基于相关视角多视校正的太赫兹阵列雷达散斑抑制方法
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摘要
在针对人体安检的站开式太赫兹阵列雷达三维成像中,散斑效应严重影响了对体表隐藏违禁品的检测和识别性能,为此,对全息散斑进行有效抑制有着迫切的需要。利用目标旋转带来的角度自由度,结合目标散射对角度的敏感性,提出了一种基于相关视角多视校正的太赫兹全息雷达散斑抑制方法。在理论上推导了全息雷达散斑强度在相关角度照射下的归一化协方差表达式,给出了相关视角多视处理后的散斑对比度。在实验上利用340 GHz站开式MIMO阵列成像系统的快速成像的优势,对低速旋转目标在相关视角下的单视成像结果进行成像空间旋转校正、目标配准和多视处理。处理后散斑对比度降低至单视散斑的44%,散斑得到了有效抑制,目标轮廓明显,细节更加丰富。该方法能够在不增加系统复杂度的条件下有效抑制散斑噪声,实现图像增强。
In the MIMO based terahertz three-dimensional imaging radar for human security screening,the speckle effect affects the detection and recognition performance of hidden contraband seriously. For this reason, effective suppression of terahertz holographic speckle is demanded urgently. By using the angle based degree of freedom for speckle suppression obtained by the target rotation, a terahertz holographic radar speckle suppression method based on multi-look correction of correlation angle was proposed. Meanwhile, the angle sensitivity of the target scattering was carefully considered. In theory,the normalized covariance expression of the holographic radar speckle intensity under the relevant angle illumination was derived, and the speckle contrast after multi-view processing was given.Experimentally, based on the fast speed of the 340 GHz MIMO based imaging system, single-look images of low-speed rotating target were obtained. The imaging space rotation correction, target registration and multi-look processing were performed on each single-look image under the relevant viewing angle. The speckle contrast of the averaged reconstructed image was reduced to 44% of a single reconstructed image. The processed speckle was effectively suppressed with distinct target contour and details. The proposed method can effectively suppress speckle noise and achieve image enhancement without increasing system complexity.
In the MIMO based terahertz three-dimensional imaging radar for human security screening,the speckle effect affects the detection and recognition performance of hidden contraband seriously. For this reason, effective suppression of terahertz holographic speckle is demanded urgently. By using the angle based degree of freedom for speckle suppression obtained by the target rotation, a terahertz holographic radar speckle suppression method based on multi-look correction of correlation angle was proposed. Meanwhile, the angle sensitivity of the target scattering was carefully considered. In theory,the normalized covariance expression of the holographic radar speckle intensity under the relevant angle illumination was derived, and the speckle contrast after multi-view processing was given.Experimentally, based on the fast speed of the 340 GHz MIMO based imaging system, single-look images of low-speed rotating target were obtained. The imaging space rotation correction, target registration and multi-look processing were performed on each single-look image under the relevant viewing angle. The speckle contrast of the averaged reconstructed image was reduced to 44% of a single reconstructed image. The processed speckle was effectively suppressed with distinct target contour and details. The proposed method can effectively suppress speckle noise and achieve image enhancement without increasing system complexity.
引文
[1] Herschel R, Briese G, Lang S A, et al. Focused imaging by geometric optics for real-time passenger screening at submillimeter wave frequencies[C]//Microwave Conference,IEEE, 2017:1549-1552.
[2] Gao Jingkun, Cui Zhenmao, Cheng Binbin, et al. Fast threedimensional image reconstruction of a standoff screening system in the terahertz regime[J]. IEEE Transactions on Terahertz Science&Technology, 2018, 8(1):1-14.
[3] Sheen D M, Hall T E, Severtsen R H, et al. Active wideband 350 GHz imaging system for concealed-weapon detection[C]//SPIE, 2009, 7309:73090I.
[4] Patrick M A. Illumination strategies to reduce target orientation requirements and speckle in millimeter wave imaging[D]. USA:The Ohio State University, 2014.
[5] Jaeger I, Stiens J, Koers G, et al. Hadamard speckle reduction for millimeter wave imaging[J]. Microwave&Optical Technology Letters, 2006, 48(9):1722-1725.
[6] Jaeger I, Stiens J, Zhang Lixiao, et al. Comparison of speckle reduction diversity tools for active millimeter-wave imaging[J]. Journal of the Optical Society of America A Optics Image Science&Vision, 2008, 25(7):1716-1721.
[7] Xu Meifang, Ding Junwen, Wang Guanjun, et al.Comparison of laser speckle suppression due to angle diversity[J]. Infrared and Laser Engineering, 2017, 46(8):0806004.(in Chinese)徐美芳,丁俊文,王冠军,等.角度多样性激光散斑抑制方法的比较[J].红外与激光工程, 2017, 46(8):0806004.
[8] Petkie D T, Holt J A, Patrick M A, et al. Multimode illumination in the terahertz for elimination of target orientation requirements and minimization of coherent effects in active imaging systems[J]. Optical Engineering, 2012, 51(9):091604.
[9] Patrick M A, Joye C D, Lucia F C D, Multimode illumination for speckle reduction and angle neutrality in millim eter wave active imaging:range and time-resolved mode averaging[J]. Journal of the Optical Society of America A Optics Image Science&Vision, 2014, 31(10):2135-2141.
[10] Patrick M A, Holt J A, Joye C D, et al. Range resolved mode mixing in a large volume for the mitigation of speckle and strategic target orientation requirements in active millimeter-wave imaging[J]. Journal of the Optical Society of America A Optics Image Science&Vision, 2015, 32(4):637-646.
[11] Goodman J W. Speckle Phenomena in Optics:Theory and Applications[M]. Englewood:Roberts&Company, 2007.
[12] Cui Zhenmao, Gao Jingkun, Lu Bin, et al. Real time 3D imaging system based on sparse MIMO array at 340 GHz[J].Journal of Infrared and Millimeter Waves, 2017, 36(1):102-106.(in Chinese)崔振茂,高敬坤,陆彬,等. 340 GHz稀疏MIMO阵列实时3-D成像系统[J].红外与毫米波学报, 2017, 36(1):102-106.
[13] Jiang Yanwen, Qin Yuliang, Wang Hongqiang, et al. A sidelobe suppression method based on coherence factor for terahertz array imaging[J]. IEEE Access, 2018, 6:5584-5588.
[2] Gao Jingkun, Cui Zhenmao, Cheng Binbin, et al. Fast threedimensional image reconstruction of a standoff screening system in the terahertz regime[J]. IEEE Transactions on Terahertz Science&Technology, 2018, 8(1):1-14.
[3] Sheen D M, Hall T E, Severtsen R H, et al. Active wideband 350 GHz imaging system for concealed-weapon detection[C]//SPIE, 2009, 7309:73090I.
[4] Patrick M A. Illumination strategies to reduce target orientation requirements and speckle in millimeter wave imaging[D]. USA:The Ohio State University, 2014.
[5] Jaeger I, Stiens J, Koers G, et al. Hadamard speckle reduction for millimeter wave imaging[J]. Microwave&Optical Technology Letters, 2006, 48(9):1722-1725.
[6] Jaeger I, Stiens J, Zhang Lixiao, et al. Comparison of speckle reduction diversity tools for active millimeter-wave imaging[J]. Journal of the Optical Society of America A Optics Image Science&Vision, 2008, 25(7):1716-1721.
[7] Xu Meifang, Ding Junwen, Wang Guanjun, et al.Comparison of laser speckle suppression due to angle diversity[J]. Infrared and Laser Engineering, 2017, 46(8):0806004.(in Chinese)徐美芳,丁俊文,王冠军,等.角度多样性激光散斑抑制方法的比较[J].红外与激光工程, 2017, 46(8):0806004.
[8] Petkie D T, Holt J A, Patrick M A, et al. Multimode illumination in the terahertz for elimination of target orientation requirements and minimization of coherent effects in active imaging systems[J]. Optical Engineering, 2012, 51(9):091604.
[9] Patrick M A, Joye C D, Lucia F C D, Multimode illumination for speckle reduction and angle neutrality in millim eter wave active imaging:range and time-resolved mode averaging[J]. Journal of the Optical Society of America A Optics Image Science&Vision, 2014, 31(10):2135-2141.
[10] Patrick M A, Holt J A, Joye C D, et al. Range resolved mode mixing in a large volume for the mitigation of speckle and strategic target orientation requirements in active millimeter-wave imaging[J]. Journal of the Optical Society of America A Optics Image Science&Vision, 2015, 32(4):637-646.
[11] Goodman J W. Speckle Phenomena in Optics:Theory and Applications[M]. Englewood:Roberts&Company, 2007.
[12] Cui Zhenmao, Gao Jingkun, Lu Bin, et al. Real time 3D imaging system based on sparse MIMO array at 340 GHz[J].Journal of Infrared and Millimeter Waves, 2017, 36(1):102-106.(in Chinese)崔振茂,高敬坤,陆彬,等. 340 GHz稀疏MIMO阵列实时3-D成像系统[J].红外与毫米波学报, 2017, 36(1):102-106.
[13] Jiang Yanwen, Qin Yuliang, Wang Hongqiang, et al. A sidelobe suppression method based on coherence factor for terahertz array imaging[J]. IEEE Access, 2018, 6:5584-5588.