# US 7,609,469 B2 · Alternative sensors for tracking and timing in bit patterned media

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- Number: US 7,609,469 B2
- Document ID: US7609469B2
- Status: Granted
- Kind: B2
- Application number: 11/770,873
- Filed: 2007-06-29
- Published: 2009-01-01
- Granted: 2009-10-27
- Earliest claimed: 2007-06-29
- Assignees: Seagate Technology LLC
- Inventors: Edward Charles Gage; Venkata Sailaja Chilaka; Chubing Peng; Mark Edward Re
- Web page: https://patentgrep.com/patent/US7609469B2

## CPC

- G11B 5/59677: {with optical servo tracking}
- B82Y 10/00: Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
- G11B 5/02: Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
- G11B 5/59616: {Synchronisation; Clocking (G11B5/59622 takes precedence)}
- G11B 5/746: {Bit Patterned record carriers, wherein each magnetic isolated data island corresponds to a bit}
- G11B 20/10222: {clock-related aspects, e.g. phase or frequency adjustment or bit synchronisation (dedicated sync patterns in the modulation code G11B20/1403)}
- G11B 2220/252: Patterned or quantised magnetic media, i.e. bits are stored in predefined single domain elements
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES

## Abstract

An apparatus includes a bit patterned magnetic storage media, a write transducer positioned adjacent to the bit patterned magnetic storage media, a write driver coupled to the write transducer to deliver write pulses to the write transducer, an optical sensor for producing a bit pattern signal, and a timing recovery circuit for producing a synchronization signal in response to the bit pattern signal, wherein the timing of the write pulses is adjusted in response to the synchronization signal.

## Claims

### Claim 1

An apparatus comprising:
a bit patterned magnetic storage media;
a write transducer positioned adjacent to the bit patterned magnetic storage media;
a write driver coupled to the write transducer to deliver write pulses to the write transducer;
an optical sensor for producing a bit pattern signal; and
a timing recovery circuit for producing a synchronization signal in response to the bit pattern signal, wherein the timing of the write pulses is adjusted in response to the synchronization signal.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein the optical sensor comprises:
a near field transducer including a metallic pin and a lens for directing light onto the metallic pin.

### Claim 3 (depends on 2)

The apparatus of claim 2, wherein an end of the pin has a cross-sectional area less than a cross-sectional area of a surface of islands in the bit patterned media.

### Claim 4 (depends on 1)

The apparatus of claim 1, further comprising:
a light source for directing light onto a surface of the bit patterned media; and
a quadrant optical detector for detecting light reflected from a surface of the bit patterned media.

### Claim 5 (depends on 1)

The apparatus of claim 1, wherein the optical sensor senses light reflected from one bit island on the bit patterned magnetic storage media.

### Claim 6 (depends on 1)

The apparatus of claim 1, wherein the optical sensor senses light reflected from a plurality of bit islands on the bit patterned magnetic storage media.

### Claim 7

A method comprising:
using an optical sensor to produce a bit pattern signal representative of locations of bit islands in a bit patterned magnetic storage media; and
using the bit pattern signal to control the timing of write pulses applied to a write transducer to control a direction of magnetization of the bit islands.

### Claim 8 (depends on 7)

The method of claim 7, wherein the optical sensor comprises:
a near field transducer including a metallic pin and a lens for directing light onto the metallic pin.

### Claim 9 (depends on 8)

The method of claim 8, wherein an end of the pin has a cross-sectional area less than a cross-sectional area of a surface of islands in the bit patterned media.

### Claim 10 (depends on 7)

The method of claim 7, wherein the step of using a near field optical transducer to produce a bit pattern signal representative of locations of bit islands in a bit patterned magnetic storage media comprises:
directing light onto a surface of the bit patterned media; and
using a quadrant optical detector for detecting light reflected from a surface of the bit patterned media.

### Claim 11 (depends on 7)

The method of claim 7, wherein the optical sensor senses light reflected from one bit island on the bit patterned magnetic storage media.

### Claim 12 (depends on 7)

The method of claim 7, wherein the optical sensor senses light reflected from a plurality of bit islands on the bit patterned magnetic storage media.

### Claim 13

A method comprising:
directing a spot of light onto a surface of a bit patterned data storage media; and
producing an error signal in response to light reflected from an island on the bit patterned data storage media, wherein the error signal is representative of a position of the spot with respect to the island.

### Claim 14 (depends on 13)

The method of claim 13, wherein the light detector produces first, second, third and fourth detector signals and the error signal is a difference between a sum of the first and fourth detector signals and sum of the second and third detector signals.

### Claim 15 (depends on 13)

The method of claim 13, wherein the error signal comprises:
an edge detection signal.

### Claim 16 (depends on 13)

The method of claim 13, wherein the error signal comprises:
a push-pull signal.

### Claim 17 (depends on 13)

The method of claim 13, wherein the error signal comprises:
a differential phase detection signal.

### Claim 18 (depends on 13)

The method of claim 13, wherein the light detector produces first, second, third and fourth detector signals and the error signal comprises a sum of the first, second, third and fourth detector signals.

### Claim 19 (depends on 13)

The method of claim 13, wherein the spot has a diameter that is less than a width of islands on the bit patterned data storage media.