Magnetic Index Mark Bias Point Offset for Bit Patterned Media
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Solution Overview
Problem
In bit patterned media (BPM) stacks, the eccentricity between the physical center of rotation and the pattern center leads to run-out issues, causing the read-write head to cross over multiple tracks due to wobbling, resulting in read and write errors.
Innovation Solution
A method for fabricating an orientation control bias point using a magnetic index mark (MIM) is introduced, which creates a bias point offset from the physical center to a virtual center of rotation, allowing the read-write head to be positioned accurately within a single track, eliminating run-out by aligning both sides of the BPM template concentrically and imprinting them simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the read-write head follows the physical center of rotation, then the head positioning is simple, but track run-out occurs due to eccentricity between physical center and pattern center
Solution Approach 1:
The patent pre-determines the bias point offset coordinates during the imprinting process, storing the correction data in advance. This preliminary action allows the system to compensate for eccentricity before actual data reading/writing occurs, eliminating track run-out while maintaining simple head positioning operations.
Solution Approach 2:
The patent changes the reference parameter from the physical center of rotation to a bias point with offset coordinates. By modifying the reference parameter used for head positioning, the system accounts for the eccentricity between physical and pattern centers, preventing track run-out without complicating the positioning mechanism.
2Ease of manufacture
If the BPM pattern is imprinted without bias point offset, then the imprinting process is simple, but run-out errors occur causing head to cross multiple tracks
Solution Approach 1:
The bias point offset coordinates are determined and stored during the imprinting process itself, before actual data operations. This preliminary determination of correction parameters maintains simple imprinting procedures while ensuring reliable data recording by pre-compensating for eccentricity.
Solution Approach 2:
The system incorporates feedback by using the determined bias point offset coordinates to adjust head positioning during data operations. This feedback mechanism ensures that the head remains accurately positioned on the intended track, preventing run-out errors and improving data recording reliability.
3Manufacturing precision
If the read-write head is repositioned to compensate for eccentricity in real-time, then track accuracy is improved, but system complexity and operation time increase
Solution Approach 1:
Instead of real-time repositioning, the patent determines the bias point offset coordinates in advance during imprinting and stores them for later use. This preliminary determination eliminates the need for complex real-time calculations and repositioning mechanisms, maintaining simple system architecture while achieving accurate track positioning.
Solution Approach 2:
The patent creates a coordinate reference copy (bias point offset coordinates) that represents the eccentricity correction information. This copied reference data is stored and reused during operations, eliminating the need for complex real-time measurement and adjustment systems while maintaining positioning accuracy.
Data Source
AI summary
The embodiments disclose an orientation control bias point coupled to a magnetic index mark and having a bias point offset set at predetermined coordinates configured to substantially prevent concentricity run-out.