Quantifying dynamics in 3D with light field and differential dynamic microscopy

In most microscopy platforms, the dynamics of soft matter and biological materials are most easily quantified in a two-dimensional plane. Measuring dynamics perpendicular to the focal plane often requires scanning-based methods that sacrifice time resolution or methods that require complex calibrations and analysis. Here, we describe how dynamics quantification in all three spatial dimensions can be achieved by combining light field microscopy (LFM) with differential dynamic microscopy (DDM). LFM allows one to perform single-shot 3D imaging using a widefield microscope by incorporating a microlens array into the optical train. Research with LFM systems has largely focused on optimizing volume reconstruction processes, particularly with the goal of fine spatial resolution. We circumvent the volumetric reconstruction process and employ DDM on the raw light field data. DDM has emerged as an effective technique for quantifying dynamics in soft and biological matter. It uses microscope-acquired movies to obtain scattering-like data and does not rely on the need to localize or segment images. Therefore, we can use LFM and DDM together to extract dynamics in 3D even for samples with low signal to noise. We demonstrate our system's performance by measuring diffusion coefficients in all three dimensions of colloidal microspheres with a scanning-free widefield microscope.