998
• Status: Expired due to Term

• Current Assignee: Round Rock Research LLC
• Original Assignee: Photobit Corporation (Micron Technology, Inc.)
• Inventors: Waligorski, Gregory, Fossum, Eric R.
• Primary Examiner(s): Allen, Stephone B.
• Application Number:
  US09/246,013
• Time in Patent Office: 810 Days
• Field of Search: 250/205, 250/216, 250/228, 356/30, 356/236, 356/243.5
• US Class Current: 250/205
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G01J 1/08 Arrangements of light sources specially adapted for photometry standard sources, also using luminescent or radioactive material

Abstract

A light-emitting diode array is driven by a digital control. The digital control modulates the pulse width of pulses applied to the light-emitting diode. The intensity of the output is controlled by controlling the width of pulses applied to the light-emitting diode. Since light-emitting diodes have very low inertial energy, this system can be rapidly turned on and turned off. The output is integrated to produce a uniform output.

Claims

1. A controllable light source, comprising:

a light source with low thermal inertia that has a response time less than 10 μ

s;

a controller for said light source, said controller including a device which produces a control signal having variable timing characteristics, said control signal having active portions and inactive portions between the active portions, a total active time of said control signal for a first command for a brighter light output being greater than a total active time for said pulses for a second command for a less bright output, said light source being turned on by said active portions to produce light and being turned off by said inactive portions; and

a light integrator, which integrates said light produced during said active portions, to thereby equalize a result thereof.

2. A device as in claim 1 wherein said low inertia light source includes a light-emitting diode (“

LED”

).

3. A device as in claim 1 wherein said low inertia light source includes at least three types of light emitting diodes, providing a total of three colored LEDs.

4. A device as in claim 2 wherein the pulses have a nominal on voltage level and a transition between a nominal low voltage level and said nominal on voltage level, a timing between said nominal on voltage level and said nominal off voltage level adjust an amount of light output.

5. A method of controlling a light-emitting diode-based light source, comprising:

providing at least one light-emitting diode; and

controlling an amount of time that said light-emitting diode is emitting light, by controlling an amount of on-time of a controlling signal to said light emitting diode relative to an amount of off time of said controlling signal, to control an effective output intensity of said at least one light-emitting diode; and

integrating the output of said at least one light emitting diode to equalize said output.

6. A method as in claim 5, wherein said integrating comprises reflecting light within a sphere.

7. A controllable light source, comprising:

at least three light emitting diodes, each having a different characteristic of output light;

a controller for said light emitting diodes, that produces a pulse-width modulated control pulse, having an on state and an off state;

a brightness controller, controlling said controller to produce longer on states for higher brightness, and shorter on states for lower brightness; and

a light integrator, surrounding said light emitting diodes, and which integrates light output from said light emitting diodes, said light integrator having an open portion defining an output port from which said integrated light is output.

8. A source as in claim 7, further comprising a light baffle, which diffuses light, located between said light emitting diodes, and said output port.

9. A source as in claim 7, wherein said light emitting diodes include at least a plurality of light emitting diodes of each of three colors.

10. A source as in claim 7, wherein said light emitting diodes emit their light in a direction away from said output port.

11. A controllable light source, comprising:

a light integrator, having an output port, and having an inner surface that reflects light;

an LED assembly, supported within said light integrator, and including a plurality of light emitting surfaces, and at least three types of light emitting diodes, at least one light emitting diode being mounted on each of said light emitting surface, each said type of light emitting diode having a different characteristic of output light produced thereby;

a reflecting baffle, mounted between said LED assembly and said output port, and reflecting light from said LED assembly so that said light cannot be directly projected from said LED assembly to said output port;

a controller for said light emitting diodes, that produces pulse-width modulated control pulses, having only an on state and an off state, and transitions between said on state and said off state;

a brightness controller, controlling an amount of said on state and an amount of said off state, to produce longer on states for higher brightness out of said output port, and shorter on states for lower brightness out of said output port.

12. A method of producing a controllable light amount, comprising:

producing a digital control signal that has active portions and inactive portions;

using said digital control signal to drive a digitally-controllable light source to produce output light; and

uniformizing said output light, to obtain output light of an intensity that is based on said digitally controllable light source.