Intelligent Protective Clothing for High-Output Lasers
In an EU project under the leadership of the Laser Zentrum Hannover e.V. (LZH), passive and active protective systems for jackets, trousers, aprons and gloves are being developed. This clothing offers effective protection against laser radiation with output densities of up to 20 Megawatts per square meter.
Protective professional clothing for firefighters, for welders or for chemists is readily available on the market. Despite the wide use of lasers in industry and research, there is currently no suitable protective clothing for the user, and when it comes to hazards from intensive laser radiation, only suitable protective laser eyewear has been classified and certified.
It is also important to have safety clothing to protect the skin, especially for the increasing number of cutting and welding applications with hand-guided laser systems. Operators are often in the directly next to the interaction zone between the laser beam and the materials to be processed, and often high-power lasers are in use. Under unfavorable conditions, for example when highly reflective surfaces are being processsed, the laser beam may be quickly deflected towards the user, causing severe skin burns. Also, near infrared laser radiation may penetrate into deeper tissue, and damage blood vessels and other biological tissue.
Therefore, the laser protective clothing developed within the framework of the EU "PROSYS" project is pursuing two strategies. First, researchers have designed a passive system with multi-layer technical textiles. The top layer has a special coating which diffusely reflects the laser radiation as much as possible. Radiation which may penetrate this first layer is then evenly spread out by the middle layer. Any residual heat, at least for a limited amount of time, which enters the energy barrier of the inner layer, may trigger a pain sensation. "This is intentional. Users should notice that they are being exposed to hazardous radiation, so they have the chance to withdraw their hand or arm," explains Michael Hustedt, Head of the Safety Group at the LZH, and coordinator of the PROSYS project. Normal reaction time is up to 4 seconds, and the passive system can protect users for output densities up to 900 kW/m2, making this protective clothing 20 times more effective than what is presently available on the market.
The effectivity of the protective clothing can be even further improved by integrating an active system, which uses sensors embedded in the different layers. If the sensors are damaged by radiation, they send an electrical signal to the laser in less than 100 ms, and the laser is automatically shut off. The operators' movement is not impaired, since the active system uses a wireless communication system between the safety transmitter and the receiver for the laser. Since the complete shut-down of the laser may take approximately 80 milliseconds, a combination of the active sensors and the passive protection layers makes sense. This system offers protection against output densities of up to 20 MW/m2.
The international consortium, which is composed of three research institutes, nine SMEs and one large enterprise, has developed prototypes of the protective clothing, which have been presented at different industrial fairs this year (e.g. Hannover Messe, LASER World of Photonics). Plans are being made for launching the products on the market soon.
Further developmental work will be, above all, concerned with improving the active systems, making them even more robust and flexible, without losing their protective functions. Practical tests in an industrial setting should provide further information for improving ergonomics and wearing comfort of the protective clothing, in order to achieve high user acceptance. The focus of this work is, for example, on reducing the weight of the material and improving the haptic characteristics of the gloves.
Source: Laser Zentrum Hannover (LZH)