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Claims  |
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What is claimed is:
1. An information apparatus comprising:
buffer means for storing therein recording data in a unit for conversion to
a two-dimensional format;
converting means for converting said recording data into n rows.times.m
columns of two-dimensional data arrangements corresponding to said unit of
data, where n and m are integers of at least two;
m light sources;
recording means for subdividing said n.times.m two-dimensional data
arrangements into m columns of one-dimensional data columns so as to be
read out, and for recording said m columns of one-dimensional data columns
on a single track by said m light sources; and
optical means for converging luminous fluxes from said m light sources and
for forming m light spots on a disk plane;
wherein said recording data are recorded on said disk plane as an optically
distinguishable information identifier group having n.times.m
two-dimensional extended areas; and
wherein a distance between adjacent light spots of said m columns on said
single track in a track radial direction of said disk plane is smaller
than a diameter of a respective one of said adjacent light spots.
2. An information apparatus according to claim 1, wherein said m light
sources are laser light sources forming laser spots along a radial
direction of the disk, a distance over laser light spots formed by the m
laser light sources along the radial direction of the disk being selected
to be "L", and a track pitch of a two-dimensional code being "p", a
relationship among the distance, track pitch and a size of the laser spot
"Ws" is given by:
p.gtoreq.L+Ws.
3. An information apparatus according to claim 1, wherein the disk plane is
subdivided into two-dimensional grids as a two-dimension coding format,
data is recorded as information pits arranged on at least selected ones of
cross points of a respective grid, and a relationship between blocks
corresponding to plural overlapped information pits is such that a
distance between outermost pits of respective blocks is selected to be
longer than an interference distance determined by the optical means.
4. An information apparatus according to claim 1, for at least reproducing
data recorded on an optical disk, comprising:
optical means for converting luminous fluxes from said m light sources and
for forming m light spots on a track of the optical disk, a plurality of
groups of pits representing the data recorded on the track, each of the
groups of pits being arranged in a grid of m columns and n rows, said pits
being formed at cross points of said columns and rows;
positioning means for positioning said m light spots onto said pit group on
the track;
m detecting means for detecting light reflected from said pit group
corresponding to each of the light spots;
generating means for generating m columns of one-dimensional data series
from the reflection light detected by the respective detecting means, and
for generating n.times.m two-dimensional data having m columns and n rows
on the basis of said m columns of said one-dimensional data series; and
reproducing means for reproducing the data from said n.times.m two
dimensional data.
5. An information apparatus as claimed in claim 4, wherein said reproducing
means includes demodulating means for demodulating the reproduced data
from said n.times.m two dimensional data.
6. An information apparatus as claimed in claim 5, wherein a pit group used
for synchronization and appearing at a predetermined interval is recorded
on said disk plane.
7. An information apparatus as claimed in claim 6, wherein said
synchronizing pit group is recorded in (n+1).times.m two-dimensionally
extended areas.
8. An information apparatus as claimed in claim 5, wherein said light
sources used during the recording operation are identical to those used
during the reproducing operation.
9. An information apparatus as claimed in claim 5, wherein said optical
means shifts the adjacent pits along the track radial direction within the
pit group so as to be recorded,
said generating means includes differential calculating means for comparing
with each other signal levels of adjacent data in the generated
one-dimensional data series; and
judging means for judging conditions of the adjacent pits based upon the
output from said differential calculating means, said generating means
generating n.times.m two-dimensional data in accordance with the output
from said judging means.
10. An information apparatus as claimed in claim 4, wherein said optical
means includes means for mutually forming said light spots at positions
delayed by a time delay ".tau." with respect to the track direction; and,
said generating means includes a means for mutually compensating a detected
m columns of one-dimensionally arranged data with a delay time of ".tau.",
said compensating means compensating for the delay time of ".tau." so as
to generate n.times.m two-dimensional data.
11. An information apparatus as claimed in claim 4, wherein said generating
means includes a calculating means for performing a calculating so that
mutual interference in the generated m columns of one-dimensional data is
removed, said calculating means removing the interference so as to
generate n.times.m two-dimensional data.
12. An information apparatus as claimed in claim 4, wherein said generating
means includes:
differential calculating means for comparing with each other signal levels
of adjacent data of said one-dimensional data; and,
judging means for judging conditions of the adjoining pits based on both
the signal levels of the adjacent data of said one-dimensional data series
and the output from said differential calculating means, said generating
means generating n.times.m two-dimensional data in accordance with the
output from said judging means.
13. An information apparatus as claimed in claim 4, wherein said m light
spots are formed at such positions that axial lines to connect said spots
are inclined with respect to a radial direction of the track.
14. An information apparatus as claimed in claim 4, wherein said
positioning means includes:
tracking position positioning means for performing a positioning operation
of the light spots along the tracking direction by utilizing diffraction
light from guide grooves of the tracks of the disk; and
discriminating means for discriminating a portion on the track of the disk
where the pits are present from another portion thereof where no pit is
present;
said tracking position positioning means performing the light spot
positioning operation in the tracking direction with employment of the
diffraction light emitted from the track portion having no pit which is
discriminated by said discriminating means.
15. An information apparatus as claimed in claim 1, wherein said
information identifier group is a pit group.
16. An information apparatus as claimed in claim 15, wherein said "n"
corresponds to a line in a track direction of the disk and said "m"
corresponds to a column in a track radial direction thereof in said
n.times.m pit groups, said "n" being an integer larger than 3 and said "m"
being an integer larger than 2.
17. An information apparatus as claimed in claim 15, wherein said recording
means includes a means for mutually giving a time delay of ".tau." to the
m columns of one-dimensionally arranged data, and for controlling said m
light sources by giving the time delay ".tau." and
said optical means mutually forms said light spots at positions delayed by
the delay time ".tau." with respect to a track direction.
18. An information reproducing apparatus for reproducing data recorded on
an optical disk, comprising:
m light sources;
optical means for converting luminous fluxes from said m light sources and
for forming m light spots on a track of the optical disk, a plurality of
groups of pits representing the data recorded on the track, each of the
groups of pits being arranged in a two-dimensional grid of m columns and
"n" rows, m and n being positive integers of at least two, said pits being
formed at cross points of said columns and rows;
positioning means for positioning said m light spots onto said pit groups
on the track;
m detecting means for detecting light beams reflected from said pit group
so as to detect m columns of one dimensional data columns on a single
track by said m light sources;
generating means for generating m columns of one-dimensional data from the
detected light beams, and for generating two-dimensional data having m
columns and n rows on the basis of the m columns of one-dimensional data;
and
reproducing means for reproducing the information data from said
two-dimensional data;
wherein a distance between adjacent light spots of said m columns on said
single track in a track radial direction of the optical disk is smaller
than a diameter of a respective one of said adjacent light spots.
19. An information reproducing apparatus according to claim 18, wherein
said reproducing means includes demodulating means for demodulating the
data from said n.times.m two-dimensional data.
20. An information recording/reproducing method comprising the steps of:
coding information to be recorded into a two-dimensional information format
of n rows.times.m columns, where n and m are integers of at least two;
converting said two-dimensional information into a one-dimensional
information format;
modulating a plurality of laser light sources in accordance with the
one-dimensional information format so as to record two-dimensional codes
on an optical disk, wherein m columns of one-dimensional data columns are
recorded on a single track by m laser light sources providing m light
spots;
reproducing said recorded two dimensional coded information utilizing a
plurality of laser light sources;
photoelectrically converting the reproduced two-dimensional information as
a signal;
detecting a one-dimensionally arranged signal from the photo-electrically
converted signal; and
decoding two dimensional information in accordance with the
photo-electrically converted signal;
wherein a distance between adjacent light spots of said m columns on said
single track in a track radial direction of the optical disk is formed to
be smaller than a diameter of a respective one of said adjacent light
spots.
21. An information recording/reproducing method comprising the steps of:
storing data to be recorded in a unit of a two-dimensional format;
coding said stored data as n.times.m two-dimensional data arrangement,
where n and m are positive integers of at least two;
subdividing said n.times.m two-dimensional data series into m columns of
one-dimensional data series, and controlling m light sources in accordance
therewith;
converging luminous fluxes from said m light sources so as to form m light
spots on a track of an optical disk;
recording on the track of said optical disk data to be recorded as an
optically distinguishable pit group having n.times.m two-dimensionally
extended areas so as that said m columns of one-dimensional data series
are recorded on a single track by said m light sources;
positioning said m light spots on said pit group on the track of the
optical disk;
detecting light reflected from pit group corresponding to each of the light
spots;
generating m columns of one-dimensional data series from the detected
reflected light, and generating two-dimensional data having m columns and
n rows on the basis of the m columns of one-dimensional data series; and
decoding data from said n.times.m two-dimensional data;
wherein a distance between adjacent light spots of said m columns on said
single track in a track radial direction of the optical disk is formed to
be smaller than a diameter of a respective one of said adjacent light
spots.
22. An information recording/reproducing method as claimed in claim 21,
wherein said generating step includes producing mark synchronization
signals in accordance with synchronization marks formed on the optical
disk at predetermined intervals, frequency-dividing said mark
synchronization signals so as to produce a synchronization signal for
enabling reading of the pits, sampling signals of the lights reflected
from said detected pit group in accordance with the synchronization signal
for reading the pits, and comparing said sampled signals with a
predetermined level to determine whether or not pits are present.
23. A method for recording and reproducing an information on an optical
recording disk, wherein the information is recorded as recording pits on
the disk, and said information is reproduced by detecting said pits by
reflecting lights from said pits, said method comprising the steps of:
converting inputted one-dimensional serial data in a form of binary digital
data into groups of digital data in a two-dimensional format of n
rows.times.m columns including m columns of one-dimensional serial data,
where n and m are integers of at least two;
recording said groups of digital data on a predetermined area on said disk
as groups of the recording pits so that said m columns of one-dimensional
serial data are recorded on a single track by m light sources providing m
light spots;
identifying the group of the recording pits as a unit; and
reproducing the binary digital data on the basis of the identified groups
of the recording bits;
wherein a distance between adjacent light spots of said m columns on said
single track in a track radial direction of the disk is formed to be
smaller than a diameter of a respective one of said adjacent light spots.
24. A method for recording and reproducing an information on an optical
recording disk, wherein the information is recorded as recording pits on
the disk, and said information is reproduced by detecting said pits by
reflected light from said pits, said method comprising the steps of:
converting inputted one-dimensional serial data in a form of binary digital
data into groups of digital data in a two-dimensional format of n
rows.times.m columns including m one-dimensional arrangements of n bits,
said m and n being integers of at least two;
recording said groups of digital data as groups of recording pits formed of
existence or absence of the pits on cross points of a grid of n rows and m
columns of a predetermined area on said disk so that said m columns
including m one-dimensional arrangements are recorded on a single track by
m light sources;
identifying the group of the recording pits as a unit; and
reproducing the binary digital data on the basis of the identified groups
of recording pits;
wherein a distance between adjacent light spots of said m columns on said
single track in a track radial direction of the disk is formed to be
smaller than a diameter of a respective one of said light spots.
25. An information apparatus comprising:
means for reading out unit data in a one-dimensional format from an
information source;
means for converting said unit data into a two-dimensional data arrangement
of n rows.times.m columns, wherein said unit data is expressed by a bit
arrangement representing presence or absence of a bit on the n rows and m
columns, n and m being integers of at least two;
means for reading out bit data serially for each of said m columns;
light source means for emitting m beams of light in accordance with the
serially read out bit data of said m columns; and
optical means for converging said light beams from said light source means
and forming m light spots on a disk plane;
wherein said unit data is recorded as m columns of one-dimensional data
columns on a single track by said m beams of light on said disk plane as a
group of optically distinguishable information identifiers on a
two-dimensional area having n rows and m columns; and
wherein a distance between adjacent light spots of said m columns on said
single track in a track radial direction of the disk plane is smaller than
a diameter of a respective one of said adjacent light spots.
26. An information recording method, comprising the steps of:
reading out unit data in a one-dimensional format from an information
source;
converting the unit data into a two-dimensional data arrangement of n
rows.times.m columns, wherein the unit data is expressed by a bit
arrangement representing a presence or absence of a bit in the n rows and
m columns, n and m being integers of at least two;
reading out the bit data serially for each of the m columns;
emitting m beams of light in accordance with the serially read out bit data
of the m columns; and
converging the light beams so as to form m light spots on a disk plane and
recording the unit data as m columns of one-dimensional data columns on a
single track by said m light spots on the disk plane as a group of
optically distinguishable information identifiers on a two-dimensional
area having n rows and m columns;
wherein a distance between adjacent light spots of said m columns on said
single track in a track radial direction of the disk plane is formed to be
smaller than a diameter of a respective one of said adjacent light spots. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
The present invention relates to an optical information processing
apparatus, and more specifically, relates to an information
recording/reproducing apparatus and a method such as an optical disk.
Up to the present practical use stage since the basic recording/reproducing
system has been proposed, in the conventional optical disk, data are
recorded in a time sequential mode on the concentric track thereof along
the circumferential direction, which is similar to the conventional
magnetic recording apparatus with utilizing magnetic force. The intervals
of the adjoining tracks are set in order that data interference (referred
to as a "crosstalk") among the respective tracks may be eliminated and
thus no correlation of the data is present between the adjoining tracks.
There are conventional techniques for increasing the recording densities of
the optical disks as described in, for instance, JP-A-2-53223.
Higher recording densities are continuously required for the information
recording/reproducing apparatuses. To this end, in accordance with the
conventional magnetic recording systems, the track intervals and the bit
densities in the circumferential direction have been separately improved,
whereby the recording plane densities could be increased. Similarly, a
similar improving approach has been taken in the optical disk.
Since the resolution in the circumferential direction and the radial
direction with respect to the conventional magnetic heads is asymmetrical
with each other, there is a considerable difference between the track
density and the bit density, e.g., approximately 10 times difference
therebetween. However, since the spots used for the data
recording/reproducing operations represent a isotropic characteristic in
the optical disk, the track density is substantially equal to the line
density. Nevertheless, even when the shape of the light spot are
isotropically made small in order to increase the densities, although the
line density may be improved, the track intervals could not be improved,
as compared with the improvement in the line density. This is because
there are many factors of the spot positional variations along the radial
direction. As a result, the amount of variations becomes large and it is
difficult to narrow the track intervals.
SUMMARY OF THE INVENTION
It is an object of the present invention to achieve higher densities of
information recorded on an optical disk.
To achieve this object, the isotropic characteristic of the optical disk
which is superior to the conventional recording apparatus is actively
utilized.
To achieve the above-described object, an information recording/reproducing
apparatus according to the present invention, comprises:
buffer means for storing therein consecutive recording data in a unit of
two-dimensionally conversion;
converting means for converting said consecutive recording data into nxm
two-dimensional data arrangements corresponding to said unit of data;
recording means having m pieces of light sources, for subdividing said
n.times.m two-dimensional data arrangements into m columns of
one-dimensional data columns so as to be read out; and for controlling
said m pieces of light sources in accordance with said data columns; and
optical means for converging luminous fluxes from said m pieces of light
sources and for forming m pieces of spots n a disk plane;
said recording data are recorded on said disk plane as an optically
distinguishable information identifier group having n.times.m
two-dimensional extended areas.
Also, an information recording/reproducing apparatus, according to the
present invention, for reproducing data which have been recorded by way of
a recording method for converting consecutive data into data having mxn
two-dimensionally extended areas, and for recording said converted data on
an optical disk as an optically distinguishable pit group, comprises:
m pieces of light sources;
optical means for converting luminous fluxes from said "m" pieces of light
sources and for forming "m" pieces of spots on a plane of the optical
disk;
positioning means for positioning said "m" pieces of spots onto said pit
group on the disk plane;
"m" pieces of detecting means for detecting light reflected from said pit
group corresponding to each of the spots;
generating means for generating "m" columns of one-dimensional data series
from the reflection light detected by the respective detecting means, and
also for generating nxm two-dimensional data by combining "n" pieces of
said one-dimensional data series; and
demodulating means for demodulating the consecutive data from said nxm two
dimensional data.
An information recording/reproducing method, according to the present
invention, comprises the steps of:
coding recorded information into two-dimensional information;
converting said two-dimensional information into a one-dimensional
information arrangement;
modulating a plurality of laser light sources with employment of said
information arrangement so as to record two dimensional codes on a disk
plane;
reproducing said two dimensional information with employment of a plurality
of laser light sources;
photo-electrically converting the reproduced signal;
detecting a one-dimensionally arranged signal from the photo-electrically
converted signal; and
decoding two dimensional information by employing these signals.
Furthermore, an information recording/reproducing method, according to the
present invention, comprises the steps of:
storing consecutive recording data in a unit of two dimensional conversion;
coding said consecutive data to n.times.m two-dimensional data series;
subdividing said n.times.m two-dimensional data series into "m" columns of
one-dimensional data series so as to be read out, and controlling "m"
pieces of light sources in accordance with these data series;
converging luminous fluxes from said "m" pieces of light sources so as to
form "m" pieces of spots on a disk plane;
recording on said disk plane, data to be recorded thereon as an optically
distinguishable pit group having n.times.m two-dimensionally extended
areas;
positioning said "m" pieces of spots on said pit group on the disk plane;
detecting light reflected from said pit group corresponding to each of the
spots;
generating "m" columns of one-dimensional data series from the reflected
light detected by said detecting steps and combining with each other "n"
pieces of said data so as to generate n.times.m two-dimensional data; and
decoding consecutive data from said n.times.m two-dimensional data.
In accordance with the present invention, the data to be recorded is
subdivided and the subdivided data are coded in order to correspond to the
two dimensional arrangement, but not to correspond to the one dimensional
arrangement effected as in the conventional coding operation.
During the recording operation, the two dimensional arrangement is
subdivided into a plurality of one dimensional arrangements. A plurality
of light sources corresponding to the two dimensional arrangement are
employed so as to converge the luminous fluxes from these light sources
onto the disk plane, whereby a plurality of spots are formed. In response
to the respective one-dimensionally arranged data, the respective light
sources are modulated so that the optically distinguishable pit group
having the two-dimensionally extended areas in the radial and
circumferential directions is recorded on the disk plane.
During the reproducing operation, the luminous fluxes from a plurality of
light sources are converged and a plurality of spots are formed on the
disk plane, the above-described spot group is positioned on the optically
distinguishable pit group having the two-dimensionally extended areas, and
ten either the reflection light or the transmission light which has been
modulated by the above pit group is detected, depending upon the
respective spots. The one dimensional data arrangement corresponding to
the trials of the respective spots is produced with employment of the
detected time sequential signals, and also one set of data corresponding
to the set of plural one-dimensional arrangements is decoded, so that the
information recorded on the disk is read out therefrom.
In accordance with the present invention, since the data are recorded by
utilizing a plurality of spots within one time, the amount of positional
variations for the spots in the radial direction among the respective
one-dimensional arrangements may be reduced. Also, even when the intervals
among the one-dimensionally arranged data are narrowed, the data may be
surely detected by the two dimensional arrangement, taking account of the
signal process during the detecting (reproducing) operation.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and advantages of the present invention will become
apparent by reference to the following description and accompanying
drawings wherein:
FIG. 1 is an explanatory diagram for showing two-dimensionally arranged pit
groups on an optical disk according to one embodiment of the present
invention;
FIG. 2 is an explanatory diagram for representing two-dimensionally
arranged pit groups according to the present invention;
FIG. 3 is an explanatory diagram for showing the recorded pit groups;
FIG. 4 is a coding list for forming a two dimensional arrangement;
FIG. 5 is a schematic block diagram for representing a signal recording
system;
FIG. 6 represents a pattern diagram, for a synchronizing mark used for
producing a clock;
FIGS. 7 and 8 are schematic block diagrams for showing a data reproducing
system;
FIG. 9 is an explanatory diagram for indicating a two dimensional
arrangement corresponding to 5-bit recording data;
FIGS. 10A to 10D are explanatory diagrams for representing two dimensional
arrangements corresponding to 7-bit recording data;
FIGS. 11 and 12 are schematic block diagrams for showing a reproduction
processing system in case of strong crosstalk between one-dimensional
arrangements;
FIGS. 13A and 13B are schematic block diagrams of another reproduction
processing system different from that of FIG. 12;
FIG. 14 is an explanatory diagram for showing a pit arrangement to reduce
crosstalk;
FIGS. 15A, 15B and 15C represent relationships between the pit intervals
and the signal outputs;
FIGS. 16A and 16B are constructive arrangement of an optical system for
forming two spots;
FIGS. 17A and 17B are schematic block diagrams for explaining a method for
detecting a control signal derived from the optical system to form the two
spots;
FIGS. 18A, 18B and 18C illustrate rules of coding operations employed in
the preferred embodiments;
FIG. 19 is an explanatory diagram for showing another preferred embodiment
in which 7 crosspoints of the recording blocks have been formed in the
track direction and 8 crosspoints thereof have been formed in the radial
track direction;
FIG. 20 is an explanatory diagram for showing a relationship between
recording reproducing spots and pit groups; and,
FIG. 21 illustrates an overall system diagram according to the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now FIGS. 1 and 21, an optical information recording/reproducing
system of the present invention will be summarized. AS shown in FIG. 1,
data to be recorded are converted in two dimensional 4.times.2 data and
are recorded under 4-line/2-column pits state in this preferred
embodiment.
In accordance with this preferred embodiment, serial (consecutive)
recording information 901 are subdivided in a unit of 8 (4.times.2) during
a recording operation; this information is coded as a two-dimensional
arrangement of 4 lines and 2 columns (902); this information is further
converted this information is further converted into a one-dimensional
information arrangement in which the 4-line/2-column arrangement is
handled as one column and then read (903); a laser 905 is modulated based
on this one-dimensional information arrangement (904); and furthermore the
laser light is converged at a predetermined position by an optical system
906 so that pits 908 and 909 are formed in two columns on an optical disk.
During the reproducing operation, the laser light emitted from the laser
905 is collected by an optical system 906 to the pits; light reflected
from the pits is received by a light receiver 910, and
photoelectric-converted (911) into a corresponding signal; a
one-dimensional arrangement signal is detected from this
photoelectric-converted signal (912); and a two-dimensional code is
obtained from this detection signal and then decoded so as to reproduce
consecutive information (914).
A more concrete arrangement of the present invention will now be described.
In FIG. 2, there is shown a basic coding pattern of a pit group which is
formed on a disk plane in accordance with the present invention and is
optically discriminatable, as one preferred embodiment. For the sake of
explanation, a coding pattern constructed of 2 lines and 2 column will now
be described as a first example. As shown in FIG. 2, a grid constructed of
4 vertical lines and 4 horizontal lines is handled as one "block". Data is
represented in such a manner that whether or not a round hole pit 30 is
present at four grid points (i.e., points where the grids intersect with
each other). With such an arrangement, since there are four grid points
within 1 block, the possible data arrangements become 2.sup.4, namely
4-bit data may be expressed. It should be noted that examples
corresponding to the recording data are shown under the respective
figures. The two-dimensional coding according to this preferred embodiment
implies that the recording data correspond to the patterns arranged in a
plane, as represented in FIG. 2
FIG. 3 is an explanatory diagram for showing the above-described pits which
have been recorded on the disk. The data arrangement along a circular
direction of the disk (arrow direction) is such that the above-described
blocks 1 to 18 are arranged along the circular direction as represented by
a dot and dash line. Gaps with equiintervals are formed in order that the
spaces between the respective blocks along the track, direction can be
recognized as the block spaces. Data are recorded among the guide grooves
20, 21, 22 and 23 of the normal consecutive servo system. A track shift
signal for positioning a recording spot is detected by utilized
diffraction emitted from the guide groove with employment of the normal
track shift detecting method.
Although the pits overlapped with each other in the above-described
preferred embodiment, the pits may be alternatively formed in such a
manner that they don't overlapped with each other. In this case, although
line density becomes coarse, a complex signal processing system is not
required to reproduce the recorded signals. Moreover, since a plurality of
pit columns may be recorded within one time, the track pitches may be
narrowered by the variations in the track shifts, as compared with the
conventional method.
When the grid interval along the track radial direction is made smaller
than the diameter of the round hole, the pits may overlap with each other
among the two-dimensionally arranged patterns. That is, a respective round
hole pit is formed by a respective light spot of a light source and due to
the overlapping of the pits, the distance between adjacent light spots of
the pit columns on a single track in a track radial direction is smaller
than a diameter of a respective light spot. In this case, a rule of codes
must be established, taking account of the reproducing process. This rule
establishment: will be described later with reference to FIG. 18A.
To record the patters according to the present invention, a positional
:relationship between recording pits must be correctly controlled.
A consideration will now be made of a method for recording a pit group to
correctly control such a positional relationship. If such a conventional
method that one pit array is recorded on one array of the optical disk
every 1 rotation and subsequently another one pit array is recorded on the
adjacent one array, is employed in the present embodiment, the conditions
of the optical spot controls in the information recording/reproducing
apparatus are varied, whereby the positional relationship of the pits in
the track radial direction would be shifted.
Accordingly, a plurality of spots are employed in this embodiment, and the
above-described two-dimensionally arranged pit group is recorded within at
least one rotation period.
A concrete positional relationship of the spots is represented in FIG. 20.
In FIG. 20, circular portions covered with inclined lines indicate optical
spots 100 and 101, an axial line 102 to connect these spots is slightly
inclined with respect to the track circumferential direction, and these
optical spots are mutually shifted with respect to the track radial
direction due to this inclination. It is originally preferable to position
two spots in a close state. However, taking account of the characteristics
of the current semiconductor laser, the spot interval on the disk plane
should be selected to be greater than 10 microns. Considering both the
extending angle of the semiconductor laser and light utilization
efficiency, the numerical aperture of the lens for coupling light from the
semiconductor laser is from 0.15 to 0.3 approximately. Since the numerical
aperture of the object lens is not selected to be so large value due to
the characteristic of the disk substrate, it is about 0.5 to 0.6. As a
consequence, a lateral magnification of an overall optical system becomes
2 to 4. The emission interval of the current semiconductor laser is set to
larger than 50 .mu.m due to various reasons, for instance, prevention of
thermal interference. Also, since the grid interval must be smaller than
the conventional track pitches from 1.6 to 1.5 .mu.m, such an arrangement
that the spots are separated along the track circumferential direction may
be realized under the present technical level. This shift amount is
recognized as an interval of the above-described grid in the track radial
direction.
For the sake of explanation, in FIG. 20, there are shown the recorded
two-dimensional arrangements at the right hand track (track between the
grooves 21 and 22), and also the relationship between the optical spot and
pit in the recording step at the left hand track (track between the
grooves 20 and 21). It should be noted that the disk plate is rotated
along an arrow direction Pits 30', 31', 33', 35', 36' which have been
recorded and through which the recording spot 101 has already passed, are
indicated by a solid line. Pits which will be recorded are indicated by a
dot line.
Although the same block is not simultaneously recorded in this spot
arrangement, the recording operation is completed after a time difference
corresponding to the spot interval along the track circumferential
direction, namely the same one rotation period.
To form the two dimensional arrangement, illumination strengths of the
respective recording spots are modulated in response to the data on the
one-dimensional arrangement and the pits are recorded in one dimensional
manner along the track circumferential direction.
To convert this two-dimensional arrangement into the one-dimensional
arrangement corresponding to the respective recording spots, a
predetermined coding list is employed. A coding list corresponding to the
two-dimensional arrangement shown in FIG. 2 is indicated in FIG. 4. This
coding list is inputted into a ROM (read-only memory) and based upon the
data to be recorded, data for realizing the two-dimensional arrangement
corresponding to these data to be recorded are retrieved. To obtain
one-dimensional arrangement for modulating plural light sources (two light
sources in an example shown in FIG. 4) based on this data, since the
above-described data correspond to 4-bit data as shown in FIG. 4, the
upper two bits correspond to the one-dimensional arrangement for
modulating the light sources by which the preceding spots have been
formed, whereas the lower 2 bits correspond to the one-dimensional
arrangement for modulating the light sources by which the succeeding spots
have been formed. Furthermore, the sequential number at the one
dimensional arrangement is first defined from the upper bit of the
above-described data.
Operation of the recording signal processing system with employment of such
a coding list will now be described with reference to FIG. 5. Data 110 to
be recorded is inputted into a latch circuit 111 and stored in response to
a latch control signal 112 every 4 bits. This 4-bit data is inputted into
a ROM 113 so as to retrieve 4-bit data for realizing a two-dimensional
arrangement. The retrieved data 114 is stored in a latch circuit 116 in
response to another latch control signal 115. The lower bit data of this
data 114 is read out in response to a first clock signal 117 and then
stored into a shift register 118 having a finite length in synchronism
with a clock signal 117. Also, the upper bit data of this data 114 is read
out in accordance with a second clock signal 119, and is stored into a
shift register 120 having a length longer than that of the above-described
shift register 118 is synchronism with a clock signal 119. Outputs of
these shift registers 118 and 120 are connected to each of modulators 121
ad 122, and thus binary-coded signals derived from the shift registers 118
and 120 are converted into analog signals 123 and 124 for modulating the
emission strengths of the lasers. In this case, the emission waveforms of
the optical pulses are controlled in order to control the shapes of the
recorded pits. For instance, to stably record the round pits shown in FIG.
1, since such a recording method is known that the optical pulses more
shorter than the clock of data are employed with high emission power, such
a control is performed. Furthermore, the modulators perform such a complex
waveform control that the recording power is increased during a certain
period of the record starting period, depending upon the line speed and
recording medium.
In response to signals 123 and 124 from the modulators, laser drive
circuits 125 and 126 are driven in order to modulate the emission power
obtained from light so | | |
