Surface curvature measurement of microlenses using a white-light interference microscope and fast geometric fit algorithm

We present a technique for measuring the microlens radius of curvature (ROC). The technique is based on the principle of three-dimensional (3-D) surface topography using a white light interference microscope. By measuring 3-D point clouds of the surface combined with fitting the measured data to an ideal sphere, the radius of the surface is determined. We take advantage of the fast speed of the maximum intensity method and the anti-interference capability of the fitting method of fringe analysis techniques in white-light interferometry to measure the 3-D topography of the microlens array surface. To measure each microlens’s ROC, we use the fast geometric fit algorithm for sphere where the input data are the spherical surface point cloud. We have built a white light interference microscope and experimentally measured the geometric parameter and the surface curvature of some microlens of a commercial microlens array. Our measurement results of the ROC, the surface height, and the diameter of microlens showed a good agreement with the results obtained using the Alpha-Step D-500 stylus profiler and the values reported by the manufacturer, indicating the applicability of this technique.