If the ToF camera had an appendage in front of the camera with a surface that extended into part of the camera's field of view at a precisely known position, could this be used to provide a reference depth for self-calibration of the remaining obscured cameras imaging area? The motivation is to achieve <5 millimeters ranging accuracy over most of the imaging area, regardless of the measured range. (The same concept is used by some ultrasonic range sensors to mitigate the influence of air temperature and other error sources on the measured range.) Does anyone have an idea of the feasibility of this concept using ToF cameras?
Having a target a fixed distance could help for self calibration but will not assure <5mm ranging accuracy for the entire measurement range. The reason for that is the error is always a percentage of the measured distance and increases with distance. The typical measurement error is less than 1%, which translates to 5mm error at 50cm.