Diffractive and refractive microlens integration with single photon detector smart pixels

We have performed the design and fabrication of microlens arrays (both diffractive and refractive) and in this paper we will present verification of the optical properties of the microlens arrays as well as a full tolerance analysis of the integration process. The tolerance of the microlenses to light arriving at non-normal incidence is of critical importance due to relatively small active area of the single photon avalanche diodes (SPAD) smart pixels and a detailed consideration of this factor will be given and the modifications to the lens designs needed to permit the use of this system in a large field-of-view mode will be discussed.