Abstract: A system and method for dynamically re-calibrating an optical disc drive during operation is provided. The optical media includes a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. The system can attempt several increasing levels of effort to recalibrate the disc drive until the disc drive reaches a desired level of performance, or the recalibration effort levels are exhausted. During each level of recalibration effort, various calibration values are determined for the optical media and the servo actuator, along with a notch frequency for a notch filter; a focus actuator offset; a tracking actuator offset; a focus control loop gain; and a tracking control loop gain. The optical media disc is divided into zones, and zone calibration tables for each of the zones are generated. Each zone is recalibrated using the corresponding zone calibration table.

Abstract: A calibration for a tracking error signal offset in a tracking servo system of an optical disk drive is presented. In some embodiments, the tracking error signal offset is adjusted for best servo function by, for example, adjusting the center of a tracking error signal when the tracking servo system is open to zero. In some embodiments, the tracking error signal offset is adjusted for best read function by, for example, adjusting the tracking error signal offset until the data jitter is minimized. Data jitter can be determined by reading data from the optical media and measuring the data error rate.

Abstract: A system for determining whether a focus servo system is in focus or out of focus (i.e. open) is disclosed. A sum signal can be compared with a threshold value. If the sum signal is below the threshold value, then a focus open condition (i.e., out-of-focus) can be indicated. In some embodiments, a focus open condition is indicated where the sum signal remains below the threshold value for a predetermined period of time.

Abstract: A digital servo system of an optical disk drive with a calibrated inverse non-linearity function is disclosed. A look-up table is determined, for example, with a focus error signal gain corresponding with a focus error signal offset so that the response of the focus servo system is substantially linear. Additionally, the look-up table can include tracking error signal gain, tracking error signal offset, or tracking loop gain parameters corresponding with the focus error signal offset.

Abstract: A control system for an optical disc for optical media with a premastered area that cannot be overwritten and a user-writeable area that can be overwritten, comprises a first processor operable to communicate with a second processor via a status register. The first processor sequences and monitors functions performed in the second processor and the second processor issues an interrupt when an error condition is detected in the second processor. The first processor detects the interrupt, and disables detecting further interrupts until the interrupt is serviced. Servicing the interrupt includes recording the error state and changing focus and tracking parameters based on the error condition detected.

Abstract: A servo system that calibrates a cross-talk gain parameter in a tracking error signal to focus error signal crosstalk correction is provided. The cross-talk gain parameter can be optimized such that the effects of a perturbation applied to the tracking servo loop on an adjusted focus error signal, i.e. a focus error signal that has been corrected for crosstalk, is minimized. The optimized cross-talk gain, then, can be set to the cross-talk gain of a set of cross-talk gains that results in the lowest value of a frequency component of the adjusted focus error signal while a perturbation at the frequency is being applied to the tracking servo loop.

Abstract: A system and method for handling events issued as a result of error conditions in the operation of an optical disc drive include suspending processing of commanded operations in the disc drive while attempting to recover from the error condition. The recovery attempt can include increasing levels of recovery effort, such as dynamically recalibrating various components in the disc drive. The system can also determine whether a previous notice was received for the same error condition. If so, the system can determine whether excessive recovery attempts have been initiated based criteria such as the time between the notices, and/or the number of notices, for the same error condition. The recovery attempts are aborted when they become excessive. If the recovery attempt is successful, the interrupted operation is resumed at the point where the processing was suspended, such as during a write or read command.

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 calibration of input signal offset in an optical disk drive is presented. The input signal offsets the input signals received from an optical pick-up unit before digitization. In some embodiments, the input signal offset is set such that the digitized input signals are zero when laser power is off. Further, a thermal drift correction is presented.

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 head load algorithm for an optical disk drive is presented. On startup, the optical media can be spun up. Then an optical pick-up unit can be positioned at an extreme position, for example at the inner diameter, and focus can be closed. The optical pick-up unit then can be incrementally moved away from the extreme position while the tracking error signal is monitored to locate an area of the optical media with tracks. Once the area is located, a tracking servo system can close on one of the tracks.

Abstract: An anti-skate algorithm in a tracking servo system of an optical disk drive is described. The anti-skate algorithm prevents skating during close of the tracking servo system by allowing the tracking servo system to close on a tracking error signal with an appropriate slope.

Abstract: A servo system with a multi-track seek algorithm with a zero crossing detector is presented. The zero crossing detector indicates when the tracking error signal crosses zero. In some embodiments, a delay is executed between adjacent detections of zero crossings in the tracking error signal, for example half a cycle. In some embodiments, a zero crossing is detected when the tracking error signal passes through a range around zero, the range having a positive value above zero and a negative value below zero.

Abstract: A calibration for a tracking error signal gain in a tracking servo system of an optical disk drive is presented. The calibration determines the peak-to-peak tracking error signal when the tracking servo system is open, calculates a gain factor in response to the peak-to-peak tracking error signal, and calculates a new tracking error signal gain based on the tracking error signal gain and the gain factor. New tracking error signal gains are calculated until the gain factor is approximately one.

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 close tracking algorithm for a tracking servo system is disclosed. The track crossing rate of an optical pick-up unit positioned over an optical media is determined. When the track crossing rate is below a threshold value, then a tracking servo algorithm is enabled. The tracking servo algorithm provides control signals to control an actuator arm that controls the position of the optical pick-up unit over the tracks of the optical media. In some embodiments, the track crossing rate can be determined by monitoring the zero crossings of a tracking error signal derived from optical signals measured in the optical pick-up unit.

Abstract: A media type detector in a tracking and focus servo system is presented. Operating parameters for a first media type are loaded and a peak-to-peak value of a tracking error signal is calculated. Whether the media type is the first media or a second media can then be determined by comparing the peak-to-peak value with a threshold value.

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

Abstract: A system, method, and apparatus for recovering from performance errors in an optical disc drive is provided for optical media with a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. The system includes instructions operable to detect a problem with at least one of: focus control, tracking control, or spin control when accessing the optical media; instructions operable to save the current state of the disc drive; instructions operable to attempt to recover from the problem; and instructions operable to restore the current state of the disc drive after recovering from the problem.

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.