And you thought you’d seen everything? Well, you may have, but you probably haven’t been looking properly.
Research into the ‘non-visual’ aspects of lighting have been going on for a long time but the topic has been lifted out the strictly academic by the new lighting technology that’s become available through LED technology.
We’re used to the idea that we experience three visual states:
Photopic vision which is what we have during the day and in well-lit space. It’s what we'd all think of as usual light conditions. During the day, we are most sensitive to the green-yellow part of the light spectrum (at a frequency of 555nm)
Scotopic vision is what happens once it gets dark. We lose colour discernment and can generally only make out colours in the green-blue region. At night, our sensitivity slips towards the blue end of green (at a frequency: 498nm)
Mesopic vision sits uncomfortably between the two. Let’s call it dusk, when details start to disappear and we’re not quite sure what it is that we’re looking at.
Melanopic vision acknowledges that there is more going on than purely visual perception, there is also the biological impact of light. The hormone melatonin (hence 'melanopic') is the key to our pattern of wakefulness and sleep (our circadian rhythm). The production of this hormone is suppressed during the day by a naturally blue-rich light environment. We steadily fall asleep at night when there is very little blue in our light.
The spectral distribution at which melatonin is held at bay peaks at 464nm, which is a very strong blue. Manufacturers of LEDs are able to adjust the light output of their modules to take advantage of this, producing artificial light sources that help us to retain our attention to detail at times when we may otherwise be flagging. A lot of attention is being given to how melanopic lighting may assist shift workers to carry out their duties.
Blue saturation has been done before using fluorescent phosphors, but the result was often considered to be far too cold for many working environments. LED technology is providing much finer adjustment in the make-up of white light, enabling warmer tones to be created, combining the melanopic peak within the spectrum.
- Internet of Things-based lighting control, data capture and security will be a key theme of LuxLive 2017, which takes place on Wednesday 15 November and Thursday 16 November at ExCeL London. For more information, and to register for free, click here.
Picture courtesy Cormac Hanley/Monomondo Photography. Copyright 2016. All rights reserved.