基于盖格-雪崩光电二极管的光子计数成像

考虑用传统的成像技术检测光生电荷信号时易受模数转换噪声干扰,本文提出了一种基于单光子灵敏雪崩光电二极管(GM-APD)的光子计数成像方法。该方法以单光子灵敏GM-APD作为探测单元,以全数字化方式实现微弱光学信号的有效检测。建立了GM-APD光子流响应模型,利用马尔科夫更新过程分析了光子探测盲区对GM-APD瞬态响应的影响,得到了GM-APD输出的数字脉冲频率与光子流密度之间的关联表达式。搭建了二维扫描成像实验验证装置,通过实验得到了不同密度光子流条件下的光子计数图像。采用标准化互信息量分析得到,在光子流密度为3.0×104count/s的条件下,该实验装置仍然可以实现可视成像;当光子流密度达到2.7×105 count/s时,标准化互信息量大于0.5;实现了在低光子流密度时采用光子计数方式对目标物体的有效成像。

Photon counting imaging based on GM-APD

As conventional imaging systems suffer from the excessive noise from Analog-digital Converters(ADCs) at low signal levels,this paper proposed an imaging method based on Geiger-mode single photon counting Avalanchen photodiode(GM-APDs) to realize all-digital detection of weak optical signals. The photon response model for the GM-APDs was established,and the performance of GM-APDs with dead-time effects was analyzed by using Markov renewal process. Then,the relationship between the digitlal pulse frequency measured by GM-APD and the input photon rate was deduced.Furthermore, a 2D scan imaging system was also built to verify this method. In the experiment, the photon counting images with different input photon rates were obtained. By using standard mutual information to assess image quality, it is demonstrated that the experimental system can achieve visual imaging with an input photon rate of 3.0×104 count/s, and the value of standard mutual information is over 0.5 with 2.7×105 count/s. It concludes that this system can realize photon counting imaging at low signal levels efficiently.