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Hal Gee

Publications and source records attributed to Hal Gee.

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Correlation Revival Eigenmodes for Differential Sensitivity in Speckle Metrology

Speckle metrology exploits the high sensitivity of scattered fields to parameters of interest, yet this also leaves measurements vulnerable to unintended perturbations. Here we employ transmission matrix formalism to engineer light fields that produce speckle correlation "revivals", selectively reducing response to a chosen parameter. In a multimode fiber scattering system, we suppress bending-induced correlation changes over a limited curvature range without strongly degrading wavelength sensitivity, opening a route to tailored, parameter-specific sensitivities of speckle-based measurements.

physics.optics

Fiber-based high-speed fringe projection profilometry

Phase shift profilometry has become a standard technique for recording the surface of an object using the projection of sinusoidal patterns. We present a method of projecting the patterns via a pair of single-mode optical fibers mounted within a needle. The system presented can capture sub-millimetre precision depth profiles at 60 frames per second. The key features of the system that enable the high-speed imaging are the creation of an automated calibration system and developments in the image unwrapping and reconstruction algorithms to produce high fidelity surface measurements. These methods produce a compact projection system capable of accurate and fast profilometry.

physics.optics