Optical data carriers and reading devices therefor

Details Optical data carriers and reading devices therefor Optical data carriers and reading devices therefor

1995-12-13

1998-05-19

Neyzari, Ali

Dynamic information storage or retrieval

Storage medium structure

Optical track structure

369 4423, 369112, G11B 724

Patent

active

057545200

ABSTRACT:
An optical data carrier for use as a WORM memory contains memory cells where each memory cell is physically represented by a diffraction pattern. The content of each memory cell is a one bit information having a binary value "0" or "1". If a memory cell is altered by applying thermal energy it represents the complementary binary value. The unaltered memory cells are also used as security elements. This means that upon reading the content of an unaltered memory cell with a readout beam, the unaltered memory cell bends this reading beam into a plurality of different beams of predetermined outgoing directions. The intensities of these reflected beams are measured and compared with stored values. The data carrier is only then an authentic data carrier and not a fraudulent imitation, if the measured intensities of the reflected beams of such an unaltered memory cell lie within predetermined ranges.

REFERENCES:
patent: 4686663 (1987-08-01), Kuhn
patent: 5018127 (1991-05-01), Ando 369112

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