Christmas presents with an alternative use – the fidget spinner
Posted on 11/12/2018
At a recent Lighting Liaison Group (LLG) meeting, Arnold Wilkens, Emeritus Professor at the University of Essex who has conducted extensive research into the biological effects of lighting and visual discomfort, raised the issue of flicker in LED lighting. A humble fidget spinner could provide the answer to checking out whether an LED bulb is flickering or not.
It’s been shown that flicker can cause irritation, but it was generally assumed that if you can’t see the flicker, it’s not a problem. However, recent research shows that flicker can be bad for you even if you can’t see it. To understand, a quick look at saccadic eye movements is needed.
When we look at a scene our eyes are not fixed in position but make a series of rapid movements known as saccades. Saccades, or saccadic eye movements, are very fast jumps from one eye position to another. But because saccades are so very fast, it may be difficult to see the eye movements as discrete jumps. During natural viewing we make two to three saccades every second.
High-speed flicker is not consciously visible but the interaction between flicker and fast saccades can cause the high-speed flicker to be visible. It was commonly believed that vision was impaired during saccadic eye movements, but this may not be the whole story. It seems that some of the known detrimental effects of flicker are probably due to the brain being available to perceive during saccades.
Flicker problems from fluorescent tubes at 120Hz were known to be an issue, but LEDs operate on a difference principle that, in theory, means flicker should not be an issue. LED bulbs are increasingly being used in domestic and commercial environments. Whilst the LED itself is rarely a problem, the electronic circuitry in the base of the bulb can be if it’s not designed well as it may cause the bulb to flicker at a very high rate. There’s no way of telling if the bulb will flicker by looking at the packet. Expensive equipment will provide an answer, but a cheaper and more easily available way is to use a fidget spinner. Spin up the spinner and arrange it so that the light shines on it; if the bulb is flickering you will see a stationery or slowly moving pattern on the spinner and if there is no flicker then the light will evenly illuminate the spinner.
Professor Wilkens is calling for LED lamps to be labelled with a health code so that consumers can made educated choices when buying bulbs. You can view his TedX talk about how modern life is disturbing our vision and how to reduce the strain here.