Hybrid Sensing Approach For Coded Modulation Time-of-Flight Cameras

In recent years, application fields such as industrial automation and indoor robot navigation increased the demand on reliable localization systems. Simultaneous mapping and localization systems often depend on depth imaging in order to reconstruct the scene. Time-of-Flight sensors prove to be well suited for these applications, however are impaired by different error sources. The measurement principle is based on measuring the phase and consequently the delay of emitted and reflected light. Specular surfaces can cause pixel saturation, while the periodicity of the measured phase leads to ambiguous distances. In this paper, we aim to solve these problems by proposing a new Time-of-Flight depth sensing approach. By combining the emerging coded modulation method with traditional depth sensing, we are able to unify the advantages of both methods. Images captured with coded modulation show a pixel response only within selected distance limits. In contrast traditional continuous wave Time-of-Flight imaging exhibits a superior signal-to-noise ratio. This method enables to mask erroneous distance measurements, allowing Time-of-Flight sensors to produce more reliable depth measurements and gain traction in the industrial environment. As our evaluation shows, our method is able to remove the influence of specular surfaces, and is capable of masking ambiguous distance measurements. Furthermore, our approach improves the system behavior by enabling more robust exposure time control.