1. Safety
• HD as discussed in "High Brightness precautions: Hazard Distance (H D )", page 6 , relevant for intrabeam exposure.
• HDreflection : the distance that has to be kept restrictive related to the reflected light from the rear projection screen.
• HDdiffuse : the relevan t distance to be cons idered while o bserving the defuse surface of the rear projection screen.
As desc ribed in "High Brightness precautions: H azard Distance (HD)", page 6 , it is mandatory to create a res tricted zone within
the beam areas closer than any NOHD. In the enclosed projection area the combination of two restricted zones are relevant: T he
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 reflec tion from the screen (HDreflection); also taking into account a 1 meter
lateral separation.
The HDreflection distance equals 25% of the difference between the determined H D 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 chapter "HD in function of the
lens Throw Ratio (TR)", page 8 .
HDreflection = 2 5% (HD – PD)
The light emitted from the screen within the observation s hall never exceed the RG2 exposure limit, determined at 10 cm. The
HDdiffuse can be neglected if the measured light at the screen surface is below 5000 cd/m ² or 15000 LUX.
1.6 HD in function of the lens Throw Ratio (TR)
TR (Throw Ratio)
The ratio of the distance to the screen (throw) to the screen width.
HD versus Throw Ratio
Image 1-4
Hazard Distance in meters versus Throw ratio of the lens for the F90 projectors
10 601–426 F70 SERIES 24/10/2017
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