Analysis of P st LM and stroboscopic visibility measure variations due to different measurement conditions

Abstract

Temporal light artefacts (TLAs) are undesired visual perceptual effects, caused by temporal light modulations (TLMs), which commonly exist in lighting systems, especially LED lighting systems. Accurate measurement of TLM and evaluation of TLA metrics, specifically the stroboscopic visibility measure (SVM) and the short-term flicker indicator (P_st^LM), are required by certain product safety regulations with limit values specified. In this study, we investigated the impact of different measurement conditions on the P_st^LM and SVM for the measured waveforms of 11 different commercial lamps. It is found that the sampling rate, filter setting and measurement duration are critical for P_st^LM. Anti-aliasing filters are essential for P_st^LM measurements, but for some waveforms, P_st^LM results may be inaccurate even under the conditions recommended by the International Electrotechnical Commission. The variation of P_st^LM at different sampling rates is slightly larger when using analogue filters compared to digital filters. For SVM, different sampling rates and measurement durations have a significant impact on the results. It is recommended to use a combination of zero-padding and quadratic interpolation (ZPQI method) to obtain accurate and consistent SVM results. Overall, the use of different filtering methods (digital or physical) has little effect on the results of the P_st^LM and SVM calculations, higher-order filters are recommended.