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Product Code: ILSC2009_1305

Scanning Audiences at Laser Shows: Theory and Practice
Patrick Murphy, International Laser Display Assn.; Orlando FL USA
Greg Makhov, Lighting Systems Design Inc.; Orlando FL USA
Presented at ILSC 2009

For more than three decades, the technique of "audience scanning" has been routinely used at laser light shows outside of the United States. Visible beams from CW lasers are projected towards viewers, to put them inside cones, fans and other moving light shapes set to music. Most commonly, accessible irradiance levels have not been measured by operators; instead they have been set by eye to look "OK". Since MPE-level irradiance at the audience is somewhat less bright than desired, most shows have exceeded the MPE.
Estimates of the irradiance levels range from 10 times to 100 times the MPE, or more. Despite this, there have been remarkably few proven or even claimed reports of injuries from deliberate audience scanning, given this widespread practice. A number of possible reasons are presented, including high divergence lasers, short duration of exposure, and viewers who actively take action to reduce exposure. Finally, a compromise proposal is presented for regulators and venue operators, in order to allow audience scanning at measured, reasonable irradiance levels, in return for banning truly unsafe or unknown levels.

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