Terri A Laird

US Patent:

51775557, Jan 5, 1993

Filed:

Mar 28, 1991

Appl. No.:

7/676794

Inventors:

Mark D. Stratton - North Andover MA
Terri G. Laird - Salem MA

Assignee:

Digital Equipment Corporation - Maynard MA

International Classification:

G01L 124

US Classification:

356 355

Abstract:

A method and apparatus for optically determining the distribution of normal force present at the mating surfaces of an electrical surface connector uses the birefringent properties of a photoelastic material. Photoelastic members are distributed between the two planar surfaces, and plane-polarized, narrow-band wave-length light is coupled into each member with an optical fiber. The light is directed to propagate along a principle strain axis of the photoelastic member. The temporarily birefringent photoelastic material provides a relative propagation delay between vector components of the light in each member which are perpendicular to the propagation direction. The light exiting each member is input to a plane polarizer, the output of which is measured with an intensity meter. The relative delay between the vector components creates a detectable change in intensity at the intensity meter. Correlation of the measurements for all the photoelastic members give a distribution of the forces across the planar surfaces.