Method of calculating the image resolution of a near-infrared time-of-flight tissue-imaging system

A new method for calculating the image resolution for a near-infrared time-of-flight tissue-imaging system is presented. The image resolution is calculated from the full width at half-maximum of the photon-path function along the midplane of the medium, integrated over all times of flight, and weighted by the time-resolved detector response. Detailed treatment of the optical gating mechanism shows that for some types of gating mechanism, there exists an optimal gating time beyond which the image resolution is not improved by arbitrarily decreasing the gating time. This theory predicts a limiting image resolution of similar to 20% of the medium thickness, which is consistent with the research of others. (C) 1996 Optical Society of America