Aalipour Rasoul, Taghi Tavassoly Mohammad, Saber Ahad
Appl Opt. 2020 Sep 1;59(25):7712-7719. doi: 10.1364/AO.397748.
Measurement of the source size and specifying its effect on the spatial coherence of propagating light are important for characterizing distant sources such as stars, and imaging with partially coherent light. The common method for measuring spatial coherence is Young's two-pinhole experiment. For characterizing spatial coherence along a line, one needs to change the location of the pinholes over a large number of pairs of points. But it requires many measurements, which takes significant time. In this paper, we use Fresnel diffraction from a step in reflection to measure the source width and transverse coherence length. It is shown theoretically and experimentally that these quantities are determined by specifying the location of minimum visibility on the diffraction pattern. We utilize a sodium vapor lamp with a variable slit in front of it as an extended one-dimensional incoherent light source. The measurements are made through recording only one diffraction pattern formed by the step. The study is applicable in 2D, and one can characterize weak starlight using highly sensitive equipment.
测量光源尺寸并确定其对传播光的空间相干性的影响，对于表征恒星等遥远光源以及用部分相干光进行成像非常重要。测量空间相干性的常用方法是杨氏双针孔实验。为了沿一条线表征空间相干性，需要在大量的点对中改变针孔的位置。但这需要进行许多测量，会花费大量时间。在本文中，我们利用反射阶跃的菲涅耳衍射来测量光源宽度和横向相干长度。从理论和实验上表明，这些量是通过指定衍射图样上最小可见度的位置来确定的。我们使用一个前面有可变狭缝的钠蒸气灯作为扩展的一维非相干光源。仅通过记录由阶跃形成的一个衍射图样来进行测量。该研究适用于二维情况，并且可以使用高灵敏度设备来表征微弱星光。
