Laser shows win limited support for audience scanning

17 Jun 2002

One of the most persistent opponents of scanning laser beams across people's faces at light shows has changed his mind.

"Audience scanning can be acceptable," John O'Hagan of the UK's National Radiological Protection Board said at the last day of the International Laser Safety Conference in Orlando. Ironically the Food and Drug Administration stopped a demonstration of scanning at a workshop earlier in the day because it had not been given enough notice.

O'Hagan has resisted audience scanning in the UK and spoken against the practice at international conferences for many years.

He said that two developments had helped him modify his view.

First, laser show promoters from around the world agreed on maximum exposures when they met at last year's International Laser Display Association conference in The Netherlands,. Some UK promoters still do not accept the figures but they are in a minority internationally, says O'Hagan.

Second, scanning techniques and technology are both developing rapidly.

One of the big problems of audience scanning is measuring how much energy a moving beam of visible light delivers to the retina. It is no good placing a power meter where the audience will stand because a beam projecting a complex three-dimensional pattern may miss it.

The agreement on the meaning of permitted exposure as given in the international laser safety standard makes it possible to measure a static beam, show that it is safe and then allow it to scan an audience.

Many laser show companies work internationally but attitudes towards scanning audiences varies from country to country. It is not allowed in the US while Germany allows scanning if the show is proven safe by an independent test house. The UK allows it in some circumstances but the promoter must prove there is no hazard so therefore it is effectively disallowed. Many other countries have no regulations or take no action.