LMI Selcom SLS 5000 - Safety of Laser Products; Maximum Permissible Exposures (Mpes); Laser Product Classification

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Safety of Laser products.
Maximum Permissible Exposures (MPEs)
IEC 60825-1, Safety of laser products, relies on the concept of the MPEs. The
MPEs are derived primarily from animal and human data, but take into account of
human variability and laser parameters Clause 3.55 of IEC 60825-1 defines the
maximum permissible exposures as “The level of laser radiation to which, under
normal circumstances, persons may be exposed without suffering adverse effects.
The MPE levels represent the maximum level to which the eye or skin can be
exposed without consequential injury immediately after, or after a long time, and
are related to the wavelength of the radiation, the pulse duration or exposure time.
The tissue at risk and, for visible and near infrared radiation, the size of the retinal
image. For calculation of MPE see “Calculation of MPE and NOHD in this
manual.
Laser product classification.
The classification of a laser product is based on the radiation emitted during the
normal operation and any reasonable foreseeable fault condition for that product.
4.1.1.1 Class 2 laser products:
Class 2 laser products would not cause permanent damage to the eye under
reasonable foreseeable conditions of operation, provided that any exposure can be
terminated by the blink reflex (assumed to take 0,25 s). Because classification
assumes the blink reflex, the wavelength must be in the visible range (400 nm to
700 nm). The Maximum Permissible Exposure (MPE) for visible radiation for
0,25 s is 25 W per square meter, which is equivalent to 1 mW entering an aperture
of 7 mm diameter (the assumed size of the pupil).
4.1.1.2 Class 3R laser products
Class 3R laser products emits radiation where direct intrabeam viewing is
potentially hazardous but the risk is lower than for Class 3B lasers, and fewer
manufacturing requirements and control measures for users apply than for Class
3B lasers.
4.1.1.3 Class 3B laser products
Class 3B laser products are unsafe for eye exposure. Usually only ocular
protection would be required. Diffuse reflections are safe if viewed for less than
10 s.
4.1.1.4 Nominal Ocular Hazard Distance (NOHD) or safety distance.
The NOHD is related to the Maximum Permissible Exposure (MPE). The NOHD
is the nominal distance at which the exposure equals the MPE. The concept of
NOHD is used when laser products such as range finders or display lasers are to
be used in the open air.