24 October 2012 Using a plenoptic camera to measure distortions in wavefronts affected by atmospheric turbulence
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Abstract
Ideally, as planar wave fronts travel through an imaging system, all rays, or vectors pointing in the direction of the propagation of energy are parallel, and thus the wave front is focused to a particular point. If the wave front arrives at an imaging system with energy vectors that point in different directions, each part of the wave front will be focused at a slightly different point on the sensor plane and result in a distorted image. The Hartmann test, which involves the insertion of a series of pinholes between the imaging system and the sensor plane, was developed to sample the wavefront at different locations and measure the distortion angles at different points in the wave front. An adaptive optic system, such as a deformable mirror, is then used to correct for these distortions and allow the planar wave front to focus at the point desired on the sensor plane, thereby correcting the distorted image. The apertures of a pinhole array limit the amount of light that reaches the sensor plane. By replacing the pinholes with a microlens array each bundle of rays is focused to brighten the image. Microlens arrays are making their way into newer imaging technologies, such as “light field” or “plenoptic” cameras. In these cameras, the microlens array is used to recover the ray information of the incoming light by using post processing techniques to focus on objects at different depths. The goal of this paper is to demonstrate the use of these plenoptic cameras to recover the distortions in wavefronts. Taking advantage of the microlens array within the plenoptic camera, CODE-V simulations show that its performance can provide more information than a Shack-Hartmann sensor. Using the microlens array to retrieve the ray information and then backstepping through the imaging system provides information about distortions in the arriving wavefront.
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Mohammed Eslami, Mohammed Eslami, Chensheng Wu, Chensheng Wu, John Rzasa, John Rzasa, Christopher C. Davis, Christopher C. Davis, } "Using a plenoptic camera to measure distortions in wavefronts affected by atmospheric turbulence", Proc. SPIE 8517, Laser Communication and Propagation through the Atmosphere and Oceans, 85170S (24 October 2012); doi: 10.1117/12.943038; https://doi.org/10.1117/12.943038
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