Laser scanning system employing parabolic light collection surfaces having optical axes disposed off the Bragg angle of the holographic optical elements of the holographic scanning disc thereof
US5984185A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 22, 1997 |
| Grant date | Nov 16, 1999 |
| Priority date | — |
| Expiry date | Apr 22, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K2207/1018
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A holographic laser scanning system for scanning bar code symbols. The system comprises a holographic scanning disc having a plurality of holographic optical elements disposed thereon for scanning the plurality of laser beams directed at the same incident angle. Each holographic optical element as substantially the same Bragg angle. The parabolic light reflective surfaces are disposed beneath the holographic scanning disc. Each parabolic light reflective surface has an optical axis disposed off the Bragg angle of the holographic optical elements, for focusing towards a focal point above the holographic scanning disc, the reflected light rays collected by each holographic optical element. A photodetector is disposed at the focal point of the corresponding parabolic light reflective surface above the holographic scanning disc, and is radially aligned with the optical axis of one parabolic light reflective surface. The light diffraction efficiency of each holographic optical element at the angle of incidence of each laser beam during scanning is substantially greater than the light diffraction efficiency of the focused laser light transmitted from each parabolic light reflective surfa…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.