Three-degrees-of-freedom precision stage

Precision positioning and fine motion are needed in many fields, such as micro electromechanical system, ultra-precision machine, optical alignment and integrated circuit manufacture, so it is indispensable to develop precision planar stage. A precision stage driven by one piezoactuator is made to achieve three degrees of freedom motion in plane. To realize precision positioning, movement of the stage should be detected and corresponding control scheme should be designed. A displacement detection system based on image processing is developed to measure three degrees of freedom displacement of the planar stage. The core parts of the system are CCD camera, microscope, image collection and image processing. Large rotation of the planar stage has no influence on displacement detection of the system. The system could obtain high resolution together with relatively large detection range. Performance of the planar stage is tested by the displacement detection system. Interference movements of the stage are less than the main movements. Movements of the planar stage in any direction are obtained by logical open-loop control. Micro motions detected by laser interferometer indicate the stage has very high resolution.