Research On Photon Counting Image Technology Based On APD

When biased above the breakdown voltage, which called Geiger mode, avalanche photodiodes (APDs) and avalanche photodiode arrays (APD arrays) have the ability of single-photon detecting, find applications in many areas like astronomy, biochemistry, waveguide photodetector, telecommunication, particle physics and general instrumentation. With APDs and APD arrays, many geometrical and device parameters can be adjusted to optimize their performance for a particular application. A new low-level-light imaging technology was proposed based on the statistical properties of photons and the photoelectric response of APDs. The topics which we have studied include both fundamental physics and future applications. The main achievements are as follow:In low-level-light imaging system, very low-level-light appears more particle characters than wave characters, going with luminous flux fluctuations randomly, which can't be properly treated with classical image processing theories and techniques. Time domain integration is the common method to reduce the effects of corpuscular property and luminous flux fluctuations. To achieve longer integration time, the detector need some special handling to reduce dark current noise and thermal noise of detector itself, causing response frequency decreased. Photon counting technology is a useful method to solve this difficult problem. In this way, we can get low-level-light image quickly and accurately based on inversion techniques with photon counting result and the known probability distribution of incident light. It is very important to study on the probability distribution of reflect light in photon counting image technology. We derived the model of photon reflecting from rough surface based on semiclassical statistical optics, conducted the thorough research to photon reflection properties of rough surface with a combination of Monte Carlo method and physics experiment. In this work, statistical distributions of low-level-light based on APDs are derived, which will lay a foundation of further application of photon counting image technology.Time and frequency responses of APDs are very important in photon counting system, and there are many models for circuit simulation. But these studies generally based on the carrier rate equations of steady-state condition, disagree with the single-photon-indicate condition. In this work, the absorption region and the multiplication are proposed as many little regions of△χ→Othickness. Based on sub-domain carrier integration equations, a mathematical model describing the time and frequency response of four-layer reach-through APDs was derived, under some reasonable assumptions. The results presented here for the electrons clearly indicate that, under Geiger mode, gain of APDs increased rapidly, which lead to avalanche current duration expanded. The analysis assumes gated-mode and active quenching operation of the APDs and APD arrays can reduce dead time, increase response frequency greatly.As we know, Geiger mode APDs and APD arrays must work under gated-mode because of their quenching time. In this working mode, the continuous incident light signals are divided into discrete time interval. Obviously, the informations of photon counting results were decreased because of gated-mode sampling, recovery and correction must be done to the counting resulting. In this work, a photon counting image model based APD arrays'response characters and Poisson point process of photons was developed. To validate the model, an image correlated by pixels and photons number was used as standard image, which processed by the arithmetic of photon counting image model. And Monte Carlo simulation methods were used to investigate the relationship between the qualities of photon counting image and the inherent disadvantage of APDs such as nonuniformity and dark counting. As a result, illumination limit of APD counting image technology based on existing APDs is given.AS an important work, we developed an experimental platform based on silicon APD single-photon conter, achieved photon counting image through serial scanning mode of single APD. Focusing on models of photon counting image technology, a large amount of experimental were conducted, sameness and diference were compared with the simulation results. This work also studies on the applications of photon counting image technology in low-level-light image enhanced technology through contrast experiment on gray response and vertical fringe resolution between APD photon counting image and EMCCD. In conclusion, all experimental test, simulation comparison and application results indicate that photon counting image technology based on APDs has better sensitivity than traditional photoelectric imaging technology.Finally, research directions of future work are considered including possible photon counting image technology extensions.