The variable frequency chopper consists of a chopping vane mounted on a motor with a limited rotation angle. Current in one direction will set the shutter to the open position and in the other direction will set the shutter to the closed position. Alternating the current will cause the blades to open and close the chopper at a frequency range from DC to 30 Hz for the CH-40, DC to 12 Hz for the CH-50, or DC to 50 Hz for the CH-60 and CH-61.
This method of chopping is jitter free. The elimination of a brush type motor and gear heads gives these choppers high reliability and long life.
The CH-40 chopper is used when very low frequencies are desired. It is used for large light beam chopping or for simultaneous chopping of multiple optical beams. Use with a mirror as an optical beam deflector.