Simultaneous encoding of amplitude apodizers and Fresnel lenses in spatial fight modulators

In this paper we show a technique to simultaneously encode a Fresnel lens and an amplitude filter in a single diffractive optical element (DOE) displayed on a spatial light modulator (SLM). In particular we have displayed this new DOE, which we call amplitude apodized Fresnel lens (AAFL), on a twisted nematic liquid-crystal SLM (TN-LCSLM) working in the phase-only regime. The programmability of the AAFL permits to change dynamically its focal length and its action on the point-spread function (PSF) of an optical system. We provide a method to encode the complex amplitude information of the AAFL on a phase-only function. We also demonstrate how to compensate for the inherent equivalent apodizing effect due to the pixelated structure of SLMs. Different types of AAFLs, such as transverse apodizing AAFL and transverse hyperresolving AAFL are implemented. The excellent quantitative agreement between experimental and numerical results shows the feasibility of AAFLs on a phase-only SLM. © 2001 SPIE · 0277-786X/01/$15.00.