Refraction contrast imaging with a scanning microlens

We demonstrate subwavelength spatial resolution with a scanning microlens o perating in collection mode with a large-area detector. Optical contrast is created by refraction of off-axis light rays at angles larger than the max imum collection angle. With a microfabricated silicon microlens 10 mum in d iameter, we measure spatial resolution due to refraction contrast of lambda /4.3 at a wavelength of lambda =10.7 mum. A model based on ray tracing is developed to explain our result, and we show that lens diameter and index o f refraction limit resolution for large emission and collection angles. (C) 2001 American Institute of Physics.