Abstract: Provided is a power saving control method and system for data storage devices or electrical equipment. Herein, data items are divided into groups according to required response times or access frequencies. The groups of data items are allocated to data storage devices or pieces of electrical equipment. A data storage device or electrical equipment to which data that may be accessed using a long response time at a low access frequency is set to a power-saving mode of a higher level. Consequently, the data storage devices or pieces of electrical equipment are provided with power-saving features of different levels. Eventually, energy saving can be achieved more efficiently.

Abstract: Provided is a power saving control method and system for data storage devices or electrical equipment. Herein, data items are divided into groups according to required response times or access frequencies. The groups of data items are allocated to data storage devices or pieces of electrical equipment. A data storage device or electrical equipment to which data that may be accessed using a long response time at a low access frequency is set to a power-saving mode of a higher level. Consequently, the data storage devices or pieces of electrical equipment are provided with power-saving features of different levels. Eventually, energy saving can be achieved more efficiently.

Abstract: An optical head unit includes a motor having a stator and a rotor which is mounted rotatably on the stator, at least the rotor having a generally disk-shaped (i.e., circular or polygonal) configuration, and an optical system mounted on a common, main surface of the rotor. The optical system includes a light emitting part for emitting a light beam, a focus actuator, an objective lens provided on the focus actuator, and a light beam receiving part. The light beam emitted from the light emitting part is output via the objective lens, and light received via the objective lens is received by the light receiving part.

Abstract: A read out apparatus reads out prerecorded information from a magneto-optic disk by detecting intervals of edges of magnetic domains formed on the magneto-optic disk with different directions of magnetization, where the intervals of the edges of the magnetic domains correspond to data "1"s or "0""1"s of the prerecorded information.

Abstract: A light control circuit of an optical disc system for controlling light from a light emitting element at a read power level even if a write data operation is performed. The light control circuit includes a light control circuit, a superimposedly energizing circuit for providing a light for data write and a subtraction circuit for subtracting a predetermined current from a light sensing element. A light control circuit may further include a reference value setting circuit for automatically finding and determining reference values of a read power level, a write power level, and a subtraction value. The reference values may be defined with respect to an origin of the characteristic of the light emitting element where a current flowing through the light emitting element is substantially zero.