The observation of objects located in inaccessible regions is a recurring challenge in a wide variety of important applications. Recent work has shown that using rare and expensive optical setups, indirect diffuse light reflections can be used to reconstruct objects and two-dimensional (2D) patterns around a corner. Here we show that occluded objects can be tracked in real time using much simpler means, namely a standard 2D camera and a laser pointer. Our method fundamentally differs from previous solutions by approaching the problem in an analysis-by-synthesis sense. By repeatedly simulating light transport through the scene, we determine the set of object parameters that most closely fits the measured intensity distribution. We experimentally demonstrate that this approach is capable of following the translation of unknown objects, and translation and orientation of a known object, in real time.

Small salient-pole alternators are being embedded in power systems in growing numbers and parameter sets which accurately reflect the transient response of such machines are in demand. High levels of local saturation and rapidly changing flux densities result in transient currents that arc far from the pure exponentials of classical theory so that estimation by curve fitting is difficult. A new approach, which encourages designer intervention, is described and this is seen to be reliable and repeatable, with a good quality of fit, even in the sub-transient region.

In correlation-based time-of-flight (C-ToF) imaging systems, light sources with temporally varying intensities illuminate the scene. Due to global illumination, the temporally varying radiance received at the sensor is a combination of light received along multiple paths. Recovering scene properties (e.g., scene depths) from the received radiance requires separating these contributions, which is challenging due to the complexity of global illumination and the additional temporal dimension of the radiance. We propose phasor imaging, a framework for performing fast inverse light transport analysis using C-ToF sensors. Phasor imaging is based on the idea that, by representing light transport quantities as phasors and light transport events as phasor transformations, light transport analysis can be simplified in the temporal frequency domain. We study the effect of temporal illumination frequencies on light transport and show that, for a broad range of scenes, global radiance (inter-reflections and volumetric scattering) vanishes for frequencies higher than a scene-dependent threshold. We use this observation for developing two novel scene recovery techniques. First, we present micro-ToF imaging, a ToF-based shape recovery technique that is robust to errors due to inter-reflections (multipath interference) and volumetric scattering. Second, we present a technique for separating the direct and global components of radiance. Both techniques require capturing as few as 3--4 images and minimal computations. We demonstrate the validity of the presented techniques via simulations and experiments performed with our hardware prototype.

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The use of small alternators, other than for standby purposes, is increasing and this has focused attention on the reliability and utility of the parameters normally quoted for such machines. Test procedures are described and methods used for parameter estimation discussed, with particular emphasis on the difficulties presented by small brushless machines.