An optical system for detecting defects on a wafer that includes a device for producing a beam and directing the beam onto the wafer surface, producing an illuminated spot on the wafer’s surface. The system consisting of the fluorophore and the absorber, which is produced in the detection medium, has an altered effective fluorescence excitation range with an altered fluorescence excitation maximum. The support arm may be supported by a base. It discloses a lifting assembly with a lifting plate at the front bottom of the jack for inserting under the bottom corners of the cabinet for lifting.