Apparatus for continuously controlled emission of light from prism light guide

• US 4,787,708 A
• Filed: 05/08/1987
• Issued: 11/29/1988
• Est. Priority Date: 05/08/1987
• Status: Expired due to Fees

• Current Assignee: 3M Company
• Original Assignee: TIR Systems Limited (Koninklijke Philips N.V.)
• Inventors: Whitehead, Lorne A.
• Primary Examiner(s): Lee, John D.
• Assistant Examiner(s): PALMER, PHAN T H
• Application Number:
  US07/047,661
• Time in Patent Office: 571 Days
• Field of Search: 350/96.10, 350/96.28, 350/96.29, 350/96.30, 350/96.32, 350/102, 350/103, 350/259, 350/262, 350/265, 350/286
• US Class Current: 385/133
• CPC Class Codes: G02B 6/0096 the lights guides being of the hollow type
• CPC Class Codes: G02B 6/032 with non solid core or cladding G02B6/02295 takes precedence
• CPC Class Codes: G02B 6/10 of the optical waveguide type G02B6/02, G02B6/24 take precedence; devices or arrangements for the control of light by electric, magnetic, electro-magnetic or acoustic means G02F1/00; transferring the modulation of modulated light G02F2/00; optical logic elements G02F3/00; optical analogue/digital converters G02F7/00

Abstract

A variety of techniques are used to effect continuously controlled emission of light from a light guide. For example, the light guide may contain a mechanism formed of a substantially non-light absorptive material having a density which varies as a function of the length of the light guide. The mechansim causes light to escape from the light guide at a rate which varies along the length of the light guide, such that the amount of light escaping, per unit length, along the light guide has a selected distribution of values. Alternatively, the light guide'"'"'s central path may be non-linear. As a further alternative, the average cross-sectional dimension of each of the plane segments aforesaid may be non-constant. As yet another alternative, a first portion of the light guide may comprise prism light guide material and the remaining portion may be such that a substantial portion of light incident thereupon is allowed to escape therethrough.

Claims

1. A light guide, having:

(i) a central path comprising the locus of points which are the centroids of the segments contained within said light guide of all planes which intersect said light guide and which are oriented such that the area of each of said plane segments is a minimum; and

,

(iii) an average cross-sectional dimension comprising, for each one of said plane segments, the average length of those portions of all lines within said light guide which lie on said one plane segment and which intersect said light guide;

wherein;

(a) the length of said light guide is substantially greater than the average cross-sectional dimension of substantially all of said plane segments;

(b) the fractional rate of change, along said light guide, of substantially all randomly selected cross-sectional dimensions of said light guide, is substantially less than the reciprocal of the average cross-sectional dimension of substantially all of said plane segments;

(c) the radius of curvature of said central path at substantially all randomly selected points on said central path is substantially greater than the average cross-sectional dimension of substantially all of said plane segments; and

,

(d) said light guide contains a mechanism which causes light to escape from said light guide at a rate which varies along the length of said light guide, such that the mount of light escaping, per unit length, along said light guide has a selected distribution of values, wherein;

(I) said mechanism is a substantially non light absorptive material; and

,

(II) the density of said material varies as a function of the length of said light guide.

2. A light guide, as defined in claim 1, wherein said central path is non linear.

3. A light guide as defined in claim 2, wherein said non linearity is such that light escapes from said light guide at a rate which varies as a function of the length of said light guide.

4. A light guide as defined in claim 3, wherein the amount of light escaping, per unit length, from said light guide is substantially constant along the length of said light guide.

5. A light guide as defined in claim 2, 3 or 4, further comprising an external cover over at least a portion of said light guide, whereby:

(a) a portion of the light which escapes from said light guide is transmitted through said cover and away from said light guide; and

,

(b) the remaining portion of said escaping light is reflected by said cover back into said light guide.

6. A light guide, as defined in claim 1, wherein the average cross-sectional dimension of each of said plane segments is non constant.

7. A light guide as defined in claim 6, wherein said the average cross-sectional dimension of each of said plane segments varies such that light escapes from said light guide at a rate which varies as a function of the length of said light guide.

8. A light guide as defined in claim 7, wherein the amount of light escaping, per unit length, from said light guide is substantially constant along the length of said light guide.

9. A light guide as defined in claim 6, 7 or 8, further comprising an external cover over at least a portion of said light guide, whereby:

(a) a portion of the light which escapes from said light guide is transmitted through said cover and away from said light guide; and

,

(b) the remaining portion of said escaping light is reflected by said cover back into said light guide.

10. A light guide as defined in claim 1, wherein:

(a) a first portion of said light guide comprises prism light guide material; and

,

(e) the remaining portion of said light guide allows a substantial portion of light incident thereupon to escape therethrough.

11. A light guide as defined in claim 10, wherein the ratio of said first and remaining portions varies, along said light guide, such that a substantially constant amount of light escapes through said remaining portion at all points along said light guide.

12. A light guide as defined in claim 10 or 11, further comprising an external cover over at least a portion of said light guide, whereby:

(a) a portion of the light which escapes from said remaining portion is transmitted through said cover and away from said light guide; and

,

(b) the remaining portion of said escaping light is reflected by said cover back into said light guide.

13. A light guide as defined in claim 11, wherein said remaining portion is formed by removing a selected amount of prism light guide material from a selected portion of said light guide.

14. A light guide as defined in claim 11, wherein said remaining portion is formed by altering the optical characteristics of a selected part of the prism light guide material initially forming part of said first portion to prevent specular total internal reflection of light within said light guide from occurring at said selected part.

15. A light guide as defined in claim 11, wherein said remaining portion is formed by placing in optical contact with a selected part of the prism light guide material initially forming part of said first portion, a substance which prevents specular total internal reflection of light within said light guide from occurring.

16. A light guide, having:

(i) a central path comprising as the locus of points which are the centroids of the segments contained with in said light guide of all planes which intersect said light guide and which are oriented such that the area of each of said plane segments is a minimum; and

,

(ii) an average cross-sectional dimension comprising, for each one of said plane segments, the average length of those portions of all lines within said light guide which lie on said one plane segment and which intersect said light guide;

wherein;

(a) the length of said light guide is substantially greater than the average cross-sectional dimension of substantially all of said plane segments;

(b) the fractional rate of change, along said light guide, of substantially all randomly selected cross-sectional dimensions of said light guide, is substantially less than the reciprocal of the average cross-sectional dimension of substantially all of said plane segments;

(c) the radius of curvature of said central path at substantially all randomly selected points on said central path is substantially greater than the average cross-sectional dimension of substantially all of said plane segments; and

(d) said light guide contains a mechanism which causes light to escape from said light guide at a rate which varies along the length of said light guide, such that the amount of light escaping, per unit length, along said light guide has a selected distribution of values,

and further comprising

an external cover over at least a portion of said light guide, whereby;

(a) a portion of the light which escapes from said light guide is transmitted through said cover and away from said light guide; and

(b) the remaining portion of said escaping light is reflected by said cover back into said light guide.

17. A light guide, having:

(i) a central path comprising the locus of points which are the centroids of the segments contained within said light guide of all planes which intersect said light guide and which are oriented such that the area of each of said plane segments is a minimum; and

,

(ii) an average cross-sectional dimension comprising, for each one of said plane segments, the average length of those portions of all lines within said light guide which lie on said one plane segment and which intersect said light guide;

wherein;

(a) the length of said light guide is substantially greater than the average cross-sectional dimension of substantially all of said plane segments;

(b) the fractional rate of change, along said light guide, of substantially all randomly selected cross-sectional dimensions of said light guide, is substantially less than the reciprocal of the average cross-sectional dimension of substantially all of said plane segments;

(c) the radius of curvature of said central path at substantially all randomly selected points on said central path is substantially greater than the average cross-sectional dimension of substantially all of said plane segments; and

,

(d) said central path is non linear.

18. A light guide as defined in claim 17, wherein said non linearity is such that light escapes from said light guide at a rate which varies as a function of the length of said light guide.

19. A light guide as defined in claim 18, wherein the amount of light escaping, per unit length, from said light guide is substantially constant along the length of said light guide.

20. A light guide as defined in claim 17, 18 or 19, further comprising an external cover over at least a portion of said light guide, whereby:

(a) a portion of the light which escapes from said light guide is transmitted through said cover and away from said light guide; and

,

(b) the remaining portion of said escaping light is reflected by said cover back into said light guide.

21. A light guide, as defined in claim 17, wherein the average cross-sectional dimension of each of said plane segments is non constant.

22. A light guide as defined in claim 21, wherein said the average cross-sectional dimension of each of said plane segments varies such that light escapes from said light guide at a rate which varies as a function of the length of said light guide.

23. A light guide as defined in claim 22, wherein the amount of light escaping, per unit length, from said light guide is substantially constant along the length of said light guide.

24. A light guide as defined in claim 21, 22 or 23, further comprising an external cover over at least a portion of said light guide, whereby:

(a) a portion of the light which escapes from said light guide is transmitted through said cover and away from said light guide; and

,

(b) the remaining portion of said escaping light is reflected by said cover back into said light guide.

25. A light guide as defined in claim 17,

(a) wherein a first portion of said light guide comprises prism light guide material;

and,

(e) the remaining portion of said light guide allows a substantial portion of light incident thereupon to escape therethrough.

26. A light guide as defined in claim 25, wherein the ratio of said first and remaining portions varies, along said light guide, such that a substantially constant amount of light escapes through said remaining portion at all points along said light guide.

27. A light guide as defined in claim 25 or 26, further comprising an external cover over at least a portion of said light guide, whereby:

(a) a portion of the light which escapes from said remaining portion is transmitted through said cover and away from said light guide; and

,

(b) the remaining portion of said escaping light is reflected by said cover back into said light guide.

28. A light guide as defined in claim 26, wherein said remaining portion is formed by removing a selected amount of prism light guide material from a selected portion of said light guide.

29. A light guide as defined in claim 26, wherein said remaining portion is formed by altering the optical characteristics of a selected part of the prism light guide material initially forming part of said first portion to prevent specular total internal reflection of light within said light guide from occurring at said selected part.

30. A light guide as defined in claim 26, wherein said remaining portion is formed by placing in optical contact with a selected part of the prism light guide material initially forming part of said first portion, a substance which prevents specular total internal reflection of light within said light guide from occurring.

31. A light guide, having:

(i) a central path comprising the locus of points which are the centroids of the segments contained within said light guide of all planes which intersect said light guide and which are oriented such that the area of each of said plane segments is a minimum; and

,

(ii) an average cross-sectional dimension comprising, for each one of said plane segments, the average length of those portions of all lines within said light guide which lie on said one plane segment and which intersect said light guide;

wherein;

(a) the length of said light guide is substantially greater than the average cross-sectional dimension of substantially all of said plane segments;

(b) the fractional rate of change, along said light guide, of substantially all randomly selected cross-sectional dimensions of said light guide, is substantially less than the reciprocal of the average cross-sectional dimension of substantially all of said plane segments;

(c) the radius of curvature of said central path at substantially all randomly selected points on said central path is substantially greater than the average cross-sectional dimension of substantially all of said plane segments; and

,

(d) the average cross-sectional dimension of each of said plane segments is non constant.

32. A light guide as defined in claim 31, wherein said the average cross-sectional dimension of each of said plane segments varies such that light escapes from said light guide at a rate which varies as a function of the length of said light guide.

33. A light guide as defined in claim 32, wherein the amount of light escaping, per unit length, from said light guide is substantially constant along the length of said light guide.

34. A light guide as defined in claim 31, 32 or 33, further comprising an external cover over at least a portion of said light guide, whereby:

(a) a portion of the light which escapes from said light guide is transmitted through said cover and away from said light guide; and

,

(b) the remaining portion of said escaping light is reflected by said cover back into said light guide.

35. A light guide as defined in claim 31, wherein:

(a) a first portion of said light guide comprises prism light guide material; and

,

(e) the remaining portion of said light guide allows a substantial portion of light incident thereupon to escape therethrough.

36. A light guide as defined in claim 35, wherein the ratio of said first and remaining portions varies, along said light guide, such that a substantially constant amount of light escapes through said remaining portion at all points along said light guide.

37. A light guide as defined in claim 35 or 36, further comprising an external cover over at least a portion of said light guide, whereby:

(a) a portion of the light which escapes from said remaining portion is transmitted through said cover and away from said light guide; and

,

(b) the remaining portion of said escaping light is reflected by said cover back into said light guide.

38. A light guide as defined in claim 36, wherein said remaining portion is formed by removing a selected amount of prism light guide material from a selected portion of said light guide.

39. A light guide as defined in claim 36, wherein said remaining portion is formed by altering the optical characteristics of a selected part of the prism light guide material initially forming part of said first portion to prevent specular total internal reflection of light within said light guide from occurring at said selected part.

40. A light guide as defined in claim 36, wherein said remaining portion is formed by placing in optical contact with a selected part of the prism light guide material initially forming part of said first portion, a substance which prevents specular total internal reflection of light within said light guide from occurring.

41. A light guide, having:

(i) a central path comprising the locus of points which are the centroids of the segments contained within said light guide of all planes which intersect said light guide and which are oriented such that the area of each of said plane segments is a minimum; and

,

(ii) an average cross-sectional dimension comprising, for each one of said plane segments, the average length of those portions of all lines within said light guide which lie on said one plane segment and which intersect said light guide;

wherein;

(a) the length of said light guide is substantially greater than the average cross-sectional dimension of substantially all of said plane segments;

(b) the fractional rate of change, along said light guide, of substantially all randomly selected cross-sectional dimensions of said light guide, is substantially less than the reciprocal of the average cross-sectional dimension of substantially all of said plane segments;

(c) the radius of curvature of said central path at substantially all randomly selected points on said central path is substantially greater than the average cross-sectional dimension of substantially all of said plane segments;

(d) a first portion of said light guide comprises prism light guide material; and

,

(e) the remaining portion of said light guide allows a substantial portion of light incident thereupon to escape therethrough.

42. A light guide as defined in claim 41, wherein the ratio of said first and remaining portions varies, along said light guide, such that a substantially constant amount of light escapes through said remaining portion at all points along said light guide.

43. A light guide as defined in claim 41 or 42, further comprising an external cover over at least a portion of said light guide, whereby:

(a) a portion of the light which escapes from said remaining portion is transmitted through said cover and away from said light guide; and

,

(b) the remaining portion of said escaping light is reflected by said cover back into said light guide.

44. A light guide as defined in claim 42, wherein said remaining portion is formed by removing a selected amount of prism light guide material from a selected portion of said light guide.

45. A light guide as defined in claim 42, wherein said remaining portion is formed by altering the optical characteristics of a selected part of the prism light guide material in initially forming part of said first portion to prevent specular total internal reflection of light within said light guide from occurring at said selected part.

46. A light guide as defined in claim 42, wherein said remaining portion is formed by placing in optical contact with a selected part of the prism light guide material initially forming part of said first portion, a substance which prevents specular total internal reflection of light within said light guide from occurring.