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World: Summary of papers presented at International Laser Safety Conference 2013
22 Mar 2013 -- Categories: Bans & Restrictions | Easy availability | Statistics | SLA news
Every two years, world experts in laser safety gather at the International Laser Safety Conference. Below is an overview of 15 laser pointer, laser show and laser/aviation safety papers presented at the 2013 ILSC meeting in Orlando. The papers are available in the 2013 ILSC Proceedings, a 390-page book available from the Laser Institute of America. All page references below are to the Proceedings book.
For additional ILSC 2013 papers, click the “read more” link.
Laser pointer hazards for pilots
- A study of the actual output of 40 laser pointers, with powers up to 1.5 Watts, showed significant differences between measured and calculated hazard levels. In some cases, the actual hazard measured at some spots inside the beam was three times the estimated hazard. This is due to the laser output not being smooth in all cases, but instead the beams having “hot spots”. The study also showed that windscreens reduced the beam irradiance -- which is safer for pilots -- from 5% to 60%. (Note however that the McLin study described below showed that windscreens also spread the beam and thus increase glare.)
- A discussion of how being inside the Nominal Ocular Hazard Distance of a laser beam does NOT mean instant blindness for pilots and others.For example, consider a 1 Watt, 1 milliradian laser where the recommended safety distance (NOHD) is 733 feet. If possible, you should be at least 733 feet from the laser before exposing an eye to the direct beam. What is the actual hazard? At 232 feet from this laser, there is a 50/50 chance of the beam causing a barely observable retinal lesion under laboratory conditions where the laser and eye are fixed in place. Due to motion of the aircraft and hand-holding the laser, the chance of a retinal lesion is likely to be less. The distance from 232 feet (“ED50”) out to the NOHD at 733 feet is a known “safety factor” where the chance of retinal injury decreases even further. At the NOHD there is a “vanishingly small risk of hazardous exposure” (Sliney, 2013). Police and other first responder pilots can use this information to better weigh the risk of laser exposure to laser light vs. the benefits of completing a mission (rescuing a person, apprehending criminals, etc.). This presentation also discusses ways to make flight near lasers safer for pilots. A PDF file of all the slides presented is here.
For additional ILSC 2013 papers, click the “read more” link.
iPhone laser event recorder app
- In one of the most interesting ILSC papers, a researcher has developed an iPhone app that records laser and bright light events. The Laser Event Recorder app uses the phone camera to take from 7 to 10 frames per second. “LERapp” analyzes the frames and if it sees an over saturated area, saves the image plus information such as the GPS location, heading, date, time, laser color and estimated irradiance. It can work both in daytime and nighttime. It is not commercially available, but the goal is to have this in the Apple App Store as well as making it available for other smartphones and for Electronic Flight Bag tablets used by pilots. Link to LaserPointerSafety.com detailed story is here.
Illegal and overpowered laser pointers
- Most laser pointers purchased online in Australia violated the country’s import and possession laws. The various 2008 bans on lasers may have actually made the situation less safe, since imported lasers claim to be at safe, legal levels but can be substantially more powerful and thus more hazardous. Link to LaserPointerSafety.com detailed story is here.
- The U.K. HPA laser safety agency analyzed samples of lasers and pointers seized from one company. HPA found that 80% of the lasers were Class 3B or 4 (above 5 mW) and thus presented a risk to users. This is a fascinating paper with many details such as the volume of lasers, problems with labeling and batteries. For example, “it was estimated that the trader sold more than 35,000 laser pointers over a two year period generating income of over £1,000,000 (approximately US$1,600,000).” The violator received a suspended 180-day jail term and 300 hours of community service. Link to LaserPointerSafety.com detailed story is here.
- U.S. government researchers tested 122 laser pointers. NIST found that 90% of green ones and 44% of red ones were overpowered. A $2000 laser pointer meter was also described which can be used for accurate measurements of laser power. This received widespread coverage in US-based press. Link to LaserPointerSafety.com detailed story is here.
- The U.S. FDA laser safety agency analyzed DPSS green laser pointers (the main type sold as of 2013). FDA found many pointers were overpowered (brighter than their stated Class level) and/or emitted hazardous invisible infrared radiation.
Laser light shows
- Michael Higlett of the U.K. Health Protection Agency discussed a laser show exposure measuring device he developed. It has two sensors corresponding to two eyes. It is placed in the audience area where the highest exposures are anticipated. The sensors send data to a laptop via long-range Bluetooth. If a pre-set limit such as the MPE is exceeded, this is highlighted on the laptop. As a test, a Pangolin graphic (not beam) show was scanned onto the sensors. There were 17 beam passes with 153 pulses during the passes; 140 of these exceeded the set hazard level. The maximum level recorded was 22 times the safe level. Had this been a real audience scanning show, there would need to be changes in laser power, divergence and/or location.
- A presentation was scheduled about laser shows in live concerts. The presenter was not able to attend. An abstract indicated that his presentation would have discussed the risks of using lasers in challenging environments, around workers who are often unaware of the hazards. A study was carried out to observe common issues, and to identify best practices to create safer working environments.
Dazzle and glare hazards
- Glare caused by lasers was extensively studied. One finding was that there are large differences between various people. “This implies that the specification of precise thresholds [of glare] and the respective extend of temporary blinding is not an easy task.”
- Laser dazzle can be calculated by computer (rather than just measured or estimated from instruments). This may help with studies of dazzle’s effect on pilot performance.
- An extensive study of the effect on glare of observers, various angles to the laser, and the use of a windscreen. Dazzle was more severe in darker conditions, and looking through a windscreen also increased dazzle.
Laser safety concepts and standards
- A discussion of how a key laser safety concept, the Nominal Ocular Hazard Distance, was developed. This is of interest because the NOHD is sometimes misinterpreted by the general public as meaning that being exposed to laser light closer than the NOHD could result in instant blindness, and conversely, that the laser light is perfectly safe once past the NOHD.
- A discussion of safety standards concludes “…safety is not completely achievable by product standards…. Legislation and enforcement can to an extent control sales and distribution, but does not appear to be effective because of the ways in which these [laser] products are distributed -- direct sales to individuals. Safety involves not only standards and their writers but also manufacturers, distributors, employers, legislators, police, and finally the users.”
Risk analysis, and comparative risks
- An analysis of how to determine risks of laser exposure. A highlight is a discussion of what level of risk is considered acceptable by society. For example, in the U.S., death is generally accepted at a level of 1 incident per million persons per year, while permanent injury such as vision loss in one eye is accepted at a level of 1 incident per 100,000 persons per year. (These are very broad statements; please see the paper and resources for important details.)