Time-resolved diffusive optical imaging using pseudo-random bit sequences.

We have experimentally implemented a time-resolved diffusive optical tomography system via a novel spread spectrum approach. A low power (~5 mW) laser diode modulated with pseudo-random bit sequences replaces the short pulse laser used in conventional time-resolved optical systems, while the time-resolved transmittance is retrieved by correlating the detected signal with the stimulation sequence. Temporal point spread functions of diffusive light propagating through a turbid medium have been measured with remarkably low noise levels and a temporal resolution of 2.24 nanosecond. We also present results of 2-dimensional scanning imaging experiments as evidences of the great potential of this new imaging technique.