Apparatus for recording and reading an optical disk, having reduced offset in its tracking error signal
US4855983A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 3, 1987 |
| Grant date | Aug 8, 1989 |
| Priority date | — |
| Expiry date | Dec 3, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0901
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A push-pull type tracking error signal produced by reflected light from pits on an ID area of an optical disk is averaged and sampled during a period while a light spot is scanned over the ID areas. An averaged value of a signal representative of the reflected light is stored for each sector of the disk, this value being a first sampled tracking error signal. The tracking error signal is also sampled while the light spot is scanned over a vacant zone having no pits in a data area, storing a second sampled tracking error signal. This vacant zone to be sampled is located either before or after a sequence of data bits in each sector. The first sampled tracking error signal is smaller than the second sampled tracking error signal because of the AC component produced by the pits. Thus, when an offset of the tracking exists, though the tracking error signal is kept almost zero by the servo control, the first sampled tracking error signal is not zero. Therefore, differences between the two tracking error signals indicates the amount of the offset. This offset signal may be visually monitored for adjusting the offset of the apparatus, or may be fed back for the tracking servo. The inventio…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.