September 2009doc.: IEEE 802.15-12-0278-00-wng0 4/11/2019<month year> <month year> doc.: IEEE 802.15-09-0117-00-0007 July 2015 doc.: IEEE 802. 15-15-0575-00-007a Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Kookmin University Comments to TCD 15-492r2: Flickering Consideration for OWC] Date Submitted: [July, 2015] Source: [Trang Nguyen, Md. Shareef Ifthekhar, and Yeong Min Jang] [Kookmin University] Address [Kookmin University, Seoul, Korea] Voice:[82-2-910-5068], FAX: [82-2-910-5068], E-Mail:[yjang@kookmin.ac.kr] Re: [] Abstract: This slide presents the flickering consideration and human eyes safety related issues. Purpose: Call for Application Response Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Submission Kookmin University <author>, <company>

doc.: IEEE 802.15-<doc#> <month year> doc.: IEEE 802.15-<doc#> July 2015 doc.: IEEE 802. 15-15-0575-00-007a Definition, quantifying, frequency and light intensity consideration of flicker Yeong Min Jang yjang@kookmin.ac.kr Submission Kookmin University <author>, <company>

Contents Definition of Flicker Quantifying flicker July 2015 doc.: IEEE 802. 15-15-0575-00-007a Contents Definition of Flicker Quantifying flicker Flicker vs. frequency Flicker vs. light intensity Conclusion

Definition of Flicker 1. Definition in the IEEE 802.15.7 [1] July 2015 doc.: IEEE 802. 15-15-0575-00-007a Definition of Flicker 1. Definition in the IEEE 802.15.7 [1] Flicker refers to the fluctuation of the brightness of light. To avoid flicker, the changes in brightness must fall within the maximum flickering time period (MFTP). The MFTP is defined as the maximum time period over which the light intensity can change without the human eye perceiving it. 2. Definition in the IEEE Standard P1789 [2] Flicker is a rapid and repeated change over time in the brightness of light. 3. Classification [2] Visible Flicker: Flicker that is perceivable by human viewer. Invisible Flicker: Flicker that is not perceivable by a human viewer. [1] Sridhar Rajagopal-Samsung Electronics, Richard D. Roberts-Intel and Sang Kyu Lim-ETRI, “IEEE 802.15.7 Visible Light Communication: Modulation and Dimming Support,” IEEE Communication Magazine, March 2012 [2] Arnold Wilkins, Jennifer Veitch and Brad Lehman, “LED Lighting Flicker and Potential Health Concerns: IEEE Standard PAR1789 Update,” Energy Conversion Congress and Exposition (ECCE), 2010 IEEE, pp. 171-178, Sept. 2010.

July 2015 doc.: IEEE 802. 15-15-0575-00-007a Quantifying flicker Figure. Periodic waveform characteristics used in the calculation of flicker metrics [3] [3] U.S. Department of Energy, “Solid-state Lighting Technology Fact Sheet – Flicker” [Online], March 2013. Available: http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/flicker_fact-sheet.pdf

Figure. Light Output from LED at 100Hz and flicker parameters [3] July 2015 doc.: IEEE 802. 15-15-0575-00-007a Quantifying flicker Figure. Light Output from LED at 100Hz and flicker parameters [3] [3] U.S. Department of Energy, “Solid-state Lighting Technology Fact Sheet – Flicker” [Online], March 2013. Available: http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/flicker_fact-sheet.pdf

Flicker vs. modulation frequency July 2015 doc.: IEEE 802. 15-15-0575-00-007a Flicker vs. modulation frequency Figure. Patents responding as a function of flash frequency [2] The former are associated with visible flicker, typically within the range ~3- ~70Hz [2] The upper frequency limit above which high frequency flicker ceases to have biological effects is not known [2] As noted in the table below, much of the literature might suggest that ~160Hz – ~200Hz may be a sufficient limit for flicker to have negligible biological effects in some lighting applications, but note that none of the literature considers the eyes in motion across a high spatial contrast [2]. [2] Arnold Wilkins, Jennifer Veitch and Brad Lehman, “LED Lighting Flicker and Potential Health Concerns: IEEE Standard PAR1789 Update,” Energy Conversion Congress and Exposition (ECCE), 2010 IEEE, pp. 171-178, Sept. 2010.

Flicker vs. modulation frequency July 2015 doc.: IEEE 802. 15-15-0575-00-007a Flicker vs. modulation frequency While there is no widely accepted optimal flicker frequency number, a frequency greater than 200 Hz (MFTP < 5 ms) is generally considered safe [1]. visible flicker, typically within the range ~3- ~70Hz [2] Invisible flicker: there is no upper limit. But < 200Hz can be considered to be safe[2] Low-frequency flicker (on the order of 120-150 Hz; cf. Ref. 14) may add extra noise to the neural Activity [2]. [1] Sridhar Rajagopal-Samsung Electronics, Richard D. Roberts-Intel and Sang Kyu Lim-ETRI, “IEEE 802.15.7 Visible Light Communication: Modulation and Dimming Support,” IEEE Communication Magazine, March 2012 [2] Arnold Wilkins, Jennifer Veitch and Brad Lehman, “LED Lighting Flicker and Potential Health Concerns: IEEE Standard PAR1789 Update,” Energy Conversion Congress and Exposition (ECCE), 2010 IEEE, pp. 171-178, Sept. 2010.

Flicker vs. modulation frequency July 2015 doc.: IEEE 802. 15-15-0575-00-007a Flicker vs. modulation frequency a) b) Figure. Modulation rate range in VLC (a) and in OCC (b) to mitigate flicker

July 2015 doc.: IEEE 802. 15-15-0575-00-007a Flicker vs. brightness Brightness. Stimulation in the scotopic or low mesopic range (below about 1 cd/m2) has a low risk and the risk increases monotonically with log luminance in the high mesopic and photopic range [2]. [1] IEC60825 NIR Safety Limits [3] [1] Sridhar Rajagopal-Samsung Electronics, Richard D. Roberts-Intel and Sang Kyu Lim-ETRI, “IEEE 802.15.7 Visible Light Communication: Modulation and Dimming Support,” IEEE Communication Magazine, March 2012 [2] Arnold Wilkins, Jennifer Veitch and Brad Lehman, “LED Lighting Flicker and Potential Health Concerns: IEEE Standard PAR1789 Update,” Energy Conversion Congress and Exposition (ECCE), 2010 IEEE, pp. 171-178, Sept. 2010. [3] Rick Roberts [Intel] LOS Link Budget, IEEE 802.15-15-0500-01-007a, July 2015.

Conclusion Human eyes safety must be considered. July 2015 doc.: IEEE 802. 15-15-0575-00-007a Conclusion Human eyes safety must be considered. Frequency range < 100Hz is visible flicker range to human eye, can be used to modulate light but request high consideration to eye safety. Brightness/light intensity is limited here. Frequency range > 100Hz is low-flicker to human eye (can be considered as invisible flicker), can be used to modulate light with consideration to eye safety. Frequency range > 200Hz can be considered as safe range to modulate light. However, long-time use may still have some potential health concerns.