Patent ID: 7129699

Claim:
A phase detection system comprising: a first rotating member; a second rotating member that is rotationally coupled to the first rotating member such that the first and second rotating members rotate at substantially the same rate; a first disk attached to the first rotating member such that the first disk rotates with the first rotating member, the first disk having a binary pseudo-random sequence encoded sequentially about a periphery of the first disk; a second disk attached to the second rotating member such that the second disk rotates with the second rotating member, the second disk having the binary pseudo-random sequence encoded sequentially about a periphery of the second disk; a first sensor disposed at a first location near the periphery of the first disk, the first sensor operable to periodically detect the binary pseudo-random sequence at the first location as the first disk rotates and generating a first detected sequence from the detected binary pseudo-random sequence; a second sensor disposed at a second location near the periphery of the second disk, the second sensor operable to periodically detect the binary pseudo-random sequence at the second location as the second disk rotates and generating a second detected sequence from the detected binary pseudo-random sequence; and a data processing system that receives the first and second detected sequences and cross-correlates the first detected sequence with the second detected sequence to determine the rotational phase relationship between the first rotating member and the second rotating member.