Detection of Surface Asperities on Film Substrates
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Asperities in biaxially oriented films produce a birefringent strain pattern which is detected by placing the film between crossed polarizing filters in a transmitted light beam. The height of the asperities is sensed by pressing the film against an optical flat glass surface with a reflected monochromatic light source. The number of the interference fringes is directly proportional to asperity height.