LpR Article | Jul 04, 2016

Human-Centric Lighting: Sensor Technology for Full- Spectrum Lighting Solutions by ams

While not necessarily common knowledge, research is rapidly validating the common-sense understanding that human beings are “tuned” to the natural lighting cycles of the sun, and can be equally “de-tuned”, to the detriment of both health and productivity, by artificial light sources that operate contrary to these natural flows. Sajol Ghoshal, Director of Sensor Driven Lighting at the Opto Sensor and Lighting BU at ams, discusses the available approaches for full-spectrum solutions, and potential humancentric benefits, of fully integrated intelligent ambient/color light sensor and driver technology.

Decades ago, the need for both energy savings, and increased lamp longevity, drove commercial lighting away from the more “natural” incandescent lighting. While the primary substitute, fluorescent technologies, continued to improve on efficiencies and color quality over its 50+ year history, with the introduction of high-efficiency T5 luminaires, progress has effectively plateaued in both areas. With the advent of LED-based lighting, an entirely new palette of precision spectral and color-quality capabilities has been presented to researchers, luminaire engineers and lighting designers alike. These capabilities are the harbinger of a new era of “human-centric” illumination, that will be enabled by cognitive lighting, that will soon be working at an elemental level to increase health, well-being and productivity of people everywhere.

Common light sources, including daylighting, have dramatically different energy spectrums allowing ambient/color sensors the ability to distinguish between these different spectra and determine the actual amount of ambient light available, as well as the quality of the light on a quantitative basis. When combined with precision control of the LED lighting with white color tuning, a fully-integrated, fully-intelligent cognitive lighting system can provide not only provide human-centric lighting, but can additionally realize higher efficiencies by focusing directly on the kind of light needed. By way of example, later afternoon sunlight may still be in ample supply in the interior of the building, but the warmer color temperature of the light may not readily support the same visual acuity as the mid-day sun. The option can then be incorporated to allow delivery of electric lighting strictly concentrated in the cooler color temperature region, with substantially lower luminous flux and overall energy savings compared to continuous full-spectrum solution.


Whether it is due to escalating insurance rates driven by rising health care costs, deeper recognition of the true value of maintaining and retaining skilled workers, or continually growing productivity demands, businesses are placing a new emphasis on the health and well-being of their employees. Up to this point in time, that emphasis has resulted in traditionally understood lifestyle “touch-points” including exercise, wellness exams, management of individual risk factors, or work-scheduling approaches for shift workers.

It has long been understood that poor lighting is not only associated with an adverse environment, as we all relate to the mental image of the “dark dungeon” or “dimly lit alley”, but that there is a cause and effect relationship with human health. The most prominent example is season affective disorder syndrome, or SADS, which is a winter-season depression that effects sensitive individuals in the higher latitudes where the day/night cycle is more extreme, right up to the Arctic or Antarctic circles, where there will be winter days when the sun will literally fail to rise fully above the horizon. Experimentation with “light therapy” proved effective in extreme cases, adding momentum to a new realm of studies of the interaction between light and humans.

While something like SADS, or traditional jet lag provides a backdrop for the effect of day/night cycles on mood or restorative rest, a new body of evidence is clearly pointing to more subtle interactions between humans and their lit environment. While the detailed results are best left to the medical and behavioral journals, as always, technology will be applied to create solutions to the puzzles that will be rapidly pieced together. There is no doubt that the ability to precisely control not only the amount, but the delivered spectrum of light will be lynchpins in the both the extreme, and more subtle solutions that will be demanded.

Human Health and Wellbeing Related to Lighting – a Simple Case

Fluorescent fixtures in most commercial buildings provide artificial lighting with a spectrum that is incompatible, or incomplete, when compared to natural light illumination. New research in the area of color science and health shows that human health, wellbeing and productivity can be improved through the use of more natural lighting. The research also concludes that people who spend more time in natural light rather than in artificial light experience an overall increase in productivity and alertness [1].

There is evidence that there are two separate functional pathways that carry information about light to the brain. The non-visual pathway leads to the hypothalamus, the coordinator of many functions, including the release of many hormones. Melatonin is among the best known of these; it is a chemical signal that regulates circadian rhythms and keeps them in synch with environmental light. Melatonin is secreted as light turns to darkness, and is suppressed by bright light [2].

Light serves to synchronize the human body bio-chemical clock. For instance, it has been found that blue light (465nm wavelength) can reduce the melatonin in our blood stream, making us more alert – this is what sunlight produces from morning until afternoon. However, as the day progresses, the intensity of the blue-spectrum in sunlight reduces while there is an increase in reds and purples, thus triggering the increase in melatonin that enables sleep and body repair. The effect of light on melatonin, alertness, and cognitive performance is blue-shifted - a lamp with a correlated color temperature of 6500K (“cold light”) induces greater melatonin suppression and an enhanced alerting effect than does a lamp with a CCT of 3000K (“warm light”) [3].

Light directly influences the amount of melatonin, and other related hormones, that a person’s brain produces, which indirectly affects alertness. With artificially driven imbalances, it’s not just sleep that is affected; almost our entire metabolism, including immune responses, is regulated in this way, and there is the potential for more serious health effects [4]. Conversely, supplemental melatonin has been indicated with positive health effects including slowing down aging processes, and potentially slowing or reversing brain-involved conditions, including Alzheimer’s.

A recent study performed by researchers from the Barcelona Biomedical Research Institute (IIBB), and the University of Granada and the Autonomous University of Barcelona, showed beneficial results with the introduction of melatonin in mice which were experiencing an initial phase of Alzheimer’s. The experts analyzed the combined effect of exercise and melatonin in 3xTg-AD mice that were exhibiting the initial symptoms of the disease, including learning difficulties and changes in behavior such as anxiety and apathy. In fact, mice supported with the addition of the melatonin showed clear indication not just of slowing further onset, but also of actual regression of the Alzheimer’s [5].

Today’s office or factory lighting is constant with a high blue-shifted content, keeping us awake and alert during work, but will often impair the natural late-day shift towards warmer spectrums, thus impacting the sleep cycle for people who work late or work on computer screen at home in the evening (computer and FPTV also deliver a high blue content) [6].

In a sense, the wider direct health effects of properly tuned lighting are effectively still in the early stages of discovery, since the kind of spectral control necessary for such studies has really only become convenient with the advent of LED lighting. Even if we limited the discussion to the relationship between lighting, melatonin production and the importance of the circadian rhythm, it becomes clear in that area alone that LED lighting with tunable white light will provide substantial benefits in our daily lives. By better controlling the spectral content of the artificial lighting around us, we will enjoy more natural alertness with increased productivity in the daytime, while better synchronizing the circadian rhythm to maintain healthy melatonin cycles for better health and performance.

Cognitive Lighting Creates New Options for Control of the Lit Environment

Human-centric illumination is enabled by the coming wave of Cognitive Lighting which implements independent smart sensors that are ‘environmentally aware’ in order to provide not simply data on a number of aspects of surrounding environment, but answers to how best to respond, both to enhance lighting quality and to save energy.

Just what do we mean by Cognitive Lighting? Lighting fixtures and systems available today are relatively un-intelligent and require user input to adjust [the lighting] to specific requirements, if they can be adjusted at all. Unfortunately, the path of least resistance is simply to keep non-spectrally optimized lights on most of the time and at the lights’ highest intensity – irrespective of the occupants’ actual needs.

However, sensor-driven lighting that is easy-to-use is key to adopting more optimized and energy efficient lighting. Users cannot, and should not, be required to directly interact with the lighting in its default mode. Rather, it should be transparent, as the system “predicts” the arrival of an occupant to an otherwise dark or dimmed space and then “sets” the lighting to achieve pre-determined ambient level and spectral mix. From there, while the space is occupied, the system “adjusts” with continual, non-distracting tweaks to maintain both the time-of-day driven human-centric color “track” and the target level of overall illumination.

Should an individual need an increased level of illumination, as a result of a specific task or simply aging eyes, a simple touch, voice or gesture-driven user interface will allow that adjustment, as well as accepting “refresh” commands to extend those settings past the default period, or to return to the standard when the task is complete. Little, if any, training should be necessary. “Here’s the new employee manual on controlling your office lighting,” is not something that should be part of the HR’s orientation process.

Tightly integrated sensing
Sensors built into the luminaire must be the “eyes and ears” of the lit space, delivering useful data on the overall environment – whether it’s occupancy, available daylight, time of day or other variables – and delivers just the right amount of light — when and where it is needed.

Networked occupancy sensors provide the traffic data to enable the lighting system to move to normal operating levels as spaces are approached, traversed and occupied. Ambient light sensors combining photopic, human-like sensitivity with wide dynamic range are responsible for supplying the data used to maintain the correct amount of light to support visual acuity and basic functionality. High-precision color sensors provide both external spectral analysis, to drive color temperature and other required spectral compensation, and will separately provide color response feedback within the luminaire to maintain a balanced closed loop system.

Screen Shot 2016-07-04 at 09.20.48.pngFigure 1: A “cognitive” lighting management system

Building Integration and Energy Savings: By- Products of Human-Centric Lighting

To realize the full potential of human-centric lighting, cognitive lighting system designers will have to consider each sensor- and intelligence-node to be a resource for the system as a whole, in addition to its localized functions. By way of example, consider the path of the first person to arrive in the office for the morning. As they approach the entry point and wave their RFID-equipped badge, the system is clear on their intention to enter the building, and can start to smoothly bring up the lobby interior lights from the “security” state to the “occupied” state. The building management system also should have a pretty good guess on where the user is going to head from there, having identified the user at the security threshold. Whether they are heading to coffee room or their work space, the system can stay one step ahead of them, applying appropriate lighting to the predicted path, as well as creating a level of nearby ambient lighting a the minimal level which provides a needed sense of security. No more “spooky” arrivals followed by the occupancy sensor or switch throwing that creates that typical “all lights on the floor to on” for an audience of one.

To achieve this, both the sensors integrated into the luminaires, as well as a few remote occupancy and motion sensors, need to incorporate both local intelligence and wider networking capabilities. These lights that “think for themselves” greatly reduce the back-end system complexity, while enhancing the overall responsiveness within an individually-defined space. With color and ambient light sensors built into each lighting instrument, on-the-spot decision-making can take place based upon the amount and type of ambient light that is present, along with the time of day and shift-work factors. With low-cost and low-power wireless networking (such as ZigBee), or wired networks (DALI), group intelligence - semi-autonomous controls aware of what each other is doing and able to self-organize the most efficient lighting plan for each moment - tying in to centralized control systems can be readily implemented. What is critical is a sensor system that connects to today’s existing building management structure like Bacnet, KNX, LONmarks [7],[8],[9],[10],[11].

Although current “smart” lighting controls enjoy a centralized approach that hinged upon occupancy to determine on/off requirements, by taking a more granular approach to supplementing the specific working space with only the amount of light needed, and coordinating that amongst area luminaires to maintain a uniformly lit environment, tremendous energy savings can be realized. In addition, a coordinated full-building system provides a new area of flexibility in response to the grid’s future demand-response requests.

In the future, where flexible, autonomous dimming has been instituted, when a 10% cut in energy use is needed, it makes tremendously more sense to delegate the request down to the local spaces rather than applying some kind of “best guess” at the building level. Those individual spaces can be polled to respond with their best available dimming options based upon real-time user activities and occupancy. If one part of the system reports that it can cut 15% in lighting alone, perhaps by substantial additional dimming in the areas with outside light, and full off in areas that might be unoccupied, but that are normally on at some level to reduce the “black hole” effect, then the building level decisions can be greatly simplified. Lights down a lot here, less so here, and the HVAC can remain where it is. Everyone’s happy.

Overall, simply by creating an autonomous, yet highly integrated building-level cognitive lighting system, facilities can realistically expect to save over 50 percent of their lighting energy while providing better, healthier human-centric lighting.

Screen Shot 2016-07-04 at 09.20.54.pngFigure 2: An integrated building managed “cognitive” lighting system


Environmentally-aware, decision-directed, multi-sensor networks and optimized light, this next wave of Cognitive Lighting systems will enhance not only the productivity of the built space, but also worker and group productivity, as well as increasing the health and well-being of individuals. The resultant energy savings will additionally be critical to meet worldwide government mandates to reduce energy consumption and lessen greenhouse gas emissions.

When fully integrated into a larger building management system, lighting that is aware of the immediate environment and broader operating concerns, and is able to intelligently adapt to user and facility requirements with autonomous local- and centralized-control, will re-define the built-environment to enhance comfort, productivity, safety and efficiency, all at the same time.

[1] Sarah Laxhmi Chellappa, Roland Steiner, Peter Blattner, Peter Oelhafen, Thomas Goetz, Christian Cajochen. “Non- Visual Effects of Light on Melatonin, Alertness and Cognitive Performance: Can Blue-Enriched Light Keep Us Alert?” – Plos ONE January 2011 Volume 6 Issue 1 e16429

[2] Jennifer A. Veitch, Ph.D. “Principles of Healthy Lighting: Highlights of CIE TC 6-11’s Forthcoming Report”, Institute for Research in Construction

[3] “Cognitive & Emotional Responses to Lighting: THIS IS YOUR BRAIN ON LIGHTING” – LITECONTROL: Lighting Design Issues

[4] Gilles Vandewalle, Pierre Maquet and Derk-Jan Dijk “Light as a modulator of cognitive brain function” - Trends in Cognitive Sciences Vol.13 No.10

[5] Yoelvis García-Mesa, Lydia Giménez-Llort, Luis C. López, Carmen Venegas, Rosa Cristòfol, Germain Escames, Darío Acuña-Castroviejo, Coral Sanfeliu. “Melatonin plus physical exercise are highly neuroprotective in the 3xTg-AD mouse” Neurobiology of Aging, 2012; 33 (6): 1124.e13 DOI: 10.1016/j.neurobiolaging.2011.11.016

[6] “Does Natural Lighting make us more Productive? Janurary 12 2012 GoodTheraphy.org

[7] Ed Koch, Akua Controls, Francis Rubinstein “Evaluation of Alternative Field Buses for Lighting Control Applications”, Lawrence Berkeley National Laboratory

[8] “Standardizing Communication Between Lighting Control Devices A Role for IEEE P1451” - 2003 IEEE

[9] Mark Dowing Wireless Sensor Networks Will Drive “The Internet Of Things” – Electronic Design Decemver 27 2011

[10] Christoph Hammerschmidt “Enabling wireless smart lighting - with an Internet address for every bulb” - EE Times Europe, April 9 2012

[11] Ed Koch, Francis Rubinstein, Sila Kiliccote “Hardware/Software Solution Unifying DALI, IBECS, and BACnet - Final Report”