Most binocular vision models assume that the two eyes sum incompletely. However, some facilitatory cortical neurons fire for only one eye, but amplify their firing rates if both eyes are stimulated. ...These 'binocular gate' neurons closely resemble subthreshold multisensory neurons. Binocular amplification for binocular gate neurons follows a power law, with a compressive exponent. Unexpectedly, this rule also applies to facilitatory true binocular neurons; although driven by either eye, binocular neurons are well modeled as gated amplifiers of their strongest monocular response, if both eyes are stimulated. Psychophysical data follows the same power law as the neural data, with a similar exponent; binocular contrast sensitivity can be modeled as a gated amplification of the more sensitive eye. These results resemble gated amplification phenomena in multisensory integration, and other non-driving modulatory interactions that affect sensory processing. Models of incomplete summation seem unnecessary for V1 facilitatory neurons or contrast sensitivity. However, binocular combination of clearly visible monocular stimuli follows Schrödinger's nonlinear magnitude-weighted average. We find that putatively suppressive binocular neurons closely follow Schrödinger's equation. Similar suppressive multisensory neurons are well documented but seldom studied. Facilitatory binocular neurons and mildly suppressive binocular neurons are likely neural correlates of binocular sensitivity and binocular appearance respectively.
Objective: We provide a review and analysis of much of the published literature on visual perception issues that impact the design and use of head-mounted displays (HMDs). Background: Unlike the ...previous literature on HMDs, this review draws heavily from the basic vision literature in order to help provide insight for future design solutions for HMDs. Method: Included in this review are articles and books found cited in other works as well as articles and books obtained from an Internet search. Results: Issues discussed include the effect of brightness and contrast on depth of field, dark focus, dark ergence, and perceptual constancy; the effect of accommodation-vergence synergy on perceptual constancy, eyestrain, and discomfort; the relationship of field of view to the functioning of different visual pathways and the types of visual motor tasks mediated by them; the relationship of binocular input to visual suppression; and the importance of head movements, head tracking, and display update lag. Conclusion: This paper offers a set of recommendations for the design and use of HMDs. Application: Consideration of the basic vision literature will provide insight for future design solutions for HMDs.
Although there are numerous studies that demonstrate that color vision deficient (CVD) individuals perform less well than color vision normal (CVN) individuals in tasks that require discrimination or ...identification of colored stimuli, there remains a need to quantify the relationship between the type and severity of CVD and performance on operationally relevant tasks.
Participants were classified as CVN (N = 45) or CVD (N = 49) using the Rabin cone contrast test, which is the standard color vision screening test used by the United States Air Force. In the color condition, test images that were representative of the size, shape, and color of symbols and lines used on fifth-generation fighter aircraft displays were used to measure operational performance. In the achromatic condition, all symbols and lines had the same chromaticity but differed in luminance. Subjects were asked to locate and discriminate between friend vs. foe symbols (red vs. green, or brighter vs. dimmer) while speed and accuracy were recorded.
Increasing color deficiency was associated with decreasing speed and accuracy for the color condition (R
> 0.2), but not for the achromatic condition. Mean differences between CVN and CVD individuals showed the same pattern.
Although lower CCT scores are clearly associated with lower performance in color related tasks, the magnitude of the performance loss was relatively small and there were multiple examples of high-performing CVD individuals who had higher operational scores than low-performing CVN individuals. Gaska JP, Wright ST, Winterbottom MD, Hadley SC. Color vision and performance on color-coded cockpit displays. Aerosp Med Hum Perform. 2016; 87(11):921-927.
A phenomenological model for pattern formation in a vertically vibrated granular layer is examined in order to investigate its nonlinear dynamics. The model comprises two coupled partial differential ...equations: one describes the evolution of the short-scale pattern, while the other enforces conservation of granular material. In a layer of moderate horizontal extent, the model predicts that a variety of exotic regular patterns may be stable, according to the system parameters. The usual cubic-order amplitude equations are unable to determine the stable solution over a significant parameter range; we compute the corresponding fifth-order terms necessary to resolve this degeneracy. When spatial modulation of the pattern is taken into account, in a sufficiently wide layer, a stability analysis of regular one-dimensional roll and two-dimensional square patterns demonstrates that each may suffer a modulational instability, which tends to localize the pattern. The corresponding modulational stability boundaries, for both rolls and squares, coincide with the transition between stable rolls and squares in the unmodulated problem. As a consequence, in a suitably large container, squares are always unstable, and corresponding numerical simulations indicate highly localized worm- or chain-like patterns. The numerical simulations and stability results are compared with appropriate experimental results.
In Experiment 1, antialiasing was found to improve performance on an orientation-discrimination task, whereas increasing display pixel-count did not. The latter finding was attributed to a decrease ...in image contrast associated with driving the CRT beyond its effective bandwidth. In Experiment 2, it was found that display resolution is the primary determinant of orientation-discrimination performance. This performance was not significantly improved by increasing antialiasing beyond a minimal level, suggesting that greater image detail can be substituted for antialias filtering. Finally, data obtained from an objective target-size calibration showed that nominal target size often does not accurately reflect the size (and hence distance) of simulated targets.
Society Records WINTERBOTTOM, P. D.
Mariner's mirror,
20/1/1/, Letnik:
97, Številka:
3
Journal Article
Recenzirano
The minutes from the Society for Nautical Research's Annual General Meeting at the National Museum of the Royal Navy in Portsmouth, England, on June 18, 2011, are presented. Such topics were ...discussed as marketing, publications, conferences, grant applications, and awards.
Objective: We sought to determine the optimal focal distance for a semitransparent monocular head-mounted display (HMD) integrated with a flight simulator display and to investigate whether observers ...experienced visual discomfort or impaired target recognition when using an HMD set at the optimal distance. Background: When an observer wears a monocular HMD and views a simulator display, focal distances of both displays must be within the observers' depth of focus to prevent blurred imagery. Because focal distance can vary by as much as 0.5 m in U.S. Air Force multifaceted simulator displays, we determined whether a monocular HMD could be integrated with a simulator display without blurred imagery or discomfort. Method: Depth of focus and visual recognition were measured with a staircase procedure, and visual discomfort was measured with a questionnaire. Results: Depth of focus was 0.64 diopters in one condition tested, but it was affected by luminance level and display resolution. It was recommended that HMD focal distance equal the optical midpoint of the range of viewing distances encountered in the simulator. Moreover, wearing an HMD produced a decline in recognition performance for targets presented on the simulator display despite both displays being within observers' depth of focus and producing no visual discomfort. Conclusion: Monocular HMDs can be integrated with multifaceted simulator displays without blurred imagery or visual discomfort, provided that the correct focal distance is adopted. Application: For situations involving simultaneously viewed visual displays.
Studies on the use of cholesteric liquid crystals (CLCs) as sensing phase for detection of organic vapours in air are described. Stock solutions of 1.0% (w/v) cholesteryl nonanoate (CN) and ...cholesteryl chloride (CC) were prepared in tetrahydrofuran. Binary mixtures, with compositions ranging from 0.18 to 0.25% of CC and 0.82–0.75% of CN, respectively, were prepared by appropriate mixing of the stock solutions. Films were cast by pipetting three 10
μl aliquots of the CLC solution mixture onto a glass disk, whose reverse side was made black to absorb unscattered light. The glass disk was adapted to the common end of a bifurcated optical fibre bundle and placed in a glass vial, which provided a headspace of organic vapours. Measurements were carried out at 27±1
°C, a temperature in which the CLC mixtures maintain their liquid crystalline properties. The responses of the CLC mixtures to vapours of ethanol, acetone, benzene, pyridine and hexane were investigated. The colour of the sensing phases depended on their compositions and exposure to organic vapours gives rise to a change in the optical characteristics of liquid crystals. It was found that the CLC layers containing 0.23–0.25% of CC had no significant change in optical properties when exposed to organic vapours and that ethanol did not cause any optical changes in the liquid crystal layers. Benzene as well as hexane always turned all the coloured liquid crystalline layers to colourless. The CLC layers exhibited different behaviours to vapours of acetone and pyridine. For example, the wavelengths of maximum scattering for the 0.19% CC layer were 530
nm in air, 545
nm in pyridine and 580
nm in acetone. The CLC layers showed reversibility. The lifetimes of these layers (interval of time in which the liquid crystalline phase exists, before crystallisation) were investigated by employing acetone and
n-hexane vapours. Average lifetimes of 14–15
min were found for films in contact with these vapours, while a lifetime of 205
min was possible when the CLC film was exposed to air.
