Patent ID: 8307264

Claim:
A detection apparatus configured to detect a position of an object to be detected based on two signals, the two signals being respectively approximated by a cosine function and a sine function, the apparatus comprising: an arithmetic portion configured to reduce an error of each of the two signals based on an error prediction value to output two error correction signals; a phase arithmetic portion configured to calculate a phase which represents the position of the object to be detected based on the two error correction signals; a storage portion configured to store sampled data of the two error correction signals sampled with respect to each of a plurality of sampling phases based on the two error correction signals and the calculated phase; and a Fourier transform portion configured to obtain coefficients α k , β k , γ k , and δ k of each term in two expressions representing the two error correction signals by performing a Fourier transform on the sampled data, the two expressions being represented as follows: A*=α 0 +α 1 cos θ+β 1 sin θ+ . . . +α k cos kθ+β k sin kθ B*=γ 0 +γ 1 cos θ+δ 1 sin θ+ . . . +γ k cos kθ+δ k sin kθ, where A* and B* are the sampled data of the two error correction signals, θ is a phase of the sampled data of the two error correction signals, and k is not less than 2, wherein the error prediction value used by the arithmetic portion is updated iteratively using the obtained coefficients.