用于实时无损检测的兆赫兹轴向线速率中红外光学相干断层扫描
Mid-infrared optical coherence tomography with MHz axial line rate for real-time non-destructive testing
AI总结：
本文提出一种基于时间拉伸红外光谱的3-4微米波段高速中红外OCT系统，将A-scan速率从3 kHz提升至1 MHz，轴向分辨率11.6微米，灵敏度55 dB，为工业产品、文物和结构的实时无损检测开辟了新途径。
摘要：
无损检测（NDT）对于确保各行业的产品质量和安全至关重要。超声、太赫兹和X射线成像等传统方法在探头接触要求、深度分辨率或辐射风险方面存在局限性。光学相干断层扫描（OCT）是解决这些局限性的一种有前景的替代方案，但它受到强散射的影响，限制了其穿透深度。近年来，中红外（MIR）光谱区域的OCT因其散射率显著低于近红外区域而受到关注。然而，已报道的MIR-OCT最高A-scan速率为3 kHz，获取一幅图像需要较长的数据采集时间，无法满足工业实时诊断的需求。在此，我们提出了一种工作在3-4微米波段的高速MIR-OCT系统，该系统采用基于时间拉伸红外光谱的扫频源OCT技术。通过集成一台重复频率为50 MHz的宽带飞秒MIR脉冲激光器，我们实现了1 MHz的A-scan速率、11.6微米的轴向分辨率和55 dB的灵敏度。作为概念验证演示，我们对覆盖有高散射油漆涂层的基底表面进行了成像。所展示的A-scan速率比此前最先进水平高出两个数量级以上，为工业产品、文化资产和结构的实时无损检测铺平了道路。
英文摘要：
Non-destructive testing (NDT) is crucial for ensuring product quality and safety across various industries. Conventional methods such as ultrasonic, terahertz, and X-ray imaging have limitations in terms of probe-contact requirement, depth resolution, or radiation risks. Optical coherence tomography (OCT) is a promising alternative to solve these limitations, but it suffers from strong scattering, limiting its penetration depth. Recently, OCT in the mid-infrared (MIR) spectral region has attracted attention with a significantly lower scattering rate than in the near-infrared region. However, the highest reported A-scan rate of MIR-OCT has been 3 kHz, which requires long data acquisition time to take an image, unsatisfying industrial demands for real-time diagnosis. Here, we present a high-speed MIR-OCT system operating in the 3-4 um region that employs the swept-source OCT technique based on time-stretch infrared spectroscopy. By integrating a broadband femtosecond MIR pulsed laser operating at a repetition rate of 50 MHz, we achieved an A-scan rate of 1 MHz with an axial resolution of 11.6 um and a sensitivity of 55 dB. As a proof-of-concept demonstration, we imaged the surface of substrates covered by highly scattering paint coatings. The demonstrated A-scan rate surpasses previous state-of-the-art by more than two orders of magnitude, paving the way for real-time NDT of industrial products, cultural assets, and structures.
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