electric eye

Noun

electric eye (plural electric eyes)

1. A sensor which measures the intensity of light, often used to start and stop electrical equipment (motorized doors, etc.).
   • A man and woman sat before an electric eye in a London laboratory tonight and a group of people in a darkened room in this village outside New York watched them turn their heads move from side to side.1928 February 10, “Span Atlantic by Electric Eye”, in Spokesman-Review, Spokane, USA, retrieved 14 Nov 2013, page 1
   • Another frequently cited possibility is a system of electric eyes reading beams of light that are aimed along tracks so that any displacement of the rails would disrupt the beam.1996 November 29, Richard Perez-Pena, “Rail Accident Stirs Debate About Sensors”, in New York Times, retrieved 14 Nov 2013

   Synonyms:

   photocell, photoelectric cell