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Proceedings Paper

Novel modulation techniques for collinear holographic data encoding
Author(s): Wei Jia; Zhongyu Chen; Tsing Chung; Fung Jacky Wen; Yuk Tak Chow; Po Sheun Chung
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Paper Abstract

We describe two novel modulation techniques for collinear holographic data encoding, employing a spatial light modulator (SLM) based on twisted nematic LCD. In the Fourier transform holographic storage system, the reference beam in the outside part and the object beam in the inside part are simultaneously modulated by one single SLM, with different modulation techniques. In one of the modulation methods, the reference beam is phase modulated with a circular blazed grating pattern, and then diffracted into the central part to interfere with the amplitude modulated object beam. Multiple holograms can be recorded on the same location with reference beams of different grating period. Another modulation method is to modulate both the reference beam and the object beam with pure phase modulation by the SLM. The binary ones are encoded with random phase shift from 0 to 2π, while the binary zeroes are encoded with a constant phase of 0. When the dc component of the spatial frequency generated by the binary zeroes is blocked, a homogeneous hologram will be obtained, and the amplitude object will be reconstructed directly. In this paper, both of the two modulation methods are performed theoretically and experimentally. From the experimental results, it can be seen that the blazed-grating modulation technique gets a higher efficiency, while pure phase modulation method can reconstruct the images with more uniform intensity. These techniques are demonstrated to be attractive for applications in data storage and encryption systems.

Paper Details

Date Published: 10 February 2012
PDF: 7 pages
Proc. SPIE 8281, Practical Holography XXVI: Materials and Applications, 82810M (10 February 2012); doi: 10.1117/12.905014
Show Author Affiliations
Wei Jia, City Univ. of Hong Kong (China)
Shanghai Institute of Optics and Fine Mechanics (China)
Zhongyu Chen, City Univ. of Hong Kong (Hong Kong, China)
Tsing Chung, City Univ. of Hong Kong (Hong Kong, China)
Fung Jacky Wen, City Univ. of Hong Kong (Hong Kong, China)
Yuk Tak Chow, City Univ. of Hong Kong (Hong Kong, China)
Po Sheun Chung, City Univ. of Hong Kong (Hong Kong, China)


Published in SPIE Proceedings Vol. 8281:
Practical Holography XXVI: Materials and Applications
Hans I. Bjelkhagen; V. Michael Bove, Editor(s)

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