Optical arrangement for gas analysis using Raman spectroscopy

摘要

The arrangement comprises two concave mirrors (3a,3b). The laser beam (1) passes through two lenses (2a,2b) to focus at a centre point between the mirrors in a multipass arrangement on the formula w0 = lambda /(2 pi )<1.5>{D(2R-D)<0.25> with a tolerance of + or - 20% where lambda is laser wave length, D distance between mirror centres and R radii of curvature. The scatter radiation from the test sample between the two mirrors is thrown back on itself by a third concave mirror (4), preferably of the same radius, and directed to a grid (5) and then a receiver (6) and evaluator (7). The system uses the minimum number of optical components compatible with the lowest possible light losses.