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Highly accurate method for measuring luminous efficacy of LEDs

Date:
September 18, 2015
Source:
Aalto University
Summary:
A new method will help with discovering the most efficient lamps, which may save billions in lighting costs in the future.
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Doctoral students Timo Dönsberg (back) and Tomi Pulli measuring the illuminance of LEDs.
Credit: Image courtesy of Aalto University

The method helps discovering the most efficient lamps, which may save billions in lighting costs in the future.

Researchers at Aalto University and VTT Technical Research Centre of Finland have succeeded in developing a method which helps to improve the relative uncertainty in measuring the luminous efficacy of LEDs from the approximate five percent of today to one per cent in the future.

"Thus far, solutions based on incandescent lamps have been used in photometry, i.e. in measuring light detected by the human eye," explains Tomi Pulli, a doctoral student at Aalto University.

"The photometers that lamp manufacturers use for calibrating their devices have been produced and calibrated for incandescent lamps, which results in errors when measuring the efficacy of LEDs. In our research, we used a LED lamp with a well-defined spectrum and a PQED detector, which we developed together with VTT MIKES Metrology and European partners, and whose spectral responsivity can be determined highly accurately. Therefore, there was no need for the problematic optical filters used in applications based on incandescent lamps. Indeed, accurately determining and analysing the spectrum of the LED was the most challenging and crucial part of the research," he reveals.

From a dot to a sphere

The detector used in measurements by Pulli and his co-researchers measures the illuminance of LEDs in a very small area. According to Professor Erkki Ikonen, the head of research, the next step will be to move onto measurements corresponding to real-life conditions for lighting.

"LED lamps emit light to all directions. In order to measure the luminous efficacy, we thus use a device called an integrated sphere, which takes into account light coming from different directions, he specifies and reminds us that the history of LEDs is still short when compared to incandescent and fluorescent lamps. Therefore, there is still little information available on their actual efficacy and ageing properties. Indeed, it is essential to determine luminous efficacy as accurately as possible so that such lamps can be introduced in the market that transform as much electrical energy into light useful to the human eye as possible.

"So far, the portion of LEDs has been merely around ten per cent globally, but the amount is increasing at a rapid pace," Ikonen explains.

Lighting amounts to approximately 20 per cent of the electricity consumption in the world. Once the share of LEDs increases close to 50 per cent, an improvement of as little as one percent in the accuracy of measuring the luminous efficacy of the lamps introduced in the market will mean saving billions of euros each year.


Story Source:

Materials provided by Aalto University. Note: Content may be edited for style and length.


Journal Reference:

  1. Tomi Pulli, Timo Dönsberg, Tuomas Poikonen, Farshid Manoocheri, Petri Kärhä, Erkki Ikonen. Advantages of white LED lamps and new detector technology in photometry. Light: Science & Applications, 2015; 4 (9): e332 DOI: 10.1038/lsa.2015.105

Cite This Page:

Aalto University. "Highly accurate method for measuring luminous efficacy of LEDs." ScienceDaily. ScienceDaily, 18 September 2015. <www.sciencedaily.com/releases/2015/09/150918083129.htm>.
Aalto University. (2015, September 18). Highly accurate method for measuring luminous efficacy of LEDs. ScienceDaily. Retrieved May 29, 2017 from www.sciencedaily.com/releases/2015/09/150918083129.htm
Aalto University. "Highly accurate method for measuring luminous efficacy of LEDs." ScienceDaily. www.sciencedaily.com/releases/2015/09/150918083129.htm (accessed May 29, 2017).

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