Patterned-Media Disk Optical Contrast for Write Clock Synchronization
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Solution Overview
Problem
Magnetic recording disk drives with patterned media face challenges in generating a reliable write clock signal due to the small difference in reflected radiation power between data islands and nonmagnetic spaces, making precise synchronization of write pulses difficult.
Innovation Solution
Incorporating optical contrast materials such as optically absorptive, fluorescent, or metal layers in the nonmagnetic spaces between data islands to enhance the contrast in reflected radiation power, allowing for improved detection by a near-field transducer and subsequent generation of a more reliable write clock signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If patterned media with data islands and nonmagnetic spaces is used, then data density is increased, but the contrast in reflected radiation power between islands and spaces becomes too small for reliable write clock signal generation
Solution Approach 1:
The patent applies local quality by introducing optical contrast materials specifically in the nonmagnetic spaces between data islands, rather than uniformly across the entire media. This localized modification enhances the optical contrast only where needed (in the spaces) without affecting the magnetic recording properties of the islands, thereby resolving the contradiction between maintaining high data density and achieving sufficient reflected radiation contrast for reliable detection.
Solution Approach 2:
The patent utilizes color changes by employing optical contrast materials that differ in optical properties (absorptivity, fluorescence, or plasmon generation) from the data islands. These materials alter the reflected radiation characteristics - either by absorbing light, emitting fluorescence, or generating surface plasmons - creating detectable optical contrast between islands and spaces that enables reliable write clock signal generation while preserving the high-density patterned structure.
2Measurement precision
If optical contrast materials are added to nonmagnetic spaces, then reflected radiation power contrast is enhanced, but device complexity increases
Solution Approach 1:
The patent employs composite materials by combining the base nonmagnetic space material with optical contrast materials. This composite approach allows the nonmagnetic spaces to maintain their magnetic isolation function while simultaneously providing enhanced optical contrast through the added material properties. The composite structure integrates multiple functions (magnetic isolation and optical contrast) within a unified material system, enhancing measurement precision without proportionally increasing device complexity.
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
The enhanced contrast in reflected radiation power enables more accurate synchronization of write pulses with the data islands, improving the precision and reliability of data writing in patterned-media magnetic recording disk drives.
Implementation Method 1
the optical contrast material in the spaces is optically absorptive material
Implementation Method 2
the optical contrast material in the spaces is fluorescent material, like fluorescent dyes and semiconductor nanocrystals, that emits radiation when excited by radiation of a specific wavelength
Implementation Method 3
the optical contrast material in the spaces is a metal layer that generates surface plasmons when excited by radiation of a specific wavelength
Implementation Method 4
A radiation detector detects radiation reflected back from the transducer and its output signal represents the variation in reflected radiation when the transducer is near an island or a space
Data Source
AI summary
A patterned-media magnetic recording disk drive uses an optical system for clocking the write data and a patterned-media disk that has discrete magnetizable data islands with nonmagnetic spaces between the islands, wherein the nonmagnetic spaces contain optical contrast material. The optical contrast material may be optically absorptive material, fluorescent material, or a metal layer that generates surface plasmons when excited by radiation of a specific wavelength. Radiation from a primary radiation source is directed to a near-field transducer maintained near the disk surface and a radiation detector detects radiation reflected back from the transducer. If the disk has fluorescent material or a metal layer in the nonmagnetic spaces, then a secondary radiation source irradiates the fluorescent material or metal layer with radiation of a specific wavelength to cause the fluorescent material to emit radiation or the metal layer to generate surface plasmons. As the disk rotates, reflected optical power from the transducer varies depending on whether an island or space is under the transducer. The output signal from the radiation detector output controls the write clock.