NONCONTACT ABSOLUTE POSITION MEASUREMENT USING A COMPACT-DISK PLAYER OPTICAL PICK-UP

An optical pick-up from a compact disc player is used as an absolute position sensor. The output from the pick-up gives the optical reflectivity profile from an object on which the measurement is to be taken. The object's position is given from the correlation between a pre-sampled reference of the reflectivity profile and actual samples of the same profile. The method is demonstrated for position/angle measurement of a smooth hand-polished rotating aluminium disc.