Apparatus for positioning flat objects for microscopic examination

Abstract

An apparatus positions a flat, rectangular object, such as a photomask, on a stage below the objective of a microscope in the XY plane with provision for rotation in the XY plane to correct for a theta shift. A pair of rails are mounted parallel on the stage and may be adjustably mounted to hold different sizes of flat objects therebetween. The members for locating the object in an exact X and Y location on the rails and for theta shifting the object are preferably mounted on the respective rails and are movable therewith to accommodate various sizes of objects. An inexpensive theta shift is achieved by inexpensive stops and pivot mounted on one rail and a spring biased plunger and an adjustable member on the other rail. An adjustment member carries an abutment dowel that contacts the flat object along the end surface opposite to the end stop and is displaced in the Y direction relative to the stop so as to act on the flat object in a rotational direction opposite to the direction rotation caused by the plunger. The adjustment means is operable by a single screw mechanism, whereby turning a single knob at the end of a screw corrects for theta shift. The abutment down is slanted over the flat object, thereby preventing upward or Z directional displacement of the flat object.