U.S. patent application number 12/119468 was filed with the patent office on 2008-08-28 for structure and method for storing data on optical disks.
Invention is credited to Stanton M. Keeler, Curtis M. Pleiss.
Application Number | 20080205211 12/119468 |
Document ID | / |
Family ID | 24164851 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080205211 |
Kind Code |
A1 |
Pleiss; Curtis M. ; et
al. |
August 28, 2008 |
STRUCTURE AND METHOD FOR STORING DATA ON OPTICAL DISKS
Abstract
During manufacturing of optical disks, mastering equipment
inserts marks ("high frequency wobble marks" or "HFWMs") into the
wobble of the groove on optical disks to store data. The presence
of a HFWM at a zero crossing of the wobble indicates an active bit
and the absence of the HFWM indicates an inactive bit. The zero
crossing is, for example, a negative zero crossing. A matched
filter is used to detect the shape of the HFWMs. If a HFWM is
detected during a wobble cycle, an active bit is saved in a
register or a memory. If a HFWM is not detected during a wobble
cycle, an inactive bit is saved in a register or a memory. The
active and inactive bits may be coded bits that must be decoded to
data bits. The data bits include information such as a
synchronization mark, a sector identification data, and an error
detection code.
Inventors: |
Pleiss; Curtis M.;
(Longmont, CO) ; Keeler; Stanton M.; (Longmont,
CO) |
Correspondence
Address: |
MACPHERSON KWOK CHEN & HEID LLP
2033 GATEWAY PLACE, SUITE 400
SAN JOSE
CA
95110
US
|
Family ID: |
24164851 |
Appl. No.: |
12/119468 |
Filed: |
May 12, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11338382 |
Jan 23, 2006 |
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12119468 |
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09542681 |
Apr 3, 2000 |
6990058 |
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11338382 |
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Current U.S.
Class: |
369/44.27 ;
G9B/27.027; G9B/7.025; G9B/7.034 |
Current CPC
Class: |
G11B 20/14 20130101;
G11B 27/24 20130101; G11B 2220/2562 20130101; G11B 7/00745
20130101; G11B 20/18 20130101; G11B 27/3027 20130101; G11B 7/0053
20130101; G11B 2220/218 20130101; G11B 2220/2545 20130101 |
Class at
Publication: |
369/44.27 |
International
Class: |
G11B 7/00 20060101
G11B007/00 |
Claims
1. A method for reading information on an optical disk, comprising:
detecting zero crossings of a wobble on the optical disk; detecting
sinusoidal marks in the wobble; outputting an inactive bit upon
detecting a wobble cycle and not the sinusoidal mark; and
outputting an active bit upon detecting a sinusoidal mark.
2. The method of claim 1, further comprising detecting a
synchronization mark of a sector on the optical disk from the
inactive bits and the active bits, wherein a predetermined sequence
of inactive bits and active bits identifies the synchronization
mark.
3. The method of claim 1, wherein the zero crossings are positive
zero crossings.
4. The method of claim 1, wherein the zero crossings are negative
zero crossings.
5. The method of claim 1, further comprising detecting physical
sector information for a sector from the inactive bits and the
active bits.
6. The method of claim 5, wherein the physical sector information
includes a physical sector address.
7. The method of claim 1, further comprising detecting an error
detection code from the inactive bits and the active bits.
8. A method for reading information on an optical disk, comprising:
determining a wobble frequency of a wobble; detecting sinusoidal
marks in the wobble according to the wobble frequency; outputting
an active bit upon detecting the sinusoidal mark; and outputting an
inactive bit when the sinusoidal mark is not detected.
9. The method of claim 8, further comprising detecting a
synchronization mark from the active bits and the inactive
bits.
10. The method of claim 8, further comprising detecting physical
sector information for a sector from the active bits and the
inactive bits.
11. The method of claim 8, further comprising detecting an error
correction code from the active bits and the inactive bits.
Description
RELATED APPLICATIONS
[0001] This application is a Divisional Application of U.S. patent
application Ser. No. 11/338,382, filed Jan. 23, 2006; which is a
Divisional of U.S. patent application Ser. No. 09/542,681, filed
Apr. 3, 2000, the contents of which are incorporated by reference
in their entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to a method to store data on
writeable optical disks, and more particularly to the use of marks
in the wobble of the groove to store data.
[0004] 2. Description of Related Art
[0005] FIG. 1 illustrates a writable optical disk that has tracks
formed from a single spiral groove. The writable optical disk is,
for example, a record-able CD or DVD. The spiral groove increases
in diameter linearly with increasing radius in a mathematical
phenomenon known as the Archimedes Spiral. The interval between
turns of the spiral groove is called the track pitch and this is
nominally constant for most optical disks. The groove is divided
into tracks that each form a 360-degree turn of the groove. The
tracks are further divided into sectors, which are the smallest
units that an optical drive (including reader and writer) accesses.
The optical drive keeps track of where data is stored by the data's
sector number.
[0006] To determine the linear velocity of the tracks, the tracks
in the writable area contain a deviation from the averaged
centerline of the groove called "wobble". FIG. 2 illustrates the
wobble. Optical drives measure the number of cycles during a unit
of time (frequency) to determine the linear velocity of the track.
Optical drives match the clocks used to write data into the tracks
("write speed") with the linear velocity of the tracks so that the
written bits of data are equally spaced apart. For further details,
see for example U.S. Pat. No. 4,972,401 issued to Carasso et
al.
[0007] Writable optical disks must have a reliable method for
reading radial and rotational positions of the tracks so that
optical drives can read from and write to the appropriate locations
in the tracks. Radial and rotational information may be
communicated through prewritten data in the tracks called
pre-embossed headers. In this addressing scheme, the mastering
equipment creates the optical disks with radial and rotational
information written in the groove during the manufacturing of the
optical disks. This addressing scheme displaces some storage area
that can be otherwise used to store user data in order to store
radial and rotational information. For further details, see for
example Standard ECMA-272 from ECMA located at 114 Rue du
Rhone-CH-1204 Geneva Switzerland ("ECMA"), which is hereby
incorporated by reference.
[0008] Radial and rotational information may also be communicated
by modulating the frequency of the wobble. The wobble frequency is
modulated between a first frequency and a second frequency to
communicate an active or inactive bit (e.g., a "1" or a "0" bit).
This addressing scheme is inefficient because multiple wobble
cycles are required to convey an active or inactive bit. As FIG. 2
illustrates, the wobble may include periodic occurrences of square
waves called "Alternating Fine Clock Marks" ("AFCMs") that provides
timing information. Each AFCM has an amplitude 3.5 to 7 times
greater than the amplitude of the wobble. Each AFCM is inverted
from the AFCM in the adjacent tracks. The AFCMs are spaced equally
apart around the tracks to provide timing information. For further
details, see for example Standard ECMA-274 from ECMA, which is
hereby incorporated by reference.
[0009] Radial and rotational information may further be
communicated through a series of pits ("land pre-pits") on the land
areas between the tracks. Land pre-pits create cross talk into the
data because optical drives detect the land pre-pits in the land
areas between the tracks. Closely aligned land pre-pits in adjacent
tracks also create cancellation problems as their presence cancels
their detection by optical drives. Land pre-pits further require a
2-beam mastering system that can generate the groove and the land
pre-pits simultaneously during the mastering of the optical disks.
For further details, see for example Standard ECMA-279 from ECMA,
which is hereby incorporated by reference.
[0010] A master optical disk is formed by coating a glass substrate
with a photoresist, exposing the photoresist to a laser beam
recorder, developing the photoresist, removing the photoresist, and
coating the remaining material with a thin seed-layer of metal to
form the master optical disk. These steps are known as "mastering".
A stamper is made by electroplating nickel onto the master and
removing the nickel from the master to form the stamper. These
steps are known as "electroforming". Optical disks are produced
from the stamper by placing the stamper in a mold cavity of an
injection molding press and injecting molten plastic into the mold.
The resulting molded disks have an imprint of the stamper. These
steps are known as "molding". The molded disks are then coated with
a variety of thin films (e.g., reflective layers, active layers,
overcoats) depending on their type. The molded disks can be coated
by a variety of methods, such as sputtering, spin coating, and
chemical vapor deposition (CVD). Manufacturers of optical disks
include Ritek of Taiwan, Sony of Japan, Matsushita of Japan, and
Imation of Oakdale, Minn.
SUMMARY
[0011] Marks ("high frequency wobble marks" or "HFWMs") in the
wobble of the groove on an optical disk are used to store data. The
presence of a HFWM at a negative zero crossing of the wobble
indicates an active bit while the absence of a HFWM at a negative
zero crossing of the wobble indicates an inactive bit.
Alternatively, the presence of a HFWM at a positive zero crossing
of the wobble indicates an active bit while the absence of a HFWM
at a positive zero crossing of the wobble indicates an inactive
bit. A matched filter outputs an active signal to a decoder logic
when the matched filter detects the shape of a HFWM. The decoder
logic records an active bit when it receives an active signal from
the matched filter. If the logic device does not receive an active
signal from the matched filter within a wobble cycle, the logic
device records an inactive bit. The stored bits include information
such as a synchronization mark used for timing, physical sector
information including a physical sector address, and an error
correction code for correcting misread of the physical sector
information.
[0012] Other aspects and advantages of the present invention will
become apparent from the following detailed description and
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIGS. 1 and 2 illustrate a groove in a prior art optical
disk.
[0014] FIG. 3 illustrates a high frequency wobble mark in
accordance to one embodiment of the present invention.
[0015] FIG. 4 illustrates high frequency wobble marks in adjacent
tracks.
[0016] FIG. 5 is a block diagram illustrating an optical drive that
detects the high frequency wobble marks of FIG. 2.
[0017] FIG. 6 illustrates a schematic of logic 33 of FIG. 5.
[0018] FIG. 7 illustrates a timing diagram of matched filter 32,
logic 33, and wobble detector 34 of FIG. 5.
[0019] FIG. 8 illustrates the data stored by high frequency wobble
marks of FIG. 2.
[0020] FIG. 9 illustrates high frequency wobble marks in accordance
to one embodiment of the present invention.
[0021] Use of the same reference symbols in different drawings
indicates similar or identical items.
DETAILED DESCRIPTION
[0022] In accordance with one aspect of the invention, the presence
of a mark in a wobble cycle ("high frequency wobble mark" or
"HFWM") indicates an active bit (e.g., a "1" bit") and the absence
of a HFWM indicates an inactive bit (e.g., a "0" bit). The active
and inactive bits ("HFWM bits") are decoded to generate data bits.
During the manufacturing of an optical disk, a conventional
mastering equipment inserts the HFWMs in the wobble of the tracks
to save data such a synchronization mark, physical sector
information, and an error correction code. The conventional
mastering equipment can make a conventional disk stamper from the
above-described optical disk and use the conventional disk stamper
to make optical disks in large quantity. The optical disk includes,
for example, a small optical disk 32 mm in diameter. Optical drives
read the synchronization mark and the physical sector information
from optical disks to determine the appropriate sectors for read
and write operations. Optical drives read the error correction code
to detect and correct errors from the reading of the physical
sector information.
[0023] In one embodiment illustrated in FIG. 3, HFWMs have a
sinusoidal shape with an amplitude equal to the amplitude of the
wobble. The amplitude is, for example, 20 nanometers from peak to
peak. Each sector of the optical disk includes, for example, 248
wobble cycles. Thus, 248 HFWM bits may be inserted into the wobble
cycles.
[0024] In one implementation illustrated in FIG. 4, the mastering
equipment inserts HFWMs at points on the optical disk where the
wobble would cross the centerline of the tracks from a region
closer to the inner diameter to a region closer to the outer
diameter ("negative zero crossings"). In FIG. 4, the would-be paths
of the wobble without the HFWMs are illustrated as dashed lines.
The negative zero crossings are labeled as crossings 1 through 4
for track i and crossings 5 to 8 for track i+n. In this
implementation, the absence of HFWMs at negative zero crossings
indicate inactive HFWM bits. In this implementation, optical drives
detect the positive zero crossings of the wobble to determine
wobble cycles, the wobble frequencies, and the linearly velocities
of the tracks.
[0025] In another implementation, the mastering equipment inserts
HFWMs at points on the optical disk where the wobble would cross
the centerline of the tracks from a region closer to the outer
diameter to a region closer to the inner diameter ("positive zero
crossings"). In this implementation, the absence of HFWMs at
positive zero crossings indicate inactive HFWM bits. In this
implementation, optical drives detect the negative zero crossings
of the wobble to determine the wobble cycles, wobble frequencies,
and the linear velocities of the tracks.
[0026] The HFWMs may have a frequency, for example, three to five
times the frequency of the wobble. It is preferred to choose a
frequency that is far from the frequencies of the data so there is
less cross talk between HFWM detection and data detection. The
HFWMs cannot have the same frequency as the wobble because optical
drives will not be able to detect the zero crossings of the wobble
to determine the wobble cycles, the wobble frequencies, and the
linear velocities of the tracks. The HFWMs cannot have a frequency
that is too large because the mastering equipment may not have the
precision to generate the shape of such HFWMs. The frequency limit
of the mastering equipment is, for example, 10.sup.6 Hz.
Furthermore, optical drives may not have the precision to detect
such HFWMs.
[0027] In one implementation, each HFWM is in phase with the HFWMs
in adjacent tracks. Since the amplitude of the HFWMs is no greater
than the amplitude of the wobble, the cross talk between HFWMs in
adjacent tracks is no greater than the cross talk between the
wobbles of the tracks. Using HFWMs that are in phase allows simpler
manufacturing processes as compared to using marks that are not in
phase with adjacent marks.
[0028] FIG. 5 illustrates a schematic diagram of an optical drive
20. Optical drive 20 includes a laser diode 21 that emits
concentrated light that passes through a collimator lens 22, a
polarizing beam splitter 23, a quarter-wave plate 24, and an
objective lens 25. The light is reflected off an optical disk 26
and, with its polarization changed by passing twice through
quarter-wave plate 24, is deflected by polarizing beam splitter 23
to a photo detector 27. Laser diode 21, collimator lens 22,
polarizing beam splitter 23, quarter-wave plate 24, objective lens
25, and photo detector 27 are collectively called an optical pickup
unit (OPU).
[0029] FIG. 5 also provides a top view of the photo detector 27.
Photo detector 27 outputs, for example, currents Ia, Ib, Ic, and Id
according to the intensity of the light that is detected in each of
four quadrants a, b, c, and d of photo detector 27. The intensity
of the light varies due to the wobble of the track. For example, as
optical disk 26 spins and a peak of the wobble passes through
quadrants a and b, the sum of currents Ia and Ib (i.e., current I1)
reaches a maximum as light is reflected into quadrants a and b.
Similarly, when a valley of the wobble passes through quadrants c
and d, the sum of currents Ic and Id (i.e., current I2) reaches a
maximum as light is reflected into quadrant c and d. The maximum of
current I1 is 180 degrees out of phase with the maximum of current
I2. Of course, a photo detector with a different number of elements
and output currents may be used.
[0030] A direct current coupled amplifier 30 adds currents Ia and
Ib and outputs current I1. A direct current coupled amplifier 31
adds the currents Ic and Id and outputs current I2. A direct
current coupled amplifier 28 adds currents I1 and I2 and outputs a
current I3, which represents the data that is stored on a track. A
direct current coupled amplifier 29 subtracts current I2 from
current I1 and outputs a current I4, which represents the wobble of
the track. The output of direct current coupled amplifier 29 is
coupled to an analog-to-digital converter 41. Analog-to-digital
converter 41 converts the amplitude of current I4 to discrete
values at a specified interval, thereby creating a stream of
digital values. Analog-to-digital converter 41 passes these values
to a matched filter 32, a wobble detector 34, and a synchronization
detector 40.
[0031] Matched filter 32 processes the stream of digital values to
look for a HFWM mark. When matched filter 32 finds a HFWM mark,
matched filter 32 outputs an active signal (e.g., a pulse) to a
logic 33 (described later) for conversion to a HFWM bit. Matched
filter 32 is known to one skilled in the art and is for example
described in "Digital and Analog Communication Systems" by Leon W.
Couch II, 1990, p. 497 to 508.
[0032] Wobble detector 34 processes the stream of digital values to
extract the wobble frequency. Wobble detector 34 phase locks to the
wobble frequency and generates a square wave clock signal. Wobble
detector 34 passes this clock signal to logic 33, which uses the
clock signal and the signals from matched filter 32 to extract the
HFWM bits (described later). A decoder 43 also uses this clock
signal to divide the HFWM bits into frames of encoded bits that
decoder 43 decodes to data bits according to the coding scheme
described below in reference to Tables 1 and 2.
[0033] Synchronization detector 40 processes the input digital
stream to look for the synchronization pattern that is encoded at
the start of each information field (described later). When
synchronization detector 40 finds the synchronization pattern, it
outputs an active signal (e.g., a pulse) to decoder 43, indicating
to decoder 43 to start decoding the HFWM bits to data bits, build
the resulting data bits into data bytes 42, and store data bytes 42
in a memory 35 for later use by a system microprocessor.
[0034] FIG. 6 illustrates one embodiment of logic 33. Logic 33
includes a D flip-flop 45 that has its data input terminal 46
coupled to an active signal (e.g., a "1") and its clock input
terminal 48 coupled to the output line of matched filter 32. Thus,
each time matched filter 32 detects a HFWM and outputs an active
signal, D flip-flop 45 outputs an active signal onto its output
line 47.
[0035] D flip-flop 45 also has a reset input terminal 49 coupled to
the wobble clock signal from wobble detector 34, which is delayed
by a buffer 54. Thus, a delayed active wobble clock signal resets D
flip-flop 45. Once reset, D flip-flop 45 outputs an inactive signal
(e.g., a "0") until it receives another active signal at its clock
input terminal 48 from matched filter 32.
[0036] Output line 47 of D flip-flop 45 is coupled to a data input
terminal 51 of a D flip-flop 50. On receipt of an active wobble
clock signal from wobble detector 34 on clock input terminal 53, D
flip-flop 50 outputs the data it receives on terminal 51 from D
flip-flop 45 to an output line 52 to decoder 43. Decoder 43 decodes
the data it receives from D flip-flop 50 to data bits.
[0037] FIG. 7 illustrates a timing diagram highlighting the
operations of matched filter 32, wobble detector 34, and logic 33.
Current I4 represents the wobble of the groove. As FIG. 7
illustrates, the wobble goes through cycles 1 to 5 respectively
from t1 to t2, t2 to t3, t3 to t4, t4 to t5, and t5 to t6. Each
time wobble detector 34 detects a rising edge in the wobble, wobble
detector 34 generates an active wobble clock signal. For example in
cycle 2, wobble detector 34 outputs an active wobble clock signal
55 in response to a rising edge 54.
[0038] Each time matched filter 32 detects a HFWM mark in the
wobble, matched filter 32 outputs an active signal. For example in
cycle 2, matched filter 32 outputs an active signal 57 when it
detects HFWM 56. Each time logic 33 receives an active wobble clock
signal, logic 33 outputs an active signal if it has received an
active signal from matched filter 32 in the last wobble cycle. For
example in cycle 2, D flip-flop 45 of logic 33 (FIG. 6) receives an
active signal 57 at clock terminal 48 and thus outputs an active
signal on line 47 to terminal 51 of D flip-flop 50. D flip-flop 45
continues to output the active signal on line 47 until it is reset.
In cycle 3, D flip-flop 50 outputs an active signal 59 because it
receives wobble clock signal 58 at clock terminal 53 and the active
signal from line 47 at data terminal 51. A delayed wobbled clock
signal 58 resets D flip-flop 45. After being reset in cycle 3, D
flip-flop 45 receives an inactive signal 60 from matched filter 32
at clock terminal 48 and thus outputs an inactive signal on line 47
to terminal 51 of D flip-flop 50. In cycle 4, D flip-flop 50
outputs an inactive signal 62 because it receives wobble clock
signal 61 at clock terminal 53 and an inactive signal from D
flip-flop 45 at data terminal 51.
[0039] FIG. 8 illustrates the information stored as HFWM bits. This
information includes a synchronization mark 36, physical sector
information 37, and a conventional error correction code 38,
collectively known as an information field. Physical sector
information 37 includes a unique physical sector address. Physical
sector information 37 is, for example, 4 bytes. Error correction
code 38 is, for example, 2 bytes. The error correction code is, for
example, ID error detection code ("IED") well understood by one
skilled in the art and described in Section 13.1.2 of Standard
ECMA-274.
[0040] The system microprocessor that controls optical drive 20
reads data bytes 42 in memory 35 to read physical sector
information 37. The system microprocessor uses the detection of
synchronization mark 36 and the read of physical sector information
37 to read from and write to the appropriate sectors on optical
disk 26. The system microprocessor uses the error correction code
to detect and correct errors from the read of the physical sector
address. Alternatively, a hardware instead of the system
microprocessor can be used to detect and correct errors in physical
sector information 37.
[0041] In one implementation, a data bit is encoded in two
consecutive HFWM bits (e.g., a 2-bit frame of HFWM bits) in
accordance with Table 1.
TABLE-US-00001 TABLE 1 HFWM Bits Data Bit 10 0 01 1
In this implementation, a synchronization mark is identified by the
following sequence of HFWM bits: 00001111.
[0042] In another implementation, mastering equipment uses an
encoding scheme to change each 4 data bits to 15 code bits (e.g., a
15 bit frame of HFWM bits) where the 15 code bits are selected from
a maximum length binary sequence (MLBS) generated from a four bit
primary polynomial of "1001". MLBS is known to one skilled in the
art and is for example described in "Error-Correcting Codes" by
Peterson et al., 1991, p. 222 to 223. By using 15 code bits
selected from a MLBS, the chances of reading error are reduced as
the 15 code bits are distinctly different from one and another.
Table 2 illustrates frames of code bits generated from the MLBS and
the data bits they represent. A negative sign before the code name
designates a frame of code bits generated by inverting the frame of
code bits of a corresponding positive code name.
TABLE-US-00002 TABLE 2 Data Bit Values Code Bits Code Name 0000
010110010001111 V0 0001 110101100100011 V2 0010 111101011001000 V4
0011 001111010110010 V6 0100 100011110101100 V8 0101
001000111101011 V10 0110 110010001111010 V12 0111 101100100011110
V14 1000 101001101110000 -V0 1001 001010011011100 -V2 1010
000010100110111 -V4 1011 110000101001101 -V6 1100 011100001010011
-V8 1101 110111000010100 -V10 1110 001101110000101 -V12 1111
010011011100001 -V14
[0043] During manufacturing of optical disks, the mastering
equipment uses code bits from Table 2 to encode HFWM bits for
identification data 37 and error correction code 38 in the wobble.
In one implementation, a 63 bit MLBS is generated from a six bit
primary polynomial of "100001". This 63 bit MLBS is used as
synchronization mark 36. The 63 bit MLBS is, for example,
"010101100110111011010010011100010111100101000110000100000111111-
". By using a different MLBS for synchronization mark 36, the
encoded identification data 37 and error correction code 38 are
less likely to be read as synchronization mark 36. One skilled in
the art will recognize that other MLBS may be used. Furthermore,
other encoding schemes may be used to decrease the chances of
reading error.
[0044] In one implementation illustrated in FIG. 9, multiple HFWMs
are inserted into a single wobble cycle. For example, three HFWMs
are inserted into a single wobble cycle. In this implementation,
matched filter 32 is programmed to detect (match) the shape of the
three HFWMs and output an active signal.
[0045] Although the invention has been described with reference to
particular embodiments, the description is only an example of the
invention's application and should not be taken as a limitation. In
particular, other waveforms of HFWMs can be used. In addition,
other types of encoding schemes may be used to encode the data.
Various other adaptations and combinations of features of the
embodiments disclosed are within the scope of the invention as
defined by the following claims.
* * * * *