In structured light imaging a predefined light pattern is projected onto an object and simultaneously observed by a camera. The appearance of the light pattern in a certain region of the camera image varies with the camera-object distance. This effect is utilized to generate a distance image of the acquired scene. The predefined light patterns can be e.g. gray codes, sine waves , or speckle patterns. Speckle patterns are used in popular structured light (infrared) cameras like the Microsoft Kinect or the Asus XtionPro sensor (see patent ).
Kinect and XtionPro cameras both compute their distance maps by correlating local patches of the IR image with reference images of the speckle pattern projected onto a reference surface at known distances.
Multiple Kinects, Multiple Xtions
With our calibration software we can calibrate multiple Kinect / Xtion systems to each other. The following images show some calibration examples. Three Asus Xtion cameras were calibrated to each other and used to fuse a complete dataset.
 D. Scharstein and R. Szeliski. “High-Accuracy Stereo Depth Maps Using Structured Light”. In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition, pp. 195-202, 2003.
 A. Shpunt and Z. Zalevsky, “Three dimensional sensing using speckle patterns”, United States Patent Application 20090096783