Design of spherically corrected, achromatic variable-focus liquid lenses

A design method for correcting chromatic as well as spherical aberrations of variable-focus, multi-chamber liquid lenses is described. By combining suitable optical liquids with appropriate radii of the liquid's interfaces, liquid lenses with superior, diffraction-limited resolution over a wide focal tuning range are possible. For an infinite object distance, the analytic thin-lens approximation of an achromatic positive/negative varifocal liquid lens is derived and the obtained results are compared with ray-traced optimized designs which consider finite thicknesses and rigid cover glasses. As a design example, the optical performance of a 4mm-diameter positive/negative f /3.6 achromatic liquid lens is given in detail.