Antireflective information record having an optically passive transparent layer
US4195313A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 14, 1978 |
| Grant date | Mar 25, 1980 |
| Priority date | — |
| Expiry date | Dec 14, 1998 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/25715
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A flat major surface of a disc-shaped substrate (e.g., of glass) is coated with a light-reflective layer (e.g., of aluminum) which is coated with a dielectric material (e.g., silicon dioxide) highly transparent for light of a frequency supplied by a recording laser and of a thickness equal to an integer multiple of the half-wavelength of the laser light output in the dielectric material. The dielectric material is coated with a layer of material moderately absorptive for light of the frequency supplied by the recording laser (e.g., an organic dye such as fluorescein). The coating parameters are chosen to establish an anti-reflection 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 cause ablation 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 o…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.