Abstract
We describe an optical edge-detection system that can detect magnetooptical (MO) edges giving the phase shift 0 or π radians to the Kerr component light in the MO data storage. The interference between the diffraction wavefront from the MO edge within a diffraction limited spot and the reference wavefront gives appropriate intensity distribution for the optical edge detection. We calculated the diffraction patterns from the MO edge using the boundary-element method and observed them experimentally using the Twyman-Green interferometer. The two sets of results are in good agreement.