Optical Waveguide Near-Field Transducer for Patterned Media Clocking
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Solution Overview
Problem
Magnetic recording disk drives with patterned media face challenges in accurately writing data to discrete magnetizable data islands due to the need for precise synchronization of write pulses with the patterned media, requiring a method to detect data islands and generate an accurate write-clock signal.
Innovation Solution
A system using an optical waveguide with a near-field transducer on the slider directs radiation to and receives reflected radiation from the disk, with a radiation detector providing a signal that controls the write clock, synchronized by a phase-locked-loop to match the frequency and phase of the data islands, and adjusted for physical spacing between the write head and transducer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If patterned media with discrete data islands is used to increase data density, then storage capacity is improved, but precise synchronization of write pulses with data islands becomes necessary
Solution Approach 1:
The patent applies preliminary action by using a separate sensing element to detect the position of data islands before the write head reaches them. The sense/write skew allows the sensing element to be positioned ahead of the write pole, enabling early detection of island positions and generation of write clock signals in advance, which are then synchronized with the write pulses through a phase-locked loop.
Solution Approach 2:
The patent introduces an intermediary sensing element that acts as a mediator between the data islands and the write head. This sense element detects the magnetic transitions of data islands and generates signals that are processed through a phase-locked loop to control the timing of write pulses, ensuring precise synchronization without requiring direct positioning control of the write head.
2Manufacturing precision
If the media is patterned perfectly with a single accurate period to ensure write head alignment, then write accuracy is improved, but manufacturing complexity increases
Solution Approach 1:
The patent implements feedback by using the sensing element to continuously monitor the actual position of data islands during disk rotation. The detected island positions are fed back through a phase-locked loop that adjusts the write clock signal in real-time, compensating for any variations in media patterning or spindle speed without requiring perfect initial manufacturing precision.
Solution Approach 2:
The patent applies dynamics by making the write clock signal dynamically adjustable through a phase-locked loop. Instead of relying on static, perfectly precise media patterning, the system dynamically synchronizes the write pulses to the actual position of data islands as they pass under the write head, adapting to real-time variations in media position and spindle speed.
3Manufacturing precision
If the spindle speed is made highly stable to synchronize write clock with data islands, then write synchronization is improved, but motor control complexity increases
Solution Approach 1:
The patent applies self-service by allowing the system to self-synchronize through the phase-locked loop that automatically adjusts the write clock frequency and phase based on the detected position of data islands. The sensing element and PLL circuitry automatically compensate for spindle speed variations without requiring complex external control mechanisms, making the system self-correcting.
4Manufacturing precision
If a pattern-sensor is used to detect data islands and generate write-clock signal, then write accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the sensing and writing functions into a single integrated head assembly. The sense element and write pole are positioned close together on the same slider, sharing the same positioning and control infrastructure. This integration reduces the overall system complexity compared to having completely separate sensing and writing subsystems, while still achieving precise synchronization through the combined sense/write skew arrangement.
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 solution ensures accurate writing of data to patterned media by synchronizing write pulses with the location of data islands, improving data integrity and density in magnetic recording disk drives.
Implementation Method 1
The optical waveguide has a near-field transducer at the disk-facing surface of the slider where the radiation exits and reflected radiation returns
Implementation Method 2
a radiation detector receives reflected radiation from the near-field transducer
Implementation Method 3
The write clock signal that controls write pulses to the write head is responsive to the radiation detector output signal, so the frequency and phase of the write clock signal can be matched to the frequency and phase of the islands as the disk rotates
Implementation Method 4
magnetic recording disk drives with patterned media, wherein each data bit is stored in a magnetically isolated island
Data Source
AI summary
A patterned-media magnetic recording disk drive uses an optical system for accurately clocking the write data. The disk has concentric data tracks patterned into discrete magnetizable data islands with nonmagnetic spaces between the islands. As the disk rotates, a radiation source directs near-field radiation to the islands and spaces, and a radiation detector receives reflected radiation. The radiation is directed from the source through an optical channel or waveguide on the air-bearing slider that supports the read and write heads. The optical channel or waveguide has a near-field transducer at the disk-facing surface of the slider where the near-field radiation exits and reflected radiation returns. The reflected optical power varies depending on whether the near-field transducer couples to an island or a space, so the radiation detector output signal represents the frequency and phase of the islands as the disk rotates. The write clock that controls write pulses to the write head is responsive to the radiation detector output signal, so the frequency and phase of the write clock signal can be matched to the frequency and phase of the islands as the disk rotates.