Abstract: The invention provides a method of triple-beam and triple-sensor in a laser speckle strain/deformation measurement system. The triple-beam/triple-camera configuration combined with sequential timing of laser beam shutters is capable of providing indications of surface strain and structure deformations. The strain and deformation quantities, the four variables of surface strain, in-plane displacement, out-of-plane displacement and tilt, are determined in closed form solutions.

Abstract: An improved method and apparatus for optically sensing and measuring physical quantities such as magnetic fields, electrical fields, mechanical strain, temperature, sound and pressure. The apparatus aspects of the invention involve a sensor structure consisting of a sandwich of magnetostrictive, piezoelectric or other materials sensitive to the physical quantity measured which are spaced apart by two opposed parallel reflecting surfaces located on opposing sides of the sensitive material. The reflecting surfaces can include an array of plane mirrors, diffraction gratings, curved mirrors, or retro-reflecting spheres. In its method aspects, multiple optical reflections between the two surfaces provide a magnified optical phase shift when the shape of the slab that is sensitive to changes in the applied field causes mechanical strains in the material. The changed optical signal can be measured by a suitable measurement device such as an interferometer for phase comparison with a diffraction reference pattern.

Abstract: A non-contacting optical imaging system for seam or other periodic pattern detection for a web of material such as a strip of fabric is disclosed in which a line scan camera is used to capture a seam or other periodic pattern image and the electrical output from the camera is converted to an alternating current signal and then to a direct current signal which is proportional to the presence or absence of a seam other periodic pattern. The DC signal is integrated and then compared to a preset reference value to produce a signal for driving an alarm, display or machine control devices.