Focusing method and system for focus capture and focus control in optical disc system including detection of Quad Sum signal to close focus
US5828054A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 7, 1995 |
| Grant date | Oct 27, 1998 |
| Priority date | — |
| Expiry date | Jun 7, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02K41/0356
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An improved focusing method including focus capture and focus control in an optical disc system having a lens and a disc. The method includes the steps of impinging light upon a disc to be read; moving the lens to a first position; monitoring a Quad Sum signal; moving the lens away from the first position towards the disc being read while looking for a maximum of the Quad Sum signal; moving the lens away from the disc; monitoring total light received from the disc; determining, during the monitoring of light, when the total light is above one-half a measured peak value; searching for a first zero crossing; determining when the Quad Sum signal exceeds approximately one-half peak amplitude; and closing focus when the Quad sum signal exceeds the one-half peak amplitude. After closing focus, the method further includes the steps of controlling a focus error signal at a first predetermined gain to produce a first level output, the first predetermined gain being maintained while reading information stored on the disc; and controlling the focus error signal at a second predetermined gain to produce a second level output, the second predetermined gain being maintained while writing informa…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.