Browsing by Author "Mantela, V."
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- Digital implementations for determination of temporal light artefacts of LED luminaires
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2024-11) Mantela, V.; Nordlund, R.; Askola, J.; Kärhä, P.; Ikonen, E.Flicker and stroboscopic effects caused by a temporally modulated light source may be harmful for the human visual system. Standardized measurement methods have been developed for the related temporal light artefacts of LED luminaires. It was found out that the performance of the International Electrotechnical Commission (IEC) recommended flickermeter implementation is highly dependent on sampling frequency. Novel digital implementations for the flickermeter and stroboscopic effect visibility measure (SVM) were created to remove any inaccuracies. The performance of the novel Aalto implementations does not depend on the sampling frequency when running the test waveforms of the IEC standard through the implementations. As compared with the IEC recommended digital implementations, Aalto flickermeter decreases the average error related to the test waveforms from −0.05 to +0.003, and Aalto SVM meter also decreases the average error by almost two orders of magnitude. - General V(λ) mismatch index: History, current state and new ideas
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2023-06-01) Krüger, U.; Ferrero, A.; Thorseth, A.; Mantela, V.; Sperling, A.The general V(λ) mismatch index f1′ specifies the mismatch between the relative spectral responsivity of a photometer, and the spectral luminous efficiency function for photopic vision, V(λ). A short review of its historical development explains the reasons for the current definition and which adjustments may be helpful in the future. The properties of the current definition are described in detail. It is very likely that photometers will be calibrated with a white light-emitting diode (LED) light source as the reference in the future. This might involve the need for a more appropriate definition of the general V(λ) mismatch index, either by using a different normalisation in f1′ for the relative spectral responsivity of the photometer or by introducing a different type of function for assessing the mismatch. On the other hand, the measurement of coloured LEDs is also becoming increasingly important. So, is a single general mismatch index for white and coloured light sources sufficient? - Improvement of temporal light artefact effects in commercial LED lamps
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2024-11) Mantela, V.; Nordlund, R.; Askola, J.; Kärhä, P.; Dekker, P.; Ikonen, E.Temporal light modulation and its potential adverse visual effects on human observers, collectively known as temporal light artefacts (TLAs), have been limited by the European Union Ecodesign regulation. Limitations on two key TLA metrics, flicker and stroboscopic effect, were introduced in September 2021. This study analyses the impact of this regulation on commercial LED lamps by measuring multiple different consumer-grade LED E27 retrofit lamps by several manufacturers before and after the regulation. The lamps purchased after the Ecodesign regulation seem to favour a certain type of LED driver that provides the best TLA behaviour of all lamp types. The regulation, with respect to TLA, has resulted in the replacement of ill-behaving lamp types in the market by newer lamps with better TLA characteristics.