Scratches, pits and particles which are smaller or larger than the beam size may be measured and identified by a single and dual multiple beam techniques. In one embodiment, this the invention uses a pair of orthogonally oriented white light beams, one in the radial and one in the circumferential direction. The scattered light from the radial and circumferential beams allows the detection and classification of particles, pits and scratches. In other embodiments, single beam techniques are used to classify radial and circumferential defects.