1. Introduction
Since the advent of computer vision, estimating depth from images has always been the object of study for a large part of the research community. Indeed, recovering depth represents the first pivotal step to pave the way to several downstream applications, ranging from augmented reality, robotics, autonomous navigation, and more. Depth can be measured either by means of dedicated, active sensors – LiDARs, ToFs, Radars, etc. – or through standard imaging sensors by developing algorithms / deep neural networks. Although depth sensing technologies grew fast in the last decade and proved a mature reality, some challenges still preclude their unbound deployment.