Light Ray Field Research Articles

Consistency analysis of focal stack-based light field reconstruction

Light field camera with a microlens array can realize spatio-angular joint sampling of light ray field at the cost of a trade-off between spatial and angular resolutions. Alternatively, focal stack-based light field reconstruction can computationally retrieve full-pixel-resolution light fields in object space by virtue of the transport-of-intensity property in an image sequence recorded at different focal depths in image space. However, traditional camera imaging generally involves a nonlinear mapping between object and image spaces. The inconsistency of image-space recording and object-space reconstruction will reduce the accuracy of reconstructed light fields. In this work, we focus on analyzing and addressing the problem caused by the object-image space inconsistency for high-resolution, high-accuracy focal stack-based light field reconstruction. With a pre-calibrated light field camera as a reference, light field reconstructions in object and image spaces are experimentally compared and discussed from different aspects, such as digital refocusing, viewpoint switching, angular resolution, and depth range and sampling rate. All experimental results demonstrate that the light field reconstruction accuracy can be significantly improved when satisfying the object-image space consistency, which can serve as a mechanism for the realization and application of high-quality computational light field imaging and measurement in the situation of nonlinear recording and reconstruction.

Dual layered display that presents auto‐stereoscopic 3D images to multiple viewers in arbitrary positions

AbstractDual layered display or also called tensor display that consists of two panels in a stack can present full‐parallax 3D images with high resolution and continuous motion parallax by reconstructing corresponding light ray field within a viewing angle. The depth range where the 3D images can be displayed with reasonable resolution, however, is limited around the panel stack. In this paper, we propose a dual layered display that can present stereoscopic images to multiple viewers located at arbitrary positions in observer space with high resolution and large depth range. Combined with the viewer tracking system, the proposed method provides a practical way to realize high‐resolution large‐depth auto‐stereoscopic 3D display for multiple observers without restriction on the observer position and the head orientation.

Light ray field capture using focal plane sweeping and its optical reconstruction using 3D displays.

We propose a method to capture light ray field of three-dimensional scene using focal plane sweeping. Multiple images are captured using a usual camera at different focal distances, spanning the three-dimensional scene. The captured images are then back-projected to four-dimensional spatio-angular space to obtain the light ray field. The obtained light ray field can be visualized either using digital processing or optical reconstruction using various three-dimensional display techniques including integral imaging, layered display, and holography.

Analysis of image distortion based on light ray field by multi-view and horizontal parallax only integral imaging display

Three-dimensional image distortion caused by mismatch between autostereoscopic displays and contents is analyzed. For a given three-dimensional object scene, the original light ray field in the contents and deformed one by the autostereoscopic displays are calculated. From the deformation of the light ray field, the distortion of the resultant three-dimensional image is finally deduced. The light ray field approach enables generalized distortion analysis across different autostereoscopic display techniques. The analysis result is verified experimentally when multi-view contents are applied to a multi-view display of non-matching parameters and a horizontal parallax only integral imaging display.

Generalized laws of refraction that can lead to wave-optically forbidden light-ray fields

The recent demonstration of a metamaterial phase hologram so thin that it can be classified as an interface in the effective-medium approximation [Science 334, 333 (2011)] has dramatically increased interest in generalized laws of refraction. Based on the fact that scalar wave optics allows only certain light-ray fields, we divide generalized laws of refraction into two categories. When applied to a planar cross section through any allowed light-ray field, the laws in the first category always result in a cross section through an allowed light-ray field again, whereas the laws in the second category can result in a cross section through a forbidden light-ray field.

TIM, a ray-tracing program for METATOY research and its dissemination

TIM (The Interactive METATOY) is a ray-tracing program specifically tailored towards our research in METATOYs, which are optical components that appear to be able to create wave-optically forbidden light-ray fields. For this reason, TIM possesses features not found in other ray-tracing programs. TIM can either be used interactively or by modifying the openly available source code; in both cases, it can easily be run as an applet embedded in a web page. Here we describe the basic structure of TIMʼs source code and how to extend it, and we give examples of how we have used TIM in our own research. Program summary Program title: TIM Catalogue identifier: AEKY_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEKY_v1_0.html Program obtainable from: CPC Program Library, Queenʼs University, Belfast, N. Ireland Licensing provisions: GNU General Public License No. of lines in distributed program, including test data, etc.: 124 478 No. of bytes in distributed program, including test data, etc.: 4 120 052 Distribution format: tar.gz Programming language: Java Computer: Any computer capable of running the Java Virtual Machine (JVM) 1.6 Operating system: Any; developed under Mac OS X Version 10.6 RAM: Typically 145 MB (interactive version running under Mac OS X Version 10.6) Classification: 14, 18 External routines: JAMA [1] (source code included) Nature of problem: Visualisation of scenes that include scene objects that create wave-optically forbidden light-ray fields. Solution method: Ray tracing. Unusual features: Specifically designed to visualise wave-optically forbidden light-ray fields; can visualise ray trajectories; can visualise geometric optic transformations; can create anaglyphs (for viewing with coloured “3D glasses”) and random-dot autostereograms of the scene; integrable into web pages. Running time: Problem-dependent; typically seconds for a simple scene.

Geometric limits to geometric optical imaging with infinite, planar, non-absorbing sheets

Wave optics can limit the ways in which optical components can change light-ray fields. Optical components called METATOYs trade in the continuity of the phase fronts and the precision to which they change light-ray fields in return for additional possibilities when changing light-ray fields. Now only geometry limits the possible mappings between the positions of an object and its geometric image. Here, I study such limitations for the case of an infinite, planar, non-absorbing sheet that images the entire three-dimensional space. The most general case of such a sheet is equivalent to a thin lens with different object- and image-sided focal lengths. Special cases include ordinary thin lenses, confocal lenslet arrays, and negative refration with n 2 = - n 1 .