Research On Key Technologies Of Self-interference Digital Holography

Interference is one of the wave characteristics of optical field.A series of optical technologies based on optical interference principle are an important part of modern science and technology,among which holography is a typical representative of applications of interference principle.According to the object-image relation of optical lens,the conventional photography only records the intensity of optical field(i.e.the amplitude of light),and because of the loss of phase information,it loses the ability of 3-D imaging of object.Based on the interference of light,holography records the amplitude and phase information of object in the form of interference fringe(i.e.hologram),and when the hologram is reconstructed by optical or digital diffraction,the wavefront of the object can be reproduced to form a lifelike 3-D image of the original object.The research of holographic principle and the development of its technology are closely related to two aspects,on the one hand,the hologram recording cannot be separated from the coherence of optical field,moreover,it is the key reason for the rapid development of holography with the advent of highly coherent laser source.However,the requirement of coherent illumination for holographic recording has limited the application and popularization of holography.How to reduce the coherence requirement for hologram recording is one of the important directions in the development of holographic technology.On the other hand,as one of the basic properties of optical field,the coherence determines the behavior of optical field,and the recorded hologram also contains the coherence information of optical field.Therefore,developing new principles and technologies of holography and studying the coherence of optical field which is closely related to holography are important research topics in the field of optics,and they also constitute the main research contents of this thesis.With the progress of modern digital technology,the integration of optical technology and digital technology has become an inevitable trend,and digital holography has become one of the most promising imaging technologies.Digital holography is receiving extensive interest not only due to the everlasting quest to quantitatively characterize complex 3-D light field,but also owing to the state of the art advances,which enables the high-sensitive and high-resolution recording as well as the fast digital reconstruction of hologram,particularly in the areas of material detection,particle tracking,bio-microscopic imaging and medical imaging and so on.In particular,digital holography,which allows incoherent light illumination and is developed with the aid of the new wave-front modulation technology,has attracted people's attention in the past 10 years.Among various schemes,a kind of recently proposed digital incoherent holography,which is generally referred to as the self-interference digital holography(SIDH),is particularly attractive.Especially,the optical configuration,with incoherent illumination,small optical path difference,on-axis channel and nonmechanical scanning,makes SIDH be very appealing and competitive in the field of optical science and technology.Due to theoretical importance and potential applications of SIDH,the extensive works need to be further carried out,and some essential issues remain to be clarified.For instance,Fresnel incoherent correlation holography(FINCH)is a new type of SIDH,however,there are different statements about the FINCH configuration that is required to achieve the optimal lateral resolution.With the development of laser technology,the performances and requirements of laser beam are becoming more and more diverse,and then,it is becoming a key issue how to modulate the optical field.In recent years,because of the development of technology and theory of modulating the correlation function of light beam,the coherence of optical field has been paid more and more attention,and becomes a new degree of freedom for modulating the optical field,moreover,some optical fields with special spatial correlation functions have been proposed.Therefore,it becomes an urgent problem how to quickly and accurately measure the two-dimensional distributions of these special spatial correlation functions,which is also one of the main research contents of this thesis.The main contributions addressed in this thesis are as follows.1.On the basis of the theory of wave optics,according to the characteristics of FINCH hologram,namely the feature of zone-plate-like pattern,we propose a model of the effective aperture of hologram from the pixelation effect of digital devices.We find out that the optimal lateral resolution is achieved when Z_h=f_d,and the resolution is deteriorated with the increase of |Z_h-f_d|.2.With the aid of the empirical mode decomposition of Hilbert-Huang transform,the conventional phase-shifting algorithm is improved,which can effectively suppress the influence of bias noise on the reconstruction image of SIDH.According to the modified phase-shifting formula,the new algorithm is based on the superposition of the original multi-phase-shifting holograms,so,it can effectively preserve the information of the original signal,and suppress the bias noise of the hologram.3.Based on the theory of statistical optics,using Gaussian Schell-model(GSM),we focus our attention on the impact of the spatial coherence on the final image of SIDH.In this work,we have found that it is the optical configuration as well as the spatial coherence of source that promotes the formation of cross-correlation image,moreover,the physical properties of cross-correlation image,such as number,location and strength,show very significant dependence on the recording distance of hologram.4.According to the statistical properties of speckle,we have proposed a new scheme which can measure the two-dimensional distribution of spatial correlation function of partially coherent optical field.The principle of the proposed scheme is that the operation using Fourier transform plus intensity-correlation algorithm is performed on speckle pattern to calculate the second-order correlation function of amplitude from the fourth-order correlation function of intensity,namely,by spatial average instead of ensemble average.