This paper analyzed the security of random phase encryption holographic storage technology. Taking binary random phase as an example, the recorded hologram is continually readout by series guessing reference. The experiment showed that the correlation coefficient between readout information and the recorded information was firstly decreased and then increased when the phase correct ratio of guessing reference is increased from 0% to 100%. The recorded information can’t be readout at all when the phase correct ratio of guessing reference range from 40% to 60%. Since the guessing reference with phase correct ratio between 40% and 60% has occupied majority guessing cases, the recorded information can’t be cracked in most cases. This indicates the high security of the random phase encryption storage technique.
A method for collinear non-interferometric phase retrieval holographic data storage using a single reference pixel is
proposed. The known embedded data of the signal beam in the traditional off-axis holographic data storage system is
placed in the reference beam through the collinear holographic data storage system, which greatly improves the material
utilization rate. And increasing the intensity of the reference beam can achieve phase retrieval using only one reference
pixel. As the intensity of the reference beam becomes stronger within a certain range, the number of iterations gradually
decreases. With this method, the phase retrieval can be achieved even when the total energy of the reference beam is less
than the signal beam. In the simulation, the four-level phase pattern was recorded and the phase was restored correctly.
The phase holographic storage system is different from the traditional object -image corresponding imaging. Because
of the particularity of phase, it is not easy to be captured by the traditional detector. Therefore, the Fourier lens is used
for Fourier transform to image it on the Fourier plane. The Fourier intensity is detected and the phase is recovered
iteratively by using the iterative Fourier transform algorithm. Due to the existence of aberrations, the wavefront phase
will be affected and the phase will be distorted.In this paper, we mainly study the influence of spherical aberration on
phase transformation. By establishing the light field with wavefront aberration, we study the influence of wavefront
aberration on phase recovery and propose the image restoration algorithm for aberration compensation .The feasibility
of the theory is proved.
KEYWORDS: Phase retrieval, Data storage, Holography, Fourier transforms, Computer programming, Solids, Data conversion, Reconstruction algorithms, Interferometry, Holographic data storage systems
Phase-modulation holographic data storage is imaging on the Fourier plane, and the imaging quality has a great influence on
phase retrieval. The iterative Fourier transform algorithm in the non-interference phase retrieval algorithm is widely used
because of its simple and stable system. By adding embedded data to the phase encoding method, the number of iterations can be
effectively reduced. However, the intensity of high-frequency information in Fourier intensity is weaker and more susceptible to
noise. To solve this problem, this paper proposes to use embedded data to improve the intensity of high-frequency information in
the Fourier intensity distribution, thereby improving noise immunity. In simulation, the convergence speed of BER (the bit error
rate) is faster under the same number of iterations.
The holographic performance of photo-polymeric material PQ/PMMA is found to be largely determined by pre-polymerization modulation, such as stirring time and pre-polymerization temperature, during the material preparation process. In the current study, in order to determine the best stirring time during the pre-polymerization process, the influence of stirring time on the holographic properties of PQ/PMMA here is seriously analyzed. Experimental observations clearly indicate that, under the same baking conditions, the diffraction efficiency of PQ/PMMA increase initially with the stirring time but then decrease as the stirring time continue increases. When the stirring time is 75 min, the holographic performance of PQ/PMMA reaches its best in which the diffraction efficiency of the material can reach up to 49.3%. Current study here determines the optimal stirring time and pre-polymerization temperature during the pre-polymerization process, thus provide an effective guidance for further preparation of PQ/PMMA photo-polymer materials with excellent holographic properties.
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