HAMR Laser Calibration for Fly Height Control
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Solution Overview
Problem
Data storage devices face challenges in maintaining accurate head positioning and data quality due to variations in fly height and environmental conditions, which affect the efficacy of laser heating and magnetic recording processes.
Innovation Solution
A calibration procedure is implemented using test data and varying calibration powers to generate metrics, allowing for adjustment of the control signal applied to the fly height actuator and write power to maintain a target fly height and data track quality, ensuring accurate head positioning and data recording.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser heating power is increased to improve data recording quality, then data track quality is improved, but head contact with disk surface increases causing damage
Solution Approach 1:
The system continuously monitors write signal metrics during laser heating and uses this feedback to dynamically adjust laser power. When the metric indicates the head is approaching the disk surface, the laser power is reduced, preventing contact while maintaining optimal heating for data recording quality.
Solution Approach 2:
The system changes the laser heating power parameter dynamically based on real-time conditions. By adjusting the laser power level according to the measured write signal metrics, the system optimizes data track quality while avoiding excessive heating that would cause head-disk contact.
2Manufacturing precision
If laser heating power is increased to improve data recording quality, then data track quality is improved, but fly height control accuracy decreases
Solution Approach 1:
The system uses write signal metrics as feedback to monitor fly height conditions. By analyzing changes in the write signal characteristics, the system can detect fly height deviations and adjust laser power accordingly, maintaining both data quality and positioning accuracy.
Solution Approach 2:
The system transitions from static laser power settings to dynamic power adjustment. The laser heating power is continuously adapted based on real-time fly height measurements derived from write signal metrics, allowing optimal performance across varying operating conditions.
3Measurement precision
If calibration power is applied for extended interval to ensure head contacts disk, then measurement accuracy is improved, but risk of head damage increases
Solution Approach 1:
The system applies calibration power at a level that is sufficient to produce measurable effects but not so high as to cause harmful head contact. By using partial power levels optimized for measurement rather than maximum power, the system achieves accurate calibration without excessive damage risk.
Solution Approach 2:
The calibration procedure is executed quickly and efficiently, obtaining accurate measurements without prolonged exposure to high calibration power. By rushing through the calibration process, the system minimizes the time the head is subjected to elevated power levels, reducing cumulative damage risk.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy and quality of data recording by maintaining optimal fly height and data track density, even under varying environmental conditions, thereby improving the overall performance of data storage devices.
Implementation Method 1
Heat assisted magnetic recording (HAMR) is a recent development that improves the quality of written data by heating the disk surface with a laser during write operations in order to decrease the coercivity of the magnetic medium
Implementation Method 2
heating the disk surface with a laser during write operations in order to decrease the coercivity of the magnetic medium
Implementation Method 3
enabling the magnetic field generated by the write coil to more readily magnetize the disk surface
Implementation Method 4
magnetize the disk surface
Implementation Method 5
the magnetic transitions are sensed by a read element (e.g., a magnetoresistive element)
Data Source
AI summary
A data storage device is disclosed comprising a head actuated over a disk, wherein the head comprises a laser configured to heat the disk while writing data to the disk. A write power for the laser is calibrated, wherein the write power is applied to the laser while writing user data to the disk. A calibration power is applied to the laser for a first interval, wherein the calibration power is high enough to cause the head to contact the disk if applied for a second interval longer than the first interval. While applying the calibration power to the laser, test data is written to the disk during at least part of the first interval. The test data is read from the disk to generate a read signal, and a metric is generated based on the read signal.