Equinox Systems Cirrus User Manual page 10

Equinox Cirrus Safety
Maximum Permissible Exposure (MPE)
The amount of laser light that a person can be exposed to without it causing harm to eyesight is known
as the Maximum Permissible Exposure (MPE) or Exposure Limit Value (ELV). These levels are defined
the in the British Laser Safety Standard BS/EN 60826-1:2007, and more recently in the Laser H&S
regulations. When people are exposed to laser light which is above the MPE, it poses a risk of causing
eye damage. This could be of concern when the laser effects are viewed directly in the face or there is a
chance that they could be.
How do I know what the MPE is?
Knowing what the MPE and exposure level is for a given laser effect is quite a complex and
involved process to establish. For it is dependant on a whole number of conditions and variables that
need to be taken into account. The laser safety standard BS/EN 60825-1:2007 contains the data
required to calculate the safe levels, but it is not straightforward to interpret. Laser Safety Calculation
Software has been developed to help ease the task of establishing laser effects exposure.
Laser Safety Officer
The PD IEC/TR 60825-14:2004 Laser Safety Guidance recommends that all establishments that use,
or businesses that work with Class 3B laser products, should appoint a Laser Safety Officer (LSO). The
Laser Safety Officer should be aware of the safety issues when using lasers, and is responsible for
overseeing how the laser is used. In smaller businesses, the LSO will probably also be the installer,
operator, owner etc.
Diffraction vs Direct X-Y Scanning Lasers
Diffraction type lasers have become increasingly popular in recent years creating laser effects that split
the beam into hundreds, if not thousands of less powerful beamlets. This type of effect is usually much
safer to view directly than traditional scanned beam effects, for the simple reason that as the beam is
split into smaller beams, the power in each beam is reduced. With x-y scanning systems, even though it
may look as if the power is being reduced by the movement, the moment any beam crosses a person's
face, the full power of the beam may briefly enter someone's eye. Caution should still be used with
diffraction effects, in particular ensuring that the brighter central beams are kept above head height.
Separation Distances
Health and Safety guidance states that for supervised installations laser light above the Maximum
Permissible Exposure (MPE) should not be accessible to members of the audience. It also recommends
the area where the MPE may not be exceeded, extends from 3m above, and 2.5m laterally from any
location in the venue where members of the public may gain access during the display. The following
diagrams illustrate this.