Perturbation of an optical beam over a laboratory path in the presence of focusing zones

An investigation is made of a perturbation in the vicinity of focal points over a laboratory path of a laser beam used in the processing of materials. The following situations are considered: a beam emerges from a focal point and expands; horizontal and vertical beams focused on a control surface. Rigorous numerical solutions are obtained of the aero-optics equations describing beam perturbations in front and behind the focal plane. The results are compared with the experimental data.