Signal To Noise Ratio Testing And Noise Characteristic Analyzing Of Third Generation Low-light-level Image Intensifier

The third generation low-light-level (LLL) image intensifier is the core device of the advanced night vision technology. The signal to noise ratio (SNR) is one of important composite indicators of the image intensifier. To solve the problems of SNR measurement technology, pinhole-like low light illuminancy measurement and noise characteristics analysis, this paper has developed a series of researches.Firstly, we studied the principles and methods of image intensifier SNR testing in this article. With the SNR testing national army standards as technical standards, we designed and developed the hardware and software for the SNR correction device of the third generation low-light-level image intensifier, which consisted of the overall structure, light source device, photoelectric detection components, signal processor, data acquisition system, analyzing software module, database storage module, etc. We established the first internal SNR correction device of the third generation low-light-level image intensifier and resolved the problems of value uniformity and accuracy in SNR measurement of internal low-light-level image intensifier.Secondly, we also studied the photon statistical characteristics of pinhole-like low light spot and measurement principle of photon flux. Based on photon counting measurement method, we developed pinhole-like low light luminometer and implemented the direct measurement of illuminancy of the low-light-level image intensifier SNR testing with a0.2mm diameter and a1.08x10-4lx illuminancy for the first time. And we solved the problem that the SNR testing can’t be closed-loop, which is caused by the illuminancy indirect transfer of the SNR testing lamp-house for the LLL image intensifier.Moreover, we presented the concepts and the specific testing methods of the microchannel plate (MCP) output SNR, and did the MCP output SNR testing experiments by using MCP noise characteristic measurement system, which provided the new technical approach for MCP noise characteristic evaluation. We also analyzed the effect to the LLL image intensifier SNR, which is caused by the photocathode, MCP and phosphor screen. Furthermore, we did the verification experiments for the SNR chain of the LLL image intensifier, which provided the theoretical basis and experimental support for further decreasing the noise of the LLL image intensifier.Based on the SNR correction device of LLL image intensifier, we developed the halo effect tester by using the high-resolution CCD, and performed the test analysis on halo effect of the super second and the third generation LLL image intensifiers. Under irradiation with low illuminancy lamp-house, we respectively collected the pinhole image with a certain diameter and the image of the pinhole on the different image intensifier phosphor screen, and analyzed the compositions and impact factors of the halo image of the phosphor screen. And we testify the accuracy of the measurements by comparing with the halo value of the American third generation LLL image intensifier. The study of the halo effect measurement would further motivate the improvement of tube-making process, and provide the new testing methods for the performance evaluation of the LLL image intensifier.