Laser surface profiler

By accurate measurement of the angle of reflection of a laser beam that is incident upon a reflective surface with a position-sensitive detector, changes in the surface-normal direction (the slope or the derivative of the surface) can be determined directly. An instrument has been built that makes repeated measurements over the surface and uses the collected data to produce a gray-scale image of the slope. The resolution of this system for detecting changes in the surface-normal direction is found to be better than 0.01 degrees . By focusing of the laser beam to achieve a lateral resolution of 5 mum , the resolvable surface-height change owing to a variation in slope is estimated to be <1 nm .