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Lasers and Eye Safety
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The UK HSE (Health & Safety Executive) has strict
safety requirements for lasers. Since many of these products
are incorporated into quality inspection or alignment
equipment used in the workplace, it is important to understand
the safety issues regarding lasers.
Lasers are classified into several
different categories, depending on the output power,
wavelength and fan angle. Structured lighting products
fall mainly into the following three categories, depending
on radiation levels attained during regular laser operation:
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Class
II --"Caution"
Visible laser light less than 1.0 mW.
Considered eye-safe, normal exposure to this type of beam will
not cause permanent damage to the retina. When exposed to this
level of laser light, the blinking reflex of the human eye is
fast enough to avoid any damage. A Class II safety rating is
considered eye-safe, but can be hazardous if there is direct
long-term ocular exposure (> 1000 seconds). Any Class II-rated
laser product can be installed on the shop floor with a minimum
of concerns. Certification is given on lasers that have an On/Off
switch and an LED.
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Class
IIIa --"Danger"
Visible laser light between 1.0 and 5.0 mW.
Considered eye-safe with caution, but may present a greater
hazard if viewed using collecting optics. Focusing of this light
into the eye could cause eye damage. Some groups of Class IIIa
lasers have a DANGER label and are capable of exceeding permissible
exposure levels for the eye in 0.25 sec and still pose a low
risk of injury. Certification is given on lasers that have an
On/Off switch and an LED.
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Class
IIIb --"Danger"
Infrared (IR) lasers and high-power visible lasers.
Considered dangerous to your retina if exposed. This includes
looking directly into a reflection from a specular (mirror-like)
surface. Normally, Class IIIb lasers will not produce a hazardous
diffuse reflection. At higher levels of the class, these lasers
can be skin hazards. Certification is given on lasers that have
a key box and remote interlock (Lasiris key boxes have an integrated
remote interlock). |
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Class
IV --"Danger"
Laser or laser systems that produce a
hazard not only from direct or specular reflections, but may
also produce hazardous diffuse reflections. Such lasers may
produce significant skin hazards as well as fire hazards.
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Each laser is classified according to CDRH and IEC 60825-1:1993
conditions. For CDRH classification, the laser beam, either
as a raw or modified beam, is focused into a 7 mm aperture located
20 cm away from the laser (for IEC, 50 mm aperture and distance
of 10 cm). The detector placed just behind the aperture records
the highest output power level of the laser beam. In the case
of a conventional gaussian line generator, it is generally the
hot central spot that causes its safety rating to go up one
class (from II to IIIa). Our patented optics producing a line
of uniform intensity along its length does not have a hot spot
at the center. Therefore, a Lasiris non-gaussian laser offers
eye-safe levels of exposures, in addition to more light and
uniform illumination transmitted to your part.
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Procedure for Classification
Here is the setup for both CDRH and
IEC 60825-1:1993 standards.
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Classification of Class IIIb lasers by IEC 60825-1 section
12.5.2 is as follows,
Class IIIb lasers are potentially hazardous if a direct beam
or specular reflection is viewed by the unprotected eye (intrabeam
viewing). The following precautions should be taken to avoid
direct beam viewing and to control specular reflections.
a. The laser should only be operated in a controlled area
b. Care should be exercised to prevent unintentional specular
reflections
c. The laser beam should be terminated where possible at the
end of its useful path by a material that is diffuse and such
a color and reflectivity as to make beam positioning possible
while still minimizing the reflection hazards
NOTE: Conditions for safe viewing of diffuse reflections for
Class IIIb visible lasers are: minimum viewing distance of
13 cm between screen and cornea, and a maximum viewing time
of 10 sec. Other viewing conditions require a comparison of
the diffuse reflection exposure with the MPE (maximum permissible
exposure limit).
d. Eye protection is required if there is any possibility
of viewing either the direct or specularly reflected beam,
or of viewing a diffuse reflection not complying with the
conditions of item c)
e. The entrances to areas should be posted with a standard
laser warning sign.
For more details on laser safety, contact us for our laser
safety booklet.
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