Whitford B G
Appl Opt. 1972 Sep 1;11(9):2069-74. doi: 10.1364/AO.11.002069.
A light beam generated by two laser-illuminated circular apertures in a plane screen and two properly adjusted phase-shifting glass plates exhibits a central irradiance minimum that makes it favorable for alignment applications. The far-field transverse irradiance distribution in such a beam is here determined theoretically and experimentally to facilitate appraisal of its suitability for this purpose. Criteria aiding optimization of the beam and factors that degrade the beam and produce alignment errors are discussed. Alignment accuracy depends upon correspondence of a reference beam to a mathematically ideal, perfectly symmetrical shape. It is shown that a beam closely approaching the ideal can be easily produced by this method. Alignment accuracy is then found to be limited chiefly by air turbulence and stray light, which in the experimental investigation limited precision to +/- 10 /microm at 8.2 m.
由平面屏幕上两个激光照射的圆形孔径以及两块适当调整的相移玻璃板产生的光束呈现出中心辐照度最小值，这使其有利于对准应用。本文从理论和实验两方面确定了这种光束的远场横向辐照度分布，以便于评估其在此用途上的适用性。讨论了有助于光束优化的标准以及使光束退化并产生对准误差的因素。对准精度取决于参考光束与数学上理想的、完美对称形状的对应程度。结果表明，通过这种方法可以很容易地产生接近理想的光束。然后发现对准精度主要受空气湍流和杂散光的限制，在实验研究中，精度在8.2米处被限制在±10微米。
