Apparatus for detecting a polarization altering substance on a surface
US5841538A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 10, 1996 |
| Grant date | Nov 24, 1998 |
| Priority date | — |
| Expiry date | Jul 10, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/8848
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An apparatus for detecting a polarization altering substance, such as ice, on a surface includes a polarizing filter on the surface between the surface and the polarization altering substance. When the polarizing filter includes alternating regions having orthogonal polarizing properties, only one viewing of the surface through a blocking filter is required. When light, either polarized or unpolarized, reflects off the surface, it passes through the polarizing filter and becomes polarized. Reflected light that additionally passes through ice after leaving the polarizer becomes unpolarized. When viewed through a blocking polarizer filter, polarized light passing through ice appears bright due to the unpolarizing effect of ice. On the other hand, polarized light not passing through ice retains its polarization and appears dark when viewed through a blocking filter. Since the polarizing filter is between the surface and the viewer, the surface can be metallic, dielectric, or painted without affecting the results. If the proper blocking orientation for the viewer is not known in advance, the Stokes coefficients can be calculated if views are taken through a series of specified polarizi…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.