ABSTRACT

We have obtained an analytical expression for the surface temperature of a sample that is moving at constant velocity when it is illuminated by a modulated and focused laser beam, which remains at rest. From this expression it is found that while the temperature amplitude thermogram shows the expected elongated shape in the direction of the sample movement, the phase thermogram surprisingly shows a cylindrical symmetry about the position of the laser spot. To the best of our knowledge this is the first time that such a mismatch between amplitude and phase is found in photothermal experiments. This behaviour is confirmed from lock-in thermography experiments on moving samples. Moreover, the temperature (amplitude and phase) profiles in both directions, parallel and perpendicular to the sample movement, show a linear behaviour from whose slopes the in-plane thermal diffusivity of the moving sample can be obtained.

摘要

我们获得了一个样品的表面温度的解析表达式，该样品在被静止的调制激光聚焦后，以恒定速度运动。从该表达式可以发现，尽管温度幅度热谱图在样品移动的方向上显示出预期的细长形状，但相位热谱图出乎意料地显示了围绕激光光斑位置的圆柱对称性。据我们所知，这是第一次在光热实验中发现振幅和相位之间的不匹配。通过对移动样本进行锁定式热成像实验可以确认此行为。此外，温度（幅度和相位）在与样品移动平行和垂直的两个方向上的分布图，