Color sensor illumination source employing a lightpipe and multiple LEDs

• US 5,303,037 A
• Filed: 02/24/1992
• Issued: 04/12/1994
• Est. Priority Date: 02/24/1992
• Status: Expired due to Term

• Current Assignee: Camp Inc.
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Taranowski, Michael G.
• Primary Examiner(s): McGraw, Vincent P.
• Assistant Examiner(s): HANTIS, KAREN
• Application Number:
  US07/840,477
• Time in Patent Office: 778 Days
• Field of Search: 356/402-411, 356/445-448, 359/618, 359/629, 359/639-640, 250/226
• US Class Current: 356/406
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems
• CPC Class Codes: G01N 2201/0621 Supply

Abstract

A light transmitting source for a color sensor utilizes a plurality of light emitting diodes emitting light in a predetermined narrow range of wavelength whose emitted light strikes a surface of a lightpipe whereupon the light is reflected and refracted and directed to a common reflection point and where each emitted light is attenuated by the reflection and refraction a desired amount and directed to illuminate an object whose color is to be measured.

Claims

1. A color sensor light source for balancing and combining the emitted light from a plurality of light emitting diodes and then directing the combined emitted light toward an object comprising:

three light emitting sources each emitting light in a predetermined narrow range of wavelengths and each emitting light at a level of light power output;

a lightpipe having at least three surfaces formed on a one piece block structure, said emitted light from one of said light emitting sources directed toward one of said surfaces respectively;

a common transmission point on one of said surfaces from which said emitted light is transmitted along a substantially common path towards said object whose color is to be measured;

said surfaces oriented relative to said light emitting sources to reflect and refract said emitted light through said lightpipe and exiting therefrom at said common transmission point on one of said surfaces from which said emitted light is directed along a substantially common path towards said object whose color is to be measured, and where said emitted light from said light emitting source having a highest level of light power output is transmitted by one of said surfaces and then reflected from another of said surfaces and then reflected by another of said surfaces toward said common transmission point and where said emitted light from said light emitting source having an intermediate level of light power output is refracted by one of said surfaces and then reflected by another of said surfaces toward said common transmission point and where said emitted light from said light emitting source having a lowest level of light power output is refracted at one of said surfaces toward said common transmission point thereby substantially balancing the light power output from said three light emitting sources.

2. The color sensor light source of claim 1, wherein said light emitting sources are light emitting diodes.

3. The color sensor light source of claim 2, wherein said light emitting diodes are comprised of a first light emitting diode emitting light at a wavelength of approximately 605 nanometers at said highest light of light power output, and a second light emitting diode emitting light at a wavelength of approximately 555 nanometers at said intermediate level of light power output and a third light emitting diode emitting light at a wavelength of approximately 470 nanometers at said lowest level of light power output.

4. The color sensor light source of claim 3, wherein said surfaces are comprised of a first surface impinged directly upon by said emitted light from said first light emitting diode and a second surface impinged directly upon by said emitted light from said second light emitting diode and a third surface impinged directly upon by said emitted light from said third light emitting diode.

5. The color sensor light source of claim 1, wherein said lightpipe is formed of an acrylic material.

6. The color sensor light source of claim 1, wherein said lightpipe is formed of polycarbonate material.

7. The color sensor light source of claim 1, wherein a lens is interposed between each of said light emitting sources and each of said surfaces respectively.

8. The color sensor light source of claim 1, wherein a lens is interposed between said lightpipe and said object whose color is to be measured.

9. The color sensor light source of claim 1, wherein said surfaces are flat.

10. A method of balancing the light power output from three light emitting diodes in a color sensor light source comprising:

providing three light emitting diodes each emitting light in a predetermined range of wavelengths and each emitting light at a light power output level, a first light emitting diode having the highest light output power, a second light emitting diode having an intermediate light output power, and a third light emitting diode having a low light output power;

providing a lightpipe having at least three surfaces formed on a one piece block structure each of said light emitting diodes emitting light impinging upon each of said surfaces respectively;

transmitting said emitted light from said first light emitting diode through one of said surfaces into said lightpipe then reflecting said emitted light off another of said surfaces internal to said lightpipe then reflecting said emitted light off another of said surfaces exiting said lightpipe at a common point to illuminate an object whose color is to be measured;

refracting said emitted light from said second light emitting diode by one of said surfaces into said lightpipe then reflecting said emitted light off another of said surfaces exiting said lightpipe at said common point to illuminate said object whose color is to be measured;

refracting said emitted light from said third light emitting diode by one of said surfaces said emitted light then exiting said lightpipe at said common point to illuminate said object whose color is to be measured.

11. The method of balancing the light output power from three light emitting diodes as disclosed in claim 10 wherein, said first light emitting diode emits light at a wavelength of approximately 605 nanometers and where said second light emitting diodes emits light at a wavelength of approximately 555 nanometers and where said third light emitting diode emits light at a wavelength of approximately 470 nanometers.

12. The method of balancing the light output power from three light emitting diodes as disclosed in claim 10 wherein, said surfaces are comprised of a first surface and a second surface and a third surface where said emitted light from said first light emitting diode is transmitted by said first surface and then reflected by said second surface and then reflected by said third surface toward said object whose color is to be measured and where said emitted light from said second light emitting diode is refracted by said second surface and then reflected by said third surface toward said object whose color is to be measured and where said emitted light from said third light emitting diode is refracted by said third surface toward said object whose color is to be measured.