Apparatus and method for monitoring holographic light protection filters
US5602656A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 9, 1994 |
| Grant date | Feb 11, 1997 |
| Priority date | — |
| Expiry date | Dec 9, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03H2250/39
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
Method and apparatus for monitoring wavelength shift in a holographic light protection filter to determine if the hologram has been damaged by moisture. The hologram is provided with first, second and third areas. The first area is an extra moisture protected area covered by a moisture resistant material. The second area is adjacent to the first area and is recorded at a different wavelength than the bulk of the hologram. The third area is the remainder of the hologram. The user compares light reflections at these specific areas of the hologram and observes color variations to determine if the hologram has been damaged by moisture. In another embodiment, scribe lines are drawn in the hologram through the three areas. The user detects moisture damage by observing the apparent displacement of these scribe lines in the three areas when viewed through a diffraction grating.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.