Patent ID: 7283201

Claim:
A stage device for holding an object, comprising: a movable object-holder configured to hold the object; at least one actuator situated and configured to move the object-holder; a position-detector situated and configured to determine a position of the object-holder, the position-detector producing a first position signal whenever the object-holder is not holding the object and producing a second position signal whenever the object-holder is holding the object; and a controller connected to the position-detector and to the at least one actuator, the controller being configured to produce a first control signal upon receiving the first position signal and to produce a second control signal upon receiving the second position signal, the first and second control signals causing the at least one actuator to place or hold the object-holder at a pre-determined position whether the object-holder is not holding or is holding the object, the controller being further configured to determine whether the object is not being held or is being held by the object-holder based on whether the controller is receiving the first position signal or the second position signal, respectively.