Real-time And Exact Phase Reconstruction Technology In Digital Holographic Microscopy

Digital holography is a characterization of three-dimensional micro-structure andmeasurement technique, with advantages of non-contact, real-time, high sensitivity,high precision, high resolution and whole-field, which achieved high degree ofintegration about optical, optoelectronic technology and computer technology. Recently,Digital holographic microscopy(DHM) has been used successfully, but there are alsomany problems, such as the resolution is not high, the real-time reconstruction is quitelow, the phase reconstruction accuracy not enough high and so on, which is hot indigital holography research, and is also the important questions to be solved in thispaper.Based on theoretic analysis, computer simulation and experiment, this paper focuson the following aspects mostly:1. Firstly, the recording and reconstruction process of digital microscopyholography are analyzed. The three common linear reconstructed algorithms whichbased on the fast Fourier transform are introduced, the advertages are also explained.2. In order to achieve high resolution imaging by cutting down the expense ofdigital holographic microscopy system, the recording and reconstruction process ofimage-plane digital holographic system(IPDHS), its point spread function and theimaging characteristics are analyzed. In the same way, pre-magnification digitalholographic microscopy system is analyzed. It is concluded that IPDHS is a optimizedholographic recording system, which can realize to record the message completely, thedependency of lateral resolution of IPDHS on the photosensitive surface size of therecording device and pixel size are very weak,which is completely different from thecommon knowledge that the lateral resolution of pre-magnification digital holographicimaging system can be improved by using large size recording device.3. According to avoid the shortage of digital holography reconstructed algorithm ofthe accuracy and the speed of reconstructed image, the digital holographic generalizedlinear reconstructing algorithm based on homomorphic signal processing is proposed.The results show that the zero order term of digital hologram frequency spectrum can beeliminated effectively by the proposed algorithm so as to realize the high-precisionreconstruction of the digital hologram. Because a whole quadrant is chosen as the filtered area, the manual frequency filtering operation needed in common linearreconstructing algorithm is avoided and then the reconstructing speed is improvedgreatly. Meanwhile, the high-frequency component of the reconstructed original imagecan be reserved up to the hilt so that the high resolution image can be achieved.Thenanalysis the influence of different ratio of object and reference in same field withgeneralized linear reconstructing algorithm.4. In order to recover the noisy wrapped phase map rapidly and accurately, the fourtypical algorithms based on fast Fourier transform, such as the algorithm of the fourtimes fast Fourier transform (4-FFT), the quadratic fast Fourier transform (2-FFT), thefour times discrete cosine transform(4-DCT) and the algorithm based on thecombination of lateral shearing and Fourier transform(LS-FFT), are compared throughtheoretical analysis, computer simulation and experimental verification.