5 minute read
Improve Alertness, Focus and Comfort with Biologically Effective Light
It is well documented that light has a significant influence on the human body. For instance, the exposure of intrinsically photosensitive retinal ganglion cells (ipRGCs) to cyan light can suppress the production of a hormone called melatonin, which affects the human wake/sleep cycle. Here, lighting technology manufacturers are tapping into the effect of melatonin suppression, which is beneficial in commercial settings such as offices, factories, and schools as it makes people more alert and attentive. However, as excessive melatonin suppression can become detrimental to health, it is important to limit the exposure to cyan light according to the natural rhythm of the human body. Fortunately, the latest LED technology can help lighting system designers deliver this fine balance with absolute precision.
Today lighting and lighting control are increasingly becoming core elements of IoT projects within all kinds of buildings, including factories and warehouses, hospitals and healthcare facilities, offices and showrooms, and schools and universities. Using human-centric lighting (HCL) to raise alertness in these environments can prolong concentration levels and drive up productivity. Of course, some environments, such as hospitality, require the opposite of alertness, where the aim is to encourage relaxation and rest. Again, artificial light can create the right mood to stimulate this sense.
Simulating the Daylight Cycle
Among the principal concepts of HCL is replicating the natural daily lighting cycle, known commonly as circadian lighting. Simulating the sun’s daily lighting cycle (and stimulating human ipRGCs) requires bright blue light in the morning (when the sun is bright and the sky is blue). By way of explanation, morning daylight has a higher content of lower wavelength (cyan) light, which stimulates the cells. The daylight also has a high correlated color temperature (CCT) in the range of 5500–5800 K for a given time. Progressing through the afternoon, there is a gradual reduction in the color temperature of daylight until it reaches approximately 2700 K at sunset, where warm yellows/reds take over. These low CCTs are predominantly beyond the sensitive wavelength range of ipRGCs.
Although seemingly different, ipRGC stimulation and the CCT of natural light have much in common; spectral light distribution is ultimately what determines these two characteristics. As HCL solutions try to mimic daylight, a tunable ipRGC solution is a logical market requirement. Lighting designers tasked with delivering HCL need the ability to tune color temperature and spectrum - the proportion of cyan within the light.
Until now, attempts at delivering a highefficacy product have fallen short. To create a tunable source, current solutions use melanopic-enhanced LEDs and conventional LEDs together. The issue is that melanopic-enhanced LEDs still emit light outside the melanopic-sensitive wavelength range and conventional LEDs emit light inside the melanopic-sensitive wavelength range. It is therefore not possible to control the melanopic light output part of the solution independently using only the melanopic-enhanced LED.
Dynasolis™, The Circadian Tunable Light Source
Essentially, an ipRGC Color Temperature Tunable (CTT) light source has two functions with regard to circadian lighting design: high melanopic light output in the morning; and low melanopic output when it is not required (in the evening or in environments that seek relaxation). By providing a clear separation of this dual functionality, it becomes possible to design a circadian tunable light source offering a combination of energizing blue and peaceful, calming, warm white, as provided by the Dynasolis LED lighting solution from Nichia [1].
Azure color that can effectively supply light at 480 nm.
Just to be clear, not just any blue will suffice. Phosphor-converted white LEDs frequently use a blue pump in the range of 450 nm because producing LEDs at that wavelength maximizes wall plug efficiency. However, research into the non-visual receptors of humans has revealed that the peak sensitivity for ipRGCs is closer to the cyan region, around 480–490 nm. To deliver system-level efficacy at 480–490 nm, phosphor-converted cyan represents the way ahead, particularly if it offers the same
Comparison of the melanopic ratio between a conventional 6500 K and Azure.
forward voltage and Z-height dimension of the warm white LED for focal length matching and uniform mixing.
With these thoughts in mind, the optimal solution derives from combining two separate LED spectra: a cyan LED with an ipRGC sensitivity-optimized spectrum for high melanopic output (without emission in the rest of the spectrum); and an LED with very little to no light in the melanopicsensitive wavelength range (such as a 2700 K LED, CRI 80 or even CRI 90).
As a result, designers can today take advantage of true dynamic lighting with both color and spectral tuning, while maintaining high color rendering and high efficiency. The benefits are a high melanopic ratio at cooler CCTs (even higher than daylight), and a low melanopic ratio at warmer CCTs.
Put to the Test
The Fraunhofer Institute for Building Physics IBP recently performed a comparative analysis between Dynasolis [2] and standard LEDs, attempting to assess the cognitive and psychological effects of different light color temperatures and spectra on 35 volunteers. These effects included alertness, attention, and relaxation.
The results clearly showed the advantages of the Dynasolis solution, which provided equal or better results in the different phases of human lighting requirements than a variety of standard LEDs thanks to its color temperature and spectrum tuning capabilities. In particular, the attention tests revealed significant improvements in the reaction times of volunteers, supported by good performance with regard to relaxation, thus demonstrating its ability to meet the full plethora of applications.
In summary, most commercially available HCL systems work primarily by adjusting CCT. While a solution such as Dynasolis addresses color tuning, it also delivers efficacy, color quality and, most importantly, increased melanopsin stimulation, the light that explicitly targets melanopsincontaining neurons in the retina of the eye. These neurons (ipRGCs) are connected to a part of the brain that regulates the circadian cycle, along with associated reflexive neuronal and hormonal responses to light.
Traditionally, multiple LEDs of different color temperatures are installed to meet different HCL needs. However, with Dynasolis users can benefit from an improved and simplified lighting installation for working environments that follows the principle of HCL to boost alertness, concentration, and comfort.
Dynasolis will be presented at Nichia’s booth at the Light + Building exhibition (Hall 8, Stand D60) on 2-6 October 2022
in Frankfurt, Germany. ■
AUTHOR: Menno SCHAKEL
As a Technical Marketing Engineer for Nichia, Menno focuses on customer’s technical requirements, bridging the gap between the customer and Nichia’s product research and development. Menno worked as an optical measurement specialist at Philips Lighting and a British measurement laboratory earlier in his career. He is also a member of several CIE Division technical committees.
m.schakel@nichia.eu
References
[1] https://led-ld.nichia.co.jp/en/product/index.html [2] https://led-ld.nichia.co.jp/en/product/lighting_dynas olis.html
