Imaging-free object recognition enabled by optical coherence

Visual object recognition is one of the most important perception functions for a wide range of intelligent machines. A conventional recognition process begins with forming a clear optical image of the object, followed by its computer analysis. In contrast, it is possible to carry out recognition without imaging by using coherent illumination and directly analyzing the optical interference pattern of the scattered light as captured by an image sensor. Here we show that such direct visual recognition can overcome traditional limitations of imaging optics to realize excellent recognition without focusing, beyond diffraction limit, or in the absence of direct line-of-sight.