Patent attributes
A position detector for detecting the position of a helicopter blade includes a sensor to generate a signal in dependence on the position of a helicopter blade with respect to the sensor, and a data processing module arranged to receive the signal from the sensor and generate an output indicative of the blade position from the received signal. The sensor includes a mask having a plurality of slits, a lens assembly, and light detector. The lens assembly has a field of view and directs incident light onto a focal plane of the lens assembly. The light detector detects the level of illumination passing through each of the slits in the mask and provides a signal indicative of the illumination level to the data processing module. The mask is located at the focal plane of the lens assembly and the slits formed in the mask are angularly divergent from one another.
