lasers and laser safety - university college cork sa… · laser safety causes of laser accidents...
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ROINN NA FISICE Department of
Physics
Lasers andLaser Safety
PY3108
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland 1
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UCCLaser Safety
• Basics of Lasers and Laser Light• Laser Beam Injuries• Laser Hazard Classes• Laser Safety Standards• Laser Control Measures and Procedures• Calculations and Estimates Quantifying Laser Safety
Contents
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 2
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UCCLaser Safety
L ight
A mplification by
S timulated
E mission of
R adiation
Basics of Lasers and Laser Light
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 3
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UCCLaser Safety
Light is an electromagnetic wave.
Different wavelengths in the visible
spectrum are seen by the eye as
different colors.
λλλλWavelength
Red: λ λ λ λ = 700 nm
Blue: λ λ λ λ = 400 nm
Wave nature of light
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 4
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UCCLaser Safety
Radio
Long WavelengthShort Wavelength
Gamma Ray X-ray Ultraviolet Infrared Microwaves
Visible
Lasers operate in the ultraviolet, visible, and infrared.
Radio
Electromagnetic Spectrum
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 5
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UCCLaser Safety
Incident Photon
Excited Atom
Laser-Professionals.com
Stimulated Photonsame wavelength
same directionin phase
Incident Photon
Stimulated Mission
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 6
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UCCLaser Safety
MONOCHROMATIC
DIRECTIONAL
COHERENT
The combination of these three properties makes laser light focus 100 times better than ordinary light
Laser Light - Characteristics
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 7
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UCCLaser Safety
Monochromatic
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 8
one colour
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UCCLaser Safety
Directional
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 9
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UCCLaser Safety
Coherent
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 10
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UCCLaser Safety
High ReflectanceMirror (HR)
Output CouplerMirror (OC)
ActiveMedium
OutputBeam
Excitation Mechanism
Optical Resonator
Laser Components
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 11
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UCCLaser Safety
Helium-Neon Gas Laser
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 12
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UCCLaser Safety
Rear Mirror
Adjustment Knobs
Safety Shutter Polarizer Assembly (optional)
CoolantBeamTube
AdjustmentKnob
OutputMirror
Beam
Beam Tube
HarmonicGenerator (optional)
Laser Cavity
PumpCavity
Flashlamps
Nd:YAGLaser Rod
Q-switch(optional)
Courtesy of Los Alamos National LaboratoryCourtesy of Los Alamos National Laboratory
Laser-Professionals.com
Neodymium YAG Laser
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 13
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UCCLaser Safety
Feedback
Physics, Photonics & Ethics November 11, 2009
amplifier
speaker
microphone
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UCCLaser Safety
Introduction to Laser Physics
Physics, Photonics & Ethics November 11, 2009
Start with one unit of
optical power
End with r2g2 units of
optical power after one
round trip.
Gain or Amplification
RegionMirror with
Reflectivity = r
Mirror with Reflectivity = r
1g
(1-r)g
rgrg2
r2g2
(1-r)rg2
3 possibilities : r2g2 < 1 optical field decays
r2g2 = 1 stable optical field(so called lasing condition)
r2g2 > 1 optical field increases
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UCCLaser Safety
10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 10 102
LASERS
200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 10600
Ultraviolet Visible Near Infrared Far Infrared
Gamma Rays X-Rays Ultra- Visible Infrared Micro- Radar TV Radioviolet waves waves waves waves
Wavelength (m)
Wavelength (nm)
Nd:YAG1064
GaAs905
HeNe633
Ar488/515
CO2
10600XeCl308
KrF248
2ωωωω
Nd:YAG532
Retinal Hazard Region
ArF193
CommunicationDiode1550
Ruby694
Laser-Professionals.com
Alexandrite755
Laser Spectrum
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 16
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UCCLaser Safety
Laser Beam Injuries
High power lasers can cause skin burns.
Lasers can cause severe eye injuries resulting in permanent vision loss.
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 17
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UCCLaser Safety
Accidental exposure to partial reflection of 2000 W CO2 laser beamfrom metal surface during cutting
Skin Burn from CO2 Laser
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 18
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UCCLaser Safety
EYE
INTRABEAM VIEWING
LASER
MIRROR
SPECULAR REFLECTION
LASER
REFLECTED BEAM
DIFFUSE REFLECTION
LASER
SCATTERED LIGHT
ROUGHSURFACE
Types of Laser Eye Exposure
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 19
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UCCLaser Safety
Choroid
Aqueous
Cornea
Macula
Optic Nerve
Sclera
Vitreous
RetinaLens
Human Eye
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 20
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UCCLaser Safety
The Retinal Hazard Region
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 21
400-1400 nmAffects the retina
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UCCLaser Safety
UV-C (100-280nm)Cornea surface
UV-A (315-400nm)Affects the lens
UV-B (280-315nm)Absorbed by the cornea
Ultraviolet Light
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 22
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UCCLaser Safety
Far IRAffects cornea and aqueous humor
Near IR (< 1400nm)Affects the retina
Infra-red Region
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 23
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UCCLaser Safety
25 µ
Photo courtesy of U S Air Force
THERMAL BURNSON
PRIMATE RETINA
Laser-Professionals.com
ROINN NA FISICE
Department of Physics
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland 24
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UCCLaser Safety
Multiple Pulse Retinal Injury
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 25
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UCCLaser Safety
Retinal Injury produced by four pulses from a Nd:YAG laser range finder.
Q-Switched Laser Injury
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 26
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UCCLaser Safety
Causes of Laser Accidents
Studies of laser accidents have shown that there are usually
several contributing factors. The following are common
causes of laser injuries:
Inadequate training of laser personnel
Alignment performed without adequate procedures
Failure to block beams or stray reflections
Failure to wear eye protection in hazardous situations
Failure to follow approved standard operating procedures
or safe work practices
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 27
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UCCLaser Safety
Lasers are classified according to the
level of laser radiation that is
accessible during normal operation.
Laser Hazard Classes
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 28
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UCCLaser Safety
Important terminology
Maximum Permissible Exposure (MPE)
Accessible Emission Limits (AEL)
Nominal Ocular Hazard Distance (NOHD)
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 29
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UCCLaser Safety
Class 1 MPE less than 7 microwatts of visible radiation.
A Class 1 laser is considered “safe” under reasonably
foreseeable conditions of operation and they present no
hazard to the eye or skin.
This Class also includes laser systems which cannot emit
hazardous levels of laser radiation because of the
inherent design of the product.
Note that there may be a more hazardous laser system
embedded in the product and additional precautions
would be necessary if the system is opened up.
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 30
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UCCLaser Safety
Class 1M
Exceed accessible emission limits for Class 1 but,
because of the geometrical spread of the emitted
radiation, the laser does not cause harmful levels
of exposure to the unaided eye.
Safe limit can be exceeded, and injury can occur, if
magnifying viewing instruments are used, eg
binoculars, telescopes, magnifying glasses,
microscopes.
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 31
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UCCLaser Safety
Class 2 MPE less than 1 mW of visible radiation.
A Class 2 laser or laser system must only emit a visible
laser beam.
Momentary viewing of a Class 2 laser beam is not
considered hazardous since the upper limit for this type
of device is less than the maximum permissible exposure
(MPE) for momentary exposures of 0.25 second or less -
the so-called “blink reflex”.
Intentional extended viewing is considered hazardous.
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 32
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UCCLaser Safety
Class 2M Laser products which exceed the permitted accessible
limits for Class 2 but, because of the geometric spread of
the emitted radiation, protection of the unaided eye is
normally afforded by natural aversion responses to bright
light.
The use of magnifying viewing instruments can give rise
to higher levels of exposure and injury can occur. These
instruments include: binoculars; telescopes; magnifying
lenses; and microscopes.
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 33
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UCCLaser Safety
Class 3R
Laser products having a level of accessible
emission up to five times the limits for Class 1 (if
invisible) or Class 2 (if visible).
The maximum permissible exposure may be
exceeded but the risk of injury is low.
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 34
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UCCLaser Safety
Class 3B
Less than 500 mW of visible radiation
note that Class 3B also covers pulsed lasers and invisible
radiation. Reference should be made to the MPE limits
contained in the British Standard in order to verify
classification.
Direct intra-beam viewing is always hazardous.
Viewing diffuse reflections from a distance is
normally safe provided the exposure duration is
less than 10 seconds.
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 35
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UCCLaser Safety
Class 4 Over 500 mW visible radiation
note that Class 4 also covers pulsed lasers and invisible radiation.
Reference should be made to the MPE limits contained in the
British Standard in order to verify classification.
These lasers are very powerful and may also be a fire
hazard.
Exposure of the skin to the beam may cause injury.
Even diffuse reflections are hazardous.
Very stringent control measures are required.
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UCCLaser Safety
Some Examples & Numbers
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 37
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UCCLaser Safety
Engineering controls Engineering controls remove the dependence to follow
rigorous procedures and the possibility of failure of
personal protective equipment.
Engineering controls all the safety features built into the
design of the laser and its associated equipment.
Examples of Engineering Controls include:
key control;
remote interlock;
beam enclosures;
protective filter installations.
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 38
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UCCLaser Safety
Administrative controls Administrative and Procedural Controls are intended to
supplement Engineering Controls to ensure that laser
personnel are fully protected from laser hazards.
Administrative/Procedural Controls include:
information, instruction and training;
signage;
protocols
arrangements for maintenance;
arrangements for servicing.
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 39
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UCCLaser Safety
Signage
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 40
Class 1
CLASS 1 LASER PRODUCT
Class 2 LASER RADIATION
DO NOT STARE INTO BEAM
CLASS 2 LASER PRODUCT
Class 2M LASER RADIATION
DO NOT STARE INTO BEAM OR VIEW
DIRECTLY WITH OPTICAL INSTRUMENTS
CLASS 2M LASER PRODUCT
Class 3B LASER RADIATION
AVOID EXPOSURE TO BEAM
CLASS 3B LASER PRODUCT
Class 4 LASER RADIATION
AVOID EYE OR SKIN EXPOSURE TO
DIRECT OR SCATTERED RADIATION
CLASS 4 LASER PRODUCT
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UCCLaser Safety
Symbol and Border: BlackBackground: Yellow
Legend and Border: BlackBackground: Yellow
INVISIBLE LASER RADIATIONAVOID EYE OR SKIN EXPOSURE
TO DIRECT OR SCATTERED RADIATIONCLASS 4 LASER PRODUCT
WAVELENGTH 10,600 nmMAX LASER POWER 200 W
EN60825-1 1998
International LaserWarning Labels
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 41
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UCCLaser Safety
Personal Protective Equipment
Personal protective equipment should only be
used when the above measures do not provide
sufficient control.
Personal protective equipment includes:
protective eyewear; and
protective clothing.
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 42
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UCCLaser Safety
Laser eye protection
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
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Department of Physics 43
Selection of eyewear should be based
on:
wavelength(s) being used;
radiant exposure;
maximum permissible exposure (MPE);
optical density of eyewear;
visible light transmission requirements;
adequate peripheral vision; prescription
lenses; and,
comfort.
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UCCLaser Safety
Optical Density
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 44
−=
in
out
I
IA 10logλ
λA
inoutII
−×=→ 10
Example 1:000,000,1
1=
in
out
I
I
Example 1: 3=λA1000
10 3 in
inout
III =×=→ −
6000,000,1
1log 10 =
−=λA
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UCCLaser Safety
Eyewear Labels
All eyewear must be labeled with wavelength and optical
density.Guidelines in EN208
(Handout)
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 45
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UCCLaser Safety
Example: Plastic Eyewear Characteristics
10
9
8
7
6
5
4
3
2
1
0
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
Wavelength (µµµµm)
Op
tical
Den
sit
y
GreenNd:YAG filter
Orange2ωωωω Nd:YAG
filter
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 46
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UCCLaser Safety
The person operating the laseralways has the primary
responsibility for all hazards associated with laser use.
Who has the primary responsibility for laser safety any time a CLASS 3 or
CLASS 4 laser is operated?
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 47
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UCCLaser Safety
Suggested Format forStandard Operating Procedures (SOP)
1. Introduction – Description of laserType and wavelength; Intended application & LocationAverage power or energy per pulsePulse duration and repetition rate for pulsed lasers
2. Hazards – List all hazards associated with laserEye and skin hazards from direct and diffuse exposuresElectrical hazardsLaser generated air contaminantsOther recognized hazards
3. Control Measures – List control measures for each hazardInclude the following:
Eyewear requirement, include wavelength and ODDescription of controlled area and entry controlsReference to equipment manualAlignment procedures (or guidelines)
4. Authorized Personnel
5. Emergency Procedures
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 48
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UCCLaser Safety
• Most beam injuries occur during alignment.
• Only trained personnel may align class 3 or class 4
lasers (NO EXCEPTIONS!)
• Laser safety eyewear is required for class 3 and
class 4 beam alignment.
• ANSI REQUIRES approved, written alignment
procedures for ALL class 4 laser alignment activities
and recommends them for class 3.
Safe Beam Alignment
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 49
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UCCLaser Safety
1. Exclude unnecessary personnel from the laser area during alignment.
2. Where possible, use low-power visible lasers for path simulation of high power visible or invisible lasers.
3. Wear protective eyewear during alignment. Use special alignment eyewear when circumstances permit
their use.
4. When aligning invisible beams, use beam display devices such as image converter viewers or phosphor
cards to locate beams.
5. Perform alignment tasks using high-power lasers at the lowest possible power level.
6. Use a shutter or beam block to block high-power beams at their source except when actually needed
during the alignment process.
7. Use a laser rated beam block to terminate high-power beams downstream of the optics being aligned.
8. Use beam blocks and/or laser protective barriers in conditions where alignment beams could stray into
areas with uninvolved personnel.
9. Place beam blocks behind optics to terminate beams that might miss mirrors during alignment.
10. Locate and block all stray reflections before proceeding to the next optical component or section.
11. Be sure all beams and reflections are properly terminated before high-power operation.
12. Alignments should be done only by those who have received laser safety training.
Alignment Guidelines forClass 3 and 4 lasers
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 50
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UCCLaser Safety
• Never intentionally look directly into a laser. Do not stare at the light from any laser.
Allow yourself to blink if the light is too bright.
• Never view a Class 3 (or any higher power) laser with optical instruments.
• Never direct the beam toward people.
• Operate lasers only in the area designed for their use and be certain that the beam is
terminated at the end of its use path. Never allow a laser beam to escape its designated
area of use.
• Position the laser so that it is well above or below eye level.
• Only block the beam with appropriate (enclosing or diffuse reflecting) beam blocks/shutters.
• Always enclose laser beams as much as possible with appropriate materials.
• Remove all unnecessary reflective objects from the area near the beam’s path. This may
include items of jewelry and tools.
• Do not enter a designated Class 3b or Class 4 laser area (posted with a DANGER sign)
without approval from a qualified laser operator. Eye protection is required in these areas.
• Always wear laser safety eyewear in designated areas.
Safe Work Practices
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 51
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UCCLaser Safety
Keys to a successful laser safety program
Active involvement and support of laser users
Effective oversight by local (Departmental ) Laser Safety Officers
Support from management at all levels
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 52
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UCCLaser Safety
Safety Calculations
Maximum Permissible Exposure (MPE)
Wavelength
Exposure
CW or Pulsed
And ANSI Standards
Accessible Emission Limits (AEL)
Area of limiting aperture
MPE
Nominal Ocular Hazard Distance (NOHD)
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 53
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UCCLaser Safety
What is the duration time - t?
What is the duration time?
a. Is it intentional viewing? Duration time = exposure time.
b. Is it accidental exposure? i. Visible (400-700 nm), ocular
Duration time = 0.25 s
ii. <400 nm, ocular Duration time = 30000 s
iii. >700 nm, ocular Duration time = 100 s
iv. Visible or invisible, skin Duration time = 10 to 100 s
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 54
MPE: λ=10.6µm?
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UCCLaser Safety
MPE: λ=10.6µm
55
21000600,106.10 −⇒= Wmnmmµ
100 sec
λ=10.6µm?
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UCCLaser Safety
What is the duration time - t?
What is the duration time?
a. Is it intentional viewing? Duration time = exposure time.
b. Is it accidental exposure? i. Visible (400-700 nm), ocular
Duration time = 0.25 s
ii. <400 nm, ocular Duration time = 30000 s
iii. >700 nm, ocular Duration time = 100 s
iv. Visible or invisible, skin Duration time = 10 to 100 s
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 56
MPE: λ=980nm?
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UCCLaser Safety
MPE: λ=980nm CW
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 57
What is C4?
100 sec
λ=980nm
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UCCLaser Safety
MPE: λ=980nm – page 36
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 58
2275.0
4 21206618 −− === WmJmtCMPE
( ) ( )
63.310
1010
56.0
500/280500/700980
4
==
== −C st 100=
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UCCLaser Safety
How about laser pointers?What is the duration time?
a. Is it intentional viewing? NO Duration time = exposure time.
b. Is it accidental exposure? YES i. Visible (400-700 nm), ocular YES
Duration time = 0.25 s t=0.25s
ii. <400 nm, ocular Duration time = 30000 s
iii. >700 nm, ocular Duration time = 100 s
iv. Visible or invisible, skin Duration time = 10 to 100 s
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 59
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UCCLaser Safety
How about laser pointers?
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 60
22 5.2536.6 −− == WmJmMPE
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UCCLaser Safety
Angle of Apparent Source
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 61
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UCCLaser Safety
Angle of Apparent Source
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 62
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UCCLaser Safety
Accessible Emission Limits (AEL)
Area of limiting aperture MPE
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 63
LAAMPEAEL ×=
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UCCLaser Safety
10.6µm Laser
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 64
21000 −= WmMPE
221000 rWmAEL π×= −
mWm
1002
01101000
2
≈
=
.π
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UCCLaser Safety
980nm Laser
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 65
221 −= WmMPE
2221 rWmAEL π×= −
mWm
802
007021
2
..
≈
= π
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UCCLaser Safety
Laser Pointers
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 66
25.25 −= WmMPE
22525 rWmAEL π×= −.
mWm
12
0070525
2
≈
=
.. π
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UCCLaser Safety
Beam Type
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 67
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UCCLaser Safety
Beam Type
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 68
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UCCLaser Safety
Beam Type
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 69
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UCCLaser Safety
Angular Measures
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 70
Hint: look up steradian
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UCCLaser Safety
The Steradian
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 71
A graphical representation of 1
steradian. The sphere has
radius r, and in this case the area
of the patch on the surface
is A = r2. The solid angle
is Ω = A/r2 so in this case Ω = 1.
The entire sphere has a solid
angle of 4π sr ≈ 12.56637 sr.
http://en.wikipedia.org/wiki/Steradian
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UCCLaser Safety
Analog to Radians
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 72
http://en.wikipedia.org/wiki/Steradian
θrL =
rL
Ω= 2rA
steradians−Ω
r
A
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UCCLaser Safety
Steradian
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 73
r
A
What is the area?
=
44 22 θπ sinr
∫ ∫=π
θ
φθθ2
0
2
0
2ddrA sin
[ ] 20
22θ
θπ cos−= r
−=
212 2 θ
π cosr
2
2
44
≈
θπr
2
2
2
≈
θπrFor small angles:
θLarge
angles
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UCCLaser Safety
Surface Irradiance
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 74
Emits into all angles:
40W light bulb: 5W light
1 metre away:
22
25.0
4
5
4
5 −− ≈=== WmWmr
W
A
PI
ππ
[ ]ππ cos12 2 −= rA
24 rπ=
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UCCLaser Safety
Surface Irradiance
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 75
1 mW, Collimated
1 metre away:
22
22300
)001.0(
001.01 −− ≈=== WmWmr
mW
A
PI
ππ
2mm diameter beam2
rA π=→
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UCCLaser Safety
Surface Irradiance
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 76
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UCCLaser Safety
Spatial Coherence
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 77
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UCCLaser Safety
Retinal Irradiance
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 78
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UCCLaser Safety
Power Through Apertures
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 79
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UCCLaser Safety
Gaussian
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 80
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UCCLaser Safety
Gaussian Cross-section
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 81
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UCCLaser Safety
Large Beam
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 82
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UCCLaser Safety
Small Beam
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 83
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UCCLaser Safety
Intermediate Beam
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 84
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UCCLaser Safety
Optical Fibre
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 85
0
63
22
πω
λθ
zzd ==
71
263
.
zNAzd == θ
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UCCLaser Safety
Power through Aperture
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 86
![Page 87: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/87.jpg)
UCCLaser Safety
Bare Diode Laser
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 87
![Page 88: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/88.jpg)
UCCLaser Safety
Nominal Ocular HazardDistance (NOHD)
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 88
![Page 89: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/89.jpg)
UCCLaser Safety
NOHD
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 89
![Page 90: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/90.jpg)
UCCLaser Safety
Collimated
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 90
![Page 91: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/91.jpg)
UCCLaser Safety
Focussed
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 91
![Page 92: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/92.jpg)
UCCLaser Safety
Calculating NOHD
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 92
21 θθ ,
Emitted Power = P Beam Divergence = θ
Divergence Angles =
Beam Area:
2
2
2
=
θπrA
Irradiance:
21
2
4
θθπz
P
A
PI ==
⇒
22
212 θθπz
For small angles!
![Page 93: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/93.jpg)
UCCLaser Safety
Calculating NOHD
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 93
Insert: MPE for I Insert NOHD for z
( ) 21
2
4
θθπ NOHD
PMPE =→
21
2θπθMPE
PNOHD =
21
2
4
θθπz
PI =
![Page 94: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/94.jpg)
UCCLaser Safety
12mW at 980nm
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 94
221 −= WmMPE
100 mm
300 mm
![Page 95: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/95.jpg)
UCCLaser Safety
12mW at 980nm
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 95
Therefore:0
63
22
πω
λθ
zzd ==
( )( )
radm
m0880
10
9802222
0
..
===µπ
µ
πω
λθ
2
2
2
=
θπrA
![Page 96: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/96.jpg)
UCCLaser Safety
Calculating NOHD
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 96
m30.=
( )22088021
012022
.
.
ππθ==
MPE
PNOHD
![Page 97: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/97.jpg)
UCCLaser Safety
12mW at 980nm
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 97
100 mm
300 mm
mWAEL 80.=
![Page 98: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/98.jpg)
UCCLaser Safety
12mW at 980nm
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 98
Therefore:
526
828
63
63
.
.
=→
=→
d
d
0
63
22
πω
λθ
zzd ==
300
100
=
=
z
z
![Page 99: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/99.jpg)
UCCLaser Safety
12mW at 980nm
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 99
Therefore:
( )2631
dde
−−=η
0680
4670
.
.
=→
=→
η
η
( )mmd 7=
526
828
63
63
.
.
=→
=→
d
d
300
100
=
=
z
z
![Page 100: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/100.jpg)
UCCLaser Safety
12mW at 980nm
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 100
0680
4670
.
.
=→
=→
η
η
526
828
63
63
.
.
=→
=→
d
d
300
100
=
=
z
z
mWP
mWP
80
65
.
.
=→
=→
mWAEL 80.=
100 mm
300 mm
![Page 101: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/101.jpg)
UCCLaser Safety
12mW at 980nm
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 101
300 mm
What about safety to Class 1M?
![Page 102: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/102.jpg)
UCCLaser Safety
What is the duration time - t?
What is the duration time?
a. Is it intentional viewing? Duration time = exposure time.
b. Is it accidental exposure? i. Visible (400-700 nm), ocular
Duration time = 0.25 s
ii. <400 nm, ocular Duration time = 30000 s
iii. >700 nm, ocular Duration time = 100 s
iv. Visible or invisible, skin Duration time = 10 to 100 s
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 102
MPE: λ=980nm?
![Page 103: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/103.jpg)
UCCLaser Safety
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 103
WCAEL 4
41021 −×= .
![Page 104: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/104.jpg)
UCCLaser Safety
Class 1 @ λ=980nm
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 104
( ) ( ) 633101010 560500280500700980
4 ..// ==== −
C
mWAEL 4360.=
WCAEL 4
41021 −×= .
mWP 4360.= 0363012
4360.
.==→
mW
mWη
![Page 105: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/105.jpg)
UCCLaser Safety
Class 1 @ λ=980nm
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 105
( )2631
dde
−−=η
( ) ( )η−=−→ 12
63 lndd
( ) η−=→ −1
263dd
e
( )η−−=→
163
ln
dd
( )mm
mm436
036301
7.
.ln=
−−=
![Page 106: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/106.jpg)
UCCLaser Safety
Class 1 @ λ=980nm
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 106
mm412=
0
63
22
πω
λzd =
λ
πω
22
063dz =→
( ) ( )( )m
mmmz
µ
µπ
98022
10436
.
.=
![Page 107: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/107.jpg)
UCCLaser Safety
12mW at 980nm
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 107
mmz 412=
mWAEL 4360.=
?? mm
Class 1 @ λ=980nm
![Page 108: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/108.jpg)
UCCLaser Safety
An Easier Way!!
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 108
Calculate using MPE!
LAAMPEAEL ×=
LAA
AELMPE =→
2
2
3
2211
2
0070
104360 −−
=
×= Wm
WMPE .
.
.
π
![Page 109: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/109.jpg)
UCCLaser Safety
An Easier Way
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 109
λ=980nm
Or, use the MPE table with the long viewing time
![Page 110: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/110.jpg)
UCCLaser Safety
Class 1 @ λ=980nm
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 110
( ) ( ) 633101010 560500280500700980
4 ..// ==== −
C
26.11 −= WmMPE
2
42.3 −= WmCMPE
Previously calculated 11.22
![Page 111: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/111.jpg)
UCCLaser Safety
An Easier Way!!
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 111
mmm 420420 == .
( )208802211
01202
..
.
π=
22
πθMPE
PNOHD = Already know: θ
![Page 112: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/112.jpg)
UCCLaser Safety
How about laser pointers?What is the duration time?
a. Is it intentional viewing? NO Duration time = exposure time.
b. Is it accidental exposure? YES i. Visible (400-700 nm), ocular YES
Duration time = 0.25 s
ii. <400 nm, ocular Duration time = 30000 s
iii. >700 nm, ocular Duration time = 100 s
iv. Visible or invisible, skin Duration time = 10 to 100 s
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 112
![Page 113: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/113.jpg)
UCCLaser Safety
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 113
WCAEL 3
71093 −×= .
![Page 114: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/114.jpg)
UCCLaser Safety
Class 1 Laser
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland
ROINN NA FISICE
Department of Physics 114
WAEL µ866.=
( )
nm
C
6335817
10 5500150
3
==
= −
λ
λ
@.
.
WAEL µ390.=nm532=λ@
![Page 115: Lasers and Laser Safety - University College Cork Sa… · Laser Safety Causes of Laser Accidents Studies of laser accidents have shown that there are usually several contributing](https://reader034.vdocuments.site/reader034/viewer/2022052320/5f06c13a7e708231d41991dc/html5/thumbnails/115.jpg)
UCCLaser Safety
Coláiste na hOllscoile Corcaigh, Éire University College Cork, Ireland 115
ROINN NA FISICE
Department of Physics
Class 1
And, this is consistent with the numbers provided
in the laser safety manual