LASER SAFETY
Texas State University | San Marcos
Objectives
IDENTIFY what the acronym LASER means and briefly DESCRIBE how a laser performs it function. (LST.OBJ.001)
LIST the characteristics of a laser beam. (LST.OBJ.002)
DIFFERENTIATE between a Continuous Wave Laser and a Pulsed Laser. (LST.OBJ.003)
Objectives (continued)
LIST the five types of lasers and briefly DESCRIBE their attributes. (LST.OBJ.004)
LIST several types of laser excitation sources. (LST.OBJ.005)
IDENTIFY the American National Standards Institute Laser Classifications. LST.OBJ.006
Objectives (continued)
LIST three areas in which lasers have been used. (LST.OBJ.007)
Describe the two common types of laser pointers. (LST.OBJ.008)
List the criteria used by the FDA to determine laser pointer classification and the required labeling on each class of laser pointer. (LST.OBJ.009)
Objectives (continued)
IDENTIFY the three primary mechanisms of tissue injury associated with laser radiation exposure. LST.OBJ.010
MATCH the specified laser wavelength to the part of the eye that is most affected. LST.OBJ.011
Objectives (continued)
IDENTIFY the two mechanisms by which laser radiation may potentially cause skin injury. LST.OBJ.012
IDENTIFY the three basic categories of controls used in laser environments to provide a degree of protection from possible laser radiation injury and GIVE several examples of each type of control. LST.OBJ.013
Objectives (continued)
IDENTIFY other non-beam hazards that are possible in laser environment and GIVE an example of each. LST.OBJ.014
MATCH the following laser related terms to their corresponding meaning:
Accessible Exposure Limit – Nominal Hazard Zone
-iffuse Reflection – Specular Reflection
Intrabeam Exposure – Radiant Exposure
Irradiance – Peak Power
Maximum Permissible Exposure
LST.OBJ.015
TxState Laser Safety Program
Laser Safety Training Manual
Laser Safety Manual
Texas Department of State Health Services Bureau Radiation Control
25 TAC §289.301
LASER
Acronym for:
Light
Amplification by the
Stimulated
Emission of
Radiation.
Laser
Emits non-ionizing electromagnetic radiation that is ultraviolet, visible, or infrared light.
Lasers now capable of emission in X-ray frequency.
Laser Light
Monochromatic
One wavelength or color
Directional
Does not expand as quickly as ordinary light
Coherent
Waves of light generated in phase with each other.
Basic Operating Concept
Electrons moved from ground state to higher energy state.
When electrons descend to ground state, photons emitted of specific wavelength.
Photons oscillate in mirrored resonator
Increases intensity by stimulating emission of additional photons of same wavelength and phase.
Photons escape via output coupler
Continuous Wave Lasers
Operated in a continuous mode for at least a period of .25 seconds.
Output expressed as the average power (watts).
Irradiance (Power Density)
Expressed in W/cm2
Function of the beam power divided by beam area
Beam area a function of:
Beam size at aperture
Beam divergence
Distance from aperture
> irradiance > potential hazard
Pulsed Lasers
Delivers energy in the form of a:
single pulse
train of pulses
Delivered in less than .25 seconds.
Output expressed as the total energy per pulse (joules).
Radiant Exposure (Energy Density)
Normally expressed in Joules/cm2
Function of:
Pulse Density
Pulse duration
Pulse frequency
> radiant exposure > potential hazard
Laser Types
Solid state
Ruby crystals and neodymium-doped glasses and crystals most common solid laser media.
Gas
A pure gas or mixture of gases (i.e. Helium-Neon or Carbon dioxide)
Liquid
Inorganic dyes contained in glass vessels most common.
Laser Types
Excimer
Uses reactive gas with inert gas. Dimer produced which when lased produce UV
Semi-conductor (most common laser)
Gallium arsenide most common semiconductor material
Excitation Sources
Types
Flash lamps
Plasma discharge tubes
High voltage current
Radio frequency
Some lasers used to “pump” other lasers.
Excitation device can present serious non-beam hazard
ANSI Classification
ANSI (and LIA) – ANSI 2000 has developed four categories of hazard potential.
Based on the ability of optical emissions from a laser system to produce injury to personnel.
The higher the classification number, the greater the hazard potential.
Class I
May produce visible or invisible laser radiation.
Do NOT pose a hazard under normal operating conditions.
Class II
Low-power visible light lasers or laser systems that:
Do NOT normally present a hazard because of the normal human aversion response
Blinking
eye movement, etc.
Potential for hazard if viewed directly for extended period of time
similar to many conventional light sources
Class IIIa
Normally not injure the eye if viewed for momentary period (within the aversion response period) with the unaided eye
May present a greater hazard if viewed using collection optics.
Must carry a caution label.
Class IIIa
Another group of Class IIIA lasers have DANGER labels
Capable of exceeding permissible exposure levels for the eye in 0.25 seconds.
Still poses a low risk of injury.
Class IIIb
Produce eye damage if viewed directly.
Includes intrabeam viewing of specular reflections.
Normally do not produce a hazardous diffuse reflection.
Class IV
Produce retinal damage from direct or specular reflections.
May also produce hazardous diffuse reflections.
May produce significant eye and skin radiation hazards as well as fire hazards.
Laser Applications
Industry
Can be used to melt, vaporize, drill material in precise manner
Many other
Scientific Research
Used to study molecular structure
Selectively induce chemical reactions
Medicine
Cut and cauterize without damaging healthy tissue
Eye surgery
Laser Applications
Military
Guidance systems for missles, aircraft, and satellites
Communication
Laser light can carry 1000 times number television channels now carried by microwave
Play audio compact discs and videodiscs
Laser Pointers
Not dangerous when used properly.
Looking directly into beam for > 1 ½ minutes can result in eye injury.
Flashblindness
Split second look
Similar to effect in flash photography
Vision returns to normal after few moments
No long term effect
Red Laser Pointers
670 nm
1000’ range
Rarely sold today
650 nm
2000’ range
Adequate most purposes
635 nm
4000’ range
Usefule outdoors unless sun brightly shining
Green Laser Pointers
532 nm
Eye more sensitive to green light
Reason for exceptionally brilliant visibility
Frequency doubled diode
Uses infrared diode (2 x 1064)
Low efficiency
500 mW into diode
Few mW out of diode
FDA Regulation
Laser pointers are regulated according to their power output.
Class II laser Pointers
< 1 mW
CAUTION Label required
Class IIIb Laser Pointers
1 to 5 mW
WARNING Label required
Biological Effects
Tissues at risk are:
Eyes
Skin
Three mechanisms of injury
Thermal effects
Photochemical effects
Acoustical transient effects
Eye Injury Potential
Related to laser wavelength
< 300 nm & > 1400 nm
Cornea
> 300 < 400 nm
Aqueous Humor
Iris
Lens
Vitreous humor
> 400 < 1400 nm
Retina
Eye Injury Potential
Retinal Injury
May be severe due to focal magnification
Optical gain ~ 105
Example
1 mW/cm2 into eye ≈100 W/cm2 on retina
Lesions
Caused when choroids blood flow cannot regulate retina heat loading
Picture of burned retina.
Skin Injury Potential
Thermal Injury
Acute exposures to high power lasers beams
Direct contact with beam or specular reflection
Not usually serious
Photochemically induced
Chronic exposure to scattered UV radiation
Direct contact with UV beam, specular reflection, or diffuse reflection
Can cause minor or severe sunburn
May promote formation of cancer
Laser Safety
Responsibility of each individual
Three categories of controls
Engineering
Administrative and Procedural
Personal Protective Equipment
Work better together than singly.
Engineering Controls
Normally designed and built into laser equipment
Protective housing
Master key switch
Beam stops/attenuators
Activation warning system
Interlocked doors
Airborne emissions controls
Administrative & Procedural Controls
No physical barrier
Examples
Area postings
Standard Operating procedures
Maintenance procedures
Administrative procedures
Alignment procedures
Personal Protective Equipment
Eye protection
Essential for beam alignments
Must be marked with:
Optical Density
Laser Wavelength
Must be comfortable
Skin protection
Gloves
UV face shield
Lab coat
Non-Beam Hazards
Industrial Hygiene
Associated with compressed gases, cryogenic materials, toxic & carcinogenic materials
Adequate ventilation to reduce fumes & vapors
Explosion Hazards
High pressure arc lamps, filament lamps, or laser welding equipment
Laser targets and elements of optical train
Non-Beam Hazards
Non-beam Optical Radiation Hazards
Laser discharge tubes, pumping lamps, and laser welding plasma
Electrical Hazards
Installation and connection
Conduit versus flexible cord
Noise Hazards
High noise levels during operation
Non-Beam Hazards – Physical
Factors that contribute to injury are:
Fire
Explosions
electrocutions
From
arc and filament lamps
capacitors
wiring
power supplies
circuits
solvents
gases
Non-Beam Hazards – Chemical
Various chemical agents:
Dyes
Solvents
Gases
Laser-generated airborne contaminants
Dusts
Mists
Fumes
Smokes
Mastering Light:
An Introduction to Laser Safety and Hazards
Objectives
IDENTIFY what the acronym LASER means and briefly DESCRIBE how a laser performs it function. (LST.OBJ.001)
LIST the characteristics of a laser beam. (LST.OBJ.002)
DIFFERENTIATE between a Continuous Wave Laser and a Pulsed Laser. (LST.OBJ.003)
Objectives (continued)
LIST the five types of lasers and briefly DESCRIBE their attributes. (LST.OBJ.004)
LIST several types of laser excitation sources. (LST.OBJ.005)
IDENTIFY the American National Standards Institute Laser Classifications. LST.OBJ.006
Objectives (continued)
LIST three areas in which lasers have been used. (LST.OBJ.007)
Describe the two common types of laser pointers. (LST.OBJ.008)
List the criteria used by the FDA to determine laser pointer classification and the required labeling on each class of laser pointer. (LST.OBJ.009)
Objectives (continued)
IDENTIFY the three primary mechanisms of tissue injury associated with laser radiation exposure. LST.OBJ.010
MATCH the specified laser wavelength to the part of the eye that is most affected. LST.OBJ.011
Objectives (continued)
IDENTIFY the two mechanisms by which laser radiation may potentially cause skin injury. LST.OBJ.012
IDENTIFY the three basic categories of controls used in laser environments to provide a degree of protection from possible laser radiation injury and GIVE several examples of each type of control. LST.OBJ.013
Objectives (continued)
IDENTIFY other non-beam hazards that are possible in laser environment and GIVE an example of each. LST.OBJ.014
MATCH the following laser related terms to their corresponding meaning:
Accessible Exposure Limit – Nominal Hazard Zone
-iffuse Reflection – Specular Reflection
Intrabeam Exposure – Radiant Exposure
Irradiance – Peak Power
Maximum Permissible Exposure
LST.OBJ.015