| 摘要 |
PROBLEM TO BE SOLVED: To compensate a reading signal wave form even in a small-scaled circuit without using a tilt sensor by detecting an error signal from the group of reading samples and extracting a sample of a particular time before or after a detecting time thereby generating a skew detecting signal. SOLUTION: A reading sample group R is supplied to 10 vertically connected unit delay elements D1 to D10. The unit delay element D1 to D5 and the unit delay elements D6 to D10 respectively form first and second delaying means and composed of 5-stage unit delay elements having delay Lt/VL. Here Lt satisfies the expression (λis a reading beam wavelength and NA is an aperture of an objective lens) and VL satisfies a reading linear speed. Then, an error detecting circuit 70 supplies a difference with the nearest predicted value of the output values of the unit delay element D5 as an error signal G to multipliers 81 and 82. Here, the value is multiplied by the outputs of R and D10 and passed through a multiplier 83 and an averaging circuit 84 to output a skew detecting signal (e). Thus, even in the small-scaled circuit, the reading signal wave form is compensated.
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