FRINGE-FIELD QUANTIFICATION IN AN LDV PROBE VOLUME BY USE OF A MAGNIFIED IMAGE

The magnified cross-section of the LDV probe volume fringe field creat ed on a far screen (image plane) with an imaging lens is examined both analytically and experimentally. It is shown that measurements of the image plane fringe field can be used to quantitatively determine the fringe field existing within the probe volume. Because the fringe spac ing in the magnified image is more accessible experimentally, both lon gitudinal- and lateral-coordinate variations in fringe spacing can be determined, permitting a complete mapping of the fringe field. The det ailed knowledge of the fringe field thus obtained allows beam quality, alignment, and fringe uniformity to be evaluated with greater precisi on than is possible with other techniques.