Guard holograms
US5138470A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 14, 1990 |
| Grant date | Aug 11, 1992 |
| Priority date | — |
| Expiry date | Dec 14, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B2027/012
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A head-up display for a vehicle, including a primary image reflection hologram supported by a transparent substrate located in the vehicle operator's field of view for the ambient scene in front of the vehicle, a light source for providing playback illumination to the primary image hologram, and a guard hologram in front of the primary image hologram for substantially reflecting ambient illumination that otherwise could spuriously turn on the first reflection hologram, the guard hologram having an angular bandwidth and a spectral bandwidth that are greater than the angular bandwidth and the spectral bandwidth of the primary image hologram, and having an optical density of 2.0 or greater. The guard hologram can be parallel fringe reflection hologram or a slant fringe reflection hologram.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.