Optical Detection for TAR Patterned Media Servo and Sync
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Solution Overview
Problem
Magnetic recording disk drives with patterned media face challenges in achieving adequate signal-to-noise ratios for servo control and write synchronization without relying on magnetic readback from nondata regions, especially in high-density bit-patterned media where radiation absorption contrast is low.
Innovation Solution
A thermally-assisted recording (TAR) patterned-media magnetic recording disk drive uses optical detection of synchronization fields for write synchronization and optical detection of servo sectors for read/write head positioning, employing a near-field transducer to generate a power absorption profile with a characteristic spot size less than the gaps between nondata blocks, allowing a sensor to provide output signals for controlling the timing of the magnetic write field and positioning of the read/write head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic readback is used for servo control and write synchronization in patterned-media disk drives, then the system can achieve servo control functionality, but the signal-to-noise ratio becomes inadequate in high-density bit-patterned media
Solution Approach 1:
The patent replaces magnetic readback detection with optical detection for servo control and write synchronization. Specifically, it uses optical detection of synchronization fields and servo sectors through the disk surface, substituting the magnetic detection mechanism with an optical one to achieve adequate signal-to-noise ratios in high-density patterned media.
Solution Approach 2:
The patent introduces an intermediary detection mechanism by using optical fields as a mediator between the disk's nondata regions and the detection system. The optical detection system acts as an intermediary to read synchronization and servo information without relying on magnetic readback, thereby improving signal quality.
2Reliability
If nondata servo regions with discrete servo islands are used, then servo control can be implemented in patterned media, but the radiation absorption contrast becomes low in high-density media
Solution Approach 1:
The patent substitutes magnetic readback with optical detection for reading servo information. By using optical detection of the disk surface reflectivity or absorption characteristics, the system achieves adequate signal contrast for servo control without relying on magnetic field interactions that provide insufficient contrast in high-density media.
3Measurement precision
If optical detection is used for synchronization fields, then write synchronization can be achieved with improved signal-to-noise ratio, but additional optical components are required
Solution Approach 1:
The patent makes the optical detection system multi-functional by using the same optical detection mechanism for both write synchronization and servo control operations. This universal approach allows a single optical detection system to handle multiple functions, reducing the need for separate dedicated components for each function.
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 eliminates the need for magnetic readback, providing stable servo control and write synchronization with improved signal-to-noise ratios, even in high-density bit-patterned media, while optimizing storage overhead and maintaining thermal stability and writability of data islands.
Implementation Method 1
an optical waveguide with a near-field transducer (NFT) directs heat from a radiation source, such as a laser, to heat localized regions of the magnetic recording layer on the disk
Implementation Method 2
The radiation heats the magnetic material locally to near or above its Curie temperature to lower the coercivity enough for writing to occur by the write head
Implementation Method 3
A sensor provides an output signal in response to radiation from the nondata blocks and gaps in the synchronization fields and the servo sectors as the disk rotates
Implementation Method 4
The NFT generates a power absorption profile on the disk with a characteristic along-the-track spot size less than the along-the-track length of the gaps between the nondata blocks
Data Source
AI summary
A thermally-assisted recording (TAR) bit-patterned-media (BPM) magnetic recording disk drive uses optical detection of synchronization fields for write synchronization and optical detection of servo sectors for read/write head positioning. The synchronization fields and servo sectors extend generally radially across the data tracks and are patterned into discrete nondata blocks separated by gaps in the along-the-track direction. A near-field transducer (NFT) directs laser radiation to the disk and generates a power absorption profile on the disk that has a characteristic along-the-track spot size less than the along-the-track length of the gaps between the nondata blocks in the synchronization fields and servo sectors. A sensor provides an output signal in response to radiation from the nondata blocks and gaps in the synchronization fields and servo sectors as the disk rotates to control the timing of the magnetic write field applied to the data islands and to control the positioning of the read/write head on the data tracks.