Backlit display with enhanced viewing properties

• US 5,381,309 A
• Filed: 09/30/1993
• Issued: 01/10/1995
• Est. Priority Date: 09/30/1993
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Borchardt, Jerry L.
• Primary Examiner(s): Lazarus, Ira S.
• Assistant Examiner(s): Sember, Thomas M.
• Application Number:
  US08/130,084
• Time in Patent Office: 467 Days
• Field of Search: 362/800, 362/26, 362/30, 362/27, 362/31, 362/331, 362/332, 362/333, 40/546
• US Class Current: 362/612
• CPC Class Codes: F21S 43/14 Light emitting diodes [LED]
• CPC Class Codes: F21S 43/40 characterised by the combination of reflectors and refractors
• CPC Class Codes: F21V 5/02 of prismatic shape F21V5/04 takes precedence
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G02B 6/0013 Means for improving the coupling-in of light from the light source into the light guide coupling light into light guides in general G02B6/42
• 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 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: G02B 6/0083 Details of electrical connections of light sources to drivers, circuit boards, or the like
• CPC Class Codes: G02B 6/009 of the light source in the package G02B6/0021 takes precedence
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side

Abstract

A high aspect ratio, backlit liquid crystal display in which light from opposing rows of light emitting diodes is projected into the ends of a thin optical cavity. The optical cavity is bounded by one major wall of which the interior surface is specularly reflective and an opposing major wall including a layer of transparent material having an interior surface formed with an array of regularly spaced, fine, triangular prisms which tend to collimate light received from the cavity and project it outwardly perpendicular to the major wall. A diffusion layer overlays the layer of transparent material, and a brightness enhancing film overlays the diffusion layer and functions to convert diffuse illumination received through the diffusion layer into directed illumination predominantly falling within the a viewing space bounded by predetermined angles.

Claims

1. A high aspect ratio, backlit display device with enhanced viewing properties, comprising:

a message carrying member having a display surface of predetermined length and width of which at least a portion is translucent, said message carrying member having a first side from which the message is to be readable within a viewing space bounded by predetermined angles relative to the first side, said message carrying member having a second side opposite the first side;

an optical structure having first and second generally parallel major walls at least partially enclosing a thin cavity having a length and width at least as great as the predetermined length and width of the display surface, the cavity having a first end substantially parallel with the width of the cavity and transverse to the first and second major walls thereof, the first major wall of said optical structure including an inner layer of transparent material having an interior surface bounding the cavity, an intermediate optical diffusion layer and an outer brightness enhancing film layer having an inner surface adjacent the diffusion layer and an outer surface adjacent the display surface, the interior surface of the inner layer and the outer surface of the outer layer each being configured with an array of regularly spaced triangular prisms parallel with the width of the cavity, the second major wall of said optical structure being adapted to provide specular reflection; and

a light source adapted to project light from the end of the cavity onto the second major wall of said optical structure in a direction transverse to the triangular prisms on the inner layer at a small angle relative to an interior surface of the second major wall.

2. The display device of claim 1 wherein said light source is adapted and oriented to produce a light beam whose center line intersects the interior surface of the second major wall at a point substantially 40 percent of the length of the optical cavity from the end thereof at which said light source is located.

3. The display device of claim 2 wherein said light source comprises first and second pluralities of light emitting diodes located at first and second opposing ends of the cavity respectively.

4. The display device of claim 3 wherein the first and second pluralities of light emitting diodes each comprise a linear array of light emitting diodes substantially parallel to the first and second major walls of the optical structure.

5. The display device of claim 4 wherein each of the diodes in the first and second pluralities of light emitting diodes produce a light beam having a half peak intensity aperture of substantially 15°

.

6. The display device claim 5 wherein said message carrying member is a liquid crystal display panel which is translucent when unenergized, and having a plurality of selectively energizable display segments which become substantially opaque when energized.

7. The display device of claim 6 wherein said optical structure is mounted on a printed circuit board with the second major wall of said optical cavity structure being adjacent printed circuit board, said optical structure being located between opposing rows of light emitting diodes carried on said printed circuit board and forming said light source, said printed circuit board also carrying electronic circuitry for selectively energizing the display segments of said liquid crystal display panel.

8. A high aspect ratio illumination source for backlighting a planar, at least partially translucent, display surface with directed illumination predominantly falling within a viewing space bounded by predetermined angles relative to the display surface, the display surface having a predetermined length and width, the light source comprising:

an optical cavity structure defining an optical cavity having opposite ends, and having a length and width at least equal to the predetermined length and width of the display surface, said optical cavity structure having a first major wall with an interior surface adapted to provide specular reflection and a second major wall including an interior layer of transparent material, the interior layer of transparent material having an interior surface configured with an array of regularly spaced triangular prisms extending across the optical cavity substantially parallel with the ends thereof;

a light source adapted to project light into the optical cavity from at least one end thereof;

a diffusion layer overlaying the exterior surface the interior layer of transparent material in the second major wall of said optical cavity structure; and

a brightness enhancing film overlaying said diffusion layer, said brightness enhancing film having a first surface adjacent said diffusion layer and a second opposing surface configured with an array of regularly spaced triangular prisms parallel with the triangular prisms formed in the interior layer of the second major wall of said optical cavity structure, the prisms on said brightness enhancing film having faces whose included angles and angular orientations relative to the first surface of said brightness enhancing film provide directed illumination predominantly between the predetermined angles bounding the viewing space.

9. The high aspect ratio illumination source of claim 8 wherein said light source is adapted to produce a light beam whose center line intersects the interior surface of the first major wall of said optical cavity structure at a point substantially 40 percent of the length of the optical cavity from said at least one end thereof.

10. The high aspect ratio illumination source of claim 9 wherein the light source comprises first and second opposing rows of light emitting diodes said opposite ends of the optical cavity, each light emitting diode producing a light beam having a half peak intensity aperture of substantially 15 °

.