Comeron Adolfo, Sicard Michaël, Kumar Dhiraj, Rocadenbosch Francesc
Department of Signal Theory and Communications, Remote Sensing Laboratory, Universitat Politècnica de Catalunya, Barcelona, Spain.
Appl Opt. 2011 Oct 1;50(28):5538-44. doi: 10.1364/AO.50.005538.
This paper presents a method to compute the overlap function of a lidar system in which a step-index optical fiber (or a bundle of such fibers) is used to carry the light collected by the telescope to the photoreceiver and a field lens is placed between the telescope and the optical fiber to increase the receiver field of view (FOV). The use of field lenses is a classical way to increase the FOV of radiometric systems (such as the receiving part of a lidar) when there is no numerical aperture (NA) limitation after the lens. However, when such a limitation exists, as in the case studied here, it will place a limit on the maximum attainable FOV. In the case of lidars, which have range-resolution capabilities, the limited FOV has an effect on the fraction of power coming from scattering volumes at different ranges that actually reaches the photodetector. This fraction is a function (the so-called overlap function) of the range of the scattering volume and its behavior has an impact on the accuracy of the retrievals. The application of the method developed in this paper shows that, in spite of the fiber NA limit, in practical situations the goal is attained of making the overlap function steeper and reaching higher values by using a field lens.
本文提出了一种计算激光雷达系统重叠函数的方法，其中使用阶跃折射率光纤（或一束此类光纤）将望远镜收集的光传输到光接收器，并在望远镜和光纤之间放置一个场镜以增加接收器的视场（FOV）。当透镜后的数值孔径（NA）没有限制时，使用场镜是增加辐射测量系统（如激光雷达的接收部分）视场的经典方法。然而，当存在这种限制时，如本文所研究的情况，它将对可达到的最大视场施加限制。对于具有距离分辨率能力的激光雷达，有限的视场会影响来自不同距离散射体的实际到达光电探测器的功率份额。该份额是散射体距离的函数（即所谓的重叠函数），其行为会对反演的准确性产生影响。本文所开发方法的应用表明，尽管存在光纤NA限制，但在实际情况下，通过使用场镜仍能实现使重叠函数更陡峭并达到更高值的目标。
