IDEA #9CAQYB Passive optical metasurfaces performing analog spatio-temporal differentiation for event-based image processing. 23A0032

Key Words: analog optical computing, metasurface, spatio-temporal differentiation, edge detection, optical image processing, event-based vision. The invention is a planarized, ultrathin and patterned optical device, also called “metasurface”, operating in the near- and mid-infrared range. When excited by an arbitrary spatio-temporal signal, the device can perform analog spatio-temporal differentiation on the input signal. That is, if a travelling optical wave with an amplitude described by a function (where and y are spatial coordinates and is a time coordinate) impinges on the device from one of its two sides, the optical wave transmitted on the other side of the device will have an amplitude proportional to , where m and n are nonzero integers. This functionality can be used, for example, to perform analog mathematical operations on an arbitrary spatio-temporal signal. Moreover, it can be used for event-based image processing without the need for any electronic circuitry (as instead required by existing technologies). In other words, the image is processed only when the image intensity is changing in time. In particular, the output field consists of a spatio-temporal signal whereby the spatial edges of the input signal are enhanced only at the instants of time where the intensity of the input image is changing.