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Copyright © 2016 Raytheon Company. All rights reserved.
This document does not contain technology or Technical Data controlled under either the U.S. International Traffic in
Arms Regulations or the U.S. Export Administration Regulations.
Laser Safety Tutorial
34th International System
Safety Conference
Anish Donda, Micah Koons
August 11, 2016
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Tutorial Outline
Laser Overview/Operation
Laser Safety Terminology
Laser Classification
Laser Parameters
Laser Hazards
Laser Standards
Hazard Controls
Laser Safety Attributes
Laser Safety Tools
Example of Laser Safety Calculations
Summary
2016-09-12 2
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Tutorial Outline
Laser Overview/Operation
Laser Safety Terminology
Laser Classification
Laser Parameters
Laser Hazards
Laser Standards
Hazard Controls
Laser Safety Attributes
Laser Safety Tools
Example of Laser Safety Calculations
Summary
2016-09-12 3
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Laser Uses
Laser is an acronym for Light Amplification by the Stimulated Emission of Radiation
Lasers have many real-world applications– Commercial
DVD/Blu-ray Player
Laser Pointers
Scanners
Cutting
Welding
– Medical
Hair Removal
Cancer Diagnosis
Imaging
– Military
Communication
Ranging
Targeting
2016-09-12 4
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Optical Spectrum
The optical spectrum is a subset of the electromagnetic
spectrum– Consists of the ultraviolet (UV) , visible, and infrared (IR) radiation
2016-09-12 5
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Stimulated Emission
Conventional light sources (i.e. a light bulb) emits photons ‘spontaneously’
via a process known as spontaneous emission
In contrast, lasers emit photons via a process known as stimulated
emission
– Individual atoms or molecules are ‘stimulated’ to release energy before going through the
spontaneous emission process
– Stimulation is achieved by a causing a photon to collide with the atom or molecule
– Both photons now travel in phase and in the same direction
2016-09-12 6
Reproduced from
Henderson and
Schulmeister,
Laser Safety,
2004.
Reproduced from
Henderson and
Schulmeister,
Laser Safety,
2004.
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Fundamentals of Lasers
A typical laser is comprised of three fundamental elements– Lasing medium
Can be a solid, liquid or gas that emits radiation when excited
Major factor that determines the wavelength of the laser system
– Excitation mechanism
The energy source used to excite the lasing medium
– Typical excitation mechanisms include electricity from a power supply, a flash lamp, or the energy from another laser
– Optical cavity
Consists of mirrors to act as the feedback mechanism for light amplification
2016-09-12 7
REFLECTIVEMIRROR
PARTIALLY REFLECTIVE
MIRROR
OPTICAL CAVITY
EXCITATION MECHANISM
LASING MEDIUM
LASEROUTPUT
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Properties of Lasers
Lasers are different from regular light in that they are– Monochromatic
Laser light consists of essentially one wavelength
A typical light bulb, for example, emits light that contains various wavelengths
– Coherent
The waves of the laser radiation are in phase with each other
Light waves from a light bulb are a mixture of frequencies and wavelengths and are not in phase with one another
– Directional
Light output from a laser is highly directional
Unlike a typical light bulb which radiates in an omni-directional manner, laser energy diverges very slowly and is concentrated in a narrow cone that propagates in a single direction
Laser operating modes– Single pulse
– Repetitive pulse: multiple pulses emitted
– Continuous wave: continuous output for a period ≥ 0.25 sec
2016-09-12 8
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Tutorial Outline
Laser Overview/Operation
Laser Safety Terminology
Laser Classification
Laser Parameters
Laser Hazards
Laser Standards
Hazard Controls
Laser Safety Attributes
Laser Safety Tools
Example of Laser Safety Calculations
Summary
2016-09-12 9
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Some Laser Safety Terminology
Accessible Emission Limit (AEL)– The maximum accessible emission level permitted within a particular laser hazard class
Continuous Wave (CW)– A laser having a continuous output for a period > 0.25 seconds
Eye-Safe Laser– Class 1 laser product
– This term is frequently misused and is discouraged
Irradiance– Radiant power incident per unit area upon a surface, expressed in W/cm2
Maximum Permissible Exposure (MPE)– The level of laser radiation to which an unprotected person may be exposed without
adverse biological changes in the eye or skin
Pulsed Laser– A laser that delivers its energy in the form of a single pulse or a train of pulses that are
<0.25 seconds
Radiant Exposure– Surface density of the radiant energy received, expressed in units of J/cm2
2016-09-12 10
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Tutorial Outline
Laser Overview/Operation
Laser Safety Terminology
Laser Classification
Laser Parameters
Laser Hazards
Laser Standards
Hazard Controls
Laser Safety Attributes
Laser Safety Tools
Example of Laser Safety Calculations
Summary
2016-09-12 11
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Laser Classification
The most accepted standard for workplace safety of lasers, in
the U.S., is ANSI Z136.1– Most of the international community uses IEC 60825-1
Laser classification is based on the potential for a laser to
exceed the Accessible Emission Limit for unaided viewing and
optically aided viewing
The standard defines the following classes of lasers– Class 1, 1M
– Class 2, 2M
– Class 3R, 3B
– Class 4
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This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Class 1 Lasers
Class 1– A Class 1 laser is considered to be incapable of producing damaging radiation
levels during operation and is safe under all conditions of normal use
The MPE cannot be exceeded when viewing a laser with the naked eye or with
the aid of typical magnifying optics
Class 1M– Considered to be incapable of producing hazardous exposure conditions during
normal operation unless the beam is viewed with collecting optics
– The power when viewed by the naked eye is less than the Accessible Emission
Limit (AEL) for Class 1, but the power that can be collected into the eye by
magnifying optics is higher than the AEL for Class 1 and lower than the AEL for
Class 3B
2016-09-12 13
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Class 2 Lasers
Class 2– A Class 2 laser is considered to be safe because the blink reflex of the eye will
limit the exposure to no more than 0.25 seconds
– Emits in the visible portion of the spectrum (400 nm to 700 nm)
– Class-2 lasers are limited to 1 mW continuous wave
Power can be higher if the emission time is less than 0.25 seconds
Class 2M– A Class 2M laser is safe because of the blink reflex of the eye if not viewed
through optical instruments
– Similar to Class 1M, Class 2M lasers are potentially hazardous if viewed with
collecting optics
2016-09-12 14
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Class 3 Lasers
Class 3R– A Class 3R laser is considered safe if handled carefully, with restricted beam viewing
– Potentially hazardous under some direct and specular reflection viewing conditions if the
eye is appropriately focused and stable, but the probability of an actual injury is small
– Visible continuous lasers in Class 3R are limited to 5 mW.
– This laser will not pose either a fire hazard or diffuse reflection hazard
Class 3B– Class 3B lasers are hazardous under direct and specular reflection viewing, but diffuse
reflections are not harmful
– Typically not a fire hazard
– The AEL for continuous lasers in the wavelength range from 315 nm to far infrared is 0.5 W
– For pulsed lasers between 400 and 700 nm, the limit is 30 mJ
– Protective eyewear is typically required where direct viewing of a class 3B laser beam may
occur
2016-09-12 15
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Class 4 Lasers
Class 4 is the highest and most dangerous class of lasers
These lasers can burn skin, or cause permanent eye damage
as a result of direct, diffuse or indirect beam viewing
Class 4 lasers may ignite combustible materials, and thus may
represent a fire risk
Most industrial, scientific, military, and medical lasers are in
this category
2016-09-12 16
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Comparison of Laser Classes
ANSI Z136.1 IEC-60825-1 CDRH Examples
Class 1 Class 1 Class I Laser printers, CD/DVD
playersClass 1M Class 1M
Class 1C Laser hair removal
Class 2 Class 2 Class II Barcode scanners
Class 2M Class 2M Class IIa
Class 3R Class 3R Class IIIa Laser pointers
Class 3B Class 3B Class IIIb Laser light show
projectors, industrial
lasers, research lasers,
medical lasers
Class 4 Class 4 Class IV
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This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Tutorial Outline
Laser Overview/Operation
Laser Safety Terminology
Laser Classification
Laser Parameters
Laser Hazards
Laser Standards
Hazard Controls
Laser Safety Attributes
Laser Safety Tools
Example of Laser Safety Calculations
Summary
2016-09-12 18
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Laser Parameters
Wavelength– the distance (typically expressed in nm or µm) between successive crests of the
wave of light from the laser
Beam Diameter– The distance between diametrically opposed points in that cross-section of a
beam where the power/energy is 1/e (0.368) times that of the peak power/energy
Beam diameter is typically expressed in millimeters, centimeters, or inches.
2016-09-12 19
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Significance of 1/e
In laser safety calculations, beam diameter and beam
divergence are measured at the 1/e point– This is the position at which the beam irradiance has dropped to 1/e, or ~37% of
the on-axis value
– By joining the two points on each side of the curve, the corresponding circular
aperture centered on the axis of a Gaussian beam will enclose 63% of the total
beam power
The use of the 1/e criterion is not arbitrary– If the total power in the beam is divided by the area
defined by the 1/e diameter, the resulting value
(having units of power per unit area) is equal to the
peak (on-axis) value of the beam irradiance
Therefore, it defines the maximum or (from the safety
perspective) the worst-case value
2016-09-12 20
Reproduced from
Henderson and
Schulmeister,
Laser Safety,
2004.
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Laser Parameters cont.
Divergence– the increase in the diameter of the laser beam with distance from the beam
waist, where the irradiance (or radiant exposure for pulsed lasers) is 1/e times
the maximum value
– Beam divergence is expressed in radians or degrees
Power/Energy– CW Lasers
The output power of the laser expressed in watts (W)
Irradiance (power density in Watts/cm2)
– Pulsed Lasers
Total energy in a single pulse expressed in joules (J)
Radiant Exposure (energy density in Joules/cm2)
2016-09-12 21
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Laser Parameters cont.
Beam Distribution– the energy distribution of the laser beam
– Typical distributions include Gaussian and Top Hat (also known as Flat Top).
Beam Profile– Circular
– Elliptical
– Rectangular
Pulse Repetition Frequency (PRF)– The number of pulses occurring per second expressed in hertz (Hz)
2016-09-12 22
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Tutorial Outline
Laser Overview/Operation
Laser Safety Terminology
Laser Classification
Laser Parameters
Laser Hazards
Laser Standards
Hazard Controls
Laser Safety Attributes
Laser Safety Tools
Example of Laser Safety Calculations
Summary
2016-09-12 23
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Effects of Laser Radiation Laser radiation poses two concerns for the human body
– Damage to the eye
– Skin burns
The exact effect on the human body is dependent on various parameters including wavelength, power, and exposure duration
While hazards related to direct beam viewing are generally appreciated, the exposure to specular and diffuse reflections can also pose a hazard to skin and eyes and must be considered
2016-09-12 24
Intrabeam Viewing
Specular Reflection
Diffuse Reflection
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Effect of Laser Radiation cont.
Three principal mechanisms of laser damage to human tissue– Photothermal effect
Process in which laser radiation incident at the tissue surface is absorbed in
the underlying tissue, increasing the temperature of the tissue
– Photochemical effect
Process in which absorbed laser radiation directly modifies the chemical
structure of tissue components
– Photoacoustic effect
Acoustical effects result from a mechanical shockwave, propagated through
tissue, ultimately damaging the tissue
2016-09-12 25
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Laser Hazards
Majority of injuries involve the eye
26
Summary of reported laser accidents in the United States and their causes from 1964 to 1992
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Laser Hazards cont.
There are several contributing factors to laser related injury– Majority of accidents are due to lack of eye protection, incorrect eyewear, and
alignment procedures
27
Summary of reported laser accidents in the United States and their causes from 1964 to 1992
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Eye Hazards
The major hazard of laser radiation is from beams entering the eye– The eye is the organ most sensitive to light
– The eye can focus a beam of light to a spot 20 µm in diameter on the retina
The major parts of the eye that are susceptible to damage are– Cornea
Damaging wavelengths: 100 nm to 315 nm & 1400 nm to 1 mm
– Lens
Damaging wavelengths: 315 nm to 400 mm
– Retina (Fovea)
Damaging wavelengths: 400 nm to 1400 mm
2016-09-12 28
Cornea
Damage
Retina
Damage
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Skin Hazards
The skin is the largest organ of the body and, as such, is at
the greatest risk for coming in contact with the laser beam– The most likely skin surfaces to be exposed are the hands, head, or arms
Depending on the wavelength of the laser, different layers of
the skin can be damaged
2016-09-12 29
Sliney D H and
Wolbarsht M 1980
Safety with Lasers and
Other Optical Sources
(New York: Plenum)
Wavelength Skin Effects
Ultraviolet C (0.200-0.280
μm)
Erythema (sunburn)
Skin cancer
Ultraviolet B (0.280-315 μm) Accelerated skin aging
Increased pigmentation
Ultraviolet A (0.315-0.400
μm)
Pigment darkening
Skin burn
Visible (0.400-0.780 μm) Photosensitive
reactions
Skin burn
Infrared A (0.780-1.400 μm) Skin burn
Infrared B (1.400-3.00 μm) Skin burn
Infrared C (3.00-1000 μm) Skin burn
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Other Laser Hazards
Fire/Explosion Hazards– The high amount of radiant power within the beam of a Class 4 laser (and
sometimes focused beams of lower classes), can be enough to ignite materials including flammable liquids, plastics, wood, and fabrics
– Laser beams can also cause explosions in combustible gases or in high concentrations of airborne dust
Thermal Hazards– Objects in the path of a laser beam (i.e. mirrors, beam stops, etc.) may get
extremely hot and could pose a burn hazard
Industrial Hygiene– Potential hazards associated with compressed gases, cryogenic materials, toxic
and carcinogenic materials and noise
– Adequate ventilation shall be installed to reduce noxious or potentially hazardous fumes and vapors, produced by laser welding, cutting and other target interactions
2016-09-12 30
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Other Laser Hazards cont.
Collateral Radiation– Certain lasers may emit other forms of radiation in addition to the laser beam
UV radiation from gas laser discharge tubes
RF energy associated with some plasma tubes
X-rays may be generated from electrical equipment (>15kV)
Hazardous Material– The materials used as the laser medium or excitation mechanism may be
hazardous
– Any compresses gases used
Electrical Hazards– Laser can use high voltage and contain large capacitors
– Electrical components should be enclosed to prevent accidental contact
– Interlocks should be used as appropriate
2016-09-12 31
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Tutorial Outline
Laser Overview/Operation
Laser Safety Terminology
Laser Classification
Laser Parameters
Laser Hazards
Laser Standards
Hazard Controls
Laser Safety Attributes
Laser Safety Tools
Example of Laser Safety Calculations
Summary
2016-09-12 32
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Laser Regulations and Standards
U.S. Commerce– Laser products sold in or imported into the United States must comply with the
Federal Performance Standard for Laser Products issued by the Food and Drug
Administration (FDA), Center for Devices and Radiological Health (CDRH), in
Title 21, Code of Federal Regulations, Subchapter J, Parts 1040.10 and 1040.11
The Federal Laser Standards require laser products to incorporate certain
safety features
– In order for a laser to comply, manufacturers must (note, not an exhaustive list):
Meet the performance standards in the CFR
– Protective housing, key switches, interlocks, attenuators, labelling, etc.
Generate user manuals
Generate a Product Report and file it with the CDRH
Generate a certification test procedures
Record keeping and annual reports
2016-09-12 33
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
DoD Laser Requirements
U.S. Department of Defense (DoD)– In 1976, the FDA Commissioner allowed the DoD, or its components, to exempt certain
military laser products from the provisions of the Federal Laser Standard
This exemption applies to DoD lasers used for actual combat or combat training or those classified in the interest of national security
The exemption was granted with the following provisions:
– Laser product specifications must include, to the extent practicable, the safety features required by the FDA standard
– Laser product specifications will be supplemented with safety controls specified by DoD
– DoD exempted laser products will be clearly identified through labeling
– MIL-STD-1425A
A provides uniform requirements for safe design of military equipment containing lasers
– U.S. Army
Technical Bulletin Med 524 – Control of Hazards to Health from Laser Radiation
– U.S. Navy
OPNAVINST 5100.27B – Navy Laser Hazards Control Program
– U.S. Air Force
AFOSH 48-139 – Air Force Laser Radiation Protection Program
– Mil-Std-1425A and each of the military laser safety programs use ANSI Z136.1 for laser classification and hazard evaluation
2016-09-12 34
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Standard for Safe Use of Lasers
ANSI Z136.1-2014 is the most widely used standard for classifying lasers and ensuring they are used safely by specifying the appropriate controls– Provides a means for calculating the laser class
– Provides control measures to ensure no exposure above the applicable MPE
– Facilitates the calculation of the MPE, OD and NOHD
– Provides labeling requirements
– Discusses non-beam hazards and mitigation techniques
The standard prescribes a 2-step process– Determine the appropriate class of the
laser or laser system
– Comply with the requirements specified for that class
IEC 60825-1 is an equivalent international standard
2016-09-12 35
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Laser Regulations/Specifications
Use of laser may also be controlled by State and Local
regulations
Example– The Department of Safety and Health Services in the state of Texas requires that
all Class 3B and 4 laser be registered
Registration also includes the identification of a qualified Laser Safety Officer
All Class 3B and 4 lasers need to be inventoried annually
– Title 25, Texas Administrative Code, Section 289.301
Mandates that Class 3B and 4 lasers be registered
Provides regulations for controlling laser radiation hazards
It is recommended to check with your State and Local
regulations for laser registration and operation requirements
2016-09-12 36
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Tutorial Outline
Laser Overview/Operation
Laser Safety Terminology
Laser Classification
Laser Parameters
Laser Hazards
Laser Standards
Hazard Controls
Laser Safety Attributes
Laser Safety Tools
Example of Laser Safety Calculations
Summary
2016-09-12 37
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Control Measures
Purpose– Reduce the likelihood of exposure to beam and non-beam hazards
Types of controls– Engineering (1st priority)
Inherent/inbuilt safety features
– Procedural/Administrative
Signs and notices
Operational activities including policies and procedures
Appointment of LSO, Training, Audits
– Personal protective Equipment (PPE) (Last priority)
Goggles
Gloves
Respirators
2016-09-12 38
Order of Precedence
Engineering, Procedural/Administrative, then PPE
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Hazard Controls
Engineering controls– First Line of Defense!
– More reliable than other controls
Examples– Protective Housing
– Safety Interlocks
– Beam Stop or Attenuator
– Beam Enclosures
– Laser Emission Indicators
– Key Control
– Protective Barriers and Curtains
2016-09-12 39
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Hazard Controls
Procedural/Administrative Controls– Standard Operating Procedures
– Alignment Procedures
– Limitations on Spectators
– Personnel Training
– Danger/Warning/Caution Signs
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CAUTION!
VISIBLE DIODELASER RADIATION
ANSI CLASS 2LASER PRODUCT
LASER RADIATIONDO NOT STARE
INTO BEAM
= 650 nm
Power < 200 W
DANGER!!LASER RADIATION
AVOID EYE OR SKINEXPOSURE TO DIRECT OR SCATTERED RADIATION
INVISIBLE CARBON-DIOXIDELASER RADIATION
W AVELENGTH: 10.6 mPOWER: 10 Watts
ANSI CLASS 4LASER PRODUCT
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Military Exemption & Labeling
Prior to the implementation of the federal standard, it was
recognized that military lasers have unique functional
requirements which sometimes preclude the incorporation of
some safety features
FDA issued Exemption Number 76EL-01DOD to the
Department of Defense on July 29, 1976. See 21CFR1010.5
2016-09-12 41
Exemption stipulations– FDA stipulated that the DoD must
establish alternative control measures
– Mil-Std-1425 (Safety Design
Requirements for Military Lasers and
Associated Support Equipment) was
developed
– Exemption label has to be “affixed or
inscribed” on the product
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Personal Protective Equipment (PPE)
– Protective Eyewear and Clothing
Eye-protection devices (Goggles)
– Eyewear has to be marked with OD
(Optical Density) and wavelengths
– Multi-band eyeware eliminates the need
to change for various wavelengths
– Visible transmittance can become
problematic
– Goggles can fog and be uncomfortable
2016-09-12 42
In general, other controls should serve as primary protection rather
than depending on employees to use protective eye wear
Skin protection can best be achieved through engineering controls
– For UV (0.200-0.400 m), skin covers and/or sun-screen creams
– For the hands, gloves will provide some protection
– Laboratory jacket or coat can provide protection for the arms
– For Class IV lasers, flame-resistant materials may be needed
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Facility
Entryway Interlocks– Use switches, motion detectors, etc. to deactivate the laser if unexpected entry occurs
Procedural Entryway Controls– Blocking barrier, screen, or curtain may be used inside the controlled area to prevent the
laser light from exiting the area
– Warning light or sound is required outside the entryway that operates when the laser is
energized and operating
2016-09-12 43
Reproduced
from ANSI
Z136.1-2014,
pg. 97
Entryway Warning Systems– Laser activation warning light installed
outside the entrance to each laser room
– Light to be conspicuously different from
general lighting
– Laser warning sign shall be posted both
inside and outside the laser-controlled
area
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Class 4 Laser Controls--General Requirements
Supervision by individual knowledgeable in laser safety
Entry of any noninvolved personnel requires approval
Appropriate laser protective eye wear must be provided all
personnel within the laser controlled area
Beam path located and secured above or below eye level for
any standing or seated position in the facility
Windows, doorways, open portals, etc., of an enclosed facility
should be covered or restricted to reduce any escaping laser
beams below appropriate ocular MPE level
Require storage or disabling of lasers when not in use
2016-09-12 44
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Tutorial Outline
Laser Overview/Operation
Laser Safety Terminology
Laser Classification
Laser Parameters
Laser Hazards
Laser Standards
Hazard Controls
Laser Safety Attributes
Laser Safety Tools
Example of Laser Safety Calculations
Summary
2016-09-12 45
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Typical Exposure Durations
0.25 seconds: blink reflex and aversion response– Time for typical head movement, eye movement, eyelid closure when exposed
to bright light.
– Can be used for visible laser only.
10 seconds: Worst case time used for exposure to near IR
(700 nm to 1400 nm) laser sources.– Natural eye motions dominate for periods longer than 10 seconds.
600 seconds: Worst case time for viewing diffuse reflections– Typical time personnel could be exposed during alignment tasks
30,000 seconds: The time that represents one typical day of
occupational exposure.– 8 hrs = 28,800 s rounded up to 30,000 s
– Time that is used to determine the MPE for OD calculations when long term
exposure is possible
2016-09-12 46
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Accessible Exposure Limit (AEL)
Definition: The maximum accessible emission level permitted
within a particular laser hazard class
2016-09-12 47
Laser Safety Attributes
Dependencies– MPE (with all of its dependencies)
– Limiting aperture
Class 1 AEL = MPE x area of limiting aperture
Exposure
Concern
Limiting Apertures (mm)
Retina 7
Cornea 1.0, 1.5 t 0.375 , 11.0
Skin 3.5 for 180 nm to 100 um
11.0 for 100 um to 1,000 um
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Optical Density (OD)
Definition: Logarithm to the base ten of the reciprocal of the transmittance (). Transmittance is defined as the ratio of the total transmitted radiant power to the total incident radiant power.
Where:– Hp is the potential eye exposure expressed in the same units as the appropriate
MPE
– MPE is calculated based on Tables 5 through 5f in ANSI Z136.1-2014.
The higher the OD value the greater the attenuation provided
2016-09-12 48
Laser Safety Attributes
Rating Transmittance reduce by
OD 1 Reduced by a factor of 10
OD 6 Reduced by a factor of 1,000,000
𝑂𝐷 = log10𝐻𝑝
𝑀𝑃𝐸𝑂𝐷 = − log101
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Nominal Ocular Hazard Distance (NOHD)
Definition: 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 does not
exceed the applicable MPE
Where:– Where ϕ is the divergence of the laser beam as measured at the 1/e point in
radians and Φ is the radiant power
– Assuming no atmospheric loss
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Primary driver for the NOHD is the divergence of the laser beam.
The tighter the divergence of the laser beam, the larger the NOHD.
Laser Safety Attributes
𝑁𝑂𝐻𝐷 =1
∅1/𝑒
1.27Φ
MPEcm
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Nominal Skin Hazard Distance (NSHD)
Definition: The distance along the axis of the unobstructed
beam from the laser beyond which the irradiance or radiant
exposure is not expected to exceed the skin MPE
Where:– Where ϕ is the divergence of the laser beam as measured at the 1/e point in
radians and Φ is the radiant power
– The Skin MPE is taken from ANSI Tables 7a-7c
– Above equation assumes no atmospheric loss
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Laser Safety Attributes
𝑁S𝐻𝐷 =1
∅1/𝑒
1.27Φ
MPEcm
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Definition: Aided viewing is viewing that takes place using a
telescopic (binocular) or magnifying optic
For typical magnifying optics– Transmissivity
70% for 700 nm to 2800 nm
90% for 400 nm to 700 nm
NOHD impact– NOHD will be larger compared to unaided viewing
OD impact– OD may increase depending on the beam size
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Aided viewing can have a significant impact on OD and NOHD
Aided Vs. Unaided Viewing
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Atmospheric Attenuation
Definition: The decrease in the radiant flux as it passes
through the atmosphere (i.e. any absorbing and/or scattering
medium)
Example values for 1030 nm wavelength
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Laser Safety Attributes
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Tutorial Outline
Laser Overview/Operation
Laser Safety Terminology
Laser Classification
Laser Parameters
Laser Hazards
Laser Standards
Hazard Controls
Laser Safety Attributes
Laser Safety Tools
Example of Laser Safety Calculations
Summary
2016-09-12 53
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Laser Hazard Analysis Software (LHAZ), v6.0
https://gumbo2.wpafb.af.mil/portal USAFSAM ESOH Service Center
esoh.service.center@wpafb.af.mil
LHAZ 6.0 is a laser hazard assessment program that combines a maximum
permissible exposure (MPE) calculator with the American National Standards
Institute (ANSI) classification routine. The program also includes a hazard
assessment and range equation worksheets to aid trained laser safety officers
during laser safety and hazard control assessments.
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Tools
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
LIA Laser Evaluator https://www.lia.org/evaluator/ This innovative System provides a reliable way to easily double-check laser
safety calculations. It is based on the ANSI Z136.1 American National
Standard for Safe Use of Lasers and will perform repeated calculations of
maximum permissible exposure (MPE), optical density (OD), nominal ocular
hazard distance (NOHD), nominal hazard zone (NHZ), and laser hazard
classification.
Easy Haz https://lasersafetyu.kentek.com/product/ EASY HAZ™ LSO Edition is software designed to provide comprehensive
laser hazard analysis information for Laser Safety Officers. It includes all the
most useful hazard calculations and additional calculations of laser parameters
and hazard values found nowhere else. EASY HAZ™ LSO is the best choice
for LSOs in any environment, LSOs with multiple lasers using different beam
profiles, and LSOs performing comprehensive diffuse reflection calculations
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Tools
Tools are not meant to be a replacement for a knowledgeable laser safety officer (LSO)
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Tutorial Outline
Laser Overview/Operation
Laser Safety Terminology
Laser Classification
Laser Parameters
Laser Hazards
Laser Standards
Hazard Controls
Laser Safety Attributes
Laser Safety Tools
Example of Laser Safety Calculations
Summary
2016-09-12 56
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International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Laser Calculation Example
The following examples will assume that we have an off-the-
shelf “purple” laser with the following parameters from the
manufacturer
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Parameter Value
Wavelength 405 nm
Power 15 mW
Mode CW
Beam Profile Circular
Beam Distribution Gaussian
Beam Diameter at 1/e 1.25 mm
Beam Divergence at 1/e 0.41 mrad
Class 3B
405 nm
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Laser Classification
AEL is the parameter that is used to establish the
classification of the laser AEL is computed by taking the given MPE multiplied by the appropriate area of
the limiting aperture
Looking at Table 5b we get an MPE = CB x 10-4 where CB is
taken from Table 6a. CB = 1 for 400-450 nm
Therefore the Class 1 MPE = 1 x 10-4 W/cm2
2016-09-12 58
Reproduced from ANSI Z136.1-2014
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Laser Classification (cont’d)
Multiplying the MPE by the area of a dilated pupil we get
AEL = 10-4 W/cm2 x (π x (0.7cm/2)2 = 38.5x10-6 W
AEL = 38.5μW for a Class 1 laser at 405 nm
Since 15 mW > 38.5 μW our laser is not a Class 1
For Class 2 and 2M the AEL is 1.0 mW (ANSI 3.2.4.3)– Our laser exceeds 1.0 mW so we are not a Class 2 laser
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Reproduced from ANSI Z136.1-2014
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Laser Classification (cont’d)
For Class 3R the laser has to be less than 5 times the Class 2
AEL or 5mW.– Our laser is greater than 5 mW so we are not a Class 3R
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Our laser is a Class 3B
because we are over the
3R limit but less than the
3B limit of 0.5 W
Reproduced from ANSI Z136.1-2014
paragraph 3.3.3.1
Reproduced from LHAZ 6.0.0.17
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MPE for Hazard Assessment
From a hazard assessment standpoint we look at the MPE at a 0.25s exposure time (aversion response time)
MPE for hazard assessment can be calculated as follows:– 1st we determine the MPE from Table 5b
We then convert the energy density to power density by dividing the MPE by the exposure duration (1 J = 1 W·sec)
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Reproduced from ANSI Z136.1-2014
MPE = 1.8 x t0.75 mJ/cm2 = 1.8 x 0.250.75 = 0.636 mJ/cm2
MPE = 0.636 mJ/cm2 / 0.25 s = 2.55 mW/cm2
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MPE for Hazard Assessment
(cont’d)
To remain safe we need to make sure that we keep personnel
exposed to an irradiance < 2.55 mW/cm2
Note that, with no attenuation, our laser irradiance is:
2016-09-12 62
Exposure mitigations– Provide suitable protective covers to prevent emissions
– If emissions are necessary, use engineering controls, administrative/procedures,
and/or laser goggles with an appropriate optical density
Eo = 15 mW / (π x (0.125/2)2 = 1.22 W/cm2
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OD Calculation
As discussed earlier, OD can be
calculated using this equation:
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𝑂𝐷 = log1038.9 𝑚𝑊/𝑐𝑚2
2.55 𝑚𝑊/𝑐𝑚2 = 1.2
which we round up to 2.0 to
specify a goggle OD
𝑂𝐷 = log10𝐻𝑝
𝑀𝑃𝐸
Hp= 15 mW / (π x (0.7cm/2)2 = 38.9 mW/cm2 and
MPE = 2.55 mW/cm2
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OD Calculation (cont’d)
OD can be calculated using power
density or energy density
Hp is the potential eye exposure
(15 mW) expressed in the same units
as the appropriate MPE
Note that, in our specific example, where the beam is smaller than the
limiting aperture we average the beam over the area of the limiting
aperture to compute the MPE for the OD calculation
2016-09-12 64
Reproduced from ANSI Z136.1-2014, paragraph 4.4.4.2.3.1
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NOHD Calculation
From our prior slides we
know that:
2016-09-12 65
Therefore:
As shown in the paper a more exact
formula is:
𝑁𝑂𝐻𝐷 =1
∅1/𝑒
1.27Φ
MPEcm
𝑁𝑂𝐻𝐷 =1
0.41 𝑥 10−3 𝑟𝑎𝑑
1.27(15 mW)
2.55 mW/𝑐𝑚2= 6666 cm = 66.7 m
𝑁𝑂𝐻𝐷 =1
∅ 1 𝑒
−𝐷𝑓2
𝑙𝑛 1 −𝐴𝐸𝐿𝑃
− 𝐷 1 𝑒2
𝑁𝑂𝐻𝐷 =1
0.41−3−0.72
𝑙𝑛 1−1.001
15
− 0.1252 = 64.9 m
MPE = 2.55 mW/cm2
AEL = 2.55 mW/cm2 (π x (0.7 cm/2)2 = 1.001 mW
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NSHD
2016-09-12 66
Looking at Table 7b we get the MPE = 0.2 x CA where CA is taken from
Table 6a and is equal to 1.0
Since the available power, 15 mW is less than the 19.24 mW AEL
there is no skin hazard therefore the NSHD = 0 m.
Reproduced from ANSI Z136.1-2014
MPE = 0.2 x 1.0 = 0.2 W/cm2
AEL = 0.2 W/cm2 (π x (0.35 cm/2)2 = 19.24 mW
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NSHD (cont’d)
2016-09-12 67
If we increase the power to 20 mW we get:
𝑁𝑆𝐻𝐷 =1
0.41−3−0.352
𝑙𝑛 1−19.24
15.0
− 0.1252
𝑁𝑆𝐻𝐷 =1
0.41−3−0.352
𝑙𝑛 −0.28− 0.1252 = 0 m
Must be a positive number
𝑁𝑆𝐻𝐷 =1
0.41−3−0.352
𝑙𝑛 1−19.24
20.0
− 0.1252 = 3.6 m
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Tutorial Outline
Laser Overview/Operation
Laser Safety Terminology
Laser Classification
Laser Parameters
Laser Hazards
Laser Standards
Hazard Controls
Laser Safety Attributes
Laser Safety Tools
Example of Laser Safety Calculations
Summary
2016-09-12 68
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Summary Lasers have many practical uses
– Personnel safety must be managed
A typical laser consists of three fundamental elements– Excitation mechanism
– Lasing medium
– Optical cavity
Lasers can be classified into 4 basic laser classes
Lasers can be harmful to humans and can lead to eye and skin damage
Basic properties of laser beams for performing safety calculations include– Wavelength
– Output power/energy
– Pulse Repetition Frequency
– Beam diameter, beam divergence, beam profile, and beam distribution
Protecting personnel includes– Engineering controls
– Administrative/procedural controls
– Personal protective equipment
Three calculated parameters to ensure safe operation include– Optical Density
– Nominal Ocular Hazard Distance
– Nominal Skin Hazard Distance
Laser safety calculations can be performed using available software
2016-09-12 69
This document does not contain technology or Technical Data controlled under either the U.S.
International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
Biography
Anish Donda, Raytheon Space and Airborne Systems, 2501
West University Drive, McKinney, Texas 75071, USA,– Telephone: 972-344-4060, Email: akdonda@raytheon.com.
– Anish Donda is a Principal Systems Engineer for Raytheon Space and Airborne
Systems in McKinney, Texas. He received his BS in Computer Engineering from
the University of Arizona in 2000, his MS in Computer Engineering from the
University of Arizona in 2003, and his MBA from the University of Arizona in
2005. He has worked for 17 years in the System Safety group at Raytheon with
the last 5 years as a system safety engineer in the advanced electro-optical
systems group specializing in laser safety.
Micah Koons, P.E., Raytheon Space and Airborne Systems,
2501 West University Drive, McKinney, Texas 75071, USA,– Telephone: 972-952-6665, Email: micah.koons@raytheon.com
– Micah Koons is a Section Manager for Raytheon Space and Airborne Systems in
McKinney, Texas. He received his BS in Electrical Engineering from Texas A&M
University in 1982. He has worked for 32 years providing reliability and system
safety support for advanced radar and electro-optical programs.
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