Scattered light smoke detector having a two-color LED, a photosensor, and a wavelength-selective polarizer connected upstream of the photosensor or connected downstream of the two-color LED, and suitable use of such a polarizer
US11506590B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 26, 2019 |
| Grant date | Nov 22, 2022 |
| Priority date | — |
| Expiry date | Sep 26, 2039 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/4792
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Various embodiments include a scattered light smoke detector comprising: a two-color LED for emitting light of a first wavelength and a second wavelength; a photosensor spectrally matched with said two-color LED; and a control unit connected to the two-color LED and to the photosensor. The control unit is configured to control the two-color LED to emit light of the first wavelength or the second wavelength and to detect a photosensor signal of the photosensor. The control unit is further configured to analyze the photosensor signal for a first scattered radiation intensity and a second scattered radiation intensity allocated respectively to the first wavelength and the second wavelength. There is a polarizer optically connected upstream of the photosensor or downstream of the two-color LED. The polarizer polarizes light passing through at different intensities in dependence upon the respective wavelength of said light.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.