Line edge follower

Abstract

A system incorporating a photosensitive device and associated circuitry for scanning a line to be traced.

What is claimed is: 
     
       1. 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 photosensor 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 .Iadd.represented by a train of video pulses .Iaddend.and to cause said photosensor to emit a sync pulse which is fed back to said phase comparator circuit to synchronize the angular position of said video 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;.]..Iadd.means responsive to said video output signal for generating a predetermined video pulse for sampling the sine and cosine wave forms; .Iaddend.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. 
     
     
       2. A system according to claim 1 for coordinate drive cutting machine wherein a phase shifter is included in said phase lock circuit between said two phase oscillator circuit and said phase comparator circuit whereby a change in the phase relationship between the sine and cosine wave forms produced by the two phase oscillator circuit and the syncronizing clock pulses results in an offset between the path the machine would have followed and the actual path the machine is following, thereby producing kerf compensation. 
     
     
       3. A system according to claim 1 including an off trace circuit which monitors the signal produced by the pulse conditioning circuit so that travel of the machine is stopped when no signal is emitted by such pulse conditioning circuit.