An electric eye is a photodetector used for detecting obstruction of a light beam. An example is the door safety system used on garage door openers that use a light transmitter and receiver at the bottom of the door to prevent closing if there is any obstruction in the way that breaks the light beam. The device does not provide an image; only presence of light is detectable. Visible light may be used, but infrared radiation conceals the operation of the device and typically is used in modern systems. Originally systems used lamps powered by direct current or the power line alternating current frequency, but modern photodetector systems use an infrared light-emitting diode modulated at a few kilohertz, which allows the detector to reject stray light and improves the range, sensitivity and security of the device.
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Famous quotes containing the words electric and/or eye:
“Wisdom is like electricity. There is no permanently wise man, but men capable of wisdom, who, being put into certain company, or other favorable conditions, become wise for a short time, as glasses rubbed acquire electric power for a while.”
—Ralph Waldo Emerson (1803–1882)
“The stars are scattered all over the sky like shimmering tears, there must be great pain in the eye from which they trickled.”
—Georg Büchner (1813–1837)