Patterned Media Disk Drive Misplacement Compensation
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Solution Overview
Problem
Magnetic recording disk drives with patterned media face challenges in accurately positioning data islands due to misplacement caused by drifts and offsets in e-beam lithography systems and self-assembled block copolymers, leading to misalignment of data tracks and islands.
Innovation Solution
Incorporating servo sectors on the disk that record misplacement information, allowing for correction of the radial position and timing of the write head, and inhibition of write pulses to defective islands, using iterative processes to measure and store misplacement data for precise alignment and synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If e-beam lithography or self-assembled block copolymers are used to create master templates for nanoimprinting, then data island patterns can be formed on disks, but drifts and offsets in the e-beam machine or block copolymer expansion/contraction cause misplacement of data islands and data tracks
Solution Approach 1:
The patent performs preliminary measurement of data island positions during the manufacturing process and stores this misplacement information in servo sectors before the disks are put into service. This advance preparation allows the system to compensate for manufacturing errors without requiring perfect placement accuracy during operation.
Solution Approach 2:
The patent implements a feedback mechanism where misplacement information measured during manufacturing is stored in servo sectors and later read during disk operation. This feedback loop enables the system to adjust write head positioning and timing based on actual measured deviations from the ideal pattern, compensating for manufacturing errors.
2Reliability
If data islands are precisely positioned to ensure synchronized write pulses, then data storage reliability is improved, but any misplacement in the manufacturing process leads to desynchronization and increased bit error rates
Solution Approach 1:
The patent measures and records misplacement information during the manufacturing process as a preliminary action. This stored information serves as a reference that enables subsequent compensation during disk operation, ensuring reliable data storage even when manufacturing precision is not perfect.
Solution Approach 2:
The patent uses feedback from measured misplacement data to adjust write head positioning and pulse timing during operation. By reading the stored misplacement information from servo sectors and using it to correct synchronization errors, the system maintains high reliability despite manufacturing variations.
3Manufacturing precision
If misplacement information is stored in servo sectors to enable correction, then alignment precision is improved, but the device complexity increases due to additional servo sector structure and correction processing
Solution Approach 1:
The patent merges the misplacement information storage function into the existing servo sector structure. By combining alignment correction data with the conventional servo sector content, the patent avoids adding separate dedicated storage structures, thereby limiting the increase in device complexity while still achieving improved alignment precision.
Data Source
AI summary
A disk drive with patterned-media disks has information recorded in the servo sectors that identifies misplacement of the data islands in the data regions between the servo sectors. This misplacement information is read from the servo sectors prior to writing to correct either or both the radial position of the write head and the timing of the write pulses to the data islands. The misplacement information may include radial deviation of the data tracks, circumferential or along-the-track misplacement of the data islands, or the location of defective data islands.