Optical Diagnostics Group

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Current research areas

Optical diagnostics provide greater understanding and control of scientific, biological and engineering systems. Light adds no extra mass or stiffness to the structure and measurements can be made at many points simultaneously under service conditions. We research novel optical techniques for measuring deformation, vibration, shape and fluid flow. Jointly with our collaborators, we apply them to unique measurement problems in science and engineering.

 

 

Coherence holography

 

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Conventional holography records and reconstructs a 3-D image of an object represented by the optical field distribution and has found wide application in high-resolution volume imaging, interferometry and optical data storage. We are interested in a new type of holography, referred to as coherence holography, where the information of the 3-D image is encoded into the spatial coherence function of the reconstructed optical field. Through this method, we have pioneered a number of experiments exploring the fundamental studies and application of optical coherence, including coherence synthesis, coherence imaging, and coherence vortex.

 

Speckle photography and Optical vortex metrology

 

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Speckle photography is an advanced experimental technique used widely for surface inspection, vibration and strain measurements in solid mechanics, as well as various inspections of density, velocity and temperature fields in gas, liquid, and plasma flows. We are interested in fundamental studies of the statistics of optical fields and its application to optical metrology, including Optical Vortex Metrology based on information of phase singularities in speckle, and pseudo-phase correlation techniques for various industrial, and bio-optical measurements.

 

Speckle interferometry

 

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We are developing optical techniques for the measurement of transient vibrations in engineering test objects at a number of points simultaneously. Simultaneous, multi-point measurements of transient, non-repeating, events can assist in product testing, development and modal analysis. We are interested in speckle pattern interferometry, high-speed temporal phase stepping, spatial phase stepping, novel detectors and image / fringe processing techniques.

 

Polarimetry

 

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The measurement of polarization provides a powerful diagnostic tool for the study of various optical properties of a material, including birefringence, dichroism, and scattering. We are interested in both fundamental studies in polarization phenomena in nature and applications of polarimetric interferometry for biomedical and industrial diagnostic, including polarized spectrum analysis and polarization-sensitive coherence tomography.

 

4D shape measurement

 

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Non-contact optical techniques can enable free-form surfaces to be measured accurately and quickly. We are interested in geometric non-contact optical techniques for shape measurement (as opposed to interferometric or time-of-flight methods) including fringe and line projection, photogrammetry and photometric stereo. Applications in which the shape changes dynamically include measuring the shape of insect wings during flight, particle tracking velocimetry for measuring fluid flows and integrating optical techniques with coordinate measuring machine (CMM) measurements.

 

Iterative laser forming

 

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A laser beam can be scanned over a specimen surface and introduce thermal gradients that produce localized plastic deformation. On cooling, tensile stresses orthogonal to the laser scan path cause the material to bend and/or shorten, depending on the process parameters and specimen geometry. As a potential new manufacturing technology, it will allow for the redesign of key components and for the adjustment and alignment of parts. We have devised the first control algorithm for automated, iterative forming of doubly-curved surfaces, using a simplified model for laser forming that incorporates calibration data for both bending and membrane strain.

  

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Contact:  Prof. Andrew Moore  a.moore –at– hw.ac.uk