In-Situ Forward Scatter And Transmittance Measurement Using A Low Power Laser Diode

F. M. Caimi; R. F. Tusting; G. Kennedy

doi:10.1117/12.943323

27 September 1984 In-Situ Forward Scatter And Transmittance Measurement Using A Low Power Laser Diode

F. M. Caimi, R. F. Tusting, G. Kennedy

Proceedings Volume 0489, Ocean Optics VII; (1984) https://doi.org/10.1117/12.943323
Event: Ocean Optics VII, 1984, Monterey, United States

Abstract

A laser diode combined transmittance and low-angle scatterance measuring instrument is described for in situ use over long periods. Two methods of optical feedback are used to improve the stability of the 800 nm wavelength output. Use of a laser diode provides several advantages not otherwise easily achieved: 1) A possibility for narrow spectral filtering to reject ambient light. 2) Beam collimation of nearly 1 milliradian. 3) Higher light thru-put to facilitate the scattering measurement using a low total power consumption of 300 mW. Improved accuracy and sensitivity are salient features. Although operation in the near infrared produces less theoretical scattering signal than shorter wavelength instruments, the loss is substantially compensated by the large spectral radiant efficiency of the laser diode. Synchronous detection is used and the instrument is easily modifiable to sense multiple forward scattering angles. Inclusion of scatterance measurement in addition to transmittance not only provides more information per instrument deployed, but also provides greater usefulness in very clear waters when compared to a conventional transmissometer alone. Results are given which support identification of particle suspension mixtures of known characteristics. Particle size information may also be obtained in certain instances.

Citation Download Citation

F. M. Caimi, R. F. Tusting, and G. Kennedy "In-Situ Forward Scatter And Transmittance Measurement Using A Low Power Laser Diode", Proc. SPIE 0489, Ocean Optics VII, (27 September 1984); https://doi.org/10.1117/12.943323

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