Photobiological Safety for Dominant LED

Photobiological Safety for
DOMINANT LEDs
Background
The potential photobiological hazard of LEDs was initially being assessed to be similar to
laser in the laser safety standard by European Standard Organization. However, the
assessment does not truly represent the LEDs because the radiances difference in both
LED and lasers led to different applications as well as potential eye hazard levels. The
EN 60825 (equivalent to IEC 60825) standard was then further revised to accommodate
the issues. Finally, the LEDs were removed from the scope of IEC 60825-1:2007 and
published as IEC 62471:2006 Photobiological Safety of Lamps. The scope of this
standard applies to lamps and lamp systems safety including the safety of luminaires.
Hazard exposure limits (EL)
Optical radiation in general does not penetrate very deeply into biological tissues. The
blue light and infrared irradiated from LED primarily affects the eye and skin. Thus the
potential hazards for both blue light and infrared are governed by following distinct
exposure limits.
a. Retinal blue light hazard exposure limit
b. Blue light (small source) hazard exposure limits for the eye (cornea)
c. Infrared radiation hazard exposure limit for the eye (cornea)
d. Retinal thermal hazard exposure limit
e. Thermal hazard exposure limit for the skin
a. Blue light hazard exposure limits
For exposure time t ≤ 104 s, the maximum radiance from blue light shall not exceed the
level defined by equations below.
700
10 6
LB = ∑∑ Lλ (λ , t ) ⋅ B (λ ) ⋅ Δλ ≤
[Wm − 2 sr −1 ]
(1)
t
300 t
For exposure time t > 104 s, the radiance is limited to a constant value:
700
LB = ∑ Lλ ⋅ B(λ ) ⋅ Δλ ≤ 100
[Wm − 2 sr −1 ]
( 2)
300
where Lλ is the spectral radiance in Wm-2sr-1nm-1, Bλ is the blue light hazard weighting
function, ∆λ is the bandwidth in nm and t in seconds.
The maximum permissible exposure duration, tmax for weighted source radiance, LB that
exceeding 100 Wm-2sr-1 within t ≤ 104 s is computed as follows:
10 6
t max =
[s]
(3)
LB
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1.0E+01
Spectral efficacy
1.0E+00
R(λ)
1.0E‐01
1.0E‐02
1.0E‐03
B(λ)
1.0E‐04
300
400
500
600
700 800 900
Wavelength (nm)
1000 1100 1200 1300 1400
Figure 1: Blue light weighting hazard function B(λ) and thermal weighting hazard function R(λ)
b. Blue light (small source) hazard exposure limits for the eye
For blue light source with size less than 0.011 radians, the EL derivation for exposure time
t ≤ 100 s can be simplified using spectral irradiance:
700
100
E B = ∑∑ E λ (λ , t ) ⋅ B(λ ) ⋅ Δλ ≤
[Wm − 2 ]
( 4)
t
300 t
For exposure time t > 100s, the radiance is limited to a constant value:
700
E B = ∑∑ eλ ⋅ B(λ ) ⋅ Δλ ≤ 1
300
[Wm − 2 ]
(5)
t
where Eλ is the spectral irradiance in Wm-2sr-1nm-1, Bλ is the blue light hazard weighting
function, ∆λ is the bandwidth in nm and t in seconds.
For blue light source weight irradiance, EB greater than 0.01 Wm-2 within t ≤ 100 s, the
maximum allowable exposure duration is calculated as followed:
100
t max =
[s]
(6)
EB
c. Infrared radiation hazard exposure limits for the eye
The exposure of infrared radiation within t ≤ 1000 s is restricted to:
3000
18000
E IR = ∑ E λ ⋅ Δλ ≤ 0.75
[Wm − 2 ]
t
780
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For time t > 1000 s, the irradiance becomes independent to duration of exposure:
3000
E IR = ∑ E λ ⋅ Δλ ≤ 100
[Wm − 2 ]
(8)
780
where Eλ is the spectral irradiance in Wm-2sr-1nm-1, ∆λ given in nm and t in seconds. In
cold environments, the EL for t > 1000 s is increased to 400 Wm-2 at 0°C and 300 Wm-2 at
10°C.
d. Retinal thermal hazard exposure limits
Apparent light entering the pupil is focused by the cornea and lens. Then it is projected at
back of the eye where the retina lies and that defines the optical irradiation induced
stressed region. The angular substense, α at a viewing distance, d can be determined by:
1 ⎛l+w⎞
α= ⎜
[rad ]
(9 )
⎟
d⎝ 2 ⎠
with l and w are the length and width of the source respectively. Since the size of the pupil
changes with the level of luminance, the effective angular substense, αeff of blue light at a
given exposure duration is listed in the table below.
Wavelength, λ
(nm)
380 - 1400
Duration, t (s)
αmin,eff , γFOV (rad)
αmax,eff , γFOV (rad)
t ≤ 0.25
0.0017
0.1
t ≥ 10
t
0.25
0.011
t ≤ 100
0.011
0.0017
0.25 < t <10
Blue Light
(Additional
remarks)
0.011
100 < t < 10000
t ≥ 10000
0.1
t
100
0.1
0.1
0.1
0.1
0.1
Table 1: Limits of the angular substense, α and measurements field of view, γFOV at different time range
For irradiance measurement, the angular substense, α is defined by field of view, γFOV
given in equation below.
F
α eff = γ FOV =
[rad ]
(11)
r
where F is the size of the field stop and r is the distance source to detector.
The maximum EL to protect retinal from thermal injury is calculated based on the
integrated spectral radiance of the light source, Lλ and weighting function, R(λ). The EL is
a function of exposure time, t and angular substense, α from the source in radians when
10 µs ≤ t ≤ 10 s.
1400
50000
L R = ∑ Lλ ⋅ R ( λ ) ⋅ Δ λ ≤
[Wm − 2 sr −1 ]
(12)
0.25
α
⋅
t
380
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For longer exposure time, t > 10 s, the EL is defined by the near infrared range (weak
visual stimulus, 780 – 1400 nm) and limited to:
1400
6000
L IR = ∑ Lλ ⋅ R (λ ) ⋅ Δλ ≤
[Wm − 2 sr −1 ]
(13)
α
780
Cornea
Light Source d
Retina Figure 2: Angular substense, α at a viewing distance, d.
Apparent
Source
Detector
/Aperture Stop
α
γ
Field Stop, F
r
Figure 3: Alternative radiance measurement technique.
e. Thermal hazard exposure limit for skin
The highest EL of skin for t ≤ 10s shall be limited to:
3000
20000
E H = ∑∑ E λ (λ , t ) ⋅ Δλ ≤ 0.75
[ Jm − 2 ]
t
380 t
(12)
where Eλ is the spectral irradiance in Wm-2nm-1, ∆λ given in nm and t in seconds. For
exposure longer than 10 s, EL is not provided because severe pain occurs before the skin
can be damaged.
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Lamp Classification
The following table, it summarizes the limits and potential risk group classification of lamps
constructed using blue light and infrared irradiated LED.
Risk Group
Risk Group 2
(Moderate
Risk)
LB < 4,000,000
Retinal Blue Light
Retinal Blue light,
small source (α < 0.011
rad)
LB < 100
Risk Group
1
(Low Risk)
LB < 10,000
EB < 1.0
EB < 1.0
EB < 400
Retinal thermal
LR < 28000/ α
LR < 28000/
α
LR < 71000/ α
LIR < 6000/ α
LIR < 6000/ α
LIR < 6000/ α
EIR < 100
EIR < 570
EIR < 3200
Hazard
Exempt
(No Hazard)
Retinal thermal,
weak visual stimulus
(including non-GLS
source)
IR radiation
Risk Group 3
(High Risk)
Unit
Wm-2sr-1
Wm-2
Warning when
exceeded
limits of Risk
Group 2
Wm-2sr-1
-2
-1
Wm sr
Wm-2
Table 3: Emission limits for risks group of continuous wave lamps.
The hazard value for lamps intended for general light service (GLS) is reported at distance
which produces a luminance of 500 lux. Meanwhile, the measurement distance for other
light sources is fixed at 200 mm.
The recommended control measure for each hazard risk groups is listed in the following
table.
Risk Group
Exempt
(No Hazard)
Hazard
Risk Group 1
(Low Risk)
Risk Group 2
(Moderate Risk)
Risk Group 3
(High Risk)
Not required
Do not stare at
operating lamp.
May be harmful to
the eyes.
Do not look at
operating lamp.
May result in eye
injury.
Do not stare at
operating lamp.
Do not stare at
operating lamp.
Do not look at
operating lamp.
Use appropriate
shielding for eyes
Avoid eye
exposure. Use
appropriate
shielding or eye
protection.
Avoid eye
exposure. Use
appropriate
shielding or eye
protection.
Retinal Blue Light
(300 – 700 nm)
Retinal Blue light,
small source
Not required
Retinal thermal
(380 – 1400 nm)
Retinal thermal, weak
visual stimulus (780 –
1400 nm)
Not required
IR radiation
(780 – 3000 nm)
Table 4: Recommended control measure for each hazard risk groups.
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Analysis
Majority of LED produce by Dominant is visible LED with wavelength spectrum fall into
range from 400nm to 700nm. Thus by default there is no risk of UV or IR radiation
exposure from these LED. The photobiological risk of visible LED is hence confined to
blue light hazard and retinal thermal hazard. Table below summarized the maximum
brightness part number from each platforms of LED produced in Dominant.
Blue White Platform Part No. Maximum Luminous Flux [lm] Risk Hazard Platform Part No. Maximum Luminous Flux [lm] Risk Hazard SPNova NPB‐JSG 27.0 RG1 Primax 5 NTWW‐FSG 129.2 Exempt PowerDomi DWB‐LJG 2.7 Exempt KNova NKW‐RGG 113.6 Exempt Domi DDB‐HJS 1.3 Exempt SPNova NPW‐RSD 113.6 Exempt MiniDomi DNB‐DZJS 1.3 Exempt Primax 5 NSW‐FSG 67.2 Exempt MultiDomi D6RTB‐HJD 1.2 Exempt Primax NAW‐BSG 39.8 Exempt Spice SSB‐HLD 0.4 Exempt PowerDomi DWW‐WJG 8.9 Exempt Through‐
hole LED L5B‐N1500 1.0 RG 1 Domi DDW‐WJG 7.5 Exempt MiniDomi DNW‐UJG 2.7 Exempt Spice SSW‐HLD 1.3 Exempt MaxiDomi DBWWW‐DJG 24.0 Exempt Through‐
hole LED L5W‐N1500 4.0 RG 1 Table 5: List of LED with the maximum brightness part number from each platform.
Three of the highest brightness LED platform, SPNova Blue, KNova White and Primax 5
White is selected as vehicle for photobiological measurement and classification (Please
refer to appendix). Besides that, the emission from Dominant major LED group, the
DomiLED White and the narrow beam group of Through-hole LED were also presented.
These LEDs are placed at a distance, d = 200 mm and powered up with their datasheet
rated current.
The result indicates that SPNova Blue is classified under Risk Group 1 (Low Risk).
However, KNovaLED White and Primax 5 whitle falls into the Exempt Group category. The
emission from DomiLED White is also classified under the Exempt Group. Both Throughhole LED of Blue and White are classified under Risk Group 1 (Low Risk).
Summary
Based on the measurement result, it is proven that the worst case exposure scenario in
Dominant visible LED product range is classified under Risk Group 1 (Low Risk).
However, this assessment applies to the LED components alone. For custom application
that involves module integration and secondary optics, power density would be one of the
additional factor to be considered into the analysis.
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Appendix I
LED Type SPNova BLUE Luminous flux Peak Wavelength Color Small Source Peak Irradiance measured, Eλ 27.0 lm at IF = 350 mA, T = 25°C
455 nm
Blue
Yes
1.134 Wm‐2 at T = 25°C (Refer to chart below)
Risk Group Categories for Continuous Wave
Risk Factor Risk Group Result Actinic UV, ES (200 – 400 nm) Near UV, EUVA (315 – 400 nm) Blue Light, LB (300 – 700 nm) Blue Light Small Source, EB (300 – 700 nm) Retinal Thermal, LR (380 – 1400 nm) Retinal Thermal Weak Stimulus, LR (380 – 1400 nm)
Infrared Radiation for eye, LIR (780 – 3000 nm)
Exempt**
Exempt**
Risk Group 1 (Low Risk)
Exempt
Exempt
Exempt**
Exempt**
**No emission in the wavelength range of the listed risk category.
Irradiance Profile at 200 mm
Irradiance vs. Angle of Incidence (Distance source to detector =200 mm)
1.5
0°
Irradiance (Wm‐2)
90°
1.0
0.5
0.0
‐90
‐60
‐30
0
30
60
90
Angle from central axis (°)
Spectrum
Spectral Radiant Intensity
(Distance source to detector = 200 mm )
1.4E‐03
Intensity (Wsr‐1nm‐1)
1.2E‐03
1.0E‐03
8.0E‐04
6.0E‐04
4.0E‐04
2.0E‐04
0.0E+00
300
350
400
450
500
550
600
650
700
750
800
Wavelength (nm)
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Appendix II
LED Type KNovaLED Luminous flux Peak Wavelength Wavelength measured Color Small Source Peak Irradiance measured, Eλ 113.6 lm at IF = 350 mA, T = 25°C
455 nm
300 – 800 nm
White
No
0.902 Wm‐2 at T = 25°C (Refer to chart below)
Risk Group Categories for Continuous Wave
Risk Factor Risk Group Result Actinic UV, ES (200 – 400 nm) Near UV, EUVA (315 – 400 nm) Blue Light, LB (300 – 700 nm) Blue Light Small Source, EB (300 – 700 nm) Retinal Thermal, LR (380 – 1400 nm) Retinal Thermal Weak Stimulus, LR (380 – 1400 nm)
Infrared Radiation for eye, LIR (780 – 3000 nm)
Exempt**
Exempt**
Exempt
Exempt
Exempt
Exempt**
Exempt**
**No emission in the wavelength range of the listed risk category.
Irradiance Profile at 200 mm
Irradiance vs. Angle of Incide nce (Distance source to de te ctor = 200 m m )
1 .5
0°
90°
) 1 .0
m
W
(
e
c
n
ia
d
ar 0 .5
Ir
2
‐
0 .0
‐9 0
‐6 0
‐3 0
0
30
Angle from ce ntral axis (°)
60
90
Spectrum
Spectral Radiant Intensity
(Distance source to detector = 200 mm )
5.0E‐04
Intensity (Wsr‐1nm‐1)
4.0E‐04
3.0E‐04
2.0E‐04
1.0E‐04
0.0E+00
300
350
400
450
500
550
600
650
700
750
800
Wavelength (nm)
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Appendix III
LED Type DomiLED Luminous flux Peak Wavelength Wavelength measured Color Small Source Peak Irradiance measured, Eλ 7.5 lm at IF = 20 mA, T = 25°C
445 nm
300 – 800 nm
White
No
0.074 Wm‐2 at T = 25°C (Refer to chart below)
Risk Group Categories for Continuous Wave
Risk Factor Risk Group Result Actinic UV, ES (200 – 400 nm) Near UV, EUVA (315 – 400 nm) Blue Light, LB (300 – 700 nm) Blue Light Small Source, EB (300 – 700 nm) Retinal Thermal, LR (380 – 1400 nm) Retinal Thermal Weak Stimulus, LR (380 – 1400 nm)
Infrared Radiation for eye, LIR (780 – 3000 nm)
Exempt**
Exempt**
Exempt
Exempt
Exempt
Exempt**
Exempt**
**No emission in the wavelength range of the listed risk category.
Irradiance Profile at 200 mm
Irradiance vs. Angle of Incidence (Distance source to detector =200 mm)
0.10
0°
0.08
90°
)
m 0.06
W
(
ce
n
ai 0.04
d
ar
Ir
2
‐
0.02
0.00
‐90
‐60
‐30
0
30
60
90
Angle from central axis (°)
Spectrum
Spectral Radiant Intensity
(Distance source to detector = 200 mm )
2.5E‐05
Intensity (Wsr‐1nm‐1)
2.0E‐05
1.5E‐05
1.0E‐05
5.0E‐06
0.0E+00
300
350
400
450
500
550
600
650
700
750
800
Wavelength (nm)
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Appendix IV
LED Type Through‐hole LED Luminous flux Peak Wavelength Color Small Source Peak Irradiance measured, Eλ 1.0 lm at IF = 20 mA, T = 25°C
465 nm
Blue
Yes
1.109 Wm‐2 at T = 25°C (Refer to chart below)
Risk Group Categories for Continuous Wave
Risk Factor Risk Group Result Actinic UV, ES (200 – 400 nm) Near UV, EUVA (315 – 400 nm) Blue Light, LB (300 – 700 nm) Blue Light Small Source, EB (300 – 700 nm) Retinal Thermal, LR (380 – 1400 nm) Retinal Thermal Weak Stimulus, LR (380 – 1400 nm)
Infrared Radiation for eye, LIR (780 – 3000 nm)
Exempt**
Exempt**
Risk Group 1 (Low Risk)
Exempt
Exempt
Exempt**
Exempt**
**No emission in the wavelength range of the listed risk category.
Irradiance Profile at 200 mm
Spectrum
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Appendix V
LED Type Through‐hole LED Luminous flux Peak Wavelength Wavelength measured Color Small Source Peak Irradiance measured, Eλ 4.0 lm at IF = 20 mA, T = 25°C
460 nm
300 – 800 nm
White
Yes
0.756 Wm‐2 at T = 25°C (Refer to chart below)
Risk Group Categories for Continuous Wave
Risk Factor Risk Group Result Actinic UV, ES (200 – 400 nm) Near UV, EUVA (315 – 400 nm) Blue Light, LB (300 – 700 nm) Blue Light Small Source, EB (300 – 700 nm) Retinal Thermal, LR (380 – 1400 nm) Retinal Thermal Weak Stimulus, LR (380 – 1400 nm)
Infrared Radiation for eye, LIR (780 – 3000 nm)
Exempt**
Exempt**
Risk Group 1 (Low Risk)
Exempt
Exempt
Exempt**
Exempt**
**No emission in the wavelength range of the listed risk category.
Irradiance Profile at 200 mm
Spectrum
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Appendix VI
LED Type Primax 5 NTWW‐FSG Luminous flux Peak Wavelength Wavelength measured Color Small Source Peak Irradiance measured, Eλ 129.2 lm at IF = 150 mA, T = 25°C
450 nm
300 – 800 nm
White
No
0.996 Wm‐2 at T = 25°C (Refer to chart below)
Risk Group Categories for Continuous Wave
Risk Factor Risk Group Result Actinic UV, ES (200 – 400 nm) Near UV, EUVA (315 – 400 nm) Blue Light, LB (300 – 700 nm) Blue Light Small Source, EB (300 – 700 nm) Retinal Thermal, LR (380 – 1400 nm) Retinal Thermal Weak Stimulus, LR (380 – 1400 nm)
Infrared Radiation for eye, LIR (780 – 3000 nm)
Exempt**
Exempt**
Exempt
Exempt
Exempt
Exempt**
Exempt**
**No emission in the wavelength range of the listed risk category.
Irradiance Profile at 200 mm
Irradiance vs. Angle of Incidence (Distance source to detector =200 mm)
1.50
0°
‐2
Irradiance (Wm )
90°
1.00
0.50
0.00
‐90
‐60
‐30
0
Angle from central axis (°)
30
60
90
Spectrum
Spectral Radiant Intensity
(Distance source to detector = 200 mm )
2.0E‐04
1.8E‐04
‐1
1.4E‐04
‐1
Intensity (Wsr nm )
1.6E‐04
1.2E‐04
1.0E‐04
8.0E‐05
6.0E‐05
4.0E‐05
2.0E‐05
0.0E+00
300
350
400
450
500
550
600
650
700
750
800
Wavelength (nm)
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