Characterization of micro-lenses based on single interferogram analysis using Hilbert transformation

Measurement of the shape, surface quality, and optical performance of micro-lenses, as well as, the uniformity of the parameters across the wafer is an important issue. In this paper we describe a reflection/transmission microscopic interferometer for characterization of micro-lens array. A Hilbert transform (HT) based method is applied to enhance the fringe contrast and to recover the phase from a single fringe pattern with closed fringes. The reflection mode of operation reveals the geometrical properties of the array whereas transmission mode of operation provides information regarding the focal properties of the micro-lenses. Experimental results on a square-packed fused silica micro-lens array are presented.