Improved superresolution with dynamic complex filters

摘要

A complex pupil filter using electrically address twisted nematic LCD spatial light modulators (SLMs) to obtain superresolution along the radial (transverse) direction is presented. The fact that the commercial LCDs can be modeled to obtain amplitude and phase-only SLMs has increased the scope of improving superresolving power dynamically by a suitable combination of both types in an optical system. In general, amplitude-only or phase-only filters result in unwanted increase of side lobe intensity which is disadvantageous for many applications such as microscopy and data storage. The main objective of the complex filter design is to increase the central to side lobe intensity ratio without affecting the size of the central spot. The complex filter performance is optimized for this purpose. The comparison of this filter with that of the conventional pupil filters of both types is shown by simulations. The complex filter is obtained by concatenating amplitude-only and phase-only SLMs in a 4F processor. The SLMs are addressed at video frame rate by a graphic card from the computer. The optimization procedure along with the experimental procedure are described and the results are discussed in this paper.