Phase-sensitive vision technique for high accuracy position measurement ofmoving targets

This paper presents a vision technique for position and displacement measur ement of moving targets. An adapted phase reference pattern is fixed to the object to be controlled and allows the location of the object in the scene observed by a static camera with an accuracy better than 10(-2) pixel. The phase reference pattern is scaled as a function of the desired field of ob servation and position accuracy. Then the system measurement performances c an he chosen from the nanometer to the millimeter ranges (or even larger). Furthermore, the method is self calibrating in length, since the phase refe rence pattern includes its own length reference. Drifts in vision system ma gnification therefore do not affect the measurement accuracy, Applications can be used in different fields, for instance, the position control of mask s and wafers in photolithography processes or the servo-control of micro-ro bots.