Glass Reflowed Microlens Array and its Optical Characteristics

We have demonstrated glass microlens array fabricated by thermal reflow process to take advantage of durable lens material and simple process. The microlens was designed using ray tracing, and was realized by controlling the diameter and height of cylindrical glass pattern. The glass pattern (Diameter x Height = 250 x 28 um) was formed by etching a glass plate with HF solution for 4 min (E/R: ~7 um). Then the glass pattern was reflowed at 850degC that is above the glass transition temperature (Tg = 820degC), in the furnace to form a spherical shape. The profile of microlens was measured using a confocal microscopy and the diameter of the spherical shape is larger than 80 percent of the mask pattern size. The fabricated microlens was evaluated in terms of focal length (~600 um) and beam waist (~12 um) using an IR source (lambda=1550 nm).