Poor mirror drive

The effect of a drive mechanism that does not allow the plane of the moving mirror of the interferometer to maintain its angle relative to the plane of the beamsplitter is somewhat analogous to the effect of beam divergence discussed in Section 2.6. In the case of the poor mirror drive, however, an optical path difference is generated between the two extreme rays of the beam passing through the interferometer rather than a path difference between the extreme rays and the central ray. 

While familiarisation with the area to be visited is important, an essential part of the risk assessment procedure, that is often overlooked, is familiarisation with the mode of transport to be used. If this is a self-drive minibus, prior to the journey, a check should be carried out on basic safety features such as tyres, lights, windscreen washers/wipers, brakes, availability of first aid kit and fire extinguisher, fluid levels, doors (operate freely and close securely) and warning instruments. Driver effectiveness and fatigue is also influenced by poor driving position and conditions so, before setting off the driver should adjust the seat, the mirrors and check that they can reach all the essential controls. 

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