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 expos ure limit on the cornea or on the skin. The light beam is considered (to
be) unsafe for exposure if the distance from a per son 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 should 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 Brightness precautions: Haz ard Distance (HD)", page 11, relevant for intrabeam exposure.
•HD
reflection
: the distance that has to b
e kept restrictive related to the reflected light from the rear projection screen.
•HD
diffuse
: the relevant distance to be c onsidered while observing the diffuse sur face of the rear projection s creen.
As described in "High Brightness precautions: Hazard Distance (HD)", page 11, it is mandatory to create a restricted zone w ithin
the beam areas closer than any NOHD. In the enclosed projection area the combination of two restricted zones are relevant: The
restricted zone of the projected beam toward the screen; taking into ac count 1 meter Separation W idth (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 m odel see graphs in chapter "HD in function of
modifying optics", page 14.
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 t he measured light at the screen surface is below 5000 cd/m² or 15000 LUX .
R5906753 DPXK BLP SERIES 20/11/2017
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