<title>Study of motion parallax in depth perception with a helmet-mounted display system used in teleoperation</title>

Abstract

The objective of this study is to compare human performance in executing tasks with a helmet-mounted display interface using different visual cues of depth perception.The study involves two experiments, the first, with direct viewing, the second, with a helmet-mounted display (HMD). These experiments are designed to assess the subject's stereoacuity in an alignment task involving two rods, one mobile, the other fixed. In both experiments, the subject has no time constraints and simply has to perform the task as well as possible. The dependent variable is the depth positioning error. Ten subjects with a stereoacuity of 20 arc-seconds or less and 20/20 visual acuity (Snellen test) corrected or not took part in this study. In all experiments, the subject was exposed to four viewing conditions in direct view or HMD: mono-stationary, stereo-stationary, mono with motion parallax and stereo with motion parallax. The independent variables are the presence of stereo (with vs. without), the presence of motion parallax (with vs. without) and the session (session 1 or session 2). ANOVA 2 X 2 X 2 statistical processing is used.This study is part of an attempt to develop a teleoperation system for power distribution line maintenance work [1 ,2]. Two control configurations are considered and studied, raised or direct viewing in which the operator is positioned in a control cabin supported by an aerial platform and thus has a direct view of the task to be done, and a ground-level teleoperation technique in which the operator is positioned in a remote-control cabin and receives information about the task from a display interface.A first prototype of the ground-level teleoperation system has been developed in an aim to study human performance in using such a system. The prototype comprises a stereoscopic display interface. The stereoscopic video camera is located at the operator's eye level in direct viewing. The results obtained with the prototype revealed that it is in fact possible to perform typical lineman tasks with the ground-level teleoperation technique and that the performance of linemen with this technique even at this early stage is already half way toward reaching the performance obtained with the direct-viewing technique. Details about these experiments and the results are presented in references [1] and [2].In teleoperation, the operator's performance and degree of work safety are strongly dependent on the quality of the visual, audio and kinesthetic information received [3]. In direct vision, the operator scales depth on the basis of stereopsis and motion parallax and also of monocular cues such as interposition, shadow effects, linear perspective, gradient of textures and relative sizes. In the case of the display interface of a ground-level cabin, the view (from the point of view of acuity and stereoacuity) must be as close as possible to the direct view of the work area. O-8194-1954-O/95/$6.OO SPIE Vol. 2590 / 151 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/21/2016 Terms of Use: http://spie...

The Effects of Scene Complexity, Stereovision, and Motion Parallax on Size Constancy in a Virtual Environment

“…Peak scene displacement was 1 ft and peak velocity was 4 ft/sec. These parameter values were chosen to conform to natural human lateral movement in order to facilitate comparisons with active motion parallax ( [2], [3]). …”

“…The experiments in [2] was to judge visual objects' size which varied fourfold range among trials, the authors concluded that absolute motion parallax only weakly determined the visual scale of nearby objects. Distance perception was studied in [3], for users' performance in teleoperation. The paper suggested that stereoscopy and motion parallax were of equal significance in distance judgment, and users' performance varied largely between HMD and projected screen settings.…”

On the Determinants of Size-Constancy in a Virtual Environment

“…Experiments by Beall et al [2] where subjects judged the size of objects, whose visual dimension varied fourfold, concluded that absolute motion parallax only weakly determined the visual scale of nearby objects. Rondot et al [3] studied distance perception during a tele-operation task. Their results suggested that stereoptical and motion parallax cues were of equal significance in distance judgment, and users' performances varied widely dependent on whether they used a head mounted display (HMD) or projection-based VE system.…”

“…Peak scene displacement was 1 ft each way and peak velocity was 4 ft/s. These parameter values were chosen to conform to natural human lateral movement in order to facilitate comparisons with active motion parallax [2,3].…”

“…22 in [17] where they plot their subjects' performance as the visual field-of-view was narrowed 2 Since motion parallax was not a significant factor in our population's results, we grouped our subjects' performance into categories: No-ENV:MONO, No-ENV:STEREO, ENV:MONO and ENV:STEREO and averaged their regression slope values within each category. thus reducing the visual cues available 3 . Similarly, one might expect the performance from our subject population to follow a similar course as the cues in the visual field are manipulated.…”