Optical fiber illumination system

• US 5,845,038 A
• Filed: 01/28/1997
• Issued: 12/01/1998
• Est. Priority Date: 01/28/1997
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Lea, Michael C., Lundin, David Jon
• Primary Examiner(s): NGO, HUNG NHAT
• Application Number:
  US08/789,808
• Time in Patent Office: 672 Days
• Field of Search: 385/901, 385/31, 385/146, 385/47, 362/32
• US Class Current: 362/551
• CPC Class Codes: G02B 6/001 the light being emitted along at least a portion of the lateral surface of the fibre

Abstract

An illumination system comprises a light source optically coupled with an optical fiber. The optical fiber includes a light emitting region extending along a portion of its length. The light emitting region includes a plurality of optical elements disposed about a first longitudinal axis extending along the surface of the optical fiber and a plurality of optical elements disposed about a second longitudinal axis extending along the surface of the fiber. The second longitudinal axis is displaced from the first longitudinal axis. In use, light from the light source is injected into the optical fiber and propagates along the fiber according to Snell'"'"'s law. A portion of the light propagating through the fiber becomes is reflected from the optical elements and is extracted from the fiber.

Claims

1. An illumination system, comprising:

an optical fiber including an optical fiber core having an optically smooth surface for propagating light through the fiber and a light emitting region extending along a portion of the fiber, the light emitting region including;

a first plurality of optical elements centered about a first longitudinal axis extending along the optically smooth surface of the optical fiber core, each optical element including an optically reflective surface extending into the optical fiber core; and

a second plurality of optical elements centered about a second longitudinal axis extending along the optically smooth surface of the optical fiber core, each element including an optically reflective surface extending into the optical fiber core, the second longitudinal axis displaced from the first longitudinal axis.

2. An illumination system according to claim 1, wherein:

the second longitudinal axis is angularly displaced from the first longitudinal axis by an angle measuring between 1° and

180°

.

3. An illumination system according to claim 1, wherein:

the second longitudinal axis is angularly displaced from the first longitudinal axis by an angle measuring between 5° and

100°

.

4. An illumination system according to claim 1, wherein:

the second longitudinal axis is angularly displaced from the first longitudinal axis by an angle measuring between 5° and

20°

.

5. An illumination system according to claim 1, wherein:

the second longitudinal axis is angularly displaced from the first longitudinal axis by an angle measuring 10°

.

6. An illumination system according to claim 1, wherein the light emitting region comprises:

a plurality of optical elements centered about a third longitudinal axis extending along the optically smooth surface of the optical fiber core and including an optically reflective surface extending into the optical fiber core, the third longitudinal axis being angularly displaced from the first longitudinal axis and the second longitudinal axis.

7. An illumination system according to claim 1, further comprising:

a light source optically coupled to the optical fiber.

8. An illumination system according to claim 1, wherein:

the optical fiber has a cross-sectional shape selected from the group of cross-sectional shapes consisting of circular, elliptical, oval, rectangular, square, and polygonal.

14. The illumination system of claim 1, wherein a spacing between the optical elements is between 0.05 and 5.0 millimeters.

15. The illumination system of claim 14, wherein optical elements in the first plurality of optical elements are substantially identical in size and geometry to optical elements in the second plurality of optical elements.

16. The illumination system of claim 14, wherein the first and second plurality of optical elements have a size and geometry such that the displacement between the first and second longitudinal axis is sufficient to reduce shadowing effects between elements in the first plurality of optical elements and elements in the second plurality of optical elements.

17. The illumination system of claim 14, wherein the optical elements are interspersed along the waveguide in an alternating pattern of one optical element from the first plurality of optical elements followed by one optical element from the second plurality of optical elements.

9. An optical waveguide adapted to reduce visible variations in the angular intensity of light reflected from the waveguide in a viewing region centered about an axis disposed at a desired viewing angle, γ

, comprising;

a core formed from a substantially optically transparent material having a first surface adapted for receiving light from a light source and at least one optically smooth surface for propagating light through the waveguide along an axis of propagation, the optical surface comprising a plurality of optical elements, each optical elements having at least one optically reflective surface disposed at an oblique angle θ

to a plane perpendicular to the axis of propagation;

the angle θ

being determined by the equation;

##EQU9## wherein ξ

is selected from the group of angles extending from (α

/2) to (β

/2) or (-β

/2) to (-α

) and wherein

α

=the shadowing angle

β

=the cone angle of light propagating through the optical fiber; and

γ

'"'"'=the desired exit angle of reflected light.

10. An optical waveguide according to claim 9, wherein:

##EQU10##

11. An optical fiber illumination system adapted for use as an automobile warning light, comprising:

an optical fiber having opposing first and second surfaces adapted for receiving light from a light source and a reflective surface for propagating light through the fiber along an axis of propagation, the optical fiber having a length of approximately 500 millimeters and a diameter of approximately 9.5 millimeters;

a plurality of optical elements centered about a first longitudinal axis extending along the surface of the optical fiber, each optical element having a first reflective surface and a second reflective surface that extend into the fiber to a depth of 0.25 millimeters;

a plurality of optical elements centered about a second longitudinal axis extending along the surface of the optical fiber, each optical element having a first reflective surface and a second reflective surface that extend into the fiber to a depth of 0.25 millimeters;

the first longitudinal axis being angularly displaced from the second longitudinal axis by 10°

.

12. An optical fiber illumination system according to claim 11, wherein:

each optical element comprises a first optically reflective surface extending into the core of the optical fiber and disposed at an angle of approximately 52.5°

relative to an axis perpendicular to the axis of propagation.

13. An optical fiber illumination system according to claim 12, wherein:

each optical element further comprises a second optically reflective surface extending into the core of the optical fiber and disposed at an angle of approximately 52.5°

relative to an axis perpendicular to the axis of propagation, the first and second optically reflective surfaces intersecting along a linear groove base.

18. An optical waveguide having an axis and having a core formed from a substantially optically transparent material, the core having a perimeter and comprising:

a first surface adapted to receive light from a light source; and

a light emitting region including a plurality of optical elements disposed on one side of the perimeter and an optically smooth surface on an opposed side of the perimeter, each optical element including a reflective surface extending into the core;

wherein the optical elements are arranged along the waveguide axis in a first and second overlapping sequence that are displaced relative to each other in a lateral direction perpendicular to the waveguide axis to enhance the angular spread in the lateral direction of light energy emitted from the optically smooth surface.

19. The waveguide of claim 18, wherein the plurality of optical elements are arranged along the waveguide axis in an alternating fashion between the first and second overlapping sequence.

20. The waveguide of claim 18, wherein the plurality of optical elements are spaced along the waveguide axis by between 0.05 and 5.0 millimeters.

21. The waveguide of claim 20, wherein the displacement between the first and second overlapping sequence reduces shadowing effects between optical elements.

22. The waveguide of claim 20, wherein the plurality of optical elements are substantially identical in size and geometry.

23. The waveguide of claim 20, wherein, when viewed along the waveguide axis, the optical elements in the first overlapping sequence subtend a first portion of the perimeter and the optical elements in the second overlapping sequence subtend a second portion of the perimeter, and wherein the first and second portions of the perimeter overlap.