Fringe analysis is used in engineering fields as a precise measurement technology. In this paper, a method for improving the accuracy of spatial fringe analysis is discussed. A new method, based on fringe scanning and interpolation techniques, is put forward. Two-dimensional fringe analysis based on this new method is also proposed. Measured results obtained using the new two-dimensional method and those obtained using the FFT method are compared. Results showed that while the accuracy of the two methods is equivalent, the calculation time for the new method is five times as speedy as that for the FFT method.

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.