Synchronization of time-of-flight 3D sensors for optical communication

Time-of-Flight 3D imaging systems are promising transceivers for image sensor based optical communication. 3D sensing based on Time-of-Flight is the most miniaturized depth imaging technology available and is currently being integrated into consumer electronics such as smart phones. Optical line-of-sight communication with a depth imaging system offers complete location-awareness of the communication partner. This enables new opportunities in fields like secure authentication, augmented reality or vehicle to vehicle communication. We show how Time-of-Flight systems are capable of using phase shift keying of pulsed light (PLPSK) to transmit data over a line-of-sight connection. PLPSK is still unexplored in the domain of image sensors and enables Time-of-Flight sensors to transmit multiple bits per frame at rates of over 7 kHz. A serious problem however are asynchronous modulation signals, causing frequent transmission errors and impairing proper communication. In this work, we formulate and discuss the severity of the problem and propose a synchronization procedure. We evaluate our solution with a prototype system, and show that it is possible to reach a synchronization success rate of nearly 100% over a distance of 9 meter.