Positioning an object with respect to a target location

摘要

System and method for positioning an object 48 at a target location, such as for auto-focusing. The system includes a positioning device 34 including a reference object (37, fig3A) having a plurality of first 38 and second 40 optical elements which are optically distinguishable. The positioning device includes a motor 42 configured to move in a reciprocating manner and a sensor capable of distinguishing the first and second optical elements. The motor allowing relative movement of the sensor 46 and reference object (37, fig 3A) and is configured to stop at a target location in two phases of motion. The method of using the device uses a clock cycle which is started when the object reaches the target location, the clock being stopped when a first transition in the reference object past the target location is reached. The motor is reversed at the second transition past the target location and the clock started when the sensor passes the first transition again and the motor stopped after the recorded time.