| 摘要 |
An optical position detector for detecting the position of a moving object, in particular a helicopter rotor blade or propeller. The detector comprises one or more sensors mounted onto a helicopter airframe (SN1, SN2, SN3, Fig. 1) arranged to view a part of a helicopter blade as it passes through each sensor field of view (V1, V2, V3, Fig. 1). The sensor comprises a planar opaque mask M1 having a plurality of thin slits S1-Sm formed therein which are angularly divergent from one another. A lens assembly RXL having a field of view is arranged to direct incident light onto the mask M1 placed at the focal plane of the lens assembly. A number of lenses L1-Ln collect the light passing through the slits and focus it onto fibre optic light guides F1-Fp, which transmit the light to a number of detectors in a control module. Alternatively a CCD array may be employed (PD, Fig.3). Thus the amplitude of illumination passing through each of the slits as the rotor blade passes over the field of view of the lens assembly is detected. |
