Large-area light source

• US 4,277,817 A
• Filed: 06/13/1979
• Issued: 07/07/1981
• Est. Priority Date: 06/23/1978
• Status: Expired due to Term

• Current Assignee: Blaupunkt-Werke GmbH (Aurelius AG)
• Original Assignee: Blaupunkt-Werke GmbH (Aurelius AG)
• Inventors: Hehr, Wilfried
• Primary Examiner(s): Lechert, Jr, Stephen J.
• Application Number:
  US06/048,040
• Time in Patent Office: 755 Days
• Field of Search: 362/31, 362/26, 362/354
• US Class Current: 362/628
• CPC Class Codes: F21V 5/02 of prismatic shape F21V5/04 takes precedence
• CPC Class Codes: G02B 5/0221 the surface having an irregular structure G02B5/0226 takes precedence
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G09F 9/00 Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the variable information is permanently attached to a movable support G09F11/00; abacus G06C1/00; slide-rules G06G1/00

Abstract

To provide for uniform output throughout the area of the light source, particularly to provide a background illuminating surface for liquid crystal display, an especially adapted for automotive application, the light-emitting surface is formed as a wedge-shaped body of transparent material, such as Plexiglas, with light being coupled thereinto at the wider side surface, the bottom surface of the wedge-shaped body having, preferably, a reflective, light dispersing layer or coating applied thereto, for example in form of a white pigmented lacquer, white paper, a ceramic plate, or the like; an intermediate layer of light-transmissive material having an index of refraction less than the index of refraction of the body may be interposed between the surface of the body and the reflective coating of layer. The top surface of the body can be matte, for example formed by microgrooves extending transversely to the plane of the side surface through which light is coupled into the wedge-shaped body. The light can be coupled thereinto derived, for example, from an incandescent bulb.

Claims

1. Large-area light source comprising

a light-transmissive body (1), a form of a thin wedge having an essentially flat, light-emitting surface and being of essentially rectangular cross section, adapted to be exposed to a visible radiation source at one side surface,

the wedge shaped light transmissive body has two major surfaces (2,3), which are inclined with respect to each other, one of said surface (2) forming the light-emitting surface.

the side surface (4) which receives the visible radiation (A) is a surface which is angled off from said one, or light-emitting surface (2) and joins said one light-emitting major surface (2) to the other major surface (3) at an essentially right-angle junction with respect to said other major surface (3),

and a thin, light-transmissive layer (7) is provided coating said other major surface (3) opposite the light-emitting surface of the wedge-shaped body (1), the optical index of refraction of said layer (7) being less than the optical index of refraction of the material of the wedge-shaped body (1);

and a light-dispersing, light-reflecting pigment coating or layer (8) is provided, covering said light-transmissive coating or layer (7).

2. Light source according to claim 1, wherein the light-transmissive coating or layer (7) comprises a coating of clear lacquer, and the light-dispersing and reflective coating or layer (8) comprises an essentially white coating of lacquer applied to the clear lacquer coating (7).

3. Light source according to claim 1, wherein the light-emitting surface (2) has a surface which is matte.

4. Light source according to claim 3, wherein the light-emitting surface (2) is formed with a plurality of essentially uniformly located microgrooves (9) which extend transversely to the side surface (4) which receives the visible radiation (A).