A method and apparatus for measuring the height of a blade of a turbine rotor as the rotor is being rotated characterized by deflecting a laser beam at a given deflection frequency across the path of the moving blade so that a portion of the deflected beam will be reflected by the end of the blade, sensing...http://www.google.co.uk/patents/US4053227?utm_source=gb-gplus-sharePatent US4053227 - Method and apparatus for automatic and contactless measurement of the height of moving blades of a turbine
