Tracer control circuit

Claim 1

In a system for controlling the relative movement between a tracer probe and a template comprising: a tracer probe that bears upon the template and is deflected substantially normal to the surface of the template at the point of contact, means for producing deflection signals indicative of the deflection of the probe in selected first and second directions, drive means for driving the probe in the first and second directions simultaneously, means for sensing the speed of the probe moving in the said first and second directions and for producing velocity signals, the improvement comprising: an analog computing circuit for computing the vector sum of deflection signals and for computing normalized drive signals being the deflection signals divided by the said vector sum, an analog computing circuit for computing the vector sum of the velocity signals and for computing normalized deflection reference signals being the velocity signals divided by the said vector sum, first summing means adding a scaled normalized drive signal and a scaled normalized deflection reference signal both corresponding to the first direction, second summing means adding the other scaled normalized drive signal and the other scaled normalized deflection reference signal both corresponding to the second direction; means for inverting the sign of the output of the first summing means; third summing means for adding a scaled deflection signal corresponding to the second direction to the inverted output of the first summing means, fourth summing means for adding a scaled deflection signal corresponding to the first direction to the output of the second summing means, means for controlling the drive means for the first direction with the output of the fourth summing means, and means for controlling the drive means for the second direction with the output of the third summing means.