Light fixture providing normalized output

• US 4,791,540 A
• Filed: 05/26/1987
• Issued: 12/13/1988
• Est. Priority Date: 05/26/1987
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Strand, Neal T., Dreyer, John F. Jr.
• Primary Examiner(s): Lazarus, Ira S.
• Assistant Examiner(s): Hagarman, Sue
• Application Number:
  US07/053,848
• Time in Patent Office: 567 Days
• Field of Search: 362/309, 362/31, 362/97, 362/33, 362/23, 362/26, 362/29, 362/30, 362/339, 362/223, 362/224, 362/329, 362/245, 362/331
• US Class Current: 362/331
• CPC Class Codes: F21V 3/00 Globes; Bowls; Cover glasses with refracting properties F21V5/00; with reflecting properties F21V7/00; characterised by cooling arrangements F21V29/506
• CPC Class Codes: F21V 5/005 using microprisms
• CPC Class Codes: F21V 5/02 of prismatic shape F21V5/04 takes precedence
• CPC Class Codes: F21Y 2103/00 Elongate light sources, e.g. fluorescent tubes
• CPC Class Codes: G03B 21/132 Overhead projectors, i.e. capable of projecting hand-writing or drawing during action epidiascopic projectors G03B21/08

Abstract

A light fixture providing normalized output. An undirected light source is located in an optical cavity having an optical window. A film with a smooth surface and a structured surface is placed in the optical window with the smooth surface facing the interior of the optical cavity. The structured surface has a plurality of triangular prisms thereon.

Claims

1. A light fixture having normalized light output comprising:

a case defining a first optical cavity, said optical cavity having an optical window;

a first light source in said optical cavity;

a first transparent film having first and second major surfaces in said optical window, said first major surface being smooth and facing into said optical cavity and said second major surface having a plurality of triangular prisms thereon, each of said triangular prisms having a major axis, said major axes of said prisms being parallel to one another;

a case defining a second optical cavity having a first input optical window and an output optical window, said second optical cavity input window accepting light exiting said first optical cavity through said first optical cavity optical window; and

a second transparent film having first and second major surfaces in said optical window, said second transparent film first major surface being smooth and facing into said second optical cavity and said second transparent film second major surface having a plurality of triangular prisms thereon, each of said triangular prisms having a major axis, said major axes of said prisms being parallel to one another and perpendicular to said major axes of said prisms of said first transparent film.

2. The light fixture of claim 1, wherein said light source is an extended linear light source having a major axis and said major axes of said triangular prisms are perpendicular to said major axis of said first extended linear light source.

3. The light fixture of claim 1, further comprising a light diffusing film in said second optical cavity output optical window adjacent to said second transparent film second major surface.

4. The light fixture of claim 1, wherein said second optical cavity has a second input optical window said light fixture further comprising:

a case defining a third optical cavity having an optical window;

said second optical cavity second input optical window accepting light exiting said third optical cavity through said third optical cavity optical window;

a second light source in said third optical cavity; and

a third transparent film in said third optical cavity optical window, said third transparent film having first and second major surfaces, said third transparent film second major surface having a plurality of triangular prisms thereon, each of said triangular prisms having a major axis, said major axes of said prisms of said third transparent film being perpendicular to said major axes of said prisms of said second transparent film.

5. The light fixture of claim 4 wherein both of said light sources are extended linear light sources.