Abstract: A tracking servo system with a feed-forward control loop is presented. Periodic variations in a control signal can be detected. These periodic variations can be added into the control signal to form a new control signal so that on subsequent cycles the control signal does not include the periodic variations.

Abstract: A device with an optical disk drive with a digital servo system for controlling tracking or focus in an optical disk driver is presented. A servo system according to the present invention includes an optical pick-up with detectors providing optical signals, an analog processor receiving the optical signals and providing a digital signal, and digital processors receiving the digital signal and providing a control signal that controls the position of the optical pick-up unit. The digital processor executes an algorithm that calculates an error signal, provides amplification and biasing to the error signal, provides filtering for the error signal, and computes the control signal. The error signal can be the focus error signal or the tracking error signal. The device can be any device.

Abstract: A servo system with a multi-track seek algorithm with an track zero crossing period integrity test is presented. Zero crossing periods for subsequent cycles can be determined from a tracking error signal. If the zero crossing period for a first cycle differs substantially from the zero crossing period for a second cycle, then an error can be indicated. In some embodiments, the first cycle and the second cycle are subsequent cycles. In some embodiments, the zero crossing period in the second cycle can be between half and twice the zero crossing period in the first cycle. In some embodiments, other ranges are utilized. For example, in some embodiments the zero crossing period in the second cycle can be between one quarter and four times the zero crossing period in the first cycle.

Abstract: A determination of a focus sum threshold in a tracking and focus servo system of an optical disk drive is presented. The focus sum threshold can be determined by moving an optical pick-up unit sinusoidally through a focus position, for example by moving the optical pick-up unit between its closest position to an optical media and its farthest position from the optical media. While moving the optical pick-up unit, a sum signal is monitored. In some embodiments, the sum signal is the sum of signals from a plurality of detectors in the optical pick-up unit. The focus sum threshold is set to a fraction of a peak value of the sum signal.

Abstract: A direction sensor in a tracking and focus servo system of an optical disk drive is presented. The direction sensor calculates a direction sum signal and a tracking error signal from side elements of detectors in an optical pick-up unit of the optical disk drive. A first direction can be indicates when the signs of a high-pass filtered sum signal and a high pass filtered tracking error signal are opposite and a second direction opposite the first direction if the signs are the same.

Abstract: A digital servo system for controlling tracking or focus in an optical disk driver is presented. A servo system according to the present invention includes an optical pick-up with detectors providing optical signals, an analog processor receiving the optical signals and providing a digital signal, and digital processors receiving the digital signal and providing a control signal that controls the position of the optical pick-up unit. The digital processor executes an algorithm that calculates an error signal, provides amplification and biasing to the error signal, provides filtering for the error signal, and computes the control signal. The error signal can be the focus error signal or the tracking error signal.

Abstract: A servo system with a multi-track seek algorithm is presented. The multi-track seek algorithm detects zero crossings in a tracking error signal, counts the number of zero crossings to form a count, and calculates a reference velocity from the count. The algorithm also determines a time period between successive zero crossings, calculates a velocity from the time period, calculates a difference signal between the reference velocity and the velocity, and adjusts the control signal so that the velocity follows the reference velocity. The reference velocity can follow a velocity profile with acceleration portions, coasting portions, and deceleration portions which move an optical pick-up unit from a starting position to a target position.

Abstract: A servo system with a multi-track seek algorithm with an accelerated servo function for regaining a closed tracking loop is presented. Upon completion of a multi-track seek operation, a gain of a tracking servo system is increased for a predetermined number of cycles. In some embodiments, the increased gain leads to a more aggressive track closing operation.

Abstract: A system, method, and apparatus for coordinating tasks in a control system for an optical disc drive for optical media with a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. The optical disc drive includes a first processor operable to communicate with a second processor, wherein the first processor includes instructions for performing non-time-critical tasks, and the second processor includes instructions for performing time-critical tasks, such as reading from and writing to optical media in the disc drive. The first processor monitors the status of the time critical tasks in the second processor and transmits commands to perform operations in the second processor. The first processor also controls power mode, manages recovery from errors, controls focus, tracking/seeking, spin, physical sector address (PSA), a laser, adjusts gains, and monitor cartridge load/eject.

Abstract: A method of changing the position of a component controlled by a servo system is disclosed. In accordance with the disclosed invention, the current position and the current control signal corresponding to the current position is determined. A target control signal corresponding to a target position is also determined. A smooth control signal profile is then calculated between the current control signal and the target control signal. The smooth control signal is then applied to move the component form the current position to the target position. In some embodiments, the smooth control signal can be, for example, a half-period sine wave with one extreme at the current control signal and the opposite extreme at the target control signal.

Abstract: A defect detector in an optical disk drive is presented. The defect detector indicates a defect by monitoring a sum signal. The sum signal is calculated from optical signals from detectors in an optical pick-up unit of the optical disk drive. A defect can be indicated when a filtered sum signal, the filtered sum signal being the sum signal filtered with a high pass filter, is above a threshold value. In some embodiments, the defect detector can recognize changes in laser power or transitions between media types and not indicate defects during those occurrences.

Abstract: A boundary crossing detector in a tracking and focus servo system of an optical disk drive is presented. A tracking error signal can be monitored as an optical pick-up unit of the optical disk drive is allowed to move across an optical media in the optical disk drive. If a peak-to-peak value of the tracking error signal changes by a threshold value, than the boundary crossing can be indicated.

Abstract: A system, method, and apparatus for coordinating tasks in a control system for an optical disc drive for optical media with a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. The optical disc drive includes a first processor operable to communicate with a second processor, wherein the first processor includes instructions for performing non-time-critical tasks, and the second processor includes instructions for performing time-critical tasks, such as reading from and writing to optical media in the disc drive. The first processor monitors the status of the time critical tasks in the second processor and transmits commands to perform operations in the second processor. The first processor also controls power mode, manages recovery from errors, controls focus, tracking/seeking, spin, physical sector address (PSA), a laser, adjusts gains, and monitor cartridge load/eject.

Abstract: A control system for controlling tracking and seeking in an optical disc drive for optical media with a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. The control system determines whether an optical pickup unit is over the premastered or the writeable areas of the optical media by measuring peak to peak amplitude of a tracking error signal. Gains and calibration values are selected based on whether an optical pickup unit is over the premastered or the writeable areas of the optical media. Reading from and writing to the optical media is disabled while jumping tracks. Control of jumping tracks on the optical media includes controlling: jumping a single track on the optical media; jumping a specified number of tracks every specified number of revolutions of the optical media; auto jumpbacks, and jumping in forward or reverse directions.

Abstract: A servo system with a multi-track seek algorithm is presented. The multi-track seek algorithm detects zero crossings in a tracking error signal, counts the number of zero crossings to form a count, and calculates a reference velocity from the count. The algorithm also determines a time period between successive zero crossings, calculates a velocity from the time period, calculates a difference signal between the reference velocity and the velocity, and adjusts the control signal so that the velocity follows the reference velocity. The reference velocity can follow a velocity profile with acceleration portions, coasting portions, and deceleration portions which move an optical pick-up unit from a starting position to a target position.

Abstract: A calibration of a loop gain in a digital servo system is presented. The loop gain can be calibrated measuring the response in a control signal generated by the digital servo system when the control signal is replaced by a sum of the control signal and a sinusoidal disturbance. The loop gain can be set to provide a desired gain, for example unity, between the control signal and the sinusoidal disturbance at a cross-over frequency.

Abstract: A notch filter that filters a focus error signal during a multi-track seek operation is presented. The notch filter has a center frequency that relates to the seek reference velocity of a multi-rack seek algorithm. During the multi-track seek operation, a focus control signal is calculated from the filtered focus error signal from the notch filter.

Abstract: A sample integrity test is disclosed. The sample integrity test receives an error signal and a defect signal. If the defect signal indicates the presence of a defect, a low-pass filtered error signal is substituted for the error signal. The low-pass filtered error signal is the error signal filtered with a low-pass filter. The error signal can be derived from optical signals from an optical pick-up unit. A control signal generated from the output signal from the sample integrity test controls the position of the optical pick-up unit. The defect signal can also be derived from the optical signals.

Abstract: A tracking servo system with a at least one second order digital filter is presented. The system calculates an error signal and offsets, amplifies, and filters the error signal before a l signal is calculated. The control signal is then utilized to position an optical pick-up unit provides signals from which the error signal is calculated. Filters in the servo system can e a low-pass integrator, a phase lead filter, notch filters, or other filters. At least one of the is a second order digital filter.

Abstract: A tracking servo system with a tracking skate detection algorithm is presented. The tracking skate detection algorithm receives a tracking error signal and, takes the absolute value of the tracking error signal and filters the absolute value with a low pass filter. If the filtered signal exceeds a threshold value for a number of cycles exceeding a maximum number, then a tracking skate condition is indicated.