Scope Overboard!

Sally B. Patterson

Researchers at Dalhousie University in Halifax, Nova Scotia, Canada, have developed a submersible holographic microscope that simplifies 3-D imaging of tiny marine life down to 100 m under the sea. Whereas such devices formerly weighed in at several tons, had to be deployed from ships and used film to garner a few images, the newcomer, slimmed down to only 20 kg, can be taken out on small boats and can record thousands of holograms in minutes.

Favella sp. were recorded in the ocean using a holographic microscope. Courtesy of M.H. Jericho.
The device, described in a report scheduled for publication in Review of Scientific Instruments, uses laser light focused through a pinhole, creating spherical waves that illuminate a sample of seawater. Waves scattered by objects in the water combine at a CCD camera with the reference wave from the pinhole to form digitized interference patterns. Holograms with 1024 × 1024 pixels can be recorded at 7 to 10 fps and transmitted via watertight Ethernet cable to a surface vessel, where software unravels them to reconstruct images of the objects.

The holographic microscope also can be used to produce movies of zooplankton and other microorganisms, enabling scientists to observe how the critters navigate in their home surf.