Single-Photon Avalanche Diode Imagers Applied to Near-Infrared Imaging

Single-photon avalanche diodes (SPADs) can be integrated into large pixel arrays. The aim of this paper is to present a view on how these imagers change the paradigm of wide-field near-infrared imaging (NIRI). Thanks to the large number of pixels that they offer and to their advanced time-resolved measurement capabilities, new approaches in the image reconstruction can be applied. A SPAD imager was integrated in a NIRI setup to demonstrate how it can improve spatial resolution in reconstructed images. The SPAD imager has a time resolution of 97 ps and a picosecond laser source with an average output power of 3 mW was employed. The large amount of data produced by this new setup could not directly be analyzed with state-of-the art image reconstruction algorithms. Therefore a new theoretical framework was developed. Simulations show that millimetric resolution is achievable with this setup. Experimental results have demonstrated that a resolution of at least 5 mm is possible with the current setup. A discussion about how different characteristics of the SPAD imagers affect the NIRI measurements is presented and possible future improvements are introduced.