Far field optical imaging with subwavelength resolution

We describe a far field optical imaging technique for surface topography me asurement with subwavelength lateral resolution. In this system, the surfac e under test is vibrated in a plane parallel to the plane of the surface an d perpendicular to the incident probe beam. The phase of the reflected beam , modulated by surface irregularities, is detected by cutting half of the o verall beam with a knife-edge and by using a lock-in amplifier whereby nois e floor is lowered and transfer function profile is extended to higher spat ial frequencies. We present experimental results showing subwavelength late ral resolution. (C) 2000 Published by Elsevier Science B.V.