Handbook of Advanced Lighting Technology

There are many histories of discovery, invention, and development in the electric lamp industry. One of the best I have found, from the earliest days to 1947, is a book by Arthur Bright, “The Electric Lamp Industry” (Bright 1949). Several more recent ones are listed in the references (Zissis and Kitsinellis 2009; Gendre 2003). A GoogleTM search under the heading “History of Light Sources” turns up a number of websites, of which a sampling is listed (http://www.mts.net/~william5/history/hol.htm; http://www.invsee.asu.edu/Modules/lightbulb/meathist.htm; http://www.en.wikipedia.org/wiki/Light; http://www.edisontechcenter.org/incandescent.html; http://www.wired.com/gadgets/miscellaneous/multimedia/2008/11/gallery_lights; http://www.inventors.about.com/library/inventors/bllight2.htm; http://www.ies.org/lighting/history; http://www.nelt.co.jp/english/products/useful/01.html).

The second decade of the twenty-first century has become the period when light-emitting diodes (LEDs) are beginning to reach their promise of being the dominant technology for generating light. For those who have worked in this field, it is gratifying to see the enthusiasm of consumers for the technology and how the rate of adoption often outpaces expert projections. At the time of writing, leading manufacturers of lighting products achieve more than 40 % of their revenue by sales of products that use LEDs as the light source, and this portion is projected to be over 80 % by 2020. The rapid adoption of LEDs is largely due to the tremendous improvement in underlining technology which enabled cost reductions and increase in functionality of lighting systems. As novel as LEDs may seem, the related discoveries and technology development have over a century- long history, with generations of researchers working on fundamental exploration without which the present day successes would not have been possible. At the same time, the present state of the art of LED technology and manufacturing lacks the homogeneity of the more established fields such as conventional light sources or silicon integrated circuits. This chapter will review the pioneering work, with more focus given to the developments of the most recent decades. An outlook to the directions that the field may take will be provided as well.

This chapter describes how, in order to achieve low droop and high-efficiency light-emitting diodes (LEDs), we investigated the following multiple quantum wells (MQWs) and electron-blocking layer (EBL) design to enhance our LED devices: graded-thickness multiple quantum wells (GQWs), graded-composition multiple quantum barriers (GQBs), selectively graded-composition multiple quantum barriers (SGQBs), and graded-composition electron-blocking layer (GEBL). Besides, the crystal quality of the epitaxial layer was enhanced by introducing freestanding GaN substrate for the epitaxial growth of III-nitride epilayer. On the other hand, in recent years, the epitaxial growth of GaN-based materials on Si substrate has a great potential for applications in low-cost and high-efficiency LEDs. Hence, the properties of GaN-based LEDs on Si will also be described in this chapter.

LED materials for incandescent lighting are based on thin Gallium-Nitride layers. Due to the lack of Gallium-Nitride substrates such layers are usually grown as thin crystal layers on sapphire or silicon-carbide substrates. Gallium-Nitride grown on silicon is a material platform which offers a huge benefit as low substrate cost, large substrate diameter, and also opens a route for manufacturing in depreciated Si wafer fabs. But long GaN on Si was believed to be a niche and not suited for high performance devices. This is because material growth requires processes with temperatures above 1000 °C and thermal stress leads to cracking of layers even below device relevant thicknesses. In the last 15 years these problems have been solved and today GaN on Si based LEDs are competitive to GaN on sapphire based devices. This chapter describes the development of GaN on Si LEDs, the differences to GaN on sapphire based structures and different routes for achieving a high output power although these layers are originally grown on a light absorbing substrate.

In this chapter, thin film GaN-based light emitting diodes (LEDs) fabricated into n-side-up and p-side-up LEDs on mirror-substrate structures using a combination of wafer bonding, laser lift-off and surface texturing techniques were described. The effects of Pd, ITO/Al, NiO/Ag, NiO/Ag/Ni, and NiO/Au/Ag mirrors on the n-side-up GaN/mirror/Si LED properties were studied. It was found that the characteristics of the vertical-conducting n-side-up GaN/mirror/Si LEDs with a NiO/Ag/Ni mirror structure showed the best performance than the other mirror ones. After the thermal anneal process, the specific contact resistance of NiO/Ag/Ni to p-GaN can be reduced. The output power of the n-side-up GaN/mirror/Si LED shows nearly three times in magnitude as compared with that of the original GaN/sapphire sample. On the other hand, the p-side-up GaN LEDs were fabricated using a combination of omni-directional reflector (ODR) and double-sided textured surface (both p-GaN and undoped-GaN) techniques. An Essential Macleod program was used to simulate the optimum thickness of the ODR structure. The reflectivity value of ODR structure used in work can reach 99%. On the top-side textured surface, the p-type GaN with hexagonal cavities was grown under low temperature (LT) conditions using metalorganic chemical vapor deposition. The GaN LED with a suitable LT p-GaN cap layer thickness was also studied. Experimental results indicate that the GaN LED sample with the 200-nm hexagonal cavity GaN layer on the surface exhibits a 50% enhancement in luminance intensity. The luminance efficiency can be improved. This indicates that the thin-film structure can enhance the light extraction efficiency of GaN-based LEDs, especially for large chip sizes.

White Light-Emitting Diodes (WLEDs) is a promising conserve energy device for altering the traditional illuminating apparatus because of their high efficiency, high flexibility, long lifetime, low energy consumption, and friendly environment. Of course you can frequently find WLEDs in your daily life. Phosphor is an important component of WLEDs and has been investigated broadly. This chapter introduces readers who begin meeting these fields to understand phosphor including history, principle, application, and perspective. The first part is a fundamental definition to luminescent materials. The second part provides requirements, classifications, and applications of phosphors for phosphor-converted LEDs (pc-LEDs). Finally, we propose some prospects and challenges of optical materials in the future.

We have witnessed the incredible progress in Phosphor-converted LEDs technology from around 10 lm/W efficacy in 1996 to now that is in excess of 170 lm/W. This efficacy value make the white LEDs an excellent candidates for the realization of the next-generation illumination devices. Also, LEDs are having small dimension, high robustness to atmospheric agents and shocks, and fast modulation speed that can be effectively exploited to achieve a linear control of the luminous output of the devices, by means of pulse width modulation (PWM) as well as visible light communication, an alternative to Wi-Fi; their applications have been extended over simple illumination. All these applications require the LEDs to operate reliably.To ensure the reliability of LEDs under operation, it is important to understand the degradation mechanisms of LEDs under the three external operating conditions, namely, drive current, temperature, and moisture. The degradation of LEDs can be attributed to either the GaN chip itself or the LED package. In this chapter, we will focus only on the package degradation due to the operating conditions.In view of the general packaging structure of high power LEDs, this chapter will examine the degradation of the several components in the packaging, namely the phosphor coating, die attach, silicone encapsulant, plastic lens, and bonding wire under the above mentioned operating conditions. Reliability prediction of the LEDs and the measurement methods to quantify their reliability will also be discussed, including LM-80 and TM-21.

Thermal management is one of the most essential issues for LED applications. The output power, efficiency, emission spectrum and reliability of the LED chip and phosphor are functions of temperature. Without proper thermal management, the output of the LED could depart from the desired performance. Basic heat transfer phenomena and corresponding calculations are introduced as well as the thermal behaviors and concerns of the essential components of an LED. A quick method to estimate the thermal resistance of an LED package is provided based on the shape factor of the geometry at the end of this chapter.

Light-emitting diode (LED) has been extensively applied to general lighting since the luminous efficacy exceeded 100 lm/W. In addition to high energy efficiency, the advantages of fast response, wide color range, narrow bandwidth, compact size, and environmental benefits extend the application of LED to display, communication, and others (Sun et al. 2004; Zukauskas et al. 2002; Schubert and Kim 2005). In regard to a light source with the use of an LED in lighting application, three properties related to the optical property should be addressed. The first is the optical efficiency, the second is the light pattern distribution, and the third is the color consistency. All these three properties can be determined in the chip level, the packaging level, and also the luminaire level. The chip level and the packaging level take the majority to determine the most properties of an LED luminaire. Among these properties, chip-level optics is especially important in intrinsic energy efficiency of an LED. In contrast, the packaging design is more important in color performance, especially for a phosphor-converted white LED (so-called pcW-LED). In addition, the optical pattern and energy efficiency are two important factors determined in this level.

White OLEDs are ultrathin, large-area light sources made from organic semiconductor materials. Over the past decades, much research has been spent on finding suitable materials to realize highly efficient monochrome and thus white OLEDs. White OLED panel efficacy has reached 90 lmW−1, and a tandem white OLED panel has achieved a lifetime of over 100,000 h at 1,000 cdm−2. LG is set to launch a 55″ OLED TV in 2013, and OLEDs will be expected to a make bigger breakthrough. Although white OLED panels show superior performance, there is still much room (nearly160 lmW−1) for improvement, in view of the theoretical limit of 248 lmW−1. With their high-efficiency, color tunability, and color quality, white OLEDs are emerging as one of the next-generation light sources.

In this chapter, we will review the progress of white OLEDs based on organic small molecules in view of device architectures. The basics of white OLED devices are, firstly, demonstrated, and then the advanced architectures and current status of white OLEDs based on fluorescent, phosphorescent, and hybrid emitters are discussed. Because tandem structures, where similar or different emitting units are connected through a charge generation layer (CGL), provide further improvement in the efficiency and stability of white OLEDs, the advances of tandem white OLEDs are also discussed. Finally, the future outlook of white OLEDs is given.

Applications of organic light-emitting diodes (OLEDs) have been rapidly developed since the first demonstration of green OLEDs by Tang and Vanslyke (1987). The original structure of an OLED consisted of a layer of organic electron transport layer (ETL)/emitting layer (EML) using 8-hydroxyquinoline aluminum (Alq3) and a hole transport layer (HTL) using an aromatic diamine. In order to inject charges and out-couple the emitted light, the organic layers were sandwiched by a transparent indium-tin-oxide (ITO) anode and a reflecting metal cathode. Such an OLED can operate at high brightnesses, which can meet the requirement for display and lighting applications. Unfortunately, the poor carrier injection efficiency from electrodes led to the high operating voltage even for standard luminance of 1,000 cd/m2 for display applications, resulting in undesirable high power consumption and very short lifetime. In 1997, Hung et al. showed that a very thin 1–2 nm lithium fluoride (LiF) layer adjacent to the ETL and aluminum cathode which greatly improved the injection efficiency for OLEDs, resulting in a low operating voltage at high brightness (Hung et al. 1997). The improved injection efficiency is attributed to forming an ohmic contact at the metal/organic interface which facilitates carrier injection. A similar approach at the other side to reduce the injection barrier of holes between the anode and the HTL was demonstrated by simple ultraviolet ozone (UVO) treatment on ITO-coated glass substrates (Sugiyama et al. 2000; Lee et al. 2004). The UVO treatment increases the work function of ITO by removing carbon contaminants and creating a tin-deficient and oxygen-rich surface. Another well-adopted treatment to improve hole injection efficiency is to insert a high work-function conducting polymer poly(3,4-ethylenedioxythiophene):poly(4-styrenesulphonate) (PEDOT:PSS) layer between the anode and the HTL (Jonas and Schrader 1991; Carter et al. 1997; Elschner et al. 2000). Nevertheless, even with the improved carrier injection with those interfacial modifications, the low device efficiency still remained a challenge for commercialization.

This chapter describes the typical manufacturing processes used to fabricate white OLED lighting panels, with an emphasis on OLEDs produced by dry manufacturing methods such as VTE. OLED panel fabrication is typically classified into three categories: front-end fabrication, sometimes referred to substrate or backplane fabrication, OLED device fabrication, and back-end fabrication including encapsulation and packaging. This chapter mainly focuses on the substrate and OLED device manufacturing processes.

OLED manufacturing can be classified into two categories: dry and wet methods. The dry manufacturing method refers to the conversion of raw organic materials from a solid powder form into a gas phase. In this method, the powder is heated to above its sublimation temperature to form a vapor which then condenses onto a substrate, all while in a high-vacuum environment. The wet method refers to the application of organic materials dissolved in a solution or a condensed liquid phase. In this wet form, the solution is applied to the substrate by spin coating, slit coating, inkjet printing, or other methods and then dried before applying the next layer. In both methods, the organic material is finally condensed onto a substrate in a solid-phase form. This chapter describes the methods and equipment typically used to manufacture OLED devices, with a focus on dry manufacturing methods such as vacuum thermal evaporation (VTE) and other vapor deposition techniques.

Dimming is critical to delivering the promise of solid-state lighting, but it needs to be implemented properly per the requirements of the application. Basic types of dimming, both analog and PWM, and their effect on LED characteristics are covered. Various methods of implementing fast and accurate PWM dimming are described. Phase-based dimming and the inherent complications associated with it are given some treatment, given its prominence in the market today, as is the 0–10 V dimming standard. The chapter then looks to the future and proposes various system-level architectures that support optimal intelligent lighting solutions. Trade-offs and considerations when selecting a communications infrastructure, including the physical layer, protocol, and application layer, are detailed.

Sensors have been used for decades for security, control of lighting, personal convenience and the control of heating, ventilation and air conditioning. For lighting control, sensors are widely used to meet energy codes in buildings and save significant energy. This chapter will discuss the fundamental science used in conventional passive infrared and ultrasonic sensors. Passive infrared sensors detect the motion of warm bodies by detecting the heat they radiate. Ultrasonic sensors detect the motion of a body by measuring the Doppler shift of reflected ultrasonic waves transmitted by the sensor.

Silicon photocells have been used for years to inform a lighting unit of the simple presence or absence of other light in the vicinity. The most common outdoor application has been street lighting, which lends itself to the straightforward on/off control information. The needs of an advanced lighting system, however, differ from those of a streetlight or other dark/light, on/off decision scenarios. Among its other distinguishing characteristics, an advanced lighting system will be expected to adapt to specific human-centered needs within a space. While adaptation capabilities in some systems may include the ability to adjust the color qualities or color temperature of a space, it will most certainly be expected to be able to vary illuminance levels in order to maintain a fixed level of brightness suitable to the user or task at hand, regardless of the variance in sunlight or other ambient lighting within the space. In order to accomplish this, a lighting decision engine will require knowledge of the specific amount of light within a space at any given point in time, measured in a human-centered fashion. This is the role of an ambient light sensor or ALS. This chapter will discuss the technical aspects of the ALS, including how it differs from a normal photocell, and will explore the communications and intelligence extensions that will be required for a complete sensor subsystem. A functional model will also be addressed to provide an illustration of how this important technology can be expected to be applied.

Innovation in solid-state lighting technology is rapidly expanding the potential for new functionality as well as the range of impacts and applications. While traditional illumination is based on a set of fixed sources that satisfy localized needs for task and ambient lighting, solid-state lighting systems propose to integrate distributed sources and sensors across the lighting space. The target “lighting field” expresses the needs of users for illumination beyond basic needs to consider energy efficiency, worker productivity, occupant health, diverse information needs, and entertainment. The lighting field is monitored by distributed sensors and closed- loop adjustments are implemented automatically to achieve the goals of the illumination system. Design of such advanced lighting systems will require new methods of representation and analysis of distributed lighting sources and sensors. This chapter introduces methods that are being explored within this new research framework. Basic methods of adaptive light field sampling, representation, estimation, and control are presented, and future directions for adaptive distributed sensing and control methods are discussed.

The technological advances in LED light sources, sensors, and control systems have ushered a new era of smart lighting control systems that provide the right quantity and quality of light when and where it is needed in order to enhance the energy savings, maintenance savings, comfort, health, productivity, safety, well-being, and user satisfaction. A networked lighting control system can collect a wide variety of data including presence, ambient light, dimming level, power consumption, user interactions, user preferences, device status, and device failures. These data can be exploited to offer energy management, space optimization, demand response, trend analysis, user comfort maintenance, automatic fault detections and diagnosis, predictive maintenance, and other advanced applications and services.In order to realize the full potential of smart lighting systems, we need very efficient and scalable networking technologies that can support building-wide, enterprise-wide, and city-wide connectivity. The industry has realized these needs leading to the development of a plethora of networking protocols, both proprietary and standardized. Although the benefits of standardized systems over proprietary technologies are recognized by stakeholders, no standard has emerged as the dominant choice leading to a very fragmented market landscape. In this chapter, we provide a brief overview of standardized networking technologies suitable for lighting controls applications. We also discuss their key features and commercialization prospects.

This chapter examines the effect of major technology trends on the use of adaptive controls in commercial and institutional buildings. Adaptive controls were originally designed to reduce the energy wasted by building lighting systems. Office buildings, in particular, were notorious for leaving lights burning all night. This conspicuous waste led lighting companies to develop lighting schedulers and occupant sensors to begin to deal with the most obvious problem. These early lighting control products formed the basis of a slowly growing lighting controls market. As digital control technology gradually supplanted analog control, manufacturers would field control systems of increasing complexity and capabilities, such as daylight harvesting systems with automated shading and demand response-enabled controllers.

While daylight harvesting is one of the most energy efficient ways to minimize energy consumption in areas with adequate nature light inside buildings, Ambient Light Sensors (ALSs) are still not being widely installed. Many drawbacks on installation and commission of ALSs, are holding back their wide spread use in building sector. Most of the drawbacks are in relation with their position, field of view, spectral response, control algorithms, commissioning and the associated user’s response. Moreover, with the advent of LED technology, lighting designers and engineers are focusing only in LED luminaires. Thus frequently ASLs are excluded from the planning, despite their even greater energy saving potential, not only in new installations but also during building retrofitting. The promising coming of CCD or CMOS image sensors can show some promise, but it is not clear yet if they can be widely incorporated in the building sector. Scope of this paragraph is the understanding of the nature of an ALS and its proper integration to buildings for their wide spread use.

As light-emitting diodes (LEDs) increasingly displace incandescent lighting over the next few years, general applications of optical wireless (OW) technology are expected to include wireless Internet access, broadcast from LED signage, and machine-to-machine positioning and navigation by light. This section explores several fundamental research topics of indoor optical wireless communications (IOWC). The authors develop a simulation method to generate IOWC channel models by tracking light reflections. The method is further optimized by investigating the contribution of each order of reflections and proposing a calibration method.

Visible light communication can be used for indoor localization by sending location information from LED lights. Several methods of such indoor localization have been proposed. The indoor localization using visible light communication will make it possible to realize many new applications including indoor navigation, location-based advertising, robot control, and accurate measurement of architectural structure.

As the lighting industry moves toward long-lasting solid-state luminaires, advanced systems will begin to integrate novel use cases into the lighting infrastructure. The proliferation of wireless devices and the demand for wireless access in indoor environments create a synergy between the wireless communications and indoor lighting industries. Since wireless traffic demand is at its highest in areas where artificial lighting is already in place, it makes perfect sense to incorporate novel wireless access technologies into the lighting infrastructure. This chapter focuses on the integration of visible light communication (VLC) with radio-frequency (RF) networks in order to provide additional wireless capacity in areas where RF is challenged with meeting the growing demand. We review current trends in wireless network access, provide an overview of VLC, and detail the requirements for implementation of such an integrated system.

One of the earliest reports on the usage of artificial lighting in horticulture dates from before the invention of the incandescent lamp. Horticulture in controlled and closed environments is one of the most energy-intensive cultivation systems in agriculture. Artificial lighting is an important part of it. Its use allows for year-round production of quality vegetable, fruit, and ornamental crops independent of weather conditions and geographic location. This chapter reviews the main aspects involving the usage of horticultural lighting considering the challenges faced by the horticultural industry in the context of a food- and energy-hungry world.

When considering indoor lighting, a museum has unique requirements in terms of the quality of illumination needed, taking into account that it may host a variety of different activities simultaneously. This article will consider these requirements, developing a particular focus on exhibition lighting in museums. It will not be limited to conservation issues and problems of visual ergonomics, which are objective factors, but it will also emphasize the role played by lighting as an element influencing subjective factor, similar to other elements of scenography.

The practice of landscape lighting varies dramatically from interior lighting. No walls, no ceilings, darkness, and continual change encompass most of the variables that separate how we approach landscape lighting from interior lighting. In addition, landscape spaces typically don’t have “visual tasks.” Landscape lighting connects humans to their landscapes that have otherwise been essentially erased by darkness. It has the ability to calm people and help them relax in the “after-work hours.” Designing for our psychological and physiological responses allows us to create spaces that feel good to people. One example is that humans visually respond to vertical surfaces before horizontal, so when we light hedges, trees, or walls, we give visitors a clue as to the boundary of a space. This aids their sense of safety.

This chapter covers some basic aspects of the fundamentals of the human visual perception. Given the enormity of the subject, we will only give a very limited account of this huge area of intellectual activity. We will first discuss the structure of the visual system that is necessary to understand the functional processing of visual information and its limitations. Next, we will elaborate on some classic visual psychophysical results that delineate the limits of detection and discrimination. With these basics, we will introduce the reader to three important streams of information processing pertinent to lighting and display technologies, namely, spatial vision, flicker fusion, and color vision. We do not discuss many aspects of visual perception such as binocular visual perception, shape and form recognition, face recognition, etc. due to space constraints. Good overviews and detailed discussions of various aspects of visual perception can be found in a number of books, e.g., Cornsweet (1970), Schwartz (2010), Palmer (1999), Norton et al. (2002), and Werner and Chalupa (2013), and Chalupa and Werner (2003) or in the chapter by Lakshminarayanan and Raghuram (2003).

Though the physical principles and visual mechanisms underlying color have been studied for centuries, the modern colorimetric system used to quantify and specify the color properties of light sources and illumination had not even begun to be developed 100 years ago. Because color only exists when the physical properties of light and materials interact with the human visual system, any such system must essentially model the link between physics and perception. This is an enormously difficult task and the colorimetric system hasn’t always been successful. Nonetheless, since the origin of colorimetry in the early twentieth century, remarkable progress has been made.

Color rendition metrics, which assess light sources in terms of the color quality of illuminated objects, are advancing with the development of lighting technology and with the increasing needs of lighting users. This chapter reviews different metrics of assessing the color quality of light sources. We show that the traditional measures of the color fidelity, such as the standard color rendering index (CRI) and its single-figure-of-merit refinements, fail to correctly assess the color rendition properties of illumination, especially for the light sources having spectral power distributions composed of narrow-band components, such as polychromatic light-emitting diode clusters. These metrics (based on the estimation of color shifts for a small number of test color samples) do not account for the ability of the light sources to increase or decrease the chromatic contrast (color saturating or dulling) and clash with the subjective preferences to the color quality of illumination. Supplementing these conventional measures with additional figures of merit accounting for the gamut area of a small number of the test color samples does not completely address this issue. The color rendition vector approach to the color shifts allows for a much more comprehensive assessment of the color rendition properties. In particular, many issues of the color rendition problem can be resolved using the statistical approach based on the color rendition vector sorting for a large number of the test color samples. However despite the availability of advanced measures of color rendition for experts, the need for an improved color rendition metric that could substitute for the outdated CRI still exists. An alternative approach to rating the light sources in terms of color quality is the color rendition engineering. The color rendition engineering allows for the development of light sources having requested or even tunable (and traded off) color rendition properties (color rendition engines). Such color rendition engines can meet individual and group needs in color quality of illumination. When supplemented with the additional functionalities offered by information and communication technology, the color rendition engines could become the preferred tools of the smart lighting revolution.

Two convergent developments are transforming architectural lighting: (1) the advance of solid state lighting technologies and (2) the confirmation that light regulates human circadian, neuroendocrine, and neurobehavioral physiology, thereby influencing health and well-being. Analytic action spectra studies have shown peak sensitivity in the short-wavelength portion of the visible spectrum from 447 to 484 nm for the biological and behavioral effects of light in humans and other mammalian species. These studies led to the discovery of intrinsically photosensitive retinal ganglion cells (ipRGCs) that contain a photopigment named melanopsin. The ipRGCs interconnect with the classical visual rod and cone photoreceptors. Together, all retinal photoreceptors provide input to the retinohypothalamic tract (RHT). The RHT transmits information about environmental light to the central circadian pacemaker as well as many other nonvisual centers in the nervous system. This chapter reviews the fundamental neurophysiology, the clinical and nonclinical therapeutic uses of light, as well as selected examples of published data on the effects of solid state light on human biology and behavior. Both the basic and applied science related to these discoveries are in a nascent stage. As new lighting technologies and applications are developed with the intent to improve human health and well-being, empirical evidence is critically needed to ensure the safety and efficacy of these advances. Collaboration between scientists and engineers across the fields of physics, biomedicine, lighting, and architecture will guide the best use of light for the benefit of humanity.

Good lighting is perhaps the most important, and least understood, design element required to provide supportive environments for all older adults. It is essential to maximize independence (abilities), quality of life, health, wellness and safety. It is critical that homes and public buildings, especially hospitality, medical, and care facilities address not only the impact of normal age-related changes to vision, but also plus the added disability of eye diseases for some, and the important role that light and the visual environment plays in the lives of older people. As people age, they become more dependent on their environment to compensate for their sensory loss, increasing frailty and reduced mobility.The special lighting needs for older adults are not limited to vision, but also include the biological effects of light on personal health. The non-visual or photobiological effects of light include both light entering the eyes, which impacts circadian rhythm (sleep/wake cycle), and light falling on the skin (vitamin D synthesis so that calcium can be absorbed by bones and tissue). Because of the dramatic growth of the 65+ population, we all need to understand the needs of older adults and provide environments designed to meet their (our) needs.

Photobiology is a scientific field that involves biology, physics and chemistry in order to study the effects of optical radiations on living organisms. Lighting systems are sources of artificial optical radiations used primarily to provide light to the human eye in order to enable visual processes in the absence of enough daylight. The first photobiological effect of a visible light source is vision itself.Photobiological safety refers to the undesirable effects of optical radiations on human tissues, especially the skin and the eye. These effects have several possible causes, according to the exposed tissue, the wavelength of the incident radiation, the intensity of the exposure and the duration of the exposure. According to these parameters, the effects can be temporary (reversible), or permanent in the case of severe exposures.This chapter presents an overview of the knowledge concerning the photobiological safety of LEDs and products using LEDs such as solid-state lighting (SSL) products.

The education of our children is one of the most important assignments for society. The facilities where education is conducted have been seen as one important part of a good educational result. In order to create good facilities the lighting situation has for long been seen as one important factor both concerning daylight and electrical lighting. The chapter describes the development of research that initially only could relate to daylight, but with the technological development within lighting was extended to the study of electrical lighting, first the incandescent bulb, then the fluorescent tubes and today the light emitting diodes (LED). The research has for a long time dealt with the visual conditions, but since the late 70s also non-visual aspects has been taken into consideration, not least after the discovery of the ipRGC in the early 21st century. The research in this area has grown very rapidly since and the knowledge has developed. However, much is still to be done. The research is only in the beginning. Results from recent research shows that there is a potential to create better lighting situations with the LED by varying intensity and spectral distribution. Furthermore the distribution of the light should be taken into consideration, and of course the visual aspect must not be neglected. We should also recognize the importance of daylight and how daylight and electrical light should work together for creating good lighting environments in the school.

In the development of the LED light sources that will be introduced here, the adopted color rendering evaluation indexes include Duv (Methods for determining distribution temperature and color temperature or correlated color temperature of light sources, JIS Z (8725–1999)), PS (Light 82–11:895–901, 1998), and FCI (Color Res Appl 32–5:361–371) in addition to the General Color Rendering Index (Ra) (Method of specifying color rendering properties of light sources, JIS Z (8726–1990)). The individual target values are defined to clarify the spectral radiation distribution. This article focuses on the above characteristics: the technical details used in the development of a LED light source called “Favorable Color (Bikou-shoku),” which preferably renders facial skin color, and “Vivid Color (Saikou-shoku),” which vividly renders the true colors of fresh food and plants.

Artificial light sources play an indispensable role to daily life of any human being. Electrical light sources are responsible for an energy consumption of around 1/6 to 1/5 of the worldwide electricity production. Although classic lighting technologies are now mature, the luminous efficiency of the light sources together with their quality of light have not quite reached their limits: there is still room for innovation. Today, there are many opportunities for enhancing not only the efficiency and reliability of lighting systems but also improving the quality of light as seen by the end user. Furthermore, currently the next revolution in lighting is taking place: Solid State Lighting (SSL). In the long-term SSL, inorganic and organic light emitting diodes are now replacing massively legacy technologies. In fact, LEDs, with a continuous growth of their luminous efficiencies, establish themselves as breakthrough solutions.

Lighting is a major global energy consumer, and as such, it causes notable environmental impacts. The environmental impacts of lighting products are researched by life cycle assessment, a method that takes the whole life cycle of the product into account. It is important to study the product life cycle as whole so that the major environmental hot spots are identified and the environmental impacts are not shifted from one stage to another when choosing a different type of technology on the basis of environmental impacts.This chapter presents the basics of the life cycle assessment for evaluating the environmental impacts of light sources in particular. The typical results of the life cycle assessment of light sources in general are presented, but the chapter concentrates only on the lamps used in households. Household lighting is changing in several countries in the world from old, inefficient technologies (incandescent lamp) to more modern light sources of a higher luminous efficacy (CFLs, LED lamps). The change is often justified by environmental reasons. The environmental assessments of household lamps show clearly that the change from incandescent lamps to lamps of higher luminous efficacy is a beneficial decision from the environmental point of view.

Technology, especially artificial light at night (ALAN), often has unexpected impacts on the environment. This chapter addresses both the perception of light by various organisms and the impact of ALAN on flora and fauna. The responses to ALAN are subdivided into the effects of light intensity, color spectra, and duration and timing of illumination. The ways organisms perceive light can be as variable as the habitats they live in. ALAN often interferes with natural light information. It is rarely neutral and has significant impacts beyond human perception. For example, UV light reflection of generative plant parts or the direction of light is used by many organisms as information for foraging, finding spawning sites, or communication. Contemporary outdoor lighting often lacks sustainable planning, even though the protection of species, habitat, and human well-being could be improved by adopting simple technical measures. The increasing use of ALAN with high intensities in the blue part of the spectrum, e.g., fluorescent light and LEDs, is discussed as a critical trend. Blue light is a major circadian signal in higher vertebrates and can substantially impact the orientation of organisms such as numerous insect species. A better understanding of how various types and sources of artificial light, and how organisms perceive ALAN, will be an important step towards more sustainable lighting. Such knowledge is the basis for sustainable lighting planning and the development of solutions to protect biodiversity from the effects of outdoor lighting. Maps that describe the rapid changes in ALAN are urgently needed. In addition, measures are required to reduce the increasing use and intensity of ALAN in more remote areas as signaling thresholds in flora and fauna at night are often close to moonlight intensity and far below streetlight levels.

Artificial light at night is an irreplaceable technology for our society and its activities at nighttime. But this indispensable tool has detrimental side effects, which have only come to light in the past 10–20 years. This chapter reviews ways to implement technology in order to lower the impact of artificial light at night on nature and humans. Further, it provides guidelines for environmental protection and scientific approaches to reduce the increase in light pollution and discusses the urgent need for further research.Measures to prevent obtrusive light and unintentional trespass into homes and natural habitats are mostly simple solutions like shielding luminaires and predominantly require awareness. Shades are another effective tool to reduce trespass from interior lights. Especially in greenhouses, the use of shades significantly reduces the contribution to skyglow. Artificial light should be switched off whenever it is not needed. Smart, flexible lighting systems can help to use artificial light with precision. The choice of the appropriate illumination has to be balanced by the needs for optimal visibility, human well-being, environmental conservation and protection of the night sky. For visibility, conditions comparable to bright moonlit nights (0.3 lx) are sufficient. Low-level streetlights that produce only 1–3 lx at the surface meet the requirement of facial cognition. Although this light level might be too low for road safety, a consideration of maximum illumination levels in street lighting is recommended. The spectral power distribution of illuminants can impact several environmental parameters. For example, illuminants emitting short wavelengths can suppress melatonin in higher vertebrates (including humans), are attracting many insect species, and contribute in skyglow above average. Recent findings in different measures for energy efficiency of illuminants at scotopic or mesopic vision conditions compared to photopic conditions indicate that the assessment of lighting products needs fundamental revision. Further research is crucially needed to create refuges for light-sensitive species at night, to measure the impact of artificial light on nature, and also to monitor the improvements of light pollution-reducing measures.Decrees in various regions have helped to lower the impact of artificial light at night significantly. Measures to reduce the impact of artificial light at night need to be carefully balanced with the surrounding environment. Thoughtful guidelines are crucial to reducing the rapid increase in sky brightness worldwide. These guidelines need to be made accessible for decision makers especially in areas which require new light installations.

Discovered in 1802 by H. Davy, the phenomenon of incandescence is the oldest practical mean of light generation from electricity. In this process, optical emission arises from the constant energy change of electrons in hot solid materials, resulting in a continuous electromagnetic spectrum with a temperature-dependent Planckian wavelength distribution. Incandescence is implemented in lamps by driving an electric current through a thin filament made of tungsten, a refractory metal chosen for its high melting point (3695 K) and low vapor pressure (1 Pa at 3477 K). In order to limit thermal losses and material evaporation, lamps are in most cases filled with a protective gaseous atmosphere, and the tungsten wire is wound into a compact coil or coiled coil configuration. In order to ensure a stable filament structure at high temperature, the metal is doped with potassium or rhenium so as to promote the most favorable crystallographic structure.When operated in a neutral Ar-N₂ or Kr-N₂ atmosphere, the filament temperature lies in the 2600–2800 K range, resulting in 5–8 % energy conversion into visible light. Better performances are obtained with a higher gas fill pressure combined with a tungsten-bromine cycle which prevents tungsten deposition onto the lamp wall. Due to a higher bulb temperature requirement (800–1000 K), halogen lamps are made with a refractory glass bulb in a very compact configuration. With a fill pressure reaching 3 bars, filaments can be operated in the 2800–3200 K range, resulting in 7–13 % energy efficiency.Lamps for general lighting applications are both of the standard and halogen types and are made for an isotropic or a directed emission of light. Standard gas-filled lamps feature a 3.5–20 lm W−1 efficacy with a 1000 h average service life, optimized for the most economical lamp usage. Standard halogen lamps have a 9–25 lm W−1 efficacy with a mean service life reaching up to 10,000 h. Incandescent lamps are also made in a wide variety of configurations with different filament structures and temperatures so as to address specific lighting needs in traffic signals, automotive applications, on stages and studios, for infrared processing, and for instrument calibration. Finally, the most recent and refined lamp designs integrate an infrared mirror for energy conservation, resulting in compact general lighting sources with up to 35 lm W−1 efficacy, or feature a novel wafer-sealed bulb construction and a 5 bar xenon fill yielding 18.8 lm W−1 in a compact low-wattage package for automotive applications.However, incandescent lamps are plagued by two intrinsic limitations, the first of which is a lumen efficacy constrained by the nature of the light emission mechanism and by the maximum filament temperature permitted by technology. The latter constitutes the second intrinsic limitation as the filament life is mostly limited by the formation and growth of local hot spots on the tungsten wire as a result of material evaporation and diffusion. These two limitations result in a relatively poor life-efficacy balance compared to other light source technologies. For this reason, incandescent lamps are being progressively phased out in a number of lighting applications as more efficient technological alternatives emerge.

This chapter provides an overview of the current technology in low-pressure discharge lamps. Because of their dominance in the market place, and production of “white” light, the major part of the chapter is devoted to fluorescent lighting. Fluorescent lamps (FL), contain mercury, a highly efficient emitter of UV radiation, which is then converted to visible radiation by a phosphor coating on the lamp. Although low-pressure sodium (LPS) lamps, which use sodium as the principal radiation source, are more efficient emitters of visible radiation than FL, they are only suitable for limited outdoor applications, due to their predominant yellow colour and hence poor colour rendering. Low pressure discharges in rare gases such as neon have been used for specialist lighting applications, but they are currently being superseded by Light Emitting Diodes (LEDs).

High-pressure mercury-vapor lamps are nowadays available for more than 80 years and will keep importance for the future at least for disinfection applications or lacquer curing. Although the lighting market changed dramatically, Hg lamps are still present; moreover they formed the basis for most of the advanced technologies. Mercury is not only an ingredient in metal-halide lamps but also in many sodium-vapor lamps or in xenon lamps, because of its outstanding material properties.

The striking feature of sodium-vapor lamps is their radiation dominated by the emission of two resonance lines at 589/590 nm. This emission is quite close to the maximum luminous efficiency function at 555 nm and hence contributes effectively to the luminous efficacy. However, due to the limited spectral range of the emission, the spectrum is yellowish and suffers from a poor color rendering.

In the family of high-pressure discharge lamps, up to now high-pressure xenon lamps provide one of the most homogeneous spectral distributions over a broad spectral range of light. This makes them still to preferred light sources in cinema projection, to give one example. Although the discharge plasma consists only of single element, scientific research is addressed to this kind of lamps up to the presence.

Silica metal-halide lamps (MH lamps)MH lampsSilica metal-halide lamps are responsible for the breakthrough of high-pressure discharge lamps in the general lighting market as they combine high-luminous efficacy and good color rendering properties. This was not achieved so far by technologies like high-pressure mercury lamps or sodium-vapor lamps. The progress was possible by the addition of compounds, which provide numerous spectral lines in the visible spectral range.

The evolution of metal halide lamps with ceramic arctubes, known as ceramic metal halide (CMH) lamps, is outlined from concept through prototypes to successful product realization and thence to a firmly established and highly reliable light source technology with a vast array of high-quality products.

“Electrodeless” discharge lamps have several advantages compared to lamps containing electrodes, including longer life, improved lumen maintenance, lamp efficacy, flexibility of lamp design, the use of chemical doses that would interact with electrodes, and improved electrical control. Although the concept of electrode lamps was first demonstrated by Tesla in 1891, the first commercially viable electrodeless fluorescent lamps did not appear in the market until the early 1990s and electrodeless HID lamps a decade later. Prior to that time, the development of electrodeless lamps had been hindered by the lack of inexpensive and efficient electronics. Electrodeless lamps are also finding increasing use as UV sources, particularly so-called excilamps, for degradation of organic pollutants and microbe deactivation.