Natural color low-level-light EBAPS imaging system based on three-color LCTF
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摘要: 高灵敏度电子轰击有源像素传感器(electron bombarded active pixel sensor, EBAPS)既有真空成像器件的高增益、高灵敏度特性,又有固体成像器件的数字化特征,极大地提升了夜视成像水平。该文基于三色液晶可调制滤光片(liquid crystal tunable filter, LCTF)搭建了自然感彩色微光EBAPS成像系统,并根据微光图像特性,对系统获得的彩色图像进行了灰度拉伸、白平衡、色彩校正等色彩增强处理。实验结果表明:该系统可实现反映景物本身颜色特点且具有自然感的低照度彩色成像,有效提升夜间对目标景物特点的观察效果,可以在5×10−4 lx照度下实现彩色成像。
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关键词:
- 电子轰击有源像素传感器 /
- 液晶可调制滤光片 /
- 彩色微光成像 /
- 白平衡 /
- 色彩校正
Abstract: The high-sensitivity electron bombarded active pixel sensor (EBAPS) not only has the characteristics of high gain and high sensitivity of vacuum imaging devices, but also has the digital characteristics of solid-state imaging devices, which greatly improves the level of night vision imaging. A natural color low-level-light EBAPS imaging system was built based on three-color liquid crystal tunable filter (LCTF). According to the characteristics of low-level-light images, the color enhancement processing such as grayscale stretching, white balance, and color correction was performed on the color images obtained by the system. The experimental results show that the system can realize the natural low-illumination color imaging that reflects the color characteristics of the scene itself, which can effectively improve the observation effect of the characteristics of the target scene at night, and can realize the color imaging under 5×10−4 lx illumination. -
表 1 回归方法及其计算形式
Table 1 Regression method and its calculation form
回归方法 色彩校正矩阵TCCM计算形式 QLSR ${{{\boldsymbol{T}}}_{{\text{CCM}}}}{ = }{{\boldsymbol{Q}}}{{{\boldsymbol{P}}}^{\rm{T}}}{({{\boldsymbol{P}}}{{{\boldsymbol{P}}}^{\rm{T}}})^{ - 1}}$ PLSR ${{{\boldsymbol{T}}}_{{\text{CCM}}}}{ = }{{\boldsymbol{Q}}}{{{\boldsymbol{P}}}^{\rm{T}}}{({{\boldsymbol{P}}}{{{\boldsymbol{P}}}^{\rm{T}}} + \lambda {{\boldsymbol{I}}})^{ - 1}}$ 表 2 颜色空间模型
Table 2 Color space model
颜色空间模型 标准矩阵Q 测量矩阵P 变换形式 线性模型 ${{\boldsymbol{Q}}} = \left[ {\begin{array}{*{20}{c}} {{R_{\text{S}}}}&{{G_{\text{S}}}}&{{B_{\text{S}}}} \end{array}} \right]$ ${{\boldsymbol{P}}} = \left[ {\begin{array}{*{20}{c}} {{R_{\text{M}}}}&{{G_{\text{M}}}}&{{B_{\text{M}}}} \end{array}} \right]$ ${{{\boldsymbol{Q}}}^{\rm{T}}} = {{{\boldsymbol{T}}}_{{\text{CCM}}}}{{{\boldsymbol{P}}}^{\rm{T}}}$ 复合模型 ${{\boldsymbol{Q}}} = \left[ {\begin{array}{*{20}{c}} {\ln ({R_{\text{S}}})}&{\ln ({G_{\text{S}}})}&{\ln ({B_{\text{S}}})} \end{array}} \right]$ $ {{\boldsymbol{P}}} = \left[ {\begin{array}{*{20}{c}} {{R_{\text{M}}}}&{{G_{\text{M}}}}&{{B_{\text{M}}}}&1 \end{array}} \right] $ ${{{\boldsymbol{Q}}}^{\rm{T}}} = {{{\boldsymbol{T}}}_{{\text{CCM}}}}{{{\boldsymbol{P}}}^{\rm{T}}}$ 表 3 场景1图像评价指标参数
Table 3 Image evaluation index parameters of scene 1
图像 色差/NBS 饱和度 拉伸后图像 白平衡后图像 色彩校正图像 白平衡后图像 色彩校正图像 (a) 31.7691 29.7584 16.8068 0.1844 1.1775 (b) 31.1937 30.4833 18.9607 0.1635 1.0684 (c) 36.5345 29.0815 18.9607 0.2215 1.0684 (d) 30.4207 36.7243 20.2295 0.1331 1.1416 (e) 31.8976 41.8603 22.7804 0.1000 1.1341 (f) 34.1854 44.2036 25.6088 0.0947 1.1602 (g) 39.8942 48.1827 29.4266 0.0718 1.0503 (h) 49.5305 53.8235 27.1670 0.0285 0.8663 -
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