Engineering data compendium. Human perception and performance. User's guide

The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use

Optical techniques for 3D surface reconstruction in computer-assisted laparoscopic surgery

One of the main challenges for computer-assisted surgery (CAS) is to determine the intra-opera- tive morphology and motion of soft-tissues. This information is prerequisite to the registration of multi-modal patient-specific data for enhancing the surgeon’s navigation capabilites by observ- ing beyond exposed tissue surfaces and for providing intelligent control of robotic-assisted in- struments. In minimally invasive surgery (MIS), optical techniques are an increasingly attractive approach for in vivo 3D reconstruction of the soft-tissue surface geometry. This paper reviews the state-of-the-art methods for optical intra-operative 3D reconstruction in laparoscopic surgery and discusses the technical challenges and future perspectives towards clinical translation. With the recent paradigm shift of surgical practice towards MIS and new developments in 3D opti- cal imaging, this is a timely discussion about technologies that could facilitate complex CAS procedures in dynamic and deformable anatomical regions

Advances in Stereo Vision

Stereopsis is a vision process whose geometrical foundation has been known for a long time, ever since the experiments by Wheatstone, in the 19th century. Nevertheless, its inner workings in biological organisms, as well as its emulation by computer systems, have proven elusive, and stereo vision remains a very active and challenging area of research nowadays. In this volume we have attempted to present a limited but relevant sample of the work being carried out in stereo vision, covering significant aspects both from the applied and from the theoretical standpoints

Coding of stereoscopic depth information in visual areas V3 and V3A

The process of stereoscopic depth perception is thought to begin with the analysis of absolute binocular disparity, the difference in position of corresponding features in the left and right eye images with respect to the points of fixation. Our sensitivity to depth, however, is greater when depth judgments are based on relative disparity, the difference between two absolute disparities, compared to when they are based on absolute disparity. Therefore, the visual system is thought to compute relative disparities for fine depth discrimination. Functional magnetic resonance imaging studies in humans and monkeys have suggested that visual areas V3 and V3A may be specialized for stereoscopic depth processing based on relative disparities. In this study, we measured absolute and relative disparity tuning of neurons in V3 and V3A of alert fixating monkeys and we compared their basic tuning properties with those published previously for other visual areas. We found that neurons in V3 and V3A predominantly encode absolute, not relative, disparities. We also found that basic parameters of disparity tuning in V3 and V3A are similar to those from other extrastriate visual areas. Finally, by comparing single-unit activity with multi-unit activity measured at the same recording site, we demonstrate that neurons with similar disparity selectivity are clustered in both V3 and V3A. We conclude that areas V3 and V3A are not particularly specialized for processing stereoscopic depth information compared to other early visual areas, at least with respect to the tuning properties that we have examined

Neurons in striate cortex limit the spatial and temporal resolution for detecting disparity modulation.

Stereopsis is the process of seeing depth constructed from binocular disparity. The human ability to perceive modulation of disparity over space (Tyler, 1974; Prince and Rogers, 1998; Banks et al., 2004a) and time (Norcia and Tyler, 1984) is surprisingly poor, compared with the ability to detect spatial and temporal modulation of luminance contrast. In order to examine the physiological basis of this poor spatial and temporal resolution of stereopsis, I quantified responses to disparity modulation in disparity selective V1 neurons from four awake behaving monkeys. To study the physiological basis of the spatial resolution of stereopsis, I characterized the three-dimensional structure of 55 V1 receptive fields (RF) using random dot stereograms in which disparity varied as a sinusoidal function of vertical position (“corrugations”). At low spatial frequencies, this produced a modulation in neuronal firing at the temporal frequency of the stimulus. As the spatial frequency increased, the modulation reduced. The mean response rate changed little, and was close to that produced by a uniform stimulus at the mean disparity of the corrugation. In 48/55 (91%) of the neurons, the modulation strength was a lowpass function of spatial frequency. These results suggest that the neurons have fronto-parallel planar receptive fields, no disparity-based surround inhibition and no selectivity for disparity gradients. This scheme predicts a relationship between RF size and the high frequency cutoff. Comparison with independent measurements of RF size was compatible with this. All of this behavior closely matches the binocular energy model, which functionally corresponds to cross-correlation: the disparity modulated activity of the binocular neuron measures the correlation between the filtered monocular images. To examine the physiological basis of the temporal resolution of stereopsis, I measured for 59 neurons the temporal frequency tuning with random dot stereograms in which disparity varied as a sinusoidal function of time. Temporal frequency tuning in response to disparity modulation was not correlated with temporal frequency tuning in response to contrast modulation, and had lower temporal frequency high cutoffs on average. The temporal frequency high cut for disparity modulation was negatively correlated with the response latency, the speed of the response onset and the temporal integration time (slope of the line relating response phase and temporal frequency). Binocular cross-correlation of the monocular images after bandpass filtering can explain all these results. Average peak temporal frequency in response to disparity modulation was 2Hz, similar to the values I found in four human observers (1.5-3Hz). The mean cutoff spatial frequency, 0.5 cpd, was similar to equivalent measures of decline in human psychophysical sensitivity for such depth corrugations as a function of frequency (Tyler, 1974; Prince and Rogers, 1998; Banks et al., 2004a). This suggests that the human temporal and spatial resolution for stereopsis is limited by selectivity of V1 neurons. For both, space and time, the lower resolution for disparity modulation than for contrast modulation can be explained by a single mechanism, binocular cross-correlation of the monocular images. The findings also represent a significant step towards understanding the process by which neurons solve the stereo correspondence problem (Julesz, 1971)

The composite illusion requires composite face stimuli to be biologically plausible

AbstractComposite stimuli are whole faces comprised of two halves taken from different individuals. When asked to decide if two identical top halves are the ‘same’, subjects are more accurate (or faster to respond) in misaligned trials, than in aligned trials. This performance advantage for misaligned trials is referred to as the composite face effect (CFE). The proposed explanation is that aligned features are automatically fused together and form a global identity that interferes with the recognition of smaller components (the composite face illusion, CFI). However, when composite faces are misaligned, it appears to be much easier to ignore the identity of the whole face and process individual features. Here we are interested in why misalignment impairs holistic face perception. In Experiment 1 we tested the difference between horizontal and vertical misalignment and found that holistic interference persists when the vertical distance between features is increased. Is this because vertical misalignment leaves features in the correct vertical arrangement, or because vertically stretched faces are biologically plausible? Experiment 2 tested the difference between these two accounts by measuring the CFE when the two halves of a composite face were separated in stereo-depth and demonstrates that vertical symmetry alone is not sufficient for holistic processing. However, when the faces were slanted through stereo-depth (to an equivalent extent), subjects continued to be inaccurate. Overall, these experiments provide strong evidence that the composite illusion depends on biological plausibility in that the faces must be globally coherent

First and Second Order Stereoscopic Processing of Fused and Diplopic Targets

Depth from stereopsis is due to the positional difference between the two eyes, which results in each eye receiving a different view of the world. Although progress has been made in understanding how the visual system processes stereoscopic stimuli, a number of questions remain. The goal of this work was to assess the relationship between the perceptual, the temporal and the 1st- /2nd- order dichotomies of stereopsis and in doing so, determine an appropriate method for measuring depth from large disparities. To this end, stereosensitivity and perceived depth were assessed using 1st- and 2nd- order stimuli over a range of test disparities and conditions. The main contributions of this research are as follows: 1) The sustained/transient dichotomy proposed by Edwards, Pope and Schor (2000) is best considered in terms of the spatial dichotomy proposed by Hess and Wilcox (1994). At large disparities it is not possible to categorize performance based on exposure duration alone; 2) There is not a simple correspondence between Ogle's (1952) patent / qualitative perceptual categories and the 1st- /2nd- order dichotomy proposed by Hess and Wilcox (1994); 3) Quantitative depth is provided by both 1st- and 2nd- order mechanisms in the fused range, but only the 2nd- order signal is used when stimuli are diplopic; 3) The quantitative depth provided by a 2nd- order stimulus scales with envelope size; and 4) The monoptic depth phenomenon may be related to depth from diplopic stimuli, but for conditions tested here when both monoptic depth and 2nd- order stereopsis are available, the latter is used to encode depth percepts. The results reported here expand on earlier work on 1st- and 2nd- order stereopsis and address the issues in the methodologies used to study depth from large disparities. These results are consistent with the widely accepted filter-rectify-filter model of 2nd- order processing, and 1st- and 2nd- order stimuli are likely encoded by disparity-sensitive neurons via a two-stream model (see Wilson, Ferrera, and Yo (1992); Zhou and Baker (1993))

Mechanisms for similarity matching in disparity measurement

Early neural mechanisms for the measurement of binocular disparity appear to operate in a manner consistent with cross-correlation-like processes. Consequently, cross-correlation, or cross-correlation-like procedures have been used in a range of models of disparity measurement. Using such procedures as the basis for disparity measurement creates a preference for correspondence solutions that maximize the similarity between local left and right eye image regions. Here, we examine how observers' perception of depth in an ambiguous stereogram is affected by manipulations of luminance and orientation-based image similarity. Results show a strong effect of coarse-scale luminance similarity manipulations, but a relatively weak effect of finer-scale manipulations of orientation similarity. This is in contrast to the measurements of depth obtained from a standard cross-correlation model. This model shows strong effects of orientation similarity manipulations and weaker effects of luminance similarity. In order to account for these discrepancies, the standard cross-correlation approach may be modified to include an initial spatial frequency filtering stage. The performance of this adjusted model most closely matches human psychophysical data when spatial frequency filtering favors coarser scales. This is consistent with the operation of disparity measurement processes where spatial frequency and disparity tuning are correlated, or where disparity measurement operates in a coarse-to-fine manner. © 2014 Goutcher and Hibbard