HAMR Laser Power Calibration via Write Quality Function
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Solution Overview
Problem
In heat-assisted magnetic recording (HAMR) technologies, optimizing laser power for calibration is crucial to prevent damage to optical components and ensure efficient data recording, but existing methods are time-consuming and lack a clear method to set a safe maximum laser power, especially during field recalibrations due to aging of components.
Innovation Solution
A method involving selecting an operational laser power based on a previously measured function of write quality metric versus laser power, determining a power difference, and setting a maximum laser power for calibration to ensure improved write quality without exceeding safe limits, allowing for efficient recalibration within defined power ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a traditional laser calibration method is used to ensure optimal write quality, then data recording quality is improved, but calibration time increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-determining a maximum laser power value based on previously measured functions before performing calibration. The controller uses historical calibration data to establish an upper power limit, allowing the calibration process to operate within predefined bounds rather than exploring the full power range, thus reducing calibration time while maintaining write quality optimization
Solution Approach 2:
The patent changes the parameter space for calibration by constraining the laser power range using a maximum power value derived from previous measurements. Instead of calibrating across all possible power levels, the system adjusts power only within the range from minimum to maximum predetermined values, reducing the search space and calibration time while still finding optimal settings
2Manufacturing precision
If higher laser power is used during calibration to improve write quality, then recording quality improves, but risk of damage to optical components increases
Solution Approach 1:
The patent applies beforehand cushioning by pre-establishing a maximum laser power value based on previously measured functions before calibration begins. This predetermined maximum acts as a protective cushion that prevents the calibration process from applying excessive power that could damage optical components, while still allowing sufficient power range to achieve optimal write quality
Solution Approach 2:
The maximum laser power value serves as an intermediary between the desired high power for quality optimization and the safety limit to prevent damage. The controller uses this intermediate maximum power value to guide calibration, ensuring power stays within safe bounds while still enabling quality optimization
3Reliability
If laser power is reduced to prevent component damage, then safety is improved, but write quality may deteriorate
Solution Approach 1:
The patent optimizes the power parameter range by setting maximum power based on previously measured functions. This dynamic parameter adjustment ensures the calibration uses the highest safe power levels determined by historical data, preventing both component damage and quality deterioration by finding the optimal power boundary
4Productivity
If a predetermined maximum laser power is used for calibration, then calibration time is reduced and safety is improved, but flexibility in finding optimal power is limited
Solution Approach 1:
The patent applies dynamics by making the maximum power value adaptive rather than fixed. The maximum power is determined dynamically from previously measured functions specific to each recording head and medium combination, allowing the system to adapt to different conditions while still providing predetermined bounds for efficient calibration
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 reduces the time required for laser calibration, prevents damage to optical components, and maintains optimal data recording quality by dynamically adjusting laser power based on previous calibration data, improving the reliability and availability of data storage devices.
Implementation Method 1
heat-assisted magnetic recording (HAMR) technologies
Implementation Method 2
a laser to create a small hotspot on a magnetic disk during recording. The heat lowers magnetic coercivity at the hotspot
Implementation Method 3
uses an energy source such as a laser to create a small hotspot on a magnetic disk during recording
Implementation Method 4
The heat lowers magnetic coercivity at the hotspot, allowing a write transducer to change magnetic orientation
Data Source
AI summary
An operational laser power for a heat-assisted, magnetic recording head is selected based on a function of a write quality metric versus laser power. The write quality metric of data written to a magnetic recording medium is monitored at the operational laser power. Responsive to the write quality metric satisfying a threshold, a power difference between the operational laser power and an offset laser power is determined. The offset laser power corresponds to a point of the function where the write quality metric is approximately equal to the threshold. A maximum laser power is set for a calibration operation. The maximum laser power is based on the sum of the operational laser power and the power difference.