engleski

Digital holography at light levels below noise using photon-counting approach

Recording of digital holograms of a weak signal (0.44 counts per second (cps)) hidden below the detector's noise (21 cps) is investigated by employing high dynamic range of a photon- counting detector. Recording conditions are discussed in terms of the most important holographic measures, namely the fringe visibility (or contrast) and signal-to-noise ratio, and in relation to the main holographic parameters. Theoretically evaluated curves are tested by recording holograms for a wide range of the parameter values. We found that (i) optimum set of holographic parameters can be determined for a harsh signal conditions, (ii) increasing the visibility does not necessarily improve the more important signal-to-noise ratio, and (iii) in cases of nearly constant visibility the signal-to-noise ratio clearly reveals differences in the quality of holographic recordings.

holography; digital holography; photon counting; fringe analysis

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