Stereo Time-of-Flight with Constructive Interference

This paper describes a novel method to acquire depth images using a pair of ToF (Time-of-Flight) cameras. As opposed to approaches that filter, calibrate or do 3D reconstructions posterior to the image acquisition, we combine the measurements of the two cameras within a modified acquisition procedure. The new proposed stereo-ToF acquisition is composed of three stages during which we actively modify the infrared lighting of the scene: first, the two cameras emit an infrared signal one after the other (stages 1 and 2), and then, simultaneously (stage 3). Assuming the scene is static during the three stages, we gather the depth measurements obtained with both cameras and define a cost function to optimize the two depth images. A qualitative and quantitative evaluation of the performance of the proposed stereo-ToF acquisition is provided both for simulated and real ToF cameras. In both cases, the stereo-ToF acquisition produces more accurate depth measurements. Moreover, an extension to the multi-view ToF case and a detailed study on the interference specifications of the system are included.