An Overview of 3-D imaging Techniques Shape from Shading Passive Triangulation Confocal Autofocus Defocus Focus Structured Light Triangulation Laser Triangulation Light Volume Holographic Multiwavelength Interferometry 3-D Imaging Speckle Based White Light Time-of-Flight Continuous Wave Impulse Based Pseudonoise/M-Sequence Figure S1. Taxonomic classification of major 3-D imaging modalities. As shown in Figure S1, optical 3-D scene capture can be broadly categorized into the following three approaches: 1) The triangulation [9] method relies on the trigonometric principles. The distance to an unknown point is measured by computing the respective angles to the point from two edges of a triangle. 2) The ToF method, as the name suggests, relies on the time it takes for light to backscatter from an object at an Amplitude (a.u.) 1 2 3 ×104 Amplitude Image (50 MHz) 4 2.2 Depth (M) 2.4 2.6 unknown distance. Since time delays are linearly proportional to the distance, measuring the ToF amounts to measuring the range of the object. 3) Interferometry is similar to ToF with the main distinction that it requires the light waves to be coherent. Each of these approaches can be further classified based on the application as well as the specialized principle linked with the approach. 2.8 Depth Image (50 MHz) 3-D View Figure 1. Three-dimensional images captured via a ToF sensor. We show an amplitude image (or the conventional digital image), a depth image, and 3-D images seen from multiple viewpoints. IEEE SIgnal ProcESSIng MagazInE | September 2016 | 47