  Over the past ten years we have seen a democratization of range sensing
technology. While previously range sensors have been highly expensive and only
accessible to a few domain experts, such sensors are nowadays ubiquitous and
can even be found in the latest generation of mobile devices, e.g., current
smartphones. This democratization of range sensing technology was started with
the release of the Microsoft Kinect, and since then many different commodity
range sensors followed its lead, such as the Primesense Carmine, Asus Xtion
Pro, and the Structure Sensor from Occipital. The availability of cheap range
sensing technology led to a big leap in research, especially in the context of
more powerful static and dynamic reconstruction techniques, starting from 3D
scanning applications, such as KinectFusion, to highly accurate face and body
tracking approaches. In this chapter, we have a detailed look into the
different types of existing range sensors. We discuss the two fundamental types
of commodity range sensing techniques in detail, namely passive and active
sensing, and we explore the principles these technologies are based on. Our
focus is on modern active commodity range sensors based on time-of-flight and
structured light. We conclude by discussing the noise characteristics, working
ranges, and types of errors made by the different sensing modalities.
