Servo Pattern Writing Junction Calculation
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Solution Overview
Problem
Conventional servo pattern writing methods using STW suffer from positioning accuracy deterioration due to side fringes and backlash issues, leading to increased writing time and reduced storage capacity, especially when writing servo patterns from both directions.
Innovation Solution
A method involving a temporary pattern written on the medium, allowing the head to move from the innermost to the outermost circumference while controlling its position, calculating a junction, and writing the servo pattern from both directions to this junction to prevent redundancy and backlash effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If servo pattern is written from both directions to reduce side fringes, then positioning accuracy is improved, but backlash causes incorrect joining of patterns and generates unwriteable areas
Solution Approach 1:
A temporary pattern is written in advance on the medium before the actual servo pattern writing. This temporary pattern serves as a reference for head position control during the servo pattern writing process, enabling accurate head positioning even when writing from both directions and preventing backlash-related joining errors.
Solution Approach 2:
The temporary pattern acts as an intermediary element between the head actuator system and the servo pattern writing process. By using the temporary pattern for head position control, the system mediates the backlash issue, allowing the head to be accurately positioned relative to the medium regardless of mechanical play in the actuator system.
2Reliability
If single direction writing method is used, then backlash is avoided, but side fringes are mixed in outer and inner circumference portions deteriorating read signal quality
Solution Approach 1:
The temporary pattern is written in advance to establish a reference framework before servo pattern writing. This allows the system to use bidirectional writing (improving read signal quality by reducing side fringes) while maintaining positioning accuracy through reference to the pre-written temporary pattern, rather than relying solely on single-direction writing.
Solution Approach 2:
The temporary pattern provides a feedback reference for head position control during servo pattern writing. By continuously referencing the temporary pattern, the system can detect and correct positioning deviations caused by backlash, enabling accurate bidirectional writing that improves read signal quality.
3Productivity
If both direction writing is used to improve read signal quality, then writing time is reduced, but storage capacity is reduced due to unwriteable areas and redundant patterns
Solution Approach 1:
The temporary pattern is written in advance in areas that will later contain servo patterns. This preliminary action enables the system to write servo patterns from both directions without creating unwriteable areas, as the temporary pattern provides continuous reference guidance. This eliminates the need to leave gaps in the servo pattern coverage, maximizing storage capacity while maintaining the speed benefits of bidirectional writing.
Solution Approach 2:
The temporary pattern is discarded (erased or overwritten) after serving its purpose as a reference during servo pattern writing. This allows the areas where the temporary pattern was written to be fully utilized for servo patterns, recovering the storage capacity that would otherwise be lost to unwriteable areas or redundant patterns.
Data Source
AI summary
According to one embodiment, a servo pattern writing method includes: moving a head from a first one of innermost and outermost circumferences of a medium to the remainder other than the first one while controlling a position of the head in accordance with a temporary pattern preliminarily written on the medium; calculating a junction between a servo pattern to be written from the innermost circumference and a servo pattern to be written from the outermost circumference based on a movement distance of the head; first writing the servo pattern from a second one of the innermost and outermost circumferences to the junction, while controlling the position of the head in accordance with the temporary pattern; and second writing the servo pattern from the remainder other than the second one to the junction, while controlling the position of the head in accordance with the temporary pattern.