Towards a unified treatment of 3D display using partially coherent light

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 111-120).This thesis develops a novel method of decomposing a 3D phase space description of light into multiple partially coherent modes, and applies this decomposition to the creation of a more flexible 3D display format. Any type of light, whether it is completely coherent, partially coherent or incoherent, can be modeled either as a sum of coherent waves or as rays. A set of functions, known as phase space functions, provide an intuitive model for these waves or rays as they pass through a 3D volume to a display viewer's eyes. First, this thesis uses phase space functions to mathematically demonstrate the limitations of two popular 3D display setups: parallax barriers and coherent holograms. Second, this thesis develops a 3D image design algorithm based in phase space. The "mode-selection" algorithm can find an optimal holographic display setup to create any desired 3D image. It is based on an iterative algebraic-rank restriction process, and can be extended to model light with an arbitrary degree of partial coherence. Third, insights gained from partially coherent phase space representations lead to the suggestion of a new form of 3D display, implemented with multiple time-sequential diffracting screens. The mode-selection algorithm determines an optimal set of diffracting screens to display within the flicker-fusion rate of a viewer's eye. It is demonstrated both through simulation and experiment that this time-sequential display offers improved performance over a fixed holographic display, creating 3D images with increased intensity variation along depth. Finally, this thesis investigates the tradeoffs involved with multiplexing a holographic display over time with well-known strategies of multiplexing over space, illumination angle and wavelength. The examination of multiplexing tradeoffs is extended into the incoherent realm, where comparisons to ray-based 3D displays can hopefully offer a more unified summary of the limitations of controlling light within a volume.by Roarke Horstmeyer.S.M

Highlighted depth-of-field photography: Shining light on focus

We present a photographic method to enhance intensity differences between objects at varying distances from the focal plane. By combining a unique capture procedure with simple image processing techniques, the detected brightness of an object is decreased proportional to its degree of defocus. A camera-projector system casts distinct grid patterns onto a scene to generate a spatial distribution of point reflections. These point reflections relay a relative measure of defocus that is utilized in postprocessing to generate a highlighted DOF photograph. Trade-offs between three different projectorprocessing pairs are analyzed, and a model is developed to help describe a new intensity-dependent depth of field that is controlled by the pattern of illumination. Results are presented for a primary single snapshot design as well as a scanning method and a comparison method. As an application, automatic matting results are presented.Alfred P. Sloan Foundatio

Partially coherent ambiguity functions for depth-variant point spread function design

The ambiguity function (AF) provides a convenient way to model how a camera with a modified aperture responds to defocus. We use the AF to design an optimal aperture distribution, which creates a depth-variant point spread function (PSF) from a sparse set of desired intensity patterns at different focal depths. Prior knowledge of the coherence state of the light is used to constrain the optimization in the mutual intensity domain. We use an assumption of spatially coherent light to design a fixed-pattern aperture mask. The concept of a dynamic aperture mask that displays several aperture patterns during one image exposure is also suggested, which is modeled under an assumption of partially coherent light. Parallels are drawn between the optimal aperture functions for this dynamic mask and the eigenmodes of a coherent mode decomposition. We demonstrate how the space of design for a 3D intensity distribution of light using partially coherent assumptions is less constrained than under coherent light assumptions.United States. Air Force Office of Scientific Research (National Defense Science and Engineering Graduate (NDSEG) fellowship)United States. Defense Advanced Research Projects Agency (DARPA Young Faculty Award)Alfred P. Sloan Foundation (Research Fellowship

Computational Microscopy: Turning Megapixels into Gigapixels

The layout of a typical optical microscope has remained effectively unchanged over the past century. Besides the widespread adoption of digital focal plane arrays, relatively few innovations have helped improve standard imaging with bright-field microscopes. This thesis presents a new microscope imaging method, termed Fourier ptychography, which uses an LED to provide variable sample illumination and post-processing algorithms to recover useful sample information. Examples include increasing the resolution of megapixel-scale images to one gigapixel, measuring quantitative phase, achieving oil-immersion quality resolution without an immersion medium, and recovering complex three dimensional sample structure