We present an analysis of the shoulder-shaped power spectrum observed in the modulated laser output due to feedback light scattered from dynamic changes in self-mobile phytoplankton with flagella in seawater performed using a self-mixing laser Doppler vibrometry system. The power spectrum occasionally has shoulder-shaped broad frequency components superimposed on a Lorentz-type spectrum. This reflects the translational motion of phytoplankton moving across the beam-focus area. The velocity of phytoplankton in the focus area can be obtained by applying a curve fitting procedure to the power spectrum. Moreover, the average velocity and the velocity distribution of phytoplankton can be determined from curve fitting of the long-term power spectrum.
© 2009 Optical Society of America
Remote Sensing and Sensors
Original Manuscript: April 28, 2009
Manuscript Accepted: June 24, 2009
Published: July 9, 2009
Vol. 4, Iss. 9 Virtual Journal for Biomedical Optics
Seiichi Sudo, Takayuki Ohtomo, Yohei Takahashi, Tomohiko Oishi, and Kenju Otsuka, "Determination of velocity of self-mobile phytoplankton using a self-mixing thin-slice solid-state laser," Appl. Opt. 48, 4049-4055 (2009)