Edge detection for servo signals in optical storage system
AssigneeTerastor Corporation
InventorYung-Chieh Hsieh
Life of this patent
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Abstract
An edge detection system for detecting pre-formatted marks on a disk surface using reflected beams of optical signals. The detector include at least two separate sensing areas to analyze the energy distribution of the reflected beam to generate an edge detecting signal.
Claims14
An edge detection system for detecting a pre-formatted mark on a disk surface by detecting a beam reflected from the disk surface, comprising:
- an optical head configured to provide evanescent coupling for operation under a near-field configuration, where a spacing variation between the head and the disk surface is high, by receiving and focusing the beam onto the disk surface at a distance less than one wavelength of said beam;
- a light detector operatively coupled with said optical head to receive the reflected beam, said light detector having a first input element that receives a first spatial half of a reflected beam from the disk surface having pre-formatted marks to produce a first signal, and a second input element that receives a second spatial half of said reflected beam to produce a second signal;
- and
- an edge detection analyzer coupled to said first and second input elements to produce a difference of said first and second signals to indicate a location with respect to a pre-formatted mark on the disk surface, where the difference of said first and second signals substantially reduce the dependence of so generated edge signal on said spacing variation.
An optical disk drive system configured to illuminate a storage media of a patterned substrate surface with an optical beam, comprising:
- an optical head to couple an optical beam onto a storage media surface at least in part by evanescent waves through an air gap of less than about one wavelength;
- a servo detector disposed to receive a reflected beam from the storage media through said optical head and configured to have a plurality of light-sensing segments, each light-sensing segment detecting a different spatial portion of said reflected beam and generating a signal;
- and
- an edge detection analyzer operatively coupled to said servo detector and configured to operate on said signals from said plurality of light-sensing segments to generate an edge detection signal to indicate pre-formatted marks according to a spatial difference in energy distribution between two halves across the reflected beam.
The system of claim wherein said optical head includes a tapered optical fiber, a solid immersion mirror, or a flying laser that couples optical energy to and from said storage media.
A method for detecting pre-formatted marks on a storage media the method comprising:
- coupling a laser beam onto said storage media through an optical head, wherein an air-gap between said optical head and said storage media is less than one wavelength of said laser beam to obtain a tightly focused beam spot at least in part by evanescent waves;
- detecting a reflected beam from said storage media through said optical head by spatially separating said reflected beam separated into segments;
- summing said segments into two halves of said reflected beam from two identical light-sensing areas symmetrically arranged relative to each other along a line substantially perpendicular to images of tracking grooves in said reflected beam;
- and
- using a difference between signals from the two identical light-sensing areas to indicate an absence or presence of said pre-formatted marks on said storage media and to substantially reduce noise common to the signals from the two light-sensing areas.
Dependencies are inferred from the claim text.