Floating Displays

Bernhard Gerl

Floating Displays

Faceplates made of glass fibers improve the readability of digital displays and reduce scattered light.

The object lying on a sheet of paper that contains print appears to be a perfectly normal glass block. But, somehow the printing underneath it looks as if it is swimming on the surface of the glass. The reason is that the block is made up of many millions of glass optical fibers. Each and every one of them guides the incident light from the outside surface down to the print material first. Then, the image is transferred back to the surface of the fiber optic.

These types of faceplates are made using multiple steps in a closely controlled clean room manufacturing process. First, round or polygonal glass rods are created. These glass rod cores are approximately 3 by 3 centimeters in cross-section and one meter in length. They are then inserted into an optical cladding and heated up to their softening point. Then, their viscous ends are stretched together in length. This results in individual fibers that are two millimeters thick. After they have been cleaned, many of these fibers are bundled together to form a 3 x 3 centimeter block. These are then heated up and drawn again, resulting in a fused fiber strand with approximately 150 to 200 individual fibers. The procedure is then repeated once again. The final product is a so-called multi-multi fiber bundle that is only two millimeters thick with many thousands of glass fibers only two to six microns in thickness.

In order to manufacture larger optical components from these, they are bundled parallel to each other in the form of a block. Then, they are bonded together by subjecting them to pressure and high temperatures so that the outer casing of the individual fibers softens and fuses together into a solid block or boule. Disks of fiber optic material are then cut out of this block in the desired thicknesses and milled, ground and polished into their final shape. Faceplates made from glass fibers are currently being used as cover panels for CCD image sensors in professional digital cameras, for example. They successfully protect the surfaces of chips from being damaged, hold off X-rays and deliver light to sensors more effectively than lenses. Other areas of application include night vision devices and medical X-ray systems with electronic image processing. In the future, they will also be used as cover plates for demanding display applications, such as ruggedized PDAs and other display devices that require privacy for the user or limited side illumination for reduced reflections and security.