timstephens

Diffuser Protection

Visisize is Oxford Lasers particle sizing product. I designed an EN60825 compliant enclosure for the output diffuser. The flagship N60 series systems contain an Nd:YAG laser to illuminate the particles, which is delivered to the measurement head through a liquid light guide and then diffused with a special diffuser element. The light guide is a potential place where the user could be inadvertently exposed to a class 4 laser beam. The laser safety standards state that if the laser beam for a class 4 laser is inaccessible, you can reduce the hazard classification. Since the diffuser element reduces the hazard classification, we realised that if we could deliver the laser to the diffuser in a protected way, we would be able to reduce the classification of the whole system.

The diffuser system is constructed from a screw-together lens tube system that allows the configuration to be adjusted to suit the experiment. Unfortunately, the screw in tubes mean that the laser beam is easily accessible. I designed and modelled a special diffuser enclosure that prevents access to the laser beam without the use of tools, and adds an emergency stop button, an emission warning light and an air-purge to keep the output lenses clear of moisture.

The light guide is bonded into special collars that mount into the screw-in tubes at one end and into the light guide launch on the vs trolley at the other end. Because the diameter of the collar at the output end will not slip through the tubes it’s impossible for the light guide to be removed from the collar. The whole screw together assembly is fitted within a solid, protective outer enclosure that can be pressurised with compressed air to help with purging air over the output optics. The back of the diffuser enclosure contains electronics for an emergency stop button and an emission indicator to comply with en60825 (since the light guide is 5m long and therefore far away from the laser’s own emission indicators) I am particularly proud of the fact that the whole assembly can be manufactured with standard tube stock, and is easy to manufacture and assemble whilst offering complete laser protection within a sleek-looking package.