Light-field Display

Human binocular vision and acuity and the accompanying 3D retinal processing of the human eye and brain are specifically designed to promote situational awareness and understanding in the natural 3D world.  The ability to resolve depth within a scene, whether natural or artificial, improves our spatial understanding of the environment and as a result reduces the cognitive load accompanying the analysis and collaboration on complex tasks. 

In recent years, studies exemplifying the benefits of 3D visualizations for mission/medical planning, training, and rehearsal have been performed:

· Investigating Geospatial Holograms for Special Weapons and Tactics Teams by Sven Fuhrmann,et al., which found mission planning with the 3D light-field visuals increased mission performance by 30%.

· Medical Holography for Basic Anatomy Training by Matthew Hackett which demonstrated a significant increase in memory retention in medical students trained using 3D viusals of human anatomy over traditional textbooks.

In addition, collaboration between multiple viewers is a common occurrence.  New visualization technologies will need to support multiple viewers without the use of stereoscopic glasses or eye or head tracking peripherals.  In some existing visualization environments, high resolution 2D screens are used with special glasses or lenticular lenses to display 3D imagery with software algorithms simulating perspective.  As documented by Air Force Research Laboratory (AFRL), many of these systems that try to provide 3D visualizations through eye-tracked or stereo projections can induce eye fatigue and nausea in the viewer due to conflicting depth cues.  In addition, these displays cannot be used for natural 3D collaboration since the visualizations offer only a single point of view (POV) or perspective.  These factors greatly limit the effectiveness of these eye-tracked or stereoscopic displays for viewing complex 3D data especially in a collaborative environment.

The FoVI 3D LFD solution will play a key role in the near future AOC by providing a solution for the way users visualize 3D information.  These advancements will reduce cognitive loads facilitating improved and faster military decisions.

Complex optic assembly visualized on the Gen1 Light-field Display.

Streaming 3D point cloud from Velodyne Sensor to Light-field Display:

Physics demonstration. Stacking cubes on the Gen1 light-field display using the Leonar3Do cursor calibrated to the display.

 

Light-field Display Metrology

In recent years, a number of technology companies have produced auto-stereoscopic 3D volumetric and light-field displays and prototypes of varying capabilities.  Qualifying their performance has been a subjective exercise as there is no common base for the determination of field of light displays (FoLD) metrology.  Similar metrology and standards definition was paramount to the successful commercialization and adoption of 2D displays.  Terms and concepts such as contrast ratio and pixels-per-inch are now common expressions to advertise and define 2D display capability.

Many of the 2D display metrics such as contrast ratio can be applied directly to the metrology of light-field displays.  However, as the FoLD produces a 3D projection within a prescribed visualization volume, the determination of contrast ratio for a light-field display will require a novel approach from the manner used to measure the contrast ratio of a 2D display.   Existing 2D image and display terms such as vignetting may require extra qualification when applied to the description of the reduction of brightness by position within a 3D volume.

In addition, new metrology concepts will need to be explored to describe the FoLD contrast ratio as a function of location within the visualization volume or as a function of viewing perspective if the FoLD contrast is not uniform throughout the projection volume.  Novel terms, such as perspective depth, may need to be defined to help describe FoLD attributes such as contrast when viewed from a particular perspective and/or depth within the visualization volume.  This will help create a common reference for understanding and describing light-field display capabilities.   

The effect of light-field attributes such as contrast on the human visualization system will also need to be explored and evaluated.  For example, small changes in contrast greatly affect the human perception of depth in the natural world.  The ability for the light-field display to project discernable depth separation along or between surfaces at different depths is a key factor in human spatial acuity and can be measured to derive a depth-contrast sensitivity metric for the FoLD.

It is also important that the terminology and procedures used to describe FoLD metrology be agnostic to the applied FoLD technology so that display capabilities can be fairly compared during the evolution and eventual productization of light-field displays.

 

 

FoVI 3D's FoLD metrology solution will play a key role in evaluating and qualifying the performance of 3D light-field displays by defining and automating the FoLD metrology process.  The intent of this program is to develop practical, affordable, and repeatable evaluation procedures and design a suite of light-field metrology applications that will qualify any 3D light-field display and produce results that can be used to evaluate FoLD metrology regardless of the FoLD implementation technology

 

Multiview Rendering

Hogel rendering is the process of rendering a synthetic radiance image/dataset for a light-field display.   A hogel is similar to a micro image in a radiance image as captured by a plenoptic camera.  The main distinction (besides being synthetically rendered) is that the hogel can represent light-rays on either side of the image plane.    This ability allows for projected 3D light-field content to be seen on either side of the light-field display image plane, effectively doubling the projection depth.

Hogel rendering requires a 3D model and a mathematical description of a light-field display image plane; in particular the exact locations of the optical axis of each micro-lens within the projection system.    A hogel is rendered at the center of each micro-lens in model space.   There are a couple of algorithms for rendering hogels for polygonal models including “orthographic slice and dice” and the fast double-frustum renderer as described in the paper “Fast Computer Graphics Rendering for Full Parallax Spatial Displays”.

Example of dynamic/live light-field rendering from an extremely large model at different resolutions

Example, hogel rendering for a static display

Static Hogel Rendering on Raspberry Pi2 Model b