Research On Surface Microscopic Contour Detection Using Overlapping Imaging Techniques

Ptychography,which is a typical lensless optical imaging technology with simple structure,has the advantages of the extensible imaging range and high resolution.This paper proposes a detection method of surface micro topography based on ptychography and some relative researches were conducted.Starting from the basic principle of ptychography,it is proved that the phase retrieval can be realized by collecting many coherent diffraction patterns.By summarizing the characteristics and development of ptychography and studying the extended ptychographic iterative engine,a theoretical foundation was laid for the method.Based on light modulation from the surface topography,an improved ptychography optical system was designed by using the combination of variable aperture and lens to control the illumination field.The system can not only inspect the large region of surface micro topography,but also calibrate its feature size,such as step height.By taking a phase step plate as sample,the simulations are conducted to analyze the influence of step height and noise on the recovery result.The results show that the detection range of step height is less than 1.5?.We can realize a preferable sample reconstruction when the noise of diffraction patterns is less than 5%.A computer-generated holography(CGH)is reconstructed in the optical experiments.The recovery result of its surface micro topography is quite accurate and the error of step height is less 30nm compared with the result of white light interference detection.It verified the high detection precision and reliability of the method.On account of the scanning shift errors in the ptychography,an annealing algorithm to correct positioning errors was introduced.Simulation and experiment show that the algorithm can improve the resolution of the reconstruction results,the position errors can be reduced to the sub-pixel level.