Sensitivity information record
US4222071A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 22, 1978 |
| Grant date | Sep 9, 1980 |
| Priority date | — |
| Expiry date | Dec 22, 1998 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/24316
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A flat major surface of a disc-shaped substrate (e.g., glass or plastic) is coated with a light-reflective layer (e.g., aluminum) which is coated with a dielectric material (e.g., silicon dioxide) highly transparent for light of a frequency supplied by a recording laser. The dielectric material is coated with a thin layer of a smooth continuous, low melting point, low thermal diffusion length metal (e.g., tellurium) absorptive for light of the frequencies supplied by the recording laser. The coating parameters are chosen to establish an anti-reflective condition for the coated record blank at the recording light frequency. The light output of the laser, which is intensity modulated in accordance with a signal to be recorded, is focused upon the coated surface of the disc as the disc is rotated. With the peak intensity of the focused light sufficient to at least cause melting of the absorptive layer, an information track is formed as a succession of spaced pits in which, the reflective layer is effectively exposed through the layer of dielectric material. For playback, light of a constant intensity is focused on the information track as the disc is rotated. During playback, the focu…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.