Patent ID: 7457218

Claim:
A method of obtaining a reproduction signal with good quality from a data recording medium, comprising: generating two actual signals as first and second signals I 1 and I 2 from detection signals obtained from said data recording medium; calculating a coefficient k which has linear correlation with a tilt, based on said first and second signals I 1 and I 2 ; and reproducing a reproduction signal in which influence of said tilt is eliminated, by using said coefficient k and said first and second signals I 1 and I 2 , wherein said calculating comprises: calculating said coefficient k from the following equation (1) k = - ( ( σ 1 2 + σ 2 2 + 2 ⁢ σ 12 ) ⁢ ( ∑ i N ⁢ r i ⁢ q i ) - ( σ 1 2 - σ 2 2 ) ⁢ ( ∑ i N ⁢ q i 2 ) ) ( σ 1 2 + σ 2 2 ) ⁢ ( ∑ i N ⁢ ( r i 2 - q i 2 ) ) + 2 ⁢ σ 12 ⁡ ( ∑ i N ⁢ ( r i 2 + q i 2 ) ) ( 1 ) where an impulse response of said first signal I 1 is expressed by the following equation (2) ∑ i N ⁢ h 1 ⁢ i ( 2 ) (N is a natural number and i is a time in units of clocks), and an impulse response of said second signal I 2 is expressed by the following equation (3) ∑ i N ⁢ h 2 ⁢ i ( 3 ) (N is a natural number and i is time in units of clocks), an expected value of noise of said first signal I 1 is σ 1 , an expected value of noise of said second signal I 2 is σ 2 , and an expected value of correlation of the noises of said first and second signals I 1 and I2 is σ 12 , q i =h 1i +h 2i , and r i =h 1i −h 2i .