Abstract: A differentiating qualifier channel in a hard disk drive. The analog signal read off a magnetic disk by the transducer is amplified and filtered, then immediately differentiated. This differentiated waveform is used to both qualify and to detect the peaks of the analog read signal. Data pulses are qualified by noting that the differentiated waveform always changes polarity after the zero-crossing of a valid peak. Positive and negative peak signals are generated whenever the differentiated waveform exceeds established positive and negative thresholds. From this, a polarity signal is constructed. The pulses indicating where the polarity signal changes states are used to enable a latch. The latch is clocked by a zero-crossings signal which has been delayed such that the zero-crossings occur after the change in polarity. The output from this latch gives the valid qualified data pulses.

Abstract: Many of the data read errors encountered in an optical disk system are due to reading off track. These errors are the result of bit shift, which is the shifting of the data transition relative to the center of the detection timing window. This bit shift is the result of the rounded edges of the data marks on the recording medium. A normal data signal is read off the recording medium while the read apparatus is centeed on the data storage track of the recording medium. If the read beam of the read apparatus moves off track radially to either side of the center of the data storage track, the detected data transitions move toward each other due to the rounded edges of the recorded data on the data storage track. This makes the data mark appear shorter and results in bit shift and increased error rate. The off-track bit shift compensation apparatus compensates for this misalignment and the resultant bit shift by dynamically adjusting the analog detection threshold of the read apparatus.

Abstract: A system and method for maintaining a prescribed track pitch in an optical storage system wherein a second radiation beam is aligned a desired distance from a first radiation beam, the first radiation beam being controllably steered to follow a previously written data track on a record carrier used within the optical storage system. A write alignment servo aligns the second radiation beam the prescribed distance from the first radiation beam in response to an offset signal. The offset signal is generated by optically measuring the distance between a pair of calibration tracks that have previously been placed on the disk so as to have the desired track pitch therebetween. The effect of variations or drift occurring in the optical or electrical components of either the write alignment servo or the optical track pitch measurement system is significantly reduced by regularly calibrating against the fixed track pitch of the calibration tracks.

Abstract: A system and method for optically measuring and maintaining track pitch in an optical storage system. A set of at least four calibration tracks, each having a prescribed track pitch or distance therebetween, are precisely placed on a record carrier of the optical storage system during the manufacture thereof. When this record carrier is subsequently inserted into the optical storage system, the track pitch of a select pair of the calibration tracks is optically measured, and an offset signal is generated in response to this measurement. This offset signal is used within the optical storage system for controllably positioning a second radiation beam with respect to a first radiation beam, the first radiation beam being directed to follow a previously written data track on the record carrier.

Abstract: A system and method for optically measuring and maintaining track pitch in an optical storage system. A set of at least four calibration tracks, each having a prescribed track pitch or distance therebetween, are precisely placed on a recording medium of the optical storage system during the manufacture thereof. When this recording medium is subsequently inserted into the optical storage system, the track pitch of a select pair of the calibration tracks is optically measured by maximizing the amplitude of a data read radiation beam, and an offset signal is generated in response to this measurement. This offset signal is used within the optical storage system for controllably positioning a second radiation beam with respect to a first radiation beam, the first radiation beam being directed to follow a previously written data track on the recording medium.

Abstract: An ink jet pump is switched from a mechanically off or idle state to a mechanically on or active state with no drift in pressure output by maintaining the pump at the same point in its force-temperature characteristic when it is on and off. This is accomplished by driving the pump in both the active and idle states with signals that dissipate the same amount of power in the pump. The frequency of the idle state signal is high enough that the pump can not mechanically respond. The power dissipations in the active and idle states are matched by adjusting the current build-up and current decay through the coil of the pump during the idle state. When the RMS current through the coil in the active state equals the RMS current in the idle state, the power dissipations are matched.