Articles & Interviews

Discomfort Caused by Glare from Luminaires with a Non-Uniform Source Luminance

Glare and the resulting discomfort are a persistent issue in lighting that became even bigger with the introduction with LEDs as a light source. While the UGR method is well established, it is sometimes heavily discussed if it is appropriate for SSL. The limitations of the UGR method need to be understood. Peter Thorns BSc(Hons), CEng, FCIBSE, FSLL, explains these limitations and consequently describes the research and how to apply correction measures. Read more »

LpR Article | Jun 20, 2016

Discomfort Glare Perception of Non-Uniform Light Sources in an Office Setting

LED based luminaires with different luminance patterns and recently, with increasingly non-uniform luminance patterns are becoming mainstream. This trend makes discomfort due to glare an important topic. Based on an office setting and the comparison of results from three different regions, L. M. Geerdinck, J. R. Van Gheluwe and M.C.J.M. Vissenberg from Philips Research have reviewed the currently used formulae to predict discomfort glare to ascertain if they are still valid. Read more »

LpR Article | Jun 08, 2016

DMI Specification Defines Electrical Interface between LED Drivers and Modules

Enabling LED modules and LED drivers to be fully interchangeable at the component level requires a specification for the electrical interface between the driver and module (DMI). Arnulf Rupp of Osram GmbH, a member of both the Zhaga Consortium and MD-SIG, explains the role of both organizations in developing and implementing a consistent, easy to use, cross-vendor DMI specification. Read more »

LpR Article | Sep 05, 2016

Easing Lighting System Design with Online Tools

The technical intricacies of an LED lighting system design can be quite complicated. The interdependencies of design parameters such as light source flux, efficacy, lumen maintenance, drive current, series/parallel light source layout, compatible optics, compatible drivers, thermal dissipation and others make the calculation of system performance a laborious process if performed manually. One simple change in one parameter could potentially force the lighting designer to consult the datasheet for every other component considered in the design in order to calculate the impact on the system as a whole. Patrick Durand, Worldwide Technical Director, Future Lighting Solutions demonstrates the capabilities of modern online tools to solve these problems giving a typical application example based on the Future Lighting System Creator (LSC). Read more »

Electrical Over Stress - How to Prevent an LED Failing Earlier than Expected

Article from LpR 66, page 70: While LEDS are, in general, very robust, failures still happen due to electrical over stress. Mauro Ceresa, EMEA Field Application Engineer Manager at Cree, will cover all aspects related to electrical over stress, or when an LED fails due to being subjected to a voltage beyond its specification limits. He will explain why the failure occurs and how to prevent this from happening. The article will explain the fundamental aspects of a good PCB layout design and how this is linked to the longevity of an LED. Read more »

LpR Article | Trends | Jun 06, 2016

Embedded Lighting - Developing New Lighting Applications for Modern Architectural Projects by Philips Lighting

When the era of LED lighting started, everybody talked about the new age of lighting with new opportunities. While many lighting concepts are still pure replacements of the conventional light sources, with the maturation of this technology, more and more new concepts are realized, and the future perspectives are even more exciting. Brad Koerner, Venture Manager - Philips Luminous Patterns at Philips Lighting, shows examples, explains why such new concepts are desirable, and discusses which technologies support the introduction of new lighting applications. Read more »

LpR Article | Jul 01, 2016

EMI Problems in TRIAC Dimmable LED Drivers by RECOM Lighting

TRIAC dimming adds a dimension to Power Factor (PF) and Total Harmonic Distortion (THD) that is rarely defined by LED driver manufacturers. Bianca Aichinger, Product Marketing Manager at RECOM Lighting, examines the relationship between PF, THD and harmonics and explains why this relationship can change as soon as the LEDs are dimmed, thus causing increased EMI and undesirable visible effects such as LED flashing and flicker. The European standards for EMC and Harmonics are only specified for full load and in the non-dimmed condition. In practice, there are often dimmer/driver/LED load conditions which may meet the regulations when undimmed, but fail significantly if dimming is used. Read more »

Smart Lighting + IoT | Outdoor Applications | Resources | LpR Article | May 16, 2017

Enabling Total Control in the Next Generation of Outdoor Lighting

Outdoor lighting is certainly one of the applications with the greatest potential for energy saving. Although many approaches are discussed, they all end up with a smart lighting solution. In order to accommodate this, intelligent software and electronics are required as well as standardized, robust interfaces. Ronald Weber, Global Industry Manager, Building Automation and Benjamin Nelson, Business Development Manager, Intelligent Buildings, both from TE Connectivity, present a Zhaga compliant solution. Read more »

LpR Article | Jul 04, 2016

Energy Efficiency and Thermal Simulations of a Retrofit LED Light Bulb by the University of Turku

Mika Maaspuro and Aulis Tuominen from the University of Turku investigated the energy efficiency of a LED driver mounted inside a retrofit light. The heat generation of the LEDs and the driver of the light bulb have been simulated and measured. A thermal model for the light bulb has been created and simulated using a Finite-Element-Method (FEM) software. Parameters of the model have been adjusted to match the temperature measurements which have been done with IR-camera and thermocouples. Read more »

LpR Article | Jul 04, 2016

Energy Efficiency and Thermal Simulations of a Retrofit LED Light Bulb by the University of Turku

Enhancing the LED Experience - UI & UX as Success Factors for IoT Based Lighting Controls

As LED lighting systems become part of the Internet of Things, getting the interface right is essential if all of the potential benefits are to be realized. Karl Jónsson and Christian Moormann of Tridonic explain why UI and UX are crucial for the acceptance of the “Internet of Things”, give design hints and describe what this type of user interface that accommodates scalability, simplicity and ease of handling could look like. The authors also discuss examples based on a system Tridonic pre-launched in 2016. Read more »

Resources | LpR Article | Horticulture | Applications | Mar 28, 2019

Enriching Horticultural Lighting for Faster Growth and Better Crops

Horticulture lighting is no new lighting application, but it gained momentum with the introduction and evolution of LED lighting, and it is meanwhile one of the fastest growing markets in lighting. Dr. Richard Blakey, Application Engineer at Würth Elektronik eiSos, explains how LED-based horticultural lighting can deliver even bigger advantages for commercial growers by introducing additional wavelengths that increase photosynthetic response - like Würth Elektronik's new members of the WL-SMDC SMD Mono-Color Ceramic LED Waterclear family that is used as a reference in the article. Read more »

Evaluating Performance of LED-Based Luminaires

LpR 69 Article, page 48: The wide spread of performance data supplied by manufacturers make it difficult for the professional user to reach an “apple-to-apple” comparison, especially if the data is not based on standardized metrics. This is however critical for the preparation of lighting projects or tender specifications. Experts from LightingEurope have therefore developed a guidance document which recommends a fixed set of performance data for LED based luminaires, with particular emphasis to the useful life and the data which is necessary for lighting application design. Read more »

Flex LED Based Smart Light System for Healing of Chronic Wounds

LpR 71 Article - page 48: Chronic wounds are notoriously challenging to treat, because they do not follow the typical healing process or time-frame. The resulting burden is significant, affecting over 40 million patients. Blue light is known for its anti-microbial and anti-inflammatory effects in the initial stages of the healing process. David Kallweit, researcher at CSEM, reports about the joint development of a chronic wound treatment device with their MEDILIGHT partners, URGO RID, University of Heidelberg, SignalGenerix, Microsemi, Technical University of Berlin, and Amires. He furthermore shows how it works and discusses future prospects. Read more »

LpR Article | Research | Jun 07, 2016

Flexible OLEDs for Lighting Applications by the Holst Centre

While OLEDs already have successfully found their way into display applications, the breakthrough in lighting applications is still pending. The reasons are diverse, but cost is one major point. Another reason is the current edge of inorganic LEDs giving reasonable design opportunities in many standard applications. However, there are applications where OLEDs could score, especially the flexible OLEDs. But even these OLEDs need to become cheaper to be applied widely. The Holst Centre and partners aim to develop generic technologies for large area flexible OLEDs which can be processed with roll-to-roll (R2R) technology. Process Engineer Tansim Baig gives an example and an overview of the current status of the development. Read more »

LpR Article | Research | Aug 09, 2016

Flicker Beyond Perception Limits - A Summary of Lesser Known Research Results

Since the introduction of fluorescent lamps, the lighting industry knows about flicker issues. However, many aspects are still unclear. Especially effects beyond the flicker fusion threshold are mostly ignored, and sometimes even denied. Dr. Walter Werner, CEO of Werner Consulting, gives a summary of research results indicating that further research is needed and that for high quality lighting very likely a much higher PWM modulation frequency is required. Read more »

Resources | LpR Article | Automotive | Driver IC | Jan 15, 2018

Flicker-Free Control of Individual LEDs in Matrix Headlights

LEDs combine design flexibility with practical, robust circuitry, enabling automotive designers to produce striking headlight designs matched by exceptionally long life and performance. Keith Szolusha, Sr. Design Leader for LED driver products at Linear Technology, and now part of Analog Devices explains how automobile designers are increasingly incorporating LEDs in lighting because they can be arranged in distinctive eye-catching designs - helping distinguish new models from old, or high end from economy. Read more »

Trends | Smart Lighting + IoT | Resources | LpR Article | Nov 28, 2016

Flicker: Standards and Test Methods

Much has been written and said about Temporal Light Artifacts (TLAs). What is essential about TLAs is that they consist of flicker and/or stroboscopic effects induced by a light stimulus whose luminance or spectral distribution fluctuates with time and causes undesired changes in visual perception for an observer in a certain environment. Walter Parmiami, Senior Engineer at UL International Italia S.r.l., discusses the current status of regulations and measurement standards and proposes a certification to help manufacturers to generate user confidence, and consumers and specifiers to find the right product for an application Read more »

LpR Article | Jul 04, 2016

Focus Tunable Lenses for LED Lighting by Optotune AG

Focus tunable lenses open up new possibilities in the design of LED based luminaires. With these shape changing lenses, the beam angle of a spotlight can be flexibly adjusted while keeping the efficiency on a constant, high level. Compact solutions combining a floodlight and a spotlight in one product can therefore be realized. This innovative technology reduces complexity and offers more flexibility in lighting design, especially for changing environments like museums, and shops. Joerg Wertli from Optotune AG demonstrates a very interesting technology for these applications. Read more »

From Component to System, Andreas Weisl, CEO at Seoul Semiconductor Europe GmbH

The history of Light-Emitting Diodes (LED) is quite short compared with some other electronic device industries. However, it has changed and revolutionized the entire world of light within a very short period of time. The history of Light-Emitting Diodes (LED) is quite short compared with some other electronic device industries. However, it has changed and revolutionized the entire world of light within a very short period of time. Read more »

Full-Color InGaN/AlGaN Nanowire Light-Emitting Diodes for SSL and Displays

III-nitride based nanowire light-emitting diodes (LEDs) have received a staggering response as a future candidate for solid-state lighting and full-color displays due to their unique and exceptional features including drastically reduced polarization fields, dislocation densities as well as the associated quantum confined Stark effect (QCSE) on account of their effective strain relaxation. Moab Rajan Philip and his supervisor Dr. Hieu P Nguyen in the Nano-Optoelectronic Materials and Devices Laboratory at the New Jersey Institute of Technology (NJIT) present astonishing ideas to fabricate and control the color emission of III-nitride nanowire LEDs via molecular beam epitaxy (MBE) growth techniques. The advantage of such LEDs and their characteristics is also discussed. Read more »

Resources | LpR Article | Quality | Optics | Oct 31, 2017

Glare Reduction Made Easy

A pleasant lighting atmosphere due to low glare at the workstation is not only pleasant and performance-enhancing, but also legally required according to EU standard EN 12464-1. But what does “glaring” mean here? Dr. Claudius Noack, Technical Director at NORKA Leuchten, explains if luminaires with the same luminous flux are glaring to the same degree and if the same luminaires are glaring to the same degree at different workstations. He answers the questions of what a manufacturer does and if manufacturers are lying to themselves and therefore to their customers when providing information on the glare rating. Read more »

Quality | LpR Article

Guidance on Specifying Solid State Lighting Luminaires

Certification marks of renowned test institutes are useful tools for end users to easily estimate the quality of a product. They are also a good marketing tool for manufacturers to generate user trust and confidence in a product or the brand. The authors, Jaap Nuesink and Michael Schoof from DEKRA Certification B.V. explain what is needed and which parameters have to be covered in order to be certified, ending up in a guideline of how to qualify for the DEKRA Solid State Lighting Certification Mark. Read more »

LpR Article | Jun 29, 2016

Handheld Photometry Supports LED Lighting Design

With SSL new dimensions were introduced to light measurement, especially concerning handheld light measurement tools. Norbert Harkam, General Manager at SalesLink GmbH, a Representative of UPRtek, explains what criteria have to be considered and what the requirements of a handheld photometer are. Read more »

Resources | LpR Article | Research | Environment | Mar 26, 2019

Hazard or Hope? LEDs and Wildlife

LpR 70 Article, page 52: The introduction and widespread uptake of LEDs as outdoor lighting has caused no small amount of concern amongst conservation biologists. The prevailing impression that LEDs are always blue-white is well founded as adoption of LEDs for streetlights were invariably high color temperatures and with the deterioration of phosphors the blue wavelengths penetrated even more. But LEDs do have characteristics that differentiate them from other light sources and may allow for the reduction of environmental effects of lighting on species and habitats: direction, duration, intensity, and spectrum. Travis Longcore, Assistant Professor at the University of Southern California's School of Architecture, sheds light on all these aspects. Read more »

Healthy Light - LED Technology for Health and Care Applications

The right light, at any time during the day or night, is absolutely essential for health and well-being especially in health and care applications. Peter Haumer, Head of Technical Sales at Lumitech/Kiteo reveals why, besides full spectrum and high color rendering, mimicking real daylight conditions with extended daylight curves, a direct and an indirect component (CCT 1.800–16.000 K), are essential. The article discusses the benefits that can be derived from special colors for medical staff, patients and residents. Read more »

Hermetic Polymer-Free White LEDs for Harsh Environments

AlGaInN-based white LED can easily achieve lifetimes of up to 100,000 h depending on junction temperature and current density. However, state of the art silicone encapsulated LEDs with powder-based phosphors reveal a strong dependence of field lifetimes on environmental conditions such as humidity, corrosive gas and air pollutant exposure. Dr. Michael Kunzer, Group Leader LED Modules at Fraunhofer Institute for Applied Solid State Physics and his colleagues, Ralf Schmidt, Andreas Zibold, Vasileios Georgiou-Sarlikiotis, Michael Arnold and Isabel Kinski propose luminescent ceramics as an interesting alternative to polymer-dispersed phosphors. This provides entirely new opportunities for the manufacturing of white LEDs. The authors explain the properties and advantage of this hermetic, light converting cap material and how to completely avoid polymers. Read more »

LpR Article | Technologies | Jun 20, 2016

High Color-Rendering, Full-Visible-Spectrum LEDs by Soraa

The first wave of conventional white LEDs primarily focused on lumens per Watt. These LEDs were based on phosphor down-conversion using primary blue “pump” emission. Currently LEDs are catching up in regards to light quality using different approaches. Aurelien David, Senior Principal Scientist and Mike Krames, Chief Technology Officer at Soraa explain their technology approach of violet-pumped, full-visible-spectrum LEDs, and the interrelated challenges and advantages. Read more »

LpR Article | Technologies | Medical | Aug 11, 2016

High-End White Light Sources Fiber Optics Technology for Medical Applications

Often technologies that are too expensive for the mass market at the beginning are already adopted in medical applications. When reaching a certain level of maturity, costs usually become more reasonable and adaptations for the consumer market begins. Holger Laabs, Oliver Mehl and Henning Rehn from Osram GmbH present a light source technology and its prerequisites for fiber optics that could become one of these technologies. Read more »

LpR Article | Technologies | Jun 28, 2016

High-Index Nanocrystals - Key to Next Generation Advancements in Lighting

Solid-State Lighting is destined to be a next generation lighting option. LEDs have already entered main stream applications and OLED technology has advanced greatly in the past few years in terms of efficacy and performance. Both technologies need to continue to improve performance to achieve high market acceptance. Dr. Gregory Cooper, Chief Technology Officer and Founder of Pixelligent Technologies LLC, illustrates how LED and OLED technology can advance to the next level by incorporating nanomaterials into existing packaging. Read more »