17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 1
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: Optical Radiation Requirements for Light-Emitting Diodes and Implications for Visible-Light CommunicationsDate Submitted: 18th July 2008Source: 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, GermanyVoice: +49-89-636-45850, FAX: +49-89-636-51115, E-Mail: [email protected]
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 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.
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 2
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG 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. WalewskiSiemens AG
Corporate TechnologyInformation & Communications
Munich, Germany
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 3
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG 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 laser-
safety standard
• Silver lining:– LEDs in wireless communications can readily be
excluded from laser-safety standard in near future
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 4
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Outline
• Historical background
• Incoherent light sources
• Eye-damage according to lamp standard
• Skin-damage according to lamp standard
• Summary and outlook
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 5
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG 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 laser-safety 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
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 6
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG 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, …)
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 7
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Eye-damage mechanisms for visible light
1. Thermal• Burning of retina• Relevant quantity at retina: Irradiance [W/m2]
2. Photochemical (‘blue hazard’)• Photo-induced damage of retina• Strong wavelength dependence (blue!)• Relevant quantity at retina: Radiant energy [J/m2]
3. Cataract• UVA (< 400 nm)• Clouding of eye lens• Exposure limit: 10 kJ/m2 over 28 800 s (350 mW/m2 on
average)
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 8
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Eye-damage mechanisms for visible light: cataract
400 500 600 7000
0.2
0.4
0.6
0.8
1
Wavelength [nm]
No
rma
lize
d L
ED
Sp
ect
ral
Po
we
r slow modulation
fastmodulation
Level of UVA emission intimately dependent on white-light generation scheme
Decision: UVAnot considered in
this talk
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 9
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Eye damage: Averaging field of view for ‘blue hazard’
Ang
le o
f ac
cept
ance
/rad
0.1 1 10 100 1 103
1 104
0
0.05
0.1
0.15
1.7 103
FOV t( )
9.999 1030.25 t
Exposure duration/s
• “Smearing out” of retina image due to random eye movement• Potentially lower luminenous intensity
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 10
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Eye damage: Risk groups according to IEC 62471
1. Exempt• No photo-biological risk• Critical exposure duration: 10 000 s for ‘blue’, 10 s for
thermal
2. Low risk• “Behavioural” protection (avoiding displeasing illuminance,
…)• Critical exposure duration: 100 s for ‘blue’, 10 s for thermal
3. Medium risk• Protection due to blinking etc.• Critical exposure duration: 0.25 s
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 11
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Typical white LEDs used in our laboratory
Nichia NSPW500CS:120 mW, 260 mrad, 18 cd, ~ 1 lm
Ostar E3A30 W, 2.1 rad, 150 cd,~ 400 lm
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 12
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Eye damage (past): LED exemption limits based on laser safety standard (IEC 60825-1)
IEC: exemption limits for LEDs (Class 1)
0,01
0,1
1
10
100
1000
10000
color (peak wavelength)
Lu
min
ou
s in
ten
sit
y [
cd
] 100 mrad
90 mrad
80 mrad
70 mrad
60 mrad
50 mrad
40 mrad
30 mrad
20 mrad
15 mrad
11 mrad
9 mrad
7 mrad
5 mrad
3 mrad
1,5 mrad
blue light thermal hazard
Nichia NSPW500CS:120 mW, 260 mrad, 18 cd,
~ 1lm
Ostar E3A30 W, 2.1 rad, 150 cd,
~ 400 lm
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 13
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Comparison: exempt eye damage limits for lasers and lamps
CIE/IEC comparison of the exemt limits
0,01
0,1
1
10
100
1000
10000
100000
0,01 0,1 1 10 100 1000 10000 100000
CIE luminous intensity [cd]
IEC
lum
ino
us
inte
nsi
ty [
cd]
w hite
blue1
blue2
verde
green1
green2
green3
yellow
orange
amber
red1
red2
x = y
• Red LEDs: Higher limits today
• Green LEDs: Mostly higher limits today
• Blue and white LEDs: higher/lower limits today
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 14
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Eye damage (today): Exempt group according to IEC 62471
CIE: exempt group
1
10
100
1000
10000
100000
LED color
ma
x.
Lu
min
ou
s in
ten
sity [
cd
]
100 mrad
80 mrad
60 mrad
40 mrad
20 mrad
11 mrad
1,7 mradmight be reached
„unreachably“ high
Ostar E3A30 W, 2.1 rad,
150 cd, ~ 400 lm‘borderline’ exempt!
Nichia NSPW500CS:120 mW, 120 mrad,
18 cd, ~ 1 lmexempt!
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 15
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Eye damage (today): Low-risk group according to IEC 62471
CIE: low risk group
1
10
100
1000
10000
100000
LED color
ma
x. L
um
ino
us
inte
nsi
ty [
cd]
100 mrad
80 mrad
60 mrad
40 mrad
20 mrad
10 mrad
2 mrad
Ostar E3B30 W, 2.1 rad,
150 cd, ~ 400 lmlow risk
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 16
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG 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 E3 still in low-risk group
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 17
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Skin-damage mechanisms for visible light
1. Thermal• Burning of skin• 3 kW/m2 over 10 s• Corresponds to Ostar-E3A emission focused to ~ 3 cm2
• Potential issue!
2. Photochemical• < 400 nm (UVA): “Sunburn” (cancer!)• Critical exposure: 30 J/m2 for 28 800 s (8 h), viz. 1 mW/m2
• 350 times lower than ‘cataract’ exposure limit for eye!
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 18
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG 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
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 19
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Overall good news
• LED manufacturer will conduct classification for you!
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 20
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
Before you get too ecstatic …
• Skin damage through focusing optics
• Everything said only valid for single LED
• Luminous intensity [cd] of closely-spaced LEDs (arrays …) potentially additive (< 100 mrad viewing angle)
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 21
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG 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
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 22
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG VLC
(Our) Vision
Let’s create a safety-compliant VLC technology!
17th July 2008
Horak et al., Siemens AG, Corporate TechnologySlide 23
doc.: IEEE 802.15-08-0523-04-0vlc
Submission to IEEE 802.15 SG 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
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