Competitor passage controlling device for determining e.g. finish time of skier, has opaque plate whose hole is arranged against portion of photoreception surface of light sensor to only allow passage of beam reflected by retro-reflector

摘要

The device has a light source (2) to transmit an infrared light beam (Le) toward a retro-reflector. A light sensor (3) e.g. photovoltaic cell, receives the light beam (Lr) reflected by the retro-reflector to convert the reflected beam into an electric signal, which varies during passage of a competitor between the sensor and the retro-reflector. An optical filter in the form of an opaque pierced plate (5) is placed near the source. A hole (6) of the plate is arranged against a portion of a photoreception surface of the sensor to only allow passage of the beam reflected by the retro-reflector. The light source is an LED or a laser diode.