The robust design for gapless microlens array fabrication using the incomplete developing and thermal reflow process

Abstract

A systematic approach to achieving high quality gapless microlens array fabrication using the incomplete developing and thermal reflow process was developed in this study. The experimental results proved that a hexagonal microlens array with a maximum 100% fill-factor could be successfully produced. The major objective in using this robust design is to reduce the variations in microlens array,focal length, allowing improved focus and enhanced illumination brightness. In this experiment, the Taguchi method was used first to perform an efficient experimental design and analyze the robustness of the microlens array fabrication process. Several parameters affect microlens array uniformity; the hexagonal column diagonal, spin coating revolution speed, exposure time, developing time, and reflow temperature. It is very important to control these parameters to decrease the sensitivity to noise. Therefore an artificial neural network (ANN) was used to minimize the variation and make the microlens array less sensitive to process variation. The L-18 orthogonal array was used as the learning data for the ANN to construct an ANN model that could predict the parameters at nondiscrete levels. The results showed the microlens array quality was significantly improved compared with the original design. (c) 2006 Wiley Periodicals, Inc.