Structured Illumination Based On Fresnel Diffraction And Its Application In 3D Sensing

In 3D sensing system which is based on structured illumination, the method and setup for generating structured illumination are very important to obtain correct and effective 3D reconstruction. Two ways to generate structured illumination have been widely studied. They are projection system based on imaging law and double-beam interference based on interference law. However, the method based on diffraction to generate structured illumination has hardly been studied.In this thesis, we present the law and method to generate structured illumination based on Fresnel diffraction. By applying RSD theory, we analyzed the spatial distribution of Fresnel diffraction field of sinusoidal grating and its available application in 3D sensing. When diffraction problems are solved by the angular spectrum theory, high speed and high accuracy can be obtained, especially for near-field Fresnel diffraction. Here, the spatial distribution of Fresnel diffraction field and different Talbot effects of sinusoidal grating are presented, under three different illuminating conditions. Especially, we discussed some interesting properties about Fresnel diffraction field and Talbot image, when sinusoidal grating is illuminated by divergent spherical wave. Such as, the amplifying effect on the field of divergent spherical wave, the condition of Talbot effect to be observed, etc.Based on the study of the law and method to generate structured illumination, which is derived from Fresnel diffraction law, this thesis offers a structured illumination scheme that is applicable to 3D sensing system. Also, computer simulation and 3D shape measurements of real objects are presented. They both prove the correctness and effectiveness of the law and method given in this thesis. All results obtained in this thesis show: structured illumination based on diffraction law, especially based on Fresnel diffraction law, has some distinctive properties. Such as the structured illumination field has wide view and measuring range, simple setup, easy to be adjusted, etc. So, applying structured illumination based on Fresnel diffraction in 3D sensing system, that is of significant meaning and great application value.