Patent ID: 6486962
Filing Date: 2002-11-26
Classification: G01H,G01N

Abstract:
A method for assessing a material property of a sheet-like material, comprising:vibrating the sheet-like material to produce at least one traveling wave therein; directing an object wavefront toward the vibrating sheet-like material so that said object wavefront is modulated by the vibrating sheet-like material to produce a modulated object wavefront; modulating a reference wavefront in synchronization with the vibrating sheet-like material to produce a modulated reference wavefront so that a difference frequency between the modulated object wavefront and the modulated reference wavefront is within the response range of a sensing medium; combining the modulated object wavefront and the modulated reference wavefront within the sensing medium to produce an output beam that contains an image of the traveling wave in the sheet-like material, the image of the traveling wave being related to a displacement amplitude of the traveling wave over a two-dimensional area of the vibrating sheet-like material; detecting an image of the traveling wave in the vibrating sheet-like material; and assessing the material property of the vibrating sheet-like material based on the detected image of the traveling wave.