| 摘要 |
To produce a tracking error signal (28) precisely indicating a positioning error of an optical beam with respect to one of recording tracks in a radial direction of an optical disk (12), a compensation section (31-36) compensates for a subtracted signal produced by subtraction between first and second electric output signals of first and second sensors (23 and 24) which receive first and second partial beams reflected from the optical disk by irradiating the optical disk by the optical beam. In the compensation section, an added signal is produced between the first and the second electric output signals. When the added signal is greater than a predetermined reference level, a comparator produces a compared result signal of a high level. Otherwise, the comparator produces the compared result signal of a low level. A sample-and-hold circuit passes the subtracted signal therethrough while the compared result signal has the high level. When the compared result signal turns from the high level to the low level, the circuit samples the subtracted signal into a sampled signal and holds the sampled signal while the compared result signal has the low level. The tracking error signal is produced by adding an inverted signal of the subtracted signal to a multiplied signal produced by multiplying output of the circuit by two.
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