Dunkelfeldkondensor(producing a hollow cone of light focussed in the plane of the specimen, so that object points appear as bright images on a dark background)
Tiefenschärfe(the range through which the object plane can be shifted along the axis without significantly deteriorating the imagery in a fixed image plane)
Schärfentiefe(the range through which the object plane can be shifted along the axis without significantly deteriorating the imagery in a fixed image plane)