Spatial optical coherence filtering is investigated as a means of reducing the amount of scattered light collected by an underwater laser system in turbid water. This approach exploits differences in coherence between unscattered and scattered laser light as a means of discrimination against scattered light prior to opto-electronic detection. An all optical filter is designed and tested that uses an axicon and a mask to pass the coherent, unscattered light while blocking the incoherent, scattered light. Experiments are performed in a laboratory water test tank to measure the effectiveness of the filter in reducing scattered light collection. The results obtained using the axicon filter are compared to those obtained using no filtering and using a conventional spatial filter. The axicon filter is shown to reduce the contribution of scattered light relative to either other test case.

Date Published: 10 May 2019
PDF: 10 pages
Proc. SPIE 11014, Ocean Sensing and Monitoring XI, 1101406 (10 May 2019); doi: 10.1117/12.2519103

Published in SPIE Proceedings Vol. 11014:
Ocean Sensing and Monitoring XI
Weilin "Will" Hou; Robert A. Arnone, Editor(s)