The Safety Calculations - MediaLas Spooky blue Bedienungsanleitung

The scanning galvos are equipped with two AlO
the output window, AR-coated, has a reflection of 5% maximum.
Assuming a maximal power of 10mW, the laser power reflected from the scanning galvos should not
exceed 8.3mW.
The protective window has an anti-reflective coating optimized for all wavelengths of the visible spectrum.
Safety calculations
Determination of the maximum permissible exposure MPE of the Spooky Blue laser projector:
Assuming the laser source, emitting at 532nm, diameter d
diameter (radius of tunnel: r = 1,75m) at a distance of 4m, the divergence of the laser would results in a beam
diameter of approx. d = 15mm at 4 meters distance. The scanning impulse frequency is assumed F = 130Hz.
The human eye pupil diameter is assumed d' = 7mm (worst case, totally opened pupil in darkness).
The assumed emitting area of the laser source is of circular shape:
2
d
0
= ⋅ =
A π 78,53
Laser
4
The circumference of the scanned tunnel is:
= ⋅ ⋅ =
S 2 π r 10,996m
tunnel
Hence, the circular velocity becomes:
= ⋅ =
V S F 10,996m
tunnel tunnel
Considering the beam diameter as well as the diameter of the human eye pupil, the impulse duration for the
exposure becomes:
'
+
d d 15mm
= =
t
impulse
V
tunnel 1429,48
As the laser emits radiation of visible wavelength, the exposure duration is limited through the "eyelid
reflex" to T= 0,25s. For this duration, the total number of impulses is expressed as:
N = T x F = 130Hz x 0,25 s = 32.5
The following three criteria have to be considered and the most limiting case will define the MPE value. The
constant C has a value of one in this calculations as the emitting laser beam surface is considered of being
6
point shaped.
a) The exposure of each impulse should not exceed the MPE value for every single-impulse. Table 6
contains the exposure for the impulse duration of
The Exposure of a single-impulse is:
1
Chart 6 "Maximal permissible exposure for the impact of radiation into the cornea". VDE 0837, Page 33
Spooky Blue
coated mirrors with reflectivity of 94% each. Additionally,
2
= 10mm at laser output, scans a tunnel of 3.5 m
0
−
6 2
⋅
10 m
m
⋅ =
130Hz 1429,48
s
+
7mm
−
6
= ⋅
15,39 10 s
m
s
=
t 15,39
6 −
⋅
10 s
.
1
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