Optical Fiber Straightedge
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
Optical fibers are manufactured with diametral tolerances of less than one micron per kilometer and a nearly perfect surface, making it possible for optical fibers to be used as a straightedge reference when combined with an LED (light-emitting diode). The fiber is stretched axially with a very high tension (i.e., 0.6 GN/m2) resulting in a strain of the order of 1%. At this value, sag and deformation of the fiber are maintained below 1.4 microns even when laterally accelerated at 100 g. In addition, by supporting it only at the ends, the possibility of distorting the reference when mounting it to a rigid surface is kept to a minimum. Vibrations of the fiber are of no consequence as long as the measurement system averages them over a large number of cycles. This can be taken care of in a servo loop filter.