Direct measurement of optical phase is used in a high-density optical disk reader. The increased density is achieved by introducing multiple pit depths to replace the single pit depths of a traditional compact disk. Having four independent pit depths can double the storage capacity of a disk. The multi-level pits are read by direct measurement of the phase difference between two laser spots focused onto the disk surface. Extraction of phase information utilizes the equations of phase shifting interferometry with four shifted fringe patterns created simultaneously by a compact optical head. The system speed is therefore limited by the readout electronics instead of by slow mechanical phase shifters. The resulting system can identify four independent levels as well as the direction of transition from one level to another. The system also has low sensitivity to vibrations and to changes in the fringe contrast and beam intensity.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/276545 |
| Date | January 1987 |
| Creators | Buseck, David Allan, 1963- |
| Contributors | Koliopoulos, Chris L. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Thesis-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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