Optical chopper

New Focus Optical Chopper, Phase-Locked The Model 3501 optical chopper provides rock-solid stability and ?exibility because its chopping frequency is phase-locked to its own internal frequency synthesizer. It comes complete with four wheels, a wheel cover, and a GPIB (IEEE-488) interface. You can chop from 4 Hz to 6.4 kHz, using either the internal frequency synthesizer or an external source as the reference. And you can chop at the fundamental, a harmonic (2 to 15), or even a sub-harmonic (1/2 to 1/15) of the reference. Other choppers don’t give you nearly as much ?exibility for the price.