Reported laser accidents in the US from 1964 to 1992€¦ · Reported laser accidents in the US...
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Transcript of Reported laser accidents in the US from 1964 to 1992€¦ · Reported laser accidents in the US...
Radiation hazards - eye damage - skin damage - fire
Non-Radiation hazards - electrical - toxic dyes - toxic gases
Reported laser accidents in the US from 1964 to 1992
High power densities: Thermal, Acoustic (ablation)
Photochemical effects on tissue DNA Damage, Radical formation
Majority of accidents
Risk of irriversible damage
Eye Transmittance
Normal focusing by the eye results in an irradiance amplification of roughly 100,000
Regulated in EN207 & EN208
Maximum Permissible Exposure (MPE) Skin and Eyes (W/cm2 or J/cm2)
Valid for wavelength range: 180 nm – 1 mm
Wavelength (nm)
Power density (W/m2 or J/m2)
Mode of operation (pulsed or CW)
Exposure time
These values are used to determine MPE
500 nm: 385 microwatt for 10 sec. 830 nm: 600 microwatt for 10 sec. 1064 nm: 1.92 milliwatt for 10 sec. 1310 nm: 15 milliwatt for 10 sec.
RISK is different for PULSED LASERS below
55 kHz repetition rate or pulse length
shorter than 100 femtoseconds
Class 1= MPE not exceeded
Class 1M = May be unsafe if optical instruments are used
Class 2= Blink reflex prevents retinal damage
(visible wavelengths)
Class 2M = May be unsafe if optical instruments are used
Class 3B & 3R = MPE is exceeded, dangerous to eyes. Safety goggles are recommended (3B) /compulsory (3R)
Class 4 = (Scattered) radiation is dangerous to eyes and skin. Wear goggles and use screens.
If laser class > 3 wear goggles, use screens!
If laser class > 4 wear goggles, use screens & beam dumps!
Laser goggles are used to decrease exposure.
American standards use optical density
OD =
European regulations are more strict
I
I0log
L-classification (lookup tables)
MPE must not be exceeded
Whole eye must be covered
Goggles must sustain an exposure of 10 seconds or 100 pulses
Wavelength range D = CW operation I,R = Pulsed operation M = Ultrashort pulsed operation L = protection Level
Check Laser class
If laser class >2 use the right goggles
Turn laser sign on
Close door and curtains
Keep laser beam on optical table
Use screens on edge of tables
Use beam dumps for highest powers
Do not change other people’s set up!
Do not remove beam dumps
Do not wear shiny jewelry
Align at low powers
Warn supervisor if you see unsafe behaviour
Let your supervisor and BHV-er know
Seek medical attention
Medication can not reverse retinal damage but reduce damage due to inflammatory response
PhD student was aligning set up in lab
He used glasses
Alignment of an optical isolator
Suddenly he smelt something burning
Holes burnt in on shelf plate
Melted spots marks on laser goggles
1064 nm
3 Watt CW
Beam diameter = 4 mm = 23,9 W/cm2 = 2,39 × 105 W/m2
L scale 5 for 1064 nm operation mode D should be used
L scale 4 was used......
However, back reflected power was found to be 200 mW .... so he was lucky.... Was he?
Goggles OD 1064 nm = 7+
Beam dia < Entrance dia pupil
Exposure on retina = 20nW
MPE Eye = 1.92 mW for > 10 sec
Laser radiation may cause irreversible damage
Know your laser and corresponding goggles
Take care of safety rules
Seek medical attention in case of emergency
Guide to Laser Safety (Laser Vision GmbH)
http://www.noirlaser.com/pdf/net_elements.pdf
http://www.laserlab.vu.nl/en/Images/SAFETY_eyes_tcm116-175360.ppt
