Patent ID: 7477586
Filing Date: 2009-01-13
Classification: G11B

Abstract:
1. An optical disk apparatus in which a first, second, third, and fourth optical disks are selectively installed, the first and second optical disks having different recording film characteristics from each other and both having a single-layer recording layer, the third and fourth optical disks having different recording film characteristics from each other and both having a double-layer recording layer, the optical disk apparatus recording and reproducing information on and from the optical disk installed, the optical disk apparatus comprising: an optical head which irradiates the optical disk installed with a light beam to provide a reproduction signal corresponding to reflected light; a determining section which uses the optical head to reproduce information from an innermost peripheral portion of the optical disk installed to determine which of the first to fourth optical disks has been installed, on the basis of the level of a reproduction signal obtained; a reproduction signal processing section which processes the reproduction signal provided by the optical head to extract information from the reproduction signal; a control section which controls the reproduction signal processing section on the basis of the result of the determination by the determining section; a section which determines that the optical disk installed is the first optical disk if a rate at which a reproduction signal at a level above a first reference value is obtained from the innermost peripheral portion is higher than a rate at which a reproduction signal at a level below the first reference value is obtained from the innermost peripheral portion; a section which determines that one of the second to fourth disk from which a reproduction signal level higher than the first reference value is obtained is the second optical disk; and a section which determines that one of the third and fourth optical disks for which all of the reproduction signals obtained are at a signal level substantially above a second reference value smaller than the first reference value is the third optical disk.