Technologies | Research | Health & Environment | Human Centric Lighting | Color Perception | Oct 18, 2019

Study Reveals How Age Affects Perception of White LED Light

Although LEDs are increasingly used in low-energy lighting and displays, consumers sometimes find their light harsh or unpleasant. Findings from a new study point to the need to take age-related perception differences into account when designing white LED lighting that is more pleasing to the eye.

Fact Box:
A new study reveals that age can affect the perceived tint of white light. This photo shows a very large difference in tint between different spots, which is representative of what the researchers found in the study. Though not representative of what all observe, viewers of different ages disagree on which of these sources appears "most white" when compared to a reference source (here, the digital camera taking the photo selected the third spot for white balance).

"Our study revealed that the amount of short-wavelength light a source emits together with the viewer's age may lead to very different perceptions of a white light," said the research team leader Aurelien David of Soraa Inc., Fremont, Calif., U.S.A. "LED light sources exacerbate this effect, because their emission often features large peaks of blue or violet radiation."

The researchers report the new findings in The Optical Society (OSA) journal Optics Express. They point out that although conventional colorimetry assumes all users have the same visual response, more recently developed models for color perception take age-related effects into account and can be used to predict and help mitigate differences in color perception.

"Today, the color of light is defined by standards based on decades-old science that doesn't accurately predict color perception," said David. "This presents a hurdle to designing better light sources that would minimize inter-user variation and aid in the increased use of LED technology."

Testing white light perception

For the study, viewers were shown several nearly white LED sources with various emission spectra and asked to rank their perceived tint compared to that of a reference white light. The test sources were part of the researchers' efforts to develop a more sleep-friendly light source. They featured a specialized emission spectrum in which the short-wavelength blue light, which may affect sleep, was replaced with shorter-wavelength violet light that maintains the light's white color.

"According to standard colorimetry methods, all users should have the same perception for a certain LED source," said David. "However, we found large variations between viewers. Some thought a given source appeared very pink, whereas others thought the same source appeared very green."

Analysis of these findings revealed that the perception variations were largely driven by age. Turning to modern color science, the researchers were able to derive a perception model that accurately accounted for the inter-user perception variation they observed.

"The perceived tint of these unusual LED sources is heavily influenced by the viewer's sensitivity in the violet range, which is strongly age-dependent," explained David. "Although others have observed similar variations in white-LED perception, the effect was especially easy to see because these special LEDs exacerbate it."

The researchers also showed that the age-dependent perception effects are present in conventional LEDs such as those used both in lighting and display applications. This means that two conventional LED sources that supposedly have the same white color may appear very different to a given observer.

Defining new color standards

"By using modern colorimetry, the design of future LED sources could be tailored to minimize inter-viewer discrepancies," said David. "Manufacturers could use this modern framework to design lighting that is more robust against age-driven variations."

The researchers note that having a standard calculation for age-dependent colorimetric quantities would help manufacturers and other stakeholders incorporate age-dependent effects into the design of future LED emitters.

"We should make sure that such age-related effects do not hinder the advancement of LED technology, since they can be addressed with scientific tools that are already available, albeit not commonly used," said David.

Acknowledgements:

The researchers acknowledge that all 64 subjects used for this research were all employees of Soraa Inc. who volunteered to participate in the study.

References:

Paper: A. David, D. Sahlhoff, M. Wisser, "Human perception of light chromaticity: short-wavelength effects in spectra with low circadian stimulation, and broader implications for general LED sources," Opt. Express, 27, 22, 31553-31566 (2019).
DOI: https://doi.org/10.1364/OE.27.031553

About Optics Express:

Optics Express reports on scientific and technology innovations in all aspects of optics and photonics. The bi-weekly journal provides rapid publication of original, peer-reviewed papers. It is published by The Optical Society (OSA) and led by Editor-in-Chief James Leger of the University of Minnesota, USA. Optics Express is an open-access journal and is available at no cost to readers online at OSA Publishing.

About The Optical Society:

Founded in 1916, The Optical Society (OSA) is the leading professional organization for scientists, engineers, students and business leaders who fuel discoveries, shape real-life applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership initiatives, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of optics and photonics experts. For more information, visit www.osa.org

FEATURED

Epoxy Features Very Low Coefficient of Thermal Expansion

Epoxy Features Very Low Coefficient of Thermal Expansion Master Bond EP30LTE-2 has been developed for joining dissimilar substrates exposed to thermally or mechanically induced stresses. It can be used for sealing, coating and encapsulating, especially for small to medium sized castings where a very low coefficient of thermal expansion (CTE) is required. Read more »

FEATURED

New BJB LED Connector for Linear LED Modules: Book 21 Compliant

New BJB LED Connector for Linear LED Modules: Book 21 Compliant Lampholders were standard in older, traditional lighting systems. Modern LED fixtures that utilize non-replaceable LEDs create several assembly and field-replacement disadvantages. Zhaga Book 21 addresses these shortcomings by standardizing linear 'socketable' LED modules. In accordance with Book ... Read more »

FEATURED

EzyLED™ Now Stocked at Digi-Key

EzyLED™ Now Stocked at Digi-Key American Bright, a global LED lighting solutions manufacturer, announced a series of EzyLED 3030. American Bright's EzyLED™ is a proprietary LED device with a built-in IC. This patented design drastically reduces the need for additional circuitry and other on-board components making it the ideal ... Read more »

FEATURED

Cree Expands Design Possibilities for Architectural Lighting with the Worldwide Proven CLQ6A LED

Cree Expands Design Possibilities for Architectural Lighting with the Worldwide Proven CLQ6A LED These SMD LEDs are packaged in an industry standard PLCC8 package. These high performance 4 color SMT LEDs are designed to work in a wide range of applications. A wide viewing angle and high brightness make these LEDs suitable for signage applications. Read more »

FEATURED

Measuring the Oxygen Content of Blood with LEDs

Measuring the Oxygen Content of Blood with LEDs Pulse oximetry is a non-invasive method for determining haemoglobin (Hb) saturation through oxygen in the blood and heart frequency. It uses the fact that oxygen-rich and oxygen-poor haemoglobin absorb red and infrared light differently. In order to measure the oxygen content reliably, LEDs with ... Read more »

EDITORIAL

LpS/TiL 2019 - Europe's Foremost Lighting Conference Discussed Latest Lighting Trends

LpS/TiL 2019 - Europe's Foremost Lighting Conference Discussed Latest Lighting Trends Last week saw the co-hosted LED professional Symposium +Expo (LpS), Trends in Lighting Forum &Show (TiL) and for the first time the Digital Addressable Lighting Interface (DALI) Summit return to Bregenz, Austria. The three international conference and exhibition events were carefully curated to ... Read more »

EDITORIAL

The 2019 LpS & TiL Award Winners: Celebrating the Complete Spectrum of Light

The 2019 LpS & TiL Award Winners: Celebrating the Complete Spectrum of Light It is a great pleasure for the LpS and TiL organization committee to announce the award winners for 2019. For the second time in a row, after the traditional cruise on the lake from Bregenz to Lindau, the gala dinner at the Eilgut Halle has proven to being a great place for the LpS & TiL award ... Read more »

page_peel