| CPC G01D 5/2455 (2013.01) [G01D 5/2451 (2013.01); G01D 5/2492 (2013.01); G01D 5/2497 (2013.01)] | 6 Claims |
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1. A position detection apparatus comprising:
an absolute track in which a first binary sequence generated from a second binary sequence is recorded; and
an absolute sensor unit that reads the first binary sequence from said absolute track,
wherein the first binary sequence consists of 0s and 1s and is generated by replacing 0 in the second binary sequence with 10 and 1 in the second binary sequence with 01, or by replacing 0 in the second binary sequence with 01 and 1 in the second binary sequence with 10,
wherein when reading, values in the second binary sequence are replaced with 1s and 0s in accordance with not a positive/negative of magnetism but a direction of inversion from positive to negative or from negative to positive, and
wherein said absolute sensor unit includes two sensor elements arranged at an interval of λ/2 or less than λ/2 of a recording pitch λ of the first binary sequence,
the apparatus further comprising:
an incremental track communicating with an incremental sensor unit that detects fore and rear positions of the absolute sensor unit;
an inverter that generates an inverted sequence by bit-inverting a detected sequence detected by said absolute sensor unit;
a discriminator that discriminates, based on the fore and rear positions detected by the incremental sensor unit, which one of the detected sequence and the inverted sequence should be searched for;
a searcher that searches the second binary sequence for the detected sequence or the inverted sequence discriminated by the discriminator; and
a position detector that detects a position of said absolute sensor unit based on a position of the detected sequence or the inverted sequence found by said searcher in the second binary sequence and the fore and rear positions detected by the incremental sensor unit.
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