Multi-layered optical disk and optical disk device

An optical disk device for performing recording or reproduction of information with respect to a multi-layered optical disk,

• the multi-layered optical disk including
• a control-information recording layer and
• an other recording layer,
• the control-information recording layer recording therein control information which is reproducible in a state where only a focusing servo operation is operated during rotation of the multi-layered optical disk,
• the multi-layered optical disk being so configured as to not include the other recording layer in a radius area where the control information is recorded,
• said optical disk device, comprising:
• a laser light light-source for emitting a laser light;
• an objective lens for converging the laser light to irradiate the multi-layered optical disk with the converged laser light;
• an optical detection unit, which includes the objective lens, for optically reading the information recorded in the multi-layered optical disk;
• a first signal generation unit for generating a focus error signal using outputs from the optical detection unit;
• a second signal generation unit for generating a sum-total signal of the outputs from the optical detection unit;
• a third signal generation unit for generating a digital signal using the sum-total signal, the digital signal indicating that a focal-point-achieved position of the laser light is in proximity to the recording layer of the multi-layered optical disk;
• a band limitation unit for generating a signal resulting from imposing a band limitation on the focus error signal;
• a displacement unit for displacing the optical detection unit in a radial direction of the multi-layered optical disk;
• a rotation unit for rotatably driving an optical disk installed into said optical disk device;
• and
• a judgment unit for using the outputs from the optical detection unit, and thereby judging a type of the optical disk installed into said optical disk device,
• wherein if a judgment result acquired by the judgment unit indicates a possibility of the multi-layered optical disk, said optical disk device executes:
• a first step of rotating the multi-layered optical disk;
• a second step of using the displacement unit, and thereby positioning the optical detection unit at a disk radius position at which the control information is reproducible;
• a third step of starting to drive the objective lens in an optical-axis direction of the laser light;
• a fourth step of making a comparison between the output signal from the band limitation unit and a predetermined level, and thereby detecting a peak of the output signal;
• and
• a fifth step of closing a focusing servo loop, after the peak is detected at the fourth step, when the digital signal indicates that the focal-point-achieved position of the laser light is in proximity to the recording layer of the multi-layered optical disk, and when the output signal from the band limitation unit is zero-crossed.

A multi-layered optical disk including two or more recording layers, comprising:

• a control-information recording layer which records therein control information which is reproducible in a state where only a focusing servo control is operated with respect to the multi-layered optical disk that rotates
• an other recording layer;
• and
• a rotation reference unit for indicating a rotation reference position of the multi-layered optical disk,
• wherein:
• a partial area of the control-information recording layer is an unrecording area at an angle larger than a predetermined angle;
• and
• the multi-layered optical disk not including the other recording layer in a radius area where the control information is recorded.