The Application And Analysis Of Sub-pixel Technology In Processing Moire Fringes In Long Focal Length Measurement System

In this dissertation, the properties of the moire fringes was analysised and verifyed under the conditions of the sub-pixel.And on the basis of that, a high-precision measurement algorithm of moire fringes’s inclination was proposed.According to the Talbot effect and moire fringes principle,There is a mathematical relationship between focal length of measured lens and the inclination of moire firnges.thus we can get the lens’s focal length by the inclination of the moire fringes.the commonly calculation method is fourier transformation of the moire fringes,and get the spectrum extreme point coordinates.For standard moire fringes.we can get the accurate coordinates of the extreme point by iterative algorithm.In order to accelerate the computing speed of the iterative algorithm.there is a information entropy algorithm was proposed by the distribution of the spectrum point in the frequency domain.For a curved moire fringes, the zeros algorithm and template algorithm were proposed, and we use CUDA technology to accelerate the computing speed by hardware.Through the theoretical analysis and experimental verification,these methods could satisfy the system’s accuracy requirements.The measurement algorithms have been developed.we have finished the theoretical analysis and algorithm argument of moire fringes.including the mathematical formula derivation.the research of spectrogram.the information entropy theory and some algorithms for curved moire fringes.Experiments data demonstrates that these algorithms works very well.