Digital holographic imaging of microorganisms

Abstract

Imaging aquatic microorganisms in 3D space is of interest to biologists and ocean scientists seeking to understand the behavior of these organisms in their natural environments. In this research, digital holographic imaging (DHI), with a 4f system providing transverse magnification of 9.1, is used to study such microorganisms. To test the imaging technique, DHI was used to locate and track 10 micrometer Dunaliella freely swimming in a 30 milliliter tank of artificial ocean water. Multiple holograms were recorded onto one frame with laser pulsing to identify short algae trajectories. An automatic algae locating program was designed, but the signal to noise ratio was too low, and therefore the program could only locate algae reliably with manual confirmation. With refinement to the experimental setup, the signal to noise ratio could be increased, and this imaging technique could be used to analyze many systems of aquatic microorganisms interacting in a 3D space.