Laser measurement of surface peak to valley depths - using defocussed beam with variable angle of incidence suitable for soft metal coatings

摘要

A contactless measurement device is for the peak to ralley depths of surfaces. It eliminates the problem of diamond point penetration into surfaces with soft metal coatings by using an optically defocussed laser beam projected onto the surface with a variable angle of incidence. A peak to valley depth-proportional, electronically-readable image is processed into an electrical signal which is calibrated w.r.t. a normal roughness to give a measurement accuracy better than 0.0001 millimetres. The variation of the angle of the emitted signal to the defocussing axis for constant focus gives a measure of the surface flow direction. The relative angle of incidence may be continuously varied to produce randomly distributed typical images suitable for on-line control of rolling processes.