Visibility Model Of Phantom Array Effect Caused By Time Modulated LEDs

LEDs are applied into various fields,such as general lighting and road lighting,because of their low power consumption,long service life,environmental protection and so on.There are a large number of methods to adjust the luminance of LEDs.The method which is most widely used in the industrial production is pulse width modulation(PWM).However,PWM could induce the fluctuation of light intensity and thus result in temporal light artefacts,such as flicker,the stroboscopic effect and the phantom array effect.This paper is dedicated in studying the phantom array effect of temporally modulated LEDs.The visibility of the phantom array effect was investigated using the psychological evaluation methods in different cases.The LEDs were driven by a programmable waveform generator.Firstly,the influence of the frequency and waveform of modulated signal and the color of light on the visibility of phantom array effect was studied simulating road lighting condition.The results show that,the frequency of modulated signal has significant effect on the visibility of phantom array effect and the effect is most visible at around 800 Hz,while is less visible at lower or higher frequencies.The waveform of signal also has effect on the visibility of the phantom array effect and the phantom array generated by square wave is more visible than the sine wave.The visibility of phantom array effect is also affected by the color of light.The phantom array effect generated by blue light is significantly more visible compared to the red and white light,while there's no difference between the latter two.Secondly,the influence of frequency on the visibility of the phantom array effect was also studied under office lighting condition.Results show that,coincidental to the road lighting condition,the phantom array effect with 600 Hz modulated signal is more visible compared to 100 Hz and 1200 Hz.Finally,the relationship between visibility of phantom array effect and frequency of modulated signal was analyzed based on the fourier transform and minkowski summation.A prediction model for the visibility of phantom array effect was established by support vector regression and was proved to be robust.