Lens positioning controller for optical playback apparatus
US4418405A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 29, 1981 |
| Grant date | Nov 29, 1983 |
| Priority date | — |
| Expiry date | Jun 29, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0908
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A focus servo system for optical disc record/playback apparatus includes three current drivers for maintaining the distance between an objective lens and an information surface of the disc substantially constant. One driver is a DC to low frequency amplifier which can drive the transducer over its full range to the mechanical stops. The second current driver is a DC to high frequency amplifier whose output at DC is limited to drive the transducer approximately twice the expected disc runout. At higher frequencies, the output is such that the displacement of the transducer does not exceed the displacement corresponding to DC value. In operation, the low frequency driver adjusts the DC operating point of the high frequency driver so that its output averages to approximately zero, thus decreasing the drive requirements of the high frequency driver. The third driver is a DC current source which sets the static operating point of the transducer.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.