1) Detector 2) Electric eye 3) Magic eye 4) Photoconductive cell 5) Photodiode 6) Photoelectric cell 7) Sensing element 8) Sensor 9) Transducer 1) Electric eye 
An apparatus for converting changes in incident light into electrical impulses.
(Digital cameras and photo printers) Photodiode.
photocell A device that generates electrical energy from light energy, usually as a voltage or current.
Device for measuring or detecting light or other electromagnetic radiation, since its electrical state is altered by the effect of light. In a photoemissive cell, the radiation causes electrons to be emitted and a current to flow (photoelectric effect); a photovoltaic cell causes an electromotive force to be generated in the presence of light a...