Coding Horror

programming and human factors

Blue LED Backlash

I recently purchased the DGL-4300 wireless router, mainly because it includes gigabit ethernet, which is still quite rare in routers. It certainly looks cool, as routers go, with its sleek rubbery design and all-blue LEDs. But those blue LEDs-- particularly a bank of them, all blinking away-- are blindingly bright! They're actually painful to look at, which is sort of ironic considering they are status and activity LEDs.

Evidently, this is a known issue with blue LEDs:

Blue LEDs really are brighter than their old-fashioned red and green counterparts. Barney O'Meara, vice president of Canadian LED manufacturer The Fox Group, said blue LEDs have at least 20 times the luminous intensity of old-fashioned red and green indicators. O'Meara said his company has developed technology to manufacture low-intensity blue LEDs.

"Blue tends to cause more discomfort and disability glare than other, longer wavelengths," said Dr. David Sliney, an expert on the harmful effects of bright light sources at the U.S. Army Center for Health Promotion and Preventive Medicine in Maryland. Sliney said the eye's lens cannot focus sharply on the blue lights. While red or green light is focused precisely onto the retina, blue light is focused slightly in front of it, which causes a distracting halo around bright blue lights.

In addition, blue scatters more widely than other colors as it passes through the eyeball, Sliney said. Together, these two effects cause the intense blue light from a point source, like an LED, to spread out across the retina, interfering with other parts of the scene. It's called dispersion: Blue's shorter wavelength makes it refract at a greater angle than, say, red or green.

Also, human vision becomes far more sensitive to blue when ambient light levels are low, a phenomenon known as the Purkinje shift. So a blue light that is merely eye-catching on a brightly lit store shelf can become dazzling when the lights are low, such as when watching a movie on a laptop in a dimly lit room.

Some researchers report that, at night, even low-level blue light may be enough to trigger recently discovered receptors in the retina that can depress melatonin production, disrupt sleep patterns and suppress the immune system.

If there's a bright blue LED in your field of view, your only recourse may be "painting" it with a permanent black magic marker. My room is dimly lit now, and if I glance over to the router, it's like getting tiny little blue LED punji sticks right in the eye. And I wear glasses, which doesn't help, either. Blue LEDs may look cool, but for actual functional use, give me green or red LEDs any day.

Blue LEDs weren't even commercially viable until the mid 1990's, largely thanks to the research of one Shuji Nakamura:

I kept at it, but I was dispirited. For ten years I had worked very hard to make these products. I worked twelve hours a day, seven days a week, except holidays. I had a very, very small budget and had to make everything I needed myself. I even made my own reactors -- the furnaces needed to do the crystal work. The commercial reactors were too expensive. I made three products all by myself, and still my salary and position were not good at the company. My bosses always complained that my results were terrible, because I spent a lot of money, as far as they were concerned, and nothing sold. But for ten years I had been working to make these LED materials and I knew at the time there were no high-brightness blue LEDs. For LED researchers, this was a dream. But my bosses said it would be impossible to create a blue LED at Nichia, because many big companies and many research teams in big universities were trying to do it and were failing.

Except for the blue LED problem, I give the DGL-4300 router a big thumbs up. The Quality of Service (QoS) feature they call "GamerFuel" really works. I can download stuff in BitTorrent while playing Battlefield 2 with hardly any impact on my ping in the game.

Written by Jeff Atwood
