In research settings, serious laser accidents are known to occur during laser alignment. Appropriate steps must be taken to minimize the risk to beam injuries occurring during alignment procedures. Class 3B lasers should and Class 4 lasers shall have corresponding alignment procedures written and maintained with the laser for reference.
Alignments should be done only by those who have received laser safety training. It is best to perform alignments with another trained person. Review all procedures before attempting the alignment. Make sure that all warning signs, lights and locks are operating.
At alignment conclusion, normal laser hazard controls shall be restored. Controls set back in place include replacing all enclosures, covers, beam blocks, barriers and checking affected interlocks for proper operation.
Alignment Procedures for Class 3B and Class 4 Lasers
- Exclude unnecessary personnel from the laser area during alignment.
- Housekeeping is paramount. The work area and optical table should be free of objects or surfaces that could reflect the light. Remove any jewelry, watches, rings (or cover rings with tape), remove objects in shirt pockets, and remove id badges. Make sure any reflective surfaces in the area are blocked or covered. Remove any unnecessary equipment, tools and combustible materials.
- Whenever possible, use low-power visible lasers for path simulation of higher-power visible or invisible lasers.
- Enclose the beam as much as possible.
- Wear protective eyewear and clothing to the extent practicable. Use special alignment eyewear when circumstances (e.g. wavelength, power, etc.) permit their use. Alternate means of viewing the beam such as CCD and web cameras should be considered before allowing the use of alignment eyewear.
- When aligning invisible (and in some cases visible) laser beams, use beam display devices such as image converter viewers or phosphor cards to locate beams.
- Perform alignment tasks that use high-power lasers, at the lowest possible power level. Pulsed lasers are aligned with single pulses if possible. If the laser is Q-switched, turn off the Q-switch and use low power or CW.
- Use a shutter or beam block to block high-power beams at their source except when actually needed during the alignment process.
- Use a laser-rated beam block to terminate high-power beams down range of the optics being aligned.
- Use beam blocks and/or laser protective barriers in conditions where alignment beams could stray into areas with uninvolved personnel.
- Place beam blocks behind optics (e.g., turning mirrors) to terminate beams that might miss mirrors during alignment.
- Locate and block all stray reflections before proceeding to the next optical component or section.
- Be sure all beams and reflections are properly terminated before high-power operation.
- Whoever moves or places an optical component on an optical table (or in a beam path) is responsible for identifying and terminating each and every stray beam coming from that component (meaning reflections, diffuse or specular).
- There shall be no intentional intrabeam viewing with the eye.
- Post appropriate area warning signs during alignment procedures where lasers are normally Class 1 (enclosed).
Procedures derived from: ANSI Z136.1, EHS University of Washington, SLAC.