Abstract: A method of recording data into a recording medium by forming a recording region which is physically different from the nonrecorded portions is disclosed. The optical data recording/reproducing method includes a first trial writing operation in which trial writing data are recorded into the recording medium while changing the recording power conditions, the recorded trial writing data are reproduced, and the reproduced trial writing data are evaluated to set an optimum recording power. The method also includes a second trial writing operation in which trial writing data are recorded into the recording medium while changing the servo conditions, the recorded trial writing data are reproduced, and the reproduced trial writing data are evaluated to set optimum servo conditions.

Abstract: Regions A–F of photodetectors output electric signals a–f respectively, in accordance with an amount of reflected light from an optical disc 1. The electric signals a–f are input to A/D converters through an RF amplifier unit respectively. An arithmetic circuit subjects the electric signals a–f to arithmetic processing, so as to generate a focus error signal FE and a tracking error signal TE. A CPU measures a DC level of an output signal from the A/D converter, and transmits control signals OCa–OCf to a variable resistor in the RF amplifier unit so that a difference between the DC level and a median in a dynamic range of the A/D converter attains “0”. The CPU transmits control signals GCa–GCf to a variable resistor in the RF amplifier unit so that output amplitude of an output signal is within the dynamic range.

Abstract: An optical disk device comprises position control portions which carry out position control of at least one of an optical head and an objective lens based on a detection signal from the optical head, and disturbance learning portions which reduce a compensation gain of the position control portion in a range in which servo control is not deviated, and detect disturbance information of the optical disk to store it as learning disturbance information. Fine disturbance information can be reliably learned because the information is not affected by the compensation gain.

Abstract: The optical disc apparatus comprises a convergence lens 12, a light detection device 14 for outputting a first and a second detection signals after detecting reflected optical beam area by area, an actuator 13 for shifting the convergence lens 12, a gain balance circuit 30 for changing a gain balance of the first and the second detection signals, an addition circuit 123 for outputting the addition signal AS after adding the first detection signal to the second detection signal in response to the shift in lens position and the change in gain balance made by the gain balance circuit 30 and the actuator 13, and an addition signal measurement unit 361 and a gain balance adjustment unit 362 operable to obtain the addition signal AS from the addition circuit 123, specify the gain balance that equalizes the detection sensitivities in the respective areas of the light detection device 14 based on the obtained result, and control the gain balance circuit 30 that realizes the determined gain balance.

Abstract: An optical disc system comprises a gain offset unit for giving a gain and an offset to an inputted reproduction signal, an A/D converter, a peak detector, a bottom detector, an amplitude detector for calculating a signal, an offset detector for calculating a signal offset, a dropout detector for detecting a dropout in the input signal, and a controller for performing gain control and offset control of the gain offset unit, the controller being able to hold the control operation or switch the control speed by a hold signal that is supplied from the outside, wherein a defect in a recording medium is detected to hold the gain control and offset control or change the control response speed, whereby the signal amplitude and offset at the input of the A/D converter are always kept constant.

Abstract: A method and device are provided for adjusting a focus bias of an objective lens of an optical pickup for an optical disc using a level of a tracking error signal. The level of the tracking error signal outputted when the optical disc is rotated and driven is detected for a predetermined period of time. An operation of adjusting the focus bias of the objective lens is carried out on the basis of the detected level of the tracking error signal. A focus bias adjustment value is set as an optimum focus bias value at a time when the detected level of the tracking error signal is maximized. In accordance with the method, a period of time for adjusting the focus bias is very short, on the order of “0” to several hundred milliseconds, in comparison with periods of time for adjusting the focus bias in conventional methods, such that the focus bias can be quickly adjusted.

Abstract: A method is provided for regulating the tracking of a scanning device, for example, a read/write head, of a drive. A drive for storage media having a scanning device is also provided, permitting improved regulation of the positioning of the scanning device. A measured position of scanning device with respect to a storage medium inserted into the drive is compared with a preselected position. Depending on the result of the comparison, at least one actuator is controlled so that the scanning device is moved in the direction of the preselected position. Acceleration acting on the scanning device is measured in a direction of movement of at least one actuator. A correction signal is derived from the measured acceleration and sent to the at least one actuator, the actuator being controlled by the correction signal so that it counteracts the acceleration acting on the scanning device.

Abstract: Track jumping on optical storage media whose address information items invalidate the track error signal at time intervals is intended to be configured more securely and more reliably. For this purpose, at the end of a coarse jump, one or more correction jumps are carried out if the optical scanner is not presently sweeping over an address information area and the track change frequency of the tracks crossed by the scanner falls below a predetermined value.

Abstract: A track-locking method for an optical disk drive is conducted according to the following steps. First, a tracking error signal (TE signal) is detected, and then the time period for a pickup head jumping from one track to another track is divided into four periods. Secondly, the extreme values of the reshaped tracking error signal (TE? signal) in the first, second and third periods are preset, and the TE signal of the first period is reshaped in view of the extreme value of the TE? signal in the first period and the crest value or the trough value of the TE signal, so as to form the TE? signal in the first period. Then, a line connecting the extreme values of the TE? signal in the first period and the second period is established as the TE? signal in the second period, and a line connecting the extreme values of the TE? signals in the second and third periods is established as the TE? signal in the third period.

Abstract: A disc apparatus (10) includes an optical lens (14). A laser beam is irradiated onto a recording surface of the magneto-optical disc (68) through the optical lens (14), and a TE signal or an RF signal is detected on the basis of the laser beam reflected by the recording surface. Herein, an MPU (50) replaces the optical lens (14) in an optical axis direction, and a TE signal detection circuit (42) or an RF signal detection circuit (60) detects the TE signal or the RF signal at each of lens positions. A laser power is adjusted by the MPU (50) such that amplitude of each of the TE signal or the RF signal detected is below a saturation value. When a parameter is adjusted, a position of the optical lens (14) is controlled such that the amplitude of the TE signal or the RF signal detected thereafter is maximized.

Abstract: A real-time wobble detector and an adaptive layer distance balancing calculator are added in a layer jump control device of a high-speed optical drive to solve failure and instability caused by the wobble effect of the optical drive during layer jump. A layer jump control method of the optical drive is also provided.

Abstract: A system provides a signal to an actuator within an optical pickup unit of an optical disk drive. In one implementation, SUM signal data (an output from the quad sensors typically present in the optical pickup unit) is recorded within a SUM table. An error term generator processes the SUM signal data from the SUM table to produce an error term. An actuator control signal generator generates a signal to control movement of the actuator, wherein the signal is a function of a prior actuator position, the error term and an adaptation coefficient, wherein the adaptation coefficient impacts a rate at which the error term is allowed to modify the prior actuator position.

Abstract: A recording and reproduction apparatus for a recording medium including a plurality of information layers includes a focusing signal generation section for generating focusing signals F+ and F? in accordance with a light beam reflected by the recording medium; a focusing control section for generating a focusing error signal in accordance with a difference between the focusing signals F+ and F?, and performing focusing control for maintaining a distance between a focal point of the light beam and a target information layer within a prescribed tolerable range; and a gain setting section for setting a focusing servo gain in accordance with the focusing error signal. The focusing signal generation section generates the focusing signals F+ F? so that values of components thereof based on the light beam reflected by an information layer other than the target information layer are substantially equal while focusing control is being performed.

Abstract: An optical recording apparatus includes an optical pickup unit for generating and directing optical signals onto a given optical medium, and for detecting corresponding reflected optical signals from the optical medium; a focus motor for moving a focusing lens on the optical pickup according to a focus signal for adjusting a defocus of the optical signals on the optical medium; and a focus controller for generating the focus signal. During write operations of the optical recording apparatus, the focus controller is for performing write defocus calibration on the given optical medium to determine an optimal write defocus value for the optical medium. If the optical medium has multiple layers, the write defocus calibration is performed on a particular layer of the optical disc toward which write operations are directed. If the optimal defocus write value is different than a starting write defocus value, an updated write defocus value is stored.

Abstract: A method for controlling an optical pickup head of an optical processing apparatus is provided. A first lead-lag compensator is disabled and a second lead-lag compensator is enabled when the optical pickup head switches from a following mode to a seeking mode. Then, an initial operating factor of the second lead-lag compensator is determined according to a last input value and a last output value of the first lead-lag compensator. An initial kick force of the actuator in the seeking mode is calculated by realizing the last input value and the last output value of the first lead-lag compensator immediately before the first lead-lag compensator is disabled. Finally, the optical pickup head is actuated to perform a seeking operation with the initial kick force.

Abstract: An optical pickup actuator circuit includes: a lens holder 2 supported so as to be slidable along a support shaft and rotatable around the support shaft and for holding an objective lens 8 so that the objective lens 8 forms an image of a light beam on a desired track on an information recording surface of an optical disk; a focusing coil 7 attached to the lens holder 2; and a focusing magnet fixedly disposed so as to be opposite to the focusing coil 7; wherein two diodes D1 and D2 are parallel-connected in a forward direction between an input end 7a of the focusing coil 7 and the ground so that an input voltage not lower than a predetermined voltage is led to the ground by the two diodes D1 and D2.

Abstract: An optical recording medium (D) includes tracks (T) extending along a spiral. The tracks (T) include a plurality of first sections (Ta) and a plurality of second sections (Tb) differing from the first sections with respect to at least one of width and depth. Each of the first sections (Ta) includes a first overlapping portion (11) in which the trailing end and other portion of the first section overlap each other in the tracking direction, the trailing end and the other portion of the first section being located in adjacent tracks. Each of the second sections (Tb) includes a similar configured second overlapping portion (12). Due to such a structure, the beam spot can be easily caused to circulate on the same track of the optical recording medium (D) during idling.

Abstract: An optical disc unit 2001 comprises: reflective surface detection means 1010 for detecting a reflective surface; focus control means (1202, 1003, 1009, 1008, 1003, 1012, 1005 and 1204) for performing focus control to a reflective surface so that the distance between the focal point of an optical beam applied to an optical disc 2100 and the reflective surface is within a predetermined error limit; shift means 1007 for shifting the focal point of the optical beam in a direction perpendicular to the optical disc; and control means 1006 for controlling the focus control means and the shift means.

Abstract: An optical disc device for changing intensities of light beams illuminated on an optical disc. The optical disc device comprises the following elements. A photo detecting device divided into a plurality of photo detectors is used for detecting the reflected light beams illuminated on an optical disc. A plurality of amplifiers is used for changing gains to respectively amplify the output signals of the photo detectors when recording and reproducing on/from the optical disc. A calculating device is used for calculating the output signals of the amplifiers to generate the servo signals. By adding the correction offset signals for correcting the offset voltages of the amplifiers and the photo detectors to the amplifiers, the correction offset signals are amplified. It is, therefore, not necessary to change the correction offset voltages even though the gain of the amplifier is changed and not necessary to change the offset voltage and is independent of the gain-switching of the amplifier.

Abstract: In a layer jump, a control signal based on a focus error signal is masked in a period based on a moving speed of an objective lens so as not to be influenced by an unnecessary light component. Thereafter, an observation of the control signal based on the focus error signal is restarted, and a brake signal is sent to the objective lens, and a focus servo is switched to the ON status. Thus, accuracy of the layer jump is improved when the unnecessary light component exists in an interlayer portion of the focus error signal.

Abstract: A signal processing apparatus is provided with a converter for converting at least one analog light detection signal into a digital light detection signal, and a signal generator for generating at least one servo error signal by subjecting the digital light detection signal to a predetermined operation process. The signal generator has a function of modifying contents of the operation process.

Abstract: The present invention provides an information storage apparatus that generates a tracking error signal based on a detection signal, and performs various control operations based on the tracking error signal. When the operation mode is a seek operation mode, the information storage apparatus generates a tracking error signal by holding the peak value of the detection signal. When the operation mode is a tracking operation mode, the information storage apparatus generates a tracking error signal directly from the detection signal. With this information storage apparatus, stable control operations can be performed, regardless of changes of conditions.

Abstract: A circuit for generating a compensation signal (TC) to compensate a tracking error (TE) swing in a servo control system, the TC signal being pre-defined in accordance with an algorithm for generating a TE signal, the circuit comprising a set of peak detection devices corresponding to a set of photo-detector elements formed in a photo-detector, each of the peak detection devices detecting an amplitude of an optical detection signal derived from a corresponding photo-detector element, a set of amplifiers of a same gain corresponding to the set of peak detection devices, the gain being selectable between an inverting and a non-inverting terminals, a set of gain selection signals corresponding to the set of amplifiers to select one of the inverting and non-inverting terminals in accordance with the pre-defined TC signal, and an adder for adding the amplitudes that are gain selected.

Abstract: A reference-position learning unit measures a current of one rotation of a medium in a state in which the focus of an objective lens is pulled-in by a focus pull-in control unit at a predetermined point in the radial direction of the medium upon insertion of the medium, calculates a mean current value thereof, and stores the calculated mean current value in the memory as a reference current value for positioning the objective lens at a reference position at which focus pull-in control is started. In focus pull-in performed after a learning process, a reference-position control unit positions the objective lens at a reference position obtained through a learning process in accordance with the reference current, and then, causes the focus pull-in control unit to perform focus pull-in.

Abstract: A beam position control system controls a position of a beam directed from a beam source. The beam position control system includes a beam position sensing system that generates one or more satellite beams which are used to determine the position of a main beam. A beam offset computation block determines a relative position of the main beam with respect to a desired main beam position and provides beam offset information to a controller that generates a compensation signal used to adjust the main beam position to the desired main beam position via a beam actuation system.

Abstract: The present invention provides a control system of following a follow target position. A control system has a disturbance observer for obtaining a disturbance force estimation value and a speed estimation value as estimation values of a disturbance force and a speed as a speed to be controlled by using an actuator control signal cont and a zero follow position which can be observed. Since the disturbance force estimation value and speed estimation value are fed back.

Abstract: An apparatus and method for detecting a wobble signal read from an optical disc. The wobble signal detection apparatus comprises an analog/digital (A/D) converter for A/D-converting an analog wobble signal, read from the optical disc and then band pass filtered, a slope detector for detecting a slope of the A/D-converted wobble signal according to a variation thereof, and a wobble signal detector for detecting a peak point of the A/D-converted wobble signal using the detected wobble signal slope, and detecting/outputting a square-wave wobble signal with a high level or low level transition at the detected peak point. The slope detector calculates variations of data values of the A/D-converted wobble signal sampled within a predetermined period on the basis of predetermined different weights, accumulates the calculated values and detects the slope of the A/D-converted wobble signal on the basis of the accumulated value.

Abstract: An apparatus which stabilizes an operation of a disc driver in a mode conversion setting section includes a pickup which reads information from a disc that is inserted into the disc driver, a filter which performs a low-pass filtering of a servo error signal that is generated during an operation of the pickup, a selector which selects one of the servo error signal and the low-pass filtered servo error signal from the filter and outputs the selected servo error signal to drive the pickup using the selected servo error signal, and a control signal generator which generates a signal to control the selector to select the low-pass filtered servo error signal in a mode conversion setting section of the disc driver. Accordingly, a defocus and a detrack can be prevented in the mode conversion setting section of the disc driver.

Abstract: A focus error signal offset calibration is presented. The focus error signal offset can be calibrated by varying the focus error signal offset to optimize an operating characteristic of the optical disk drive. In some embodiments, the operating characteristic can be a servo function. In some embodiments, the operating characteristics can be a read function.

Abstract: A focus control system for an optical pickup head is provided. The optical head generates an electronic signal in response to an optical signal. The focus control system comprises a focusing error signal generator, a focus control signal generator and an actuator. The focus control signal generator is electrically connected to the focusing error signal generator, and includes a first, a second and a third compensators with a first, a second and a third gains, respectively, for generating a focus control signal with one of the first, second and third gains in response to the focusing error signal according to a corresponding one of a first, a second and a third operating modes of the optical pickup head. A method for controlling movement of an optical pickup head is also provided.

Abstract: A focusing method of layer jump for an optical storage device to retrieve data from a multi-layer optical disc is disclosed. The optical disc includes first data layer and second data layer. Before layer jump, the focus is on the first data layer, and the second data layer is the target data layer to proceed with layer jump. If layer-jump failure, no matter where the focus is, an auxiliary force is provided to let the lens continuously move along the layer jump direction and prevent the focus from locating between the two data layers. And then, the lens moves along a backward direction to set on the second data layer according to a reference signal.

Abstract: A method of an optical disk drive for determining both an optimum write power and an optimum tracking offset value using a test area reserved for a conventional OPC operation by determining a coarsely adjusted laser power using a portion of the test area, determining an optimum tracking offset using another portion of the test area, and determining an optimum write power using the remaining portion of the test area. The optimum tracking offset ensures that the RF signal is not affected by a wobble formed on a groove.

Abstract: An optical disc reproduction apparatus is provided for permitting appropriate automatic adjustment to a servo control system, particularly a CD and a DVD-ROM having a BCA. A limit switch 24 is disposed in such a manner that it detects movement of an optical pickup 11 to a position which is located at a radius of 23.49 mm from the center. A system controller 22 moves the optical pickup 11 by 1.0 mm in an outer radial direction from the position detected by the limit switch 24, and reads a signal from an optical disc 5 at that position to carry out the automatic adjustment to the servo system, through a servo controller 21 and a feed motor 18. As a result, in the CD, a signal within a lead-in area thereof is used for and subjected to the automatic adjustment performed by the servo controller 21, while in the DVD-ROM, a signal in an outer peripheral area of a lead-in area having the BCA and in the vicinity thereof is used for and subjected to the adjustment.

Abstract: The present invention provides a low-cost optical recording device that determines an optimum quantity of light for recording and reproducing, and an optimum focus offset value. The present invention also relates to a method of determining such an optimum focus offset value. The optical recording device is equipped with a focus control system for performing a focus control operation to focus light from a light source onto a recording face of an optical recording medium.

Abstract: On an optical disc including a substrate on which pits having at least two different depths are formed, main information is recorded by the shape of the pits and additional information is recorded by the depth of the pit. It is possible to reverse polarity of a tangential push-pull signal dependent on the depth of the pit, and therefore it becomes possible to record information utilizing the depth of the pit. This improves recording density of the optical disc. Further, when information of the optical disc is to be copied, the information recorded by the depth of the pit cannot be copied. Therefore, unauthorized reproduction can be prevented.

Abstract: An optical system of an optical recording apparatus forms a main spot and sub-spots preceding and succeeding the main spot on a signal recording medium. The optical system is set such that the sub-spot is shifted from the main spot in the direction orthogonal to a signal track by a distance expressed by an expression (2k?1)P/4(k=natural number), in which P denotes a distance between adjacent signal tracks on the signal recording medium. Thus, the sub-spot succeeding the main spot can be used to effectively read the state of a signal recorded on the signal recording medium by the main spot.

Abstract: The quantity of spherical aberration correction is predetermined for each recording plane of an optical disk on which focusing control is performed. Before operating the focusing control, the quantity of spherical aberration to be corrected by an aberration correcting system is set based on an output signal from an aberration correction quantity switching device that corresponds to the type of the optical disk and the recording plane to be subjected to the focusing control. This makes it possible to perform stable focusing control on each recording plane of a multi-layer optical disk with high density by using an objecting lens having a large NA after spherical aberration has been corrected properly.

Abstract: An optical storage device decreases the influence of return light to the laser light source and prevents an increase of power consumption even if high frequency superimposing is performed. The optical storage device applies drive current, to which a high frequency signal is superimposed, to the laser light source, and reads/writes data from/in the storage medium. The high frequency superimposing is set to OFF as a default to save power consumption, and high frequency superimposing is turned ON only when it is judged that servo is unstable, and high frequency superimposing is turned OFF when it is judged that servo is stable.

Abstract: A pull-in point setting circuit 16 sets the intermediate value between the maximum value and minimum value of the focus error signal of a layer 1 as the pull-in point of a focus servo action in advance of the playback of an optical disk 11. At a layer jump before the automatic adjustment of a focus bias, the focus servo action is pulled in at the set point. Thus, the layer jump can be reliably effected even before the adjustment of the focus bias.

Abstract: The present invention is a method and system to provide focus control in a multi-layer optical storage medium. The method comprises generating a beam of light and reflecting the beam of light off one of a first and a second optical layers on a disk. The reflected beam is detected and a servo signal is provided in response to the reflected beam. The light source is directed to move from a first position to a second position based on the servo signal, so as to focus the light source from one of the first or the second optical layer to another one of the first or the second optical layer.

Abstract: A pickup is moved in a direction opposite to a pickup moving direction in which the pickup is to be moved. At a timing at which a period of time corresponding to one period of oscillation generated on an objective lens of the pickup has passed after moving the pickup in the direction opposite to the pickup moving direction, the pickup is moved in the pickup moving direction.

Abstract: An apparatus and method for high-speed searching of an optical medium having a plurality of tracks. Light spots are directed by the apparatus onto the optical medium. As the spots traverse across the tracks in one of a first direction and a second direction, a photodetector unit receives reflected components of the light spots, thus forming respective electrical signals. Digital shaping circuitry converts the electrical signals into digital signals. A quadrature detector receives the digital signals which are arranged in quadrature relationship to each other, and produces an up-count signal indicating the light spots are traversing the tracks in the first direction and a down-count signal indicating the light spots are traversing the tracks in the second direction. A counter counts the up-count signal and the down-count signal to determine a number of tracks traversed by the light spots.

Abstract: An offset measuring method is for measuring an offset based on an optical beam reflected by an information medium, in a recording and reproduction apparatus including an optical pickup placed on transportation means so as to be driven along a radial direction of the information medium. The method includes the steps of directing an optical beam toward a first measuring position, thereby measuring a first offset amount based on the optical beam reflected at the first measuring position; moving the transportation means by a first distance in a first direction along the radial direction; driving the optical pickup by a second distance, which is equal to the first distance, in a second direction; and directing an optical beam toward a second measuring position, thereby measuring a second offset amount based on the optical beam reflected at the second measuring position.

Abstract: A method is provided for outputting a focusing completion signal to realize a focusing condition of an optical pickup head for an optical access apparatus. The method is described as follows. A trace shift of the optical pickup head along a focusing direction is actuated in response to a focus control signal when a focus adjustment operation starts. Then, a focusing error signal and a sub-beam addition signal are generated in response to optical signals from the optical pickup head. A closed-loop enable signal is generated to enable a closed-loop control operation in response to a specified situation of the focusing error signal. The focusing completion signal is outputted when the sub-beam addition signal is at a level greater than a threshold value and when the closed-loop enable signal is generated.

Abstract: The invention provides a method for adjusting a speed-detection device for an object lens in an optical pickup head. The invention provides an adjusted optical disc drive, wherein the optical pickup head is accelerated/decelerated and the speed-detection device outputs a standard signal level. Next, the optical pickup head of an unadjusted optical disc drive is accelerated/decelerated under the same condition, and the speed-detection device outputs a speed signal level. Finally, the gain of a programmable gain amplifier is adjusted until the speed signal is equal to the standard signal.

Abstract: A position control apparatus which includes position error signal detection means for detecting a position error signal of the mechanical part and position control means for controlling the position of the mechanical part by supplying to it the position error signal from the position error signal detection means, whereby the apparatus has provided therein phase compensation means comprising a digital filter; the position error signal is supplied to the phase compensation means to perform phase compensation thereon and the phase-compensated position error signal is supplied to the position control means; and, when starting a closed-loop control, filter variables that were used at a time preceding by an amount of time equal to or greater than that corresponding to the amount of one sampling time of the digital filter have been reset.

Abstract: A calibration method for an optical disk drive is presented. The operating parameters of an optical disk drive are initially calibrated when the disk drive is produced or during a repair step. The disk drive is then field calibrated during normal operation. Operating parameters can be field calibrated during power up. Further, operating parameters can be field calibrated when a new optical media is inserted into the optical disk drive. Additionally, operating parameters can be field calibrated during error recovery.

Abstract: A system with a plurality of servo algorithms executing on a digital signal processor is presented. The digital signal processor receives a sensor interrupt, indicating availability of digitized data from optical sensors, and decides which of a plurality of servo algorithms to service in response to the interrupt. In some embodiments, the plurality of servo algorithms includes a tracking servo algorithm. In some embodiments, the plurality of servo algorithms includes a focus servo algorithm. In some embodiments, multi-track seek operations or one-track jump operations can also be serviced during the interrupt period.

Abstract: A gain calibration device and method for differential push-pull (DPP) tracking error signals in an optical storage system is provided. The gain calibration method processes the synthesized gain (SPPG) of the sub beam in the DPP tracking error signal components with respect to the main beam. The calibration theorem resides in controlling the objective lens of the pick-up head to form a lens-shift or controlling the tilt of the objective lens relative to the optical disc to make the synthesized DPP tracking error signals generate a correspondingly signal variation owing to the optical path deviation. The synthesized gain is calibrated to make the signal variation a minimum value, and the calibrated synthesized gain is the optimum value.

Abstract: A digital servo system with a biased feed-forward control is disclosed. The biased feed-forward control determines the low frequency component of a control signal from the digital servo system. The low frequency component can then be added to a future control signal to form an adjusted control signal. In some embodiments, the low frequency component is then removed from the future control signals. In some embodiments, a bias signal is incremented or decremented in response to the low frequency component, the bias signal being added to future control signals.