Real-Time Holography Targets Biological Imaging

Scientists at Imperial College of Science, Technology and Medicine in London have demonstrated a holographic imaging system for wide-field optical sectioning that promises a depth resolution comparable to confocal microscopy and frame rates of up to 1000 per second.

Described in the Sept. 16 issue of Applied Physics Letters, the setup, which may be applied to the imaging of turbid media, including biological samples, is suitable for use with both reflected light and fluorescence imaging techniques.

The system, which combines structured illumination and light-in-flight holography, records real-time holograms of the sample using an AlGaAs/GaAs multiple quantum well structure. The reconstructed holograms are collected from the photorefractive medium by a cooled 12-bit CCD camera and are exposed by 842-nm radiation from a homebuilt diode-pumped Cr:LiSAF laser. In the demonstrations, the researchers imaged a US Air Force test chart under illumination by an 806-nm LED and a fluorescent film excited by a Ti:sapphire laser operating at 415 nm.