Method and apparatus for calibrating an optical disk system
US4907212A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 9, 1988 |
| Grant date | Mar 6, 1990 |
| Priority date | — |
| Expiry date | Jun 9, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0037
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Calibration of read timing, write timing and focus is accomplished automatically by comparing reflectance signals. The timing or focus settings are preferably modified, and signals are again compared under the modified adjustment settings. The read timing adjustment includes comparing signals from mark positions immediately preceding and immediately following an isolated mark and adjusting read delay to achieve small or minimum differences between the signals at the mark positions immediately preceding and immediately following the isolated mark bit position. Focus calibration is accomplished by comparing the value of the signal from a mark with the value from a mark position immediately adjacent the mark and adjusting the focus offset until a larger maximum difference between the two signals is achieved. The write timing calibration is preferably achieved by causing the write circuitry to emit a low-power light beam in the vicinity of an unwritten mark position and adjusting the write timing delay circuitry until a low or minimum signal, i.e. high reflectance, is achieved at a desired mark position.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.