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Full text of "USPTO Patents Application 10670332"

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J 



Europaisches Patentamt 
European Patent Office 
Office europeen des brevets 



(fj) Publication number : 0 556 046 A1 



EUROPEAN PATENT APPLICATION 



@ Application number: 93300996.1 
(g) Date of filing : 11.02.93 



@ int. ci. 5 : G11B 7/125, G11B 7/00 



(so) Priority : 14.02.92 JP 28457/92 

(43) Date of publication of application : 
18.08.93 Bulletin 93/33 

(S) Designated Contracting States : 
DE FR GB 

© Applicant : SONY CORPORATION 

7-35, Kitashinagawa 6-chome Shinagawa-ku 
Tokyo (JP) 



(72) Inventor : Koike, Shigeaki Sony Corporation 
7-35, Kitashinagawa 6-chome 
Shinagawa-ken, Tokyo (JP) 

(74) Representative : Nicholls, Michael John 

J.A. Kemp & Co., 14, South Square, Gray's Inn 
London WC1R 5LX (GB) 



(54) Recording and reproducing apparatus for optical disk. 



CD 
CD 



(57) To determine the optimum recording light 
amounts for all recordable region of each opti- 
cal disk in a relatively short time information is 
recorded on the try-to-write region 4 on the 
inside of the innermost periphery of the rewrit- 
able region 2 of the optical disk 1 while rotating 
it at linear velocities equal to those at least at 
two positions (radii R1, R2) in the radius direc- 
tion A within the rewritable region 2, and the 
optimum recording light amounts are 
measured. Then, the optimum recording light 
amounts for all velocities in the rewritable reg- 
ion 2 are determined by an interpolation or 
extrapolation processing 26 of the measured 
optimum recording light amounts at the two 
velocities. 



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This invention relates to an apparatus and meth- 
od for recording optical disks, both those suitable for 
recording and reproduction, for example, reversible- 
type optical disks capable of being repetitively record- 
ed and reproduced, or write-once type disks. 

When recording such disks, pits (or marks) are 
formed on a repetitively recordable and reproducible 
optical disk, or a write-once read-many type optical 
disk, and the amount of laser light to be irradiated on 
the optical disk, the amount of recording light, has to 
be maintained to be a proper value. This is because 
the recorded pits are required to have a uniform 
shape and a high density in order to reduce error 
upon reproduction and improve the recording density. 

According to the prior art, in order to set the 
amount of recording light at a proper value, a "try-to- 
write" region is prepared on a track within a predeter- 
mined user's recordable region of the optical disk, 
and the user confirms the proper amount of recording 
light within this try-to-write region. 

When information is recorded at the confirmed 
proper amount of recording light, the recording den- 
sity of a recorded region near the try-to-write region 
can be improved since a relatively small error occurs 
upon reproduction. 

However, when a video signal is recorded over 
the whole disk, i.e. the innermost to outermost per- 
iphery of the user's recordable region of the optical 
disk, the amount of recording light, even if it is set to 
be a proper value within the try-to-write region as 
mentioned above, diverges from the proper amount at 
other tracks away from that region because the linear 
velocity of the recording medium (which depends on 
the radius of the track) is considerably different from 
that within the try-to-write region. This limits the high- 
density recordability. 

Increasing the amount of testing, however tends 
to occupy more time and thus be inefficient. Also, al- 
though it has been proposed to provide a test area in 
every sector and test at every radius (e.g. in comput- 
ers WD2000 and WD3000) this reduces the amount 
of available storage area and so is unsuitable for vid- 
eo disks where more data is generally stored than on 
a computer disk. 

This invention, in view of this problem,-is to pro- 
vide an apparatus and method for recording optical 
disks which are capable of determining the optimum 
recording conditions of the user's recordable region 
of individual optical disks in a relatively short time. 

According to this invention, there is provided opt- 
ical disk recording apparatus comprising: 

a disk drive for rotating an optical disk; 

a light source for recording data on the optical 

disk; 

recording light amount control means for con- 
trolling the amount of light emitted by the light source 
to record the data; 

reproduction means for reproducing the data 



to produce a reproduced signal; 

system control means for controlling said light 
source and light amount control means to record test 
data in a predetermined test region of the disk and the 
5 reproduction means to reproduce it and for setting the 
recording light amount to be used in accordance with 
the reproduced test data; 

characterized in that the system control means is 
adapted to control the disk drive to rotate the disk dur- 

10 ing recording of first and second test data at respec- 
tive first and second different angular velocities such 
that the linear velocities of the test region at said first 
and second angular velocities are equal to the linear 
velocities of two different radial positions of the disk 

15 during information recording, and to determine re- 
spective first and second optimized recording light 
amounts in accordance with the reproduced first and 
second test data; and in that the system control 
means comprises computing means for computing 

20 light recording amounts for all other desired radial 
positions on the disk from the first and second opti- 
mized recording light amounts. 

There is also provided an optical disk recording 
method comprising the steps of:- 

25 recording test data on a test region of an optical 

disk using a light source; 

reproducing the test data; and 
setting the recording light amount of the light 
source according to the test data; characterized by: 

30 rotating the disk during recording of first and 

second test data at respective first and second differ- 
ent angular velocities such thatthe linear velocities of 
the test region undergoing recording are equal to the 
linear velocities of two different radial positions of the 

35 disk during information recording; 

determining respective first and second opti- 
mized recording light amounts in accordance with the 
reproduced first and second test data; and 

computing light recording amounts for all other 

40 desired radial positions on the disk from the first and 
second optimized recording light amounts. 

Thus with the invention, information may be re- 
corded on the try-to-write region on the inside of the 
innermost periphery of the user's recordable region 

45 of the optical disk while rotating it at the first and sec- 
ond linear velocities equal to those at two points in the 
radius direction of the user's recordable region and 
with first and second amounts of recording laser 
beam under the control of the recording light amount 

50 control means. Then, the first and second recording 
light amounts optimized at the first and second linear 
velocities in the try-to-write region of the optical disk 
can be obtained by the reproduction means 22, com- 
paring means 23 and optimizing means 25. Also, the 

55 values of the optimum recording light amounts at all 
points in the radius direction in the recordable region 
are determined by computing means on the basis of 
the optimized first and second recording light 



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amounts. Therefore, the optimum recording light 
amount for all points in the user's recordable region 
of each optical disk can be determined in a relatively 
short time. 

The computing means may determine the other 
recording light amounts by interpolation and/or ex- 
trapolation based on a function selected according to 
the properties of the disk, e.g. selected to model the 
properties of tested disks. 

The invention is applicable to write-once disks as 
well as rewritable disks. 

The invention will be further described by way of 
example only with reference to the accompanying 
drawings, in which:- 

Figure 1 is a diagram of the construction of the 
optical disk recording and reproducing apparatus 
of one embodiment of the optical recording appa- 
ratus of the invention; 

Figure 2 is a plan view of the optical disk of the 
optical disk recording and reproducing apparatus 
shown in Fig 1; 

Figure 3 is a diagram showing the contents of the 
velocity command table stored in the system con- 
troller of the optical disk recording and reproduc- 
ing apparatus shown in Fig. 1; 
Figure 4 is a waveform diagram to which refer- 
ence is made in explaining the operation of the 
optical disk recording and reproducing apparatus 
shown in Fig 1; 

Figure 5 is a flowchart to which reference is made 
in explaining the operation of the optical disk re- 
cording and reproducing apparatus shown in Fig 
1; and 

Figure 6 is a graph showing the optimum record- 
ing light amount characteristic obtained by the 
optical recording and reproducing apparatus 
shown in Figure 1 . 

An illustrative embodiment of the optical disk re- 
cording apparatus to which the optical disk recording 
method of the invention is applied will now be descri- 
bed with reference to the drawings. 

Figure 1 is a schematic diagram of an embodi- 
ment of the optical disk recording apparatus of the in- 
vention. Figure 2 is a plan view of an optical disk to 
be recorded by this apparatus. 

Referring to Figs 1 and 2, there is shown an opt- 
ical disk 1. This optical disk 1 has a rewritable region 
2 as the user's recordable region. This rewritable re- 
gion 2 is an annular region extending from radius R : 
to R 2 . A try-to-write region 4 is formed on the inside 
of the innermost periphery of the rewritable region 2. 
This try-to-write region 4 is an annular region extend- 
ing from radius R 0 to R v The type of optical disk 1 is 
not limited to the rewritable optical disk, but may be a 
write-once type optical disk. 

An optical pickup 5 is located to face the disk sur- 
face of this optical disk 1 in order to write pits or read 
the recorded pits. The optical pickup 5 has an object 



lens 6 and a mirror 7, and it is moved along a guide 
rail 8 in the radius direction A of the optical disk 1 by 
a feeding mechanism that is formed of a feeding mo- 
tor 9 and so on. 

5 The position of the optical pickup 5 in the radius 

direction A, or the radius R is read as radius data D R 
by an encoder connected to the rotating shaft of a 
spindle motor 3. The radius data is supplied to a sys- 
tem controller 10. The system controller 10 responds 

10 to the radius D R from the encoder to control the feed- 
ing mechanism so that the optical pickup 1 can be 
moved to a predetermined radius R specified by the 
radius- position specifying data which the system con- 
troller 10 itself generates. 

15 This optical disk 1 is rotated at a constant angular 

velocity (CAV) by the spindle motor 3 under the con- 
trol of a speed command signal S v from the system 
controller 10. Therefore, since the linear velocity LV 
at a predetermined radius R is determined by the 

20 product of the radius R and the angular velocity, it is 
proportional to the radius R. Fig. 3 shows the con- 
tents of a velocity command table 11 stored in the sys- 
tem controller 10 in association with this velocity 
command signal S v . 

25 As shown in Fig. 1, a fixed optical system 12 is 

optically connected to the pickup 5 that is moved in 
the radius direction A. The fixed optical system 12 has 
a laser diode 13 which is controlled to emit a laser 
beam according to the optical modulation system. 

30 The laser diode 13 is connected to a recording light 
amount control circuit 15 as the means for controlling 
the amount of recording light. This recording light 
amount control circuit 15 supplies a recording signal 
S 2 (see Fig. 4B) of a modulating current signal to the 

35 laser diode 1 3. The amplitude of the recording signal 
S 2 is determined by a control signal S 3 that is fed from 
the system controller 10. The on-period and off-peri- 
od of the recording signal S 2 are determined by a bi- 
nary reference recording signal S-, (see Fig 4A) that 

40 is fed from a reference recording signal generating cir- 
cuit 16. 

The laser diode 1 3 emits a laser beam of intensity 
proportional to the recording signal S 2 that is fed from 
the recording light amount control circuit 15. The laser 

45 beam emitted from the laser diode 13 iscollimated by 
a collimator lens 14, and then passed through a beam 
splitter 16 to a mirror 7, from which the laser beam is 
reflected at right angles. The collimated laser beam 
reflected from the mirror 7 is again converged by an 

50 object lens 6 and irradiated on the optical disk 1. 
Thus, the optical disk 1 is recorded in cooperation 
with a magnetic circuit not shown to form recorded 
pits (magnetized pits) thereon. 

On the other hand, the laser beam for reading is 

55 irradiated on the optical disk 1 and reflected from the 
optical disk 1 with the recorded pits. The reflected las- 
er beam is passed through the object lens 6, the mir- 
ror 7, the beam splitter 16 and a condenser 17 and in- 



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EP 0 556 046 A1 



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cident on a photodiode 21 . 

The output signal from the photodiode 21 is sup- 
plied to a reproduction circuit 22. When the output sig- 
nal from the photodiode 21 is supplied to the repro- 
duction circuit 22, the information recorded on the 
optical disk 1 is supplied therefrom as a reproduced 
signal S 4 (S 41 through S 43 ) (see Figs 4C through 4E) 
to a symmetry detecting circuit 23 as comparing 
means. 

The symmetry detecting circuit 23 supplies a 
duty-ratio data S 5 according to the reproduced signal 
S 4 to the system controller 10. 

The system controller 10 analyzes the duty-ratio 
data S 5 by an optimizing routine 25 as optimizing 
means which will be described in detail later. The ana- 
lyzed data as the control signal S 3 is supplied to the 
recording light amount control circuit 15. The control 
signal S 3 can be optimized by repetitive execution of 
this optimizing routine 25. 

The optimization of the control signal S 3 , or the 
optimization of the amount P of emitted light from the 
laser diode 1 3 is performed within the try-to-write re- 
gion 4 of the optical disk 1 . That is, in the try-to-write 
region 4, the control signal S 3 is optimized for, for ex- 
ample, the linear velocity LV^ at the innermost periph- 
ery, or radius R^ of the rewritable region 2 and for the 
linear velocity LV 2 at the outermost periphery, or ra- 
dius R 2 . The optimization for all positions in the radius 
direction within the rewritable region 2 is performed 
by the interpolation processing such as the linear in- 
terpolation according to an interpolation routine 26 or 
a predetermined functional interpolation. 

The predetermined function should be selected 
to be, for example, a function exhibiting the average 
characteristic of the characteristics (hereinafter refer- 
red to as the optimum recording light amount charac- 
teristics, if necessary) of the radius vs. optimum con- 
trol signal S 3 (corresponding to the optimum record- 
ing light amount) which are measured for CAV at all 
points in the radius direction A in reference tests, e.g. 
in which a plurality of optical disks 1 are rotated at a 
constant angular velocity (CAV). The function for in- 
terpolation may be function proportional to a half pow- 
er of the linear velocity LV. 

Thus when the optimum recording light amount is 
determined by two linear velocities at two positions in 
the radius direction within the rewritable region 2, the 
rewritable region between the radii corresponding to 
the two linear velocities can be determined by inter- 
polation processing, and the rewritable region other 
than that between the radii corresponding to the two 
linear velocities can be determined by extrapolation. 

The linear interpolation determines the optimum 
recording light amount from, for example, the linear 
velocity LV^ at the innermost radius R^ of the rewrit- 
able region 2 and the linear velocity LV 2 at the outer- 
most radius R 2 . The linear interpolation may deter- 
mine the optimum recording light amount from the lin- 



ear velocity LV 3 at a radius R 3 {R 3 = R^ (R 2 - R^/2) be- 
tween the radii, R^ and R 2 and the other two linearve- 
locities, or the three linear velocities LV 1t LV 2 and LV 3 . 
This linear interpolation using three linear velocities 

5 can provide a much higher precision than that using 
two linear velocities. 

The characteristics of the linear velocity LV vs. 
optimum control signal S 3 , or the optimum recording 
light amount characteristics determined by the inter- 

10 polation routine 26 are stored in an optimum recording 
light amount table 27. 

Therefore, the optical disk 1 can be recorded over 
all the rewritable region 2 by the optimum amount of 
recording light according to this optimum recording 

15 light amount table 27. 

The operation of this embodiment, particularly 
the optimizing routine 25 will be described in detail 
with reference to the flowchart of Fig. 5. 

After detecting that the optical disk 1 has been 

20 loaded on the shaft of the spindle motor 3, the system 
controller 1 0 controls the feeding motor 9 to move the 
optical pickup 5 in the radius direction A toward the 
centre and to position it at a point within the try-to-wri- 
te region 4, for example, at the radius R 0 (step S1 01). 

25 The radius data D R = Rq can be confirmed by the out- 
put data from the encoder of the feeding motor 9. 

Then, the system controller 1 0 refers to the veloc- 
ity command table 1 1 (see fig. 3) and supplies the ve- 
locity control signal Svtothe spindle motor 3, thereby 

30 controlling the motor to rotate the disk so that the lin- 
ear velocity at the radius Rq equals the recording lin- 
ear velocity ^ forthe radius R^ (step S102). The lin- 
ear velocity, LV 0 i at radius R 0 can be made coincident 
with the linear velocity LV., at radius R., by supplying 

35 the velocity signal Sv which satisfies the relation of 
LVoi=(Ri/R 0 ) LV 0 =LV 1 . 

The system controller 10 then sets the control 
signal S 3 to a certain value and supplies it to the re- 
cording light amount control circuit 15. In this case, 

40 the reference recording signal Si shown in Fig 4A is 
supplied from the reference recording signal generat- 
ing circuit 16 to the recording light amount control cir- 
cuit 1 5. Thus, the recording signal S 2 of which the am- 
plitude is determined by the control signal S 3 as 

45 shown in Fig4B is supplied to the laser diode 13. The 
laser beam modulated by the recording signal S 2 is ir- 
radiated from the laser diode 13 on the optical disk 1, 
recording pits thereon. Then, the reading laser beam 
is irradiated on the optical disk 1, and the reflected 

so laser beam from the recorded pits are read by the 
photodiode 21. The reproduction circuit 22 produces 
the reproduced signal S 4 (step S103). Examples of re- 
produced signals S 4 for different recording light 
amounts are shown in Fig 4C, D and E. (Although for 

55 simplicity the recording signals and optimum repro- 
duced signal are shown as symmetrical, in practice 
they may not be symmetrical but this can be allowed 
for in the subsequent detection circuitry). 



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The reproduced signal S 4 is supplied to the sym- 
metry detecting circuit 23. The symmetry detecting 
circuit 23 produces, for example, the duty ratio data 
S 5 (S 5 = B/A) of the period of the reference level V R 
to that of the maximum level V M ax of the reproduced 
signal S 4 , in which case the reference level is 1/2 the 
maximum level. The system controller 10 reads in this 
duty ratio S 5 (S 5 = B/A) (step S104), and decides 
whether the read-in duty radio data S 5 (S 5 = B/A) is 
50% (or whatever is optimum) (step S105). 

If it is not 50% (or optimum) at step 1 05, decision 
is further made of whether it is above 50% (step 1 06). 

In the case of signal S 41 where the recording light 
amount was too large, since the reproduced signal S 4 
is the reproduced signal S 41 shown in Fig. 4C, the ra- 
tio is 50% or below. In other words, the recording las- 
er beam based on the recording signal S 2 and which 
is generated from the laser diode 1 3 is found to be too 
intensive. Thus, the control signal S 3 is reduced in its 
intensity by a predetermined amount and that inten- 
sity-reduced control signal S 3 is fed to the recording 
light amount control circuit 1 5 so that the control sig- 
nal S 2 is reduced by a predetermined amount (step 
S107). 

If the reproduced signal S 4 produced from the re- 
production circuit 22 is a reproduced signal S 42 as 
shown in Fig. 4 E, the duty ratio data S 5 (S 5 = B/A) fed 
to the system controller from the symmetry detecting 
circuit 23 is 50% or above. In this case, the control 
signal S 3 is increased by a predetermined amount, 
and the intensity- increased control signal S 3 is sup- 
plied to the recording light amount control circuit 15, 
thus increasing the recording signal S 2 by a predeter- 
mined amount (step S108). 

When the duty ratio data S 5 (S 5 = B/A) reaches 
50% after repetition of steps S1 03 through step S 108, 
the reproduction circuit 22 produces the reproduced 
signal S 4 as a reproduced signal S 42 which is, as 
shown in Fig. 4D, substantially symmetric with re- 
spect to the intersection, F between the reference 
level V R and the reproduced signal S 4 . When the re- 
corded information is reproduced on the basis of the 
reproduced signal S 4 of which the duty ratio data S 5 
(S 5 = B/A) is 50%, it has the minimum loss of data. In 
this case, little error occurs, thus improving the reli- 
ability. 

In this way, the decision at step S105 is "yes", 
and the value of the optimum control signal S 3 is de- 
termined under the condition that the linear velocity 
at radius Rq within the try-to -write region 4 is equal 
to the linear velocity LVi at radius R 1f or LV 01 =(R 1 /R 0 ) 
LV 0 = LvV This value is also stored in memory means, 
though not shown, within the system controller 10 
(step S109). 

Similarly, the value of the optimum control signal 
S 3 is determined under the condition that the linear 
velocity at radius R 0 is equal to the recording linear 
velocity LV 2 for radius R 2 , or LV 02 = (R 2 /Ro) LV 0 = LV 2 . 



This value is also stored in memory means, though 
not shown, within the system controller 10. 

Then, in use, the system controller 10 can deter- 
mine the values of the optimum control signal S 3 for 

5 all linear velocities LV (i.e. all radii) in the rewritable 
region 2 by interpolation processing according to the 
interpolation routine 26. 

Fig 6 shows a curve of the optimum control signal 
S 3 determined by this interpolation processing, or an 

10 optimum recording light amount characteristic 30. 
This shows a functional interpolation between the op- 
timum recording light amount P1 associated with the 
optimum control signal S 3 determined at the linear ve- 
locity LV 0 i corresponding to linear velocity LV^ and 

15 the optimum recording light amount P2 associated 
with the optimum control signal S 3 determined at the 
linear velocity LV 02 corresponding to linear velocity 
LV 2 . A curve may by more suitable than straight linear 
interpolation for certain types of disk, e.g. MO disks 

20 with low melting and Curie temperature. 

Thus, according to this embodiment, when infor- 
mation is recorded on the try-to-write region 4 on the 
inside of the innermost periphery of the rewritable re- 
gion 2 of the optical disk 1 in order to determine the 

25 optimum recording light amount in the rewritable re- 
gion 2, the optical disk 1 is rotated at linear velocities 
LV 0 i, LV 02 corresponding to the linear velocities LV 1? 
LV 2 at least at two radii, for example, R 1p R 2 of the re- 
writable region 2 in the radius direction of the optical 

30 disk 1. Under this condition, the optimum recording 
light amounts and P 2 are measured, and the values 
of the optimum recording light amount at all points 
within the rewritable region 2 of the optical disk 1 are 
determined by the interpolation or extrapolation proc- 

35 essing according to the interpolation routine 26. 
Therefore, the values of the optimum recording light 
amount for all linear velocities LV in the rewritable re- 
gion 2 of each optical disk 1 can be determined in a 
relatively short time. 

40 This invention is not limited to this embodiment, 

but of course may take other various constructions 
without departing from the scope of the invention as 
defined by the claims. 

45 

Claims 

1. Optical disk recording apparatus comprising: 

a disk drive (3) for rotating an optical disk 

50 (2); 

a light source (13) for recording data on 
the optical disk (1); 

recording light amount control means (1 5) 
for controlling the amount of light emitted by the 
55 light source (1 3) to record the data; 

reproduction means (17 - 23) for reproduc- 
ing the data to produce a reproduced signal (54); 

system control means (10) for controlling 



5 



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said light source (13) and light amount control 
means (1 5) to record test data in a predetermined 
test region (R 0 ) of the disk (1) and the reproduc- 
tion means (1 7 - 23) to reproduce it and for setting 
the recording light amount to be used in accor- 5 
dance with the reproduced test data; character- 
ized in that the system control means (10) is 
adapted to control the disk drive (3) to rotate the 
disk during recording of first and second test data 
at respective first and second different angular 10 
velocities such that the linear velocities of the 
test region (Rq) at said first and second angular 
velocities are equal to the linear velocities of two 
different radial positions (Ri,R 2 ) of the disk during 
information recording, and to determine respec- 15 
tive first and second optimized recording light 
amounts in accordance with the reproduced first 
and second test data; and in that the system con- 
trol means (10) comprises computing means for 
computing light recording amounts for all other 20 
desired radial positions on the disk (1) from the 
first and second optimized recording light 
amounts. 



pendent therefrom, or a method according to 
claim 2, or 3 when dependent therefrom, wherein 
the optimized recording light amounts are deter- 
mined by a recursive process of recording the test 
data, reproducing it and adjusting the recording 
light amount and repeating as necessary. 

5. Apparatus according to claim 1, or 3 or 4 when de- 
pendent therefrom, or a method according to 
claim 2, or 3 or 4 when dependent therefrom, 
wherein the disk (1) is rotated at the first angular 
velocity to determine the optimal first recording 
light amount and then rotated at the second an- 
gular velocity to determine the optimal second re- 
cording light amount. 

6. Apparatus according to claim 1 , or 3, 4 or 5 when 
dependent therefrom, or a method according to 
claim 2, or 3, 4 or 5 when dependent therefrom, 
wherein test data is also recorded while rotating 
the disk (1) at a third angular velocity to deter- 
mine a third recording light amount correspond- 
ing to a third radial position of the disk. 



2. An optical disk recording method comprising the 
steps of:- 

recording test data on a test region (Rq) of 
an optical disk using a light source; 
reproducing the test data; and 
setting the recording light amount of the 
light source according to the test data; character- 
ized by: 

rotating the disk during recording of first 
and second test data at respective first and sec- 
ond different angular velocities such that the lin- 
ear velocities of the test region (Rq) undergoing 
recording are equal to the linear velocities of two 
d if ferent radial positions (R^ , R 2 ) of t he d isk duri ng 
information recording; 

determining respective first and second 
optimized recording light amounts in accordance 
with the reproduced first and second test data; 
and 

computing light recording amounts for all 
other desired radial positions on the disk from the 
first and second optimized recording light 
amounts. 

3. Apparatus according to claim 1 or a method ac- 
cording to claim 2 wherein the said linear veloci- 
ties of two different radial positions correspond to 
t he I i near velocities of t he portions of t he d isk (1 ) 
substantially at the inner and outer peripheries 
(Ri,R 2 ) of the user's recordable region when the 
disk (1) is rotated at the angular velocity for infor- 
mation recording. 

4. Apparatus according to claim 1, or 3 when de- 



25 7. Apparatus according to claim 1 , or 3 - 6 when de- 
pendent therefrom, or a method according to 
claim 2, or 3 - 6 when dependent therefrom, 
wherein the light recording amounts for all other 
desired radial positions are computed by interpo- 

30 lation or extrapolation from the determined re- 

cording light amounts. 

8. An apparatus or method according to claim 7 
wherein the interpolation or extrapolation is line- 

35 ar. 

9. An apparatus or method according to claim 7 
wherein the interpolation or extrapolation is 
based on a function of the half power of the linear 

40 velocity of the recording region of the disk. 

10. An apparatus or method according to any one of 
the preceding claims wherein the test data com- 
prises a square wave (S^ and the optimization of 

45 the recording light amount comprises monitoring 

the duty ratio of time periods (A,B) above and be- 
low a reference level in the reproduced signal 
(S 4 ). 

50 



55 



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EP 0 556 046 A1 




EP 0 556 046 A1 





8 



EP 0 556 046 A1 



Wareforms of Recording Signal 
and Reproduced Signal 



FIG. UA 

Reference Recording 
Signal 

FIG. UB 

Recording Signal 



FIG. 4C 



Reproduced Signal 
(Large Light Amount) 



FIG. UD 



Reproduced Signal 
(Optimum Light Amount) 



Si 



FIG. UF 



Reproduced Signal 
(Small Light Amount) 



_f 



S 2 



i i i 

i i i 

l i i 

I i i 





— Vr 



Vmax 



9 



EP 0 556 046 A1 



FIG. 5 



Yes 




Determine linear 
velocity 



Record and 
reproduce 



^ read in 



S101 



S102 



S103 
.S10A 




5105 



S106 
Yes 



S3 decrease ( light 
amount decrease) 



S108 



S3 increase 
(light amount 
increase ) 



I 



5109 



Store LV 
and S3 



c 



End 



10 



EP 0 556 046 A1 



FIG. 6 



Optimum Recording Light 
Amount Table 




30 Optimum Recording 
Light Amount 
Characteristic 



LVi 

Linear Velocity LV 



LV2 



11 



EP 0 556 046 A1 



European Patent 
Office 



EUROPEAN SEARCH REPORT 



Application Number 

EP 93 30 0996 



DOCUMENTS CONSIDERED TO BE RELEVANT 



Category 



X 
X 



Citation of document with indication, where appropriate, 
of relevant i 



EP-A-0 393 001 (IBM CORP) 

* the whole document * 

EP-A-0 126 682 (TH0MS0N-CSF) 

* abstract * 



Relevant 
to claim 



CLASSIFICATION OF THE 
APPLICATION (Int. CI.5 ) 



1-8,10 



1-5,7,8, 
10 



G11B7/125 
G11B7/00 



TECHNICAL FIELDS 
SEARCHED (Int. CI.5 ) 



G11B 



The present search report has been drawn up for all claims 



Place of fcearch 

THE HAGUE 



Dale of conpletioM of the uarck 

28 MAY 1993 



ANNIBAL P. 



CATEGORY OF CITED DOCUMENTS 

X ; particularly relevant if taken alone 

\ : particularly relevant if combined with another 

document of the same category 
A : technological background 
O : non-written disclosure 
P : intermediate document 



T : theory or principle underlying the invention 
E : earlier patent document, but published on, or 

after the filing date 
D : document cited in the application 
L : document dted for other reasons 

& : member of the same patent family, corresponding 
document 



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