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摘要:
针对传统光电探测方法在强光背景下目标探测对比度低的问题,本文提出一种基于激光照明的主动偏振成像方法。首先构建激光入射双向反射分布模型、激光入射偏振双向反射分布模型以及激光照明的目标表面偏振度模型,并分析3种典型目标材料偏振特性与束散角之间的耦合关系。然后在暗室可控条件下开展逆光观测实验,验证目标偏振特性受激光束散角的影响。实验结果表明:强光背景下主动偏振成像目标对比度与传统被动强度成像相比提升了86.11%,不同束散角下不同目标材料的可见光偏振特性间存在差异,金属材质相对于非金属材质的线偏振度提升更高,实验结果与理论分析具有较好的一致性。最后,在室外开展太阳逆光观测实验,验证了研究方法在室外高强光、远距离下依旧具有适用性。本研究为提升强光背景下的目标精准感知能力奠定了理论基础。
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关键词:
- 激光束散角 /
- 强背景光 /
- 可见光偏振特性 /
- 偏振双向反射分布函数 /
- 偏振度
Abstract:In this study, we propose an active polarization imaging method based on laser illumination to tackle the issue of low target detection contrast in strong light backgrounds, which is a challenge in conventional photoelectric detection. Through constructing a laser incident bidirectional reflection distribution model, a laser incident polarization bidirectional reflection distribution model and a target surface polarization model of laser illumination, the coupling relationship between the polarization characteristics of three typical target materials and the divergence angle of a laser beam is analyzed. Backlight observation experiments are conducted in a controlled darkroom to verify the impact of the scattering angle of the laser beam on the polarization characteristics of the target. The experimental results show an 86.11% increase in target contrast for active polarization imaging under strong light background compared to traditional passive intensity imaging. Additionally, the visible polarization characteristics of different target materials vary with different divergence angles, and the line polarization of metallic materials is higher than that of non-metallic materials. The experimental results are in good agreement with the theoretical analysis. The outdoor solar backlight observation experiment verifies the applicability of the research method in high-intensity light and long-distance settings. This study can lay a theoretical foundation for improving accurate target perception under a strong light background.
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图 5 逆光状态下金色聚酰亚胺薄膜、铝板、太阳能电池板(从左到右)非偏与偏振图像对比图。(a)、(b)、(c)非偏图像(d)、(e)、(f)偏振图像
Figure 5. Comparison of unpolarized and polarized images of gold polyimide film, aluminum plate, and solar panel (from left to right) under backlight state. (a), (b) and (c) are unpolarized images and (d), (e) and (f) are polarized images
表 1 定标实验结果
Table 1. Results of calibration experiments
定标参数 参数数值 积分球输出功率/mW 20.920 激光输出功率/W 2.080 偏振片消光比 0.517 黑布吸收率 0.996 表 2 成像、照明系统的主要技术参数
Table 2. Main technical parameters of imaging and lighting systems
系统 指标 参数 可见光偏振相机 响应波段/μm $0.3 \sim 0.7 $ 镜头焦距/mm 15 光圈数 2.8 靶面分辨率 $2\;464 \times 2\;056$ 像元尺寸/μm 3.45 灵敏度/lx 0.01 白光激光器 输出波段/μm $0.3 \sim 0.7$ 电功率/W $\geqslant10$ 束散角/(°) $ 3 \sim 11$ 输出流明值/lm $ \geqslant 230$ 输出光功率/W 2 表 3 强光背景下不同目标的实验结果
Table 3. Experimental results of different targets under strong background light
目标 图像对比度 非偏图像 线偏振度图像 金色聚酰亚胺薄膜 0.36 0.65 铝板 0.45 0.80 太阳能电池板 0.24 0.48 表 5 室外强光背景下不同探测模式的实验结果
Table 5. Experimental results of different detection modes under strong outdoor light background
目标 图像对比度 非偏图像 偏振图像 无人机 0.03 0.24 表 4 成像系统主要技术参数
Table 4. Main technical parameters of imaging system
相机类型 指标 参数 可见光工业相机 响应波段/μm $0.3 \sim 0.7$ 镜头焦距/mm 25 光圈数 16 靶面分辨率 $2\;046 \times 2\;046 $ 像元尺寸/μm 5.5 灵敏度/lx 0.01 低照度相机 响应波段/μm $0.3 \sim 0.7$ 镜头焦距/mm 25 光圈数 16 靶面分辨率 $1\;920 \times 1\;080$ 像元尺寸/μm 12 灵敏度/lx 10−4 -
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