Abstract: A method and apparatus for remote and automatic detection of surface flaws in tubes, pipes and other cylindrical or enclosed cavities that have been treated with a photoluminescent medium. The device, or so-called scanning probe, has a nonrotating ultraviolet radiation source, an offset rotary drive means, a passive rotary scanning means that includes a plurality of lenses, reflectors and an optical filter, a non-rotating solid-state photodiode and support electronic circuitry. The ultraviolet illumination source and photodiode are mounted on-axis and do not rotate. A passive optical scanning means is caused to rotate by an offset rotary drive means. Ultraviolet radiation from the illumination source is projected onto the test-part surface and causes dye penetrant that has been previously deposited onto the testpart surface to fluoresce at a different wavelength, thus revealing the presence of surface cracks and flaws.