Abstract In this paper we propose super resolution measurement and post-processing strategies that can be applied in thermography using laser line scanning. The implementation of these techniques facilitates the separation of two closely spaced defects and avoids the expected deterioration of spatial resolution due to heat diffusion. The experimental studies were performed using a high-power laser as heat source in combination with pulsed thermography measurements (step scanning) or with continuous heating measurements (continuous scanning). Our work shows that laser line step scanning as well as continuous scanning both can be used within our developed super resolution (SR) techniques. Our SR techniques make use of a compressed sensing based algorithm in post-processing, the so-called iterative joint sparsity (IJOSP) approach. The IJOSP method benefits from both - the sparse nature of defects in space as well as from the similarity of each measurement. In addition, we show further methods to improve the reconstruction quality e.g. by simple manipulations in thermal image processing such as by considering the effect of the scanning motion or by using different optimization algorithms within the IJOSP approach. These super resolution image processing methods are discussed so that the advantages and disadvantages of each method can be extracted. Our contribution thus provides new approaches for the implementation of super resolution techniques in laser line scanning thermography and informs about which experimental and post-processing parameters should be chosen to better separate two closely spaced defects.

中文翻译：

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超分辨率激光线扫描热成像

摘要 在本文中，我们提出了可用于使用激光线扫描的热成像的超分辨率测量和后处理策略。这些技术的实施促进了两个紧密间隔的缺陷的分离，并避免了由于热扩散而导致的空间分辨率的预期恶化。实验研究是使用高功率激光作为热源结合脉冲热成像测量（步进扫描）或连续加热测量（连续扫描）进行的。我们的工作表明，激光线步进扫描和连续扫描都可以在我们开发的超分辨率 (SR) 技术中使用。我们的 SR 技术在后处理中使用基于压缩感知的算法，即所谓的迭代联合稀疏 (IJOSP) 方法。IJOSP 方法受益于两者 - 空间缺陷的稀疏性以及每次测量的相似性。此外，我们展示了进一步提高重建质量的方法，例如通过热图像处理中的简单操作，例如通过考虑扫描运动的影响或通过在 IJOSP 方法中使用不同的优化算法。讨论了这些超分辨率图像处理方法，以便提取每种方法的优缺点。因此，我们的贡献为在激光线扫描热成像中实施超分辨率技术提供了新方法，并告知应选择哪些实验和后处理参数以更好地分离两个紧密间隔的缺陷。