Controlling the Beam
It falls upon the shoulders of the laser safety officer (LSO) to assess the environment in which the laser is operating. This assessment may lead to requiring the use of laser safety curtains or laser safety barriers to prevent the laser beam from escaping the area through an entryway. Laser safety curtains are tools available to the LSO for entryway control. They are flexible and can be cut to any dimension. Curtains are hung like drapes from track systems or are attached to or suspended from a ceiling, but may also be configured as a floor-mounted system with vertical uprights carrying the load. Sometimes curtains are referred to as “barriers” because the material is opaque. Laser safety curtains per the ANSI Z136.1 “shall be specifically selected to withstand direct and diffusely scattered beams.” Therefore, curtains should not combust or ignite or release toxic fumes when struck by a laser beam. In addition, the ANSI Z136.1 for Safe Use of Lasers requires that a damage threshold limit (TL) and the exposure time for that threshold limit is exhibited on the curtain.
While curtains can provide a range of protection, they may not be able to withstand very high irradiance levels for more than a few seconds. A stronger form of protection is needed. This is when laser safety barriers may have to be used. Laser barriers are opaque and are also called partitions, guards or screens. They are freestanding laser-blocking devices usually made of a light metal. They can withstand higher irradiances than curtains, but like curtains must have the threshold limit and exposure time marked on the barrier. Many systems provide rollers or casters attached to the support legs. Some systems also provide a method or accessories for attaching multiple barriers together with no safety gaps. They are used to block or attenuate reflected or direct beams in entryways and are used during times of service. They can also be used to establish a boundary for a laser-controlled area. Per the ANSI Z136.1 for Safe Use of Lasers standard laser barriers “shall be specifically selected to withstand direct and diffusely scattered beams.”
Curtains and barriers are very useful tools for laser beam control. They serve as a good entryway control and in laser beam containment when lasers are being serviced.