Millimeter-wave (MMW) multiple-input multipleoutput synthetic aperture radar (MIMO-SAR) system is a technology that can achieve high resolution, high frame rate, and allweather imaging and has received extensive attention in the nondestructive testing and internal imaging applications of layered dielectric targets. However, the non-ideal scattering effect caused by dielectric materials can significantly deteriorate the imaging quality when using the existing MIMO-SAR fast algorithms. This paper proposes a rapid, high-quality dielectric target-enhanced imaging algorithm for a new universal non-uniform MIMO-SAR system. The algorithm builds on the existing non-uniform MIMO-SAR dielectric target frequency-domain algorithm (DT-FDA) by constructing a forward sensing operator and incorporating it into the alternating direction method of multipliers (ADMM) framework. This approach avoids large matrix operations while maintaining computational efficiency. By integrating an optimal regularization parameter search, the algorithm enhances the image reconstruction quality of dielectric internal structures or defects. Experimental results show the proposed algorithm outperforms IBP and DT-FDA, achieving better focusing, sidelobe suppression, and 3D imaging accuracy. It yields the lowest image entropy (8.864) and significantly improves efficiency (imaging time: 15.29 s vs. 23295.3 s for IBP).

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Since its unique advantages in the trade-off between data acquisition rate and hardware cost, the scanning 1D multipleinput-multiple-output (MIMO) array setup has been widely used in nondestructive testing (NDT) applications, especially for product quality control on the assembly line. In this article, two fast fully focused algorithms based on scanning 1D MIMO array are developed for imaging half-space medium structures. Both of the algorithms are derived under the half-space Green's function, and are implemented through fast Fourier transform (FFT) and phase compensation. The only difference between these two algorithms is that the matrix multiplication and nonuniform FFT (NUFFT) are respectively employed to reconstruct the range profile. Simulation and experimental results verify the effectiveness of the proposed algorithms in computation efficiency and image reconstruction quality.

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