According to the IEC Standard 60825-4, Safety of laser products — Part 4: Laser guards [1], laser guard is defined as a barrier which limits the extent of a danger zone by preventing laser radiation accessible at its rear surface from exceeding the class 1 AEL. Conventional materials used for laser guards are metals such as aluminum or steel, or plywood. Test conditions and test classification for proprietary laser guards are given in the Annex D of the above standard.
With the recent advancement of diode-pumped solid-state laser technology, the output power from single laser equipment, especially from a fiber laser, now can reach more than 100 kW. Conventional carbon oxide lasers are now being replaced with fiber lasers due to many attractive features such as beam quality, low power consumption and easy direct fiber beam delivery. The operating wavelength of typical industrial fiber laser is in 1 µm band. This wavelength band is more hazardous to the eye compared to the 10 µm wavelength band of CO2 lasers. The large impact to the human body would be a serious concern if protection time of a laser guard for fiber laser were not sufficiently long for suitable access control measures.
To our knowledge, none of the conventional laser guard materials meet the criterion of T2 (maintenance inspection time of 100 s) for continuous irradiation of 5 kW laser with 30 mm beam diameter.
In this report we propose a new laser guard material utilizing Carbon Fiber Reinforced Plastics (CFRP), which will satisfy the safety requirement for IEC test classification T3 up to output power of 10 kW for 30mm beam diameter and T2 up to output power of 5kW for slightly larger beam diameter. We also propose an improved evaluation method suitable for the newly developed laser guard material by considering statistical analysis. We will also report the detail of the test methods including measurement setup towards proposal of future revision of the international standard for laser guards.