![]() LED manufacturers can use this model to test their products. Researchers from Southeast University in China repeated the experiments to exclude cultural differences.īased on the thresholds found for each combination of the tested parameters, Perz developed an open source model quantifying the visibility of the stroboscopic effect of any light waveform. The subjects indicated whether or not they observed a stroboscopic effect for each change. During the experiments, Perz manipulated different lighting parameters the frequency, the amplitude or the modulation depth and the shape of the wave. The disk rotated at a constant speed of 4 meters per second, similar to fast hand gestures in an office environment. ![]() She invited more than 200 persons, in a simulated office environment, to look at a black disk with a white dot under a LED light source. Perz searched for the exact value of specific light characteristics at which the stroboscopic effect becomes invisible to the human eye the visibility threshold. In short what you don’t see, won’t affect you.” She adds: “Manufacturers want to know what people do and do not perceive, so they can make informed choices when designing their drivers.” Research in this area indicates that exposure to fluctuating light induces biological responses, possibly affecting health, only when the flicker or the stroboscopic effect are visible. Perz: “It’s important to determine when stroboscopic light is still perceptible to people. In its extreme form this effect is often used in discotheques.” The human eye does perceive this effect and it can influence our perception of lighting quality, leading to annoyance and irritation, but also headaches. ![]() Perz: “This effect is visible as a series of still images when fluctuating light illuminates a moving object. “As a result, different designs of drivers can lead to varied levels of unwanted effects in the emitted light of LEDs,” says Perz.įlickering is immediately visible, but the so-called stroboscopic effect is more difficult to observe if you don’t know what to look for. However, this requires a trade-off with other features of drivers, such as cost, size, reliability or efficiency. This driver can reduce the current fluctuations to prevent the visibility of side effects. “Incandescent lamps need to become hot in order to emit light, and since the thermal processes are rather slow, we can’t see that the light is fluctuating,” explains Gosia Perz, “But the reaction of LEDs to the driving current is very fast, almost instantaneous, which can lead to visible side effects caused by fluctuating light.” Most LEDs are not operated directly from the mains, but they contain a piece of electronics - a driver - that regulates the current flowing through a LED. The electricity that we use in Europe when plugging different home appliances, televisions and lamps into wall sockets is alternating-current (AC) power supply that changes at 50 cycles per second (50 Hertz). Gosia Perz was awarded a PhD for this research at TU/e on February 5 th , with distinction. The model developed allows lighting manufacturers to test for these undesirable effects while designing their LED products. Researchers at Eindhoven University of Technology and Signify determined the characteristics of light at which the human eye no longer perceives these unwanted effects. Light emitted by LEDs can flicker or exhibit a stroboscopic effect, which can lead to annoyance, fatigue and even headaches.
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