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Gesture-Based Interaction with Time-of-Flight Cameras

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CHAPTER 2. TIME-OF-FLIGHT CAMERAS<br />

2.7.6 Multi-Camera Setups<br />

The use <strong>of</strong> TOF cameras operating at the same modulation frequency in a configu-<br />

ration where light from one camera’s illumination unit can reach the sensor <strong>of</strong> the<br />

other camera corrupts the range measurement. This is due to the fact that the sensor<br />

cannot disambiguate between the phase shift induced by its own illumination unit<br />

and that <strong>of</strong> another camera.<br />

A straight forward way <strong>of</strong> circumventing this problem is to run the cameras at<br />

different demodulation frequencies. The demodulation approach to measuring the<br />

phase shift responds only to a very narrow band <strong>of</strong> frequencies near the modulation<br />

frequency; all other frequencies will merely appear as an increase in background il-<br />

lumination (Lange, 2000).<br />

A second solution to using several cameras in the same environment is to mod-<br />

ulate the illumination by a pseudo-noise signal. In case each camera uses a different<br />

code, the sensor will only detect the phase shift corresponding to its own emitted<br />

signal (Heinol, 2001).<br />

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