Line edge follower

A line edge tracer system for use with an X-Y coordinate drive machine to cause said machine to follow the path described by the line edge comprising;

• a circular photo sensor array capable of scanning a field having a radius determined by an optical system associated with said photosensor array;
• a phase-lock circuit including said photosensor array and a two-phase oscillator circuit for producing sine and cosine wave forms;
• a phase comparator circuit connected to said two-phase oscillator circuit, the output of said phase comparator circuit being connected to a voltage controlled oscillator circuit, the output of said voltage controlled oscillator circuit producing clock pulses to sequentially sample the individual photosensitive elements in said photo sensitive array to produce a video output signal and to cause said photo sensor to emit a sync pulse which is fed back to said phase comparator circuit to synchronize the angular position of said veido pulses with the sine and cosine wave forms produced by said two-phase oscillator circuit;
• video amplifier circuit connected to said photosensor array;
• a pulse conditioning circuit connected to said video amplifier for receiving the video signal and for changing the wave form of said signal;
• a sample and hold circuit connected to the two-phase oscillator circuit for receiving said sine and cosine wave forms therefrom and also connected to the pulse conditioning circuit to receive the changed wave form therefrom and also connected to the pulse conditioning circuit to receive the changed wave form therefrom to sample the sine and cosine wave forms by the changed wave forms;
• and an X and Y axis feed rate control circuit connected to such sample and hold circuits for operating an X servo and a Y servo response to the signal received from such sample and hold circuit whereby the resultant of said X and Y movement being the path described by said line.