In Pulse-Compression Thermography, the impulse response of the Sample Under Test is retrieved pixelwise by applying a proper matched filter on the set of acquired thermal images obtained by stimulating the system with a heat source amplitude – modulated by a proper coded signal. Linear frequency-modulated chirp signals and binary codes are the most employed coded excitations, and to improve the detection capability of the technique, a non-linear frequency-modulated chirp signal can be used to deliver more energy to the sample in a frequency range of interest. In this work, we report the application of an exponential chirp to modulate the heating source and we compare it with a standard linear chirp excitation. To do a fair comparison, various windowing functions have been applied on the matched filters to reduce range side lobes, thus enhancing the retrieved impulse response quality. It is shown that the combined use of an exponential chirp and an appropriate matched filter obtained by exploiting the Reactance Transform window provides a faithful reconstruction of the sample impulse response and an enhanced signal-to-noise ratio with respect to the use of linear chirp. This has been demonstrated on a 3D-printed polymethyl methacrylate (PMMA) sample containing 16 flat-bottom holes of different depths.

在脉冲压缩热成像技术中，通过对获取的热图像集应用适当的匹配滤波器，对获得的被测样品的脉冲响应进行逐像素检索，该图像通过用热源振幅（由适当的编码信号调制）刺激系统而获得。线性调频线性调频信号和二进制编码是最常用的编码激励，并且为了提高该技术的检测能力，可以使用非线性调频线性调频信号将更多能量传递给样品。利益。在这项工作中，我们报告了指数线性调频调制调制热源的应用，并将其与标准线性线性调频调制激励进行了比较。为了进行公平的比较，已在匹配的滤波器上应用了各种加窗功能，以减小范围旁瓣，从而提高了检索到的脉冲响应质量。结果表明，相对于线性线性调频信号的使用，指数线性调频信号和通过利用电抗变换窗口获得的适当匹配滤波器的组合使用可以忠实地重构采样脉冲响应，并提高信噪比。这在包含16个不同深度的平底孔的3D打印的聚甲基丙烯酸甲酯（PMMA）样品上得到了证明。