HAMR Thermal Sensor Bandwidth via Waveform Calibration
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Solution Overview
Problem
The optical power fluctuations in heat-assisted magnetic recording (HAMR) devices affect recording quality and reliability due to mode hopping, operation temperature drift, and aging, necessitating improved monitoring and control methods.
Innovation Solution
Enhancing thermal sensor bandwidth through advanced electrical detection techniques, including calibration and real-time waveform data updates, and maintaining the thermal sensor at a predetermined temperature to ensure steady-state operation and fast response times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thermal sensor operates in conventional mode, then the sensor structure is simple, but the response time is limited by the thermal sensor rise time to steady state
Solution Approach 1:
The system performs preliminary calibration to obtain calibration waveform data before actual operation. This pre-characterization of the thermal sensor's response allows the system to compensate for the inherent slow response time by comparing real-time measurements against the known calibration profile, effectively extending the usable bandwidth without modifying the physical sensor structure.
Solution Approach 2:
The patent introduces an intermediary processing system that includes a lookup table storing calibration data and a controller that performs real-time comparison and compensation. This intermediary layer between the thermal sensor and the control system enables fast response by using pre-computed calibration data rather than waiting for the thermal sensor to reach steady state naturally.
2Measurement precision
If optical power monitoring is implemented using conventional methods, then the system structure is simple, but the monitoring precision and control accuracy are insufficient
Solution Approach 1:
The system implements a feedback control mechanism where the thermal sensor continuously monitors optical power, the controller compares measurements against calibration data, and adjusts the laser diode current accordingly. This closed-loop feedback system achieves high precision monitoring and control by continuously compensating for optical power variations caused by mode hopping, temperature drift, and aging.
Solution Approach 2:
The patent replaces conventional optical power monitoring methods with an electrical detection approach using a thermal sensor that converts optical power variations into electrical resistance changes. This substitution of optical detection with electrical measurement enables more precise and stable monitoring while simplifying the overall system architecture.
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 allows for precise monitoring and control of optical power, enhancing the recording quality, reliability, and extending the lifespan of HAMR devices by overcoming limitations in thermal sensor response time and bandwidth.
Implementation Method 1
The optical power in the light delivery path of HAMR heads affects the heating temperature profile... Monitoring and controlling this optical power can improve HAMR recording quality
Implementation Method 2
Heating of the media surface has been accomplished by a number of techniques such as focused laser beams... optical power from a laser diode (LD)
Implementation Method 3
measuring and tracking a resistance value of the thermal sensor... obtaining calibration waveform data for a resistance of the thermal sensor
Data Source
AI summary
Embodiments disclosed herein generally relate to a method for monitoring optical power in a HAMR device. In one embodiment, the method includes enhancing a thermal sensor bandwidth through advanced electrical detection techniques. The advanced electrical detection techniques include obtaining calibration waveform data for a thermal sensor by calibrating the thermal sensor, obtaining real-time waveform data for the thermal sensor that may deviate from the calibration waveform data, updating the calibration waveform data to include the real-time waveform data, repeating obtaining real-time waveform data and updating the calibration waveform data during writing operations. By updating the calibration waveform data, the bandwidth of the thermal sensor is determined by a fixed sampling time interval, and the thermal sensor rise time to steady state would not be a limitation to its response time.