Patrick Murphy, ILDA Executive Director

Scanning Audiences at Laser Shows: Theory and Practice ... and a Proposal
Patrick Murphy, ILDA Executive Director Greg Makhov, ILDA Safety Committee Chair

What is Audience Scanning?

“Creating beautiful mid-air beam patterns
which surround and envelop the audience, for entertainment and display purposes”

International Laser Display Association
3 important points Scans are not intended to enter the eye An undesired consequence “Audience scanning” means deliberate exposure only Does NOT include accidental exposures from non-audience scanning shows Visible, continuous-wave lasers only Never use pulsed lasers (ex: Q-switched) Only CW lasers discussed in this paper International Laser Display Association

How many people have been exposed?

Conservative estimate
Number of people exposed to direct laser beams: 100 clubs with 100 people nightly: 10,000/day 3,650,000 people experience this yearly 109,500,000 people over the past 30 years Number of exposures per show: Beam crosses the eye an average of 20 times per show Typical 5 pulses each crossing 100 pulses per show International Laser Display Association

109,500,000 people x 100 pulses per show =
10,950,000,000 pulses over 30 years

What laser power have these 110 million people been exposed to?

Typical raw laser power
500 milliwatts to 5 watts raw power (at laser, before projector optics and scanner) As much as 20 watts raw power for larger shows International Laser Display Association

What is the irradiance at the audience?
Exact irradiance unknown Estimates from laser show and safety experts Greg Makhov, John O’Hagan, James Stewart Most shows are above the MPE at the point of closest audience access Many shows are far above the MPE 10, 50, even 300 times the MPE International Laser Display Association

A typical show 3 watt laser After optics and scanners, about 1 watt output toward audience 1 milliradian divergence Closest audience access 25 meters International Laser Display Association

A typical show, cont. Static irradiance: 162 mW/cm2 65x the ¼ second MPE Well-designed scanning effects, no static beams Dwell time is 1 msec or less, so single pulse MPE applies Because of scanning, hazard is reduced 4x 16x the single pulse MPE International Laser Display Association

Where are the injuries from 11 billion pulses, most over the MPE?

“Close to zero” injuries

1996 study by independent research firm Presented at ILSC 1997 Looked worldwide Found 5 reported accidents over 20 years Article notes “there may be underreporting” If 9 out of 10 injuries are not reported, this is 25 injuries per decade (2.5 per year) "Is Deliberate Audience Scanning Unsafe?", Patrick Murphy, Pangolin Laser Systems Proceedings of the 1997 International Laser Safety Conference, Vol. 3, pp

Google Scholar 2007 article on injuries at a show caused by a pulsed YAG laser “To our knowledge, only one case of eye injury during a laser show has been reported previously.” “The lesions resolved within 3 months” Retinal Laser Injury During A Laser Show Shneck, Marina MD; Levy, Jaime MD; Klemperer, Itamar MD; Lifshitz, Tova MD Department of Ophthalmology, Soroka University Medical Center, Ben-Gurion University of the Negev Retinal Cases & Brief Reports: Volume 1(3) Summer 2007, pp

Google search No reports found of incidents of audience members at shows with CW lasers (Again, we are not including the July 2009 Tomorrowland incident at this time) Not even informal complaints on blogs or forums International Laser Display Association

Rockwell Laser Industries database of over 1600 incident cases Only two cases involving deliberate audience scanning with CW lasers: One case of “eye irritation” following a laser show, 1980 One case of retinal scotoma produced while watching a laser show (beam hit into eye), 1997 International Laser Display Association

Recent incidents July 2008, Aquamarine Festival, near Moscow 35+ persons injured by pulsed laser Due to rain forcing audience into a tent, the laser was irresponsibly and illegally aimed down into audience instead of up into the sky Wrong type of laser; pulsed lasers should never be used for audience scanning Because of illegal use, these injuries do not apply to statistics about continuous-wave lasers used for audience scanning International Laser Display Association

Recent incidents July 2009, Tomorrowland Festival, Belgium 2 persons (out of 90,000) had eye injuries Laser show irradiance was calculated to be close to or at MPE: 50 mW/cm² closest to audience (5x MPE), 10 mW/cm² at 20 meters into crowd (same as MPE) Many high-powered laser pointers in use in crowd Conclusion: Legal and safety authorities agreed injuries were due to crowd laser pointers International Laser Display Association

Summary Based on 1996 study finding 5 incidents over 20 years
2.5 reported injuries per decade Estimating 90% underreporting: 25 estimated injuries per decade, worldwide

How does this compare? Lasers U.S. amusement park rides 2.5 reported injuries per decade Due to underreporting, could be 25 injuries per decade Worldwide 72,000 reported injuries per decade 44 deaths Just one country International Laser Display Association

Important caveats Not saying there aren’t changes to retina It is unknown whether shows cause laboratory-detectable changes Further research would be very helpful Not saying the MPEs are wrong We believe in and support the MPE levels International Laser Display Association

Our conclusion We are saying that, after 30 years and 11 billion pulses, most over the MPE, there are practically no complaints, injury claims, proven injuries, lawsuits, etc. from audience members, from CW shows. If there were, these shows would not be occurring Clients were very skittish after press reports of July 2008 injuries caused by pulsed laser International Laser Display Association

Why are there essentially no reported injuries?

Reasons for essentially no injuries
MPEs have a built-in safety factor Does not explain shows which are well over 10 times the MPE International Laser Display Association

Lasers are relatively far from audience members Gives time for beam to diverge Audience is not always looking at the laser beams Audience rarely focuses vision directly on the laser projector output (scanners) Taking in entire scene International Laser Display Association

Multiple pulses are safer than previously thought Effect of multiple pulses not n-1/4 See papers presented earlier at ILSC 2009 International Laser Display Association

Pupil is smaller than 7 mm Laser shows are usually presented with stage lights, etc., so 5 mm is more realistic At 5 mm: 50% less light enters the eye Pulse width is decreased by 30% International Laser Display Association

0.25 second aversion response prevents serious damage from scanning failure Small likelihood of hitting a pupil Randomly positioned static beam has a 1/25,000 chance of being on a pupil International Laser Display Association

Avoidance response before beam crosses the eye Move head Look down or to the side Blink or close eyes View show while blocking beam emission point Put up a hand in front of the projector output Stay behind the head of the person in front of them International Laser Display Association

Audience is spread out Those closest to the laser receive the maximum exposure Those farther back have a lower exposure, due to: Increased divergence Increased linear velocity of the scanned beam International Laser Display Association

Is it possible to create shows which are below the MPE?

Before: Very hard to measure exposure
Requires a detector watching the entire show Only measures that one spot To calculate additional locations, requires re-running entire show Practically impossible to determine maximum exposure International Laser Display Association

Analyze scan characteristics...
Angular velocity of scanners From 10 radians/sec to 100 radians/sec Distance from projector to audience From 1 meter to 10,000 meters Angular velocity * distance = linear velocity From 10 meters/sec to 10,000,000 meters/sec Assume 1 mrad divergence (tight for a laser projector) Beam diameter/linear velocity = pulse duration From 2 milliseconds to 10 microseconds Within range of Thermal MPE for 10 sec to 18 μsec MPE for pulse is therefore 1.8 x t3/4 x 10-3 J/cm2 International Laser Display Association

Time compared to aversion response
... compare to MPEs ... Exposure time MPE Notes Time compared to aversion response 1.0 second 1.8 mW/cm2 Aversion response protects against this exposure 0.25 second 2.5 mW/cm2 Longest exposure needed to be considered 1x 0.01 second 5.6 mW/cm2 2.2 x 0.001 second 10 mW/cm2 Typical slow scanning speed 4 x 18 microseconds 27 mW/cm2 Typical fast scanning speed 10 x International Laser Display Association

... express scanning factor as a multiple of the static beam
Conclusion: Scanning the beam allows an increase of 4 times to 10 times the exposure, compared with a static beam. International Laser Display Association

Easy, safe measurement technique
Show measurement is vastly simplified: Put out a static beam Measure at point of closest audience access Adjust power and/or divergence so the irradiance is 10 mW/cm2 (this is the MPE for a 1 msec exposure) Requires a show with smooth, constantly moving scans Recommended to use scan-fail safeguard or similar velocity-monitoring circuit International Laser Display Association

Problem: MPE-level shows are not impressive

MPE shows are dim & fuzzy
Shows done at the MPE are Low power: Dim High divergence: Fat, fuzzy beams Require almost total darkness to be effective Similar to turning down the volume at a disco or rock concert, to background listening levels International Laser Display Association

No longer an impressive show
Forcing MPE-only shows would be unacceptable to many clients and laser show producers For 30 years, they’ve presented shows that are 10, 50, 100 times the MPE, with no injury reports Want shows to be visually impressive, not wimpy International Laser Display Association

Solution lies in risk analysis and management

Risks in everyday life People accept risk in their everyday life (driving to work) and in their leisure activities Playing sports Going hiking Riding bicycles These activities can and do cause injuries Cuts (leaving visible scars) Bruises Broken bones International Laser Display Association

Injuries and life Minor injuries (cuts, scrapes, bruises) are an unfortunate but inescapable consequence of leading an active, interesting life NOT saying it is OK to cause injuries Should minimize or eliminate if possible But people routinely choose to participate in activities which eventually will lead to a cut, scrape, bruise (or worse) International Laser Display Association

Risk acceptance People make individual risk/reward calculations, based on factors including... ... enjoyment of the activity ... chance of injury (bowling vs. tackle football) People manage their risk Having control over risk exposure International Laser Display Association

Risk management Goal is to manage and minimize the risk Tackle football: Wear helmets and padding Hiking: Carry first aid gear, GPS Bicycling: Wear helmet, use lights at night International Laser Display Association

Risk management Goal is NOT to eliminate or water-down the activity to bland nothingness Only allow touch football No hiking except on marked paths All bicycles to have outboard training wheels International Laser Display Association

Risks at discos, nightclubs and concerts
Loud sound systems. One evening too close to the speakers can cause permanent hearing damage Audiences like loud music (rightly or wrongly) Note that there is not a movement to turn down sound to OSHA-approved levels Widespread alcohol consumption Often to excess Smoking in many countries Illegal drugs at some concerts, raves International Laser Display Association

Risks at discos, nightclubs and concerts
Patrons can control risks Bring earplugs Stand farther from speakers Drink in moderation, or non-alcohol drinks Despite the risks – or maybe BECAUSE of some of the risks – these remain popular A disco with moderate, OSHA-approved sound levels, that serves only soft drinks, will have very few patrons International Laser Display Association

Putting it all together...

The good and bad of audience scanning
Audience scanning -- good Audience scanning - bad Excellent safety record, despite many shows exceeding MPE New technique for accurately setting show irradiance 4x the static MPE Very popular, especially in discos, nightclubs, rock concerts Too many shows exceeding the MPE by far too much Too many laser show producers setting light levels “by eye” No idea of the exposure levels MPE shows are dim, fuzzy Unacceptable in higher risk environments such as discos, nightclubs, concerts

Patron-managed risk at laser shows
Take conscious or subconscious avoidance actions before the beam crosses the eye Look away Blink Don’t look directly at the projector Hold up a hand Stay behind another person’s head Turn around Move away from the laser-scanned area International Laser Display Association

A practical proposal to increase audience scanning safety

Requirements for all audience scanning shows
CW lasers only Operator must measure static beam so as to know irradiance – no more guessing Well-designed, smooth scan patterns with no hot spots Effective scan-fail circuit Laser show operator continuously monitoring the show (or equivalent automated detection system) International Laser Display Association

Level 1 show Below MPE (similar to current regulations)
Laser power at point of closest audience access is below the MPE Set beam irradiance to 10 mW/cm2 This is the MPE for 1 millisecond pulses No signage or other warning needed International Laser Display Association

Level 2 Show “With greater power, comes greater responsibility”
Show is allowed to exceed the MPE by a factor of 10 Measure the static beam; set irradiance to 100 mW/cm2 When scanning, this is 10x the MPE for 1 millisecond pulses Signage and caution announcements required “Caution: Extra-bright laser lights in use. Avoid looking directly into beams” Similar to signs at amusement parks such as “Do not ride if you are pregnant or have heart problems.” International Laser Display Association

How does this improve safety?
All audience scanning shows must be measured. NO EXCEPTIONS. No audience scanning above 10x the MPE. This eliminates the very high powered shows at 50, 100, 300 times the MPE Audience at Level 2 shows have additional safety information “Avoid looking directly into laser beam” International Laser Display Association

Who will use these levels?
Level 1 shows will be for cautious clients Corporate shows, family-audience shows, major theme parks Level 2 shows will be used where patrons accept or even welcome some risks Discos, nightclubs, rock concerts International Laser Display Association

Use by private sector Guidelines used by venue owners, show producers in areas where laser laws or enforcement is weak. They decide whether shows they present are Level 1 or Level 2 Guidelines championed within the laser show industry (ILDA) International Laser Display Association

Regulatory enforcement
Regulators could informally permit Level 2 shows, if comfortable with professionalism, safety measures of laser show producer Similar to police enforcement of speed limits: no tickets until you are 10 mph over the 60 mph speed limit International Laser Display Association

Work in standards committees
Seek discussion, improvement and acceptance by standards bodies IEC , Guidance for laser displays and shows ANSI Z136.10, Safe Use of Lasers in Entertainment, Displays and Exhibitions International Laser Display Association

Conclusion Audience scanning with visible CW lasers appears to be causing essentially no claimed or proven injuries There are mechanisms which are reducing the exposure on the retina For improved safety, we want to eliminate shows which are significantly over the MPE In return, we ask for shows at a reasonable brightness level International Laser Display Association

Questions?

(Slides that follow are “leftovers” which may have been included in various versions previous to this one) International Laser Display Association

Belgian incident Tomorrowland dance festival in Boom, Belgium, July 25-26, 2009 90,000 attendees International Laser Display Association

Lasers at Tomorrowland
Multiple lasers used Mid-air beams, and audience scanning 2 outdoor areas, and 3 indoor tents International Laser Display Association

Eye injury report 2 people claimed eye injuries “Irreversible” central visibility to a young man Unspecified eye damage to a 21-year-old woman Complaint lodged with police against festival organizer Found to be caused by laser pointer in crowd Police, mayor, health officials, organizer agree Many witnesses to high-powered pointer use International Laser Display Association

Laser show did not cause the injury
Only 2 persons out of 90,000 claimed injury Compare with Moscow festival: 35+ claims Compare with Bulgarian disco: 12+ injury claims Company used “beam attenuation maps” Audience irradiance: 50 mW/cm² closest to audience, 10 mW/cm² 20 meters in crowd Show was continuously monitored Police, mayor allowing same festival in 2010 International Laser Display Association

Tomorrowland: Conclusion
Injuries were not caused by audience scanning International Laser Display Association

Patrick Murphy, ILDA Executive Director

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