Abstract
Digital Holographic Microscopy (DHM) is a single shot interferometric technique, which provides quantitative phase images with subwavelength axial accuracy. A short hologram acquisition time (down to microseconds), allows DHM to offer a reduced sensitivity to vibrations, and real time observation is achievable thanks to present performances of personal computers and charge coupled devices (CCDs). Fast dynamic imaging at low-light level involves few photons, requiring proper camera settings (integration time and gain of the CCD; power of the light source) to minimize the influence of shot noise on the hologram when the highest phase accuracy is aimed. With simulated and experimental data, a systematic analysis of the fundamental shot noise influence on phase accuracy in DHM is presented.
Highlights
Digital Holographic Microscopy (DHM) is a recent quantitative phase imaging technique, which is developing rapidly, offering both sub-wavelength axial accuracy and real time observation capabilities
We proposed a general study of the signal-to-noise ratio of DHM phase images, based on the decision statistical theory proposed by Wagner and Brown [24], treating the effect of shot noise jointly with the influence of the intensity ratio between the reference and the object beams [25]
The results established in this work with simulations yield simple look-up tables to set the hologram acquisition parameters properly, or the number of reconstructed phase images used for averaging, to reach the targeted shot noise-limited phase accuracy in DHM required for a particular experiment
Summary
Digital Holographic Microscopy (DHM) is a recent quantitative phase imaging technique, which is developing rapidly, offering both sub-wavelength axial accuracy and real time observation capabilities. In the frame of digital holography, some studies concerning the noise reduction were proposed for specific applications: Monnom et al have demonstrated an improved visibility of the reconstructed intensity images by reducing the noise due to out-of-focus objects, but the resulting amelioration is not clearly quantified and the phase behavior is not considered [19]; Paganin et al investigated the effect of a uniformly distributed noise during the acquisition of the out-of-focus images required for their amplitude-based phase-retrieving algorithm; the results are only applicable to their phase sensitive technique [20]; Ruijter and Weiss have extensively discussed the detection limit in quantitative off-axis electron holography, but their estimation of the phase variance relies principally on the fringe visibility over the hologram zone from which the phase is deduced and this estimation is valid for objects with smooth phase variation only [21]; Mills and Yamaguchi have inspected the effect of the hologram quantization in phase-shifting digital holography, but have restricted their study to amplitude images [22]; Baumbach and al. For the first time to our knowledge, the influence of shot noise to the phase accuracy in DHM is clearly studied using both simulated and experimental data
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