- Optical chopper
An optical chopper is a mechanical device which periodically interrupts a light beam. Three types are available: variable frequency rotating disc choppers, fixed frequency tuning fork choppers, and optical shutters. A rotating disc chopper was famously used in 1849 by Hippolyte Fizeau in the first non-astronomical measurement of the speed of light.
"The chopper amplifier allows for either a physical quantity to be measured or on the electrical signal from the transducer. In general it is desirable to chop the signal as close to its source as possible because only the noise that arises after chopping is removed by the process. The rotation of the chopper produces a radiant signal that fluctuates periodically between zero and some maximum intensity."
There are also electrical ways of generating pulsed light beams at a variable millisecond intervals. As an electrical alternative to the rotating disc, pulsed light is currently used to grow plants under intermittent artificial light generated using specially designed ballast systems for standard fluorescent light tubes. Because the light beam is interrupted before the light is generated, unlike devices which interrupt the light after it is generated, the electrically pulsed light tubes reduce the energy requirements of pulsed light applications by an amount equal to the percentage of pulsing, so a 50% flickered on-off light stream is made with 50% less energy. “Chopper Light” systems are also suitable for UV applications.
Late 20th century computer mice used two chopper wheels for encoding.
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