A standoff methane (CH4) sensor with actual hard topographic targets (usually called non-cooperative targets) is essential for natural gas pipeline leakage inspection and many other practical applications. To address this requirement, a miniaturized and low-power-consumption gas sensor was developed based on tunable diode laser absorption spectroscopy for standoff CH4 detection with a non-cooperative target. Wavelength modulation spectroscopy with a 1f normalized 2f detection method was employed for calibration-free CH4 measurement. A Kalman filter algorithm was used to improve the precision of the detection. The performance of the standoff CH4 sensor was evaluated comprehensively under various conditions, including different incident angles, different hard topographic targets, and different standoff distances. The results show that the measurement precision is 0.107% and the sensitivity is 4.08 parts per million per meter (ppm·m) with a time resolution of 1 s and a standoff distance of 40 m. The detection limit can achieve 1.24 ppm·m at an optimal integration time of 70 s. This sensor can be easily integrated into mobile platforms, which lays the foundation for intelligent leak inspection.

中文翻译：

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微型便携式激光气体传感器，用于非合作目标的远距离甲烷检测。

具有实际硬地形目标（通常称为非合作目标）的远距离甲烷 (CH4) 传感器对于天然气管道泄漏检查和许多其他实际应用至关重要。为了满足这一要求，我们开发了一种基于可调谐二极管激光吸收光谱的小型化、低功耗气体传感器，用于非合作目标的远距离 CH4 检测。采用 1f 归一化 2f 检测方法的波长调制光谱进行免校准 CH4 测量。采用卡尔曼滤波算法提高检测精度。在不同的入射角、不同的硬地形目标和不同的相距距离等多种条件下对相距CH4传感器的性能进行了综合评估。结果表明，测量精度为0.107%，灵敏度为4.08ppm·m，时间分辨率为1 s，测量距离为40 m。在70 s的最佳积分时间下，检测限可达到1.24 ppm·m。该传感器可以轻松集成到移动平台中，为智能泄漏检测奠定了基础。