Three-dimensional shape measurement beyond the diffraction limit of lens using speckle interferometry

Speckle interferometry is generally known as a method for measuring the deformation of an object with rough surfaces. In this paper, a three-dimensional (3D) shape measurement method is proposed for superfine structures beyond the diffraction limit using the basic property of speckle interferometry. Since the differential coefficient distribution of the shape of such an object can be detected in speckle interferometry by imparting a known lateral shift to the measured object, the shape can be reconstructed by integrating the differential coefficient distribution. Based on experimental results obtained using diffraction gratings as measured objects, it is confirmed that the proposed method can measure 3D shapes that are beyond the diffraction limit of the lens.