Experimental Study On Laser Ranging With Time-Correlated Single Photon Counting Techniques

Time-correlated single photon counting technology (TCSPC) is an effective means of single-photon signal detection, based on the measurement of the detection times of the individual photons and the reconstruction of the waveform from the individual time measurements. TCSPC is widely used in fields such as biological research, fluorescence lifetime measurements and laser imaging radar. The purpose of this paper is mainly to study the technology of TCSPC. Firstly, the basic principles of the technology and system solutions are introduced. Secondly, the key technologies of TCSPC, the amplifier's performance is researched and analyzed. Finally, the application of TCSPC in laser ranging is studied.In TCSPC, the detector has a great impact on the SNR, which lacks detailed research by domestic researchers. Based on this, the detector is researched and analyzed in the paper. Through the research in dark counts and total counts of PMT that change with the supply voltage, it is found that there is a flat area in the curves. The analysis of SNR shows that the flat area enables SNR to achieve the optimum while the detector works in a stable condition. Then, according to the theory of photomultiplier tube and photon statistical distribution, it is inferred that the photomultiplier output-pulse amplitude has a certain distribution rule, which is proved by experiments, and in addition, the distribution rule of output-signal pulse amplitude is figured out. Further studies show that dark counts mainly concentrate in low amplitude areas and the photon counts reach the peak in high amplitude areas. Thus the paper comes to the conclusions as follow: Optimum operating voltage are selected within the range of flat area of Count-voltage Curve; Optimum discriminate level is selected at the valley point in the distribution curve of total counts pulse amplitude.TCSPC is used in laser ranging in view of its high accuracy and sensitivity of time resolution. At present, the most measurement precision of short-distance laser rangefinder is meter magnitude and detailed research of TCSPC application in laser ranging is seldom found domestically. This paper performs basic research in short distance laser ranging, using the time-digital converter as time-interval measurement unit, and selecting the method of Letters algorithm and median filtering to process data, which helps to greatly reduce the error ratio of measurement results and improve the measurement accuracy. In addition, through analysis of the largest measurement distance by detection efficiency experiment, the relationship between measurement distance and target dimensions is obtained. The experiments of short-distances in 5m and 7m are successful. According to the experimental results and theoretical analysis, the minimum measurement accuracy can reach a centimeter magnitude in a short distance measuring, and pulse energy can serve as the light source for the micro joule of laser. This study lays the foundation for the miniaturization short-distance laser rangefinder.