Kamran Binaee

Binocular eye tracking calibration during a virtual ball catching task using head mounted display

When tracking the eye movements of an active observer, the quality of the tracking data is continuously affected by physical shifts of the eye-tracker on an observers head. This is especially true for eye-trackers integrated within virtual-reality (VR) helmets. These configurations modify the weight and inertia distribution well beyond that of the eye-tracker alone. Despite the continuous nature of this degradation, it is common practice for calibration procedures to establish eye-to-screen mappings, fixed over the time-course of an experiment. Even with periodic recalibration, data quality can quickly suffer due to head motion. Here, we present a novel post-hoc calibration method that allows for continuous temporal interpolation between discrete calibration events. Analysis focuses on the comparison of fixed vs. continuous calibration schemes and their effects upon the quality of a binocular gaze data to virtual targets, especially with respect to depth. Calibration results were applied to binocular eye tracking data from a VR ball catching task and improved the tracking accuracy especially in the dynamic case.

Assessment of an augmented reality apparatus for the study of visually guided walking and obstacle crossing

To walk through the cluttered natural environment requires visually guided and anticipatory adjustments to gait in advance of upcoming obstacles. However, scientific investigation of visual contributions to obstacle crossing have historically been limited by the practical issues involved with the repeated presentation of multiple obstacles upon a ground plane. This study evaluates an approach in which the perception of a 3D obstacle is generated from 2D projection onto the ground plane with perspective correction based on the subject’s motion-tracked head position. The perception of depth is further reinforced with the use of stereoscopic goggles. To evaluate the validity of this approach, behavior was compared between approaches to two types of obstacles in a blocked design: physical obstacles, and the augmented reality (AR) obstacles projected upon the ground plane. In addition, obstacle height, defined in units of leg length (LL), was varied on each trial (0.15, 0.25, 0.35 LL). Approaches to ended with collision on 0.8% of trials with physical obstacles per subject, and on 1.4% trials with AR obstacles. Collisions were signaled by auditory feedback. Linear changes in the height of both AR and physical obstacles produced linear changes in maximum step height, preserving a constant clearance magnitude across changes in obstacle height. However, for AR obstacles, approach speed was slower, the crossing step peaked higher above the obstacle, and there was greater clearance between the lead toe and the obstacle. These results suggest that subjects were more cautious when approaching and stepping over AR obstacles.

Novel apparatus for investigation of eye movements when walking in the presence of 3D projected obstacles

The human gait cycle is incredibly efficient and stable largely because of the use of advance visual information to make intelligent selections of heading direction, foot placement, gait dynamics, and posture when faced with terrain complexity [Patla and Vickers 1997; Patla and Vickers 2003; Matthis and Fajen 2013; Matthis and Hayhoe 2015]. This is behaviorally demonstrated by a coupling between saccades and foot placement.