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16 / 192018-08-16 | Document No.: AN097
Figure 14: Angular subtense index α versus viewing distance from SFH 4780S.
In any way, the upper limit of α = 0.1 rad.
As the thermal stress depends on the wavelength, the so-called burn-hazard
weighting function R(λ) is defined as:
for the SFH 4780S R(λ) becomes
Finally, the actual burn-hazard weighted radiance level L
R
from the SFH 4780S
can be calculated to be:
At last, L
R,lim
, the retinal thermal hazard exposure limit (EL) for exposure is
defined as:
Distance from SFH 4780S [cm]
Angular subtense
D
[rad]
16
0.10
0.08
0.06
0.04
0.02
0.00
6 101214420 8 18 20
SFH 4780S
for all operating conditions / time ranges)
R  10
700 –500
= 9
R
SFH 4780 S
810 nm 06, 10
L
R
L

R 
 300 nm =
1400 nm

L
e
R 
06, I
e

28
mm ,
2
-----------------------------
==11
L
R lim 10 sec
50000 W  m
2
 sr 
 t
025,

-------------------------------------------------
 12