APD-based Photon Counting Imaging System Design

Photon counting imaging systems developed from 1960s have extremely high sensitivity. This kind of systems can detect single photons and their spatial location in principle, and therefore can gain photon images of extremely low illumination. As the development of low-level-light image intensifier technique and low-level-light image devices, photon counting imaging technology has made rapid progress and gradually reaches its maturity. Therefore, photon counting imaging technology has been widely used in military, astronomy, physics, chemistry, biology, quantum electronics and so on.The paper, beginning with the principle of photon counting imaging, then studies the development of single photon counting and imaging. According to problems of the currently used single photon detectors, photomultiplier tube (PMT) and charge-coupled device (CCD), we choose Geiger-mode avalanche photodiode (APD) as the core detector. Based on Geiger-mode APD's single-photon detection mechanism, performance parameters, types and characteristics of avalanche suppression circuitry, we structure the photon counting imaging system by single APD detection and two-dimensional scanning.The paper designs a FPGA-based PCB board to control work of each part of photon counting imaging system, meanwhile, to exchange data with the computer. The PCB board is made up of communication module, two-dimensional guide control module, illumination adjustment module, and so on. We use VHDL language to describe planning of FPGA and realize functions of each module. To reach ns class acquisition accuracy, digital double-frequency technique of FPGA's Phase Looked Loop (PLL) was used; and also we design a logic counter to achieve photon counting.To test and calibrate the parameters of APD photon counting imaging system, we carry out a series of experiments. Through the scanning imaging experiments, the photon counting and imaging capability of the whole system is proved. Finally, combining problems found in the experiments, research directions of future work are considered including possible photon counting image technology extensions.