Calculation And Acceleration Of 3D Diffracted Light Field By Point Cloud Method

Holographic display not only provides a 3D image that is almost identical to the real world,but also fully communicates all the deep stimuli of human perceived from 3D objects,which will be the ultimate goal of 3D imaging and display.A video imaging system includes several functional parts:acquisition,compression,transmission and display.Among them,acquisition is a very important step.Compared with the traditional optical holography,the method of calculating the hologram for digital holography has the advantages of low environmental requirement and high flexibility,and can directly encode the mathematical description of the light wave.However,the calculation of the diffraction field involves fundamental problems such as signal processing and optical theory,and still faces many challenges,it is the current research hotspot to explore the method of reducing the computational complexity of diffraction field and explore the corresponding discretization criterion.Computational holography covers plenty of signal.processing problems,for example,the Fresnel kernel is neither band nor limited in space,but it can still recover a complete Fresnel diffraction field from their finite samples.According to the Wigner distribution analysis,the coherent coding of the signal contains more information required for reconstruction than the non-coherent coding.Thus,on the one hand,in order to produce a vivid 3D image,it should be calculated that the scalar diffraction form of the binomial expansion of the Fresnel(rather than the Fraunhofer),and the high spatial bandwidth product and the binomial order of the complex diffraction field poses a huge challenge to calculating the holography.On the other hand,the coherent Fresnel diffraction field has some properties used as the basis for accelerated calculation.There are many methods to calculate Fresnel.Based on the point cloud method,the method of calculating Fresnel diffraction field is studied.Firstly,an indirect calculation method is given by investigating the sampling problem of diffraction field and combining the reversibility of Fresnel diffraction propagation in propagation direction.Secondly,through the study of the method of look-up table and the spatial symmetry of Gabor band or Gabor lens,the original look-up table method is improved and the calculation efficiency is improved.The main contents and innovations of the thesis as follows:(1)According to the sampling standard of the point cloud algorithm and the reversibility of Fresnel propagation,a two-step calculation method is given,the sampling distance between the source scene and the holographic surface can be set independently.In the actual calculation process,the distance between the source scene and the holographic surface is set as a different sampling spacing according to the requirement,so as to in the premise of ensuring the effect of eye observation,increasing the source scene sampling distance,reducing the number of cloud point,improving the efficiency of calculation.(2)Based on the novel look-up table method,a new method of calculating the main fringe pattern is proposed.The novel look-up table method is used to calculate the main fringe pattern,which is usually set to the calculation of coaxial holographic,and the sample point and the central position of the holographic surface is on the z axis,and by combining with the symmetry of the hologram,only one a symmetric region of hologram is calculated for each calculation,and the other positions can be obtained directly through the symmetry.This method can greatly reduce the repetitive calculation during the calculation of the principal fringe pattern and improving efficiency of the calculation.