The present invention, in the vacuum coating system as a test glass changer for the optical measurement in the layer properties, the test glass exchanger is at least one movable substrate holder (2 for guiding the substrate to a path at least through one of the stream of coating material ) and, at least it is connected firmly to the rotary spindle (4) to one test glass element and the rotary spindle (4) mounted in the can be rotated relative to the substrate holder (2) to the center (6), at a time one of the a test glass element in the beam path of the optical measurement device and includes a control device for introducing at least one stream of the coating material, the mount (6) is at least one of which is eccentrically offset with respect to the rotary spindle (4) recess 7 a has, mounted 6 of the rotary spindle (4) according to which a rotational movement about this may be caused by the control device, the test glass exchanger, recesses (7) one of Li of test to the test glass elements arranged in the recess characterized in that can be applied to is provided with a centering device 10, the torque and the holding moment is mounted by the centering device (6) to move to the measuring position of the optical measuring device It relates to a glass exchanger.
In addition, prior to the present invention is a method for the exchange of test glass using a test glass exchanger, recesses (7) arranged in the test in one of the recesses of the glass element is moved to the measuring position of the optical measuring device, the method comprising using the control device causing pivotal movement of the mount (6), the angular distance is recessed from the measurement position of a step of moving the test glass element by a rotational movement to the first position, the first position (7 ) and a small, mobile phase than the angular distance between, to a test method for testing a glass replacement glass element by using a centering device (10) characterized in that it comprises the step of moving a measurement position.