Measuring the deformation of building elements engulfed by flames is essential in fire research to improve safety in the event of a fire. Ideally, the measurement system should be non-contact, able to range at the millimeter to meter scale with sub-mm precision, and have sufficient speed to capture temperature-induced deformations of the target object. To date, no ranging technology has been demonstrated that meets those requirements while imaging through flames. Here, we show that coherent laser detection and ranging (LADAR) can provide three-dimensional images of objects hidden behind methane or acetylene flames with sufficiently high precision to track their deformation. The heterodyne detection of coherent frequency-modulated continuous-wave (FMCW) LADAR allows the ranging signal to be detected in the presence of strong radiation of the flames. We measure three-dimensional point clouds of diffusely scattering complex surfaces with a precision of less than 30 μm at 2-meter stand-off distance, despite soot-induced signal loss and steering (refraction) of the ranging laser by the flames. Movies of the heat-induced surface deformation of objects illustrate the temporal performance. These data show that FMCW LADAR can quantify the deformation and movement of objects in fires, when non-contact shape measurements at stand-off distances of multiple meters are crucial.

中文翻译：

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相干激光测距，可通过火焰精确成像

在火灾研究中，测量被火焰吞没的建筑元素的变形对于提高火灾发生的安全性至关重要。理想情况下，测量系统应该是非接触式的，能够在毫米到米的范围内以亚毫米的精度进行测量，并具有足够的速度来捕获温度引起的目标物体变形。迄今为止，还没有证明通过火焰成像时能够满足这些要求的测距技术。在这里，我们表明相干激光检测和测距（LADAR）可以以足够高的精度提供隐藏在甲烷或乙炔火焰后面的物体的三维图像，以跟踪其变形。相干调频连续波（FMCW）LADAR的外差检测可以在火焰强烈辐射的情况下检测测距信号。尽管有烟灰引起的信号损失和测距激光被火焰控制（折射），我们仍可以在2米的对距距离处测量散布散射复杂表面的三维点云，其精度小于30μm。影片的热诱导对象的表面变形说明了时间性能。这些数据表明，FMCW LADAR可以量化火灾中物体的变形和运动，这对于在几米远距离处进行非接触式形状测量至关重要。影片的热诱导对象的表面变形说明了时间性能。这些数据表明，FMCW LADAR可以量化火灾中物体的变形和运动，这对于在几米远距离处进行非接触式形状测量至关重要。影片的热诱导对象的表面变形说明了时间性能。这些数据表明，FMCW LADAR可以量化火灾中物体的变形和运动，这对于在几米远距离处进行非接触式形状测量至关重要。