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... filters are typically used to set fixed parameters (such as the average luminance) , variable filters to control the brightness continuously (for instance , in an increment threshold test) . Table 3 presents some types of neutral density filters . Require high voltages , work by polarization . ...
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... A basic understanding of the visual adaptation process is necessary in order to tackle glare from a sequential perspective. The human eye is capable of luminance adaptation across 11 log units of luminance levels [22], courtesy of cone and rod photoreceptors. They enable neural adaptation across 2-3 log units of luminance, beyond which photochemical adaptation takes place [8,23]. ...
This paper proposes that the light intensities of adjacent interior spaces should be concurrently evaluated to reduce the risk of glare when evacuees transition between spaces to reach the final exit. The prevention of glare during daytime evacuation has the potential to smoothen the evacuation process from a building. As all legislative, regulatory, and assessment tool recommendations currently used in Malaysia measure illuminance (in lux), this paper similarly evaluates illuminance instead of luminance for ease of initial adoption in the country. Illuminance recommendations in MS1525:2019, LEED, DOSH Guidelines, UBBL, GBI, GreenRE, Melaka Green Seal, and MyCREST were compared to determine the contrast ratio. The illuminance contrast is greatest at the final exit points, such as from parking structures, lobbies, and staircases, which are benchmarked against the Malaysian sky illuminance that can reach 100,000 lux. A contrast ratio as high as 2000:1 may occur if Malaysian offices were designed to only achieve the minimum illuminance requirements. Of the three assessed final exit spaces, naturally-lit fire escape staircases were selected for modelled simulation of illuminance performance using VELUX Daylight Visualiser 2. The findings ascertained that most typical staircase layouts are able to exceed the minimum illuminance requirements at noon, when the sun is potentially the most intense, although the contrast ratio may still reach 1480:1. While the contrast between intermediate spaces are acceptable, those between the final exit transitions and the outdoors are high, suggesting a risk of glare. Further studies are required to determine strategies to facilitate visual adaptation for Malaysians, such as the identification of an ideal acceptable illuminance contrast ratio, temporal adaptation period, or distance-based parameters.
... Maxwell [50] introdujo un enfoque óptico alternativo por medio de una lente que forma imagen en el plano de la pupila (Fig. 3B), con lo que el observador ve un campo uniformemente iluminado y el área de estimulación está determinada por la lente de campo [17]. Las ventajas de esta disposición son que puede producir estímulos en los que el enfoque, la forma y el tamaño son independientes de la iluminancia retiniana; además, los niveles de luz que llegan a la retina pueden ser superiores a los producidos por los sistemas de visión libre [51]; y la imagen retiniana está libre de la difusión intraocular que generan el iris y la esclerótica [52]. Una desventaja de esta disposición es que no es adecuada para fuentes de luz muy pequeñas [17]. ...
... Como se mencionó, un problema potencial de esta disposición es que el ojo tiene que posicionarse cuidadosamente a una distancia determinada para enfocar la lente de campo, pues un pequeño cambio en dicha posición producirá un desenfoque en la imagen. Para superar este problema, se han propuesto disposiciones más complejas [51]; sin embargo, para muchos experimentos sin formación de imágenes, el montaje de la Fig. 1B es adecuado y se sigue utilizando, por ejemplo, para estudiar los mecanismos de adaptación a la luz en la retina [54,55]. Los sistemas de visión maxwelliana son muy útiles para evitar la modulación de la iluminación retiniana debida a las variaciones en el tamaño pupilar que pueden ser ocasionadas por otros factores que lo afectan, con lo que se logra un mejor control de las condiciones experimentales. ...
... Maxwellian view affords control of the shape, size and focus of the stimulus independently of the pupil size to precisely control the retinal illumination. 28,[30][31][32][33][34] The position of the observer's eye must be in the correct position during the entire experimental procedure. 7. Homogenously distribute the primaries in the optical pathway that forms the retinal image. ...
Melanopsin-mediated visual and non-visual functions are difficult to study in vivo. To isolate melanopsin responses, non-standard light stimulation instruments are required, with at least as many primaries as photoreceptor classes in the eye. In this protocol, we describe the physical light calibrations of the display instrumentation, control of stimulus artefacts, and correction of individual between-eye differences in human observers. The protocol achieves complete photoreceptor silent substitution in psychophysical, pupillometry, and electroretinographic experiments for probing melanopsin, rod, and cone function. For complete details on the use and execution of this protocol, please refer to Uprety et al. (2022).1.
... The observer sees the lens uniformly filled with light and the stimulation area is determined by the lens size (Wyszecki and Stiles, 2000). The advantages of this arrangement are: (1) it can produce stimulus where the focus, shape, and size are independent of the retinal illuminance; (2) the light levels reaching the retina can be higher than those produced by free-viewing systems (Burns and Webb, 2010); and (3) the retinal image is free of intraocular scattering generated by the iris and the sclera (van den Berg, 1995). One disadvantage of this arrangement is that it is not adequate for very small light sources (Wyszecki and Stiles, 2000). ...
... A small change in the position of the object will produce a defocus on the image. To overcome this issue, more complex arrangements were proposed (Burns and Webb, 2010); however, for many nonimage-forming experiments, the setup of Fig. 1B is adequate. ...
... For a deeper explanation of Maxwellian view arrangements and optical computation, we encourage the reader to consult the works of Burns and Webb (2010), Westheimer (1966), and Wyszecki and Stiles (2000). ...
We assessed how rod excitation (R) affects luminance (L $+$ + M $+$ + S) and chromatic [L/(L $+$ + M)] reaction times (RTs). A four-primary display based on the overlapped images of two spectrally modified monitors, which allowed specific or combined [L $+$ + M $+$ + S $+$ + R, L/(L $+$ + M) + R] photoreceptor stimulation, was used to present a C-target stimulus differing from the background only by the selected stimulation. For the luminance pathway, rod input increased RTs, suggesting a suppressive rod–cone interaction. The responses of the chromatic pathway were faster when rods were involved, suggesting a major role of rods in mesopic color perception.
... The observer sees the lens uniformly filled with light and the stimulation area is determined by the lens size (Wyszecki and Stiles, 2000). The advantages of this arrangement are: (1) it can produce stimulus where the focus, shape, and size are independent of the retinal illuminance; (2) the light levels reaching the retina can be higher than those produced by free-viewing systems (Burns and Webb, 2010); and (3) the retinal image is free of intraocular scattering generated by the iris and the sclera (van den Berg, 1995). One disadvantage of this arrangement is that it is not adequate for very small light sources (Wyszecki and Stiles, 2000). ...
... A small change in the position of the object will produce a defocus on the image. To overcome this issue, more complex arrangements were proposed (Burns and Webb, 2010); however, for many nonimage-forming experiments, the setup of Fig. 1B is adequate. ...
... For a deeper explanation of Maxwellian view arrangements and optical computation, we encourage the reader to consult the works of Burns and Webb (2010), Westheimer (1966), and Wyszecki and Stiles (2000). ...
This chapter describes the most common setups that scientists use for generating light stimulation, from lab-made approaches to commercially available technologies. The studied optical stimulation systems are divided into nonimage-forming and image-forming arrangements. Two classical systems widely used are among the first: the Maxwellian view system and the Ganzfeld stimulator. Between the image-forming arrangements, the focus is on approaches that consider off-the-shelf devices and the recent appearance of multi-primary displays, which allow the inclusion of more primaries and the generation of stimulation for independent and combined photoreceptor and postreceptoral excitations. Some of the several limitations that can have important implications in research practice are also examined, such as those related to color gamut, sampling frequency, light range, and spatial resolution.
Since experimentation on how optical radiation is processed by the human neural system requires the reliability of the parameters and variables under study to be assured, the characterization and consequent calibration of experimental devices are essential. Therefore the chapter discusses a set of characterization and calibration principles that researchers should consider when carrying out experiments with the described optical stimulators. Outstanding characteristics are stimulator response curve, primaries' spectral power distribution, additivity, modulation transfer function, and temporal stability. Finally, some possible sources of artifacts that researchers should consider when these stimulators are used are presented. Throughout this last section, data based on different optical stimulator measurements is provided.
... The white light-emitting diode (LED) with a green filter (520 nm) provided the filled-circle stimulus (Fig. 2E) in the Maxwellian view illumination. 37 The diameter of the light source image at the pupil plane was 3.25 mm, below the minimal registered size of subjects' pupils. The power of LED at the system output was measured by placing an additional sensor at the pupil plane after removing filter F2 of known transmission (a set of Thorlabs filters, NE 10A-A and NE 20A-A; common transmission, 0.125%). ...
Purpose:
Two-photon vision relies on the perception of pulsed infrared light due to two-photon absorption in visual pigments. This study aimed to measure human pupil reaction caused by a two-photon 1040-nm stimulus and compare it with pupil responses elicited by 520-nm stimuli of similar color.
Methods:
Pupillary light reflex (PLR) was induced on 14 dark-adapted healthy subjects. Three types of fovea-centered stimuli of 3.5° diameter were tested: spirals formed by fast scanning 1040-nm (infrared [IR] laser) or 520-nm (visible [VIS] laser) laser beams and uniformly filled circle created by 520-nm LED (VIS light-emitting diode [LED]). The power of visible stimuli was determined with a dedicated procedure to obtain the same perceived brightness equivalent as for 800 µW used for two-photon stimulation.
Results:
The minimum pupil diameter for IR laser was 88% ± 10% of baseline, significantly larger than for both VIS stimuli: 74% ± 10% (laser) and 69% ± 9% (LED). Mean constriction velocity and time to maximum constriction had significantly smaller values for IR than for both VIS stimuli. Latency times were similar for IR and VIS lasers and slightly smaller for VIS LED.
Conclusions:
The two-photon stimulus caused a considerably weaker pupil reaction than one-photon stimuli of the same shape, brightness, and similar color. The smaller pupil response may be due to weaker two-photon stimulation of rods relative to cones as previously observed for two-photon vision. Contrary to normal vision, in a two-photon process the stray light is not perceived, which might reduce the number of stimulated photoreceptors and further weaken the PLR.
... FCP devices employ typically a Maxwellian view setup in contrast to standard automated perimetry , which means that the illumination source is made optically conjugate to the pupil of the eye (Burns and Webb, 1995). This leads to important implications with regard to the effect of pupil size on threshold determinations. ...
Fundus-controlled perimetry (FCP, also called 'microperimetry') allows for spatially-resolved mapping of visual sensitivity and measurement of fixation stability, both in clinical practice as well as research. The accurate spatial characterization of visual function enabled by FCP can provide insightful information about disease severity and progression not reflected by best-corrected visual acuity in a large range of disorders. This is especially important for monitoring of retinal diseases that initially spare the central retina in earlier disease stages. Improved intra-and inter-session retest-variability through fundus-tracking and precise point-wise follow-up examinations even in patients with unstable fixation represent key advantages of these technique. The design of disease-specific test patterns and protocols reduces the burden of extensive and time-consuming FCP testing, permitting a more meaningful and focused application. Recent developments also allow for photoreceptor-specific testing through implementation of dark-adapted chromatic and photopic testing. A detailed understanding of the variety of available devices and test settings is a key prerequisite for the design and optimization of FCP protocols in future natural history studies and clinical trials. Accordingly, this review describes the theoretical and technical background of FCP, its prior application in clinical and research settings, data that qualify the application of FCP as an outcome measure in clinical trials as well as ongoing and future developments.
... Limited to the optimal brightness of lighting, a previous study found that older people prefer higher luminosity due to the normal aging of their vision [14]. More specifically, as the pupil size decreases with age, less illuminance reaches the retina [15]. This explains why older people require higher illuminance levels [14]. ...
This study investigates an optimal chromaticity and placement of refrigerator lighting to meet users' preference. In the experiment, eighteen lighting stimuli were provided by combining six chromaticities and three placements. A total of 177 women aged 20 to 69 participated and assessed the lighting stimuli using ten affective scales. Based on the assessments, we derived four aspects to describe the characteristics of lighting styles: performance, aesthetics, visual comfort, and overall satisfaction. Specifically, cool white lighting placed in front appealed the well-functioning, performance support aspect. Further, when the shelves were lit in magenta-white, the refrigerator interior was evaluated to be the most attractive. When visual comfort matters more, shelf lighting in cyan-white would be optimal. An age effect was also discovered. Younger participants in their 20s and 30s preferred cool white when lit indirectly. Participants over 40, however, found magenta-white more attractive, especially when they viewed it directly. By expanding this study to diverse product categories, it could produce additional empirical findings for designers, so that they may choose and place lighting properties more efficiently and successfully.
... Confusion about the meaning of trolands persists today. For example, the second edition of OSA's "The Science of Color" ( [6], p. 92) states, "The troland value is often referred to as retinal illuminance, but this usage is technically incorrect," yet OSA's Handbook of Optics says, "The troland is a unit of illuminance (luminous power per unit area) … at the retina (the retinal illuminance)" ( [7], p. 28.3). According to the International Commission on Illumination (CIE), the troland (Td) is a "unit used to express a quantity proportional to retinal illuminance produced by a light stimulus" [8], but this definition fails to specify the optical nature of a troland or to provide a basis for understanding its proportional relationship with retinal illuminance. ...
... Equation (8) is an expression for areal flux density arriving at the retinal image of an extended source. This is the same equation given by Burns and Webb assuming z 0 16.7 mm [7]. The numerator is the product of source luminance and pupil area. ...
Trolands are a widely used measure of retinal illuminance in vision science and visual optics, but disagreements exist for the definition and interpretation of this photometric unit. The purpose of this communication is to resolve the confusion by providing a sound conceptual basis for interpreting trolands as a measure of angular flux density incident upon the retina. Using a simplified optical analysis, we show that the troland value of an extended source is the intensity in micro-candelas of an equivalent point source located at the eye’s posterior nodal point that produces the same illuminance in the retinal image as does the extended source. This optical interpretation of trolands reveals that total light flux in the image of an extended object is the product of the troland value of the source and the solid angle subtended by the source at the first nodal point, independent of eye size.
... Invariant (EDOF) Displays. For HMDs, the analogue of a pinhole camera is a Maxwellian view: a point light source is focused on the viewer's pupil, with an amplitude SLM modulating a focused image on the retina [ Burns and Webb 2010]. Von Waldkirch et al. [2004] apply this principle to HMDs, showing a trade between DOF and resolution. ...
Conventional binocular head-mounted displays (HMDs) vary the stimulus to vergence with the information in the picture, while the stimulus to accommodation remains fixed at the apparent distance of the display, as created by the viewing optics. Sustained vergence-accommodation conflict (VAC) has been associated with visual discomfort, motivating numerous proposals for delivering near-correct accommodation cues. We introduce focal surface displays to meet this challenge, augmenting conventional HMDs with a phase-only spatial light modulator (SLM) placed between the display screen and viewing optics. This SLM acts as a dynamic freeform lens, shaping synthesized focal surfaces to conform to the virtual scene geometry. We introduce a framework to decompose target focal stacks and depth maps into one or more pairs of piecewise smooth focal surfaces and underlying display images. We build on recent developments in "optimized blending" to implement a multifocal display that allows the accurate depiction of occluding, semi-transparent, and reflective objects. Practical benefits over prior accommodation-supporting HMDs are demonstrated using a binocular focal surface display employing a liquid crystal on silicon (LCOS) phase SLM and an organic light-emitting diode (OLED) display.
