Abstract: A method is applied to reduce a range in variation of a target spin speed for a rotatable medium in a data storage device. The method includes rotating the rotatable medium at the target spin speed, determining an initial position of a head relative to a surface of the rotatable medium, determining a target position of the head relative to the surface of the rotatable medium, calculating an adjusted spin speed based on the initial position and the target position, sending a signal to rotate the rotatable medium at the adjusted spin speed, repositioning the head from the initial position to the target position, and sending a signal to rotate the rotatable medium at the target spin speed.

Abstract: Embodiments of the invention avoid erroneous drive current control at the time of a change in the drive waveform for a spindle motor. In one embodiment, a drive current setup section acquires the actual rotational speed from a rotational speed determination section. If the drive waveform is not changed, the feedback system for a first gain determines a drive current. Drive current data corresponding to the drive current is set in a register. If the drive waveform data switches to a curved wave during the next timing cycle, the feedback system does not perform any process, but the same drive current data as for the immediately preceding timing cycle is set in the register. During the next timing cycle, the actual rotational speed is acquired from the rotational speed determination section, and the feedback system for a second gain determines the drive current. When the drive waveform data changes, the feedback system process is skipped once.

Abstract: A storage system capable of reducing the start-up time of disk drives is provided. If a power source monitor circuit itself is normal (S93), the power source monitor circuit reads a detection signal from a detection circuit, and checks power sources (S94). If the power sources are normal (S95), all disks are spun up (S96). When the spin-up of all disks is completed (S98), processing is completed. If either of two power sources fails (S95), the power source monitor circuit reports the fact to a host control logical part (S99). The power source monitor circuit clears its internal counter to zero (S100) and issues a drive command to HDDs (S101). When the spin-up of all disks is completed (S103), processing is completed. If there is a disk which has not yet been spun up, the power source monitor circuit sets the internal counter to n+1 (S104) and returns to Step S101.

Abstract: In an index signal generator for generating an index signal for use in a direct-drive motor having a rotation axis and comprising a stator and a rotor, a particular at least one of M magnetized elements is used as an index detection magnet having magnetic force which is different from those in remaining ones of the M magnetized elements. Wound around one of a specific one of particular three cores in the stator, an index detection coil detects variations of the magnetic force generated by the ring-shaped permanent magnet to produce a detected signal. On the basis of the detected signal, the index signal is generated.

Abstract: Method and apparatus for characterizing the flight characteristics of a read/write head. A disc is accelerated to a selected rotational velocity sufficient to aerodynamically support the head. The head is positioned over a portion of the disc non-accessible to customer data and a magnetoresistive element of the read/write is biased using a suitable voltage or current. A media noise landing signature obtained as the element transduces white noise from the surface identifies the head as a low-flying head.

Abstract: A brushless motor has first and second power transistors which form current paths to three-phase windings so as to rotate a rotor. A position detecting part produces a position signal in response to a rotation of the rotor. An activation operation block controls active operation of the first and second power transistors in response to the position signal. The activation operation block includes a starting operation part which comprises an initial phase setting part, phase changing part and a phase correcting part. The initial phase setting part sets an initial phase of drive signals to the three-phase windings in response to the level of the position signal at the timing of a start signal. The phase changing part changes sequentially the phase of the drive signals to the three-phase windings in the positive direction in response to time.

Abstract: A method, computer program product and hard disk drive for restricting a rate of spin-up/spin-down cycles for a spindle motor in a hard disk drive. The firmware in the hard disk drive determines a maximum rate of spin-up/spin-down cycles the spindle motor is designed to handle over a designated period of time based on the number of spin-up/spin-down cycles the spindle motor is designed to handle over its expected lifetime. The firmware disables the automatic standby mode of operation if a calculated rate of spin-up/spin-down cycles during the designated period of time is greater than the maximum rate of spin-up/spin-down cycles the spindle motor is designed to handle over the designated period of time. By disabling the automatic standby mode of operation, the rate of spin-up/spin-down cycles will be reduced as the spindle motor will not incur a spin-up/spin-down cycle until the automatic standby mode of operation is enabled.

Abstract: A method for detecting a change in fly-height comprises measuring motor currents at various radii at a regular interval to determine the head drag. If any of the head drags at the various radii are greater than a threshold value, it is determined that a decrease in fly-height has occurred. If the disk drive has a head cleaner, a head cleaning is initiated to correct the fly-height change. If no head cleaning is necessary, a general error signal may be generated to indicate potential drive failure.

Abstract: A method and apparatus for providing a user selectable start-up current in a disk drive are provided. A user may select a relatively high start-up current to provide a relatively fast start-up time in a disk drive. Alternatively, the user may select a relatively low maximum current draw by the hard drive to enable a relatively low power, low cost power supply to be used in connection with the hard drive, for use with applications in which a relatively long start-up time is acceptable. In connection with applications in which a low cost power supply is to be used, the maximum current drawn by the disk drive may be limited to the amount of current required by the disk drive during seek operations.

Abstract: An apparatus, method, and system for writing data to a hard disk drive synchronous with an apparent disk speed. The apparatus, method, and system has a phase-locked loop (PLL) to generate am output clock signal, wherein a clock interpolator responsive to phase rotation control is in the PLL feedback loop. The phase rotation control is proportional to the apparent disk speed, and the PLL output clock signal is also proportional to the apparent disk speed. A second clock interpolator further modifies the PLL output clock signal to provide pre-compensation control.

Abstract: A computer system including a computer main body provided with a hard disk drive (HDD) to retrieve/store data and an HDD driver to drive the hard disk drive to rotate at a predetermined rotational speed, further including a lower noise mode selection part allowing a user to select one between a normal mode and a lower noise mode; and a controller to control the HDD driver to drive the hard disk drive to rotate at a maximum speed when the normal mode is selected and at a minimum speed when the lower noise mode is selected. With this configuration, the present invention provides a computer system and a control method thereof, in which a hard disk drive can be set to a lower noise mode by a user.

Abstract: A method and apparatus for managing power consumption of consumer electronic devices that run on a battery or an accumulator, particularly portable applications such as mobile phones, laptops or MPEG players or recorders. They consist essentially of a host and a storage medium like a disk or means for receiving a storage medium like a disk drive that are coupled with an interface. Power management is very important because long battery life enhances user convenience. The invention determines whether it is more efficient either to leave the disk drive in the idle mode or to switch the drive to standby until the next data request appears. The disk drive is entered into the most efficient power mode. The time until the next request is determined by the host.

Abstract: A method and device for controlling power consumption in a computer having a storage device including a motor and a storage medium is disclosed. The method comprises supplying a first power level to the motor of the storage device to spin the storage medium at a first rotational velocity, detecting a first predetermined condition and responsive to the detection of the first predetermined condition, supplying a second power level to the motor of the storage device to spin the storage medium at a second rotational velocity. A number of user defined preferences and system conditions in the computer may be taken into account in determining the second power level to the storage medium.

Abstract: The present invention provides a magnetic disk storage system including a spindle motor that rotates a magnetic disk, a spindle motor drive circuit that rotatably drives the spindle motor, a magnetic head that performs reading of information on the magnetic disk, a voice coil motor that moves the magnetic head, and a voice coil motor drive circuit that drives the voice coil motor. When the magnetic head is loaded from a standby position to the surface of the magnetic disk, the rotational speed of the spindle motor is made slower than a rotational speed at a normal operation. Upon power-off, the spindle motor drive circuit is caused to carry out a stepup converter operation to thereby generate a voltage higher than a back electromotive voltage, and causes a control circuit and a drive circuit to operate by the high voltage to thereby enable speed control at the movement of the magnetic head to a predetermined standby position.

Abstract: The invention relates to a disk drive and related method for improved disk rotation rate control in the presence of seek operations. A spindle motor rotates a spindle, supporting at least one disk with a magnetic recording surface, in response to a motor current. The actuator radially positions a transducer head over the recording surface. The motor is subjected to a torque load component related to the transducer head radial position. The spindle motor controller has a feedback control loop and a feedforward control element. The feedback control loop maintains a relatively constant spindle rotation rate based on a difference error between a predetermined target spindle rotation rate parameter and a measured spindle rotation rate parameter. The feedforward control element, in conjunction with a seek operation, adjusts the motor current based on a target head radial position with respect to an initial head radial position.

Abstract: A method and apparatus for generating an index location from a spin motor of a disk drive are disclosed. A disk drive includes a motor having a plurality of commutation states, wherein changes in commutation states are controlled by an FCOM signal having FCOM pulses. Ideally, when the motor is spinning at a constant speed, the time between FCOM pulses is constant. However, the inventor of the present invention has recognized that, in practice, the time between FCOM pulses, when measured more closely, is not constant due to mechanical tolerances in the motor. Accordingly, the inventor has determined that the non-constant times between FCOM pulses can be advantageously used to generate a spin motor index in a disk drive. Once obtained, the spin motor index may advantageously be used for a number of purposes.

Abstract: A storage system capable of reducing the start-up time of disk drives is provided. If a power source monitor circuit itself is normal (S93), the power source monitor circuit reads a detection signal from a detection circuit, and checks power sources (S94). If the power sources are normal (S95), all disks are spun up (S96). When the spin-up of all disks is completed (S98), processing is completed. If either of two power sources fails (S95), the power source monitor circuit reports the fact to a host control logical part (S99). The power source monitor circuit clears its internal counter to zero (S100) and issues a drive command to HDDs (S101). When the spin-up of all disks is completed (S103), processing is completed. If there is a disk which has not yet been spun up, the power source monitor circuit sets the internal counter to n+1 (S104) and returns to Step S101.

Abstract: Method and apparatus for accelerating a multi-phase motor having a rotatable rotor is disclosed. A first commutation state in which the rotor resides is identified, a first position of the rotor within the first commutation state is determined (preferably within one to two electrical degrees), and a travel distance for the rotor to advance from the first position to a second position is determined. An optimized activation time is next determined for utilizing substantially all available motor torque, and a first drive pulse is applied for the activation time to advance the rotor to the second position. The process is repeated until an intermediate velocity is reached, after which back electromotive force (bemf) commutation is used for control of the motor. The apparatus includes a controller programmed with routines that utilize speeds and accelerations of the motor in accordance with basic Newtonian laws to determine optimized activation times.

Abstract: A writer for head positioning information, or a so-called servo track writer allows the read gap to follow a track which has been established on a recording medium or disk. As long as the read gap keeps following the existing track, the write gap is allowed to move along a path extending in parallel with the existing track. The write gap is utilized to write head positioning or servo information into the recording medium along the path. Even when the recording medium suffers from vibration or the like, the read gap can follow the track. The head positioning information can thus be written into the recording medium so as to establish a head positioning pattern at a higher positional accuracy.

Abstract: The object is to raise controller gain while absorbing magnet position dispersion in a motor, and implement rotation control that is resistant to the influence of disturbance. There are provided a spindle motor 3 that performs rotational drive of a predetermined drive object, and a controller 121 that controls rotational drive of this spindle motor 3 by comparing a pulse time in rotational drive of this spindle motor 3 with a predetermined target time and performing feedback; and also provided is a peak filter 122 that compensates control by the controller 121 by varying the target time dynamically so as to suppress the rotation frequency and higher harmonic components thereof contained in the drive current waveform of the spindle motor 3.

Abstract: A disk drive is disclosed comprising an interface for receiving a primary supply voltage and a secondary supply voltage from a host computer. The primary supply voltage is applied to the windings of a multi-phase spindle motor in a commutation sequence, and the secondary supply voltage is connectable to a center tap of the windings.

Abstract: A disk drive having a layer of lubricant on a disk surface, where an undesirable lubricant layer thickness modulation is reduced by varying ?/f during operation of the disk drive. Here ? is the angular velocity of the disk and f is a resonant frequency of a head assembly containing the head. In this manner, the amplitude of the lubricant thickness modulation is decreased, improving disk drive performance. The ratio ?/f is preferably varied by varying the disk angular velocity ?.

Abstract: A motor drive device which controls a spindle output predriver unit and power MOSFETs of an output stage associated with it to form a PWM signal in such a manner that a detection current formed by a DC shunt resistor and a sense amplifier and a current instruction signal coincide with each other, generates a regenerative signal obtained by giving dead times to the PWM signal, generates an energizing timing signal from the result of BEMF (back electromotive voltage) zero cross detection and generates signals for controlling on/off of power MOSFETs of three phases to thereby drive a three-phase motor, is provided with a switching characteristic adjustment unit which measures a time at which the spindle output is being transitioned and performs such feedback control that the measured time and a designated switching time coincide with each other.

Abstract: A spindle motor in a disk drive is driven by a driving circuit that, upon receipt of a signal or command, selectively spins up the spindle motor according to a first spin up profile or according to a second spin up profile that is defined to provide a longer spin up time in comparison with the spin up time defined by the first spin up profile. The second spin up profile spins up the spindle motor in a longer period of time and/or generates less acoustic noise as compared to the first spin up profile.

Abstract: Hard disk drive track density is increased by selectively increasing the stiffness of a fluid dynamic bearing (FDB) motor during servo write. Applying a load to the shaft of a fixed shaft FDB motor to close the bearing gaps increases stiffness. Alternatively, the disk drive is cooled to increase bearing fluid viscosity or the motor is operated at an increased rotational velocity.

Abstract: A magnetic disk apparatus includes a low-rotation mode for decreasing the revolution number of a disk, in the low-rotation mode, any control signal for decelerating the disk is not generated to permit it to be decelerated owing to inertial drive and when a detected speed falls below a target speed, the disk is accelerated to thereby realize power saving.

Abstract: A brushless motor has first and second power transistors which form current paths to three-phase windings so as to rotate a rotor. A position detecting part produces a position signal in response to a rotation of the rotor. An activation operation block controls active operation of the first and second power transistors in response to the position signal. The activation operation block includes a starting operation part which comprises an initial phase setting part, phase changing part and a phase correcting part. The initial phase setting part sets an initial phase of drive signals to the three-phase windings in response to the level of the position signal at the timing of a start signal. The phase changing part changes sequentially the phase of the drive signals to the three-phase windings in the positive direction in response to time.

Abstract: A disk drive is disclosed employing either back electromotive force (BEMF) spindle speed control mode or wedge spindle speed control mode. A BEMF detector monitors the BEMF voltage generated by the windings of the spindle motor to generate a BEMF speed error. The BEMF spindle speed control mode is used to spin up the disk to an operating speed, and the wedge spindle speed control to maintain the disk at the operating speed. While in the wedge spindle speed control mode, a BEMF detection window is disabled to reduce acoustic noise.

Abstract: In a flexible disk drive for driving a flexible disk inserted in the flexible disk drive, when a power supply is turned on and when the flexible disk is not inserted in the flexible disk drive, a seek operation is inhibited and a track 00 signal is supplied to a host system just as if the flexible disk drive were operating normally.

Abstract: A system and method for assessing and potentially correcting for non-translational motion in a resonance measurement apparatus is provided. The design measures the response of an article, such as an HGA assembly including a read/write head, as well as the excitation of a shaking device, such as a head resonance tester, and computes a correction factor using either two or three point measurement. The correction factor may be evaluated by subjecting the arrangement to further vibration at varying frequencies. Measurement of the shaking device may be accomplished using an accelerometer or by optical measurement using a light beam.

Abstract: The performance capability of different heads that are part of the same hard disk drive (HDD) are utilized by an adaptive format that includes a plurality of storage zones and at least one reset zone that are distributed along a radius of the hard disk such that a reset zone is disposed between two adjacent storage zones. Each storage zone has a plurality of associated data tracks and each reset zone includes a plurality of data tracks. The number of data tracks associated with each respective storage zone is based on a performance capability of a head associated with the hard disk and includes at least one data track of at least one reset zone adjacent to the storage zone when the number of data tracks associated with the storage zone exceeds the number of data tracks that are between each reset zone adjacent to the storage zone.

Abstract: Optimizing performance of physical disk drives in a disk array storage device with a plurality of logical volumes is accomplished by accumulating statistics over an interval to select two logical volumes for an exchange. After testing to determine any adverse effect of making that change, the exchange occurs to more evenly distribute the loading on individual physical disk storage devices. One set of statistics, seek time, is obtained by combining estimated disk access information and an interpolated seek time obtained from a template that stores characteristics seek times among different pairs of segments that define a physical disk device independently of a logical volume configuration.

Abstract: A disk drive is disclosed employing either back electromotive force (BEMF) spindle speed control or wedge spindle speed control. The BEMF spindle speed control is used to calibrate a reference time period representing an accumulation of a predetermined number of wedge-to-wedge times. During wedge spindle speed control, a wedge time period representing an accumulation of a predetermined number of wedge-to-wedge times is measured, and a wedge speed error is computed as the difference between the reference time period and the wedge time period.

Abstract: A disk drive which can be used in particular under a low temperature environment is disclosed. The drive comprises a spindle motor (SPM) being a fluid dynamics bearing motor, and rotates a disk medium by the SPM. When an ambient temperature of the drive has changed to a low temperature, current consumption by the SPM increases to maintain steady rotation of the drive. When a CPU detects that current consumption by the SPM exceeds a specified value, the CPU restricts a current supplied to a voice coil motor (VCM) such that the total current amount does not exceed a specified maximum current capacity of the drive.

Abstract: A method for reducing written-in runout of a disk drive writes a plurality of servo tracks onto a magnetic-storage portion of a disk that comprises a first radial band proximate the outer circumference of the disk, and a second radial band between the first radial band and the inner circumference of the disk. A first plurality of servo tracks is written to the storage medium in the first radial band at a first servo-writing spin rate. A second plurality of servo tracks is written to the storage medium in the second radial band at a second servo-writing spin rate that is different from the first servo-writing spin rate.

Abstract: Disclosed are a system, a method, and a computer program product to disable the power-saving sleep mode of a disk drive if the drive detects an error at spinup that is a result of the read/write head sticking to the disk surface. The power saving sleep mode is avoided to prevent further spinup problems.

Abstract: An apparatus and method for compensating for variation in sample rate in a disc drive having a rotating disc and a head that is positioned over the rotating disc is provided. The disc includes at least one track that has multiple consecutive sectors. A sample rate value between timing marks of each pair of consecutive sectors of the multiple consecutive sectors is computed to obtain a sequence of sample rate values. A sequence of timing error values is computed as a function of the sequence of sample rate values and a nominal sample rate value. Data related to the sequence of timing error values is utilized to compensate for variation in sample rate values.

Abstract: In the present system and method, ZCP level signals of each phase voltage are first obtained. Among the detected ZCP level signals, some ZCPs are generated by phase back EMF, which are true ZCPs and other ZCPs by commutations, which are false ZCPs. The duration of the false ZCP level outputs varies with the excited phase current, inductance and back EMF of motors, the present invention utilizes fixed-width narrow pulse signals corresponding to the rising and falling edges of the ZCP level outputs in order to eliminate influences of the earlier disclosed motor parameters. These fixed width pulse signals make up the ZCP pulse signal. Because the first edge of the plurality of false ZCP level signal substantially corresponds to the switching-off signal of the commutated-off excited phase, a first false ZCP masking signal having pulses wider than the ZCP pulse signal are applied to mask the first plurality of false ZCP signals.

Abstract: A disk drive is disclosed comprising an interface for receiving a supply voltage from a host computer and control circuitry for controlling at least one operation of the disk drive. The supply voltage is applied to the windings of a multi-phase spindle motor in a commutation sequence during a normal operating mode, and a secondary voltage supplied by a center tap of the windings is used to power the control circuitry during the normal operating mode.

Abstract: The motor drive method is for a magnetic disk drive apparatus having a magnetic disk as an information recording medium, a magnetic head for recording/reproducing information to/from the magnetic disk, and a motor for driving the magnetic disk, the motor having a connection point connecting middle points in a multi-phase Y-connection and capable of realizing a unipolar drive method for successively exciting phases and a bipolar drive method for simultaneously exciting two adjacent phases, wherein the unipolar drive method is selected when the temperature in the magnetic disk drive apparatus is lower than a predetermined temperature and the bipolar drive method is selected when the temperature exceeds the predetermined temperature. The motor stationary rotation is assured by selecting the unipolar drive method or the bipolar drive method.

Abstract: An information storing device and an information processing device having a memory for registering a plurality of working modes at recording/reproduction and a switching circuit for selecting one of the plurality of working modes, which select the optimum working mode automatically or by an instruction of an operator according to power supply capacity of a device of higher rank to effect recording/reproduction.

Abstract: Dispersing and reducing wear of a rotatable disc surface using a stimulated take off process to accelerate formation of an air bearing between a read/write head and a non-textured circumferential landing zone of a rotatable disc surface of a disc drive by accelerating the non-textured circumferential landing zone of the rotatable disc surface to a rotational operating speed through application of a current to a spindle motor assembly securing the rotatable disc surface while stimulating a head stack assembly with a reciprocating lateral displacement effectuating a tracing of a radially varying path across and around the circumferential landing zone of the rotatable disc surface by the read/write head accelerating formation of the air bearing between the read/write head and a non-textured circumferential landing zone, thereby dispersing and reducing wear of the rotatable disc surface.

Abstract: A CPU sets an SPM driver in SPM start-up mode when a SPM is started up. At this time, a voltage selector applies, to a driver circuit, a voltage (high voltage) boosted by a voltage booster. A starter control circuit controls, during the period of an SPM start-up mode, the driver circuit with the high voltage applied thereto, thereby starting up the SPM. After the SPM has been started up, the CPU sets the SPM driver in PWM mode. At this time, the voltage selector switches the voltage applied to the driver circuit, from the boosted voltage to the voltage (low voltage) of a power supply. During the period of the PWM mode, a PWM circuit controls the driver circuit with the low voltage applied thereto, so as to rotate the SPM at a rated speed.

Abstract: Track mis-registration (TMR) correction is conditionally made in a hard disk drive using servo data in a closed loop servo control scheme, along with one or more alternative sensing schemes when an external shock or vibration occurs. The alternative sensing schemes include measurement of spindle motor speed using a frequency of servo markers read from a rotating disk, voice control motor (VCM) back emf, spindle motor speed back emf, and accelerometer readings. The predicted TMR resulting from the signal generated by the alternative sensing scheme(s) is simulated based upon a model of the disk drive system, and corrections are applied only if the expected TMR due to the disturbances is large enough that application of the corrections using the alternative sensing scheme would be likely to reduce the overall TMR.

Abstract: Track mis-registration (TMR) correction is conditionally made in a hard disk drive using servo data in a closed loop servo control scheme, along with one or more alternative sensing schemes when an external shock or vibration occurs. The alternative sensing schemes include measurement of spindle motor speed using a frequency of servo markers read from a rotating disk, voice control motor (VCM) back emf, spindle motor speed back emf, and accelerometer readings. The predicted TMR resulting from the signal generated by the alternative sensing scheme(s) is simulated based upon a model of the disk drive system, and corrections are applied only if the expected TMR due to the disturbances is large enough that application of the corrections using the alternative sensing scheme would be likely to reduce the overall TMR.

Abstract: Track mis-registration (TMR) correction is conditionally made in a hard disk drive using servo data in a closed loop servo control scheme, along with one or more alternative sensing schemes when an external shock or vibration occurs. The alternative sensing schemes include measurement of spindle motor speed using a frequency of servo markers read from a rotating disk, voice control motor (VCM) back emf, spindle motor speed back emf, and accelerometer readings. The predicted TMR resulting from the signal generated by the alternative sensing scheme(s) is simulated based upon a model of the disk drive system, and corrections are applied only if the expected TMR due to the disturbances is large enough that application of the corrections using the alternative sensing scheme would be likely to reduce the overall TMR.

Abstract: Track mis-registration (TMR) correction is conditionally made in a hard disk drive using servo data in a closed loop servo control scheme, along with one or more alternative sensing schemes when an external shock or vibration occurs. The alternative sensing schemes include measurement of spindle motor speed using a frequency of servo markers read from a rotating disk, voice control motor (VCM) back emf, spindle motor speed back emf, and accelerometer readings. The predicted TMR resulting from the signal generated by the alternative sensing scheme(s) is simulated based upon a model of the disk drive system, and corrections are applied only if the expected TMR due to the disturbances is large enough that application of the corrections using the alternative sensing scheme would be likely to reduce the overall TMR.

Abstract: A computer system including a computer main body provided with a hard disk drive (HDD) to retrieve/store data and an HDD driving part to drive the hard disk drive to rotate at a predetermined rotational speed, further including a lower noise mode selection part allowing a user to select one between a normal mode and a lower noise mode; and a controller to control the HDD driving part to drive the hard disk drive to rotate at a maximum speed when the normal mode is selected and at a minimum speed when the lower noise mode is selected. With this configuration, the present invention provides a computer system and a control method thereof, in which a hard disk drive can be set to a lower noise mode by a user.

Abstract: An apparatus for optically detecting rotational position information of a rotating object, includes a light source, a detector which is located at a position to receive scattered light from the rotating object when the rotating object is irradiated with a light beam from the light source, and outputs a frequency signal based on the scattered light, a signal processing system for detecting rotational position information by performing signal processing for the frequency signal from the detector, and a rotation control system for controlling rotation of the rotating object. The rotation control system preliminarily rotates the rotating object in detecting the rotational position information.

Abstract: For scanning a disc-shaped information carrier at a high average information rate with minimum access time, the angular velocity is decreased substantially as the radial distance to the scan location increases, while at the same time the linear velocity of track scanning increases substantially. The track may be divided into zones which are scanned with constant angular velocity. With respect to the inner tracks of at least two adjacent zones, or the innermost and the outermost tracks, the angular velocity decreases less than inversely with increase of radial distance, while the linear velocity increases less than proportionally with increase of radial distance.