Research On Lensless Wavefront Division Digital Holography

Despite rapid progress in the field of optical imaging,most advanced microstructure imaging measurement equipment still suffers from complex structures and high costs,which limits their use outside well-equipped laboratories.At the same time,the observation methods used in resource-constrained environments and advanced and complete laboratories should have significantly different positioning and requirements.Such imaging equipment in a resource-constrained environment should have the characteristics of low cost,small size,light weight,appropriate accuracy,and easy operation and use by ordinary people without training.The purpose of this subject " Research on lensless wavefront division digital holography " is to try to design a portable optical path structure that suitable for resource-constrained environments and featuring low cost and easy operation.The specific research contents of this article are as follows:First,the principle and method of recording and reconstruction of off-axis digital holography are studied.At the same time,the off-axis digital holographic recording conditions based on two spherical lights are emphasized.Then the simulation shows that the advantages of the dual-wavelength unwrapping algorithm over the single-wavelength unwrapping algorithm.This chapter lays a basic theoretical basis for subsequent research.Secondly,a portable lensless off-axis digital holograph based on the wavefront division is proposed.The structure has the characteristics of low cost,portable,friendly sample operation,and easy implementation.In the reconstruction process,a division algorithm is introduced to remove the spherical aberration caused by spherical light to improve the imaging quality.The performance characteristics of the structure are fully described by the resolution determination experiment,quantitative phase imaging experiment,dynamic observation experiment,and time stability and repeatability experiment.Third,the dual-wavelength digital holography is combined with the proposed structure.It is used to increase the axial measurement range of the system to avoid the time-consuming calculation of phase unwrapping.Quantitative phase imaging of samples with high step shows that in the situation where the phase unwrapping algorithm fails,the dual-wavelength technique can effectively measure high step samples within its measurement range.The dynamic performance of the dual-wavelength digital hologram is experimentally demonstrated.Compared with the dual-wavelength digital hologram which is taken twice,the single exposure dual-wavelength digital hologram acquisition method can realize the observation of dynamic samples.Finally,the proposed portable optical path structure is integrated so that it is truly out of the laboratory and can make the required observations in a resource-constrained environment.