Laser Diode Current Calibration via Temperature Compensation Equation
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Solution Overview
Problem
Heat-assisted magnetic recording (HAMR) disk drives face challenges in accurately adjusting laser diode currents across varying operating temperatures, leading to suboptimal data recording due to non-linear changes in current requirements with temperature.
Innovation Solution
A temperature compensation equation is generated during manufacturing using initial operating currents and efficiency values at different temperatures, allowing for an updated compensation factor to be calculated during field operation, which adjusts the current supplied to the laser diode for optimal write operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed laser diode current is used for data recording, then device complexity is reduced, but recording reliability deteriorates due to temperature variations
Solution Approach 1:
The patent performs preliminary calibration during manufacturing by measuring laser diode output at multiple temperatures and storing the data in a lookup table. This preliminary action enables accurate current adjustment during actual operation without requiring complex real-time measurement systems, thus improving recording reliability while controlling device complexity.
Solution Approach 2:
The patent implements feedback by using a temperature sensor to continuously monitor the drive temperature and comparing it against stored calibration data. The controller adjusts the laser diode current based on this feedback to maintain optimal recording conditions across temperature variations, improving reliability without excessive complexity.
2Measurement precision
If laser diode current is adjusted for each temperature, then recording precision is improved, but manufacturing complexity increases
Solution Approach 1:
The patent performs all necessary calibration measurements during manufacturing by testing the laser diode at multiple predetermined temperatures and storing the corresponding output values in a lookup table. This preliminary action captures the temperature-dependent characteristics once, enabling precise current adjustment during operation without requiring complex real-time calibration procedures, thus improving measurement precision while maintaining ease of manufacture.
3Productivity
If temperature compensation is implemented, then data recording efficiency is improved, but device complexity increases
Solution Approach 1:
The patent performs preliminary calibration during manufacturing by measuring laser diode output at multiple temperatures and storing the data in a lookup table. This preliminary action enables efficient temperature compensation during operation without requiring complex real-time measurement and calculation systems, thus improving data recording efficiency while controlling device complexity.
Solution Approach 2:
The patent creates a copy of the temperature-dependent laser characteristics in the form of a lookup table stored in non-volatile memory. This copied data allows the controller to quickly determine the appropriate current adjustment based on temperature without performing complex calculations in real-time, improving recording efficiency while minimizing the increase in device complexity.
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 enables precise adjustment of laser diode currents across the full range of operating temperatures, improving data recording efficiency and maintaining consistent performance despite temperature variations.
Implementation Method 1
a laser diode (102) located on an input surface (103) of a slider body (101)... for heating a region of the magnetic recording medium
Implementation Method 2
An optical waveguide (110) may be mounted to the slider body (101)... The waveguide (110) may be configured to transmit the light from the laser (102) to the near-field transducer (112)
Implementation Method 3
a near-field transducer (112) configured to heat a region of the magnetic recording medium... The near-field transducer (112) may be configured to convert the light to heat the region of the magnetic recording medium
Implementation Method 4
A temperature sensor is disposed in the disk drive and is configured to measure an operating temperature or a value proportional to the operating temperature
Data Source
AI summary
A method includes generating, during manufacture of a heat-assisted magnetic recording (HAMR) disk drive, a temperature compensation equation for a compensation factor using initial operating currents supplied to a laser diode of the disk drive at different initial operating temperatures and an efficiency value based on the initial operating temperatures. The operating currents are representative of currents for recording data to or erasing data from a magnetic recording medium. The temperature compensation equation is stored in the disk drive. A subsequent efficiency value is determined based on at least one of the initial operating temperatures and an operating temperature differing from the initial operating temperatures. An updated compensation factor at the operating temperature is determined during field operation using the temperature compensation equation and the subsequent efficiency value. An updated operating current is calculated using the updated compensation factor and the operating temperature. A current supplied to the laser diode for a subsequent write operation is adjusted to the updated operating current.