Apparatus and method for ice detection
US5243185A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 31, 1992 |
| Grant date | Sep 7, 1993 |
| Priority date | — |
| Expiry date | Jul 31, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/0641
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An apparatus and method that accurately and reliably detects ice on a target surface (20). Intrinsic birefringent properties of hexagonal ice crystals are used to detect ice by analyzing elliptically-polarized reflection of linearly-polarized radiation from ice. A linearly-polarized radiation beam (15) is focused on the target surface (20), and returned radiation (25) is filtered (30) as a function of its elliptical polarization. Filtered radiation (35) is directed to a sensor (40) and quantified according to the intensity of radiation received at various points (41.sub.1 -41.sub.n) on the filter (30), and an output signal for each point is produced (45.sub.1 -45.sub.n). The presence or formation of ice is determined by a signal processor (50) that detects the variance among the output signals (45.sub.1 -45.sub.n)--a variance (55) reaching a threshold value being indicative of ice. Filtering unit (30) may be composed of two polarizing filters (31 and 33), rotatable with respect to each other on a common axis and disposed in a parallel plane therewith. A reading is taken from all the output signals (45.sub.1 -45.sub.n), and an output signal variance (55) is calculated. The filters (…
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