LSO 06: Beam Hazards Flashcards
What is MPE ?
amt of brightness safe to view for defined period
What is AEL ( accessible emission limit)?
maxm total power of laser radiation that can be emitted from the laser. It applies for laser manufacturer not for laser user
What is limiting aperture dependent on?
Laser wavelength, and other physical factors
What does higher classifications mean?
Higher risk of injury should accidental exposure occur
What are Class 1, Class 1M lasers?
M= magnifying optic
Safe under reasonable foreseeable conditions of operation, bean is inaccessible, visible and invisible wavelengths
What are Class 2/2M lasers?
low power visible wavelength lasers ( Should be visible), aversion response, AEL = 1mW for a CW laser
What are Class 3R lasers?
R= reduced requirements
Risk of injury is greater than for lower classess. AEL= 5mW ( continuous wave laser)
What are Class 3B lasers?
hazard from direct, Intra-beam viewing , specular reflection……. It is safe is view the diffuse reflection as long as its 13 cm from source and only 10 sec
AEL= 500mW, no fire hazard or combustion hazard
What are Class 4 lasers?
Direct intrabeam viewing is hazardous, specular and diffuse reflections is hazardous. eye, skin and fire hazard. more than 500mW
which class of laser has an AEL between 1-5 mW for a CW laser?
Class 3R
NHZ
Nominal Hazard Zone “ the space within which the level of the direct, reflected or scattered radiation may exceed the applicable MPE. Exposure levels beyond the boundary of the NHZ are below the appropriate MPE
Nominal Ocular Hazard Distance
The distance along the axis of the unobstructed beam from a laser, fiber end or connector to the human eye beyond which the irradiance or radiant exposure is not expected to exceed the applicable MPE
A class 3B laser with an NHZ of 30 cm is located in a lab. The laser operator stands no closer than 42 cm away from the laser during operations. Does this present a hazard to the operator?
No
Aperture
An opening window or lens through which optical radiation can pass
Intrabean Viewing
The viewing condition whereby the eye is exposed to all or part of a laser beam
Point source viewing
the viewing condition whereby the angular subtense of the source is equal to or less than the limiting angular subtense. less than 1.5mRad…..viewing through telescope is point source viewing
Telescopic Viewing
viewing an object from a long distance with the aid of an optical system that increases the visual size of the image.
Retinal Hazard Region
Optical radiation with wavelengths between 0.4 and 1.4 um ( 400-1400nm)
Beam Geometry
can be described by: path of travel for laser beam, shape of the beam
What is beam profile?
The distribution of irradiance or radiant exposure across the beam, perpendicular to the beam propagation direction
Gaussian Beam Profile
Laser generate a beam with a cross-sectional energy distribution that can be described mathematically by a gaussian type distribution
Top-hat beam profile
gives uniform beam energy across the diameter of the beam
What are the ways a person may view a laser beam?
Intrabeam, specular reflection, diffuse reflection, infra beam, lens or laser
what is infra beam viewing?
Eye directly in the path of laser beam
