Light source assembly for scanning devices utilizing light emitting diodes

• US 6,139,174 A
• Filed: 08/25/1998
• Issued: 10/31/2000
• Est. Priority Date: 08/25/1998
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Butterworth, Mark M.
• Primary Examiner(s): O'Shea, Sandra
• Assistant Examiner(s): Alavi, Ali
• Application Number:
  US09/139,904
• Time in Patent Office: 798 Days
• Field of Search: 362/84, 362/260, 362/551, 362/555, 362/582, 362/230, 362/231
• US Class Current: 362/555
• CPC Class Codes: H04N 1/02815 Means for illuminating the original, not specific to a particular type of pick-up head
• CPC Class Codes: H04N 1/02835 in combination with a light guide, e.g. optical fibre, glass plate light-guides per se G02B6/00
• CPC Class Codes: H04N 1/02855 in combination with a light guide, e.g. optical fibre, glass plate light-guides per se G02B6/00

Abstract

A light source assembly and method of providing illumination a target surface utilize a fluorescent material to generate composite "white" light from source light of a particular color, i.e., a particular wavelength. The light source assembly is optimally designed for use in scanning devices, such as flat-bed color scanners, in which linear illumination is necessary to capture images, graphics, and/or text from a target scanned surface. In the preferred embodiment, the light source assembly includes a Gallium Nitride (GaN) based light emitting diode (LED) that emits blue source light and a light transmitting rod lens. The light transmitting rod lens is preferably a solid transparent structure, designed to receive the blue source light through one end of the rod and transmit a composite "white" light from the entire length of the rod, providing the desired linear illumination. The rod lens includes two fluorescent strips and a non-fluorescent strip, located near the exterior surface of the rod. The two fluorescent strips operate to absorb the blue source light and to emit red light and green light, while the non-fluorescent strip reflects the blue source light. The emitted red and green light, along with the reflected blue light, form the composite light that provides the linear illumination on the target surface.

Claims

1. A light source assembly for scanning devices comprising:

generating means for emitting light of a first center wavelength, said light of said first center wavelength being a first component of a composite light;

an elongated structure having a first port on an exterior surface, said first port being optically coupled to said generating means to receive said light of said first center wavelength from said generating means, said exterior surface defining an interior region of said elongated structure to provide a propagation conduit for said light of said first center wavelength, said elongated structure having a second port along a length of said elongated structure;

a first fluorescent material operationally associated with said elongated structure, said fluorescent material being distributed generally along a length-wise direction of said elongated structure, said fluorescent material having a property to absorb said light of said first center wavelength and emit light of a second center wavelength, said light of said second center wavelength being a second component of said composite ligh; and

a second fluorescent material located near said exterior surface of said elongated structure, said second fluorescent material being distributed generally parallel to said first fluorescent material, said second fluorescent material having a property to absorb said light of said first center wavelength and emit light of a third center wavelength, said light of said third center wavelength being a third component of said composite light, said composite light being a generally white light;

wherein said second port of said elongated structure is positioned and oriented to simultaneously direct and focus said first, second and third components of said composite light away from said elongated structure and toward a target surface.

2. The light source assembly of claim 1 wherein said generating means is a light emitting diode positioned adjacent to said first port of said elongated structure to emit said light of said first center wavelength to said interior region via said first port.

3. The light source assembly of claim 2 wherein said light emitting diode (LED) is a Gallium Nitride (GaN) based LED, said GaN based LED configured to emit said light of said first center wavelength wherein said first center wavelength is within a blue region of a visible light spectrum.

4. The light source assembly of claim 1 wherein said first and second fluorescent materials are fluorescent organic dyes.

5. The light source assembly of claim 1 further comprising a diffusive material on said exterior surface of said elongated structure, said diffusive material being distributed generally parallel to said first and second fluorescent materials.

6. The light source assembly of claim 1 wherein said elongated structure is a solid rod composed of a transparent material, said transparent material providing a propagation medium for said light of said first center wavelength within said elongated structure.

7. The lights source of claim 6 wherein said solid rod has a generally circular cross-section, said second port and said first fluorescent material having centers spaced apart by approximately 180 degrees along said generally circular cross-section.

8. The light source assembly of claim 6 wherein said solid rod has a U-shaped cross-section, said fluorescent materials being located near a bottom of said U-shaped cross-section and said second port being located on a top of said U-shaped cross-section.

9. The light source assembly of claim 6 wherein said first and second fluorescent materials are diffused into said solid rod, thereby forming fluorescent regions within said solid rod.

10. A light source assembly for a scanning device comprising:

a light source configured to emit light of a first center wavelength;

a solid transparent rod having a first port at one end operatively associated with said light source to receive said light of said first center wavelength, said solid transparent rod having a second port along a length of said solid transparent rod directed to transmit light to a target surface; and

fluorescent means operatively associated with said length of said solid transparent rod for fluorescing light having at least one component with a center wavelength significantly different than said first center wavelength, said fluorescent means being responsive to said light of said first center wavelength propagating through said solid transparent rod, said second port being positioned to simultaneously release and focus said light of said first center wavelength and said light from said fluorescent means onto said target surface.

11. The light source assembly of claim 10 further comprising means for attaching said light source and said solid transparent rod for movement relative to said target scanned surface.

12. The light source assembly of claim 10 wherein said fluorescent means includes at least one organic fluorescent dye responsive to said light of said first center wavelength.

13. The light source assembly of claim 10 wherein said light source is a light emitting diode.

14. The light source assembly of claim 13 wherein said light emitting diode (LED) is a Gallium Nitride (GaN) based LED configured to emit blue light.

15. The light source assembly of claim 10 wherein said solid transparent rod is made of a plastic material and wherein said flourescent means includes at least one fluorescent material diffused into said solid transparent rod along said length.

16. A method of providing illumination on a scanned surface comprising steps of:

emitting light of a first center wavelength from a light source;

receiving said light of said first center wavelength through a port at one end of an elongated rod, said elongated rod being transparent to allow said light of said first center wavelength to propagate within said elongated rod;

absorbing at least some of said light of said first center wavelength by a fluorescent material located near an outer surface of said elongated rod, said fluorescent material being distributed generally along a lengthwise direction of said elongated rod;

emitting light of a second center wavelength by said fluorescent material in response to an absorption of said light of said first center wavelength; and

simultaneously transmitting said light of said first and said second center wavelengths in a common direction away from said elongated rod and toward a target surface.

17. The method of claim 16 wherein said step of emitting said light of said first center wavelength includes employing a light emitting diode to generate said light of said first center wavelength.

18. The method of claim 16 wherein said step of emitting said light of said first center wavelength includes employing a Gallium Nitride (GaN) based light emitting diode to generate said light within a blue region of a visible light spectrum.

19. The method of claim 16 further comprising steps of:

absorbing at least some of said light of said first center wavelength by a second fluorescent material located near said outer surface of said elongated rod, said second fluorescent material being distributed generally along said lengthwise direction of said elongated rod; and

emitting light of a third center wavelength by said second fluorescent material in response to an absorption of said light of said first center wavelength by said second fluorescent material.

20. The method of claim 16 further comprising a step of focusing said light of said first and said second center wavelengths within said elongated rod prior to said step of transmitting said light of said first and said second center wavelengths.