Reflection light barrier using polarised light beam - has polarising beam splitter between single transmission and reception lens and light source and photodetector

摘要

The light barrier has a light source (10) and a photodetector (14) associated with a single lens (12) at one end of a monitored surveillance path, with a retroreflector (13) at its opposite end. The light source (10) and the photodetector (14) are coupled to the lens (12) via a polarising beam splitter (11), the retroreflector (13) providing depolarisation of the reflected light, with the light component perpendicular to the transmitted beam directed onto the photodetector (14). Pref. the retroreflector (13) comprises a triple mirror with unmirrored reflection surfaces. ADVANTAGE - Reduced power loss for extending effective working range.