Optical switch for detecting e.g. transparent polymer film, has phototransistor that receives light whose intensity falls so that conductivity of phototransistor is reduced, when object is introduced in light beam emitted by light source

摘要

The switch has a phototransistor (Q1) receiving light beam emitted by a light source e.g. light emitting diode (LED1). Output of the phototransistor is connected to a transistor (Q2) that is connected in series with the LED1, in feed line of the LED1. The intensity of light received by the phototransistor falls so that conductivity of the phototransistor is reduced, when an object is introduced in a path of the light beam.