PURPOSE: To enable the recording of a schlieren pattern and absorption distribution, by mounting a knife edge in an UV scanner.

CONSTITUTION: A shielding window 10 is attached to the door 15 of a centrifugal separator, and mirrors 12, 13 and slits 11 are attached to a rotor chamber. The light emitted from a lamp 1 forms a focus to a slit 4 through a mask 2 and a lens 3. The light issued from the slit 4 passes through a concave mirror 5, a diffraction lattice 7, a mirror 8, a shielding window 10, the cell of a rotor 14, the shielding window 10 and a mirror 17 to form a focus on a knife edge 24. The light issued from the knife edge 24 is formed into an image on the slit 19 integrated with a photomultiplier 20. The output of the photomultiplier 20 is recorded as density distribution. The knife edge 24 is allowed to have access in order to obtain a schlieren pattern.