An apparatus comprises a photodetector (PD) that irradiates a disk with laser light and outputs a signal based on a reflected light from the disk, a front monitor that outputs a reference signal based on an emitted light of a laser diode, and a data detection processing unit to which an output signal of the PD is input to generate a reproduction signal. The data detection processing unit includes a reproduction signal adaptive equalizer that outputs an equalization signal by adaptive equalization processing based on the PD output signal, and a laser noise adaptive equalizer that outputs the equalization signal by the adaptive equalization processing based on a laser noise signal, and generates the reproduction signal in which the laser noise is reduced on the basis of an arithmetic operation result of the output of the reproduction signal adaptive equalizer and the output of the laser noise adaptive equalizer.

Provided are an apparatus and a method for generating a reproduction signal with reduced laser noise. There are provided a photodetector (PD) that irradiates a disk with laser light and outputs a signal based on a reflected light from the disk, a front monitor that outputs a reference signal based on an emitted light of a laser diode, and a data detection processing unit to which an output signal of the PD is input to generate a reproduction signal. The data detection processing unit includes a reproduction signal adaptive equalizer that outputs an equalization signal by adaptive equalization processing based on the PD output signal, and a laser noise adaptive equalizer that outputs the equalization signal by the adaptive equalization processing based on a laser noise signal, and generates the reproduction signal in which the laser noise is reduced on the basis of an arithmetic operation result of the output of the reproduction signal adaptive equalizer and the output of the laser noise adaptive equalizer.

Provided are an apparatus and a method for generating a reproduction signal with reduced laser noise. There are provided a photodetector (PD) that irradiates a disk with laser light and outputs a signal based on a reflected light from the disk, a front monitor that outputs a reference signal based on an emitted light of a laser diode, and a data detection processing unit to which an output signal of the PD is input to generate a reproduction signal. The data detection processing unit includes a reproduction signal adaptive equalizer that outputs an equalization signal by adaptive equalization processing based on the PD output signal, and a laser noise adaptive equalizer that outputs the equalization signal by the adaptive equalization processing based on a laser noise signal, and generates the reproduction signal in which the laser noise is reduced on the basis of an arithmetic operation result of the output of the reproduction signal adaptive equalizer and the output of the laser noise adaptive equalizer.

A method includes detecting noise in a laser output of a heat assisted magnetic recording device. The noise is converted into an electrical signal including a numerical value. A least significant digit of the numerical value is selected. The least significant digit is concatenated with another least significant digit from another detecting of another noise in another laser output to form a number.

A method includes detecting noise in a laser output of a heat assisted magnetic recording device. The noise is converted into an electrical signal including a numerical value. A least significant digit of the numerical value is selected. The least significant digit is concatenated with another least significant digit from another detecting of another noise in another laser output to form a number.

In a multilayer optical disc having information layers conforming to a plurality of different optical disc standards, because the type of each information layer is not recorded in the other information layers, in read and write operations by a compatible optical disc device conforming to a plurality of optical disc standards, every time the information layer being accessed changes, it has been necessary to read the type of the information layer and select a method of generating a tracking error signal adapted to the type of information layer, so access has taken time. In order to solve the above problem, in the optical multilayer disc according to the present invention, having information layers conforming to a plurality of different optical disc standards, in an area in one of the information layers, information about the other information layers is recorded. The time required to access the other information layers can be reduced by using this information to select a tracking error signal generating method.

In a multilayer optical disc having information layers conforming to a plurality of different optical disc standards, because the type of each information layer is not recorded in the other information layers, in read and write operations by a compatible optical disc device conforming to a plurality of optical disc standards, every time the information layer being accessed changes, it has been necessary to read the type of the information layer and select a method of generating a tracking error signal adapted to the type of information layer, so access has taken time. In order to solve the above problem, in the optical multilayer disc according to the present invention, having information layers conforming to a plurality of different optical disc standards, in an area in one of the information layers, information about the other information layers is recorded. The time required to access the other information layers can be reduced by using this information to select a tracking error signal generating method.

A method includes detecting noise in a laser output of a heat assisted magnetic recording device. The noise is converted into an electrical signal including a numerical value. A least significant digit of the numerical value is selected. The least significant digit is concatenated with another least significant digit from another detecting of another noise in another laser output to form a number.

A method includes detecting noise in a laser output of a heat assisted magnetic recording device. The noise is converted into an electrical signal including a numerical value. A least significant digit of the numerical value is selected. The least significant digit is concatenated with another least significant digit from another detecting of another noise in another laser output to form a number.

A method includes detecting noise in a laser output of a heat assisted magnetic recording device. The noise is converted into an electrical signal including a numerical value. A least significant digit of the numerical value is selected. The least significant digit is concatenated with another least significant digit from another detecting of another noise in another laser output to form a number.