OPTICAL METHOD OF DETERMINATION OF STRESS AT A POINT

A method of determining stress at a point is suggested here. The effec t of bending of a wave front that is due to variations of the refracti ve index is used to measure different aspects of stresses. A Fourier l ens with a cross slit at its front focal plane is used to form interfe rence fringes at planes near its back focal plane. The sample, illumin ated by a plane-parallel coherent beam of light, is placed close to a cross slit, and the change in fringe pattern due to axial shift of the spectrum planes of the slits is measured to relate it to the state of stress. (C) 1997 Optical Society of America.