Optimally Modulated Illumination for Rapid and Accurate Time Synchronization

This paper presents a rapid and accurate time-synchronization technique using an LED and an off-the-shelf camera. We discuss optimally modulated illumination as a function of camera exposure time through theoretical analysis and derive its mathematical representation. Experiments in real environments with a single LED and 60 fps camera show that the proposed technique can achieve time synchronization within a 17.4 μs error at the 90th percentile using only four frames (a measurement time of 0.067 s). Comparative experiments with computer simulations prove that the proposed technique using optimally modulated illumination to camera exposure time needs less CPU time than that using nonoptimally modulated illumination. The performance of the proposed technique derived from the noise distribution of intensities in captured images agrees closely with the experimental results, enabling time synchronization to be estimated within a confidence interval at a given confidence level. Possible applications to be developed by utilizing features of the proposed technique are described.