Interference

Interference due to multiple Kinects is caused by the mixing of two IR illumination patterns. See Figure 10-2 for a regular IR pattern and Figure 10-3 for an image of mixed illumination patterns. Do you see how the regularity in the mixed figure is disrupted? This is called noise. Interestingly, in both Kinects, the noise is the other Kinect's pattern. This noise confuses the depth differencing algorithm in the Kinect. Instead of detecting just the disruption in its own field, the Kinect now has a set of points that should not exist where they exist. This causes all sorts of effects, but the two primary effects are shown in Figure 10-4 and Figure 10-5. Figure 10-4 shows “holes” in the detected depth field and Figure 10-5 shows “splotches” generated in areas of no depth detection. The holes can be smoothed over with a variety of methods, but the splotches are far more concerning. They rapidly create a blizzard of false positives that can overwhelm your system. A size filter may help, eliminating any set of voxels or points that don't have a connected size greater than X, but this adds to your computation time.