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LASER SAFETY

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)

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LASER SAFETY

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  1. LASER SAFETY Texas State University | San Marcos

  2. 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)

  3. 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

  4. 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)

  5. 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

  6. 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

  7. 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

  8. TxState Laser Safety Program • Laser Safety Training Manual • Laser Safety Manual • Texas Department of State Health Services Bureau Radiation Control • 25 TAC §289.301

  9. LASER • Acronym for: • Light • Amplification by the • Stimulated • Emission of • Radiation.

  10. Laser • Emits non-ionizing electromagnetic radiation that is ultraviolet, visible, or infrared light. • Lasers now capable of emission in X-ray frequency.

  11. 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.

  12. 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

  13. Continuous Wave Lasers • Operated in a continuous mode for at least a period of .25 seconds. • Output expressed as the average power (watts).

  14. 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

  15. 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).

  16. Radiant Exposure (Energy Density) • Normally expressed in Joules/cm2 • Function of: • Pulse Density • Pulse duration • Pulse frequency • > radiant exposure > potential hazard

  17. 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.

  18. 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

  19. 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

  20. 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.

  21. Class I • May produce visible or invisible laser radiation. • Do NOT pose a hazard under normal operating conditions.

  22. 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

  23. 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.

  24. 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.

  25. Class IIIb • Produce eye damage if viewed directly. • Includes intrabeam viewing of specular reflections. • Normally do not produce a hazardous diffuse reflection.

  26. 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.

  27. 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

  28. 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

  29. 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

  30. 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

  31. 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

  32. 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

  33. Biological Effects • Tissues at risk are: • Eyes • Skin • Three mechanisms of injury • Thermal effects • Photochemical effects • Acoustical transient effects

  34. 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

  35. 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

  36. Picture of burned retina.

  37. 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

  38. Laser Safety • Responsibility of each individual • Three categories of controls • Engineering • Administrative and Procedural • Personal Protective Equipment • Work better together than singly.

  39. 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

  40. Administrative & Procedural Controls • No physical barrier • Examples • Area postings • Standard Operating procedures • Maintenance procedures • Administrative procedures • Alignment procedures

  41. 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

  42. 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

  43. 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

  44. 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

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