From dizziness to underexposed photos, strobes have an impact in many ways. Solid-state lighting SSL has been recognized by the lighting industry as a high-efficiency light source for today and in the future, but it still lacks the issue of stroboscopic LEDs that cause periodic adjustments. If left unresolved, strobe will cause a lot of problems, which will damage the well-designed lighting and lighting space. Understanding the basics behind stroboscopic issues will help architects and lighting professionals avoid the annoying and even harmful effects of strobes.
What is strobe?
With regard to stroboscopic, the simplest definition is the constant fluctuation of light during the switching period. In the United States, current is transmitted through an alternating current of 60 Hz, and the supply voltage of the luminaire fluctuates back and forth between peaks and troughs in the form of a sine wave during the switching period. Therefore, it is possible to generate a strobe twice the power supply frequency, that is, 120 Hz. If there is no suitable electronic circuit, such as a ballast, drive or power supply, the source will strobe. Some strobes are intentional, such as bicycle headlights. "Some strobes don't attract attention and there is no physical discomfort. But some strobes are really a problem," senior scientist and lighting design at the Pacific PNNL (Pacific Northwest National Laboratory) Advanced Lighting Group. Naomi Millier said, "The lighting industry is concerned with stroboscopic range that can cause nervous system problems and affect job performance."
Nadarajah Narendran, research director at the LRC (Lighting Research Center) in New York, said: "Humans can detect strobes below 50 Hz, and of course some people will notice it at 100 Hz." A low frequency flash of about 3 to 70 Hz may cause seizures in high-sensitivity people, and a moderate strobe between about 100 and 500 Hz may cause indirect perception of stroboscopic effects. In this case, a dynamic object may appear as a series of still images. This effect may be the effect that the ballroom hopes to achieve, but it is dangerous for industrial sites. For example, strobo can make moving gears or blades look slow, even static, and it can also have a series of adverse effects on health, such as headaches, eye strain and physical and mental fatigue.
Figure: The stroboscopic effect causes moving objects to appear to be stationary or to move more slowly.
Jim Benya, head of Benya Burnett Consultancy in California, said that as the flashing frequency steps into the kilohertz range, up to 2 kilohertz or more, preliminary research shows that "we don't feel it, strobo is no longer a problem." However, how to get different light sources to achieve such high flicker frequency may be a problem.
Strobe measurement
Currently, there is no official standard process to guide manufacturers in stroboscopic testing, but IES (Illuminating Engineering Society) has developed two methods to measure stroboscopicity, which can be found in RP-16-10 Lighting Engineering Terms and Definitions. The first and more commonly used measurement method is the strobo ratio. It shows the average amount of adjustment of the light output over a switching cycle, which is the amount of reduction. A 100% stroboscopic light source means that it does not illuminate at certain times during the switching cycle, while a fully stable source is 0% strobed.
Another measurement method is the stroboscopic index, which ranges from 0 to 1. It combines the strobe ratio with two other variables: the light waveform (output curve) and the duty cycle. The duty cycle is the percentage of the light-on time that the light source has in a single switching cycle. The lower the stroboscopic ratio and the stroboscopic index, the less the source flickers or the visible stroboscopic effect.
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