17 th July 2008 doc IEEE 802 15

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Project: IEEE P 802. 15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Optical Radiation Requirements for Light-Emitting Diodes and Implications for Visible. Light Communications Date Submitted: 18 th July 2008 Source: Werner Horak, Ronald Neuhaus, and Joachim W. Walewski Company Siemens AG, Corporate Environmental Affairs & Technical Safety and Corporate Technology, Information & Communications Address Otto-Hahn-Ring 6, DE-81739 Munich, Germany Voice: +49 -89 -636 -45850, FAX: +49 -89 -636 -51115, E-Mail: joachim. walewski@siemens. com Re: N/A Abstract: We discuss changes in eye-safety and skin-safety requirements for light-emitting diodes due to changes in safety legislation and we discuss subsequent implications for visible-light communications. Purpose: Helping the 802. 15 VLC SG to shape the scope of a VLC standard Notice: This document has been prepared to assist the IEEE P 802. 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 P 802. 15. Submission to IEEE 802. 15 SG VLC 1 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Optical Radiation Requirements for Light-Emitting Diodes and Implications for Visible-Light Communications (VLC) Werner Horak and Ronald Neuhaus Siemens AG Corporate Environmental Affairs & Technical Safety Joachim W. Walewski Siemens AG Corporate Technology Information & Communications Munich, Germany Submission to IEEE 802. 15 SG VLC 2 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Executive summary • Good news: – LEDs not longer covered by laser-safety standard • Generally higher exposure limits • Already considered by manufacturer of LED • Bad news: – Wireless communications still covered by lasersafety standard • Silver lining: – LEDs in wireless communications can readily be excluded from laser-safety standard in near future Submission to IEEE 802. 15 SG VLC 3 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Outline • Historical background • Incoherent light sources • Eye-damage according to lamp standard • Skin-damage according to lamp standard • Summary and outlook Submission to IEEE 802. 15 SG VLC 4 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Historical background • 1993 -2007: photo-biological safety aspects of LEDs covered by laser-safety standard IEC 60825 • Since 2007 LEDs in lighting/signalling scenarios covered by IEC 62471 (‘lamps’) • Our message: This is good for VLC – Evidence provided in the rest of this talk • But: LEDs in wireless communications still covered by lasersafety standard IEC 60825 -12 (free-space optics) • Motion by Siemens at IEC TC 76 meeting in Nov 2007: Exclude LEDs from IEC 60825 -12 and make IEC 62471 only pertinent standard – Status: No objections by chair Dr. Tozer – But: No action taken since then – Suggestion: Future VLC TG lobbies IEC to finalise complete withdrawal of LEDs from IEC 60825 -12 Submission to IEEE 802. 15 SG VLC 5 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Salient properties of incoherent light sources • No diffraction-limited focus • Large optical extent (no point image on retina) • Intrinsic scenarios for long-term exposure (illumination, displays, …) Submission to IEEE 802. 15 SG VLC 6 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Eye-damage mechanisms for visible light 1. Thermal • • 2. Burning of retina Relevant quantity at retina: Irradiance [W/m 2] Photochemical (‘blue hazard’) • • • 3. Photo-induced damage of retina Strong wavelength dependence (blue!) Relevant quantity at retina: Radiant energy [J/m 2] Cataract • • • UVA (< 400 nm) Clouding of eye lens Exposure limit: 10 k. J/m 2 over 28 800 s (350 m. W/m 2 on average) Submission to IEEE 802. 15 SG VLC 7 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Eye-damage mechanisms for visible light: cataract Decision: UVA not considered in this talk Level of UVA emission intimately dependent on white-light generation scheme Submission to IEEE 802. 15 SG VLC 8 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Eye damage: Averaging field of view for ‘blue hazard’ Angle of acceptance/rad • “Smearing out” of retina image due to random eye movement • Potentially lower luminenous intensity Exposure duration/s Submission to IEEE 802. 15 SG VLC 9 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Eye damage: Risk groups according to IEC 62471 1. Exempt • • 2. No photo-biological risk Critical exposure duration: 10 000 s for ‘blue’, 10 s for thermal Low risk • • 3. “Behavioural” protection (avoiding displeasing illuminance, …) Critical exposure duration: 100 s for ‘blue’, 10 s for thermal Medium risk • • Protection due to blinking etc. Critical exposure duration: 0. 25 s Submission to IEEE 802. 15 SG VLC 10 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Typical white LEDs used in our laboratory Ostar E 3 A 30 W, 2. 1 rad, 150 cd, ~ 400 lm Nichia NSPW 500 CS: 120 m. W, 260 mrad, 18 cd, ~ 1 lm Submission to IEEE 802. 15 SG VLC 11 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Eye damage (past): LED exemption limits based on laser safety standard (IEC 60825 -1) Ostar E 3 A 30 W, 2. 1 rad, 150 cd, ~ 400 lm Nichia NSPW 500 CS: 120 m. W, 260 mrad, 18 cd, ~ 1 lm Submission to IEEE 802. 15 SG VLC 12 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Comparison: exempt eye damage limits for lasers and lamps • • • Submission to IEEE 802. 15 SG VLC 13 Red LEDs: Higher limits today Green LEDs: Mostly higher limits today Blue and white LEDs: higher/lower limits today Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Eye damage (today): Exempt group according to IEC 62471, 10 000 s exposure for ‘blue’ Ostar E 3 A and 10 s for thermal 30 W, 2. 1 rad, 150 cd, ~ 400 lm ‘borderline’ exempt! „unreachably“ high might be reached Nichia NSPW 500 CS: 120 m. W, 120 mrad, 18 cd, ~ 1 lm exempt! Submission to IEEE 802. 15 SG VLC 14 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Eye damage (today): Low-risk group according to IEC 62471, Ostar E 3 B 30 W, 2. 1 srad, 100 exposure for ‘blue’ and 10 s for thermal 150 cd, ~ 400 lm low risk Submission to IEEE 802. 15 SG VLC 15 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Conclusion regarding LED eye safety (IEC 62471) • • No class ‘M’ Main hazards: ‘Blue’ and thermal Thermal generally not an issue ‘Blue’ can be an issue – But: Even high-illuminance LEDs like OSTAR E 3 still in low-risk group Submission to IEEE 802. 15 SG VLC 16 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Skin-damage mechanisms for visible light 1. Thermal • • 2. Burning of skin 3 k. W/m 2 over 10 s Corresponds to Ostar-E 3 A emission focused to ~ 3 cm 2 Potential issue! Photochemical • • • < 400 nm (UVA): “Sunburn” (cancer!) Critical exposure: 30 J/m 2 for 28 800 s (8 h), viz. 1 m. W/m 2 350 times lower than ‘cataract’ exposure limit for eye! Submission to IEEE 802. 15 SG VLC 17 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Conclusions regarding LED skin safety (IEC 62471) • • • Hazards: Thermal and ‘sunburn’ There is a class ‘M’ for skin safety ‘Sunburn’ limits for skin automatically guarantee ‘cataract’ limits for eye Submission to IEEE 802. 15 SG VLC 18 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Overall good news • LED manufacturer will conduct classification for you! Submission to IEEE 802. 15 SG VLC 19 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Before you get too ecstatic … • • • Skin damage through focusing optics Everything said only valid for single LED Luminous intensity [cd] of closelyspaced LEDs (arrays …) can be additive (< 100 mrad viewing angle) Submission to IEEE 802. 15 SG VLC 20 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc Summary • • Prospect of moving out VLC LEDs from IEC 60825 -12 to IEC 62471 Almost all LEDs either ‘exempt’ or ‘low risk’ Red and yellow LEDs: practically all exempt Caution: LEDs in arrays might exceed limits Skin limits are of concern Classification provided by LED manufacturer Suggestion: Lobby for removal of LEDs from IEC 60825 -12 Submission to IEEE 802. 15 SG VLC 21 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc (Our) Vision Let’s create a safety-compliant VLC technology! Submission to IEEE 802. 15 SG VLC 22 Horak et al. , Siemens AG, Corporate Technology

17 th July 2008 doc. : IEEE 802. 15 -08 -0523 -00 -0 vlc References/Literature • • W. Halbritter, W. Horak, and J. Werner, “Measurement requirements for the characterization of photobiological hazards posed by the optical radiation of lamps or LEDs, ” 2008 CIE Expert Symposium on Advances in Photometry and Colorimetry, 2008 International Electrotechnical Commission, “Photobiological safety of lamps and lamp systems , ” IEC 62471, 2006 International Electrotechnical Commission, “Safety of laser products - Part 1: Equipment classification and requirements, ” IEC 60825 -1, Ed. 2, 2007 International Electrotechnical Commission, “Safety of laser products - Part 12: Safety of free space optical communication systems used for transmission of information , ” IEC 60825 -12, 2005 International Electrotechnical Commission, Technical Committee 76: Laser Equipment, Working Group 5: Safety of Fiber Optics Communications Systems, Unconfirmed Minutes of the meeting held in Milan, 5– 9 November 2007 W. Horak and R. Neuhaus, “Optical radiation safety analysis of LEDs on the basis of guidelines for incoherent sources, ” Proc. ILSC 2005: 155 -162 W. Horak and R. Neuhaus, “Optical radiation safety requirements for LEDs according to their new status in between laser and lamp safety standards, ” Proc. ILSC 2007: 49 -53 Submission to IEEE 802. 15 SG VLC 23 Horak et al. , Siemens AG, Corporate Technology