2008-2009 Triangle Computer Science Distinguished Lecturer Series
Presented by - The U.S. Army Research Office, Duke University, N.C. State University and University of North Carolina at Chapel Hill, Computer Science Departments, UNC
Professor, Computer Science and Electrical Engineering, Stanford University
Monday March 23, 2009, 4:00 pm 011 Sitterson Hall
Light field photography and microscopy
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.
Marc Levoy is a Professor of Computer Science and (jointly) Electrical Engineering at Stanford University. He received a Bachelor's and Master's in Architecture from Cornell University in 1976 and 1978, and a PhD in Computer Science from the University of North Carolina at Chapel Hill in 1989. In the 1970's Levoy worked on computer animation, developing an early computer-assisted cartoon animation system. This system was used by Hanna-Barbera Productions from 1983 until 1996 to produce The Flintstones, Scooby Doo, and other shows. In the 1980's Levoy worked on volume rendering, a family of techniques for displaying sampled three-dimensional functions, for example computed tomography (CT) or magnetic resonance (MR) data. In the 1990's he worked on technology and algorithms for digitizing three-dimensional objects. This led to the Digital Michelangelo Project, in which he and a team of researchers spent a year in Italy digitizing the statues of Michelangelo using laser scanners. His current interests include light field sensing and display, computational photography, and applications of computer graphics in microscopy and biology. Awards: Charles Goodwin Sands Medal for best undergraduate thesis (1976), National Science Foundation Presidential Young Investigator (1991), ACM SIGGRAPH Computer Graphics Achievement Award (1996), ACM Fellow (2007). Recent professional service: Papers Chair of SIGGRAPH 2007.
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