Conversion of evanescent waves into propagating waves by vibrating knife edge

Using plane wave spectrum methods, we analyze the propagation and mutual conversion of plane and evanescent waves generated by a one-dimensional object partially obscured by a vibrating knife edge. We show that subwavelength details of the object may be detected in each part of the transmitted plane wave spectrum, upon scanning the knife edge across the object. We discuss the implications for near-field scanning optical microscopy (NSOM) and compare some aspects of conventional NSOM (physical aperture), and vibrating knife edge (electronic aperture) approaches to the sampling of optical fields. © 1996 John Wiley & Sons, Inc.