Carter W H
Appl Opt. 1982 Jun 1;21(11):1989-94. doi: 10.1364/AO.21.001989.
The actual focal plane for a laser beam under frequently encountered conditions is shifted from the plane given by geometrical optics. The concept of effective Fresnel number for an unapertured Gaussian laser beam is defined and used to examine focal shifts. It is found that the effective Fresnel number has a simple physical interpretation that makes clear its relationship to the focal shift phenomena. Expressions are obtained that relate the important Gaussian beam parameters to the effective Fresnel number, and a method of correcting for the focal shift in optical systems design is described.
在常见条件下，激光束的实际焦平面与几何光学所给出的平面存在偏移。定义了无孔径高斯激光束的有效菲涅尔数概念，并用于研究焦移。结果发现，有效菲涅尔数具有简单的物理解释，这使其与焦移现象的关系变得清晰。得到了将重要的高斯光束参数与有效菲涅尔数相关联的表达式，并描述了一种在光学系统设计中校正焦移的方法。
