Imaging Mechanism And Image Restoration Of Non-diffraction Beams

Nondiffracting beam has multiple characteristic, including the small size of centrallight spot, high strength, good direction, long transmission distance. It is widely used byresearchers in spatial straightness error of measurement, laser precision machining, lasertriangulation measurement, optical imaging In this thesis, using the axicon to producenondiffracting beam and this technical will be applied to ordinary imaging system,which is to achieve the purpose of the depth of field extension, This paper is mainly tostudy light imaging mechanism and optical image recovery of the nondiffracting beam.This article describes several methods of nondiffracting light generation andanalyses their advantages and disadvantages, respectively, and discusses the progress ofnondiffracting light, including engineering measurement, imaging characteristics,imaging mechanism, simultaneously, it analyses the significance of diffractive opticalimaging system being applied to the visual detection.Use generalized pupil function of Fourier optics theory to calculate generalizedpupil function of nondiffracting optical imaging system of axicon, so as to furthercalculate optical transfer function (OTF) and point spread function (PSF) of the limiteddiffraction system, and to analyze the effect which different defocus amount makes onthe PSF, and use the pinhole method to measure the point spread function of the systemto verify the correctness of the theoretical derivation.Three typical nondiffracting light imaging system is designed on the basis of thetheoretical derivation of the ZEMAX Optical Design Software. After add the axicon tothe initial system, and according to optimization goals which regard the minimalgeometric aberration as system, such as spherical aberration, coma and chromaticaberration and so on. By comparison, only based on the structure of the double Gauss,at the same time the depth of field being5times of the original system, then the cutofffrequency of the MTF curves will be100lp/mm.Double Gaussian structure of the diffraction-free optical imaging system designuses incidental analysis menu of the ZEMAX software to study, from such differentfield of view as the spot diagram aberration curves, MTF curves, analog imaging angle,the effect on the image quality of the imaging system in such different ways aswavelength,site, defocus amount.Finally, making an imaging experiment on the actual processing imaging systemand comparison with conventional systems on the line, people found that the depth offield of the system had a5-fold increase, but the images shot by the system is not clearand the contrast is low, which requires recovery of nondiffracting optical image. For theimaging characteristics of the axicon imaging systems, people propose nondiffractingoptical image restoration method based on superimposed with multiple images andmulti-scale Retinex. Image restoration results can meet online testing requirements.