Review of tradeoffs for quenched avalanche photodiode sensors for imaging turbid media

摘要: Abstract We evaluate the efficiency of a new optoelectronic quenched avalanche photodiode sensor (QAPD), with potential enabling high-resolution imaging through turbid media femtosecond-lasers. Our target application is for cancer in human breast. aim to improve contrast ratio unscattered, image bearing photons by reducing or removing large background multiply scattered that result poor spatial resolution. The approach we are taking use temporal discrimination: ultra-short (less than picosecond) laser pulses and time gated detection can select only those which travel almost straight tissue. feasibility resolving 1 mm structure 50 mm tissue sample, using our system, will be discussed—there no results reported date this performance. enhance short resolved single photon counting technique. In technique, earliest arriving transmitted pulse detected QAPD. When combined an efficient electronic quenching circuit, QAPD insensitive later diffuse photons. High accuracy measurement arrival first achieved amplitude conversion electronics resolution 3 ps. This paper contains discussion source, including QAPD, high-speed comparator, critical biasing intensity counter.