Optical beam rider

A new type of optical-beam-riding system is described in which the vehicle position is derived by scanning a spatial modulation pattern. The optical beam is produced by a transmitter which incorporates a conventional filament lamp as source and a motor-driven nutating lens or equivalent mechanism as scanner. Misalignment signals are obtained in vehicle axes, an important advantage if the vehicle is not roll-stabilised. In addition, these signals are, to a first approximation, independent of the distance from the transmitter out to maximum design range. Sources of error include transmitter noise due to imperfections of the scanning mechanism and receiver noise generated by photodetectors and amplifiers. In addition, there is some signal loss at extremes of range due to defocusing, because the equipment uses fixed-focus optics.