| 摘要 |
PURPOSE:To attain a highly precise resoluting reproduction without crosstalk for a recording medium recorded in high density by simultaneously reading a track to be read and the neighboring one by >=2 laser beam different in wavelength. CONSTITUTION:Laser beams whose oscillation wavelength is different by several 10nms generated by an integrated 3-wavelength distributing feedback type laser oscillator 10 are condensed on the surface of a recording medium 15. The middle beam 19b irradiates a track to be read, and beams 19a and 19c irradiate the neighboring ones. Reflected laser beams are transmitted to a diffraction grating 16 and separated into one of three different wavelengths, and transformed into electrical signals. In case the track to be read has an identification signal f3, the output signals from band-pass-filters BPF 36 and 38 represent the amount of crosstalk. Feedback is adjusted by changing the coefficients K1 and K2 of a multiplicator 34 in order to make the f1 and f2 zero at the output terminal 39. As a result, a reproduced signal without any crosstalk component is attained.
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