1. Safety
1.5 HD for fully enclosed projection systems
HD
Hazard Distance (HD) is the distance measured from the projection lens at which the intensity or the energy per surface
unit becomes lower than the ap plicable exposure limit on the cornea or on the skin. The light beam is considered (to
be) unsafe for exposure if the distance from a person to the light source is less than the HD.
Restriction Zone (RZ) based on the HD
The projector is also suitable for rear projection applications; projecting a beam onto a defuse co ated projection screen. As displayed
in image 1-3 two areas sho uld be considered: the restricted enclosed projection area (RA) and the observation area ( TH).
RA TH
sw
PD
HDDIFFUSE
sw
RZ
sw
sw
PR
HD
REFLECTION
RESTRICTED
AREA
RESTRICTED
AREA
Image 1-3
RA Restricted Access location (enclosed projection area).
PR Projector.
TH Theater (observation area).
RZ Restriction Zone.
PD Projection Distance.
SW Separation Width. Must be minimum 1 meter.
For this type of setup 3 different HD shall be considered:
• HD as discussed in "High Br ightness precautions: Hazard Distance (HD)", page 10, relevant for intrabeam ex posure.
•HD
reflection
: the distance that has to b
e kept r estrictive related to the reflected light from the rear projection screen.
•HD
diffuse
: the relevant distance to be considered while observing the defuse surface of the rear projection screen.
As described in "High Brightness pr ecautions: Ha zard D istance (HD)", page 10, it is mandatory to create a r estricted zone within
the beam areas c loser than any NOHD. In the enc losed projection area the com bination of two restricted zones are relevant: The
restricted zone of the projected beam toward the s creen; taking into account 1 meter Separation Width (SW) from the beam onward.
Combined with the restricted zone related to the rear reflection from the s creen (HD
reflection
); also taking into account a 1 meter lateral
separation.
The H D
reflection
distance equals 25% of the difference between the determined HD distance and the projection distance to the rear
projection screen. To determine the HD distance for the used lens and projector model see graphs in c hapter "HD in function of
modifying optics", page 13.
HD
reflection
= 25% (HD – PD)
The light emitted from the screen within the observation s hall never exceed the RG2 exposure limit, determined at 10 cm. The
HD
diffuse
can be neglected if the measured light at th e screen surface is below 5000 cd/m² or 15000 LUX.
12
R5906847 DP2K SLP SERIES 02/06/2017
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