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