Snapshot super-resolution indirect time-of-flight camera using a grating-based subpixel encoder and depth-regularizing compressive reconstruction

An indirect time-of-flight (iToF) camera is an inexpensive depth-map measurement device with a large pixel count; however, spatial resolution is generally lower than that of ordinary image sensors due to the more complicated sensor design for time-resolved measurement. To solve this problem, we apply the snapshot digital super-resolution method to an iToF camera employing compressive sensing and point-spread-function (PSF) engineering. For PSF engineering, we also propose the attachment of a diffraction grating onto a lens as an optical subpixel encoder. Furthermore, exploiting this iToF camera scheme, we also propose compressive reconstruction processing that regularizes a depth map directly. We quantitatively investigated the effectiveness of our method through simulations and verified it by optical experiments with a prototype.