ABSTRACT
Holography is an interferometric technique that relies upon coherent interference between a clear reference beam and a so-called object beam transmitted through, or reflected by, a sample of interest. Holography with electron waves has been used for three-quarters of a century; Gabor invented the technique as an attempt to improve the resolution of the electron microscope. Because nearly all of the illuminating photons are captured, low-power excitation sources can be used-specifically milliwatt diode lasers, which are available in a large range of wavelengths. Following recording, reconstruction may be undertaken on a computer as a postprocessing step. A large body of literature exists on reconstruction of amplitude and phase images from digital holograms. The signal-to-noise ratio (SNR) in raw reconstructions of biological samples is much lower than that seen in fluorescence microscopy. The optical design aimed to achieve this by minimizing on-axis optical interfaces.
