Comparison and Evaluation Method and System of Imaging Effect of Field-Low-Light-Level Image Intensifiers
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摘要: 以像增强器为核心成像器件的微光夜视技术一直是国内外重点发展的关键技术，广泛应用于军用夜视领域。直接对比分析不同型号像增强器输出图像特性的评测方法是评价像增强器成像性能最为直观的重要维度，但由于像增强器为直视型成像器件，带来野外实验光路搭建、多路视频同步录制、不同外型尺寸像增强器适配性等多方面的挑战。因此，本文研究了外场微光像增强器成像效果对比评测方法，研制了包含双像增强器成像光路、低照度CMOS成像光路与激光测距机的光轴平行对比评测系统，可实现同时观察和多路像相机的成像数字视频的采集；系统可便捷地适配安装多种不同外型尺寸、不同供电方式的典型像增强器，同时包含激光测距功能，可测量观察目标的距离；在上位机软件中集成多个无参考图像质量评价指标，可通过数字图像处理技术辅助观察者判断不同型号像增强器成像效果的优劣。实际外场测试实验表明测评系统方便可行，能够反映不同成像光路的成像效果，可反馈指导像增强器生产制造工艺的进一步优化，促进微光夜视技术的发展。Abstract: Image intensifiers, which are core imaging devices for low-light-level night-vision techniques, are used worldwide as advanced military night-vision devices. A method of directly comparing and analyzing the final output image characteristics of different image intensifiers is the most intuitive routine for assessing the image quality of image intensifiers. However, because image intensifiers are direct-view imaging devices, they face many challenges, such as field experimental set-up, synchronous image capturing, and adaption of image intensifiers with different types. Therefore, an image quality assessment method and image quality comparison system for image intensifiers were proposed. Dual-channel image intensifiers, a low-light-level CMOS and a laser rangefinder were integrated into the system; the main optical axis of each device was parallel. The images of the image intensifiers and CMOS were synchronously observed and captured. The system is compatible with different types of image intensifiers and power supply modes. The distance between the target and the system was also measured. Moreover, several no-reference image-quality-assessment metrics were integrated into the software to assist the observer in assessing the image quality of different image intensifiers. The actual field test results show that the proposed system is convenient and practical for comparing the quality of different imaging devices, and can facilitate optimization of the manufacture of image intensifiers, thereby promoting the development of low-light-level night-vision technology.
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图 1 像增强器成像效果对比评测系统原理示意
Figure 1. Diagram of proposed image quality comparison system of image intensifiers
图 5 系统集成内部分布图与实物图
Figure 5. System composition and the final integrated image quality comparison system
图 6 上位机软件界面（右下部分为上部分像增强其成像效果的局部放大及统计信息）
Figure 6. Host computer software interface (the bottom right part shows the local enlarged view and local image statistics of the top images)
表 1 像增强器细节区域评价指标
Table 1. Assessment index of detail region of image intensifier
Indices Black rectangular area in Fig. 8 Red rectangular area in Fig. 8 Black rectangular area in Fig. 9 Image intensifier 1 Image intensifier 2 Image intensifier 1 Image intensifier 2 Image intensifier 1 Image intensifier 2 Imin 166.00 85.00 37.00 25.00 113.00 90.00 Imax 255.00 234.00 61.00 46.00 244.00 246.00 Imean 243.05 216.33 47.65 32.98 142.77 129.96 Istd 8.92 24.73 3.22 2.53 21.23 29.20 IBrenner 58359.00 171799.00 19345.00 11105.00 123959.00 213647.00 ITenen 2224.00 8304.00 0.00 0.00 3928.00 7576.00 Ientropy 3.00 3.58 2.50 2.19 4.10 4.36 
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