Patent ID: 6043483
Filing Date: 2000-03-28
Classification: G01D

Abstract:
An apparatus for determining the absolute position of a movable member with respect to a predetermined location, comprising:a first member and a plurality of second members, disposed on the movable member, the first member having a characteristic different from a characteristic of all of the second members;a detecting device, adapted to detect when the first member is at the predetermined location and when any of the second members is at the predetermined location, comprising a first detector, disposed at a first location of the detecting device, and a second detector disposed at a second location of the detector device, which is at a distance from the first location along a direction of movement of the movable member, the first detector being adapted to detect the first member and any of the second members when the movable member moves, and to output a first signal indicative thereof, and the second detector being adapted to detect the first member and any of the second members when the movable member moves, and to output a second signal indicative thereof; anda position and direction determiner, adapted to determine, based on the first and second signals provided by the first and second detectors, respectively, a direction of movement of the movable member, and a distance in which the movable member has moved relative to the predetermined location after the first member was detected by the detecting device as being at the predetermined location, to determine the absolute position of the movable member with respect to the predetermined location.