Apparatus and method for transferring two or more wafers whereby the positions of the wafers can be measured

A method and an apparatus for transferring a substantially flat and substantially circular objects, such as wafers, from a pick-up position to a delivery position, the apparatus comprising, a manipulator, at least one source for emitting a source signal, at least one sensor for sensing said source signal and for providing a sensor signal, a computing device arranged for processing at least one sensor signal to obtain data on the position of said object, the manipulator being arranged for simultaneously transferring a first and a second object along a path in a substantially parallel orientation, spaced apart from each other, and substantially co-axially whereby the central axis of each object may be displaced radially, a said source and a said sensor are connected by a virtual line, whereby the virtual line includes an angle with the central axes of the first and second objects.