楔条形阳极光子计数探测器成像性能的检测

Image performance of photon-counting imaging detector with wedge-and-strip anode

基于楔条形位置灵敏阳极的光子计数成像探测器能够记录入射的单光子或带电粒子位置信息,因而能够在极低的照明条件下实现目标的二维成像。本文研制了一套WSA光子计数成像探测器样机,介绍了它的设计结构及工作原理;分析了这类探测器的图像畸变产生的原因,提出了校正图像畸变的方法,并得到了无畸变的图像。以美国空军标准分辨率检测板(USAF1951)为目标进行了分辨率检测,采集的检测图像显示人的裸眼能分辨出检测板的第2组第6单元条纹。最后,为了消除人眼观测的主观性,通过计算探测器对该单元条纹的成像调制度来确保检测结果的准确性。计算结果显示探测器对该单元条纹的水平、垂直方向成像调制度分别为57%和37%。这一结果表明研制的探测器完全能够分辨该单元条纹,对应的分辨率为7.13lp/mm,即探测器空间分辨率达到了0.14mm。

A photon-counting imaging detector with a wedge-and-strip anode （WSA） can record position information on a single photon or incidence particle, so it can acquire the two-dimensional image of an objective under very low lighting conditions. In this paper, a detail description of a detector prototype built by us is firstly given, including its configuration and operating principle, then the imaging distortion of the detector is analyzed, correction methods are proposed and distortion-free images are obtained. Resolution tests are taken using a USAF1951 resolution target placed in front of the detector. The detected image shows that the 6th element in the 2nd group of the USAF1951 target can be differentiated by the naked eye. Finally, in order to remove the subjectivity error produced by human eye observation and to ensure measurement accuracy, the imaging modulation index is computed. The computed results show that, for the 6th element in the 2nd group of the USAF1951, its imaging modulation index can reach 57% and 37% in the vertical and horizontal, respectively. This result indicates that proposed detector prototype can differentiate the strips above absolutely with a 7.13 lp/mm, i.e., the spatial resolution reaches 0.14 mm.