| Summary: | 博士 === 國防大學中正理工學院 === 應用物理研究所 === 91 === The study of holographically optical data storage and security by using the phase-coded multiplexing method are presented in this thesis. We have reinvented a new way of multiplexing; called “rotationally shifted random-phase encoded (RSRPE)” multiplexing. It is attempted to store holographic data in a photorefractive LiNbO3:Fe crystal. We can rotate and shift a circular holographic diffuser located in the reference beam of the holographic storage system as a random-phase modulator to provide a simple yet effective approach of increasing data storage capabilities. Experimental results showed that the proposed multiplexing method could also be combined with angular multiplexing to produce rotationally shifted random-phase encoded and angular (RSRPEA) multiplexing, thus offering higher data storage density and securing capabilities.
The defects of the Javidi’s encrypted optical memory angular multiplexing system are the loss of encrypted data, which is caused by the limited bandwidth and the imperfect phase conjugate beam reconstruction process. It can be corrected by mounting a lens with smaller f-number in the object beam and setting up the Sagnac interferometer in the reference beam path to improve the performances of the proposed Javidi’s system. The RSRPE multiplexing can also be integrated with the proposed Javidi’s system to become a triple random phase encoded system. Experimental results show that the system is safer and more reliable when the data page is recorded in the photorefractive LiNbO3:Fe crystal, and the decrypted process can only be attained when the photorefractive phase-conjugate beam is implemented.
In addition to proposing the RSRPE multiplexing system, the comparison problem of resolution; the storage of digital information; the mechanism of the phase modulation of the diffuser’s rotation and shift, and the disturbance of cross-talk between the inter-pages will also be studied in this thesis.
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