Why circadian lighting? Part - 2

elevant global market value of circadian lighting

(US $Billion)

Data source: Verified Market Reports, QY Research, Global Info Research, WiseGuyReports.

Circadian lighting trend in the last 20 years

1.Turning point 1: Year 2002, the discovery of ipRGC cells!

For over 150 years since the discovery of rods and cones in the human eye, scientists had always believed that these were the only photoreceptor cells in the eye. They thought that human visual experiences were interpreted through the neural signal transmission between rods, cones, and the visual cortex of the brain. However, in 2002, Berson and his colleagues at Brown University in the United States discovered a third type of photoreceptor cell in the mammalian retina, the very rare "intrinsically photosensitive retinal ganglion cells" (ipRGCs). These cells contain a newly discovered photoprotein—melanopsin. Unlike rods and cones, ipRGCs do not contribute to vision. Instead, they connect to the suprachiasmatic nucleus (SCN) and play a role in regulating circadian rhythms. Since then, research on human circadian rhythms in the field of biology has opened up interdisciplinary connections related to lighting.

Reference: Phototransduction by retinal ganglion cells that set the circadian clock

Author：David M Berson 1, Felice A Dunn, Motoharu Takao

Issued date：February 2002

2.Turning point 2: Year 2020, the perfection of the LED upstream industry!

Before 2020, even though there were research findings on chronobiological lighting, most targeted studies on lighting environments were still based on fluorescent lamps. According to the principles and practicality of chronobiological lighting, the spectral shape has a significant impact on circadian rhythms. However, fluorescent lamps lack the ability to flexibly adjust the spectrum. Based on its digital characteristics, LED is suitable as a carrier for chronobiological lighting applications. After 2020, with the development of full-spectrum and color-changing lighting, the upstream LED industry chain, including LED chips and phosphors, has achieved more comprehensive commercialization in materials with various wavelengths and spectral shapes. This has effectively promoted the research and implementation of chronobiological lighting products.

Reference: Tailored lighting intervention improves measures of sleep, depression, and agitation in persons with Alzheimer’s disease and related dementia living in long-term care facilities

Author：Mariana G Figueiro, Barbara A Plitnick, Anna Lok, Geoffrey E Jones, Patricia Higgins, Thomas R Hornick, Mark S Rea

Issued date：September 2014

3.Phase in germination: 2010 – 2015

In this phase, the concept of tunable color temperature emerged as the primary understanding of circadian lighting. Through the color temperature tunability, a basic usage logic has been established: using cool light during the day and warm light at night. This represents the initial stage of circadian lighting. However, the issue in this stage is superficial awareness, circadian effects were only superficially recognized. Some lighting companies promoted tunable color temperature lamps as having human-centric functions without scientifically and objectively explaining the mechanisms and principles. Instead, they relied solely on the intuitive visual perception of the human eye as evidence of chronobiological functionality. To this day, some lighting companies still use adjustable color temperature lamps as an excuse to claim that their products are chronobiological lighting solutions. This approach is misleading and lacks a scientific basis.

4.Phase in initial development: 2015 – 2020

Compared to tunable color temperature, the lighting development in this phase has progressed to the inclusion of color tunability with RGBW that it is no longer satisfied with only white light illumination. In this phase, some lighting companies and control platforms have clearly put forward the concept of circadian lighting and integrated it into intelligent control systems, enabling real-time automatic adjustment. However, the issue in this phase is that it only reaches the level of "visual circadian." People merely observe that the changes in light seem to follow the color of sunlight and can even create more colors than natural light, but they are unable to explain the true connection with circadian lighting.

5.Phase in transition development: 2020 – 2025

Building on tunable light, the development of circadian lighting in this phase has become more diversified and can be summarized in the following development points:

•          Tunable chromaticity coordinates along the blackbody curve: this makes the light color more natural and realistic, avoiding visual discomfort caused by color bias and ensuring that colors appear more "accurate."

•          Expanded Color Gamut: in addition to RGBW, existing solutions from film and stage lighting have also been adapted to circadian lighting, introducing various combinations such as RGBAL and RGBCW, which add specific color points and relate to the principles of emotional regulation.

However, the issue at this stage is that it still remains at the level of "visual circadian." Various characteristics (full spectrum, high color rendering, blackbody curve tuning, wide color gamut) are all color metrics and have not been linked to the theories of non-visual biological rhythms. This leaves unanswered the essential questions of circadian lighting: how light affects human rhythms, how to scientifically use light to optimize rhythmic health, and why this method is effective.

6.Phase in scientific development: 2025~

With in-depth research and interpretation of lighting indicators for non-visual biological effects, integrating lighting parameters with biological effect indicators to clarify the requirements for luminaires and lighting design in specific application scenarios. In the scientific development phase, from circadian rhythm monitoring to the discovery and analysis of rhythm issues, and then to using lighting to influence and resolve these issues, an effective closed loop is formed. This allows for the objective and quantifiable design of lighting environments and products, moving circadian lighting beyond merely "visual rhythm" to fully comply with the scientific "non-visual rhythm."

Technical solutions for circadian lighting

Powered by Yuji Lighting, different technical solutions are developed for circadian lighting.

1.FlameWarm™ lighting solution - the “photon melatonin”

The innovation of the FlameWarm™ is not only about its extreme low M/P of 0.046, but is more about that its weight in the V(λ) can reach 34%, while its weight in the ipRGCs sensitivity is only 1.3%. The significance of this is that the illumination from FlameWarm™ can achieve relatively higher brightness without suppressing melatonin secretion. This is particularly important in nighttime lighting environments, as it can maintain a sufficient level of visual alertness without disturbing the circadian rhythm, thereby preventing the occurrence of dangerous events such as falls.

The feature can also be directly and quantitatively demonstrated through the measurement of CS values. FlameWarm™ only begins to produce a certain amount of circadian rhythm stimulation when the Ev reaches 600 lx. In fact, 600 lx is already far higher than the general daytime lighting standards. In contrast, a 2700K LED starts to produce a certain amount of circadian rhythm stimulation at just 150 lx. This makes it very difficult to design the lighting for nightlights or sleep-aid applications using 2700K LEDs.

When designing the visual color of FlameWarm™, a primary wavelength of 600 nm was selected. The blackbody curve is the locus of natural light at different color temperatures. FlameWarm™ is designed as located on it. The common fire is around 1800K, and FlameWarm™ provides an even warmer tint of 1250K, presenting the most natural color for visual comfort.

2.RhythMax™ lighting solution - the “photon coffee”

The RhythMax™ lighting solution is for generating the extreme circadian stimulus for effective wakeup by reaching m-DER to 2.003, exceeding twice the circadian rhythm stimulation effect than natural daylight at the same illuminance level. The innovation of RhythMax™ is that its weight in the V(λ) is approximately 29%, while its weight in the ipRGCs sensitivity can reach up to 70%. The significance of this is that the illumination from RhythMax™ can achieve significant suppression of melatonin secretion at lower brightness levels. This means that, for the same circadian rhythm stimulation effect, the RhythMax™ technology can deliver lower energy consumption, lower glare from luminaires (UGR), and lower blue light hazard (IEC62471).

The feature can also be directly and quantitatively demonstrated through the measurement of CS values. RhythMax™ begins to produce a certain level of circadian rhythm stimulation at an eye-illuminance of just 30 lx. In contrast, a standard 5000K LED starts to produce a certain level of circadian rhythm stimulation only at 60 lx.

When designing the visual color of RhythMax™, a peak wavelength of 480 nm was selected, with a color temperature of over 100000K (for reference only, as it is not appropriate to describe it by color temperature). It is close to the color system of PANTONE color 16-4535 TCX. This choice creates a visual color similar to ice blue, which is friendly to lighting designers and architects. It also avoids the use of deep blue or cyan light directly emitted by LED chips. Although deep blue or cyan light theoretically has a higher m-DER, its luminous efficacy is significantly lower. When reaching the same m-EDI, it releases several times the irradiance, which is not conducive to controlling blue light hazard.

3.Well24™ Day / Nite lighting solution – stronger / weaker melanopic lux white light

The Well24™ solutions are white light from warm color temperatures (Nite mode of 2200K/2700K) to cold color temperatures (Day mode of 4000K/5000K/5700K).