High efficiency reflector for directing collimated light into light guides

• US 20010038736A1
• Filed: 05/29/2001
• Published: 11/08/2001
• Est. Priority Date: 03/08/1999
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Company
• Inventors: Whitehead, Lorne A.
• Granted Patent: US 6,418,253 B2
• Time in Patent Office: Days
• US Class Current: 385/31
• CPC Class Codes: G02B 6/0006 Coupling light into the fibre in general G02B6/4298
• CPC Class Codes: G02B 6/4298 coupling with non-coherent light sources and/or radiation detectors, e.g. lamps, incandescent bulbs, scintillation chambers

Abstract

A reflector for reflecting light from an elongate light source into the input end of a light guide having a diameter “D”. The light source is inserted through the narrow end of a collimating reflector which has a wide end with a diameter exceeding “D” through which light is emitted into the guide. The wide end of an output reflector circumferentially surrounds the collimating reflector'"'"'s wide end. The output reflector'"'"'s narrow end circumferentially surrounds the light guide'"'"'s input end. The wide end of an input reflector circumferentially surrounds the collimating reflector'"'"'s narrow end. The reflectors are cylindrically symmetrical about a common axis. Light passing from the light source to the collimating reflector is reflected, producing an output beam whose width varies as a function of distance along the axis. The light guide'"'"'s input end is positioned along the axis to minimize the width of the output light beam.

Claims

1. A reflector for reflecting light emitted by an elongate light source into an input end of a light guide having a light guide diameter “

D”

, said reflector comprising;

(a) a collimating reflector having;

(i) a narrow apertured end for insertable positioning of said light source within said collimating reflector;

(ii) a wide apertured end for emitting light into said light guide, said wide apertured end of said collimating reflector having a diameter exceeding said light guide diameter “

D”

;

(b) an output end annular reflector having;

(i) a wide apertured end circumferentially surrounding said collimating reflector near said wide apertured end of said collimating reflector;

(ii) a narrow apertured end circumferentially surrounding said input end of said light guide;

wherein;

(1) said reflectors are cylindrically symmetrical about a common longitudinal axis;

(2) light rays emitted by said light source which pass to said collimating reflector are reflected by said collimating reflector and produce an output light beam having a beam width which varies as a function of distance along said axis; and

,

(3) said light guide input end is positioned at a selected distance along said axis at which said output light beam has a minimum beam width value.

3. A reflector as defined in

claim 1

, wherein said collimating reflector is an off-axis paraboloidal cross-section, cylindrically symmetrical reflector.

6. A reflector as defined in

claim 3

, said input end annular reflector further comprising a curved surface, wherein in any cross-sectional plane containing said axis, said curved surface defines:

(i) a first arc on one side of said axis, said first arc having a first center of curvature located on said one side of said axis, and located within a cylinder which is symmetrical about said axis and which has a diameter not greater than the diameter of said narrow apertured end of said collimating reflector; and

,

(ii) a second arc on an opposed side of said axis, said second arc having a second center of curvature located on said opposed side of said axis, and located within said cylinder.

7. A reflector as defined in

claim 1

, wherein:

(a) said collimating reflector has a focal point f, and,

(b) said output end annular reflector further comprises a spherical arc section having a center of curvature near said focal point f.

9. A reflector as defined in

claim 3

, wherein said light source is a metal halide light bulb having an elongate light emitting arc.

10. A reflector as defined in

claim 9

, wherein said light emitting arc has one end near said focal point f and an opposed end near said narrow apertured end of said collimating reflector.

2. A reflector for reflecting light emitted by a light source into an input end of a light guide having a light guide diameter “

D”

, said reflector comprising;

(a) a collimating reflector having;

(i) a narrow apertured end for insertable positioning of said light source within said collimating reflector;

(ii) a wide apertured end for emitting light into said light guide, said wide apertured end of said collimating reflector having a diameter exceeding said light guide diameter “

D”

;

(b) an input end annular reflector having;

(i) a narrow apertured end for insertable positioning of said light source through said input end annular reflector;

(ii) a wide apertured end circumferentially surrounding said collimating reflector near said narrow apertured end of said collimating reflector;

(c) an output end annular reflector having;

(i) a wide apertured end circumferentially surrounding said collimating reflector near said wide apertured end of said collimating reflector; and

,

(ii) a narrow apertured end circumferentially surrounding said input end of said light guide;

wherein said reflectors are cylindrically symmetrical about a common longitudinal axis.

4. A reflector as defined in

claim 2

, wherein said collimating reflector is an off-axis paraboloidal cross-section, cylindrically symmetrical reflector.

8. A reflector as defined in

claim 2

, wherein:

(a) said collimating reflector has a focal point f; and

,

(b) said output end annular reflector further comprises a spherical arc section having a center of curvature near said focal point f.

11. A reflector as defined in

claim 2

, wherein:

(a) light rays emitted by said light source which pass to said collimating reflector are reflected by said collimating reflector and produce an output light beam having a beam width which varies as a function of distance along said axis; and

,

(b) said light guide input end is positioned at a selected distance along said axis at which said output light beam has a minimum beam width value.

12. A reflector as defined in

claim 4

, wherein:

(a) light rays emitted by said light source which pass to said collimating reflector are reflected by said collimating reflector and produce an output light beam having a beam width which varies as a function of distance along said axis; and

,

(b) said light guide input end is positioned at a selected distance along said axis at which said output light beam has a minimum beam width value.

5. A reflector for reflecting light emitted by a light source into an input end of a light guide, said reflector comprising:

(a) a collimating reflector having;

(i) a narrow apertured end for insertable positioning of said light source within said collimating reflector;

(ii) a wide apertured end for emitting light into said light guide;

(b) an input end annular reflector having;

(i) a narrow apertured end for insertable positioning of said light source through said input end annular reflector; and

,

(ii) a wide apertured end circumferentially surrounding said collimating reflector near said narrow apertured end of said collimating reflector;

wherein said reflectors are cylindrically symmetrical about a common longitudinal axis,

(c) said input end annular reflector further comprising a curved surface, wherein, in any cross-sectional plane containing said axis, said curved surface defines;

(i) a first arc on one side of said axis, said first arc having a first center of curvature located on said one side of said axis, and located within a cylinder which is symmetrical about said axis and which has a diameter not greater than the diameter of said narrow apertured end of said collimating reflector; and

,

(ii) a second arc on an opposed side of said axis, said second arc having a second center of curvature located on said opposed side of said axis, and located within said cylinder.

13. A reflector as defined in

claim 5

, wherein:

(a) light rays emitted by said light source which pass to said collimating reflector are reflected by said collimating reflector and produce an output light beam having a beam width which varies as a function of distance along said axis; and

,

(b) said light guide input end is positioned at a selected distance along said axis at which said output light beam has a minimum beam width value.