Implementation and Evaluation of a 50 kHz, 28µs Motion-to-Pose Latency Head Tracking Instrument.

This paper presents the implementation and evaluation of a 50,000-pose-sample-per-second, 6-degree-of-freedom optical head tracking instrument with motion-to-pose latency of 28µs and dynamic precision of 1-2 arcminutes. The instrument uses high-intensity infrared emitters and two duo-lateral photodiode-based optical sensors to triangulate pose. This instrument serves two purposes: it is the first step towards the requisite head tracking component in sub- 100µs motion-to-photon latency optical see-through augmented reality (OST AR) head-mounted display (HMD) systems; and it enables new avenues of research into human visual perception - including measuring the thresholds for perceptible real-virtual displacement during head rotation and other human research requiring high-sample-rate motion tracking. The instrument's tracking volume is limited to about 120×120×250 but allows for the full range of natural head rotation and is sufficient for research involving seated users. We discuss how the instrument's tracking volume is scalable in multiple ways and some of the trade-offs involved therein. Finally, we introduce a novel laser-pointer-based measurement technique for assessing the instrument's tracking latency and repeatability. We show that the instrument's motion-to-pose latency is 28µs and that it is repeatable within 1-2 arcminutes at mean rotational velocities (yaw) in excess of 500°/sec.

An Extended Depth-at-Field Volumetric Near-Eye Augmented Reality Display.

We introduce an optical design and a rendering pipeline for a full-color volumetric near-eye display which simultaneously presents imagery with near-accurate per-pixel focus across an extended volume ranging from 15cm (6.7 diopters) to 4M (0.25 diopters), allowing the viewer to accommodate freely across this entire depth range. This is achieved using a focus-tunable lens that continuously sweeps a sequence of 280 synchronized binary images from a high-speed, Digital Micromirror Device (DMD) projector and a high-speed, high dynamic range (HDR) light source that illuminates the DMD images with a distinct color and brightness at each binary frame. Our rendering pipeline converts 3-D scene information into a 2-D surface of color voxels, which are decomposed into 280 binary images in a voxel-oriented manner, such that 280 distinct depth positions for full-color voxels can be displayed.

From Motion to Photons in 80 Microseconds: Towards Minimal Latency for Virtual and Augmented Reality.

We describe an augmented reality, optical see-through display based on a DMD chip with an extremely fast (16 kHz) binary update rate. We combine the techniques of post-rendering 2-D offsets and just-in-time tracking updates with a novel modulation technique for turning binary pixels into perceived gray scale. These processing elements, implemented in an FPGA, are physically mounted along with the optical display elements in a head tracked rig through which users view synthetic imagery superimposed on their real environment. The combination of mechanical tracking at near-zero latency with reconfigurable display processing has given us a measured average of 80 µs of end-to-end latency (from head motion to change in photons from the display) and also a versatile test platform for extremely-low-latency display systems. We have used it to examine the trade-offs between image quality and cost (i.e. power and logical complexity) and have found that quality can be maintained with a fairly simple display modulation scheme.