Abstract
The prospects for gray-scale (or multilevel) digital holographic data storage are theoretically and experimentally investigated. A simple signal-to-noise ratio (SNR) partitioning argument shows that when SNR scales as 1 over the number of holograms squared, five gray levels would be expected to result in a 15% capacity increase over binary data pages. However, the additional signal-dependent noise sources present in practical systems create a baseline SNR that reduces both the optimal number of gray levels and the resulting gain in capacity. To implement gray-scale recording experimentally, we adapt the predistortion technique previously developed for binary page-oriented memories [Opt. Lett. 23, 289 (1998)]. Several new block-based modulation codes for decoding gray-scale data pages are introduced. User capacity is evaluated by an experimental technique using in the 90° geometry. Experimental results show that a balanced modulation code with three gray levels provides a 30% increase in capacity (as well as a 30% increase in readout rate) over local binary thresholding.
© 1998 Optical Society of America
Full Article | PDF ArticleMore Like This
Geoffrey W. Burr, Hans Coufal, Robert K. Grygier, John A. Hoffnagle, and C. Michael Jefferson
Opt. Lett. 23(4) 289-291 (1998)
Bhargab Das, Joby Joseph, and Kehar Singh
Appl. Opt. 48(28) 5240-5250 (2009)
Geoffrey W. Burr, Wu-chun Chou, Mark A. Neifeld, Hans Coufal, John A. Hoffnagle, and C. Michael Jefferson
Appl. Opt. 37(23) 5431-5443 (1998)