Registration errors in augmented reality systems

Abstract

Augmented reality (AR) systems combine three-dimensional computer-generated imagery with the view of the real environment in order to make unseen objects visible or to present additional information. A critical problem is that the computer-generated objects do not currently remain correctly registered with the real environment---objects aligned from one viewpoint appear misaligned from another and appear to swim about as the viewer moves. This registration error is caused by a number of factors, such as system delay, optical distortion, and tracker measurement error, and is difficult to correct with existing technology. This dissertation presents a registration error model for AR systems and uses it to gain insight into the nature and severity of the registration error caused by the various error sources. My thesis is that a mathematical error model enables the system architect to determine . which error sources are the most significant, . the sensitivity of the net registration error to each error, . the nature of the distortions caused by each type of error, . the level of registration accuracy one can expect, and also provides insights on how best to calibrate the system. Analysis of a surgery planning application yielded the following main results: . Even for moderate head velocities, system delay causes more registration error than all other sources combined; . Using the eye's center of rotation as the eyepoint in the computer graphics model reduces the error due to eye rotation to zero for points along the line of gaze. This should obviate the need for eye tracking; . Tracker error is a significant problem both in head tracking and in system calibration; . The World coordinate system should be omitted when possible; . Optical distortion is a significant err...