PDF《Indirect焖licker燩erception:?》

12 ??2016?Rensselaer?Polytechnic?Institute.?All?rights?reserved. Which?Flicker?Metrics?are? Most?Useful??(cont'd.) ? Flicker?index?(Eastman?and?Campbell?1952) ? Has?historically?been?reported?for?many?types?of?lamps ? Like?percent?flicker,?does?not?incorporate?frequency ? Fourier\based?metrics?(e.g.,?Perz et?al.?2015) ? Acknowledges?that?stroboscopic?effects?ultimately?reduce?to?a? spatial?frequency??visibility?problem ? Fourier\based?approaches?should offer?the?most?complete?predictive metric

13 ??2016?Rensselaer?Polytechnic?Institute.?All?rights?reserved. Comparing?Metrics

14 ? Bullough?and?Marcus?(2015)?evaluated?different?waveform?shapes? and?duty?cycle?(60%\90%?or?100%)?at?100,?120,?300?and?1000?Hz ? Responses?to?waving?a?light\colored?rod?against?a?dark? background,?and?to?a?metronome?operating??at?208?bpm were? assessed [all?waveforms?above:?100%?flicker] ??2016?Rensselaer?Polytechnic?Institute.?All?rights?reserved. Experimental?Results

15 ? Percent?flicker?and?flicker?index?values?cannot?be?compared?across?different? frequencies;

?Perz et?al.?(2015)?developed?a?stroboscopic?visibility?measure? (SVM)?based?on?Fourier?analysis,?which?is?independent?of?frequency?properties ? In?their?study?of?responses?to?100\1000?Hz?flicker?varying?in?waveform?shape? and?duty?cycle?(Bullough?and?Marcus?2015),?detection?and?acceptability?were? rectified?at?least?as?well?as?SVM?by?a?modified?flicker?index?defined?as:? ? Modified?flicker?index?=?Flicker?index?* 100/f,?where?f is?the?frequency?(Hz) ??2016?Rensselaer?Polytechnic?Institute.?All?rights?reserved. Implications?of?Results ? Data?from?Bullough and?Marcus?(2015)?have?several? implications?for?specifications?to?limit?perception?of? stroboscopic?effects: ? Metrics?based?on?flicker?index?(such?as?modified?flicker?index)? are?superior?to?those?based?on?percent?flicker,?such?as?IEEE? 1789?and?California?Title?24 ? Whether?percent?flicker?or?flicker? index?is?used?in?a?specification?for? stroboscopic?effects,?it?should?be? proportional?to?the?frequency,?not? to?the?logarithm?of?the?frequency? (such?as?in?IEEE?1789)

16 ??2016?Rensselaer?Polytechnic?Institute.?All?rights?reserved. Limitations?of? Flicker?Index\Based?Metrics ? All?waveforms?studied?thus?far?regarding?the?perception? of?stroboscopic?effects?have?had?one?primary?frequency? component?(100?Hz,?120?Hz,?etc.) ? When?two?or?more?frequency?components?exist? simultaneously?within?a?waveform?(e.g.,?both?120?Hz? and?240?Hz)?and?with?similar?strength,?defining?the? primary?frequency?is?not?straightforward ? Presents?difficulties?for?specifying?the?modified?flicker?index ? For?such?cases,?Fourier\based?approaches?to?specifying? flicker?for?stroboscopic?effect?perception?may?be?most? appropriate

17 ??2016?Rensselaer?Polytechnic?Institute.?All?rights?reserved. Application?Dependence?of?the? Perception?of?Stroboscopic?Effects

18 ? Horizontal?illuminance?on?desktop:? 300?lx ? Light\colored?surfaces ? Flicker?frequencies?(always?at?33%? flicker,?0.17?flicker?index): ? 100,?200,?500,?1000?Hz ? Questions:? ? Stroboscopic?effects?detected?while? waving?white?rod? ? Stroboscopic?effects?detected?with? metronome?(208?bpm)? ? Acceptability?of?any?flicker?from?lighting? +2 Very?acceptable +1? Somewhat?acceptable

0 Neither?acceptable nor?unacceptable \1 Somewhat unacceptable \2? Very?unacceptable ??2016?Rensselaer?Polytechnic?Institute.?All?rights?reserved. Experimental?Results

19 Detection?Acceptability 162?666??????985????(all?Hz)86???? 125????(all?Hz) Thresholds?for?detection?(50%)?and?for?acceptability?(rating=0)?occurred?at?systematically?lower? frequencies?with?lower?contrast?and?slower?movement?speed.?In?other?words,?sensitivity?to? stroboscopic?effects?was?reduced?under?the?tested?conditions?relative?to?those?used?to?develop? the?ASSIST?predictive?model?(2012) ??2016?Rensselaer?Polytechnic?Institute.?All?rights?reserved. Classification?of?Lighting? Applications