Scanning laser differential-heterodyne interferometer for flying-height measurement

With conventional optical interferometry flying-height testing, a stationar y measurement beam and a two-axis moving stage are used to measure slider-d isk spacing at different points on the slider. Pitch angle or roil angle is calculated an the basis of the measurement results. me report on a scannin g differential-heterodyne interferometer. which measures the continuous fly ing-height variation along the edge of a slider witt; two continuously scan ning laser beams. Pitch angle or roll angle can be obtained directly from t he scanning measurement. The system can also measure points individually to obtain the absolute flying height at different locations on the slider. Ex periments were performed to demonstrate the concept of scanning measurement . The flying-height variation along the slider edge was measured by continu ous scan and by point-to-point moving. The measurement results from continu ous scan coincided with those of conventional methods. (C) 2000 Optical Soc iety of America.