Light chopper controlled by phase locked stepping motor

摘要

A phase locked loop stepper motor controlled light chopper is disclosed for providing a specific pattern reversal rate. The stepper motor controlled light chopper includes a phase comparator for comparing the phase of a reference signal with the phase of a comparison signal; a RC low pass filter for filtering the output of the phase comparator; a voltage controlled oscillator having a frequency varying in response to the output of the RC filter. The chopper also includes a binary counter for generating count signals responsive to the frequency of the voltage controlled oscillator; a divide by 10 circuit counting one of the outputs of the binary counter and providing the comparison signal. The light chopper also includes a memory circuit for storing an eight state four bit Gray code for driving a four phase stepper motor as a chopper wheel in a specified pattern mounted on a drive shaft.