9
BIOLOGICAL EFFECTS OF LASER BEAMS
Here are some known and documented effects of intense laser light over biological bodies:
- Ocular trauma: a collimated laser beam, focused by the eye lens, can create an extremely
intense light over the retina, even more intense than what would result from a direct viewing
of the sun. Such exposure can lead to a permanent damage of the vision.
- Thermal injury: following the absorption of laser energy, the tissue proteins are denatured due
to the temperature rise. Tissue damage results from this kind of exposure.
- Other damage mechanisms have also been demonstrated for other specific wavelength ranges
and/or exposure times. For example, photochemical reactions are the principal cause of
threshold level tissue damage following exposures to either ultraviolet radiation (200nm to 315
nm) for any exposure time or "blue light" visible radiation (400nm to 550nm) when exposures
are longer than 10 seconds.
Table 1-1: Summary of basic biological effects of light
Photobiological spectral domain
Ultraviolet C (200 to 280nm)
Erythema (sunburn)
Skin cancer
Ultraviolet B (280 to 315nm)
Accelerated skin aging
Increased pigmentation
Ultraviolet A (315 to 400nm)
Photochemical UV cataract
Pigment darkening
Skin burn
Photochemical and thermal
retinal injury
Photosensitive reactions
Skin burn
LASER CLASSIFICATION
The lasers sources are categorized according to their ability to harm the exposed bodies, from class 1 (no
hazard during normal use) to class 4 (severe hazard to eyes and skin).
Standard combiner models either belong to class 3B or class 4.
• Class 3B laser sources: laser products that are normally hazardous when intraocular beam
exposure occurs, including accidental short time exposure. Viewing diffuse reflections is
normally safe. Class 3B lasers may produce minor skin injuries or even pose a risk of igniting
flammable materials. However, this is only likely if the beam has a small diameter or is focused.
• Class 4 laser sources: laser products that are normally hazardous when intraocular beam
exposure occurs, including accidental short time exposure. Viewing diffuse reflections is not
safe. Class 4 lasers can produce severe skin injuries and can pose a risk of igniting flammable
materials.
Please refer to the Manufacturing Test Report (MTR) of your product for detailed information about the
laser classification of your combiner.
The classification of a laser is based on the concept of accessible emission limits (AEL) that are defined
for each laser class. This is usually the maximum power (in Watts) or energy (in Joules) that can be
emitted over a specified wavelength range and exposure time.
SAFETY GUIDELINES
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