U.S. patent application number 09/741263 was filed with the patent office on 2001-05-03 for reproduction apparatus and method.
This patent application is currently assigned to SONY CORPORATION. Invention is credited to Aoki, Nobuyuki.
Application Number | 20010000695 09/741263 |
Document ID | / |
Family ID | 17703720 |
Filed Date | 2001-05-03 |
United States Patent
Application |
20010000695 |
Kind Code |
A1 |
Aoki, Nobuyuki |
May 3, 2001 |
Reproduction apparatus and method
Abstract
A reproducing apparatus and method are provided in accordance
with the invention. The apparatus includes a reader for reading out
data from a recording medium, a controller for controlling the
position of the reader, and a determiner for determining a number
of tracks the controller is to move the reader. The apparatus also
includes a comparator, which compares whether the determined number
of tracks is less than a predetermined number of tracks in which
each of the tracks has an essentially equal number of sectors
therein. If so, the controller moves the position of the reader in
accordance with the equation
T.sub.j=.vertline.S.sub.t-S.sub.c.vertline./S.sub.n wherein T.sub.j
is the number of tracks said reading means is to move, S.sub.t is
the address of the target sector to be read out next, S.sub.c is
the address of the current sector, and S.sub.n is the essentially
equal number of sectors in a track. A method utilizing the
apparatus is also provided.
Inventors: |
Aoki, Nobuyuki; (Kanagawa,
JP) |
Correspondence
Address: |
FROMMER LAWRENCE & HAUG, LLP
10TH FLOOR
745 FIFTH AVENUE
NEW YORK
NY
10151
US
|
Assignee: |
SONY CORPORATION
|
Family ID: |
17703720 |
Appl. No.: |
09/741263 |
Filed: |
December 19, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09741263 |
Dec 19, 2000 |
|
|
|
08957951 |
Oct 27, 1997 |
|
|
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Current U.S.
Class: |
369/44.28 ;
G9B/7.047 |
Current CPC
Class: |
G11B 7/08529 20130101;
G11B 7/08505 20130101 |
Class at
Publication: |
369/44.28 |
International
Class: |
G11B 007/085 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 29, 1996 |
JP |
08-286385 |
Claims
What is claimed:
1. A reproducing apparatus, comprising: reading means for reading
out data from a recording medium; control means for controlling the
position of said reading means; and processing means for
determining a distance for said control means to move said reading
means in accordance with one of a plurality of predetermined
equations, said processing means selecting said one equation in
accordance with said distance.
2. The reproducing apparatus of claim 1, wherein said distance is
determined in accordance with a number of tracks said reading means
is to be moved.
3. The reproducing apparatus of claim 2, wherein a first equation
is utilized if said number of tracks said reading means is to be
moved is less than a predetermined number of tracks, and a second
equation is utilized if said number of tracks said reading means is
to be moved is greater than or equal to a predetermined number of
tracks.
4. The reproducing apparatus of claim 3, wherein said predetermined
number of tracks is equal to a number of tracks in which each track
has an essentially equal number of sectors therein.
5. The reproducing apparatus of claim 3, wherein said predetermined
number of tracks is a number of tracks which is less than a number
of tracks in which each track has an essentially equal number of
sectors therein.
6. The reproducing apparatus of claim 2, wherein said distance is
determined in accordance with a simplified equation for determining
the number of tracks said reading means is to be moved.
7. A reproducing apparatus, comprising: reading means for reading
out data from a recording medium; control means for controlling the
position of said reading means; determination means for determining
a number of tracks for said control means to move said reading
means; and comparing means for comparing whether said number of
tracks is less than a predetermined number of tracks in which each
of said tracks has an essentially equal number of sectors therein,
wherein when said number of tracks is less than said predetermined
number of tracks, said control means moves the position of said
reading means in accordance with the equation
T.sub.j=.vertline.S.sub.t-S.sub.c.vertline./S.sub.n wherein T.sub.j
is the number of tracks said reading means is to move, S.sub.t is
an address of a target sector to be read out next, S.sub.c is the
address of a current sector, and S.sub.n is the essentially equal
number of sectors in a track.
8. The reproducing apparatus method of claim of claim 7, further
comprising storage means for storing a corresponding relationship
between each sector address of the recording medium and the number
S.sub.n of sectors of the track in which the sector is located.
9. The reproducing apparatus of claim 7, wherein said predetermined
number of tracks is equal to a number of tracks in which each track
has an essentially equal number of sectors therein.
10. The reproducing apparatus of claim 9, wherein said
predetermined number of tracks is 1000.
11. The reproducing apparatus of claim 7, wherein said
predetermined number of tracks is a number of tracks which is less
than a number of tracks in which each track has an essentially
equal number of sectors therein.
12. The reproducing apparatus of claim 11, wherein said
predetermined number of tracks is 64.
13. A reproducing method for reading out data from a recording
medium, comprising the steps of: reading data from said recording
medium with a reading means; determining a distance to move said
reading means in accordance with one of a plurality of
predetermined equations; and selecting said one equation in
accordance with said distance.
14. The reproducing method of claim 13, further comprising the step
of determining a number of tracks said reading means is to be
moved.
15. The reproducing method of claim 14, further comprising the
steps of: comparing said number of tracks said reading means is to
be moved to a predetermined number of tracks; utilizing a first
equation if said number of tracks said reading means is to be moved
is less than said predetermined number of tracks; and utilizing a
second equation if said number of tracks said reading means is to
be moved is greater than or equal to said predetermined number of
tracks.
16. The reproducing method of claim 15, further comprising the step
of setting said predetermined number of tracks equal to a number of
tracks in which each track has an essentially equal number of
sectors therein.
17. The reproducing method of claim 15, further comprising the step
of setting said predetermined number of tracks to a number of
tracks which is less than a number of tracks in which each track
has an essentially equal number of sectors therein.
18. The reproducing method of claim 14, further comprising the step
of determining said distance in accordance with a simplified
equation for determining the number of tracks said reading means is
to be moved.
19. A reproducing method for reading out data from a recording
medium, comprising the steps of: reading out data from said
recording medium by a reading means; determining a number of tracks
to move said reading means; comparing whether said number of tracks
is less than a predetermined number of tracks in which each of said
tracks has an essentially equal number of sectors therein;
controlling the position of said reading means in accordance with
the equation T.sub.j=.vertline.S.sub.t-S.sub.c.vertlin- e./S.sub.n
wherein T.sub.j is the number of tracks said reading means is to
move, S.sub.t is an address of a target sector to be read out next,
S.sub.c is an address of a current sector, and S.sub.n is the
essentially equal number of sectors in a track, when said number of
tracks is less than said predetermined number of tracks.
20. The reproduction method of claim 19, further comprising the
step of storing a corresponding relationship between each sector
address of the recording medium and the number S.sub.n of sectors
of the track in which the sector is located.
21. The reproducing method of claim 19, further comprising the step
of setting said predetermined number of tracks equal to a number of
tracks in which each track has an essentially equal number of
sectors therein.
22. The reproducing method of claim 21, further comprising the step
of setting said predetermined number of tracks to 1000.
23. The reproducing method of claim 19, further comprising the step
of setting said predetermined number of tracks equal to a number of
tracks which is less than a number of tracks in which each track
has an essentially equal number of sectors therein.
24. The reproducing method of claim 23, wherein said predetermined
number of tracks is 64.
Description
BACKGROUND OF THE INVENTION
1. This invention relates generally to a reproduction apparatus and
method, and more particularly to a reproduction apparatus and
method wherein a reading out position of a reading out element for
reading out data from a predetermined sector of a predetermined
track of a recording medium is moved to read out data from the
recording medium.
2. At present, optical discs, such as compact discs, on which
digital data are recorded are widely used. On such optical discs,
data are recorded on each of a plurality of sectors of a plurality
of tracks formed in circumferential directions on the discs. Each
of the plurality of sectors is also provided with a sector
address.
3. When reproducing data recorded on an optical disc making use of
an optical pickup, laser light is irradiated upon pits formed on
tracks of the optical disc which are positioned to correspond to
the stored data being transmitted. Light which is reflected from
the pits on the disc is photo-electrically converted, so as to read
out the stored data from each sector.
4. The optical pickup is adapted to move in a radial direction of
the optical disc, and thus in a direction perpendicular to a
tangent of each circular track of the optical disc, for example, by
a drive motor. Accordingly, when data are to be read out
continuously from sectors positioned on different tracks, a control
circuit for controlling the drive motor calculates the number of
tracks the optical pickup must be moved to arrive at the track
having the sector to be read out next. This calculation is made
from a sector address which represents the current position of the
optical pickup and another sector address of a sector to be read
out next. The optical pickup is then moved by the required number
of tracks.
5. Next, an example of the calculation of the distance over which
the optical pickup is to be moved is described with reference to
the flow chart depicted in FIG. 6.
6. First in step S1, a track number T.sub.t of a target track,
which contains a target sector S.sub.t is calculated from the
address of the target sector. In a preferred embodiment, the number
T.sub.t of the target track is calculated in the following
manner.
7. First, the distance along the radius of the disc to the target
T.sub.t track which has the target sector address is represented by
r. The distance along the radius of the disc from the current track
to a reference track which has a reference sector Sr (start point
of a program area) is represented by r.sub.0. The track pitch is
represented by T.sub.p, the rotational speed (linear velocity) of
the optical disc is represented by V1, and the sector frequency is
represented by fs. The sector number S.sub.n (number of sectors) of
a track located at a radius r is represented by an expression
(1).
S.sub.n=2.pi.r.times.fs/V1 (1)
8. In a preferred embodiment, by way of example, in which the
optical disc is a DVD (Digital Versatile Disc), r.sub.0 is fixed at
24.00 mm and T.sub.p is fixed at 0.74 .mu.m while V1 is fixed at
3.49 m/s for a single layer disc but fixed at 3.84 m/s for a dual
layer disc.
9. Furthermore, where the number of tracks from the track having
the reference sector address S.sub.r to the track which has the
target sector address S.sub.t is represented by k, the radius r
from the current track to the track having the target sector
address S.sub.t is represented by an expression (2).
r=r.sub.0+k.times.T.sub.p (2)
10. Accordingly, the total number S of sectors which are contained
between the track having the reference sector address S.sub.r and
the Nth track is represented by an expression (3). 1 S = K = 0 N -
1 S n = K = 0 N - 1 2 fs ( r o + kT p ) VI = 2 fs VI { Nr o + N ( N
- 1 ) T p 2 } ( 3 )
11. The expression (3) is a quadratic equation regarding N and may
be re-written into an expression (4).
.pi..times.fs.times.T.sub.p.times.N.sup.2+.pi..times.fs.times.(2r.sub.0-T.-
sub.p).times.N-V1.times.S=0 (4)
12. Then, solving this equation (expression (4)) for N (track
number), N is represented by an expression (5). 2 N = - fs ( 2 r o
- T p ) + { fs ( 2 r o - T p ) } 2 + 4 fsT p VIS 2 fsT p = 2 r o -
T p 2 T p + 2 r o - T p 2 T p + VIS fsT p ( 5 )
13. Here, since the radius r.sub.0 to the track having the
reference sector is much larger than the track pitch T.sub.p
(r.sub.0>>T.sub.p), N may be represented approximately by an
expression (6) 3 N = - r o T p + ( r o T p ) + VIS fsT p . ( 6
)
14. Accordingly, since the track number T.sub.t of the target track
is equal to the number of tracks the target track is positioned
from the reference track, the track number T.sub.t may be
calculated from the sector address S.sub.t in accordance with an
expression (7). 4 T t = - r o T p + ( r o T p ) 2 + VIS t fsT p ( 7
)
15. Thus, the track number T.sub.t of the track containing the next
sector to be read may be calculated in this manner. It is to be
noted that, from the number T.sub.t of the track, the sector number
S.sub.n on the track is calculated in accordance with an expression
(8). 5 S n = 2 fs { r o + ( T t - 1 ) T p } VI ( 8 )
16. Then, in step S2, from the current sector address S.sub.c of
the current sector, the number T.sub.c of the current track on
which the current sector S.sub.c is located is calculated in
accordance with an expression (9). 6 T c = - r o T p + ( r o T p )
2 + VISc fsT p ( 9 )
17. Then, in step S3, it is determined whether or not the number
T.sub.t of the target track in which is located the target sector
S.sub.t to be read out next is larger than the number T.sub.c of
the current track on which the current sector S.sub.c is located.
If it is determined that the number T.sub.t of the target track is
larger than the number T.sub.c of the current track, then the
direction of movement of the optical pickup is set to the forward
direction toward the outermost circumference of the optical disc in
step S4.
18. On the other hand, if it is determined in step S3 that the
number T.sub.t of the target track on which the target sector
S.sub.t is located is equal to or smaller than the number T.sub.c
of the current track on which the current sector S.sub.c is
located, then the direction of movement of the optical pickup is
set to the reverse direction toward the innermost circumference of
the optical disc in step S5.
19. In step S6, an absolute value
.vertline.T.sub.t-T.sub.c.vertline. of the difference between the
number T.sub.t of the target track on which the target sector
S.sub.t to be read next is located and the number T.sub.c of the
current track on which the current sector S.sub.c is located
determines the number of tracks the optical pickup is to move.
20. In step S7, it is determined whether or not the movement track
number is 0. If it is determined that the movement track number is
0, then movement of the reading out position is stopped. If the
movement track number is not 0, then in step S8 the optical pickup
is moved the appropriate number of tracks, as determined in step
S6. Thereafter, the control returns to step S1 so that it can be
confirmed that the target track has been reached. If it is
determined that the current track T.sub.c is equal to the target
track T.sub.t, then no further movement is performed. However, if
T.sub.c is not equal to T.sub.t, movement of the optical pickup is
performed repetitively (track jumping) until T.sub.c equals
T.sub.t.
21. In this manner, because when the optical pickup is moved an
error may occur, track jumping is performed repetitively until the
optical pickup reaches the target track T.sub.t.
22. However, the method described above is deficient. Since the
number T.sub.c of the current track at the current position of the
optical pickup and the number T.sub.t of the target track of the
destination of the optical pickup, and therefore the required
movement of the optical pickup, are calculated for each required
track jump and movement of the optical pickup in accordance with
expression (7) or expression (9), each of which is a complicated
expression including a square root, the calculation of the movement
track number takes a long time. Thus, it is difficult to move the
optical pickup to the proper position of the target track at a high
speed.
OBJECTS OF THE INVENTION
23. Accordingly, it is an object of the invention to provide an
improved method and apparatus for moving an optical pickup from a
current track to a target track.
24. Another object of the invention is to provide an improved
method and apparatus for moving an optical pickup from a current
track to a target track quickly.
25. A further object of the invention is to provide an improved
method and apparatus for moving an optical pickup from a current
track to a target track quickly by utilizing different formulae to
calculate the required amount of movement based upon the amount of
movement required.
26. Yet another object of the invention is to provide an improved
method and apparatus for moving an optical pickup from a current
track to a target track which utilizes a simple expression to
determine the amount of movement of the optical pickup when the
amount of movement required is relatively small.
27. A still further object of the invention is to provide an
improved method and apparatus for moving an optical pickup from a
current track to a target track which selects a particular formula
to determine the amount of movement of the optical pickup in
accordance with the distance the optical pickup is to be moved.
28. Still other objects and advantages of the invention will in
part be obvious and will in part be apparent from the specification
and the drawings.
SUMMARY OF THE INVENTION
29. Generally speaking, in accordance with the invention, a
reproduction apparatus for reproducing data stored on a recording
medium is provided. The reproduction apparatus includes control
means which calculates the number of tracks over which an optical
pickup must be moved when moving from a current sector to a target
sector to be read next making use of one of a plurality of
calculation expressions depending upon the distance from the
current sector (and track) to the target sector (and track).
30. A reproduction method is also provided in which the number of
tracks over which the position of the optical pickup is to be moved
when moving from a current track to a target track to be read next
is calculated making use of one of a plurality of calculation
expressions depending upon the distance to the target track
containing the target sector to be read out next from the current
track.
31. The invention also comprises a reproduction apparatus,
including control means. When the position of the optical pickup is
to be changed form a current track to a target track containing a
target sector to be read out next, the control means calculates if
the number of tracks which the optical pickup must be moved leaves
the optical pickup within a range of tracks in which the number of
sectors per track at the target track is at least approximately
equal to the number of sectors per track at the current track. If
so, the number of tracks T.sub.t over which the optical pickup must
be moved is calculated in accordance with a simple expression
(T.sub.j=.vertline.S.sub.t-S.sub.c.vertline./S.sub.n), in which the
address of the target sector to be read out next is represented by
S.sub.t, the current sector address is represented by S.sub.c, and
the number of sectors per track at the current and target track is
represented by S.sub.n.
32. The invention further comprises a reproduction method in which
the position of an optical pickup is to be changed from a current
track to a target track including a target sector to be read out
next. If the number of tracks over which the optical pickup is to
be moved leaves the optical pickup within a range of tracks in
which the number of sectors per track at the target track is at
least approximately equal to the number of sectors per track at the
current track, the number T.sub.j of tracks over which the optical
pickup must be moved is calculated in accordance with a calculation
expression (T.sub.j=.vertline.S.sub.t-S.sub.c.vertline./S.sub- .n),
where the address of the target sector to be read out next is
represented by S.sub.t, the address of the current sector is
represented by S.sub.c, and the number of sectors per track at the
current and target track is represented by S.sub.n.
33. The invention accordingly comprises the several steps and the
relation of one or more of such steps with respect to each of the
others, and the apparatus embodying features of construction,
combinations of elements and arrangements of parts which are
adapted to effect such steps, all as exemplified in the following
detailed disclosure, and the scope of the invention will be
indicated in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
34. For a more complete understanding of the invention, reference
is made to the following description and accompanying drawings, in
which:
35. FIG. 1 is a block diagram depicting a reproduction apparatus
constructed in accordance with a first embodiment of the
invention;
36. FIG. 2 is a flow chart illustrating the operation of the
reproduction apparatus of FIG. 1 when the position of an optical
pickup is to be moved;
37. FIG. 3 is a flow chart illustrating the calculation of the
required number of tracks an optical pickup must be moved;
38. FIG. 4 is a block diagram depicting a reproduction apparatus
constructed in accordance with a second embodiment of the
invention;
39. FIG. 5 is a flow chart illustrating the operation of the
reproduction apparatus of FIG. 4 when the position of an optical
pickup is to be moved; and
40. FIG. 6 is a flow chart illustrating a conventional scheme for
movement of an optical pickup.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
41. Reference is first made to FIG. 1, which depicts a reproduction
apparatus constructed in accordance with a first embodiment of the
invention. An optical pickup 1 (reading out means) irradiates laser
light upon an optical disc 101. Optical disc 101 is adapted to
selectively reflect this laser light in accordance with the data
stored thereon. Optical pickup 1 then photo-electrically converts
the reflected light from optical disc 101 and outputs an RF signal
in accordance with a signal obtained from a demodulation circuit 2
which interprets the pattern of the selectively reflected light.
Additionally, optical pickup 1 adjusts the distance of an objective
lens (not shown) built therein from the optical disc 101 in
accordance with a control signal supplied thereto from a servo
controller 7.
42. Demodulation circuit 2 digitizes the RF signal supplied thereto
from the optical pickup 1 in a binary fashion, performs error
correction on the binary digitated data, and then outputs the
reproduced digital data to a sector address detection circuit
3.
43. Sector address detection circuit 3 extracts, from the digital
data supplied thereto, an address of the current sector on which
the digital data are recorded. Thus, an address S.sub.c of the
current sector from which the data is being read is contained
within the data. After being extracted by sector address detection
circuit 3, the current sector address is output to a system
controller 6 (control means). Further, the sector address detection
circuit 3 outputs the digital data supplied thereto to a signal
processing circuit (SPC) 4.
44. Signal processing circuit 4 performs predetermined processing
(for example, decompression of compressed data and so forth) for
the digital data supplied thereto and outputs the data after the
processing to a data outputting circuit (DOC) 5. Further, for
example, where multiplexed data are recorded on the optical disc
101, signal processing circuit 4 selects one of the multiplexed
data in response to a predetermined setting and outputs an address
(sector address) of selected data to the system controller 6.
45. Data outputting circuit 5 is controlled by the system
controller 6 and outputs the data supplied thereto from signal
processing circuit 4 to a predetermined receiving circuit (not
shown). System controller 6 causes servo controller 7 to control
drive systems (a spindle motor 8, a head drive motor 9 and so
forth) in response to the sector address S.sub.c supplied thereto
from sector address detection circuit 3 and a signal supplied
thereto from an inputting element 10 and corresponding to a setting
supplied by a user.
46. Servo controller 7 controls spindle motor 8 to rotate optical
disc 101 so that the linear velocity at the position of optical
pickup 1 where the data is being read out equals a predetermined
velocity, and controls motor 9 so that optical pickup 1 may be
disposed at proper location to read out data, as instructed by
system controller 6.
47. The operation of the reproduction apparatus of FIG. 1 when the
position of optical pickup 1 is to be moved will now be described
making reference to the flow chart of FIG. 2.
48. First in step S21, in response to a signal from signal
processing circuit 4 or inputting element 10, a sector address
S.sub.t of a target sector from which data is to be read out next
is provided to system controller 6. A number T.sub.t of a target
track having the target sector S.sub.t is calculated in accordance
with expression (7) (noted above). Also, the number of sectors
S.sub.n in the target track T.sub.t is calculated in accordance
with expression (8) (noted above).
49. Next in step S22, system controller 6 receives a sector address
S.sub.c of the current sector being read from sector address
detection circuit 3 and calculates a number T.sub.c of the current
track having this current sector S.sub.c sector in accordance with
expression (9) (noted above).
50. Then, in step S23, system controller 6 determines whether or
not the number T.sub.t of the target track containing the target
sector S.sub.t (the next sector to be read) is larger than the
number T.sub.c of the current track containing the current sector
S.sub.c. If system controller 6 determines that the number T.sub.t
is larger than the number T.sub.c, then in step S24 the direction
of movement of optical pickup 1 is set to the forward direction
toward an outermost circumference of optical disc 101.
51. On the other hand, if system controller 6 determines in step
S23 that the number T.sub.t of the target track containing the
target sector S.sub.t is equal to or smaller than the number
T.sub.c of the current track containing the current sector S.sub.c,
then in step S25 the direction of movement of optical pickup 1 is
set to the reverse direction toward an innermost circumference of
the optical disc 101.
52. In step S26, system controller 6 sets a movement track value
equal to an absolute value .vertline.T.sub.t-T.sub.c.vertline.
between the number T.sub.t of the target track having the target
sector S.sub.t (the sector to be read out next) and the number
T.sub.c of the current track having the current sector S.sub.c.
53. In step S27, system controller 6 determines whether or not the
movement track number is 0. If system controller 6 determines that
the movement track number is 0, then it ends the movement of
optical pickup 1, since optical pickup would be positioned within
the proper track to read the next target sector S.sub.t. However,
if system controller 6 determines that the movement track number is
not 0, then in step S28 system controller 6 instructs servo
controller 7 to drive motor 9 so that optical pickup 1 is moved by
a distance equal to the movement track number set in step S26 or
step S30 (hereinafter described). System controller 6 then advances
to step S29.
54. In step S29, system controller 6 determines whether or not the
movement track number is smaller than 1,000. If the movement track
number is equal to or larger than 1,000, then system controller 6
returns control to step S22 to effect processing in steps S22 to
S26 to calculate the movement track number making use of the
expression (9).
55. On the other hand, if system controller 6 determines in step
S29 that the movement track number is smaller than 1,000, then
position of optical pickup 1 on the current track T.sub.c is in the
proximity of the target track T.sub.t. System controller 6 then
calculates the movement track number making use of an expression
(10) (described below) which is simpler than expression (9)
(described above). Here T.sub.j represents the movement track
number.
T.sub.j=.vertline.T.sub.t-T.sub.c/S.sub.n (10)
56. By making use of the expression (10) in this manner, the
movement track number can be calculated simply by using an
expression performing only arithmetical operations and utilizing
only the current sector address T.sub.c, the address T.sub.t of the
target track containing the target sector S.sub.t and the sector
number S.sub.n, representing the number of sectors per track at
both the current and target tracks (which is approximately the same
when T.sub.j is less than 1000). While the number of sectors per
track of a DVD is approximately equal for less than 1,000 tracks,
it is possible to choose the comparison number in step S29 to be
any value less than 1,000. In a preferred embodiment, this number
may be 64. Further, since only the relationship between two points
is utilized in place of a calculation which determines an absolute
position from a reference track, the calculation error in movement
track number is reduced.
57. After this calculation, control is returned to step S27. In
step S27, system controller 6 determines again whether or not the
movement track number is 0. If system controller 6 determines that
the movement track number is 0, then movement of optical pickup 1
ends. However, if system controller 6 determines that the movement
track number is not 0, then in step S28, optical pickup 1 is moved
by a distance equal to the movement track number set in step S30.
System controller 6 then advances to step S29.
58. In such a manner, system controller 6 first performs the
processing in steps S21 to S26 to calculate the movement track
number. If it is determined that the movement track number is
smaller than 1,000, then system controller 6 only performs the
processing in step S30 (making use of the simpler expression) to
calculate the movement track number. By this operation, the time
required for the movement of optical pickup to the proper position
at the target track T.sub.t can be reduced.
59. Now making reference to FIG. 3, the details of the processing
in step S30 of FIG. 2 will be described.
60. In step S41, system controller 6 calculates the movement track
number T.sub.j in accordance with expression (10) assuming that the
number of sectors in the current track are equal. This is a
possible approximation, since in a preferred embodiment where the
optical disc 101 is a DVD, when the movement track number is
smaller than 1,000, the number of sectors per track are
substantially equal. Even if they are not equal, since the position
of optical pickup 1 is adjusted through an interactive until its
position approaches and equals the position of the target track, as
movement of the reading out position is repeated until the target
position is reached, and thus each subsequent move of optical
pickup 1 is smaller and smaller, the sector numbers will become
equal to each other and, the formula is accurate.
61. Then, in step S42, system controller 6 determines whether or
not the address S.sub.t of the target sector to be read out next is
larger than the address S.sub.c of the current sector. If system
controller 6 determines that the address S.sub.t is larger than the
address S.sub.c, then in step S43 system controller 6 sets the
direction in which optical pickup 1 is to be moved to the forward
direction. On the other hand, if system controller 6 determines in
step S42 that the address S.sub.t of the target sector to be read
out next is equal to or smaller than the address S.sub.c of the
current sector, then it sets the direction in which optical pickup
1 is to be moved to the reverse direction in step S44.
62. Then, in step S45, system controller 6 determines whether or
not the remainder of .vertline.S.sub.t-S.sub.c.vertline./S.sub.n in
expression (10) is 0. If the remainder is not 0, then when optical
pickup 1 is moved T.sub.j tracks, it will have moved one track too
few. This is because only whole tracks are counted. By way of
example, if S.sub.n=5 and S.sub.t=18, then S.sub.t will be in the
fourth track. However, expression 10 will determine T.sub.j to be 3
(T.sub.j=.vertline.18-0.vertline./5=3) with a remainder of 3. Thus,
in order to reach the track on which the target sector S.sub.t is
positioned, system controller 6 increments the movement track
number T.sub.j by one in step S46. On the other hand, if it is
determined that the remainder of
.vertline.S.sub.t-S.sub.c.vertline- ./S.sub.n is 0, T.sub.j will
move optical pickup 1 to the proper track, and step S46 is
skipped.
63. In this manner, in step S30 of FIG. 2, calculation of the
movement track number is performed in accordance with expression
(10). It is to be noted that, by utilizing expression (10) in this
manner, the error in determining the movement track number in the
proximity of the target track Tt is reduced, and the number of
times optical pickup 1 must move until the target track is reached
can be reduced.
64. It should also be noted that, when the movement track number is
calculated in step 41 in an alternative embodiment, in place of
dividing the absolute value .vertline.S.sub.t-S.sub.c.vertline. by
S.sub.n, S.sub.n may be successively subtracted from the absolute
value .vertline.S.sub.t-S.sub.c.vertline. until the result of the
subtraction is reduced to 0. The number of such subtraction
iterations may be used as the movement track number. Thus, the
division procedure is performed by iterative subtraction. By this
operation, the load to system controller 6 may be reduced.
65. Further, in a DVD, since the number of tracks corresponding to
a range in which the number of sectors per track is equal is
approximately 1,000, 1,000 is used as the threshold value for the
movement track number in step S29. However, where optical disc 101
is some other disc, the threshold value may be set to a different
dropper threshold value based on the particular type of disc.
Additionally, as noted above, a number less than 1,000 may be used
for the threshold value, such as 64 in a preferred embodiment.
66. Reference is next made to FIG. 4, which depicts a reproduction
apparatus constructed in accordance with a second embodiment of the
present invention. Elements similar to those in the first
embodiment are designated by like reference numbers and the
description thereof is therefore omitted.
67. A ROM 11 (storage means) stores in advance a table indicating
the relationship between the number of sectors per track and track
number for each range of tracks on optical disc. 101.
68. A system controller 6A (control means) controls various
circuits similarly to system controller 6 of the first embodiment,
and further calculates a movement track number in such a manner as
hereinafter described making use of the corresponding relationship
stored in the ROM 11.
69. Reference is now had to FIG. 5, which illustrates the
functioning of the apparatus as shown in FIG. 4.
70. First, in step S61, system controller 6A determines whether or
not the address S.sub.t of a target sector to be read out next is
larger than the address S.sub.c of a current sector. If system
controller 6A determines that address S.sub.t is larger than
address S.sub.c, then in step S62 system controller 6A sets the
direction in which optical pickup 1 is to be moved to the forward
direction and in step S63 sets, the value of variable T.sub.j to be
used for calculation of the movement track number to 0.
71. On the other hand, if system controller 6A determines in step
S61 that address S.sub.t of the target sector to be read out next
is equal to or smaller than address S.sub.c of current sector, then
in step S64 system controller 6A sets the direction in which
optical pickup 1 is to be moved to the reverse direction and in
step S65 sets the value of variable T.sub.j to 1.
72. Then control is returned to step S66 in which system controller
6A determines the distance, or number of sectors Sd1 from a
reference sector Sr to the target sector S.sub.t is calculated in
accordance with the formula
S.sub.d1=.vertline.S.sub.t-Sr.vertline.. Reference sector Sr is
typically located along the inside track of an optical disc, or at
the first sector of the disc. Then, in step S67, a counting
variable "n" is set to zero.
73. In step S68, letter A designates a number of tracks on an
optical disc which all have the same number of sectors, and Sx
equals the total number of sectors in one track in the "A" group of
tracks. In a preferred embodiment a group of "A" tracks=1000. It is
thus determined whether the number of sectors which are between the
target sector (S.sub.t) and the reference sector (S.sub.r)=S.sub.d1
is greater or equal to the number of tracks multiplied by the
number of tracks in the first group "A" of tracks. Thus, the
formula S.sub.d1.gtoreq.(S.sub.0+n).times.A is used. If S.sub.d1 is
greater than the number of sectors in the group of tracks A, then
in step S69, this number of sectors in the group of tracks A is
subtracted from the total number of tracks (S.sub.d1) between the
reference sector (S.sub.r) and the target sector (S.sub.t), and is
saved in variable S.sub.d1. Then, in step S70, a target track
number T.sub.t is incremented by the number of tracks A, and in
step S71, counting variable n is incremented by 1. Control then
returns to step S68.
74. This time through step S68, the number of sectors Sd1 (after
being decremented) is compared to the total number of sectors in
the next group of tracks A all having the same number of sectors.
(But possibly having a different number of sectors per track than
the first group "A".) Since each track in second group A has
S.sub.1 sectors, it is checked whether
S.sub.d1.gtoreq.(S.sub.1).times.A.
75. If so, then control passes to step S69 and the procedure
continues as noted above.
76. If at any time at step S68 it is determined that
S.sub.d1<(S.sub.0+n).times.A, the control passes to step S72,
since it has been determined that the target track number T.sub.t
is within 1000 tracks of the current value of T.sub.t. Thus,
T.sub.t is set equal to the prior value of T.sub.t (after being
incremented for each group of tracks "A", plus the total number of
sectors left to travel S.sub.d1 (after being decremented for the
number of sectors in each group of tracks "A") divided by the
number of sectors per track S.sub.0+n for the current group of
tracks "A" in accordance with the formula:
T.sub.t=T.sub.t+(S.sub.d1/(S.sub.0+n))
77. Thus the number of tracks left to travel within the group of
tracks "A" is added to the number of tracks already determined
necessary to travel, thus giving the total number of tracks between
the reference sector Sr and the target sector S.sub.t.
78. Then in steps S66a to S72a, using the same procedure noted
above with respect to steps S66 to S72, the number of tracks
T.sub.c from the reference sector Sr to the current sector S.sub.c,
at which data is currently being read from, is calculated. In step
S74 the number of tracks to be moved or jumped, T.sub.j is
calculated as the absolute value of the difference between the
number of tracks from the track containing the reference sector to
the target track T.sub.t containing the target sector S.sub.t and
the number of tracks from the track containing the reference sector
to the current track T.sub.c containing the current sector S.sub.c
in accordance with the following formula:
T.sub.j=.vertline.T.sub.t-T.sub.c.vertline.
79. This determines the number of tracks T.sub.j the optical pickup
must move to get from the track containing the current sector to
the track containing the target sector. This number is forwarded to
a storage memory for moving the optical pickup in step S74. In step
S75, it is determined by system controller 6A whether or not the
value of variable T.sub.j (the movement track number), is 0. If it
is determined that movement track number T.sub.j is 0, then it ends
the movement of optical pickup 1.
80. On the other hand, if system controller 6A determines that
movement track number T.sub.j is not 0, then in step S76 system
controller 6A causes servo controller 7 to drive motor 9 to move
optical pickup 1 by a distance corresponding to the movement track
number T.sub.j. System controller 6A then returns control to step
S61. Processing in steps S61 to S75 is repeated until the movement
track number T.sub.j is reduced to 0.
81. As described above, since the ROM 11 stores the number of
sectors S.sub.n per track for a particular group "A" of tracks in
advance, there is no need to calculate S.sub.n, and the processing
is simplified. Thus, the movement of optical pickup to the target
track T.sub.t can be performed in a shorter time.
82. It is to be noted that, for example, when optical disc 101 is a
DVD, the movement of optical pickup 1 can be performed by the
procedure described above for either a single layer DVD or a dual
layer DVD in which addresses in both of the two layers are
allocated from the inner circumference side to the outer
circumference side of the disc.
83. On other hand, for dual layer DVD in which addresses in one of
the two layers are allocated from the outer circumference side to
the inner circumference side of the disc, the movement of optical
pickup 1 can be performed simply if the procedure described above
is modified so that the directions of track jumping are reversed.
In particular, in step S24 of FIG. 2, step S43 of FIG. 3 and step
S62 of FIG. 5, the direction of track jumping is set to the reverse
direction, but in step S25 of FIG. 2, step S44 of FIG. 3 and step
S64 of FIG. 5, the direction of track jumping is set to the forward
direction.
84. Thus, as described above, with the reproduction apparatus and
method of the first embodiment, when the position of the optical
pickup is to be changed to a sector which is to be read out next,
since the number of tracks over which the optical pickup is to be
moved is calculated making use of one of a plurality of calculation
expressions, the choice of which depends upon the distance to the
sector to be read out next, the movement of the optical pickup to
the target track can be performed at a high speed.
85. With the reproduction apparatus and method of the second
embodiment, when the position of the optical pickup is to be
changed to a sector which is to be read out next, when the number
of tracks corresponding to the distance to the next sector is
smaller than the number of tracks corresponding to a range of
tracks in which the number of sectors per track of the recording
medium is equal, the number T.sub.j of tracks over which the
position of the optical pickup is to be moved is calculated in
accordance with a calculation expression
(T.sub.j=.vertline.S.sub.t-S.sub- .c.vertline./S.sub.n) where the
address of the target sector to be read out next is represented by
S.sub.t, the sector address of the current position of the optical
pickup is represented by S.sub.c, and the number of sectors per
track is represented by S.sub.n. Thus, the movement of the position
of the optical pickup to the target track can be performed at a
high speed.
86. It will thus be seen that the objects set forth above, among
those made apparent from the preceding description, are efficiently
attained and, since certain changes may be made in carrying out the
above method and in the constructions set forth without departing
from the spirit and scope of the invention, it is intended that all
matter contained in the above description and shown in the
accompanying drawings shall be interpreted as illustrative and not
in a limiting sense.
87. It is also to be understood that the following claims are
intended to cover all of the generic and specific features of the
invention herein described and all statements of the scope of the
invention which, as a matter of language, might be said to fall
therebetween.
* * * * *