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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 applicable 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 coated projection screen. As displayed
in image 1-3 two areas should be considered: the restricted enclosed projection area (RA) and the observation area (TH).
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: Hazard Distance (HD)", page 11, relevant for intrabeam exposure.
•
HD
: the distance that has to be kept restrictive related to the reflected light from the rear projection screen.
reflection
•
HD
: the relevant distance to be considered while observing the diffuse surface of the rear projection screen.
diffuse
As described in "High Brightness precautions: Hazard Distance (HD)", page 11, it is mandatory to create a restricted zone within
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 account 1 meter Separation Width (SW) from the beam onward.
Combined with the restricted zone related to the rear reflection from the screen (HD
separation.
The HD
distance equals 25% of the difference between the determined HD distance and the projection distance to the rear
reflection
projection screen. To determine the HD distance for the used lens and projector model see graphs in chapter "HD in function of
modifying optics", page 14.
HD
= 25% (HD – PD)
reflection
The light emitted from the screen within the observation shall never exceed the RG2 exposure limit, determined at 10 cm. The
HD
can be neglected if the measured light at the screen surface is below 5000 cd/m² or 15000 LUX.
diffuse
R5906753 DPXK BLP SERIES 20/11/2017
RA
PR
TH
HD
RZ
DIFFUSE
PD
HD
REFLECTION
); also taking into account a 1 meter lateral
reflection
1. Safety
13
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