Liquid-crystal active lens: application to image resolution enhancement

The Liquid-crystal active lens combines liquid-crystal spatial light modulator(LC-SLM)with an objective lens. The LC-SLM controls the phase in a pupil plane of the lens, and thus modifies arbitrarily, although within a limited dynamic range, the transfer function of the system. We demonstrate that a liquid-crystal active lens can improve the resolution of an imaging system that is not diffraction limited, i.e. if the detector pixel size is larger than the Airy pattern of the optics. This is achieved by micro;scanning the detector plane to p x p sub-pixel positions, combining the resulting sub-images in one larger image, and then deconvolving numerically the latter. Hence the number of pixels in the image is increased by a factor of p x p. This principle is demonstrated experimentally, and the degradation of image quality as a function of the resolution enhancement factor p is discussed. (C) 1999 Elsevier Science B.V. All rights reserved.