Advancing plenoptic / lightfield imaging for optical diagnostics

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Experimental research into the motion of fluids, aerodynamics and microscale flows in academic and industrial applications is now dominated by digital techniques. Cameras are used to take images of tracer particles seeded into the flow to track their movement, inferring fluid motion. This technology, based on particle image velocimetry (PIV) and particle tracking velocimetry (PTV) has been developed over the last 30 years to a point where it is now compatible with even the most detailed computer simulations. Importantly, these experimental techniques include all of the physics of the flow problem. However, they can be costly and require significant expertise to set up and operate. _A new approach to collect images of particle locations over three dimensions (3D) from a single camera will be researched, investigated and developed, as part of my continuing research program developing optical instrumentation. It is based on collecting the entire light field seen by the camera, not just what is brought into focus by the main lens. Termed light-field or plenoptic imaging, the camera has a microlens array in front of the sensor that allows small angle perspective viewing of particle locations. In many ways, this is similar to how insects with compound eyes view the world. This type of imaging system, using only a single camera, promises to be significantly easier to install and setup in a flow system, especially where viewing access is limited. It will also allow, for the first time, realistic measurement of three-dimensional flows at the microscale such as the flow in porous media and microscale biological flows where perspective viewing is extremely limited. The evaporation of a water droplet on a surface, which has received much academic interest and is extremely challenging within which to take measurements, will be used to test the limits of the technique and theory of its use. The program will continue to develop this type of camera system for experimental use by addressing a number of fundamental question for which there is limited research available in the literature. These include developing a general calibration procedure, a general optical model based on ray tracing to describe the imaging process, processing of image data to define objects in 3-D space and advanced approaches based on PTV and numerical models of particle motion to provide high-quality flow measurement. Being able to collect high quality data at the microscale flows, for which there are currently limited approaches, will have significant impact both in academia and industry, allowing understanding of the nature and science of important problems such as diffusion and evaporation. The program will also train students in the areas of mechanical engineering, optical instrumentation and fluid mechanics, developing new knowledge and science. Students will work in a professional environment, receiving supplementary training making them highly sought after by industry and academia.