Assembly Blog


Beware the Blue Light

Bright blue LEDs may be the cause of eye strain, headaches and even sleep disruption.

June 24, 2013
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That bright blue LED light, found on many electronic devices, may be the cause of eye strain, headaches and even sleep disruption.

Blue light causes more trouble for the eye than other colors. That is because it is harder for the eye to focus blue sharply. Different wavelengths of light (i.e. different colors) have different refractive indexes as they pass through the eyeball to the retina. Our eyes can easily focus on fine details in red or green light.

But our retinas can’t handle blue light very well. Blue light scatters more widely within the eye and tends to be focused in front of the retina, making it appear slightly out of focus. What we notice is a kind of halo around bright blue lights. They also seem to produce more glare. So blue light can lead to eye strain and headaches as your eye muscles strain to bring fine details into focus.

The problem is compounded when the light source is an LED. Because of a difference in the manufacturing process, blue LEDs are different from other colors. They can be up to 20 times brighter than traditional red or green LEDs.

Blue lights are more noticeable in the dark or in dim light because the rods (a type of photoreceptor in the retina) are most sensitive to greenish-blue light. And since there are more rods in the outer edge of the retina, blue lights appear brighter in our peripheral vision in low-light conditions. That’s why a tiny blue LED can be so distracting in a dark room, even if it’s in your peripheral vision.

But beyond being a distraction, blue lights are known to affect our circadian rhythm and sleep patterns. Exposure to blue light suppresses the production of melatonin. Melatonin is known as the “sleep hormone” and is produced by the pineal gland, a pea-sized gland in the middle of your brain. You sleep when melatonin levels are high and awaken when melatonin drops.

Even a very low level of blue light, such as that produced by a single bright LED, can suppress melatonin levels, leading to wakefulness. This means anything with a blue LED in your bedroom has the potential of disrupting your sleep cycle. This can be the tiny blue light on your phone charger, the power button of your laptop, or accessories such as speaker lights. If this is the case, try unplugging the device, removing it to another room, or covering the LED so you can’t see the light. You may sleep better for it.


Delia Treaster, Ph.D., is a certified professional ergonomist and writes on various ergonomic issues, drawing on decades of experience in occupational ergonomics. She has been an ergonomic contractor with Humantech, one of the largest workplace ergonomics consulting firms in the United States. Prior to working for Humantech, Delia was an ergonomic consultant for the U.S. Postal Service, a senior ergonomic specialist with Travelers Insurance, and a research scientist at Battelle Memorial Institute. She has a master’s degree in human factors engineering and a Ph.D. in biomechanics from Ohio State University.

E-mails to Delia can be sent to ergocorner@yahoo.com.


Editor’s note: “Ergo Corner” is part of a series of guest spots by industry experts that will appear regularly on ASSEMBLY’s blog page. Check back frequently to read more commentaries from Delia, as well as contributions on product testing, automated assembly systems, electronics assembly and robotics.

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agreed!

David
June 27, 2013
Here is a direct, practical application of this issue. When I was working on my master's I had occasion to use a government agency library system to do some research on a paper I was writing for a class. The displays for the library holdings were old, low resolution and for some ungodly reason they had selected an intense, blue font for display of the search results. These were nearly unreadable, partly from pixelation due to the display resolution, but significantly exacerbated by the blue wavelength. The bottom line design lesson here is that some hues of blue should not be used in displays requiring text processing. However, the specific color dimensions are important. For example, cyan (a kind of de-saturated blue) is commonly used without issue in aviation displays and is easily legible.

makes sense

Martin
June 27, 2013
Makes perfect sense from an evolutionary point of view: Why should an organism develop skills to capture sharp imagery of the blue sky?

old displays were bad

Stephen
June 27, 2013
I remember the old dot-matrix graphics in green or tan mostly against a black background. The blues they used back in the day were not bright enough, IMO. Who uses actual blue today?

watch color combinations

Alan
June 27, 2013
The implications of this inability to focus blue well extend beyond the use of pure blue in displays: it means that the eye cannot easily discern edges where the only difference in colour is the amount of blue. So, for example, it is hard to read text in cyan on a green background, or magenta on red.

it's about wavelength

Bob
June 27, 2013
More accurately, in terms of the progressive wavelength, as the color approaches ultraviolet, it become physiologically more difficult to focus on. Cyan isn't desaturated blue, it is simply closer to the 'green' end of the spectrum and therefor easier to focus on. Saturation is a measurement of the intensity of a specific color hue whereas Cyan is a specific hue (wavelength) or hue range.

contrast makes a difference

Stephen
June 28, 2013
The contrast against the background makes a difference. Sometimes I revise manuscripts using different colors of type. I've noticed that microsoft-blue stands out more from both the white and surrounding black text than red or green, although all three are not mistakable to me.

watch adjacent colors

Bob
June 28, 2013
@Alan, the issue you bring up is different albeit important as well. Edge recognition between two colors that are close in hue and brightness can be difficult to see from the perspective of differentiation of color. However, the blue light issue happens regardless of the color that is next to it. It is a physiological issue of the ability to progressively have difficulty focusing on wavelengths that approach the ultraviolet end of the spectrum when the wavelength is also a more pure hue. This can't be controlled by adjacent color use. The issue you address is a specific function of choice of adjacent colors

interesting application

Stephen
July 3, 2013
Another practical application: In The Netherlands, they use blue light in the toilets of night clubs and other venues to make it more difficult for addicts to shoot up.

control room impact?

John
July 3, 2013
I am particularly interested in 'blue light' and its impact on control room operators. The international standard, ISO 11064, on control room ergonomics does not deal with this factor. Has anyone come across any work on 'blue light' and its impact on control room staff?

biodynamic lighting

Martin
July 3, 2013
I have designed several truly biodynamic lighting systems aimed at the circadian rhythm phase shift. These systems have improved vigilance and alertness, as well as enabling shift operators to sleep after leaving work. Understanding on this issue has progressed significantly over recent years. Control technologies have also improved, resulting in significant reductions in installation costs and complexities. In the early days, commissioning was often a challenge. Today, it’s virtually plug-and-play, if designed correctly. The short and long term health consequences of circadian rhythm disruption are now well-established. A recent study has concluded that red light is also effective in improving vigilance and alertness, especially in the afternoon dip. Detailed knowledge and experience is critical to ensuring success, as there are significant potential pitfalls.

clarification

Bob
July 3, 2013
I should reiterate (or perhaps clarify) that the disruptive aspect of blue light in terms of human vision is specifically more severe as (either or both) the light is more pure in it's wavelength (less 'white'). The higher the wavelength is as it approaches ultraviolet (<440 nm), visual acuity in terms of focus begins to recede below the 500-480 nm range, assuming that the light color is fairly pure.

Blue light and aging

Brandon
July 9, 2013
And, from an accessibility standpoint.... if I understand the research correctly, sensitivity to blue light also diminishes with age. More specifically, the increasing presence of yellow-ish cataracts filters light in the blue range. To those individuals, this will cause blue light to look relatively dimmer. In contrast, green-yellow light is not subject to this effect and may look equally bright to all ages.

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