A moulding apparatus for moulding a strap on to a group of battery plates including a mould block with moulds, each of which has an inlet weir and an outlet weir. In one embodiment, the present invention permits the production of multi-spectral, polarimetric, near-field microscopy systems that can achieve a spatial resolution of less than 100 nanometers. The head worn device senses movement of the user’s head and generates corresponding input signals.