Self-referenced Incoherent Digital Holographic Imaging

Incoherent digital holography is an attractive technology as it dispense with thedependence on coherent light source. Thus the incoherent holographic imaging hasbeen applied to the three-dimensional fluorescent microscopy, white light colorholographic display and holographic adaptive optics. The hologram of a point-objectoriginating from an incoherent extended object can be formed based on spatialself-coherence of the beams by suitable optical beam-splitting technique. Thehologram of the extended object is the incoherent superimposion of allpoint-holograms. Three-dimensional information of the spatially incoherent object canbe retrieved by the numerical reconstruction of the hologram which is captured by acharge coupled device (CCD). Recently, the research about the basic principle,performance improvement and novel applications of the incoherent holography areactive and have been paid more and more attentions in the world.The topic of this thesis is about the investigation on key problems ofself-referenced incoherent holography. The investigations are focused on thefollowing five aspects: the comprehensive evaluation and optimization of the systemresolution, the compensation of the phase-shifting errors, the quantitative evaluationof the spatial coherence of light source, implementation of the incoherent off-axiscommon-path digital holographic recording and the combination of the incoherentdigital holography and spectral imaging to achieve multi-dimensional informationrecording and reconstruction. Some novel methods and algorithms were proposed andverified through experiments and simulations. The main researchs are summarizedand described as the following:1. The basic principle of the self-referenced incoherent digital holography isinvestigated. Some characteristics of the incoherent holography are analyzed incontrasting to conventional coherent holographic imaging system. In incoherentholography, the hologram of an extended object is the incoherent superimposion of allpoint-holograms. The phase shifting technique is introduced for eliminating the twinimage and the zero-order in in-line incoherent holography is introduced. Furthermore,some numerical reconstruction algorithms are analyzed. 2. The imaging performance of Fresnel Incoherent Correlation Holography(FINCH) is investigated theoretically and experimentally. Based on the scalardiffraction theory, analytical calculation of the Point Spread Function (PSF) for boththe optical recording and digital reconstruction are presented. And the magnificationand resolution of the system are also demonstrated. It is demonstrated that theimproved resolution can be obtained by FINCH comparing with coherent andincoherent conventional imaging system. Furthermore, the numerical aperture of therecorded Fresnel point-hologram is introduced as a comprehensive parameter for bothevaluating and optimizing the imaging characteristics in the FINCH scheme. Anoptimal numerical aperture of the hologram is achieved by implementing anappropriate phase mask for a given recording distance between the spatial lightmodulator (SLM) and the CCD. Optimized imaging resolution and signal to noiseratio (SNR) are demonstrated experimentally.3. A compensation algorithm of phase-shifting error in incoherent digitalholography is developed and used to improve the reconstruction image quality. Thephase modulation characteristics of the SLM are measured quantitatively when theSLM are illuminated with laser and quasi-monochromatic narrow-band thermalextended light source respectively. Combining with analytical calculation andsimulations, the phase shifting error which is introduced by the non-linearitycharacteristics of the SLM is investigated. A new phase shifting error compensationalgorithm based on evaluating the Mean Contrast of Noise (MCN) of thereconstructed image is proposed. The reconstructed image quality can be improvedeffectively by applying the algorithm.4. The spatial coherence of the light field is measured quantitatively by a novelmethod of twin-beams interference in the triangular interferometer. The spatialcoherence can be measured independently from the complex coherence, as the effectof the temporal coherence has been minimized by the common-path optical setup ofthe interferometer. The experimental setup is effective, simple and robust.Experimentally measured and theoretically calculated results of spatial coherence fitwell and the error is only3.8%.5. The common-path off-axis Fourier incoherent holography is developed andimplemented. To overcome the limitation of the slow recording speed of the common-path in-line incoherent holography, we present a new technique ofIncoherent off-axis Fourier Triangular Holography (IFTH). Single exposure issufficient to retrieve the3D information of the objet. The recording properties,3Dreconstruction ability, imaging resolution and magnification of the proposed imagingsystem are investigated theoretically and experimentally.6. Four-dimentional recording and reconstruction are achieved by the proposedIncoherent Fourier Triangular Color Holography (IFTCH), which combines the IFTHand spectral imaging technology. Three holograms are sufficient to rebuild a colorimage. Combined with some image fusion skills during reconstruction, thereconstructed color images with satisfied quality are demonstrated. The proposedmethod shows it great potential in some practical applications such as3D spectralimaging, color holographic imaging for dynamic samples and the3D fluorescentspectral imaging.