LED lighting (Light emitting diodes) has gained popularity because it offers a wide range of benefits, including great energy efficiency, economic effectiveness, extended life, and design freedom. LED lights are present in many environments, including our homes, workplaces, and others. There is a “Dark” side to the “Bright” narrative, even if LED lighting is without a doubt the most significant and exciting development in the lighting industry.
Light output flickers continuously and comes in two flavors: visible and invisible. The naked eye may detect visible flicker that occurs within the frequency range of 100 hertz. The invisible flicker, which the human eye cannot detect over 100 hertz, is the one that we should all be concerned about.
How to detect invisible flicker is given here.
- Open the slow-motion video mode on your smartphone camera.
- Aim your finger at the LED light source.
- There will be a discernible distortion. The flicker that cannot be seen.
Knowing how invisible flicker affects the health and eyes of people
High flicker rates in LED lights can have a number of negative effects on health. Human eyes must quickly adapt to shifting light output due to flicker, which strains the eye muscles. According to studies, continuous exposure to the flicker that LED lights to create can cause eye strain, headaches, impaired vision, weariness, apparent slowing or stopping of motion, decreased performance on visual tasks, and in some cases neurological issues.
Why should we be worried about this issue?
Imagine the effects LED will have on our eyes and general health over time as we are exposed to artificial light for the majority of the 6,000 hours per year that we have our eyes open. If you work in an office, the LED lights installed there may be to blame for any headaches, eye strain, or vertigo you’ve had. In some industrial situations, LED flicker can cause problems with performance or even accidents.
Due to their constant exposure to LEDs in malls, homes, schools, and other public places, children are most vulnerable to these health risks. Children’s eyesight issues can result from spending a lot of time studying under LED lights with a lot of flickers.
Exists a safe threshold for flicker?
Even though numerous studies have shown flicker to be damaging to eye health, there is little awareness of this issue in India, and there are currently no laws governing the amount of flicker in LED lights. However, California’s threshold restriction of 30% has been established under IEEE standards PAR 1789. The flicker percentage of LED devices from various brands sold in India ranges from 40 to 80 percent, which is significantly higher than the recommended limit of 30%.
Characterizing Light Source and Flickers
All light sources operating on alternating current (AC) to modulate light output will inevitably create flickers from current fluctuations; fluorescent tubes, high-pressure sodium lights (HPS), and LED lights all to share the same luminous characteristic causing flickers along with current flow simultaneously. Direct current (DC) input through the power circuit became necessary to ensure the most comfortable lighting experience. Electricity frequency commonly runs at 50 Hz or 60 Hz, the flickering rate of a fluorescent tube is the multiplier of electricity frequency which is usually 120 Hz. Normally the flickers occurring at a frequency of over 100 flickers per second are unnoticeable unless the flickering is below 100 Hz; anything above 100 Hz could only be perceived through stroboscopic effects.
Stroboscopic Effects can be observed through several phenomenons, while the easiest way is by taking a direct shot at the light source, the result shows a distinctive ripple effect as per figure 1. The multiple shadows of a moving object are the presence of the Stroboscopic Effect. Stroboscopic effects may result in false interpretation of machinery with indistinctive slow motion or motionlessness while operating.
The simplest approach to examining stroboscopic effects is to take a direct shot at the light source, which produces a characteristic ripple effect as shown in figure 1. A moving object’s numerous shadows, as seen in figure 3, indicate the presence of the stroboscopic effect. Stroboscopic effects can lead to incorrect interpretations of moving or immobile machinery that is actually running.
Human reactions to flicker
Low-frequency flicker may cause seizures, and the magnetically ballasted fluorescent lights used in offices are also linked to headaches, weariness, visual blur, and vision impairment, according to the Solid-State Lighting Technology Fact Sheet (U.S. Department of Energy 2013). Even when driving at night, stroboscopic effects can create the illusion that moving objects are slowing down or stopping. Such an effect is also potentially dangerous in industrial settings, where it may raise issues with construction safety.
Children, autistic patients, migraine sufferers, and epileptic patients are some of the demographics that are more susceptible to the detrimental effects of flickers.
Analysis of flicker in lights that are available for purchase
We are aware of the major flickering issues with fluorescent tubes in general, but we are unsure if LED lights also suffer from this issue. The research below, carried out by the US PNNL, may provide us with an eye-opening perspective.
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