Discussions on the development of advanced night vision imaging technology
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摘要: 夜视成像技术是在低照度条件下,将不可见辐射加以转换或将微弱的夜天光进行增强,以实现人眼夜间隐蔽观察的一种成像技术,在夜间侦查瞄准、辅助驾驶、导航制导等现代军事应用中发挥着重要作用。为了确保“单向透明”,充分发挥“拥有黑夜”的技术优势,世界军事强国都投入大量人力、物力开展先进夜视成像技术研究,使夜视装备性能得以迅速发展。 本文作为本期《红外与激光工程》——“南京理工大学”专刊的引子,概要地介绍了夜视成像技术当前的进展与所面临的挑战,并对未来先进夜视成像技术的发展趋势——基于光电转换的光强直接成像与基于计算成像的信号反演成像分别进行了探讨与展望。Abstract: Night vision imaging technology converts invisible radiation or enhances faint light at night under low illumination conditions to enable human eyes to see covertly at night. It plays an important role in modern military applications such as night detection and targeting, assisited driving, navigation and guidance. In order to ensure "one-way transparency" and give full play to the technical advantages of "dominating the night", the world's military powers have invested a lot of human and material resources to carry out research on advanced night vision imaging technology, so that the performance of night vision equipment can be rapidly developed. As the first article of this special issue of "Nanjing University of Science and Technology" for the Journal of Infrared and Laser Engineering, this paper outlines the current progress and challenges of night vision imaging technology, and provides a discussion and outlook of the future development trend of advanced night vision imaging technology——direct imaging based on photoelectric conversion and constructive imaging based on computational imaging, respectively.
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图 4 负dB信号反演成像技术实验结果。(a) 信噪比为−10.03 dB暗室棋盘格原始图像;(b) 信噪比为0.492 dB暗室棋盘格反演图像;(c) 信噪比为−5.3 dB山林原始图像;(d) 信噪比为6.99 dB山林反演图像
Figure 4. Experimental results of negative dB signal reconstructive technique. (a) The original image of the checkerboard in the darkroom with an SNR of −10.03 dB; (b) The reconstructive image of the checkerboard in the darkroom with an SNR of 0.492 dB; (c) The original image of the mountain forest with an SNR of −5.3 dB; (d) The reconstructive image of the mountain forest with an SNR of 6.99 dB
图 7 光学系统口径所限制的衍射分辨极限(艾里斑)。(a) 成像系统的最小可分辨距离(光学角分辨率)与成像系统的孔径成反比;(b)~(d) 两个非相干的点目标在不同间距下所能拍摄到的艾里斑图像
Figure 7. Diffraction resolution limit limited by the aperture of optical system (Airy spot). (a) The minimum resolvable distance (optical angular resolution) of the imaging system is inversely proportional to the aperture of the imaging system; (b)-(d) Airy spot images of two incoherent point targets at different distances
图 8 基于孔径编码像素超分辨成像原理。(a) 成像系统光路结构示意图;(b) 经过孔径编码调制后的点扩散函数与传统固定孔径成像对比;(c) 不同编码下光学传递函数与点扩散函数分布;(d) 由探测器空间采样不足所导致的频域混叠现象与孔径编码反演成像后的解调图像
Figure 8. Principle of coded aperture pixel super-resolution imaging. (a) Schematic diagram of optical path structure of imaging system; (b) The point spread function modulated by coded aperture is compared with the traditional fixed aperture imaging; (c) Distribution of optical transfer function and point spread function under different patterns; (d) Frequency domain aliasing caused by the insufficient spatial sampling of the detector and demodulated image after coded aperture constructive imaging
图 9 基于孔径编码的像素超分辨成像技术的典型实验结果。(a) 长波红外成像系统对标准分辨率靶标成像测试;(b)~(d) 采用像素超分辨算法对USAF靶标及远距离车辆前后成像效果对比
Figure 9. Typical experimental results of coded aperture-based pixel super-resolution imaging technique. (a) Long-wave infrared imaging system for standard resolution target imaging test; (b)-(d) Comparison of imaging resolution before and after applying pixel super-resolution algorithm on USAF target and vehicle results
图 10 非相干合成孔径技术原理。(a) 实现点扩散函数优化的分时分孔径相位反演合成重建示意图;(b) 基于分时分孔径相位反演合成孔径实现点扩散函数优化;(c) 超分辨前后成像对比
Figure 10. Principle of incoherent synthetic aperture technology. (a) Process for synthetic aperture super-resolution imaging; (b) Point spread function optimization based on time and aperture division synthetic aperture of phase reconstructive; (c) Image comparison before and after super resolution
图 11 非相干合成孔径超分辨成像技术实验装置与成像结果。(a) 非相干合成孔径实验系统;(b)傅里叶叠层扫描频谱拓展;(c) 基于PZT相移的单孔径自相关波前复原;(d) 单孔径自相关成像以及细节效果;(e) 非相干合成孔径超分辨成像以及细节效果,实现了光学成像系统衍射极限4倍的超分辨成像
Figure 11. Experimental equipment and imaging results of incoherent super-resolution imaging technology. (a) Experiment setup of the incoherent synthetic aperture; (b) Spectrum scanning expansion based on Fourier ptychography; (c) Single-aperture self-correlation wavefront restoration based on PZT phase-shifting; (d) Single-aperture self-correlation imaging and details; (e) Incoherent synthetic aperture super-resolution imaging and details, achieving super-resolution imaging corresponding to 4 times diffraction limit of the optical system