Color Reproduction and Measurement of 3D Objects
CIE Division 8 Image Technology is responsible for the study of the optical, visual and metrological
aspects of the communication, processing, and reproduction of images, using all types of analogue and
digital imaging devices, storage media, and imaging media. The Division is continually working on
recommendations to improve color image reproduction techniques, including, for example, colorappearance
models, color-difference evaluation and gamut-mapping algorithms. Current technology is
able to transform color images from one digital medium to another, under various viewing conditions,
while maintaining the appearance of each color in the image. This process has been applied in the
graphic arts industry with great success. According to Kaida Xiao, Chair of CIE's Division 8 TC 8-17,
the CIE standard observer and psychophysical data for color-appearance and color-difference modelling
were developed using flat, 2D color samples. He explains that to meet the increasing requirements for
color image reproduction for 3D objects, new research and recommendations
are highly desired.
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Interior Automotive Lighting Control Redefined
In modern car’s interior lighting, tough requirements and rising complexity are a huge challenge.
A new industry consortium was formed to meet this technological challenge and to provide a
comprehensive ecosystem for the new digital LED lighting paradigm. The founding members of
the Open ISELED Alliance are Inova Semiconductors (ISELED "Digital LED" concept and LED
controller), Dominant Opto Technologies (LED manufacturing and packaging), NXP (system
microcontroller), TE Connectivity (system integration and connection technology) and Pforzheim
University (theoretical framework). The alliance recently added LucieLabs (software, firmware),
a French IoT Software startup to its line-up. The goal of all these organizations is to work in
close cooperation to present a complete system solution - a true ecosystem. Roland Neumann,
CTO of Inova Semiconductors introduces the challenges and the worked out innovative solution
that uses a single system controller to individually address up to 4,096 LEDs.
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LpS Gets a Younger Sibling to Foster a Holistic System Approach
For the most part our readers are aware of the fact that the LpS has a
strong focus on the component level, but after the 6th event, the Luger
Research team realized that it was time to find a way to push the more
holistic system approach. After much consideration and careful
planning, the Trends in Lighting (TiL) Forum and Show was initiated
and took place in conjunction with the LpS 2017. Arno Grabher-Meyer,
Editor-in-Chief at LED professional took a close look at both exhibitions
and the lectures to find out what the audience thought of the extension
and broader outlook.
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Avoiding Brightness and Color Mismatch with Proper RGB Gamut Calibration
For well over a decade, proponents of Solid-State Lighting (SSL) have been offering bullish forecasts
concerning the adoption of LEDs for general and specialized lighting applications. Recent years have
seen those rosy predictions come true, with LED lighting now almost completely dominating the market
for new construction, retrofit, and many replacement lighting applications. For many of these
applications accurate color calibration is required. Rood Bouten, CTO at Admesy, explains the reasons
and how to perform a proper RGB gamut calibration.
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The Value of High-End Labs for High Quality Lighting
With the relocation to the Augsburg
site in 2015, the Osram laboratory
equipment includes a number of
integrating spheres of different sizes up
to 3 meters in diameter, several goniophotometers
A/B/C types, a rotary mirror
light distribution meter and a hemispherical
goniometer with a measurement radius of
2.65 meters, optical bench measuring
systems with up to 35 meter measuring
distance, corresponding high-quality
photometric receivers and spectral
radiometers as well as the necessary
components for the electrical operation
of lamps - according to customer or
standardized specifications.
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SoC Technologies in Lighting - Today’s Landscape and Tomorrow's Practices
A system-on-chip (SoC) quite suddenly became an important component in the lighting industry,
fueling IoT innovation and opening new opportunities, while at the same time bringing disruption and
new challenges. With rapid advancements in wireless communication, the impact of connected
technologies on the lighting business will only keep increasing. This means deeper integration with
SoCs and more attention from silicon vendors as they start competing for market share in this
promising segment. But what is the current state of SoC design from the lighting perspective?
Are chipmakers keeping up with the growing expectations for wireless lighting control solutions that
are mature and truly reliable? When developing its complete Bluetooth software stack for professional
lighting, Silvair worked with a number of different SoCs. Therefore, Piotr Winiarczyk, Wireless Solution
Architect, and Szymon Rzadkosz might have found the answers to these questions.
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LED Driver Miniaturization - Opening New Opportunities for Solid State Lighting
While LEDs have significantly improved over the past decade, driver technologies have not kept pace and
are, in some respects, the limiting factors for new applications. Size is a particular issue. Dramatically
increasing the switching frequency helps to reduce size but often causes other issues or is costly. Mickey
Madsen, CEO of Nordic Power Converters, explains how his company has overcome the hurdles and
made it feasible by designing very high frequency LED drivers.
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LED-Retrofit Based on AlGaN/GaN-on-Si Field- Effect Transistor Drivers
Efficient driver technologies for LED systems are still a relevant topic. Several new approaches are
proposed and new technologies are under development. Andreas Zibold, PhD student at the
Fraunhofer Institute for Applied Solid State Physics IAF, and his co-authors, M. Kunzer, R. Reiner,
B. Weiß, P. Waltereit, R. Quay, J. Wagner, and O. Ambacher demonstrate the suitability of AlGaN/GaNon-
Si field effect transistors (FETs) for their use in LED drivers. The transistors are tested in an isolated
buck converter and an efficiency of 86% is measured for the full converter circuit. The driver circuit is
combined with an LED module based on a laser-structured Aluminum Nitride (AlN) ceramic board onto
which 21 high power white-emitting LED chips are mounted. This combination resulted in an LEDRetrofit
lamp with a total light output of 2676 lm at an efficacy level of 119 lm/W. The results compare
favorably to state-of-the-art commercial solutions.
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Trends in Horticulture Lighting
Cree has been a leader in general lighting applications for over 20 years and has customers ranging
from restaurant chains to global government agencies. Paul Scheidt began his career in Cree in 2005,
working on the development of their lighting applications. During this time, he has seen an increase in the
horticulture lighting application. LED professional spoke to Paul Scheidt about horticulture lighting and
what he thinks is behind this recent trend. He also shares his views of what he thinks the future holds for
both Cree and horticulture lighting applications.
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Lighting to Achieve Optimal Appearance
Visual appearance of an object or space depends on the characteristics of the lighting applied.
The objective definition of light quality often doesn’t tell the whole story. Light intensity, its spectral
composition and distribution in space, as well as individual preference, must be considered.
Nevertheless, aiming for the absolute optimum is only recommended when private rooms are
concerned. As visual appearance is key in driving consumer demand, it is important to tune the light
to maximize effectiveness and visual pleasure for most consumers. Markus Reisinger, owner and
CEO of the Lighting Research Studio, discusses this complex situation with examples.
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Issue 63 | Challenges in UV Measurement
Over the past decade UV LEDs have emerged as a highly attractive alternative to conventional
UV emission sources. They are cost effective and energy efficient devices in a small housing.
These advantages allow new fields of applications and access to a larger group of users - even in
the consumer market, e.g. water purification. Dr. Tobias Roesener, Product Manager at Instrument
Systems, explains what makes accurate measurement of UV LEDs so complicated and what the
crucial requirements on the measurement equipment are. In addition, he discusses calibration
and stray light issues.
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Quantum Dot Based White LEDs for General Illumination
Colloidal quantum dot based white LEDs can be integrated into commercial products meeting the
stringent reliability requirements for general illumination and providing LED efficiency gains of 5% to 15%
over commercial phosphor based LEDs at CCT’s ranging from 5000 K to 2700 K. Unlike earlier
demonstrations, the QD material is applied in an on-chip configuration resulting in drop-in fit, form,
and function compatibility to existing LED based luminaires and lamps. Ken T. Shimizu, Director,
Novel Technologies and Devices, Research and Development, M. Böhmer, D. Estrada, S. Gangwal,
S. Grabowski, H. Bechtel, E. Kang, K. J. Vampola, D. Chamberlin, O. B. Shchekin, and J. Bhardwaj
from Lumileds showcase the advantages of on-chip QD LEDs: A commercial lamp at 3000K color
temperature and 90 CRI is substituted with QD based LEDs resulting in a system level efficiency gain up
to 17%, attributed to the reduced blue LED droop from the lower drive current and the lower heat sink
temperature when compared to the standard phosphor based LED lamp output.
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Challenges when Designing LED-Based Illumination Systems in Medical Applications and Diagnostics
LEDs have become indispensable in medical technology and dentistry. But the requirements placed on these lighting products are very high: Minimized size, high, application specific color rendering index, efficient temperature management, usability and excellent disinfection opportunities are all extremely important. Prof. Paola Belloni from the Steinbeis Transfer Center Illumination Optics and Lighting Engineering and Furtwangen University, and Alexander Gärtner from the Faculty of Mechanical and
Medical Engineering of the Furtwangen University discuss the requirements for different applications such as endoscopy, surgeries, dental devices, and photodynamic therapy. Further topics are the development of a self-disinfecting operation interface with edge-lit UV-A LEDs, and a new optimization approach, taking into account the reflection and absorption properties of human tissues.
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Measurement of Angular and Spatial Resolved Spectral Rayfiles
The enhanced complexity of modern lighting systems has increased the importance of realistic light
source models during the optical design process of LED-based luminaires. I. Rotscholl, Research Associate,
K. Trampert, C. Neumann, I. Leopoldo Sayanca from the Karlsruhe Institute of Technology, U. Krüger and
F. Schmidt from the TechnoTeam Bildverarbeitung GmbH, propose a method to enhance the often used LED
light source model “rayfile” towards a “spectral rayfile”. A spectral rayfile would be a model that associates
each ray with its own spectrum and therefore describes varying spectra as a function of angular direction and
spatial starting position. The PMBS (physical motivated basis spectra) method is based on the assumption
that each LED spectrum consists of a weighted sum of individual basis spectra, for instance those of
individual semiconductors and phosphors. There is no need for any special measurement equipment but a
classic nearfield goniophotometer and some off-the-shelf optical filters. This method requires at least one
spectral measurement and just a minimum of goniophotometric measurements with different optical filters.
Finally, the authors demonstrate the potential of this method by applying the concept on a typical LED and
compare the results to the often used Blue/Yellow approach in terms of accuracy and applicability.
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Tech-Talks BREGENZ - Dr. Wilfried Pohl, Research Director, Bartenbach GmbH
Bartenbach is one of the pioneers in light planning and lighting research. Since Christian Bartenbach
Senior founded the engineering office in 1976, the company has been dedicated to light and visual
perception. Several lighting inventions made over the years, can be attributed to Bartenbach.
Dr. Wilfried Pohl, as a member of the Managing Board and Director of Research at Bartenbach GmbH,
has played a substantial role in many developments. LED professional talked with him about
Bartenbach’s history, education in the lighting business, the lighting parameters he deems very
important, the quality of light, "Human Centric Lighting" and "Biodynamic Lighting“, and how LEDs
have changed the light planning and lighting research company, in general.
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