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Gesture-Based Interaction with Time-of-Flight Cameras

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3<br />

Introduction<br />

The second part <strong>of</strong> this thesis is devoted to computer vision algorithms designed for<br />

TOF camera data. In this context, we will demonstrate the advantage <strong>of</strong> a combined<br />

image sensor that delivers both range and intensity, i.e. we will explicitly show how<br />

the combination <strong>of</strong> both types <strong>of</strong> data significantly improves the performance <strong>of</strong> al-<br />

gorithms in contrast to using either data alone. The first section <strong>of</strong> this chapter will<br />

focus on the improvement <strong>of</strong> the range measurement by exploiting the intensity im-<br />

age under the well-defined lighting conditions provided by the TOF camera illumi-<br />

nation. Secondly, we will address the topic <strong>of</strong> image segmentation. Here, the goal<br />

is to identify connected image regions that depict an object or a person present in<br />

the scene. These results will then be used in an algorithm for the estimation <strong>of</strong> hu-<br />

man pose that fits a simple model <strong>of</strong> the human body in 3D. Finally, we will turn<br />

to the discussion <strong>of</strong> suitable image features for encoding relevant properties <strong>of</strong> TOF<br />

images. In this context, we will first discuss geometrically motivated features that<br />

are related to the Gaussian curvature. We will then reformulate the computation <strong>of</strong><br />

these features in 3D to achieve scale invariance. A third type <strong>of</strong> features is obtained<br />

using the sparse coding principle. These three types <strong>of</strong> features will be evaluated in<br />

the context <strong>of</strong> detecting facial features, such as the nose. Finally, we will turn to the<br />

computation <strong>of</strong> range flow and will use the resulting 3D motion vectors for the recog-<br />

nition <strong>of</strong> human gestures. In the following, we will give a brief overview <strong>of</strong> the four<br />

topics discussed in the scope <strong>of</strong> Part II <strong>of</strong> thesis <strong>with</strong>in Chapter 4 through Chapter 7.<br />

Shading Constraint Improves TOF Measurements<br />

In Chapter 4, we describe a technique for improving the accuracy <strong>of</strong> range maps mea-<br />

sured by a TOF camera. Our technique is based on the observation that the range<br />

map and intensity image are not independent but are linked by the shading con-<br />

29

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