High efficiency prism light guide with confocal parabolic cross section

• US 5,715,347 A
• Filed: 10/12/1995
• Issued: 02/03/1998
• Est. Priority Date: 10/12/1995
• Status: Expired due to Term

• Current Assignee: University of British Columbia
• Original Assignee: University of British Columbia
• Inventors: Whitehead, Lorne A.
• Primary Examiner(s): Palmer, Phan T. H.
• Application Number:
  US08/542,164
• Time in Patent Office: 845 Days
• Field of Search: 385/133, 385/146, 385/147, 385/901, 362/32, 359/858, 359/861
• US Class Current: 385/133
• CPC Class Codes: G02B 6/032 with non solid core or cladding G02B6/02295 takes precedence
• CPC Class Codes: Y10S 385/901 Illuminating or display apparatus

Abstract

A hollow light guide with opposed first and second parallel sections having confocal, parabolic cross-sectional shape. The light guide may be a prism light guide, or other hollow light guide such as a metallic mirror light guide or a multi-layer dielectric light guide. The cross-sectional shapes have vertices separated by a distance which does not exceed about three times (preferably, about 2.5 times) the focal length of the shapes.

Claims

1. A hollow light guide comprising opposed first and second parallel sections, said sections having substantially confocal, substantially parabolic cross-sectional shape overlappingly enclosing a light guiding region, said shape having substantially constant cross-sectional area in any plane transverse to said parallel sections.

2. A light guide as defined in claim 1, wherein said light guide is a prism light guide.

3. A light guide as defined in claim 2, wherein said cross-sectional shapes have vertices separated by a distance which does not exceed about three times the focal length of said shapes.

4. A light guide as defined in claim 3, wherein said first and second sections are joined along one or more seams.

5. A light guide as defined in claim 2, wherein said cross-sectional shapes have vertices separated by a distance which does not exceed about 2.5 times the focal length of said shapes.

6. A light guide as defined in claim 5, wherein said first and second sections are joined along one or more seams.

7. A light guide as defined in claim 2, wherein said first and second sections are joined along one or more seams.

8. A method of making a hollow light guide, said method comprising the steps of:

(a) forming light guide wall material into first and second light guide sections, each of said sections having substantially parabolic cross-sectional shape, said shape having substantially constant cross-sectional area in any plane transverse to said sections; and

,

(b) joining said first and second light guide sections together to overlappingly enclose a light guiding region while maintaining said parabolic cross-sectional shapes substantially confocal with one another.

9. A method as defined in claim 8, further comprising, during said joining step, maintaining between parabolic vertices of said shapes a separation distance which does not exceed about three times the focal length of said shapes.

10. A method as defined in claim 9, wherein said light guide is a prism light guide and said wall material is prismatic wall material.

11. A method as defined in claim 8, further comprising, during said joining step, maintaining between parabolic vertices of said shapes a separation distance which does not exceed about 2.5 times the focal length of said shapes.

12. A method as defined in claim 11, wherein said light guide is a prism light guide and said wall material is prismatic wall material.

13. A method as defined in claim 8, wherein said light guide is a prism light guide and said wall material is prismatic wall material.