Abstract

Interest in micro-optical components for applications ranging from telecommunications to life sciences has driven the need for accessible, low-cost fabrication techniques. Many microlens fabrication processes are unsuitable for applications requiring 100% fill factor, apertures 1000μm with high numerical aperture, and scalability to large areas (e.g., tens of centimeters to meters) with millions of lenses. We report on a flexible, low-cost mold fabrication technique that utilizes a combination of milling and microforging. The technique involves first performing a rough cut with a ball-end mill. Final shape and sag height are then achieved by pressing a sphere of equal diameter into the milled divot. Using this process, we have fabricated molds for rectangular arrays of 1–10,000 lenses with apertures of 251600μm, sag heights of 3130μm, interlens spacings of 2502000μm, and fill factors up to 100%. Mold profiles have a roughness and figure error of 68nm and 354nm, respectively, for 100% fill factor, 1000μm aperture lenses. The required forging force was modeled as a modified open-die forging process and experimentally verified to increase nearly linearly with surface area. The optical performance of lens arrays injection molded from microforged molds was characterized by imaging the point spread function and was found to be in the range of theoretical values. The process can be easily adapted to lenticular arrays as well. Limitations include milling machine range and accuracy.

© 2007 Optical Society of America

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