# US 5,349,503 A · Illuminated transparent display with microtextured back reflector

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- Number: US 5,349,503 A
- Document ID: US5349503A
- Status: Granted
- Kind: A
- Application number: 08/052,320
- Filed: 1993-04-23
- Granted: 1994-09-20
- Earliest claimed: 1991-12-31
- Assignees: AT&T Bell Laboratories
- Inventors: Greg E. Blonder; Bertrand H. Johnson
- Web page: https://patentgrep.com/patent/US5349503A

## CPC

- G02B 6/0036: {2-D arrangement of prisms, protrusions, indentations or roughened surfaces}
- G02B 6/0061: {to provide homogeneous light output intensity}
- G02B 6/0065: {Manufacturing aspects; Material aspects}
- G02F 1/133553: {Reflecting elements (associated to illuminating devices G02F1/133605)}
- G02B 6/0051: {Diffusing sheet or layer}
- G02B 6/0055: {Reflecting element, sheet or layer}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS

## Abstract

Applicants have discovered that a particularly efficient illuminating device for a transparent display comprises a microtextured reflecting surface formed on a major surface of a transparent substrate and a light source for directing light into the transparent substrate approximately parallel to the major surface. Preferably the substrate has two major surfaces separated by a thickness in the range 0.5 to 1.0 mm so that the substrate acts as a light guide. A substantial portion of the light passing into the substrate undergoes total internal reflection until it hits a microelement and is reflected out of the substrate. The result is an efficient illuminating device particularly useful for lighting transparent displays.

## Claims

### Claim 1

An illuminating device comprising:
a transparent substrate comprising a pair of substantially parallel major surfaces;
one of said major surfaces comprising a plurality of spherical segments having smooth, continuous mold-formed surfaces and bases in the range 10-125 micrometers in diameter; and
means for directing light into said substrate in a direction generally parallel to said major surfaces.

### Claim 2 (depends on 1)

A device according to claim 1 wherein said major surfaces are spaced apart by a thickness of about 0.5 to 1.00 ram.

### Claim 3 (depends on 1)

A device according to claim 1 further comprising a diffusing sheet disposed parallel to said major surfaces.

### Claim 4 (depends on 1)

A device according to claim 1 wherein said spherical segments are coated with reflecting material.

### Claim 5 (depends on 1)

A device according to claim 1 wherein said spherical segments have altitudes which are 10% to 20% of the diameters of their bases.

### Claim 6 (depends on 1)

A device according to claim 1 wherein the combined areas of the spherical segment bases comprises 50 to 90% of the area of the major surface on which they are formed.

### Claim 7 (depends on 1, 2, 3, 4, 5, 6)

An illuminated display device comprising a transparent display device and an illuminating device according to claim 1 or 2 or 3 or 4 or 5 or 6.