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Marc Levoy; Synthetic Aperture Photography and Microscopy by Recording and Processing the 4D Light Field. Journal of Vision 2007;7(15):20. doi: https://doi.org/10.1167/7.15.20.
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Light field photography is a technique for recording light intensity as a function of position and direction in a 3D scene. Unlike conventional photographs, light fields permit manipulation of viewpoint and focus after the imagery has been recorded. At Stanford we have built a number of devices for capturing light fields, including (1) an array of 128 synchronized video cameras, (2) a handheld camera in which a microlens array has been inserted between the main lens and sensor plane, and (3) a microscope in which a similar microlens array has been inserted at the intermediate image plane. The third device permits us to capture light fields of microscopic biological (or industrial) objects in a single snapshot. Although diffraction limits the product of spatial and angular resolution in these light fields, we can nevertheless produce useful perspective flyarounds and 3D focal stacks from them. Since microscopes are inherently orthographic devices, perspective flyarounds represent a new way to look at microscopic specimens. Focal stacks are not new, but manual techniques for capturing them are time-consuming and hence not applicable to moving or light-sensitive specimens. Applying 3D deconvolution to these focal stacks, we can produce a set of cross sections, which can be visualized using volume rendering. Ours is the first technology (of which we are aware) that can produce volumetric models from a single photograph. In this talk, I will describe a prototype light field microscope and show perspective views, focal stacks, and reconstructed volumes for a variety of biological specimens. I will also survey some promising directions for this technology. For example, by introducing a second microlens array and a video projector, we can control the light field arriving at a specimen as well as the light field leaving it. Potential applications of this idea include microscope scatterometry - measuring reflectance as a function of incident and reflected angle, and “designer illumination” - illuminating one part of a microscopic object while avoiding illuminating another.
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