Importance

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Abstract

With an optical disc device for reproducing information from discs having a recording density different from one another, by means of laser light beams each having a wavelength different from one another, a provision is put in place to prevent data stored on a CD-R disc from being damaged by irradiating a short wavelength laser beam. A method for identifying discs disclosed by the present invention is to find out whether or not a disc in question is CD-R and the like by irradiating long wavelength laser light on the disc while the rotation of the disc is suspended, and otherwise to find out whether or not a disc is DVD and the like by irradiating short wavelength laser light on the disc. Shifting a focusing lens in the light irradiating axis direction of laser light by means of an actuator generates a focus error signal and an all light amount sum signal, the amplitudes of which enable the identification of discs.

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First Claim