Quantitative analysis of hidden particles diffusing behind a scattering layer using speckle correlation

Area of Science:

• Optics and Photonics
• Biophysics
• Materials Science

Background:

• Speckle-correlation imaging utilizes the "memory effect" to visualize objects through opaque layers.
• Dynamic processes, like particle diffusion, present unique challenges for imaging through scattering media.

Purpose of the Study:

• To apply correlation analysis to quantitative imaging of dynamic fluorescent beads.
• To determine particle diffusion constants and counts using speckle patterns.
• To assess the applicability of the method for varying scattering layer thicknesses.

Main Methods:

• Utilized an epi-fluorescence microscope with speckled illumination and detection.
• Calculated spatio-temporal cross-correlation of detection speckle patterns.
• Analyzed correlation as a function of lag time and spatial shift.

Main Results:

• Successfully quantified the diffusion constant of fluorescent beads.
• Determined the number of fluorescent particles without phase retrieval.
• Demonstrated method utility even when the "memory effect" range is limited.

Conclusions:

• Correlation analysis of speckle patterns provides a robust method for quantitative imaging of dynamic systems.
• The technique is effective for measuring particle diffusion and concentration.
• The method's independence from the "memory effect" range broadens its applicability to diverse scattering scenarios.