Focus capture for optical disc system including detection of quad sum signal to close focus
US6087644A · kind A · utility
53Cited by
294References
12Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Aug 27, 1997 |
| Grant date | Jul 11, 2000 |
| Priority date | — |
| Expiry date | Aug 27, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02K41/0356
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A system for focus capture wherein a lens is initially retracted to the bottom of its stroke, moved up to the top of its stroke while looking for the maximum Quad Sum signal, then moved back away from the disc while the system looks for the total light coming back from the disc to be above one-half of the peak value it measured, searching for the first zero crossing and, after the Quad Sum is over one-half amplitude, closing focus.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.