scholarly journals FAITH: Fast iterative half-plane focus of expansion estimation using optic flow

2021 ◽  
pp. 1-1
Author(s):  
Raoul Dinaux ◽  
Nikhil Wessendorp ◽  
Julien Dupeyroux ◽  
Guido De Croon
Keyword(s):  
Half Plane ◽  
Optic Flow ◽  
Focus Of Expansion

Short-Latency Vergence Eye Movements Induced by Radial Optic Flow in Humans: Dependence on Ambient Vergence Level

1999 ◽  
Vol 81 (2) ◽  
pp. 945-949 ◽  
Author(s):  
D.-S. Yang ◽  
E. J. Fitzgibbon ◽  
F. A. Miles
Keyword(s):  
Eye Movements ◽  
Optic Flow ◽  
Radial Flow ◽  
Human Subjects ◽  
Short Latency ◽  
Viewing Distance ◽  
Focus Of Expansion ◽  
Random Dot Patterns

Yang, D.-S., E. J. Fitzgibbon, and F. A. Miles. Short-latency vergence eye movements induced by radial optic flow in humans: dependence on ambient vergence level. J. Neurophysiol. 81: 945–949, 1999. Radial patterns of optic flow, such as those experienced by moving observers who look in the direction of heading, evoke vergence eye movements at short latency. We have investigated the dependence of these responses on the ambient vergence level. Human subjects faced a large tangent screen onto which two identical random-dot patterns were back-projected. A system of crossed polarizers ensured that each eye saw only one of the patterns, with mirror galvanometers to control the horizontal positions of the images and hence the vergence angle between the two eyes. After converging the subject's eyes at one of several distances ranging from 16.7 cm to infinity, both patterns were replaced with new ones (using a system of shutters and two additional projectors) so as to simulate the radial flow associated with a sudden 4% change in viewing distance with the focus of expansion/contraction imaged in or very near both foveas. Radial-flow steps induced transient vergence at latencies of 80–100 ms, expansions causing increases in convergence and contractions the converse. Based on the change in vergence 90–140 ms after the onset of the steps, responses were proportional to the preexisting vergence angle (and hence would be expected to be inversely proportional to viewing distance under normal conditions). We suggest that this property assists the observer who wants to fixate ahead while passing through a visually cluttered area (e.g., a forest) and so wants to avoid making vergence responses to the optic flow created by the nearby objects in the periphery.

Evidence for the use of rotational optic flow cues for locomotor steering in healthy older adults

2011 ◽  
Vol 106 (3) ◽  
pp. 1089-1096 ◽  
Author(s):  
Jessica R. Berard ◽  
Joyce Fung ◽  
Anouk Lamontagne
Keyword(s):  
Older Adults ◽  
Virtual Environment ◽  
Optic Flow ◽  
Visual Motion ◽  
Healthy Older Adults ◽  
Head Mounted Display ◽  
Focus Of Expansion ◽  
Healthy Young People ◽  
The Right ◽  
Head Rotations

Optic flow is a powerful visual cue for the control of locomotion. Considerable research has focused on how healthy young people use and perceive optic flow. However, little is known on how older adults use this type of visual motion to control walking. The purpose of this study is to investigate the ability of young and older adults to adjust their physical walking trajectory in response to a rotation of the optic flow presented in a virtual environment. Ten healthy young adults (mean age 23.49 ± 4.72 yr) and 10 healthy older adults (mean age 76.22 ± 3.11 yr) participated in the study. Subjects were instructed to walk straight in a virtual environment viewed within a head-mounted display unit as they walked overground for 5 m, while the focus of expansion was gradually rotated to the left or the right by 40°. All subjects responded with a similar strategy by rotating their head and body in the direction away from the orientation of the perturbation. The younger subjects achieved almost complete corrections and had very small net heading errors. In contrast, the older adults had delayed and smaller reorientations, particularly in the head, thus showing significantly larger heading errors compared with younger subjects. We conclude that older adults retain the ability to use optic flow to control their walking trajectory, although smaller, delayed head rotations and larger heading errors may indicate an age-dependent effect on sensorimotor coordination.

scholarly journals Differential processing of the direction and focus of expansion of optic flow stimuli in areas MST and V3A of the human visual cortex

2017 ◽  
Vol 117 (6) ◽  
pp. 2209-2217 ◽  
Author(s):  
Samantha L. Strong ◽  
Edward H. Silson ◽  
André D. Gouws ◽  
Antony B. Morland ◽  
Declan J. McKeefry
Keyword(s):  
Human Brain ◽  
Neural Activity ◽  
Optic Flow ◽  
Radial Direction ◽  
Judgment Task ◽  
Radial Motion ◽  
Motion Direction ◽  
Biologically Relevant ◽  
Direction Discrimination ◽  
Focus Of Expansion

Human neuropsychological and neuroimaging studies have raised the possibility that different attributes of optic flow stimuli, namely radial direction and the position of the focus of expansion (FOE), are processed within separate cortical areas. In the human brain, visual areas V5/MT+ and V3A have been proposed as integral to the analysis of these different attributes of optic flow stimuli. To establish direct causal relationships between neural activity in human (h)V5/MT+ and V3A and the perception of radial motion direction and FOE position, we used transcranial magnetic stimulation (TMS) to disrupt cortical activity in these areas while participants performed behavioral tasks dependent on these different aspects of optic flow stimuli. The cortical regions of interest were identified in seven human participants using standard functional MRI retinotopic mapping techniques and functional localizers. TMS to area V3A was found to disrupt FOE positional judgments but not radial direction discrimination, whereas the application of TMS to an anterior subdivision of hV5/MT+, MST/TO-2 produced the reverse effects, disrupting radial direction discrimination but eliciting no effect on the FOE positional judgment task. This double dissociation demonstrates that FOE position and radial direction of optic flow stimuli are signaled independently by neural activity in areas hV5/MT+ and V3A. NEW & NOTEWORTHY Optic flow constitutes a biologically relevant visual cue as we move through any environment. With the use of neuroimaging and brain-stimulation techniques, this study demonstrates that separate human brain areas are involved in the analysis of the direction of radial motion and the focus of expansion in optic flow. This dissociation reveals the existence of separate processing pathways for the analysis of different attributes of optic flow that are important for the guidance of self-locomotion and object avoidance.

scholarly journals Look where you go: characterizing eye movements toward optic flow

2020 ◽  
Author(s):  
Hiu Mei Chow ◽  
Jonas Knöll ◽  
Matthew Madsen ◽  
Miriam Spering
Keyword(s):  
Eye Movements ◽  
Optic Flow ◽  
Visual Motion ◽  
Signal Strength ◽  
Motion Processing ◽  
Task Instructions ◽  
Motion Signal ◽  
Visual Motion Processing ◽  
Focus Of Expansion ◽  
Smooth Tracking

AbstractWhen we move through our environment, objects in the visual scene create optic flow patterns on the retina. Even though optic flow is ubiquitous in everyday life, it is not well understood how our eyes naturally respond to it. In small groups of human and non-human primates, optic flow triggers intuitive, uninstructed eye movements to the pattern’s focus of expansion (Knöll, Pillow & Huk, 2018). Here we investigate whether such intuitive oculomotor responses to optic flow are generalizable to a larger group of human observers, and how eye movements are affected by motion signal strength and task instructions. Observers (n = 43) viewed expanding or contracting optic flow constructed by a cloud of moving dots radiating from or converging toward a focus of expansion that could randomly shift. Results show that 84% of observers tracked the focus of expansion with their eyes without being explicitly instructed to track. Intuitive tracking was tuned to motion signal strength: saccades landed closer to the focus of expansion and smooth tracking was more accurate when dot contrast, motion coherence, and translational speed were high. Under explicit tracking instruction, the eyes aligned with the focus of expansion more closely than without instruction. Our results highlight the sensitivity of intuitive eye movements as indicators of visual motion processing in dynamic contexts.

Artificial Optic Flow Guides Visual Attention in a Driving Scene

2019 ◽  
Vol 62 (4) ◽  
pp. 578-588 ◽  
Author(s):  
Yoko Higuchi ◽  
Satoshi Inoue ◽  
Hiroto Hamada ◽  
Takatsune Kumada
Keyword(s):  
Visual Attention ◽  
Traffic Safety ◽  
Optic Flow ◽  
Visual Information ◽  
Past Research ◽  
Traffic Situation ◽  
Significant Information ◽  
Safe Driving ◽  
Focus Of Expansion ◽  
Dot Motion

Objective The objective of this study was to investigate whether an artificial optic flow created by dot motion guides attention in a driving scene. Background To achieve safe driving, it is essential to understand the characteristics of human visual information processing as well as to provide appropriate support for drivers. Past research has demonstrated that expanding optic flow guides visual attention to the focus of expansion. Optic flow is an attractive candidate for use as a cue to direct drivers’ attention toward the significant information. The question addressed concerns whether an artificial optic flow can successfully guide attention even in a traffic situation involving the optic flow that naturally occurs while driving. Method We developed a visual search paradigm embedded in a video of a driving scene. Participants first observed an optic flow motion pattern superimposed on the video for brief period; next, when the optic flow and video ceased, they searched a static display for a target among multiple distractors. Results The target detection was faster when a target’s locus coincided with the implied focus of expansion from the preceding optic flow (vs. other loci). Conclusion The artificial optic flow guides attention and facilitates searching objects at the focus of expansion even when the optic flow was superimposed on a driving scene. Application Optic flow can be an effective cue for guiding drivers’ attention in a traffic situation. This finding contributes to the understanding of visual attention in moving space and helps develop technology for traffic safety.

Visually Perceived Eye Level and Horizontal Midline of the Body Trunk Influenced by Optic Flow

Perception ◽  
10.1068/p5416 ◽  
2005 ◽  
Vol 34 (9) ◽  
pp. 1045-1060 ◽  
Author(s):  
Jun Wu ◽  
Zijiang J He ◽  
Teng Leng Ooi
Keyword(s):  
Virtual Reality ◽  
Flow Pattern ◽  
Optic Flow ◽  
The Body ◽  
Motion Information ◽  
Dynamic Motion ◽  
Focus Of Expansion ◽  
Angular Declination ◽  
Flow Information ◽  
Optic Flow Information

The eye level and the horizontal midline of the body trunk can serve, respectively as references for judging the vertical and horizontal egocentric directions. We investigated whether the optic-flow pattern, which is the dynamic motion information generated when one moves in the visual world, can be used by the visual system to determine and calibrate these two references. Using a virtual-reality setup to generate the optic-flow pattern, we showed that judged elevation of the eye level and the azimuth of the horizontal midline of the body trunk are biased toward the positional placement of the focus of expansion (FOE) of the optic-flow pattern. Furthermore, for the vertical reference, prolonged viewing of an optic-flow pattern with lowered FOE not only causes a lowered judged eye level after removal of the optic-flow pattern, but also an overestimation of distance in the dark. This is equivalent to a reduction in the judged angular declination of the object after adaptation, indicating that the optic-flow information also plays a role in calibrating the extraretinal signals used to establish the vertical reference.

Approximate Solution Of A Singular Integral Equation With A Multiplicative Cauchy Kernel In The Half-Plane

2008 ◽  
Vol 8 (2) ◽  
pp. 143-154 ◽  
Author(s):  
P. KARCZMAREK
Keyword(s):  
Integral Equation ◽  
Approximate Solution ◽  
Singular Integral Equation ◽  
Half Plane ◽  
Singular Integral ◽  
Trigonometric Polynomials ◽  
Cauchy Kernel

AbstractIn this paper, Jacobi and trigonometric polynomials are used to con-struct the approximate solution of a singular integral equation with multiplicative Cauchy kernel in the half-plane.

Rayleigh Wave in a Rotating Magneto-Thermo-Elastic Half-Plane

2012 ◽  
Vol 42 (4) ◽  
Author(s):  
Baljeet Singh ◽  
Sangeeta Kumari ◽  
Jagdish Singh
Keyword(s):  
Rayleigh Wave ◽  
Half Plane
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