Totally internally reflecting light conduit

• US 5,745,632 A
• Filed: 03/25/1997
• Issued: 04/28/1998
• Est. Priority Date: 10/18/1995
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Dreyer, John F.
• Primary Examiner(s): Palmer, Phan T. H.
• Application Number:
  US08/824,027
• Time in Patent Office: 399 Days
• Field of Search: 385/133, 385/146, 385/147, 385/901, 359/831, 359/833, 359/850, 359/515, 362/32, 362/346
• US Class Current: 385/133
• CPC Class Codes: G02B 6/0001 specially adapted for lighting devices or systems lighting or signalling on vehicles using light guides B60Q1/00; lighting devices for vehicle dashboards B60Q3/10; lighting devices for vehicle interior using light guides B60Q3/62; lighting devices mounted on the vehicle rear part using light guides F21S43/235; measuring arrangements having light conducting pointers G01D13/265; illumination of liquid crystal displays G02F1/1336; illuminated signs G09F13/00
• 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: Y10S 385/901 Illuminating or display apparatus

Abstract

A hollow, cylindrical light conduit for transporting light generally longitudinally therethrough and distributing light therealong includes a cylindrical wall member of a transparent material. The wall member has an inner cylindrical smooth surface and an outer cylindrical structured surface having an array of isosceles prisms arranged side by side thereon. The faces of adjacent prisms extend longitudinally along the cylindrical wall member and are aligned at the same desired prism angle relative to one another. The light transporting performance of the light conduit, achieved by total internal reflection, and the light distributing performance of the light conduit, specifically relative to radially aligned, high incident angle longitudinal light rays in planes parallel or near parallel to the prisms, is optimized as a function of the desired prism angle between the faces of adjacent prisms.

Claims

1. A hollow tubular light conduit for distributing light therefrom comprising:

a cylindrical wall member of a transparent material, the wall member having an inner smooth surface and an outer structured surface, the structured surface having a linear array of isosceles prisms arranged side by side thereon with faces of adjacent prisms extending longitudinally along the cylindrical wall member and aligned at a selected prism angle of greater than 0 and less than 90 degrees wherein, depending on the selected prism angle, the wall member exhibits light distribution relative to radially aligned, high incident angle longitudinal light rays in planes parallel or near parallel to the prisms when the following condition is satisfied;

N₀ β

+β

/2=90

where

β

=the selected prism angle

N₀ =zero or any positive integer.

2. In a tubular light conduit for transporting light generally longitudinally therethrough and distributing light therealong, wherein the light conduit has a cylindrical wall member of a transparent material and wherein the wall member has an inner cylindrical smooth surface and an outer cylindrical structured surface having an array of isosceles prisms arranged side by side thereon, with faces of adjacent prisms extending longitudinally along the cylindrical wall member and aligned at a same desired prism angle, the improvement which comprises:

optimizing the light transporting performance by the light conduit, by total internal reflection, and the light distributing performance of the light conduit, relative to radially aligned, high incident angle longitudinal light rays in planes parallel or near parallel to the prisms, as a function of the desired prism angle between the faces of adjacent prisms

wherein the function for achieving light transporting by total internal reflection comprises;

Nβ

=90, when 0°

<

β

<

90°

,

Th=(N₀ +1/2)W×

tan(270-2β

), when 90°

<

β

<

120°

,

β

=120°

, and ##EQU2## when 120°

<

β

180°

, where

β

=the desired prism angle

N=any positive integer

Th=the average thickness of the wall member

N₀ =zero or any positive integer

W=one half the width of each prism.

3. In a tubular light conduit for transporting light generally longitudinally therethrough and distributing light therealong, wherein the light conduit has a cylindrical wall member of a transparent material and wherein the wall member has an inner cylindrical smooth surface and an outer cylindrical structured surface having an array of isosceles prisms arranged side by side thereon, with faces of adjacent prisms extending longitudinally along the cylindrical wall member and aligned at a same desired prism angle, the improvement which comprises:

optimizing the light transporting performance by the light conduit, by total internal reflection, and the light distributing performance or the light conduit, relative to radially aligned, high incident angle longitudinal light rays in planes parallel or near parallel to the prisms, as a function of the desired prism angle between the faces or adjacent prisms

wherein the desired prism angle is 120 degrees.

4. In a tubular light conduit for transporting light generally longitudinally therethrough and distributing light therealong wherein the light conduit has a cylindrical wall member or a transparent material and wherein the wall member has an inner cylindrical smooth surface and an outer cylindrical structured surface having an array of prisms arranged side by side thereon, with faces of adjacent prisms extending longitudinally along the cylindrical wall member and aligned at a same desired prism angle, the improvement which comprises:

optimizing the light transporting performance by the light conduit, by total internal reflection, and the light distributing performance of the light conduit, relative to radially aligned, high incident angle longitudinal light rays in planes parallel or near parallel to the prisms, as a function of the desired prism angle between the faces of adjacent prisms

wherein the prisms are non-isosceles prisms.

5. A hollow tubular light conduit for transporting light therealong and distributing light therefrom comprises:

a cylindrical wall member of a transparent material, the wall member having an inner smooth surface and an outer structured surface, the structured surface having a linear array of isosceles prisms arranged side by side thereon with faces of adjacent prisms extending longitudinally along the cylindrical wall member and aligned at a selected prism angle of greater than 90 and less than 120 degrees wherein, depending on the selected prism angle, the wall member exhibits light piping via total internal reflection relative to radially aligned, high incident angle longitudinal light rays in planes parallel or near parallel to the prisms when the following condition is satisfied;

Th=(N₀ +1/2)W×

tan (270-2β

)

where

β

=the selected prism angle

Th=the average thickness of the wall member

N₀ =zero or any positive integer

W=one half the width of each prism.

6. A hollow tubular light conduit for transporting light therealong and distributing light therefrom comprises:

a cylindrical wall member of a transparent material, the wall member defined by an inner smooth surface and an outer structured surface, the structured surface having a linear array of prisms arranged side by side thereon, with faces of adjacent prisms extending longitudinally along the cylindrical wall member and aligned at a selected prism angle of 120 degrees, and with each face aligned at 30 degrees relative to the tangent of the opposite smooth surface, wherein the wall member exhibits light piping via total internal reflection relative to radially aligned, high incident angle longitudinal light rays in planes parallel or near parallel to the prisms.

7. A hollow tubular light conduit for transporting light therealong and distributing light therefrom comprises:

a cylindrical wall member of a transparent material, the wall member having an inner smooth surface and an outer structured surface, the structured surface having a linear array of isosceles prisms arranged side by side thereon with faces of adjacent prisms extending longitudinally along the cylindrical wall member and aligned at a selected prism angle of greater than 120 and less than 180 degrees wherein, depending on the selected prism angle, the wall member exhibits light piping via total internal reflection relative to radially aligned, high incident angle longitudinal light rays in planes parallel or near parallel to the prisms when the following condition is satisfied;

##EQU3## where β

=the selected prism angle

Th=the average thickness of the wall member

N₀ =zero or any positive integer

W=one half the width of each prism.

8. A hollow tubular light conduit for transporting light therealong and distributing light therefrom comprising:

a cylindrical wall member of a transparent material, the wall member having an average thickness (Th) defined by an inner smooth surface and an outer structured surface, the structured surface having a linear array of isosceles prisms arranged side by side thereon with faces of adjacent prisms extending longitudinally along the cylindrical wall member and aligned at a selected prism angle (β

), each prism having a width (2W), wherein the wall member exhibits light piping via total internal reflection relative to radially aligned, high incident angle longitudinal light rays in planes parallel or near parallel to the prisms based on the prism angle when one of the following conditions is satisfied;

Th=(N₀ +1/2)W×

tan(270-2β

), when 90°

<

β

<

120°

, or

β

=120°

, or ##EQU4## when 120°

<

β

<

180°

, where N₀ =zero or any positive integer.