Write laser power setting responsive to a series of written test signals having two frequency components
US5249172A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 19, 1992 |
| Grant date | Sep 28, 1993 |
| Priority date | — |
| Expiry date | Mar 19, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B33/144
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A write laser power setting device for setting a write laser power for writing data on a recording medium, includes first and second oscillators and for producing carrier signals having high frequencies f1 and f2. The carrier signals are added with each other to produce a sum signal which is applied to a laser driver for producing a laser drive signal. The power of the laser drive signal is changed to various levels. Using the laser drive signal, the write/read head writes test signals at preselected areas on the recording medium such that different writing power levels are applied to different preselected areas, respectively. After writing the test signals, the write/read head reads the recorded test signals. From the read signal, an unwanted signal having a frequency f1-f2 is filtered, and the level of the unwanted signal is detected and stored. A minimum level of the stored levels is selected, and a preselected area at which the minimum level reading is obtained is detected. Then, the writing laser power is set at a writing power level corresponding to the level used for writing the test signal in the detected preselected area.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.