White-light array generation with a diffractive lenslet array

Abstract

In this paper we present two different optical configurations providing a white-light array generator based on a diffractive lenslet array (DLA). In both cases, starting from a white-light point source we achieve a regularly spaced set of sharp light spots by use of a single DLA and a small number of extra lenses (only one or two). The first optical system permits us to change the separation between the intensity peaks in a tunable way. The second is very compact and consists only of diffractive lens elements. The key question in both set-ups is the use of achromatic Fourier-transform methods. In this way, we achieve, in a first-order approximation, the superposition of the chromatically dispersed arrays of monochromatic focal points produced by the DLA in a single plane and with the same magnification for all the wavelengths of the incident light. The residual chromatic aberrations of both novel array illuminators are low, even when the temporal spectrum of the source spreads over the entire visible spectrum. Some experimental results are also shown.