We propose to represent a time-of-flight (TOF) camera by the map of "internal radial distances" (IRD), associating an intrinsic distance to each pixel, as an alternative for the classic pinhole model. This representation is more general than the perspective model and appears to be a natural concept for 3D reconstruction and other applications of TOF cameras. In this new framework, calibrating a ToF camera comes down to the determination of this IRD map. We show how this can be accomplished by images of flat surfaces, without performing any feature detection. We prove deterministic calibration formulas, using one or more plane images. We also offer a numerical optimization method that in principle needs only one image of a flat surface. This paper has been recommended for acceptance by Peter Sturm. 
Investigating new calibration methods without feature detection for TOF cameras