Detection of the stroboscopic effect by young adults varying in sensitivity

The advent of LED lighting has renewed concern about the possible visual, neurobiological, and performance and cognition effects of cyclic variations in lighting system luminous flux (temporal light modulation). The stroboscopic visibility measure (SVM) characterises the temporal light modulation signal to predict the visibility of the stroboscopic effect, one of the visual perception effects of temporal light modulation. A SVM of 1 means that the average person would detect the phenomenon 50% of the time. There is little published data describing the population sensitivity to the stroboscopic effect in relation to the SVM, and none focusing on people subject to visual stress. This experiment, conducted in parallel in Canada and France, examined stroboscopic detection for horizontal and vertical moving targets when viewed under commercially available lamps varying in SVM conditions (SVM: ∼0; ∼0.4; ∼0.9; ∼1.4; ∼3.0). As expected, stroboscopic detection scores increased with increasing SVM. For the horizontal task, average scores were lower than the expected 4/8 at ∼0.90, but increased non-linearly with higher SVMs. Stroboscopic detection scores did not differ between people low and high in pattern glare sensitivity, but people in the high-pattern glare sensitivity group reported greater annoyance in the SVM ∼1.4 and ∼3.0 conditions

Flicker Explained : guide to IEC for the lighting industry

Flicker, or more precisely temporal light modulation (TLM), has re-emerged as a problem with the introduction of LED-based lighting technology. TLM, meaning variations in light intensity over time, may have negative effects on human health, causing annoyance, headaches, eyestrain and migraine. In addition to the unnecessary suffering TLM causes in individuals, the negative consequences of TLM create an obstacle to broad and rapid adaptation of the new LED-technology and consequently also an obstacle to potential energy savings.This guide gives an introduction to TLM, what it is and how it is measured. The effect of TLM on health is concluded, and also the state of knowledge in its research area. An extended part of this guide discusses the flicker measure short-term flicker indicator, Pst, and the technical report describing it, TR IEC 61547-1:2020 (henceforth referred to as IEC 61547, unless otherwise stated). This report describes the equipment, method and measures required to assess flicker. It is, however, technically complicated and could be very hard to interpret by non-technical readers. For a more detailed investigation and recommended amendments of the IEC 61547, see “Flicker explained – Interpretation of the Technical Report IEC 61547“ which is another product of the project Flicker Explained. For a general guide on TLM measurements, please consult the technical note published by International Commission on Illumination, CIE TN 012:2012

Flicker – a technological overview

Flicker can be annoying, but above all it can have a negative effect on human health; causing irritation, headaches, eye strain and migraines. With the introduction of LED lamps, flicker has once again become a problem. In addition to the unnecessary suffering caused to individuals, the negative consequences create an obstacle to the wide and rapid adoption of new LED technology and thus also an obstacle to potential energy savings.The EU’s new eco-design regulations entered into force in September 2021. These include, for the first time (in Europe) regulatory limits for flicker, creating an urgent need to disseminate knowledge about flicker and how to measure it

Light-Emitting Diodes (LEDS): implications for safety

Since the original ICNIRP Statement was published in 2000, there have been significant improvements in the efficiency and radiance (i.e., optical radiation emission) of LEDs. The most important improvement is the development of 'white' LEDs that can be used as general lighting sources, which are more efficient than traditional lighting sources. LEDs emitting in the ultraviolet wavelength region have also become available and have made their way into consumer products. All these changes have led to a rise in concern for the safety of the optical radiation emissions from LEDs. Several in vitro and animal studies have been conducted, which indicate that blue and white LEDs can potentially cause retinal cell damage under high irradiance and lengthy exposure conditions. However, these studies cannot be directly extrapolated to normal exposure conditions for humans, and equivalent effects can also be caused by the optical radiation from other light sources under extreme exposure conditions. Acute damage to the human retina from typical exposure to blue or white LEDs has not been demonstrated. Concern for potential long-term effects, e.g. age-related macular degeneration (AMD), remains based on epidemiological studies indicating a link between high levels of exposure to sunlight and AMD. When evaluating the optical radiation safety of LEDs, it has now been established that published safety standards for lamps, not lasers, should be applied. Thus far, the only clear, acute adverse health effects from LEDs are those due to temporal light modulation (including flicker). Glare can also create visual disturbances when LED light fixtures are not properly designed. Further research is needed on potential health effects from short- and long-term exposure to new and emerging lighting technologies

Light-emitting diodes (LEDS): Implications for safety

Since the original ICNIRP Statement was published in 2000, there have been significant improvements in the efficiency and radiance (i.e., optical radiation emission) of LEDs. The most important improvement is the development of 'white' LEDs that can be used as general lighting sources, which are more efficient than traditional lighting sources. LEDs emitting in the ultraviolet wavelength region have also become available and have made their way into consumer products. All these changes have led to a rise in concern for the safety of the optical radiation emissions from LEDs. Several in vitro and animal studies have been conducted, which indicate that blue and white LEDs can potentially cause retinal cell damage under high irradiance and lengthy exposure conditions. However, these studies cannot be directly extrapolated to normal exposure conditions for humans, and equivalent effects can also be caused by the optical radiation from other light sources under extreme exposure conditions. Acute damage to the human retina from typical exposure to blue or white LEDs has not been demonstrated. Concern for potential long-term effects, e.g. age-related macular degeneration (AMD), remains based on epidemiological studies indicating a link between high levels of exposure to sunlight and AMD. When evaluating the optical radiation safety of LEDs, it has now been established that published safety standards for lamps, not lasers, should be applied. Thus far, the only clear, acute adverse health effects from LEDs are those due to temporal light modulation (including flicker). Glare can also create visual disturbances when LED light fixtures are not properly designed. Further research is needed on potential health effects from short- and long-term exposure to new and emerging lighting technologies

Auswertung der zeitlichen Lichtmodulation unter Verwendung von bildauflösenden Messgeräten

Reale Lichtszenen weisen oft eine Kombination aus verschiedenen Lichtquellen und auch Tageslicht auf. Die herkömmliche Messmethode erfordert für eine solche Szene mehrere Einzelmessungen mit einem Leuchtdichtephotometer (als Spot-TLMMessgerät) oder einem nah an der Lichtquelle platzierten Beleuchtungsstärke-Photometer. Diese Szenen können aber auch mit Hochgeschwindigkeitskameras oder bildgebende Leuchtdichtemessgeräten (engl. Imaging luminance measurement devices, ILMD) in einer Messung aufgenommen und ausgewertet werden. Ein derartiges Messverfahren beschreibt damit eine Alternative zur gängigen Methode und wird in diesem Beitrag anhand von gängigen Lampentypen demonstriert. Aus den Aufnahmen werden die Metriken zur zeitlichen Lichtmodulation (engl. temporal light modulation, TLM) berechnet, dabei werden die Parameter der einzelnen und der überlagerten Lichtquellen extrahiert und bewertet. Ein wesentlicher Vorteil der Aufnahme einer gesamten Szene ist es, dass auch die räumliche Verteilung der TLM betrachtet und in der Bewertung berücksichtig werden kann. In dieser Arbeit werden die Möglichkeiten und die Grenzen der bildgebenden TLM-Messung anhand von unter Laborbedingungen erstellten Beispiele aufgezeigt

All-optical modulator based on a microfibre coil resonator functionalized with MXene

A novel all-optical modulator based on a microfibre coil resonator (MCR) functionalized using MXene is reported. The MCR was manufactured by winding a tapered fibre on a polycarbonate (PC) resin cylinder with low refractive index to support the microfibre, which also forms a fluidic channel coil. The MXene dispersion was injected into the channel to allow the deposition of an MXene layer using a photodeposition process. The transmission spectra were tuned using a tunable laser with a centre wavelength of 1550 nm and the light-matter interaction resulting from the photo-thermal effect and MXene absorption provide the all-optical modulation in this device. The variation of the resonance wavelength, phase shift and extinction ratio of transmission spectrum versus power were determined as 50 pm/mW, 0.262 π/mW and 0.554 dBm/mW respectively. The all-optical modulation properties were further characterized using a lens coupling method and adding a chopper to provide a controlled light source. The rise and fall response times for waveforms of the light signal were 0.179 and 0.145 ms, respectively. The intensity and width of the light signal waveform was modulated using the chopper-controlled light source, which indicates that MXene, as a new two-dimensional material, has excellent nonlinear optical effects and the MXene-MCR has the potential for use in ultra-fast optical nonlinear optical processing. The MXene-MCR has several superior characteristics compared with other all-optical modulators including excellent modulation properties, all-fibre construction, easy fabrication and fast response. These advantages demonstrate MXene-MCR has excellent potential for use as a tunable optical filter, an optical switch as well as an all-optical modulator