Positioning device

A positioning device comprising a first upper and a second lower support, which are coupled to each other by means of at least two elastic rods acting together as a parallelogram mechanism, at least one support being displaceable parallel to itself with respect to the other support in a direction-parallel to one (Y) of two coordinate directions (X,Y) of an orthogonal coordinate system (X,Y,Z) with a simultaneous elastic deformation of the rods acting as a parallelogram mechanism, which rods have a comparatively high resistance to displacement of one of the supports with respect to the other support parallel to the X-direction, characterized in that the second lower support is supported by means of a static bearing prestressed parallel to the Z-direction and comprising a viscous carrier medium and is guided with respect to a base and is provided with a Z-actuator which cooperates with the first upper support, the upper support being displaceable in a first mode of operation of the Z-actuator by means of a first and a second drive, which is independent from the first drive, respectively, parallel to the X-direction and the Y-direction to an X-Y target position with a Z-position an activated Z-actuator, while the upper support in a second mode of operation of the Z-actuator is displaceable parallel to the Z-direction and is maintained in the said X-Y target position by the first and second drives during a displacement parallel to the Y-direction of the lower support with respect to the upper support.