Pavia, Juan MataWolf, MartinCharbon, Edoardo2014-04-142014-04-142014-04-14201410.1364/Oe.22.004202https://infoscience.epfl.ch/handle/20.500.14299/102809WOS:000332520000054Single-photon avalanche diode (SPAD) imagers typically have a relatively low fil factor, i.e. a low proportion of the pixel's surface is light sensitive, due to in-pixel circuitry. We present a microlens array fabricated on a 128x128 single-photon avalanche diode (SPAD) imager to enhance its sensitivity. The benefit and limitations of these light concentrators are studied for low light imaging applications. We present a new simulation software that can be used to simulate microlenses' performance under different conditions and a new non-destructive contact-less method to estimate the height of the microlenses. Results of experiments and simulations are in good agreement, indicating that a gain >10 can be achieved for this particular sensor. (C) 2014 Optical Society of Americatext::journal::journal article::research article