Artificial compound-eye structure has been studied recently due to its great applications of wide field-of-view imaging
and backlight modules. However, fabrication process for microstructures on curvilinear surface has a lot of difficulties
since traditional fabrication techniques are planar. In this paper, a simple and low-cost method to fabricate microlenses
on spherical surface was demonstrated. Microlenses with high fill factor were formed by thermal reflow technique,
followed by multiple replication processes to transfer the microlenses from planar substrate onto spherical surface.
During the process, we made a curved mold with concave microlenses, which allowed this method to be duplicable
easily. Polydimethylsiloxane (PDMS) elastomer was employed as the material of both microlenses and mold due to its
flexibility and transparency for visible light. To prevent microlenses from being damaged during the release procedure,
surface treatment using trichloro(1H,1H,2H,2H-perfluorooctyl)silane was applied before every replication process.
Several PDMS domes covered with hexagonal or square microlenses on the surface were fabricated successfully. The
diameter of each microlens was about 200 μm and the pitch of array was 220 μm. The radius of curvature of the
spherical surface was about 6.1 mm. The uniformity of microlenses was analyzed through the intensity distribution of
focused spots. Imaging performance of microlenses was shown. The curved microlens arrays were combined with image
sensor, and clear images of objects at different distance are shown. The experimental results showed a high potential for
curved microlens arrays being applied to compact mobile camera lens.