Method for detecting an obstruction in a scatter volume of an optical fire alarm and optical fire alarm

摘要

The method involves providing an emitter that emits light (5) of specific wavelength which is passed along beam axis (6) in the inner space (7) of optical fire alarm (1). The light is converted into scattering signals. The scattering signals are then analyzed to detect interference objects (12) by comparing them with each other. An independent claim is included for optical fire alarm.