06 November 2014

Human Centric Lighting: A future market with potential

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Light decisively influences the well-being of people, characterises their day and night time rhythm and effects activity and the ability to concentrate, as is generally known. Comparatively young however is research and development that attempts to utilise this health-promoting effect of light. "Human Centric Lighting" is the generic term for one of the most promising and high-growth segments in the lighting branch.


Here a focus is placed on people, their health and the influence of artificial lighting on the sense of well-being. The spectral composition of this artificial light as well as its intensity are oriented to the natural course of daylight, and simulate this to a high degree. These parameters significantly determine whether light has an activating or calming effect on the human organism, In the following talk, we offer an overview of the current state of the technology, report about specific practical experience within the various application areas, and demonstrate future trends as well as the latest research projects.

The Circadian System

 During the process of evolution, the circadian system developed under the influence of the natural sequence of day and night (Fig.1). Daylight has a significant influence on physiological and psychological parameters. Consequently, the human eye contains not only rods and cones responsible for bright/dark vision and colour vision, but also has so-called non-visual photoreceptors that have responsibility for influencing the human circadian rhythm. These receptors have maximum sensitivity in a wavelength range of approximately 450 nm.




In modern societies however, people are distanced from natural sequences – we spend ever-more time in closed rooms bathed in artificial light, and many people make "the night to day" in a professional sense, without taking into account the rhythm of the circadian system.


A noticeable symptom of this is shortened or impaired sleep. Light with an increased blue component suppresses the evening discharge of the sleep-promoting hormone melatonin. On the other hand, light with high red components supports the discharge of melatonin, thereby contributing to relaxation. 


Human Centric Lighting: promoting good health

This is exactly where Human Centric Lighting has its effect – with the aim of providing support for the circadian rhythm of people. The human hormone balance has responsibility for this, especially the melatonin hormone, which determines our waking and sleeping behaviour. To increase the discharge of this hormone, intelligent lighting systems feature various light spectra, and with differing intensities, depending on the time of day. The following applies here: light sources with a warm light colour, meaning with a low colour temperature, have a lower circadian activation factor. The higher the blue component in the light source spectrum, the higher is the circadian activation factor and stimulation of the "blue receptors" that are responsible for controlling the biological functions. Positive effects can be achieved if this artificial light adapts to the natural human biological rhythm, by controlling the colour temperatures and intensity.


Effectiveness has been proven many times

Various scientific surveys have demonstrated that sustainable effects are achievable with such controlled lighting systems – as a result, the error quotas of school pupils could be reduced by more than 30 per cent. The productivity of people at workstations was also partly increased by 20% in addition to improved motivation of these workers. Dipl.-Ing. Reinhold Hetzel, Graz Technical University, stated: "The type and quality of artificial light sources and their effectiveness on comfort, well-being and health are being ever-more noticed and discussed (chronobiology). Following on from this is the requirement to simulate natural light (sunlight) as part of interior lighting." 1


In the year 2008, the PLACAR common research project demonstrated how brief exposition to light during the evening positively influences physiology and behaviour.2 It was seen that the effectiveness manifested itself after only 10 minutes, and that the effect increases with time if no adaptation occurs. The effect depends on light intensity, its direction and its spectral distribution. Based on these recognitions, systems have been developed and continuously optimised in past years, along with the advances of LEDs and specific PI-LED technology. The application areas for Human Centric Lighting (made possible and economically feasible thanks to LED) are exceedingly diverse and will become even more multifaceted in the coming years.


Highly promising medical applications

Positive effects can also be achieved in the medical sector, as demonstrated by various pilot projects. A typical example is pre- and post-operative situations where recovery processes can be supported by using controlled light and the consequent increase of melatonin discharge. A project carried out by the Charité Berlin concerning sleep research, clinical chronobiology and optimised lighting in care homes where residents suffer from dementia achieved highly interesting results: 3 "Night-time confusion is a primary reason for enrolling patients with Alzheimer's dementia in care homes. The increasing occurrence of nightly agitation is caused among other factors by a weakened circadian system. Exposure to daylight is reduced particularly with a weakened bodily constitution, and artificial light used in care homes often has insufficient illuminance levels and a low blue component."


The survey carried out in a care home for dementia patients analysed how optimised lighting is able to achieve positive effects. A luminaire from TRILUX was installed in one of the care home's relaxation rooms, where residents bring a large part of their day. It was seen that the state of agitation and restlessness was significantly less after just one month. To determine this, the Cohen Mansfield Agitation Index (CMAI) was measured two weeks before and four weeks after the installation. This agitation index measures the occurrence of agitated behaviour related to the previous 14 days. The total score of the index significantly reduced with the test persons.

The common research project is also highly promising that was initiated in mid-2014: According to the principle of "optimised light systems for improving performance and health" (abbreviated to OLIVE in German), the options of intelligent lighting will be analysed, ranging from energy saving to the promotion of health. The OLIVE joint project is intended to research the technological and bio-medical fundamentals for such intelligent lighting, and display the new light as part of various everyday situations and possibilities. The North Rhine Westphalia light forum will then evaluate the intelligent light within various application scenarios. The project is planned for a period of three years, up until mid-2017.

Perspectives for Human Centric Lighting

Scientifically founded, Human Centric Lighting enables many applications today, for example in the medical sector, in care homes and other commercial areas such as offices, retail and education. As result, it is already possible today to support the natural biological rhythm at the workplace with colour temperature daylight sequences – ranging from a stimulating effect in the morning to a more relaxed lunch period, and including phases of concentration in the afternoon and a soft transition to going home in the evening. Future focus applications are for example manufacturing companies with multiple shifts, whereby optimised lighting systems are able to improve the sense of well-being and ability to concentrate for such shift workers – and with positive effects for work safety among other factors. Simultaneously, it is of course also necessary that the relevant standards and directives for workstation lighting continue to be updated while taking into account such recognitions.



 Already today, complete solutions are available from a single source that meet a wide diversity of needs (see Fig. 3). Premium solutions enable daylight to be precisely simulated according to the Planckian Curve, and with a daylight-similar quality of light (Ra>90). The complete system of PI-LED, module, LMU and control units covers all construction forms (spot, area, planar and linear) with these having only exceedingly low colour differences to each other (MacAdams<3).




The precise setting of colour temperature ranging from 2,500 to 7,000 K complies with maximum demands for quality and precision, and can be implemented automatically according to time or modified manually or via sensor control. There is also the option of using the RGB colour space in addition to white tones for daytime sequences, enabling specific light moods to be achieved. The premium system offers extremely wide flexibility in terms of control options as well: ranging from wired solutions to radio technology (wireless with ZigBee) that are often a feature in the modernisation sector, all options are open.


MixedWhite systems consisting of highly efficient warm white and cool white LEDs enable economic Human Centric Lighting solutions. Colour temperature and brightness are manually controlled with a push-button according to the room situation. The core consists of ZITARES intelligent, enabling economic implementation thanks to two independently controllable output channels. The system also provides maximum flexibility because the LED modules used can be freely specified. MixedWhite+ additionally provides the option of an integrated clock that enables the programming of individual key characteristics for the daylight-dependent, automatic modification of colour temperature in compliance with our circadian rhythm. Even higher energy efficiency is achieved with daylight-dependent control in combination with presence detection. System control is convenient via remote control, touch panel or combi-sensor.


In the end though, it is the users along with the specific application areas that decide which technological version is used to achieve Human Centric Lighting. . Some applications, such as industrial lighting applications, are predestined for simple, white-white solutions according to cost-benefit analyses. In other areas, for example medical applications, maximum precision is needed for coordinating the light spectrum in the form of high-end systems. The market already offers solutions in this bandwidth that are mature for application.

One recognition is important in this connection: today's lighting standards are operationally safe, energy-efficient and with high performance, but do not represent the optimum when people are focused on with their physiological and psychological needs. Human Centric Lighting is an essential basis in this respect that will determine and change the lighting world in coming years.



1 Tunable Natural Light Realized by Phosphor-Innovation Light-Emitting-Diode Technology, Reinhold Hetzel, Stefan Tasch & Günther Leising, Springer Verlag Vienna 2012

2 PLACAR Summary Report, Horst Rudolph, Arnsberg 2009

3 Optimised lighting reduces agitated behaviour of care home residents suffering from dementia, Wahnschaffe A, Nowozin C, Haedel S, Rudolph H, Rath A , Kunz D., Berlin 2008



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