Optical: systems and elements – Holographic system or element – Having defined page composer
Patent
1994-08-04
1995-09-12
Ben, Loha
Optical: systems and elements
Holographic system or element
Having defined page composer
359 10, 359 22, 365125, 369103, G02B 532
Patent
active
054502187
ABSTRACT:
A method for encoding and decoding digital data for storage in a holographic medium (12). Digital data, consisting of binary data (B.sub.i) or grey scale data (A.sub.i), is encoded in bit groups or digit groups (B.sub.k, A.sub.k) containing at least k=1 bits or digits, respectively, by assigning to each bit group (B.sub.k) one reference bit (B.sub.r) and to each digit group (A.sub.k) two reference digits (A.sub.r1, A.sub.r2), assigning the bits of group (B.sub.k) to information bits (B.sub.j), assigning the digits of group (A.sub.k) to information digits (A.sub.j), assigning the reference bit (B.sub.r) and information digits (B.sub.j) to a reference pixel (P.sub.r) and information pixels (P.sub.j) chosen from pixels (24) of a holographic signal modulator (18), and assigning the reference digits (A.sub.r1, A.sub.r2) and information digits (A.sub.j) to reference pixels (P.sub.r1, P.sub.r2) and information pixels (P.sub.j) chosen from pixels (24) of the holographic signal modulator (18). Storing all pixels (24) by illuminating the holographic signal modulator (18) with a signal beam (22) which impresses upon the signal beam (29) pixels (24), guiding the signal beam (22) to the holographic medium (12) and storing the pixels (24) by directing a reference beam (26) at the holographic medium (12) from a predetermined angle .beta. and at a predetermined part of the holographic medium (12). Decoding the encoded binary data (B.sub.i) and encoded grey scale data (A.sub.i) by aiming the reference beam (26) at the holographic medium (12) at the same angle .beta. and location as during storage, recovering pixels (24) and recovering from them using a decoding unit (38) reference bits (B.sub.r) and information bits (B.sub.j) for each bit group (B.sub.k), and recovering reference digits (A.sub.r1, A.sub.r2) and information digits (A.sub.j) for each digit group (A.sub.k). Reconstructing the original binary data (B.sub.i) by differentiating the binary values of bits (B.sub.r) and (B.sub.j). Reconstructing the grey scale data (A.sub.i) by differentiating the reference digits (A.sub.r1, A.sub.r2) to obtain a benchmark (D.sub.r) and applying a binary operation on the benchmark (D.sub.r) and each of the information digits (A.sub.j).
REFERENCES:
patent: 3614191 (1971-10-01), Sakaguchi et al.
patent: 3871740 (1975-03-01), Matsubara et al.
patent: 4318581 (1982-03-01), Guest et al.
patent: 5121228 (1992-06-01), Paek
Bashaw Matthew C.
Heanue John F.
Hesselink Lambertus
Ben Loha
Board of Trustees of the Leland Stanford Junior University
McFarlane Thomas J.
Schuberg Darren E.
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