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26/11/19
Ver H
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 ≤ 10
4
s, the maximum radiance from blue light shall not exceed the
level defined by equations below.
)1(][
10
)(),(
12
6
700
300
srWm
t
BtLL
t
B
For exposure time t > 10
4
s, the radiance is limited to a constant value:
)2(][100)(
12
700
300
srWmBLL
B
where L
λ
is the spectral radiance in Wm
-2
sr
-1
nm
-1
, B
λ
is the blue light hazard weighting
function, ∆λ is the bandwidth in nm and t in seconds.
The maximum permissible exposure duration, t
max
for weighted source radiance, L
B
that
exceeding 100 Wm
-2
sr
-1
within t ≤ 10
4
s is computed as follows:
)3(][
10
6
max
s
L
t
B
Photobiological Safety for
DOMINANT LEDs
2
Ver H
Photobiological Safety for DOMINANT LED
26/11/19
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:
For exposure time t > 100s, the radiance is limited to a constant value:
)5(][1)(
2
700
300
WmBeE
t
B
where E
λ
is the spectral irradiance in Wm
-2
sr
-1
nm
-1
, B
λ
is the blue light hazard weighting
function, ∆λ is the bandwidth in nm and t in seconds.
For blue light source weight irradiance, E
B
greater than 0.01 Wm
-2
within t ≤ 100 s, the
maximum allowable exposure duration is calculated as followed:
)6(][
100
max
s
E
t
B
c. Infrared radiation hazard exposure limits for the eye
The exposure of infrared radiation within t ≤ 1000 s is restricted to:
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
300 400 500 600 700 800 900 1000 1100 1200 1300 1400
Spectral efficacy
Wavelength (nm)
R(λ)
B(λ)