An optical method using a laser and an integrating sphere combination for characterizing the thickness profile of magnetic media

An optical instrument developed for measuring the film thickness of magnetic media is described. The system uses a polarized-laser beam and an integrating sphere to measure the absorption by the magnetic media. The film thickness is calculated from the absorption value in real time by using a personal computer. The corresponding radial and azimuthal positions for the measurement are determined from a computerized R-θ (rotational-translational) stage. The automated instrument, which rapidly maps the film thickness of particulate and thin-film media, has provided the first full-disk image of film thickness variation