基于相关视角多视校正的太赫兹阵列雷达散斑抑制方法

Terahertz holographic radar speckle suppression method based on multi-look correction of correlation angle

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.