Multi-aperture optical head for parallel scanning near field optical microscopy

This paper proposes the spatial sampling of high spatial frequencies images and their conversion into sequences of diffraction limited images. That me thod is based on a hybrid optical head which combines a classical diffracti ve lens and a spatial filter directly placed in the high resolution optical field. That filter is made of a matrix of sub-wavelength apertures etched in a thin opaque screen. The distance L between apertures is large enough t o be resolved by the diffractive lens. The elementary aperture size d deter mines the exact size of object points. If the aperture size d is much small er than the wavelength used, near field resolutions can be expected. Each i mage obtained with that optical head is a sub-image (or sample matrix) of t he whole high resolution image with a sampling ratio of (d/L)(2). The recon struction of the entire high resolution image is based on a sequence of (L/ d)(2) diffraction limited sub-images which are recorded during a lateral sc anning of the optical head. (C) 1999 Elsevier Science B.V. All rights reser ved.