OPTICAL SMOKE DETECTION BASED ON THE TWO COLOUR PRINCIPLE USING A LIGHT EMITTING DIODE WITH AN LED CHIP FOR LIGHT EMISSION AND WITH A LIGHT CONVERTER FOR CONVERTING A PART OF THE EMITTED LIGHT TO LONGER WAVE LIGHT

摘要

The invention relates to an arrangement (10) for optical smoke detection according to the two-color principle. The arrangement comprises a light-emitting diode (1) and a photosensor (2) for detecting scattered light or transmitted light. The light-emitting diode is designed to emit light in a first wavelength range and in a different second wavelength range. According to the invention, the light-emitting diode has an LED chip (3) for emitting light in the first wavelength range and a light converter (6) for converting a portion of the emitted light into light of the second wavelength range. The second wavelength range has a spectral half-width (BR) of at most 100 nm. In a particular embodiment, the light converter has a phosphorescent phosphor with an optical decay half-life (λF) and / or optical rise half-life (ΔR) in the range of 10 μs to 50 ms. By means of a control unit (9) as part of a smoke detection unit (20) with an arrangement according to the invention, the two-color ratio from the height of an abrupt signal rise or abrupt signal drop (RS) of the detected photosensor signal can be determined immediately after switching on / off the light-emitting diode. The invention also relates to a smoke detector and an optical smoke detection method.