Is it time for Human Centric Sensing?

Office lighting has for some time often included sensors built into the space, designed to manage the energy efficiency of the rooms. At the simplest level, these intervene by turning off the light when you aren’t there (and sometimes when you are!) and more recently to adjust the level of lighting to do what is known as ‘daylight harvesting’ – limiting artificial light to what is needed to make up for any lack of natural light available.

While this sensing is often still patchy and poorly executed, it is fairly well established, standard approaches are understood, and usage conventions becoming established. We have learned, for example, that if the lights go out when we are sitting quietly in the room, we need to wave our arms or move to be in range of the sensor.

But increasingly, there is an understanding of the importance of light for our very well-being, from early simple discoveries in combating Seasonal Affective Disorder to now a much deeper understanding of the retinal ganglion cells that manage our physiological response to light. So maybe by now, we shouldn’t just be sensing the energy characteristic of light but a wider array of factors that would allow us to better adjust and control the lighting delivery to be good for us, not just mechanically efficient.

We can, of course, reuse the sensors we have – knowing how bright a light is and whether someone is present is better than not having that information. But as a rule, energy management systems just look straight down from a light (or near a light) and measure what is bounced straight back to it. For energy conservation, knowing if someone is there is enough; little more information is needed to decide whether a light is needed or not. Some sensors even only look into the light itself, unconcerned by the result – just directly checking the performance of the output.

Other factors become important for human quality of light, a key one being the Colour Temperature or, more ideally, spectrum of the resulting lighting. At certain key times of the day, and for certain periods your body needs to be stimulated by ‘daylight-like light into producing (or not producing!) the hormones that manage your sleep-wake cycle….and this cycle’s influence also extends to many other aspects of your physiology such as digestion, cognitive performance etc. Depending on what you are doing and when you are doing it, you may also want to more subtly adjust these factors to aid concentration, adjust body-clocks or give a greater sensory acuity.

For this, looking down at the top of your head is not ideal, not least because the angle of incidence of the light is also important – different sections of your eye do different jobs and where the light comes from does matter. Light sensors for Human Centric Lighting need to be where humans are (most of the time), not observing obliquely from afar. Interestingly, if we achieve this, we are also likely to make better judgements about how intensity adjustments can reduce the energy requirements, as the intensity of lighting is also a key factor in the human need and the efficiency level.

One, not unreasonable, suggestion has been that we (almost) all carry sophisticated human-centric sensing around with us all the time in the form of our smartphones. However, while there is lots of interesting data available from these (and other) devices that could inform a better lighting experience, the reality is that you cannot really rely on it. Sensing can be compromised by how it is being used for other tasks…..some of the time, the sensor is being held against your head or resting on the desk, depending on how you take a call….It may be tucked in a pocket or a bag where it can’t see the light; at another moment, it may be playing a game while sitting in a completely different room (!) or lying on a desk face down while the owner wanders to the kitchen. So, while there is a lot of interesting potential, perhaps this ‘sensor’ is also busy being too many other things as well.

Therefore, maybe it is time to provide sensing dedicated to the quality of lighting for our well-being and activity, just as we already do to manage our energy use and even extend that to our much wider well-being (temperature, humidity, air quality). This enhanced sensing needs to be at the human-level quite literally. Wireless technologies untether the sensors from the ceiling or wall, so now is the opportunity for the ubiquitous Human Centric Lighting sensor that sits where you do and literally looks out for you.