Holographic display element
US5153751A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Apr 26, 1991 |
| Grant date | Oct 6, 1992 |
| Priority date | — |
| Expiry date | Apr 26, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B2027/012
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
The invention relates to a holographic display element which includes a reflection hologram and is attached to, for example, an automobile windshield so as to project light rays carrying images of display information onto the display element from a luminous source in the car. When external light such as sunlight coming is diffracted by the reflection hologram there is a possibility that visible light ranging from 570 nm (greenish yellow) to 780 nm (red) is diffracted into a certain range of angles in a horizontal plane and makes a strange impression on persons viewing the windshield from the outside. According to the invention another reflection hologram having different diffraction characteristics is superposed on the first hologram on the outer side in order that diffraction of visible light into the aforementioned range of angles may become inconspicuous. In one embodiment the second hologram diffracts light of 570-780 nm at angles outside the aforementioned range of angles thereby to prevent undesirable diffraction by the first hologram. In another embodiment the second hologram diffracts different wavelengths into the range of angles so that additive color mixing with visible …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.