Patent ID: 8904560

Claim:
A method of operating a metrology instrument, comprising: generating relative motion between a probe and a sample at a scan frequency using an actuator exhibiting a non-linear response; detecting motion of the actuator using a position sensor, wherein the position sensor exhibits noise in the detected motion; controlling the XY position of the actuator with a control signal, u, using both a feedback loop and a feed forward algorithm, wherein a feedback signal, u fb , associated with the feedback loop is updated during operation of the metrology instrument by combining a signal associated with a predetermined path defined by the feed forward algorithm therewith, wherein the feed forward algorithm substantially continuously updates the control signal so that the XY motion of the actuator substantially follows a reference thereby compensating for the non-linear response; wherein the controlling step includes operating the feedback loop at a bandwidth less than the scan frequency associated with the generating step thereby attenuating noise in the actuator position compared to the noise in the detected motion in the corresponding bandwidth; and wherein the bandwidth of the feedback loop is different than a bandwidth associated with operation of the feedforward algorithm.