The Effect of the Range of a Modulating Phase Mask on the Retrieval of a Complex Object from Intensity Measurements

The authors have been supported by the postdoctoral project (1.1.1.2/16/I/001, 1.1.1.2/VIAA/1/16/199), the CAMART2 project (grant agreement ID 739508), the Latvian Investment and Development Agency (LIDA) project (KC-PI-2017/105), and the grant for the Latvian State Emeritus Scientists.In many fields of science, it is often impossible to preserve the information about the phase of the electromagnetic field, and only the information about the magnitude is available. This is known as the phase problem. Various algorithms have been proposed to recover the information about phase from intensity measurements. Nowadays, iterative algorithms of phase retrieval have become popular. Many of these algorithms are based on modulating the object under study with several masks and retrieving the missing information about the phase of an object by applying mathematical optimization methods. Several of these algorithms are able to retrieve not only the phase but also the magnitude of the object under study. In this study, we investigate the effect of the range of modulation of a mask on the accuracy of the retrieved magnitude and phase map. We conclude that there is a sharp boundary of the range of modulation separating the successfully retrieved magnitude and phase maps from those retrieved unsuccessfully. A decrease in the range of modulation affects the accuracy of the retrieved magnitude and phase map differently. © 2021 V. Karitans et al., published by Sciendo. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.Postdoctoral project (1.1.1.2/16/I/001, 1.1.1.2/VIAA/1/16/199); the Latvian Investment and Development Agency (LIDA) project (KC-PI-2017/105), and the grant for the Latvian State Emeritus Scientists; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

The Effect of Stimulus Contrast and Spatial Position on Saccadic Eye Movement Parameters

The study is supported by LCS Project No 2021/1-0219, the UL Foundation Project No 2260 and LU project No. Y5-AZ77-ZF-N-100. The research is being developed with the support of LZP FLP project No. lzp-2021/1-0219, LU Foundation and SIA “Mikrotikls” project No. 2260 and LU project No. Y5-AZ77-ZF-N-100. The Institute of Solid-State Physics, University of Latvia (Latvia), as a center of excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase 2 under Grant Agreement No. 739508, project CAMART2.Background: Saccadic eye movements are rapid eye movements aimed to position the object image on the central retina, ensuring high-resolution data sampling across the visual field. Although saccadic eye movements are studied extensively, different experimental settings applied across different studies have left an open question of whether and how stimulus parameters can affect the saccadic performance. The current study aims to explore the effect of stimulus contrast and spatial position on saccadic eye movement latency, peak velocity and accuracy measurements. (2) Methods: Saccadic eye movement targets of different contrast levels were presented at four different spatial positions. The eye movements were recorded with a Tobii Pro Fusion video-oculograph (250 Hz). (3) Results: The results demonstrate a significant effect of stimulus spatial position on the latency and peak velocity measurements at a medium grey background, 30 cd/m2 (negative and positive stimulus polarity), light grey background, 90 cd/m2 (negative polarity), and black background, 3 cd/m2 (positive polarity). A significant effect of the stimulus spatial position was observed on the accuracy measurements when the saccadic eye movement stimuli were presented on a medium grey background (negative polarity) and on a black background. No significant effect of stimulus contrast was observed on the peak velocity measurements under all conditions. A significant stimulus contrast effect on latency and accuracy was observed only on a light grey background. (4) Conclusions: The best saccadic eye movement performance (lowest latency, highest peak velocity and accuracy measurements) can be observed when the saccades are oriented to the right and left from the central fixation point. Furthermore, when presenting the stimulus on a light grey background, a very low contrast stimuli should be considered carefully. © 2023 by the authors. --//-- This is an open access article Goliskina V., Ceple I., Kassaliete E., Serpa E., Truksa R., Svede A., Krauze L., Fomins S., Ikaunieks G., Krumina G., The Effect of Stimulus Contrast and Spatial Position on Saccadic Eye Movement Parameters, (2023) Vision (Switzerland), 7 (4), art. no. 68, DOI: 10.3390/vision7040068 published under the CC BY v 4.0 licence.LCS Project No 2021/1-0219; UL Foundation Project No 2260; LU project No. Y5-AZ77-ZF-N-100; LZP FLP project No. lzp-2021/1-0219, LU Foundation and SIA “Mikrotikls” project No. 2260 and LU project No. Y5-AZ77-ZF-N-100. The Institute of Solid-State Physics, University of Latvia (Latvia), as a center of excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase 2 under Grant Agreement No. 739508, project CAMART2

A comparative analysis of colour–emotion associations in 16–88‐year‐old adults from 31 countries

As people age, they tend to spend more time indoors, and the colours in their surroundings may significantly impact their mood and overall well-being. However, there is a lack of empirical evidence to provide informed guidance on colour choices, irrespective of age group. To work towards informed choices, we investigated whether the associations between colours and emotions observed in younger individuals also apply to older adults. We recruited 7,393 participants, aged between 16 and 88 years and coming from 31 countries. Each participant associated 12 colour terms with 20 emotion concepts and rated the intensity of each associated emotion. Different age groups exhibited highly similar patterns of colour-emotion associations (average similarity coefficient of 0.97), with subtle yet meaningful age-related differences. Adolescents associated the greatest number but the least positively biased emotions with colours. Older participants associated a smaller number but more intense and more positive emotions with all colour terms, displaying a positivity effect. Age also predicted arousal and power biases, varying by colour. Findings suggest parallels in colour-emotion associations between younger and older adults, with subtle but significant age-related variations. Future studies should next assess whether colour-emotion associations reflect what people actually feel when exposed to colour

The sun is no fun without rain : Physical environments affect how we feel about yellow across 55 countries

Across cultures, people associate colours with emotions. Here, we test the hypothesis that one driver of this cross-modal correspondence is the physical environment we live in. We focus on a prime example – the association of yellow with joy, – which conceivably arises because yellow is reminiscent of life-sustaining sunshine and pleasant weather. If so, this association should be especially strong in countries where sunny weather is a rare occurrence. We analysed yellow-joy associations of 6625 participants from 55 countries to investigate how yellow-joy associations varied geographically, climatologically, and seasonally. We assessed the distance to the equator, sunshine, precipitation, and daytime hours. Consistent with our hypotheses, participants who live further away from the equator and in rainier countries are more likely to associate yellow with joy. We did not find associations with seasonal variations. Our findings support a role for the physical environment in shaping the affective meaning of colour.Peer reviewe

Comparing of saliency methods for sight prediction of real observer. Multi-spectral insight

Darbs ir uzrakstīts latviešu valodā uz 55 lapām, satur 37 att., 1.pielikumu un 44 literatūras avotus. Darba mērķis. Izstrādāt uzmanības modeli, ņemot vērā monitora spektrālo starojumu. Darba uzdevumi. Raksturot monitora spektrālas īpašības. Izstrādāt stimulu vadītas uzmanības modeli, kurā ir ņemtas vērā no objekta nākošas gaismas spektrālās īpašības. Pielietot modeli eksperimenta stimuliem un atrast saistības ar acu kustību raksturlielumiem. Raksturot uzmanības uzvedību atkarībā no stimula īpašībām. Subjekti. Kopā eksperimentos piedalījās 6 subjekti vecumā no 22 līdz 54 gadiem. 3 no tiem meklēšanas eksperimentā un 3 reakcijas laika eksperimentā. Rezultāti un secinājumi. Izstrādātais stimulu vadītās uzmanības modelis nodrošina augstu apstrādājamā attēla izšķirtspēju. Augstākais korelācijas koeficients ir atrasts starp maksimālo vērtību aktivācijas kartē un stimula Maikelsona kontrasta vērtību atvēruma vietā. Atslēgas vārdi. Uzmanība, uzmanības modelis, acu kustības, vizuālās meklēšanas eksperiments, vālīšu krāsu telpa.This master thesis is written in Latvian. It contains 55 pages, 37 pictures, 1 appendix and 44 literature references. The aim. To develop attention model, taking into account display emission spectral properties. Tasks. Characterize spectral emission of display primaries. Develop the model of stimulus driven attention. To apply the model to the experiment image and find correlations with eye movement characteristics. Subjects. 6 subjects participated in two different experiments, 3 subjects in each. Results and conclusions. Model process the image at high resolution. Resulting activation maps showed high correlation value with Mickelson contrast value of stimuli and search time. Keywords. Attention, model of attention, eye movements, visual search, cone color space

Color and form influence on perception of visual stimuli

Elektroniskā versija nesatur pielikumusRedzes uztvere ir sarežģīts process, kurš ir atkarīgs no stimula veida (forma, krāsa, kustība) un tā optiskajiem parametriem (spožuma, kontrasta, spektrālā sastāva u.c.). Formas uztvere redzes sistēmā sākas ar vizuālo detaļu novietojuma virziena un elementu garuma kodēšanu, kas hierarhiskā redzes sistēmas modelī atbilst primāras redzes garozas līmenim. Darbā ir pētīti orientētu virsmas tekstūru atpazīšanas raksturlielumi atkarībā no stimulu konteksta (blakus esoša papildus modulācija). Izmantotā metodika atšķīrās no iepriekš pielietotajām konteksta izraisītas modulācijas pētījumiem, kad kontrasta vietā ir izmantoti temporālie stimuli kopā ar maskēšanas metodi. Parādīts, ka uztveres treniņi ar teksturētām virsmām uzrāda atpazīšanas uzlabojumu, vismaz divreiz samazinot sākuma atpazīšanas slieksni. Redzes treniņos ar hromatiskām tekstūrām tika noskaidrots, ka lielākais sliekšņa pazeminājums ir novērojams pie sarkani-zaļajiem stimuliem. Piedāvāta metodika redzes parametru uzlabošanai ambliopijas gadījumā. Krāsu uztvere sākas tīklenē, kur krītoša gaisma tiek absorbēta trīs tipu receptoros un tālāk elektrisko signālu veidā nosūtītā augstākām smadzeņu zonām. Gadījumos, kad ģenētisko faktoru dēļ iztrūkst kāds no foto receptoru pigmentiem, izpaužas krāsu redzes traucējumi, kuru diagnostikai visbiežāk pielieto krāsu redzes testus tabulu veidā. Šīs pseidoizohromatiskās tabulas ne vienmēr ļauj viennozīmīgi atklāt krāsu redzes traucējumus, kam par iemeslu var būt drukāto testu lapu nodzeltēšana vai nepareiza apgaismojuma izvēle testa laikā. Lai objektīvi izanalizētu testu pielietojamību krāsu redzes traucējumu diagnosticēšanā, darbā tiek piedāvāti risinājumi, kas izmanto attēlu multispektrālās analīzes iespējas. Pielietotās metodes izmanto cilvēka hromatiskās jūtības īpatnības un ietver mašīnu redzes elementus. Izveidotā metode ļauj pētīt pseidoizohromatisko testu dizainu un analizēt to pielietojamību dažādos apgaismojumos. Dotā pētījuma rezultāti ir nozīmīgi krāsu redzes traucējumu pārbaudes testu izveidē un analīzē. Krāsu uztvere fizioloģiski balstās uz trīs tīklenes fotoreceptoru tipiem un rada tādas parādības kā metamerisms, krāsu pastāvīgums, krāsu indukcija, kā arī redzes ilūzijas. Neskatoties uz to, ka jau sen ir izpētīta vālīšu gaismas jutība, krāsu redzes mehānismiem redzes garozā tiek pievērsta pastiprināta uzmanība arī patlaban. Darbā tika pētīti krāsu pēcefekti personām ar normālu trihromātisko un arī traucētu krāsu redzi un atrastas būtiskās atšķirības tiem novēroto pēcefektu krāsās. Mūsu rezultāti kopumā sakrīt ar citu autoru darbos iegūtajiem, taču sniedz papildus informāciju par krāsu pēcefekta mehānismiem. Darbā izveidotā pēcefekta izpētes metode var tikt attīstīta, kā alternatīva metode krāsu redzes traucējumu testēšanā. Krāsu un formas redzes uztvere „dala” līdzīgus apstrādes ceļus (ventrālā plūsma). Pēc objekta formas (kontūras) uztveršanas, notiek neapzināta citu objekta parametru aizpildīšana, piemēram, krāsa vai tekstūra. Pēcefekta aizpildīšanas (filling-in) pētījumos ir parādīts, ka augstākajos redzes garozas līmeņos formas uztvere ir saistīta ar krāsu kodēšanu. Krāsas, kas veido spēcīgākos pēcefektus aizpildīšanas eksperimentos, ir atšķirīgas no pamata krāsu asīm laterālajā ceļgalveida ķermenī un unikālo toņu virzieniem.Visual perception is a complex process, which depends on the attributes of the stimulus (shape, color, and movement), surround and its optical parameters (radiance, contrast, spectral composition). Form perception in the hierarchical organization of the visual system starts in the primary visual cortex, there most of the simple cell neurons are tuned to the elongated oriented details of different spatial frequency. Texture segmentation characteristics are studied in the current work, depending on the context around the stimuli. The methodology used is different from other contextual modulation studies, where contrast is used instead of the temporal stimulus. It is shown that perceptual training with textured surfaces show improvement in recognition, at least twice reducing the initial detection threshold. Visual exercises for chromatic textures showed that the largest threshold decrease is observed at the red-green stimuli. Method of temporally variable stimuli is used together with ferroelectric shutter goggles to improve the visual characteristics in the case of amblyopia. Color perception starts at the level of retinal photoreceptors, where the incident light is absorbed by three classes of receptor and in the form of electrical signals is sent to higher cortical areas. Due to genetic factors receptor pigments can be absent, which result in the deficiencies of the color vision. The most popular available color vision diagnostic tests are pseudoisochromatic table. However, not always these tests clearly reveal color vision deficiencies, which could be due to the aging of the printed or choice of the improper source of light. To objectively analyze the performance of the color vision diagnostic plates, we offer solutions based on the multispectral imaging with applied algorithms. The methods use chromatic sensitivities of the photopigments to model a performance of the defective color vision together with machine vision elements for the objective evaluation of the test diagnostic efficiency. The established method makes it possible to study pseudoisochromatic tables design and analyze their applicability in different lighting conditions. Study gains important results for the analysis and design of the color vision deficiency tests. Color perception is physiologically based on the three classes of retinal photoreceptors with the following postreceptoral and cortical processing, which causes different phenomena such as, metamerism, color constancy, color induction, as well as visual illusions. Despite the fact that cone sensitivities are well studied, color vision mechanisms of visual cortex are widely studied field our days. Color aftereffects are studied in the subjects with normal trichromatic color vision, as also in subjects with impaired color vision. Significant differences in the aftereffect colors are found for subjects. Our results generally concur with the findings of other authors, but provide additional information on color aftereffect mechanisms. Aftereffect method could be used for diagnostics of color vision deficiencies. Color and shape perception is processed in the ventral pathway. Surface perception includes the processes of construction of shape based on the contour information with following assignment of the visible features, such as color, brightness and texture. Contour filling-in studies have shown that in the cortex form perception is related to the color processing. Colors that produce the strongest aftereffect filling-in are not always complementary, and can be produce between more than two colors. Identified strongest colors are not aligned along unique hue direction or cardinal direction of color space

Rayleigh Equation Anomaloscope from Commercially Available LEDs

Most precise classification of CVD (color vision deficits) can be provided by using anomaloscope. Today anomaloscopes are available, which can evaluate red-green (Rayleigh) and blue-green (Moreland) color defects.<p>DOI: <a href="http://dx.doi.org/10.5755/j01.ms.18.2.1928">http://dx.doi.org/10.5755/j01.ms.18.2.1928</a></p

Color-discrimination threshold determination using pseudoisochromatic test plates

We produced a set of pseudoisochromatic plates for determining individual color-difference thresholds to assess test performance and test properties, and analyzed the results. We report a high test validity and classification ability for the deficiency type and severity level (comparable to that of the fourth edition of the Hardy–Rand–Rittler (HRR) test). We discuss changes of the acceptable chromatic shifts from the protan and deutan confusion lines along the CIE xy diagram, and the high correlation of individual color-difference thresholds and the red–green discrimination index. Color vision was tested using an Oculus HMC anomaloscope, a Farnsworth D15, and an HRR test on 273 schoolchildren, and 57 other subjects with previously diagnosed red–green color-vision deficiency