Depth estimation system using diffractive effects of the grooves and signal elements in the grooves
US4180830A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 28, 1977 |
| Grant date | Dec 25, 1979 |
| Priority date | — |
| Expiry date | Jun 28, 1997 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/22
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Apparatus provides an incident light beam which illuminates the surface of a grooveddisc, having signal elements recorded therein in the form of a succession of spaced apart depressions, with a light spot that spans a plurality of convolutions of the groove. The structure of the grooved convolutions serves as a diffraction grating which reflects the incident light beam into a first plurality of substantially coplanar diverging beams of light. The signal elements also serve as a diffraction grating which reflects the incident light beam into a second plurality of diverging beams of light. Photodetectors, respectively positioned to intercept several of the reflected beams provide outputs corresponding to the light power in the respective reflected beams. Circuits are provided for directly deriving from the photodetector outputs respective estimations of both groove and signal element depths in the region illuminated by the light spot.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.