This document sets forth several acceptable methods of laser beam divergence measurement techniques.

The FAA has published FAA order 7400.2D as interim guidance on laser exposure levels near airports. The exposures in Las Vegas and the resulting moratorium on outdoor laser light shows led to a request from the International Laser Display Association for several measurement teams to go to Las Vegas to perform divergence measurements on a number of light show lasers. The purpose of these measurements was to find the most practical methods to determine beam divergence for laser safety calculations for a typical laser light show installation.

A comparison of divergence measurement techniques for laser light shows was conducted in Las Vegas, Nevada in March of 1996 (see Reference 1). Techniques compared included the long focal length lens and small aperture method, the two-point aperture method, the knife-edge measurement method, and use of a beam profiler. All methods were found to be accurate for most cases of field laser beam divergence measurements, although each was found to have certain limitations, depending upon the application. The two-point aperture method was considered by most participants to be the simplest, quickest, and most practical technique for laser safety measurement of laser light show beam divergence.