  For active optical imaging, the use of single-photon detectors can greatly
improve the detection sensitivity of the system. However, the traditional
maximum-likelihood based imaging method needs a long acquisition time to
capture clear three-dimensional (3D) image in low light-level. To tackle this
problem, we present a novel imaging method for depth estimate, which can obtain
the accurate 3D image in a short acquisition time. Our method combines the
photon-count statistics with the temporal correlations of the reflected signal.
According to the characteristics of the target surface, including the surface
reflectivity, our method is capable of adaptively changing the dwell time in
each pixel. The experimental results demonstrate that the proposed method can
fast obtain the accurate depth image despite the existence of strong background
noise.
