the introduced optical design. The sensor optics surface profile
was implemented using a 5-axis CNC tool. The material was
mould aluminium, which contains small amounts of several constituents
such as silicon and magnesium. The tooled surface was
hand-polished in order to generate a high surface reflectance. The
reflectivity of the polished aluminium surface at 8–14m was
estimated to be around 0.98. The designed sensor pre-amplifier
electronics schematics are shown in Fig. 8