Abstract
We study the noise of the intensity variance and of the intensity correlation and structure functions measured in light scattering from a random medium in the case when these quantities are obtained by averaging over a finite number N of pixels of a digital camera. We show that the noise scales as 1/N in all cases and that it is sensitive to correlations of signals corresponding to adjacent pixels as well as to the effective time averaging (due to the finite integration time) and spatial averaging (due to the finite pixel size). Our results provide a guide to estimation of noise levels in such applications as multi-speckle dynamic light scattering, time-resolved correlation spectroscopy, speckle visibility spectroscopy, laser speckle imaging etc.
Highlights
The statistical properties of optical speckle patterns resulting from scattering of light from a random medium are largely independent of the nature of the latter [1]
We study the noise of the intensity variance and of the intensity correlation and structure functions measured in light scattering from a random medium in the case when these quantities are obtained by averaging over a finite number N of pixels of a digital camera
Our results provide a guide to estimation of noise levels in such applications as multi-speckle dynamic light scattering, time-resolved correlation spectroscopy, speckle visibility spectroscopy, laser speckle imaging etc
Summary
The statistical properties of optical speckle patterns resulting from scattering of light from a random medium are largely independent of the nature of the latter [1]. One of the earliest applications is dynamic light scattering (DLS), known as photon correlation spectroscopy (PCS), where the fluctuations of the far-field speckle are analyzed [2]. The same method applied to turbid media is known as diffusing-wave spectroscopy (DWS) In both DLS and DWS, one usually makes use of the ergodicity of intensity fluctuations and replace ensemble averaging by time averaging. Desirable to increase the speckle size with respect to the size of the camera pixel (to mimic a point-like detector) and to reduce correlation of signals detected by neighboring pixels These two objectives are mutually exclusive, at least if one wishes to exploit signals from all available pixels of the image sensor. We start by considering the variance of intensities in a stationary speckle patterns and extend our analysis to the time correlation function and the intensity structure function of dynamic speckle patterns
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