Diffractometer for measuring signal depth and width
US4236823A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 28, 1979 |
| Grant date | Dec 2, 1980 |
| Priority date | — |
| Expiry date | Feb 28, 1999 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/22
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An incident light beam illuminates the surface of a disc, having signal elements recorded therein in the form of a succession of spaced apart depressions, with a light spot that spans a plurality of depressions. The structure of the depressions serves as a diffraction grating which reflects the incident light beam into a plurality of substantially coplanar diverging fans of light. Polarizers are interposed between the light beam source and the surface to polarize the light beam in orthogonal directions. Photodetectors, positioned to intercept the reflected fans, provide outputs corresponding to the light power in the reflected fans. The photodetectors provide a first output of the reflected light power of the light beam polarized in a first direction and a second output of the light power of the reflected light beam polarized in a direction orthogonal to the first direction. The ratio of the first output to the second output is indicative of the depression depth.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.