Focus-error detection using prism-enhanced spot size monitoring
US5084783A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 20, 1990 |
| Grant date | Jan 28, 1992 |
| Priority date | — |
| Expiry date | Apr 20, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/1381
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An apparatus and method is described for detecting focus errors in an optical head by positioning a prism in the optical path of a return light beam reflected from an optical recording medium. The prism reduces the beam in one dimension by a factor of M and concurrently increases the divergence/convergence angle associated with a focus-error of the beam by a factor of M in this dimension, thereby desirably enhancing the focus error signal by a factor of M.sup.2. A focus error is detected by a segmented photodetector having inner and outer photosensitive regions. The photodetector generates an electrical signal indicative of the focus error from the difference in light intensities at the inner and outer regions. The photodetector preferably is segmented in such manner as to also provide a track error signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.