Backprojection (BP) algorithm is successfully used to focus the layered scenes using ground-penetrating radar data. However, the BP algorithm with the time-consuming refraction point computation is impractical to autofocus in the layered scenes lacking medium information, where iterative focusing for estimating information continuously accumulates the calculation time of refraction points. Therefore, we propose a refraction point estimation (RPE)-based BP algorithm for autofocusing technique in unknown layered scenes. Our RPE algorithm, including two steps, directly expresses the refraction point. The first step coarsely estimates an initial position using an adjustment factor. Subsequently, the second step precisely converts the quartic equation of the refraction point into a linear form subject to the coarse estimation. Following this, we propose an RPE-based BP autofocusing technique to efficiently complete information estimation and refocusing. Compared with the existing algorithms, the proposed RPE algorithm directly estimates the refraction point and avoids iteration. The results indicate that the RPE-based BP algorithm has significant advantages in efficiency and accuracy, prompting the practical application of the BP autofocusing in unknown layered scenes.

中文翻译：

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使用探地雷达数据的未知分层场景中基于折射点估计的反投影自动对焦技术

反投影（BP）算法成功地用于使用探地雷达数据聚焦分层场景。然而，BP算法的折射点计算耗时，在缺乏介质信息的分层场景中自动对焦是不切实际的，在这种情况下，用于估计信息的迭代对焦不断累积折射点的计算时间。因此，我们提出了一种基于折射点估计 (RPE) 的 BP 算法，用于未知分层场景中的自动对焦技术。我们的 RPE 算法，包括两个步骤，直接表示折射点。第一步使用调整因子粗略估计初始位置。随后，第二步将折射点的四次方程精确地转换为线性形式进行粗略估计。按照此，我们提出了一种基于 RPE 的 BP 自动对焦技术，以有效地完成信息估计和重新对焦。与现有算法相比，本文提出的RPE算法直接估计折射点，避免了迭代。结果表明，基于RPE的BP算法在效率和准确性方面具有显着优势，促进了BP自动对焦在未知分层场景中的实际应用。