Fabrication of microoptical freeform arrays on wafer level for imaging applications

Miniaturized imaging systems combining an ultra-compact form factor in combination with the ability of refocusing and depth imaging have gained much interest in the field of mobile imaging. Therefore, artificial compound eye cameras are an extremely promising approach for the realization of compact monolithic camera modules on wafer level. Up to now, their imaging performance was limited to low resolution in the range of VGA format according to fabrication constrains given by the established microoptical fabrication methods, namely the reflow of photoresist. In order to overcome these classical limitations, the use of refractive freeform arrays (RFFA) instead of conventional microlens arrays is inevitable. To enable high volume and cost efficient mass production of artificial compound eye cameras for mass markets like the consumer electronics industry, their fabrication on wafer level is essential, but has not been published up to now. We present a wafer level based process chain enabling the fabrication of these elements for the first time.