For My Eyes Only

Secret Worlds ◽  
2021 ◽  
pp. 53-84
Author(s):  
Martin Stevens
Keyword(s):  
Visual Processing ◽  
Colour Vision ◽  
Green Light ◽  
Light Spectrum ◽  
Colour Perception ◽  
Mantis Shrimp ◽  
Uv Vision ◽  
Different Dimensions ◽  
Different Parts ◽  
Polarisation Vision

This chapter explores how vision is used by animals and the diversity in ways of seeing. It first details how colour vision works, focusing on the example of honeybees, which, like humans, are trichromatic and have good colour vision. Bees have a dedicated ultraviolet (UV) receptor, and then one for seeing shortwave (blue) and mediumwave (green) light. Other animals deviate more substantially, in that they have either more or fewer receptors used in colour vision, and hence different ‘dimensions’ of colour perception. The chapter then considers how jumping spiders use UV vision in identifying known or suitable prey species, as well as in mating. It also looks at polarisation vision in mantis shrimp. Mantis shrimp are bizarre in the number of receptors they have, each sensitive to different parts of the light spectrum. Finally, the chapter assesses how toads recognize prey from non-prey. The toad’s visual system acts as a ‘feature detector’ based on several stages of visual processing, producing a quick and appropriate response to a set of criteria that reliably encode objects of particular importance—in this case, food.

scholarly journals Blue as an Underrated Alternative to Green: Photoplethysmographic Heartbeat Intervals Estimation under Two Temperature Conditions

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4241
Author(s):  
Evgeniia Shchelkanova ◽  
Liia Shchapova ◽  
Alexander Shchelkanov ◽  
Tomohiro Shibata
Keyword(s):  
Blue Light ◽  
Characteristic Point ◽  
Biological Effects ◽  
Green Light ◽  
Estimation Accuracy ◽  
Lower Sensitivity ◽  
Light Spectrum ◽  
Cardiovascular Parameter ◽  
Temperature Conditions ◽  
Characteristic Points

Since photoplethysmography (PPG) sensors are usually placed on open skin areas, temperature interference can be an issue. Currently, green light is the most widely used in the reflectance PPG for its relatively low artifact susceptibility. However, it has been known that hemoglobin absorption peaks at the blue part of the spectrum. Despite this fact, blue light has received little attention in the PPG field. Blue wavelengths are commonly used in phototherapy. Combining blue light-based treatments with simultaneous blue PPG acquisition could be potentially used in patients monitoring and studying the biological effects of light. Previous studies examining the PPG in blue light compared to other wavelengths employed photodetectors with inherently lower sensitivity to blue, thereby biasing the results. The present study assessed the accuracy of heartbeat intervals (HBIs) estimation from blue and green PPG signals, acquired under baseline and cold temperature conditions. Our PPG system is based on TCS3472 Color Sensor with equal sensitivity to both parts of the light spectrum to ensure unbiased comparison. The accuracy of the HBIs estimates, calculated with five characteristic points (PPG systolic peak, maximum of the first PPG derivative, maximum of the second PPG derivative, minimum of the second PPG derivative, and intersecting tangents) on both PPG signal types, was evaluated based on the electrocardiographic values. The statistical analyses demonstrated that in all cases, the HBIs estimation accuracy of blue PPG was nearly equivalent to the G PPG irrespective of the characteristic point and measurement condition. Therefore, blue PPG can be used for cardiovascular parameter acquisition. This paper is an extension of work originally presented at the 42nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society.

scholarly journals How colour palettes in maps are re-coloured by daltonization methods

2019 ◽  
Vol 1 ◽  
pp. 1-2
Author(s):  
Anne Kristin Kvitle
Keyword(s):  
Colour Vision ◽  
Information Graphics ◽  
Male Population ◽  
Colour Perception ◽  
Female Population ◽  
Other Information ◽  
Map Design ◽  
Enhancement Method ◽  
Choropleth Map ◽  
Future Work

<p><strong>Abstract.</strong> The ability of identifying objects and elements based on colour is important in order to decode the information in a map or other information graphics. For this reason, the colours need to appear correct and be perceived in the desired and intended way. Map reading is reported as a challenging task for people with impaired colour vision. In reviews of the challenges of colour vision deficiencies (CVD) in everyday life (Cole, 2004), up to 60 % of the subjects in the studies reported problems in reading colour coded charts, slides and prints. Other studies (Carter and Silverstein, 2010) describes the difficulties to distinguish and identify coloured objects in weather, financial and other maps and charts.</p><p>Colour vision deficiencies are common, where congenital CVD affects about 8 % of the male population and 0.4 % of the female population. In addition, colour vision and colour perception may be affected by medical conditions or injury (acquired CVD) and situational conditions (situation induced CVD).</p><p>Reviews of visual usability and accessible map design conclude that few maps appear to have been designed with CVD users in mind (Cartwright, 2015) and that the design efforts or research of accessible colours palettes for CVD observers are mostly limited to thematic maps such as choropleths (Kvitle, 2018).</p><p>Daltonization methods are image processing methods to automatically enhance information in existing images. A common enhancement method is re-colouring, changing the colours in the original image to make be more distinguishable to the CVD observers. The daltonization method targets a specific type of CVD, and may also have been designed for specific applications (natural images, scientific images, information graphics etc). Therefore, the evaluation of the methods is often based on a limited set of test images. Using one specific map image as input will give very different results based on the daltonization methods.</p><p>The aim of the work is primarily to examine how the colour palettes in a map are altered by different daltonization methods. Second, the aim is to explore how different map types are influenced by the daltonization methods and to propose requirements and guidelines for test images for future work.</p><p> The set of test images in this work includes</p><ul><li>Information graphics (such as a tube map).</li><li>Choropleth map.</li><li>Reference map based on different map providers.</li></ul><p> To illustrate the visual differences, CVD simulation methods are applied on the original images and the daltonized versions of the images.</p>

scholarly journals Photosynthetic Physiology of Blue, Green, and Red Light: Light Intensity Effects and Underlying Mechanisms

2021 ◽  
Vol 12 ◽  
Author(s):  
Jun Liu ◽  
Marc W. van Iersel
Keyword(s):  
Blue Light ◽  
Interactive Effect ◽  
Red Light ◽  
Green Light ◽  
Photosynthetic Photon Flux Density ◽  
Interactive Effects ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Spectrum ◽  
Response Curves

Red and blue light are traditionally believed to have a higher quantum yield of CO2 assimilation (QY, moles of CO2 assimilated per mole of photons) than green light, because green light is absorbed less efficiently. However, because of its lower absorptance, green light can penetrate deeper and excite chlorophyll deeper in leaves. We hypothesized that, at high photosynthetic photon flux density (PPFD), green light may achieve higher QY and net CO2 assimilation rate (An) than red or blue light, because of its more uniform absorption throughtout leaves. To test the interactive effects of PPFD and light spectrum on photosynthesis, we measured leaf An of “Green Tower” lettuce (Lactuca sativa) under red, blue, and green light, and combinations of those at PPFDs from 30 to 1,300 μmol⋅m–2⋅s–1. The electron transport rates (J) and the maximum Rubisco carboxylation rate (Vc,max) at low (200 μmol⋅m–2⋅s–1) and high PPFD (1,000 μmol⋅m–2⋅s–1) were estimated from photosynthetic CO2 response curves. Both QYm,inc (maximum QY on incident PPFD basis) and J at low PPFD were higher under red light than under blue and green light. Factoring in light absorption, QYm,abs (the maximum QY on absorbed PPFD basis) under green and red light were both higher than under blue light, indicating that the low QYm,inc under green light was due to lower absorptance, while absorbed blue photons were used inherently least efficiently. At high PPFD, the QYinc [gross CO2 assimilation (Ag)/incident PPFD] and J under red and green light were similar, and higher than under blue light, confirming our hypothesis. Vc,max may not limit photosynthesis at a PPFD of 200 μmol m–2 s–1 and was largely unaffected by light spectrum at 1,000 μmol⋅m–2⋅s–1. Ag and J under different spectra were positively correlated, suggesting that the interactive effect between light spectrum and PPFD on photosynthesis was due to effects on J. No interaction between the three colors of light was detected. In summary, at low PPFD, green light had the lowest photosynthetic efficiency because of its low absorptance. Contrary, at high PPFD, QYinc under green light was among the highest, likely resulting from more uniform distribution of green light in leaves.

scholarly journals Behavioural evidence for polychromatic ultraviolet sensitivity in mantis shrimp

2018 ◽  
Vol 285 (1884) ◽  
pp. 20181384 ◽  
Author(s):  
Michael J. Bok ◽  
Nicholas W. Roberts ◽  
Thomas W. Cronin
Keyword(s):  
Narrow Band ◽  
Visible Range ◽  
Mantis Shrimp ◽  
Visual Systems ◽  
Uv Vision ◽  
Wavelength Discrimination ◽  
Behavioural Experiments ◽  
Polarization Detection ◽  
Behavioural Evidence ◽  
Uv Range

Stomatopod crustaceans are renowned for their elaborate visual systems. Their eyes contain a plethora of photoreceptors specialized for chromatic and polarization detection, including several that are sensitive to varying wavelength ranges and angles of polarization within the ultraviolet (UV) range (less than 400 nm). Behavioural experiments have previously suggested that UV photoreception plays a role in stomatopod communication, but these experiments have only manipulated the entire UV range. Here, using a behavioural approach, we examine UV vision in the stomatopod Haptosquilla trispinosa . Using binary trained choice assays as well as innate burrow-choice experiments, we assessed the ability of H. trispinosa to detect and respond to narrow-band LED stimuli peaking near 314 nm (UVB) versus 379 nm (UVA) in wavelength. We find that H. trispinosa can discriminate these stimuli and appears to display an aversive reaction to UVB light, suggesting segregated behavioural responses to stimuli within the UV range. Furthermore, we find that H. trispinosa can discriminate stimuli peaking near 379 nm versus 351 nm in wavelength, suggesting that their wavelength discrimination in the UV is comparable to their performance in the human-visible range.

scholarly journals THE SENSIBILITY OF THE NOCTURNAL LONG-EARED OWL IN THE SPECTRUM

1940 ◽  
Vol 23 (6) ◽  
pp. 709-717 ◽  
Author(s):  
Selig Hecht ◽  
Maurice Henri Pirenne
Keyword(s):  
Infrared Radiation ◽  
Energy Content ◽  
Green Light ◽  
Visible Spectrum ◽  
Low Light ◽  
Light Intensities ◽  
Different Parts

Infrared radiation (750–1500 mµ) produces no iris contraction in the typically nocturnal long-eared owl even when the energy content is millions of times greater than that of green light which easily elicits a pupil change. The energies in different parts of the visible spectrum required for a minimal iris response yield a spectral visibility curve for the owl which is the same as the human visibility curve at low light intensities. Functionally, the owl's vision thus corresponds to the predominantly rod structure of its retina, and the idea that nocturnal owls have a special type of vision sensitive to infrared radiation for seeing in the woods at night is erroneous.

Colour Vision in Migraine: Selective Deficits for S-Cone Discriminations

Cephalalgia ◽  
2005 ◽  
Vol 25 (6) ◽  
pp. 412-423 ◽  
Author(s):  
AJ Shepherd
Keyword(s):  
Colour Vision ◽  
Visual Pathways ◽  
Control Groups ◽  
Colour Perception ◽  
Threshold Detection ◽  
The Third ◽  
And Control

Three studies are reported that explore colour perception in migraine. In each, sensitivity for colours detected selectively by the S-cones and the L- and M-cones was assessed separately. The first study assessed the discrimination of small colour differences using the Farnsworth-Munsell 100-hue test. The second assessed threshold detection for purple, yellow, red and green targets on five equiluminant background colours. The third examined supra-threshold colour scaling using two colour series, purple-yellow and red-green. Each study indicated that differences in colour perception between migraine and control groups were restricted to colours detected by the S-cones, there were no differences in performance for colours detected by the L- and M-cones. The results are discussed in terms of possible pathologies in the early visual pathways.

Highly Accurate Measurements of Human Colour Vision Parameters with Application to Diagnostics

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 111-111 ◽  
Author(s):  
A V Chistopolov
Keyword(s):  
Colour Vision ◽  
Measurement Accuracy ◽  
Wide Spectrum ◽  
Testing Procedure ◽  
Chromaticity Diagram ◽  
Colour Perception ◽  
Small Deviations ◽  
Standard Observer ◽  
Prolonged Testing ◽  
Normal Perception

A new method for measuring a wide spectrum of parameters describing a subject's colour vision is presented. It is based on a portable visual colorimeter, ‘Spectr-3M’, designed in our laboratory and has several useful features: (1) it enables testing over a wide area of the chromaticity diagram; (2) it allows the use of continuously changing colour stimuli; (3) the measurement accuracy is high; (4) the testing procedure is fast and comfortable, minimising the effects caused by prolonged testing and increasing the reliability of the data. Using this method we have revealed significant deviations from the CIE 1931 standard colorimetric observer in the colour perception of several subjects previously attested by the Rabkin and Ishihara charts as having normal perception. The data obtained by our method are more informative than results obtained with the Nagel anomaloscope, revealing not only general features of colour perception defects (as the anomaloscope), but allowing more detailed characterisation, including even small deviations from the CIE 1931 standard observer.

METHOD OF ASYMPTOTIC PARTIAL DECOMPOSITION OF DOMAIN

1998 ◽  
Vol 08 (01) ◽  
pp. 139-156 ◽  
Author(s):  
G. P. PANASENKO
Keyword(s):  
Small Parameter ◽  
Interface Conditions ◽  
Singular Behavior ◽  
Common Boundary ◽  
Partial Decomposition ◽  
Regular Behavior ◽  
Different Dimensions ◽  
The Common ◽  
Different Parts ◽  
Passage To The Limit

A new method of partial decomposition of a domain is proposed for partial differential equations, depending on a small parameter. It is based on the information about the structure of the asymptotic solution in different parts of the domain. The principal idea of the method is to extract the subdomain of singular behavior of the solution and to simplify the problem in the subdomain of regular behavior of the solution. The special interface conditions are imposed on the common boundary of these partially decomposed subdomains. If, for example, the domain depends on the small parameter and some parts of the domain change their dimension after the passage to the limit, then the proposed method reduces the initial problem to the system of equations posed in the domains of different dimensions with the special interface conditions.

scholarly journals On negative after-images with pure spectral colours

1913 ◽  
Vol 86 (585) ◽  
pp. 117-118
Keyword(s):  
Colour Vision ◽  
Stray Light ◽  
Experimental Conditions ◽  
Colour Perception ◽  
Green Colour ◽  
Dark Room

In a paper “On Negative After-Images and Successive Contrast with Pure Spectral Colours,” by Mr. A. W. Porter, F. R. S., and Dr. F. W. Edridge-Green, the authors describe certain experiments, which they consider impossible of explanation on either the Hering or the Young-Helmholtz theory of colour vision. In justice to Thomas Young, it is only fair to point out a discrepancy between the title of the paper and the experimental conditions therein described, viz.: “The method adopted was as follows: In a dark room, in which, however, there was a certain amount of stray light , a horizontal spectrum, as pure as possible, was projected on a screen. A portion of the retina of one eye was then fatigued by rigidly gazing at a portion of another spectrum, isolated in the Edridge-Green colour-perception spectrometer. . . . After the fatiguing light had been viewed for about 20 seconds, the eye was turned to the screen, so that the after-image formed a band running right across the spectrum on the screen and occupying its centre.”

scholarly journals Disruptive coloration, crypsis and edge detection in early visual processing

2006 ◽  
Vol 273 (1598) ◽  
pp. 2141-2147 ◽  
Author(s):  
Martin Stevens ◽  
Innes C Cuthill
Keyword(s):  
Edge Detection ◽  
Pattern Matching ◽  
Visual Processing ◽  
Colour Vision ◽  
The Body ◽  
Detection Algorithms ◽  
Avian Predators ◽  
Early Visual Processing ◽  
Disruptive Coloration ◽  
Risk Of Predation

Many animals use concealing markings to reduce the risk of predation. These include background pattern matching (crypsis), where the coloration matches a random sample of the background and disruptive patterns, whose effectiveness has been hypothesized to lie in breaking up the body into a series of apparently unrelated objects. We have previously established the effectiveness of disruptive coloration against avian predators, using artificial moth-like stimuli with colours designed to match natural backgrounds as perceived by birds. Here, we investigate the mechanism by which disruptive patterns reduce detectability, using a computational vision model of edge detection applied to photographs of our experimental stimuli, calibrated for bird colour vision. We show that, disruptive coloration is effective by exploiting edge detection algorithms that we use to model early visual processing. Thus, ‘false’ edges are detected within the body rather than at its periphery, so inhibiting successful detection of the animal's body outline.

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