Search Results (7)

Melanopsin contribution to visual and non-visual effect has drawn widespread concern. However, research about whether this contribution can be applied to display system design is limited. Here, a four-primary display system was designed and constructed based on three projectors with filters to realize isolation control of melanopsin and cones, and a 65-inch uniform display area was achieved. The melanopic luminance metamers (higher and lower) of different colours have been modulated thusly. The effect of melanopic luminance on pupillary light reflex (PLR) and brightness perception was explored under a luminous environment of 300 lx to ensure the saturation of rod. The results showed that the higher melanopic luminance level contributed to delayed contraction maintenance. Moreover, a log relationship was found between melanopic equivalent daylight luminance and pupillary contraction maintenance parameters with coefficient of determination more than 0.85. Furthermore, stimuli of higher melanopic luminance level appeared brighter, indicating that melanopsin contributed to brightness perception. Full article

The pupillary light reflex, which has been seen as an important noninvasive and objective indicator of autonomic nervous system function, can be used for evaluating the impact of different lighting conditions in buildings on circadian behaviors, assessing ipRGC function in healthy and diseased retinas, and explaining luminance adaptation. However, the mechanism by which the intrinsic and extrinsic signals of ipRGCs regulate the steady-state pupil size under continuous lighting stimuli is still not clearly understood after decades of exploration. This paper presents a new experimental protocol with a large hemisphere LED screen as the stimulation device, allowing for a more realistic and comprehensive study in architectural spaces, which can potentially inform the design of lighting systems in buildings that promote healthy vision and comfort. Results reveal that both intrinsic and extrinsic signals participated in the process of regulating pupil size under continuous lighting conditions. Based on the findings, a new mathematical model was further proposed to calculate the contribution of these two signal sources to the changing intensity of melanopic radiance. The research outcomes also provide new insight into the mechanism of visual perception and adaptation and the nonvisual effect of eyes under different light conditions. Results suggest that the contribution of extrinsic signals may have been underestimated in previous studies since the extrinsic signal increases with reducing intensity in photopic conditions with lower melanopic radiance. Full article

Introduction: In 2009, the World Health Organization identified vehicle crashes, both injury-related and fatal, as a public health hazard. Roadway lighting has long been used to reduce crashes and improve the safety of all road users. Ocular light exposure at night can suppress melatonin levels in humans. At sufficient light levels, all visible light wavelengths can elicit this response, but melatonin suppression is maximally sensitive to visible short wavelength light. With the conversion of roadway lighting to solid state sources that have a greater short wavelength spectrum than traditional sources, there is a potential negative health impact through suppressed melatonin levels to roadway users and those living close to the roadway. This paper presents data on the impact of outdoor roadway lighting on salivary melatonin in three cohorts of participants: drivers, pedestrians, and those experiencing light trespass in their homes. Methods: In an outdoor naturalistic roadway environment, healthy participants (N = 29) each being assigned to a cohort of either pedestrian, driver, or light trespass experiment, were exposed to five different solid state light sources with differing spectral emissions and one no lighting condition. Salivary melatonin measurements were made under an average roadway luminance of 1.0 cd/m² (IES RP-18 Roadway Lighting Requirements for expressway roads) with a corneal melanopic Equivalent Daylight Illuminances (EDI) ranging from 0.22 to 0.86 lux. Results: The results indicate that compared to the no roadway lighting condition, the roadway light source spectral content did not significantly impact salivary melatonin levels in the participants in any of the cohorts. Conclusions: These data show that recommended levels of street lighting for expressway roads do not elicit an acute suppression of salivary melatonin and suggest that the health benefit of roadway lighting for traffic safety is not compromised by an acute effect on salivary melatonin. Full article

The evaluation of both visual and nonvisual effects from the spectral power distribution (SPD) of outdoor light is critical in lighting design. The dome-light SPD characteristically changes continuously depending on the seasonality, orientation, altitude of the sun or hour of the day. Traditional photopic parameters, such as the illuminance, luminance or correlated colour temperature (CCT), have been widely studied, but presently, there is no melanopic measurement or evaluation method. This article discusses the processes involved in establishing a simple method to determine the SPD of daylight and solar radiation over the skydome in a location to accurately account for the effects of both photopic and circadian levels around a location. Once per month for one year, natural daylight was spectrally measured in the city of Zaragoza (Spain); radiometric and photometric characteristics were analysed by season; and circadian effects were calculated in terms of standard parameters described by the Commission International de l’Eclairage (CIE), factors recommended by normative and scientific backgrounds. Finally, we suggest that the best parameter is the melanopic versus photopic irradiance ratio, which achieves reliable results at simplifying and correlating calculations. Full article

Modern indoor lighting faces the challenge of finding an appropriate balance between energy consumption, legal requirements, visual performance, and the circadian effectiveness of a spectrum. Multi-channel LED luminaires have the option of keeping image-forming metrics steady while varying the melanopic radiance through metamer spectra for non-visual purposes. Here, we propose the theoretical concept of an automated smart lighting system that is designed to satisfy the user’s visual preference through neural networks while triggering the non-visual pathway via metamers. To quantify the melanopic limits of metamers at a steady chromaticity point, we have used 561 chromaticity coordinates along the Planckian locus (2700 K to 7443 K, ±Duv 0 to 0.048) as optimisation targets and generated the spectra by using a 6-channel, 8-channel, and 11-channel LED combination at three different luminance levels. We have found that in a best-case scenario, the melanopic radiance can be varied up to 65% while keeping the chromaticity coordinates constant $\left(\Delta u^{\prime }{v}^{\prime }\le 7.05\times {10}^{-5}\right)$ by using metamer spectra. The highest melanopic metamer contrast can be reached near the Planckian locus between 3292 and 4717 K within a Duv range of −0.009 to 0.006. Additionally, we publish over 1.2 million optimised spectra generated by multichannel LED luminaires as an open-source dataset along with this work. Full article

In this work, we investigated the luminous and melanopic efficiency of the radiation (LER/MER) performances of phosphor-converted LEDs (PC LEDs) with tunable spectral characteristics, namely peak wavelength, full width at half maximum (FWHM), and emission intensity. We constructed theoretical PC LED spectra based on the characteristics extracted from the database of IES TM-30-15, analyzed the relations between LER/MER and different spectral characteristics, and proposed spectral composition strategies at various correlated color temperatures (CCTs). Results showed that both MER and LER are linear with the FWHM of phosphor within the peak wavelength range in practical use, but the change in values by tuning emission intensity varies with spectral compositions. Hence, different spectral characteristics should be considered comprehensively. We further explored the trade-off between luminous and melanopic efficiency. Lowering the FWHM of phosphor and the intensity distribution of the blue LED can obtain higher LER and low circadian effect at lower CCT. As CCT increases, considering color rendering and the increase in the blue intensity distribution, besides reducing FWHM, tuning the peak wavelength close to the peak wavelength of V(λ) helps to reduce the circadian effect. These investigations provide optimization strategies for ideal melanopic and luminous performance of PC LED light sources. Full article

Big lighting data are required for evaluation of lighting performance and impacts on human beings, environment, and ecology for smart urban lighting. However, traditional approaches of measuring road lighting cannot achieve this aim. We propose a rule-of-thumb model approach based on some feature points to reconstruct road lighting in urban areas. We validated the reconstructed illuminance with both software simulated and real road lighting scenes, and the average error is between 6 and 19%. This precision is acceptable in practical applications. Using this approach, we reconstructed the illuminance of three real road lighting environments in a block and further estimated the mesopic luminance and melanopic illuminance performance. In the future, by virtue of Geographic Information System technology, the approach may provide big lighting data for evaluation and analysis, and help build smarter urban lighting. Full article