Optical disk medium having features for radial tilt detection and apparatus for measuring radial tilt

8/13/2019 Optical disk medium having features for radial tilt detection and apparatus for measuring radial tilt

1/16

Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give

notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in

a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art.99(1) European Patent Convention).

Printed by Jouve, 75001 PARIS (FR)

Europäisches Patentamt

European Patent Office

Office européen des brevets

(19)

E P

1 0 3 1 9 7 0 B 1

*EP001031970B1*(11) EP 1 031 970 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mentionof the grant of the patent:

12.10.2005 Bulletin 2005/41

(21) Application number: 00301412.3

(22) Date of filing: 23.02.2000

(51) Int Cl.7: G11B 7/007, G11B 7/095,

G11B 7/09, G11B 11/105

(54) Optical disk mediumhaving features forradial tiltdetectionandapparatusformeasuringradialtilt

Optische Platte mit Merkmalen zur Radialneigungserfassung, und Vorrichtung zum Messen einer Radialneigung

Disque optique avec des caractéristiques pour détecter une inclinaison radiale, et appareil pour

mesurer une inclinaison radiale

(84) Designated Contracting States:DE FR GB

(30) Priority: 24.02.1999 US 256791

(43) Date of publication of application:30.08.2000 Bulletin 2000/35

(73) Proprietor: Hewlett-Packard Company,A Delaware Corporation

CA 94304 (US)

(72) Inventor: Prikryl, IvanLoveland, CO 80537 (US)

(74) Representative: Carpmaels & Ransford43 Bloomsbury Square

London WC1A 2RA (GB)

(56) References cited:EP-A- 0 099 576 EP-A- 0 886 266

US-A- 4 866 688 US-A- 5 859 820


2/16

EP 1 031 970 B1

2

5

10

15

20

25

30

35

40

45

50

55

Description

FIELD OF INVENTION

[0001] Thisinvention relates generally to optical disks

and more specifically to an optical disk that includes

physical features suitable for use in detecting radial tilt

of the disk relative to an ideal plane.

BACKGROUND OF THE INVENTION

[0002] Optical disks, for example, compact disks

(CD), require precise focusing of an optical beam onto

a data surface. One or more light beams (typically from

a laser diode), illuminate one or more spots on the disk,

and are reflected back into an optical head. In addition

to information about recorded data, the reflected light

beamsgenerally mayalsocarry informationabout track-

ing error (how well a beam is centered on a data track),

and focus error (how well a beam is focused onto the

data surface). Typically, the data surface of an opticaldisk is protected by a transparent substrate on the side

that is illuminated by the laser. In general, whenever an

illuminating beam must pass through the substrate to

reach thedata surface, disk tilt degrades the focus qual-

ity of the illuminating beam. Typically, for the data den-

sities involved in CD media, tilt detection and compen-

sation are not required. However, for higher data densi-

ties, forexample,for DigitalVersatileDisks (DVD), radial

tiltdetection and compensationmay be necessary. Note

that tilt may have a radial component and a tangential

component, but the radial component is typically much

larger (and therefore of more concern) than the tangen-

tial component.[0003] Some optical disk drives use a separate light

beam for radial tilt measurement. See, for example, U.

S. Patent Numbers 5,657,303 and 5,699,340. In order

to simplify the optical head, there is a need for a radial

tilt measurement system that uses the same light beam

that is used for reading the data. However, the tilt infor-

mation should not interfere withthe resulting datasignal.

One approach to providing radial tilt information in the

data reading beam is used by the Advanced Storage

Magneto Optic (ASMO) format. ASMO media is prefor-

matted with permanent (embossed) headers. Each

header starts with tilt measurement marks, formed into

the walls of a groove defining a track. The tilt measure-ment information does not interfere with the data be-

cause data and headers do not coexist at the same

place on the disk. However, rewritable DVD media do

not use permanent headers. There is a need for radial

tilt detection features, in optical media that do not use

permanent headers, that will not interfere with the opti-

cal data signal. Another approach is to provide multiple

tracking error signals. See, for example, U.S. Patent

5,808,985. There is need for radial tilt detection without

requiring any modification to conventional optical

heads.

SUMMARY OF THE INVENTION

[0004] An optical disc medium in accordance with the

invention has a recording thin film structure (data sur-

face) with grooves and lands behind a transparent sub-

strate. Periodically, along radial lines, radial tilt meas-

urement features are provided in the data surface,

wherein the height of the grooves and lands arechanged, preferably over a short circumferential length.

For example, along the radial lines, the height of a

groove (over a short length) may be raised to the height

of a land and the height of a land (over a short length)

may be reduced to the height of a groove. The optical

disk medium is designed in conjunction with the optical

system of the drive so that when the focused laser spot

is centered on a groove, a tracking error signal (for ex-

ample, radial push-pull signal) is zero even if the disk is

radially tilted. If the focused laser spot is centered on an

area having a height that is different than the height of

a groove, for example a land, the tracking error signal

varies when the disk is radially tilted. As a result, whenthe focused laser spot passes over a tilt measurement

feature, an abrupt step in the tracking error signal pro-

videsa measure of themagnitudeanddirection of radial

tilt.The abruptsteps are removed from thetrackingerror

signal by existing low-pass filtering. The tilt measure-

ment features have negligible effect on the data signal,

and negligible effect on filtered tracking error and focus

error signals. No changes are required for the drive op-

tical system. Theonly drive changerequired is addition-

al signal processing of the trackingerror signal to detect

abrupt steps.

[0005] Some proposed formats (for example,

DVD-RAM) usea format calledsingle-spiralgroove andland recording, in which each spiral groove completes

onerevolutionof thediskand then ends at thebeginning

of a spiral land. Each spiral land completes one revolu-

tion of the diskand then ends at the beginning of a spiral

groove. Data is recorded on the grooves and on the

lands. The method of using a change in the groove

height to measure radial tilt is also applicable to single-

spiral groove and land recording.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]

Figure 1A is a block diagram side view of an exam-

ple optical head and disk within an optical disk

mechanism.

Figure 1B is an expanded view of part of the disk of

figure 1A.

Figure 1C is an expanded plan view of a detector

illustrated in figure 1A.

Figure 2 is graph of a radial push-pull signal mag-

1 2


3/16

EP 1 031 970 B1

3

5

10

15

20

25

30

35

40

45

50

55

nitude as a function of radial offset.

Figure 3A is a plan view of an optical disk in accord-

ancewith the invention, illustrating featuresused for

tilt detection.

Figure 3B is an expanded view of part of the optical

disk of figure 3A.

Figure 4 is a graph of a tracking error signal as a

function of time when using an optical disk in ac-

cordance with the invention.

Figure 5A is a plan view of an optical disk having an

alternative track configuration.

Figure 5B is an expanded view of part of the optical

disk of figure 5A.

DETAILED DESCRIPTION OF THE PREFERRED

EMBODIMENT OF THE INVENTION

[0007] Figure 1A illustrates an optical disk system.

The system in figure 1A depicts representative compo-

nents in a manner suitable to illustrate the invention

within the context of a drive, but the system of figure 1A

may not accurately depict any actual optical disk sys-

tem, and there are many variations and many different

configurations. In figure 1A, a laser diode 100 emits co-

herent but uncollimated light. The light passes through

a collimation lens 102, is reflected from a partially-re-

flecting mirror 104, passes through an aperture 106,

through a focusing lens 108, and is focused onto a data

surface within an optical disk 110. Light reflected fromthedata surface in thedisk110passes through partially-

reflecting mirror 104, through a focusing lens 112, and

is detected by a detector array 114. Some or all of the

optical components (100, 102, 104, 106, 108, 112, and

114) may be mounted into an assembly referred to as

an optical head (reference 116). An electronic signal

processing system 117 receives signals from the detec-

torarray114and derives varioussignals, such as a data

signal, a tracking error signal, and a focus error signal.

[0008] In figure 1A, dashed line 118 represents the

optical axis or centerline of the optical system. In figure

1A, angle α is the angle between the optical axis and

the plane of the illuminated area of the disk. Ideally, theplane of the area on the disk 110 that is illuminated by

the focused laser spot is orthogonal to the optical axis

118. That is, angle α should be ninety degrees. Howev-

er, the disk is notperfectlyflat,and is subject to dynamic

forces, so that angle α slightly varies from ninety de-

grees during operation. This patent document is prima-

rily concernedwith measurement of radial disk tilt,of the

illuminated area of the disk, relative to the optical axis

of an optical head. In particular, disk 110 includes phys-

icalfeaturesthat enable measurement of disktilt without

requiring a separate light beam, with negligible effect on

thedata signal, andwithout requiring changes to thede-

sign of the optical head.

[0009] Figure 1B illustrates an expanded cross-sec-

tion view of the optical disk 110. In figure 1B, disk 110

includes a substrate 120. Grooves are formed onto one

surface of the substrate 120. The grooved surface is

coated with a recording thin film structure to form a data

surface, and covered by a protective layer 122. Binarydata are encoded as marks of contrasting reflectance,

or by pits and lands that affect reflectance by changing

the phase of the reflected light. The light reflecting data

surface comprises grooves 124 and lands 126. In figure

1B, the definition of a "groove" is as seen on the surface

of the substrate where the recording thin film structure

is formed. That is, as seen by the optical head, a

"groove" is closer to the optical head than a land. In the

following discussion, a groove is referred to as having

a depth, in the sense that a groove is physically formed

into a surface of a substrate and a land represents the

original surface of the substrate.The focused laser spot

on anoptical disk typicallyhas a central area of relativelyhigh intensity, andseveral side lobe ringshaving a much

lower intensity. The central area of high intensity has an

overall diameter sufficiently large such that when the

center of the spot is centered on a groove, some light

falls onto each adjacent land. Accordingly, in figure 1B,

light ray 128 is depicted as being on the optical axis of

a focused beam directed onto the center of a groove,

and light rays130 at the outer edges of the focused spot

aredepictedas being directedonto thecenters of lands.

In the following discussion, data is assumed to reside

on the surface of grooves, but in general, data may re-

side on lands, or on both lands and grooves. Figure 1B

illustrates a single sided medium. The invention isequally applicable to double sided media, in which ef-

fectively twosubstrates arebonded at thedatasurfaces.

[0010] Figure 1C illustrates a plan view (orthogonal to

the orientation depicted in figure 1A) of the detector ar-

ray 114. The light received at the surface of the detector

array is not uniform, but instead comprises interference

patterns, resulting in an intensity distribution. Ideally,

when the focused laser spot is centered on a track

(groove or land), the interferencepatternon thedetector

array 114 is symmetrical. In figure 1C, array 114 is di-

vided into four quadrants. Typically, a data signal is ob-

tained as the sum of the signals from each of four de-

tector quadrants (A+B+C+D). If the focused laser spotis not centered on a groove, more of the reflected light

may come from an adjacent land. As a result, the inten-

sity distribution on the detector array may become

asymmetrical, so that one half of the sensor array (for

example, quadrants A and B), may receive a different

light intensity distribution than the other half. A differen-

tial signal such as (A+B)-(C+D) is used to measure the

degree to which the focused laser spot is radially offset

from the center of a track (groove or land). This tracking

error signal is commonly called the Radial Push-Pull

(RPP) signal. In systems incorporating the present in-

3 4


4/16

EP 1 031 970 B1

4

5

10

15

20

25

30

35

40

45

50

55

vention, a radial push-pull tracking error signal is used

to additionally provide a measurement of radial tilt.

[0011] Figure 2 illustrates the magnitude of RPP as a

function of radial offset of the center of the laser spot

from the center of a groove, for one particular system.

Line S1 represents the magnitude of RPP with no disk

tilt. Line S2 represents the magnitude of RPP with a ra-

dial tilt of +12 milliradians (α = π/2 + 0.012 radians). LineS3 represents the magnitude of RPP with a radial tilt of

- 12 milliradians (α = π/2 - 0.012 radians). The system

generating the RPP signal illustrated in figure 2 has a

track pitch of 0.76 micrometers, so that when the fo-

cused laser spot is offset by 0.38 micrometers, the spot

is centered on a land (reference 202). RPPas a function

of radial offset in figure 2 has characteristics that are

unique to the present invention. In particular, the system

generating the RPP signal illustrated in figure 2 has

been designed so that RPP is insensitive to radial tilt

when the focused laser spot is centered on a groove

(reference 200). That is, when the focused laser spot is

centered on a groove, RPP is zero even if the opticaldisk is tilted. However, as illustrated in figure 2, when

the focused laser spot is centered on a land (reference

202), RPP varies with tilt. In a system inaccordance with

the invention, the height of grooves is occasionally

changed, thereby providing a measurable step in RPP

if the disk is tilted, even if the spot is centered, without

affecting the data signal.

[0012] When the focused laser spot is centered in a

groove, and when the disk is not tilted, the spot on the

recording thin film structure is symmetrical on the

groove, the reflected light is centeredin theaperture(fig-

ure 1A, 106), and the reflected light is centered on the

detector array (figure 1A, 114). When the disk is tilted,the disk substrate 120 causes the focused laser spot to

become asymmetrical on the groove due to an aberra-

tion called coma. Theasymmetryof the focused spot on

the data surface introduces an asymmetry of light dis-

tribution within the aperture, and asymmetry of light dis-

tribution on the detector array.

[0013] In addition, even without coma, radial disk tilt

causes the entire reflected light pattern to shift within

the aperture, causing one side of the reflected beam to

be vignetted by the aperture. Coma and vignetting each

change the intensity distribution on the detector array,

and the changes can add or cancel. The present inven-

tion utilizes the fact that the vignetting effects and comaeffects can mutually compensate or magnify each other

in the RPP signal. As will described below, the net ef-

fects of coma and vignetting on RPP may be made to

cancel, when the focused spot is centered on a groove,

by a proper selection of groove parameters.

[0014] Many of the variables that affect asymmetry of

light on the detector array due to coma, and asymmetry

of light distribution within the aperture, are mostly con-

trolled by system requirements or industry standards.

For example, in the system generating the offset re-

sponse illustrated in figure 2, the laser wavelength (650

nanometers), reflectance (0.2), track pitch (0.76 mi-

crometers), and groove width (0.38 micrometers) are all

selected to satisfy various system requirements or

standards. For the system generating the offset re-

sponse illustrated in figure 2, the aperture is round, and

truncates the disk illuminating beam (which has a gaus-

sian distribution) fallingoutsidea boundary representing

an intensity of 50% of the peak intensity at the center of the beam. However, one of the most important param-

eters that affects light distribution of the reflected beam

within theapertureand on thedetectorarray is thedepth

of a groove relative to the surface of a land. Recall that

thefocused spot is distributed over thewidthof a groove

andonto theadjacent lands. Adjusting the groove depth

causes the interference patterns on the detector array

to change. For the system generating the offset re-

sponse illustrated in figure 2, the depth of a groove (rel-

ative to the surface of a land) was empirically adjusted

to a depth of 52 nanometers, in an optical modelingpro-

gram, so that the net effect of coma on RPP was can-

celed by the net effect of vignetting by the aperture onRPP when the focused spot is centered on a groove. As

a result, RPP is insensitive to radial tilt when thefocused

laser spot is centered on a groove (figure 2, reference

200) and has increased sensitivity to radial tilt when the

focused spot is centered on a land (figure 2, reference

202). Note that for data recording on a land instead of

a groove, it is possible to select the disk groove depth

so that the RPP signal will be insensitive to radial tilt

when the focused spot is centered on a land and will

have increased sensitivity to radial tilt when the focused

spot is centered on a groove. Alternatively, as will dis-

cussed further below, for single-spiral groove and land

systems, it may be preferable to select groove depth sothat the RPP signal is insensitive to radial tilt when the

focused spot is centered between thecenterof a groove

and the center of a land.

[0015] Figure 3A illustrates an optical disk 110 in ac-

cordance with the invention. The optical disk 110 in-

cludes an inner hole 300 for mounting. A data area ex-

tends from an inner radius 302 to an outer radius 304.

The data area may comprise one spiral grove (separat-

ed by lands), multiple concentric circular grooves sepa-

rated by lands, or other arrangements of grooves sep-

arated by lands. Radial tilt measurement features are

provided along multiple radial lines 306, within the data

area, wherein the height of grooves and lands arechanged. For example, at a radius where there is nor-

mally a groove, the recording thin film structure may be

fabricated to have the height of a land, and at a radius

where there is normally a land, the recording thin film

structure may be fabricated to have the height of a

groove. Figure 3A depicts three radial lines (306), but

the number three is not a requirement. For some sys-

tems, having the groove height step up and down fewer

than three times per revolution of the disk may be suffi-

cient, and for other systems, more than three steps up

and down per revolution of the disk may be preferable.

5 6


5/16

EP 1 031 970 B1

5

5

10

15

20

25

30

35

40

45

50

55

Stepping the groove height to the height of a land and

stepping land height to theheight of a groove is conven-

ient for manufacturability, but from figure 2, it can be

seen that other steps in groove height and land height

are acceptable. The only requirement is that the chang-

es in height result in a detectable step in theRPP signal.

[0016] Figure 3B illustrates an expanded view of the

area alonga radial line 306where thegroovesand landshave steps in height. In figure 3B, cross-hatched areas

depict surfaces on the recording thin film structure hav-

ing the height defined as a land, and non-cross-hatched

areasdepict surfaceson the recording thinfilm structure

having a height defined as a groove. Accordingly, refer-

ence number 308 designates grooves, and reference

number 310 designates lands. Within a groove 308,

along radialline 306, the height is changed to theheight

of a land, as designated by reference number312. With-

in a land, along radial line 306, the height is changed to

the height of a groove, as designated by reference

number 314.

[0017] Preferably, the circumferential length of thecentral part of area 312 is less than the shortest length

that can be resolved by the optical system, in order to

minimize any effect on the data signal by the tilt detec-

tion feature. Writing and reading data is synchronized

with a clock signal. A channel bit width is defined as a

distance on the data surface determined by one data

clock period times the circumferential velocity of the

disk. For a disk using "8/16" modulation, the shortest

mark that canbe resolved by theoptical system is about

three times the channel bit width. For a 4.7 gigabyte

DVD medium using "8/16" modulation, a channel bit

width is 133 nanometers. For this case, the circumfer-

entiallength of thecentral part of area 312maybe abouttwo channel bit widths, or about 266 nanometers.

[0018] Recall that the data signal is a sum (figure 1C,

A+B+C+D) and recall that a focused laser spot centered

on a groove overlaps onto the adjacent lands. The cir-

cumferential length of the land segments (area 314) ad-

jacent to the tilt detection features in the groove, and

with changed land height, is selected to further reduce

any effect on the data signal by the tilt detection fea-

tures. Since the intensity of the laser spot is substantially

lower over the lands relative to the center of the spot,

the circumferential length of each area 314 needs to be

greater thanthe circumferentiallength of eacharea312,

such that the light reflected from two combined areas314 on adjacent lands can compensate for any pertur-

bation introduced into the sum data signal by area 312

on the groove. In the system illustrated in figure 3, the

circumferential length of the central part of each area

314 is about 5.5 channel bit widths.

[0019] Figure 4 illustrates a radial push-pull signal

(RPP) 400 as a function of time when using an optical

disk as illustrated in figures 3A and 3B. When a focused

laser spot passes over an area 312 (figure 3) within a

groove, a pulse (402, 404) in RPP indicates that thedisk

is radially tilted. The magnitude and direction of the

pulse in RPP provide a measure of the magnitude and

direction of radial tilt. After detection of tilt signals (402,

404), the RPP signal 400 may be low pass filtered to

prevent the pulses from interfering with tracking offset

control.

[0020] Optical disk systems commonly also derive a

focus error signal from signals from the detector array

(figure 1A, 114). However, the focus control, similarly asfor tracking offset control, is much lower frequency than

the data information, so that low pass filtering for the

focus control also removes anyhigh frequency steps re-

sulting from the radial tilt measurement features (figure

3B, areas 312 and 314).

[0021] The radial tilt measurement features do not af-

fect data writing. That is, when data is written, the tilt

measurement features may be ignored, and data may

be written over the tilt measurement features.

[0022] In proposed single-spiral groove and land for-

mats, for example DVD-RAM and ASMO, spiral tracks

have a "switching point," at which thespiral track chang-

es from a groove to a land or vice-versa. Figure 5A il-lustrates a single-spiral groove and landdisk500 having

a spiral track 502. The switching point is along a radial

line 504. Figure 5B provides additional detail of the

switching point. In figure 5B, along radial line 504,

groove 506 changes to a land 508, and land 510 chang-

es to a groove 512. A disk as illustrated in figures 5A

and 5B may be designed so that a tracking error signal

is insensitive to tilt when the focused laser spot is cen-

tered on a groove (or land). Referring to figure 2, if the

disk is not tilted, switching from position 200 to position

202does not result in a step in the trackingoffset signal.

However, if thediskis tilted, theswitchingpoint then pro-

vides a single abrupt step in the tracking error signal,once every revolution. For example, the tracking signal

may exhibit a positive step when switching from a

groove to a land, and then one revolution later the track-

ing signal may exhibit a negative step when switching

from a land to a groove, if the disk is radially tilted. Al-

ternatively, it may be preferable to design the disk so

that when the focused spot is centered on a groove, the

tracking error signal change for radial tilt is the same

magnitude as the magnitude change when the focused

spot is centered on a land,butopposite in direction.That

is, in figure 2, curves S2 and S3 may be shifted horizon-

tally so that, for example, at position 200, curve S2 is

above curve S1 and curve S3 is below curve S1, and atposition 202, curve S2 is below curve S1 and curve S3

is above curve S1, with the magnitudes of the differenc-

es equal. Then, an abrupt step in the tracking error sig-

nal occurs when the focused spot transitions from a

groove to a land, and vice-versa, and if there is no radial

tilt, the steps are equal in magnitude but opposite in di-

rection. However, when the disk is radially tilted, the

steps have unequal magnitude.

[0023] The foregoing description of the present inven-

tion has been presented for purposes of illustration and

description. It is not intended to be exhaustive or to limit

7 8


6/16

EP 1 031 970 B1

6

5

10

15

20

25

30

35

40

45

50

55

the invention to the precise form disclosed, and other

modifications and variations may be possible in light of

the above teachings. The embodiment was chosen and

described in order to best explain the principles of the

invention and its practical application to thereby enable

others skilled in the art to best utilize the invention in

various embodiments and various modifications as are

suited to the particular use contemplated. It is intendedthat the appended claims be construed to include other

alternative embodiments of the invention except insofar

as limited by the prior art.

Claims

1. An optical disk medium (110) comprising:

a data surface, the data surface having at least

onegroove (124, 308), each grooveat a groove

height, and lands (126, 310) adjacent to each

groove (124, 308), each land (126, 310) at aland height; characterised by:

a plurality of first areas (312),along a radial

line on the disk; each first area (312) being

in a groove (124, 308), having a height that

isdifferent than thegrooveheight, andhav-

inga circumferential lengththat is less than

a circumferenceof thediskat theradial dis-

tance of the first area (312); and,

a plurality of second areas (314), along the

radial line, one second area (314) on each

land (126, 310) adjacent to each first area

(312), each second area (314) having aheight that is different than the land height.

2. The optical disk (110) of claim 1, wherein the height

of each first area (312) is the land height and the

height of each second area (314) is the groove

height.

3. The optical disk (110) of claim 1, wherein the data

surface is adapted to receive data marks, the data

marks having a specified shortest data mark length,

and wherein each first area (312) has a circumfer-

ential length that is less than the specified shortest

data mark length.

4. A disk system comprising:

an optical disk (110) having:

a data surface, the data surface having at

least one groove (124, 308) each groove

at a groove height, and lands (126, 310)

adjacent to each groove (124, 308), each

land (126, 310) at a land height;

an optical system (116), including a light source

(100) and an optical detector array (114),

wherein light from the light source is focused

onto the data surface of the optical disk and

light reflected from the data surface is directed

onto the optical detector array, and wherein a

plurality of signals are generated by the detec-

tor array; characterised by:

theoptical disk (110)further havinga radial

tilt measurement area (312, 314) compris-

ing a plurality of first areas (312) along a

radial line on the disk, each first area (312)

being in a groove (124, 308), and having a

height that is different than the groove

height; and a plurality of second areas

(314) along theradial line,one second area

(314) on each land (126, 310) adjacent to

each first area (312), each second area

(314) having a height that is different than

theland height; and thedisk system further comprising:

an electronics system (117),deriving a

tracking error signal (figure 2, S1; fig-

ure 4, 400) from the plurality of signals

from the detector array;

wherein when light is reflected from the radial

tilt measurement area (312, 314) on the data sur-

face onto the detector array, and when the disk is

locally radially tilted, a detectable magnitude

change occurs in the tracking error signal (figure 2,

S2, S3; figure 4, 402, 404); andthe electronics system measuring radial tilt

from the detectable magnitude change in the track-

ing error signal.

5. The disk system of claim 4, further comprising:

an optical aperture (106), wherein light reflect-

ed from the data surface passes through the

optical aperture before being directed onto the

detector array.

6. The disk system of claim 5, wherein the height of

each first area (312) is the land height and theheight of each second area (314) is the groove

height.

7. A method of measuring radial tilt of an optical disk

(110) as claimed in any of claims 1-6, the method

comprising the following steps:

detecting light reflected from the optical disk;

deriving a trackingerrorsignal (figure 2, S1; fig-

ure 4, 400) from the detected reflected light;

and,

9 10


7/16

EP 1 031 970 B1

7

5

10

15

20

25

30

35

40

45

50

55

detectingan abruptstep in themagnitude of the

tracking error signal (figure 2, S2, S3; figure 4,

402, 404), the magnitude of the abrupt step in-

dicating a magnitude of radial tilt.

Patentansprüche

1. Ein Optische-Platte-Medium (110) mit folgenden

Merkmalen:

einer Datenoberfläche, wobei die Datenober-

fläche zumindest eine Rille (124, 308), wobei

sich jede Rille in einer Rillenhöhe befindet, und

Stege (126, 310) benachbart zu jeder Rille

(124, 308), wobei sich jeder Steg (126, 310) in

einer Steghöhe befindet, aufweist; gekenn-

zeichnet durch:

eine Mehrzahl erster Bereiche (312) ent-

lang einer Radiallinie auf der Platte; wobeisich jeder erste Bereich (312) in einer Rille

(124, 308) befindet, eine Höhe aufweist,

die sich von der Rillenhöhe unterscheidet,

und eine Umfangslänge aufweist, die klei-

ner ist als ein Umfang der Platte in der Ra-

dialentfernung des ersten Bereichs (312);

und

eine Mehrzahl zweiter Bereiche (314) ent-

lang der Radiallinie, wobei sich ein zweiter

Bereich (314) auf jedem Steg (126, 310)

benachbart zu jedem ersten Bereich (312)

befindet, wobei jeder zweite Bereich (314)eine Höhe aufweist, die sich von der Steg-

höhe unterscheidet.

2. Die optische Platte (110) gemäß Anspruch 1, bei

der die Höhe jedes ersten Bereichs (312) die Steg-

höhe ist und die Höhe jedes zweiten Bereichs(314)

die Rillenhöhe ist.

3. Die optische Platte (110) gemäß Anspruch 1, bei

der die Datenoberfläche angepasst ist, um Daten-

markierungen aufzunehmen, wobei die Datenmar-

kierungen eine spezifizierte kürzeste Datenmarkie-

rungslänge aufweisen, und bei der jeder erste Be-reich (312) eineUmfangslängeaufweist,die kleiner

ist als die spezifizierte kürzeste Datenmarkierungs-

länge.

4. Ein Plattensystem mit folgenden Merkmalen:

einer optischen Platte (110) mit folgendem

Merkmal:

einer Datenoberfläche, wobei die Daten-

oberfläche zumindest eineRille (124, 308),

wobei sich jede Rille in einer Rillenhöhe

befindet, und Stege (126, 310) benachbart

zu jeder Rille (124, 308), wobei sich jeder

Steg(126, 310) in einer Steghöhebefindet,

aufweist;

einem optischen System (116), das eine Licht-

quelle (100) und ein optisches Detektorarray(114) umfasst, wobei Licht von der Lichtquelle

auf die Datenoberfläche der optischen Platte

fokussiertwirdund vonder Datenoberfläche re-

flektiertes Licht auf das optische Detektorarray

gerichtet wird,und wobei eine Mehrzahlvon Si-

gnalen durch das Detektorarray erzeugt wird;

gekennzeichnet durch:

die optische Platte (110), die ferner einen

Radialneigungsmessbereich (312, 314)

aufweist, der eine Mehrzahl erster Berei-

che (312) entlang einer Radiallinie auf der

Platte,wobei sich jeder erste Bereich (312)in einer Rille (124, 308) befindet und eine

Höhe aufweist, die sich von der Rillenhöhe

unterscheidet; und eine Mehrzahl zweiter

Bereiche (314) entlang der Radiallinie,wo-

bei sich ein zweiter Bereich (314) auf je-

dem Steg (126, 310) benachbart zu jedem

ersten Bereich (312) befindet, wobei jeder

zweite Bereich (314) eine Höhe aufweist,

die sich von der Steghöhe unterscheidet,

aufweist; wobei das Plattensystem ferner

folgendes Merkmal aufweist:

ein Elektroniksystem (117), das einVerfolgungsfehlersignal (Fig. 2, S1;

Fig. 4, 400) aus der Mehrzahl von Si-

gnalen aus dem Detektorarray herlei-

tet;

wobei, wenn Licht von dem Radialneigungs-

messbereich (312, 314) auf die Datenoberfläche

auf dem Detektorarray reflektiert wird und wenn die

Platte lokal radial geneigt ist, eine erfassbare Be-

tragsänderung in dem Verfolgungsfehlersignal (Fig.

2, S2, S3; Fig. 4, 402, 404) auftritt; und

das Elektroniksystem eine Radialneigung aus der

erfassbaren Betragsänderung in dem Verfolgungs-fehlersignal misst.

5. Das Plattensystem gemäß Anspruch 4, das ferner

folgendes Merkmal aufweist:

eine optische Apertur (106), wobei von der Da-

tenoberfläche reflektiertes Licht durch die opti-

sche Apertur läuft,bevor es aufdas Detektorar-

ray gerichtet wird.

6. Das Plattensystem gemäß Anspruch5, bei dem die

11 12


8/16

EP 1 031 970 B1

8

5

10

15

20

25

30

35

40

45

50

55

Höhe jedes ersten Bereichs (312) die Steghöhe ist

und die Höhe jedes zweiten Bereichs (314) die Ril-

lenhöhe ist.

7. Ein Verfahren zum Messen einer Radialneigung ei-

ner optischen Platte (110) gemäß einem der An-

sprüche 1 bis 6, wobei das Verfahren die folgenden

Schritte aufweist:

Erfassen von von der optischen Platte reflek-

tiertem Licht;

Herleiten eines Verfolgungsfehlersignals (Fig.

2, S1; Fig. 4, 400) aus dem erfassten reflektier-

ten Licht; und

Erfassen einer abrupten Stufe bei dem Betrag

des Verfolgungsfehlersignals (Fig. 2, S2, S3;

Fig. 4, 402, 404), wobei der Betrag der abrup-

tenStufe einen Betrageiner Radialneigung an-

zeigt.

Revendications

1. Disque optique (110) comprenant :

unesurfacede données, lasurface de données

ayant au moins une rainure (124, 308), chaque

rainure étant à une hauteur de rainure, et des

plats (126, 310) adjacents à chaque rainure

(124, 308), chaque plat (126, 310) étant à une

hauteur de plat ; caractérisé par :

une pluralité de premières zones (312) le

long d'une ligne radiale sur le disque ; cha-

que première zone (312) étant dans une

rainure (124, 308), ayant une hauteur qui

est différente de la hauteur de rainure, et

ayant une longueurcirconférentielle quiest

inférieure à une circonférence du disque à

la distance radiale de la première zone

(312) ; et

une pluralité de secondes zones (314), le

long de la ligne radiale, une seconde zone

(314) sur chaque plat (126, 310) adjacenteà chaque première zone (312), chaque se-

conde zone (314) ayant une hauteur qui

est différente de la hauteur de plat.

2. Disque optique (110) selon la revendication 1, dans

lequel la hauteur de chaque première zone (312)

est la hauteur de plat et la hauteur de chaque se-

conde zone (314) est la hauteur de rainure.

3. Disque optique (110) selon la revendication 1, dans

lequel la surface de données est adaptée pour re-

cevoir des marques de données, les marques de

données ayant une longueur de marque de don-

nées la plus courtespécifiée,et dans lequel chaque

premièrezone(312) a une longueurcirconférentiel-

le quiest inférieure à la longueurde marquede don-

nées la plus courte spécifiée.

4. Système de disque comprenant :

un disque optique (110) ayant :

unesurfacede données,la surface de don-

nées ayant au moins une rainure (124,

308), chaque rainure étant à une hauteur

de rainure, et des plats (126, 310) adja-

cents à chaque rainure (124, 308), chaque

plat (126, 310) étant à unehauteur de plat ;

un systèmeoptique (116),comprenant une

source de lumière (100) et un réseau de

détecteurs optiques (114), dans lequel lalumière provenant de la source de lumière

est focalisée sur la surface de données du

disque optique et la lumière réfléchie par

la surface de données est dirigée sur le ré-

seau de détecteurs optiques, et dans le-

quel une pluralité de signaux sont générés

par le réseau de détecteurs ; caractérisé

par :

le disque optique (110) ayant en outre

une zone de mesure d'inclinaison ra-

diale (312, 314) comprenant une plu-

ralité de premières zones (312) le longd'une ligne radiale sur le disque, cha-

que première zone (312) étant dans

une rainure (124, 308) et ayant une

hauteur quiest différentede la hauteur

de rainure ; et une pluralité de secon-

des zones (314) le long de la ligne ra-

diale, une seconde zone (314) sur

chaque plat (126, 310) adjacente à

chaque première zone (312), chaque

seconde zone (314) ayantune hauteur

quiest différentede la hauteur de plat ;

et le système de disque comprenant

en outre :

un système électronique (117),

dérivant un signal d'erreur de

poursuite (figure 2, S1 ; figure 4,

400) de la pluralité de signaux du

réseau de détecteurs ;

dans lequel, lorsque la lumière est réfléchie

depuis la zonede mesure d'inclinaison radiale(312,

314) sur la surface de données vers le réseau de

détecteurs, et lorsque le disque est localement in-

13 14


9/16

EP 1 031 970 B1

9

5

10

15

20

25

30

35

40

45

50

55

cliné radialement,un changement d'intensitédétec-

table se produit dans le signal d'erreur de poursuite

(figure 2, S2, S3 ; figure 4, 402, 404) ; et

le système électronique mesurant une incli-

naison radiale à partir du changement d'intensité

détectable dans le signal d'erreur de poursuite.

5. Système de disque selon la revendication 4, com-prenant en outre :

une ouverture optique (106), dans laquelle la

lumière réfléchie par la surface de données

passe à travers l'ouverture optique avant d'être

dirigée sur le réseau de détecteurs.

6. Système de disque selon la revendication 5, dans

lequel la hauteur de chaque première zone (312)

est la hauteur de plat et la hauteur de chaque se-

conde zone (314) est la hauteur de rainure.

7. Procédé pour mesurer une inclinaison radiale d'undisque optique (110), tel que revendiqué dans l'une

quelconque des revendications 1 à 6, le procédé

comprenant les étapes suivantes :

détecter la lumière réfléchie par le disque

optique ;

dériver un signal d'erreur de poursuite (figure

2, S1 ; figure 4, 400) de la lumière réfléchie

détectée ; et

détecter une marche abrupte dans l'intensité

du signal d'erreur de poursuite (figure 2, S2,S3 ; figure 4, 402, 404), l'importance de la mar-

che abrupte indiquant une importance de l'in-

clinaison radiale.

15 16


10/16

EP 1 031 970 B1

10


11/16

EP 1 031 970 B1

11


12/16

EP 1 031 970 B1

12


13/16

EP 1 031 970 B1

13


14/16

EP 1 031 970 B1

14


15/16

EP 1 031 970 B1

15


16/16

EP 1 031 970 B1

Documents

Optical disk medium having features for radial tilt detection and apparatus for measuring radial tilt