Research On Improving The Resolution Of Incoherent Optical Coherence Imaging

As a common light source in our life,incoherent light can effectively avoid speckle noise and other problems caused by optical elements in coherent light imaging.The design of optical path can also trigger interference and holographic imaging of objects,which makes holographic technique applied in more areas.With the growth of technique,there are many techniques for recording holograms using Incoherent light sources.Among them,Fresnel Incoherent Digital Holography(FINCH)is a new recording method proposed in 2007.It is based on the correlation between object light wave information and Fresnel band plate to realize Incoherent Holography.By making the technology which has the function of multiplexing lens phase mask and loaded into the Spatial Light Modulator(Spatial Light Modulator,SLM),the implementation of the incident Light wave field phase modulation,achieve the goal of diffraction spectroscopy and phase shift,can be obtained with different phase shift of the hologram,and combines the technique of phase shift in the process of reproduction get rid of the influence of coaxial twin like brought by the holographic.Based on the study of the incoherent holographic imaging system,the effects of the characteristics of the main components and the corresponding parameters on the resolution of hologram recording and reconstruction are analyzed theoretically and experimentally,and a general optimization method is given.This paper principally carries out the research from the following aspects:(1)The basic principle of incoherent optical coherence imaging is studied.The expressions of point spread function,transverse magnification and reconstruction distance of finch imaging system are derived.The effect of phase-shifting technology in in-line holography is described.The phase-shifting constant can be introduced into the spatial light modulator to eliminate the zero order image and conjugate image in in-line holography to improve the imaging quality.The application conditions and scope of convolution algorithm,angular spectrum algorithm and Fresnel diffraction algorithm used in hologram reconstruction are analyzed.(2)The effect of recording parameters on the imaging resolution of finch imaging system is studied theoretically.By changing the mask focal length and recording distance of SLM in two modes of loading plane wave,spherical wave and double spherical wave,the relationship between optical path difference and temporal coherence length is studied.The coherence condition can be satisfied by optimizing the parameters,so as to improve the resolution of imaging system;When the system parameters meet the coherent condition,the numerical aperture size is mainly considered.The optimal resolution of the imaging system is the parameter corresponding to the maximum numerical aperture when the coherent condition is satisfied;This paper discusses the requirement of the sampling frequency of the image detector on the recording distance,analyzes the limitation of the target area and pixel size of the detector on the hologram radius,and then discusses the influence of the hologram radius on the resolution.(3)The FINCH imaging system was experimentally studied.The experimental optical path was designed and the phase mask loaded on the spatial light modulator was fabricated.The effects of the focal length and recording distance of the phase mask on the resolution of the system are studied by computer simulation and experimental operation.