Abstract
Holograms of colloidal dispersions encode comprehensive information about individual particles' three-dimensional positions, sizes and optical properties. Extracting that information typically is computationally intensive, and thus slow. Here, we demonstrate that machine-learning techniques based on support vector machines (SVMs) can analyze holographic video microscopy data in real time on low-power computers. The resulting stream of precise particle-resolved tracking and characterization data provides unparalleled insights into the composition and dynamics of colloidal dispersions and enables applications ranging from basic research to process control and quality assurance.
Highlights
Holograms of colloidal spheres obtained with holographic video microscopy [1, 2] can be interpreted with predictions of the Lorenz-Mie theory of light scattering [3] to track each particle in three dimensions, and to measure its size and refractive index [4]
Whereas nonlinear fitting typically requires more than a second on a 1 Gflop computer, a trained support vector machines (SVMs) can estimate the size, refractive index or axial position of a micrometer-scale sphere in under a millisecond on the same hardware
SVM-accelerated tracking can be used for real-time three-dimensional particletracking velocimetry [8]
Summary
Holograms of colloidal spheres obtained with holographic video microscopy [1, 2] can be interpreted with predictions of the Lorenz-Mie theory of light scattering [3] to track each particle in three dimensions, and to measure its size and refractive index [4]. State-of-the-art implementations [4,5,6,7] can locate a sphere and resolve its radius both to within a few nanometers, and can determine its refractive index to within a part per thousand [8,9,10]. The cost of this powerful technique is the computational burden of fitting each hologram pixel-by-pixel to theoretical predictions [4, 11]. Whereas nonlinear fitting typically requires more than a second on a 1 Gflop computer, a trained SVM can estimate the size, refractive index or axial position of a micrometer-scale sphere in under a millisecond on the same hardware
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