An optical chopper is an electromechanical instrument that periodically interrupts a beam of light. The MC2000 Optical Chopper, utilizing advanced features to meet the most demanding applications, is a rotary type that is composed of a control console, motor head assembly and slotted chopper wheel. The MC2000 uses a phased-locked loop (PLL) motor speed control design to precisely maintain the chopping speed and phase to a reference signal. An internal, crystal-stabilized, frequency synthesizer provides an accurate and stable reference frequency for long-term stable performance.