Evaluating perception in driving simulation experiments.

The use of driving simulation for vehicle design and driver perception studies is expanding rapidly. This is largely because simulation saves engineering time and costs, and can be used for studies of road and traffic safety. How applicable driving simulation is to the real world is unclear however, because analyses of perceptual criteria carried out in driving simulation experiments are controversial. On the one hand, recent data suggest that, in driving simulators with a large field of view, longitudinal speed can be estimated correctly from visual information. On the other hand, recent psychophysical studies have revealed an unexpectedly important contribution of vestibular cues in distance perception and steering, prompting a re-evaluation of the role of visuo-vestibular interaction in driving simulation studies.

Absolute distance perception during in-depth head movement: calibrating optic flow with extra-retinal information.

We investigated the ability of monocular human observer to scale absolute distance during sagittal head motion in the presence of pure optic flow information. Subjects were presented at eye-level computer-generated spheres (covered with randomly distributed dots) placed at several distances. We compared the condition of self-motion (SM) versus object-motion (OM) using equivalent optic flow field. When the amplitude of head movement was relatively constant, subjects estimated absolute distance rather accurately in both the SM and OM conditions. However, when the amplitude changed on a trial-to-trial basis, subjects' performance deteriorated only in the OM condition. We found that distance judgment in OM condition correlated strongly with optic flow divergence, and that non-visual cues served as important factors for scaling distances in SM condition. Absolute distance also seemed to be better scaled with sagittal head movement when compared with lateral head translation.

Oculo-motor stabilization reflexes: integration of inertial and visual information.

STABILIZATION OF GAZE IS A FUNDAMENTAL REQUIREMENT OF AN ACTIVE VISUAL SYSTEM FOR AT LEAST TWO REASONS: (i) to increase the robustness of dynamic visual measures during observer's motion; (ii) to provide a reference with respect to the environment ([Ballard and Brown, 1992]). The aim of this paper is to address the former issue by investigating the role of integration of visuo-inertial information in gaze stabilization. The rationale comes from observations of how the stabilization problem is solved in biological systems and experimental results based on an artificial visual system equipped with space-variant visual sensors and an inertial sensor are presented. In particular the following issues are discussed: (i) the relations between eye-head geometry, fixation distance and stabilization performance; (ii) the computational requirements of the visuo-inertial stabilization approach compared to a visual stabilization approach; (iii) the evaluation of performance of the visuo-inertial strategy in a real-time monocular stabilization task. Experiments are performed to quantitatively describe the performance of the system with respect to different choices of the principal parameters. The results show that the integrated approach is indeed valuable: it makes use of visual computational resources more efficiently, extends the range of motions or external disturbances the system can effectively deal with, and reduces system complexity.