Information recording method and information recording apparatus that can achieve uniform signal characteristics and overwriting characteristics over an entire surface of an optical disk mediu Number:7,426,166 from the United States Patent and Trademark Office (PTO) owispatent

Title: Information recording method and information recording apparatus that can achieve uniform signal characteristics and overwriting characteristics over an entire surface of an optical disk mediu

Abstract: In an information recording method and apparatus, when performing recording by using multiple pulses defined by erase powers Pe1 and Pe2 for forming a space part between mark parts, the set values of the erase powers Pe1 and Pe2 are updated at predetermined intervals in accordance with a recording linear velocity.

Patent Number: 7,426,166 Issued on 09/16/2008 to Yokoi

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Inventors:	Yokoi; Kenya (Kanagawa, JP)
Assignee:	Ricoh Company, Ltd. (Tokyo, JP)
Appl. No.:	10/875,167
Filed:	June 25, 2004

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Foreign Application Priority Data

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Jul 15, 2003 [JP]			2003-196865

Current U.S. Class:	369/59.11 ; 369/116; 369/47.5; 369/59.12
Current International Class:	G11B 5/09 (20060101)

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References Cited [Referenced By]

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U.S. Patent Documents

4984873	January 1991	Takiguchi et al.
5056896	October 1991	Iimura et al.
5732062	March 1998	Yokoi et al.
6426929	July 2002	Watabe et al.
6459666	October 2002	Yokoi
6487149	November 2002	Yokoi et al.
6600712	July 2003	Masui et al.
6664526	December 2003	Yokoi
6801240	October 2004	Abe et al.
2002/0071380	June 2002	Shimizu et al.
2002/0105875	August 2002	Ushiyama et al.
2002/0196324	December 2002	Abe et al.
2003/0090981	May 2003	Yokoi
2003/0156519	August 2003	Yokoi
2003/0189885	October 2003	Masui et al.
2004/0011945	January 2004	Yokoi

Foreign Patent Documents

	1 249 834		Oct., 2002		EP
	1 298 650		Apr., 2003		EP
	5-225570		Sep., 1993		JP
	5-274678		Oct., 1993		JP
	2707774		Oct., 1997		JP
	10-106008		Apr., 1998		JP
	2001-118245		Apr., 2001		JP
	2001-243626		Sep., 2001		JP
	2003-157536		May., 2003		JP
	WO 01/86642		Nov., 2001		WO

Primary Examiner: Tran; Thang V.
Assistant Examiner: Haley; Joseph
Attorney, Agent or Firm: Dickstein Shapiro LLP

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Claims

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What is claimed is:

1. An information recording method of performing recording on an optical disk medium having a recording layer on which mark information is recorded by a laser beam emitted in accordance with a waveform based on a recording pulse sequence, said information recording method comprising the steps of: performing recording while varying a recording clock cycle T in accordance with a variation in a recording linear velocity such that a recording linear density becomes substantially constant; and when performing recording by using multiple pulses defined by an erase power Pe1 and an erase power Pe2 as an erasing pulse for forming a space part between mark parts, updating set values of the erase power Pe1 and the erase power Pe2 at predetermined intervals in accordance with the recording linear velocity such that the difference between the erase power Pe1 and the erase power Pe2 is increased in accordance with an increase in the recording linear velocity.

2. An information recording method of performing recording on an optical disk medium having a recording layer on which mark information is recorded by a laser beam emitted in accordance with a waveform based on a recording pulse sequence, said information recording method comprising the steps of: performing recording while varying a recording clock cycle T in accordance with a variation in a recording linear velocity such that a recording linear density becomes substantially constant; when performing recording by using multiple pulses defined by an erase power Pe1 and an erase power Pe2 as an erasing pulse for forming a space part between mark parts, updating set values of the erase power Pe1 and the erase power Pe2 at predetermined intervals in accordance with the recording linear velocity; and updating set values of a coefficient .epsilon.1 and a coefficient .epsilon.2 at predetermined intervals in accordance with the recording linear velocity such that the difference between the coefficient .epsilon.1 and the coefficient .epsilon.2 is increased in accordance with an increase in the recording linear velocity, where, when an erase power Pe0 for a single erasing pulse is a target power, the erase power Pe1 is defined as Pe1=.epsilon.1.times.Pe0, and the erase power Pe2 is defined as Pe2=.epsilon.2.times.Pe0.

3. An information recording method of performing recording on an optical disk medium having a recording layer on which mark information is recorded by a laser beam emitted in accordance with a waveform based on a recording pulse sequence, said information recording method comprising the steps of: performing recording while varying a recording clock cycle T in accordance with a variation in a recording linear velocity such that a recording linear density becomes substantially constant; and when performing recording by using multiple pulses defined by an erase power Pe1 and an erase power Pe2 as an erasing pulse for forming a space part between mark parts, updating set values of the erase power Pe1 and the erase power Pe2 at predetermined intervals in accordance with the recording linear velocity, and wherein the step of updating comprises the steps of: updating a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 at predetermined intervals in accordance with the recording linear velocity; detecting index values which are pre-formatted on the optical disk medium of a plurality of recording linear velocities, the erase powers Pe1 and the erase powers Pe2 corresponding to the recording linear velocities, and duty ratios Te1 of a pulse width of the erasing pulse corresponding to the recording linear velocities; calculating variations in the set values of the erase power Pe1, the erase power Pe2, and the duty ratio Te1 that are updated at the predetermined intervals based on the detected index values; and setting the erase power Pe1 and the erase power Pe2 with respect to the desired recording linear velocity.

4. An information recording method of performing recording on an optical disk medium having a recording layer on which mark information is recorded by a laser beam emitted in accordance with a waveform based on a recording pulse sequence, said information recording method comprising the steps of: performing recording while varying a recording clock cycle T in accordance with a variation in a recording linear velocity such that a recording linear density becomes substantially constant; and when performing recording by using multiple pulses defined by an erase power Pe1 and an erase power Pe2 as an erasing pulse for forming a space part between mark parts: updating a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 at predetermined intervals in accordance with the recording linear velocity; detecting address information that is pre-formatted on the optical disk medium; calculating the set values of the erase power Pe1, the erase power Pe2, and a duty ratio Te1 of a pulse width of the erasing pulse with respect to the address information corresponding to the recording linear velocity from variations in the set values that are updated at predetermined intervals; and calculating the set values of the erase power Pe1, the erase power Pe2, and the duty ratio Te1 with respect to desired address information by associating the predetermined intervals with corresponding ranges of the address information.

5. An information recording method of performing recording on an optical disk medium having a recording layer on which mark information is recorded by a laser beam emitted in accordance with a waveform based on a recording pulse sequence, said information recording method comprising the steps of: performing recording while varying a recording clock cycle T in accordance with a variation in a recording linear velocity such that a recording linear density becomes substantially constant; when performing recording by using multiple pulses defined by an erase power Pe1 and an erase power Pe2 as an erasing pulse for forming a space part between mark parts, updating a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 with respect to a cycle of the multiple pulses at predetermined intervals in accordance with the recording linear velocity; and updating a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 at predetermined intervals in accordance with the recording linear velocity such that the duty ratio Te1 with respect to the cycle of the multiple pulses defined by the erase power Pe1 and the erase power Pe2, where Pe1>Pe2, is decreased in accordance with an increase in the recording linear velocity.

6. An information recording method of performing recording on an optical disk medium having a recording layer on which mark information is recorded by a laser beam emitted in accordance with a waveform based on a recording pulse sequence, said information recording method comprising the steps of: performing recording while varying a recording clock cycle T in accordance with a variation in a recording linear velocity such that a recording linear density becomes substantially constant; when performing recording by using multiple pulses defined by an erase power Pe1 and an erase power Pe2 as an erasing pulse for forming a space part between mark parts, updating a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 with respect to a cycle of the multiple pulses at predetermined intervals in accordance with the recording linear velocity, and wherein the step of updating comprises the steps of: updating set values of the erase power Pe1 and the erase power Pe2 at predetermined intervals in accordance with the recording linear velocity; detecting index values which are pre-formatted on the optical disk medium of a plurality of the recording linear velocities, the erase powers Pe1 and the erase powers Pe2 corresponding to the recording linear velocities, and duty ratios Te1 of a pulse width of the erasing pulse corresponding to the recording linear velocities; calculating variations in the set values of the erase power Pe1, the erase power Pe2, and the duty ratio Te1 that are updated at the predetermined intervals based on the detected index values; and setting the erase power Pe1 and the erase power Pe2 with respect to the desired recording linear velocity.

7. An information recording method of performing recording on an optical disk medium having a recording layer on which mark information is recorded by a laser beam emitted in accordance with a waveform based on a recording pulse sequence, said information recording method comprising the steps of: performing recording while varying a recording clock cycle T in accordance with a variation in a recording linear velocity such that a recording linear density becomes substantially constant; and when performing recording by using multiple pulses defined by an erase power Pe1 and an erase power Pe2 as an erasing pulse for forming a space part between mark parts, updating set values of the erase power Pe1 and Pe2 and a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 with respect to a cycle of the multiple pulses at predetermined intervals in accordance with the recording linear velocity, and wherein the step of updating comprises the steps of: updating a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 at predetermined intervals in accordance with the recording linear velocity; detecting address information that is pre-formatted on the optical disk medium; calculating the set values of the erase power Pe1, the erase power Pe2, and a duty ratio Te1 of a pulse width of the erasing pulse with respect to the address information corresponding to the recording linear velocity from variations in the set values that are updated at predetermined intervals; and calculating the set values of the erase power Pe1, the erase power Pe2, and the duty ratio Te1 with respect to desired address information by associating the predetermined intervals with corresponding ranges of the address information.

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Description

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to information recording methods and information recording apparatuses for phase change optical disks such as DVD-RWs (ReWritable), which include a recording layer whose phase is reversibly changed between a crystal phase and an amorphous phase and are compatible with the formats of, for example, DVD-Videos (Digital Videos or Digital Versatile Discs) and playback-only DVDs such as DVD-ROMs.

2. Description of the Related Art

With the penetration of multi-media, various information recording disks have been developed: examples include playback-only disks such as DVD-Videos and DVD-ROMs, recordable DVD-Rs using an organic dye material for a recording layer, and rewritable DVD-RWs using a phase change material for a recording layer.

Information (sectors, in this example) recorded on such DVDs is in the format shown in FIG. 1A. In such a format, data (sectors) are continuously recorded on the entire track of a disk at a constant linear density as shown in FIG. 1B.

In order to achieve an information recording medium having compatibility with playback-only disks, information is recorded with a constant recording channel clock frequency as shown in FIG. 1D while constantly maintaining the linear velocity in the track by controlling the rotational speed of the disk such that the number of revolutions becomes inversely proportional to the track radius by using a CLV (Constant Linear Velocity) method as a method for controlling the rotational speed of the information recording medium (disk) as shown in FIG. 1C.

However, in order to control the rotational speed by the CLV method, it is necessary to vary the rotational speed of a disk such that the linear velocity in the track becomes constant. That is, a great running torque and a large and high-cost motor are required since the speed of a spindle motor for rotating the disk needs to be varied. In addition, there is a disadvantage in that, at the time of seeking, a longer access time is required compared to that of an HDD or a MO drive, since a waiting time period is required until completion of speed variation of the spindle motor.

In order to perform recording on a disk while maintaining a constant rotational speed of the disk without performing speed variation control, it has also been conceived to make the format of information recorded on a disk as shown in FIGS. 2A through 2D. That is, as shown in FIG. 2D, the frequency of a channel clock used in recording of the disk is decreased in the inner tracks and increased in the outer tracks such that the frequency is proportional to the radius position of the track. In this case, since the recording linear velocity becomes small in the inner tracks and large in the outer tracks, the recording linear density is constant as shown in FIG. 2B. In addition, it is possible to record information on the disk while maintaining a constant number of revolutions (rotational speed) of the disk as shown in FIG. 2C, i.e., by using a CAV (Constant Angular Velocity) method.

Accordingly, it becomes unnecessary to perform rotational speed variation control of the spindle motor that rotates the disk. Thus, low-revolution torque will suffice and it is possible to use a small and low-cost motor. Further, since speed variation is not performed, the waiting time period at the time of seeking is eliminated. Consequently, it is possible to significantly reduce the access time period.

Additionally, it is also possible to use a ZCLV method in which an optical disk medium is divided into a plurality of regions (zones) in the radial direction thereof, and the recording speed for each of the zones is varied such that the average number of revolutions (angular velocity) of the disk over the zones becomes constant while maintaining a constant recording linear velocity in each of the zones by using the above-mentioned CLV method.

However, generally, in a phase change optical disk medium, the ratio among the pulse width of a recording pulse sequence, heating power, and erase power of a laser emission during recording at a specific recording linear velocity is optimized, and the states of marks and spaces formed vary at a different recording linear velocity. In other words, the heat capacity of a top heating pulse, which is necessary for formation of a mark, may be excessive or deficient, the average length of marks may be different due to variation in cooling rate, and faulty erasing and degradation of a recording film may occur due to excessive or deficient erase power. Hence, jitter may be degraded or the number of times of overwriting may be decreased.

In this regard, according to Japanese Laid-Open Patent Application No. 5-22570, in order to obtain in a relatively short time period an optimum recording light volume corresponding to the entire recordable regions of each optical disk, the optimum light volume is obtained at the same recording linear velocity for each of at least two positions in a test-writing region. Then, by performing interpolation or extrapolation with respect to the optimum recording light volumes at the two recording linear velocities obtained by an interpolating routine, the optimum recording light volumes are obtained for all of the recording linear velocities.

In addition, according to Japanese Laid-Open Patent Application No. 5-274678, in order to reduce the laser power required for recording without degrading jitter characteristics, in a method of recording information in the outer track regions at frequencies higher than those for the inner track regions by emitting an optical beam whose intensity is modulated in accordance with an information signal on the basis of a reference clock that is different for each region while rotating an optical disk at a constant number of revolutions, the optical beam is periodically emitted at a frequency that is an integral multiple of the frequency of the reference clock for each region. Additionally, when the optical beam is emitted on the outer track regions, the duty ratio of pulse emission is set larger than that in the time when the optical beam is emitted on the inner track regions.

Further, according to Japanese Laid-Open Patent Application No. 10-106008, in order to provide an optical disk apparatus capable of high-speed and highly-reliable recording, an optical disk, an optical head, synchronization signal generating means, a VCO, phase comparing means, a controller, and recording signal generating means are provided, and the height and width of a pulse of a recording signal is varied in accordance with the recording linear velocity, such that recording can be consistently performed under the best recording conditions.

Additionally, Japanese Laid-Open Patent Application No. 2001-118245 discloses a method in which, among a top heating pulse duty ratio Ttop for varying the front edge of the top heating pulse in a recording pulse sequence, an end-off cooling pulse duty ratio Tecp for varying the rear edge of the end-off cooling pulse in the recording pulse sequence, and an erase power ratio E that is the ratio of an erase power Pe with respect to a heating power Pw, at least two of the above-mentioned set values are updated at predetermined intervals. Thereby, even if the recording linear velocity is varied by CAV control that makes the number of revolutions of a disk constant, recording is performed in which uniform characteristics are obtained over the entire surface of a phase change optical disk medium.

However, generally, it is difficult for a phase change optical disk to correspond to a wide-range recording linear velocity. Particularly, in a case where recording is performed at a high recording linear velocity, it is necessary to adjust the length of a recording mark by lowering the level of erase power. Thus, there is a problem in that erase power sufficient for overwriting cannot be supplied.

In this regard, according to Japanese Patent Publication No. 02707774, it is disclosed that overwriting characteristics at a high recording speed are improved by composing an erasing pulse part by multiple pulses, thereby achieving the erasing level of high erase power and reduction of the average power by using low erase power. However, in a recording state where the recording linear velocity is not constant as in CAV recording, it is difficult to perform recording in which uniform signal characteristics are obtained over the entire surface of a disk and a decrease in the number of times of overwriting is prevented.

That is, in the above-mentioned patent documents, the set values of some elements of a recording pulse sequence, such as the duty ratio of pulse emission, are varied in accordance with the recording linear velocity as in the CAV method. However, merely qualitative effects with respect to an optical disk medium are obtained, which are not sufficient for recording disks, particularly, for DVDS.

In other words, since variation in overwriting characteristics, i.e., variation in characteristics of recording information (RF signal) such as a decrease in the number of times of overwriting, is not only affected by formation of a recording mark part but also by the light emission waveform of an erasing pulse part in an interacting manner, the recording methods disclosed in the above-mentioned patent documents are not sufficient, and it is not always possible to obtain uniform signal characteristics over the entire surface of an optical disk and to avoid a decrease in the number of times of overwriting. Thus, it is not always possible to obtain desired effects at a high recording linear velocity covering a wide range. Moreover, even if the set values of an erasing pulse part are to be varied, quantitative study has not been conducted with respect to how to vary the set values.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide an improved and useful information recording method and information recording apparatus in which one or more of the above-mentioned problems are eliminated.

Another and more specific object of the present invention is to provide an information recording method and an information recording apparatus that can perform recording while achieving uniform signal characteristics over the entire surface of a phase change optical disk medium having a recording layer whose phase reversibly varies between a crystal phase and an amorphous phase, and that can avoid a decrease in the number of times of overwriting with good overwriting characteristics by using a simple method without performing speed variation control of the rotational speed of the optical disk at the time of recording of information while rotating the optical disk, and while maintaining compatibility with the recording formats of conventional playback-only optical disks.

A further object of the present invention is to provide an information recording method and an information recording apparatus that are effective in controlling the emitted light volume of a LD at the time of recording to be a constant value by means of a drive circuit.

In order to achieve one or more of the above-mentioned objects, according to one aspect of the present invention, there is provided an information recording method of performing recording on an optical disk medium having a recording layer on which mark information is recorded by a laser beam emitted in accordance with a waveform based on a recording pulse sequence, said information recording method comprising the steps of:

performing recording while varying a recording clock cycle T in accordance with a variation in a recording linear velocity such that a recording linear density becomes substantially constant; and

when performing recording by using multiple pulses defined by an erase power Pe1 and an erase power Pe2 as an erasing pulse for forming a space part between mark parts, updating set values of the erase power Pe1 and the erase power Pe2 at predetermined intervals in accordance with the recording linear velocity.

Accordingly, even if the recording linear velocity is varied as in the CAV method and the erase condition of an optical disk medium varies, it is possible to constantly supply a sufficient erase power by using the erase power Pe1 in the multiple pulses without increasing the average erase power. Also, since the set values of the erase powers Pe1 and Pe2 are sequentially updated (set) at predetermined intervals in accordance with the recording linear velocity, it is possible to perform recording with good overwriting characteristics over an entire surface of the optical disk medium.

Additionally, according to another aspect of the present invention, there is provided an information recording method of performing recording on an optical disk medium having a recording layer on which mark information is recorded by a laser beam emitted in accordance with a waveform based on a recording pulse sequence, said information recording method comprising the steps of:

performing recording while varying a recording clock cycle T in accordance with a variation in a recording linear velocity such that a recording linear density becomes substantially constant; and

when performing recording by using multiple pulses defined by an erase power Pe1 and an erase power Pe2 as an erasing pulse for forming a space part between mark parts, updating a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 with respect to a cycle of the multiple pulses at predetermined intervals in accordance with the recording linear velocity.

Accordingly, even if the erase condition of an optical disk medium varies with a variation in the recording linear velocity as in the CAV method, an optimum duty ratio of the pulse width of the erase power is sequentially and constantly updated (set). Hence, it is possible to perform recording with good overwriting characteristics over an entire surface of the optical disk. Particularly, when varying the duty ratio of the pulse width of the erasing pulse, the edge position of the erasing pulse of the erase power Pe1 may be varied in accordance with the recording linear velocity. Thus, the control is easy and the process can be simplified.

Additionally, according to another aspect of the present invention, there is provided an information recording method of performing recording on an optical disk medium having a recording layer on which mark information is recorded by a laser beam emitted in accordance with a waveform based on a recording pulse sequence, said information recording method comprising the steps of:

performing recording while varying a recording clock cycle T in accordance with a variation in a recording linear velocity such that a recording linear density become substantially constant; and

when performing recording by using multiple pulses defined by an erase power Pe1 and an erase power Pe2 as an erasing pulse for forming a space part between mark parts, updating set values of the erase power Pe1 and the erase power Pe2 and a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 with respect to a cycle of the multiple pulses at predetermined intervals in accordance with the recording linear velocity.

Accordingly, even if the recording linear velocity is varied as in the CAV method and the erase condition of an optical disk medium varies, it is possible to constantly supply a sufficient erase power by using the erase power Pe1 in the multiple pulses without increasing the average erase power. Also, since the set values of the eraser powers Pe1 and Pe2 are sequentially updated (set) at predetermined intervals in accordance with the recording linear velocity, it is possible to perform recording with good overwriting characteristics over an entire surface of the optical disk medium. Particularly, when varying the duty ratio of the pulse width of the erasing pulse, the edge position of the erasing pulse of the erase power Pe1 may be varied in accordance with the recording linear velocity. Thus, the control is easy and the process can be simplified.

In an embodiment of the present invention, the step of updating may include the step of updating the set values of the erase power Pe1 and the erase power Pe2 at predetermined intervals in accordance with the recording linear velocity such that the difference between the erase power Pe1 and the erase power Pe2 is increased in accordance with an increase in the recording linear velocity.

In another embodiment of the present invention, the step of updating may include the step of updating set values of a coefficient .epsilon.1 and a coefficient .epsilon.2 at predetermined intervals in accordance with the recording linear velocity such that the difference between the coefficient .epsilon.1 and the coefficient .epsilon.2 is increased in accordance with an increase in the recording linear velocity, where, when an erase power Pe0 for a single erasing pulse is a target power, the erase power Pe1 is defined as Pe1=.epsilon.1.times.Pe0, and the erase power Pe2 is defined as Pe2=.epsilon.2.times.Pe0.

In a case where a recording linear velocity range that requires an erasing pulse divided into multiple pulses is to be covered, it is preferable to increase the erase power Pe1, which is the higher power and affects the overwriting characteristics, to a higher power in accordance with an increase in the recording linear velocity. Also, with respect to jitter characteristics, which are signal characteristics, it is preferable to reduce the erase power Pe2, which is the lower power, to a lower power in accordance with the increase in the recording linear velocity. However, by increasing the difference between the erase powers Pe1 and Pe2 in accordance with the increase in the recording linear velocity, it is possible to achieve both overwriting characteristics and jitter characteristics.

In an embodiment of the present invention, an information recording method may further include the step of updating a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 at predetermined intervals in accordance with the recording linear velocity such that the duty ratio Te1 with respect to the cycle of the multiple pulses defined by the erase power Pe1 and the erase power Pe2, where Pe1>Pe2, is decreased in accordance with an increase in the recording linear velocity.

In a case where a recording linear velocity range that requires an erasing pulse divided into multiple pulses is to be covered, it is preferable to increase the erase power Pe1, which is the higher power and affects the overwriting characteristics, to a higher power in accordance with an increase in the recording linear velocity. Also, with respect to jitter characteristics, which are signal characteristics, it is preferable to reduce the erase power Pe2, which is the lower power, to a lower power in accordance with the increase in the recording linear velocity. However, by decreasing the duty ratio Te1 of the pulse width of the erase power Pe1 with respect to the cycle of the multiple pulses in accordance with the increase in the recording linear velocity, it is possible to achieve both overwriting characteristics and jitter characteristics.

In an embodiment of the present invention, the step of updating may include the steps of:

updating a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 at predetermined intervals in accordance with the recording linear velocity;

detecting index values which are pre-formatted on the optical disk medium of a plurality of recording linear velocities, the erase powers Pe1 and the erase powers Pe2 corresponding to the recording linear velocities, and duty ratios Te1 of a pulse width of the erasing pulse corresponding to the recording linear velocities;

calculating variations in the set values of the erase power Pe1, the erase power Pe2, and the duty ratio Te1 that are updated at the predetermined intervals based on the detected index values; and

setting the erase power Pe1 and the erase power Pe2 with respect to the desired recording linear velocity.

Accordingly, it is possible to determine the minimum intervals for updating the set values without calculating through test writing the initial values of the erase power values and the duty ratio of the pulse width of the erasing pulse formed by the multiple pulses. Also, it is possible to perform recording with uniform characteristics over an entire surface of the optical disk medium by a simple method.

In an embodiment of the present invention, the step of updating may include the step of reading one of:

updating a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 at predetermined intervals in accordance with the recording linear velocity;

reading one of:

first optimum set values of: a plurality of recording linear velocities; the erase powers Pe1 and the erase powers Pe2 corresponding to the recording linear velocities; and duty ratios Te1 of the pulse width corresponding to the recording linear velocities, said first optimum set values being included in disk information previously recorded in a predetermined area of the optical disk medium in the past; and

second optimum set values of: a plurality of recording linear velocities; the erase powers Pe1 and the erase powers Pe2 corresponding to the recording linear velocities; and duty ratios Te1 of the pulse width corresponding to the recording linear velocities, said second optimum set values being stored in an information recording apparatus beforehand, and

setting the erase power Pe1 and the erase power Pe2 with respect to the recording linear velocity by calculating variations in the set values of: the erase power Pe1; the erase power Pe2; and the duty ratio Te1 of the pulse width, which are updated at the predetermined intervals, based on one of the first and second optimum set values that are read.

Accordingly, even in a case where recording or overwriting is performed on the optical disk medium, by using the optimum set values that are obtained from the optimum set values recorded in the previous time, it is possible to determine the minimum intervals for updating the set values without calculating again the erase power values and the duty ratio of the pulse width of the erasing pulse formed by the multiple pulses. Thus, it is possible to reduce the process time required until recording is started. Also, it is possible to perform recording with uniform characteristics over an entire surface of the optical disk by a simple method.

In an embodiment of the present invention, the step of updating may include the steps of:

updating a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 at predetermined intervals in accordance with the recording linear velocity;

detecting address information that is pre-formatted on the optical disk medium;

calculating the set values of the erase power Pe1, the erase power Pe2, and a duty ratio Te1 of a pulse width of the erasing pulse with respect to the address information corresponding to the recording linear velocity from variations in the set values that are updated at predetermined intervals; and

calculating the set values of the erase power Pe1, the erase power Pe2, and the duty ratio Te1 with respect to desired address information by associating the predetermined intervals with corresponding ranges of the address information.

Accordingly, even during recording, it is possible to easily and accurately determine the intervals for updating the set values such that the calculated optimum set values of an erasing pulse sequence formed by multiple pulses are not shifted. Thus, even if the recording linear velocity is varied and the erase condition of an optical disk medium varies as in the CAV method, it is possible to constantly update with a high degree of accuracy the optimum erase powers and the optimum duty ratio of the pulse width of the erasing pulse. Hence, it is possible to perform recording with good overwriting characteristics over an entire surface of the optical disk medium.

In an embodiment of the present invention, the step of updating may include the steps of:

updating a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 at predetermined intervals in accordance with the recording linear velocity;

detecting one of index values or optimum set values of: a plurality of recording linear velocities; and the erase power Pe1, the erase power Pe2, and a duty ratio Te1 of a pulse width of the erasing pulse that are corresponding to the recording linear velocities; and

calculating variations in the set values of the erase power Pe1, the erase power Pe2, and the duty ratio Te1 that are updated at the predetermined intervals by one of a linear function approximation or a quadratic function approximation based on the detected one of the index values or optimum set values.

Accordingly, by solving a simple approximate expression based on the index values or optimum set values at several positions for which different recording linear velocities are set, it is possible to calculate with ease and with a sufficient degree of accuracy the erasing powers and the duty ratio of the pulse width at arbitrary address or recording linear velocity in each zone.

Additionally, according to another aspect of the present invention, there is provided an information recording apparatus that performs recording on an optical disk medium having a recording layer on which mark information is recorded by a laser beam emitted in accordance with a waveform based on a recording pulse sequence while varying a recording clock cycle T in accordance with a variation in a recording linear velocity such that a recording linear density becomes substantially constant, the information recording apparatus including:

a controller that, when performing recording by using a plurality of multiple pulses defined by an erase power Pe1 and an erase power Pe2 as an erasing pulse for forming a space part between mark parts, updates at predetermined intervals in accordance with a recording linear velocity at least one of: set values of the erase power Pe1 and the erase power Pe2; and a set value of a duty ratio Te1 of a pulse width of the erase power Pe1 with respect to the cycle of the multiple pulses;

a pulse width varying part that varies a position of an edge of the erasing pulse for the multiple pulses in accordance with the updated duty ratio Te1; and

a driver circuit that updates and controls an amount of light emitted from a laser light source in accordance with the updated erase power Pe1 and the updated erase power Pe2.

Accordingly, even in a case where an information recording method, such as the CAV method, in which the recording linear velocity is varied is used for an optical disk medium corresponding to a wide range of the recording linear velocity, it is possible to perform recording with good overwriting characteristics over an entire surface of the optical disk medium with a simple and small circuit configuration.

Additionally, according to another aspect of the present invention, there is provided an information recording apparatus that performs recording on an optical disk medium having a recording layer on which mark information is recorded by a laser beam emitted in accordance with a waveform based on a recording pulse sequence while varying a recording clock cycle T in accordance with a variation in a recording linear velocity such that a recording linear density becomes substantially constant, the information recording apparatus including:

a controller that, when performing recording by using a plurality of multiple pulses defined by an erase power Pe1 and an erase power Pe2 as an erasing pulse for forming a space part between mark parts, calculates and updates at predetermined intervals set values of the erase power Pe1, the erase power Pe2, and a duty ratio Te1 of a pulse width of the erase power Pe1 that are corresponding to the recording linear velocity by performing an approximation with respect to the recording linear velocity on the set values of the erase power Pe1, the erase power Pe2, and the duty ratio Te1 with respect to the cycle of the multiple pulses, said set values corresponding to one of address information and recording linear velocity information detected from the optical disk medium;

an erasing pulse generation part that varies a position of an edge of the erasing pulse for the multiple pulses in accordance with the updated duty ratio Te1 and generates the multiple pulses defined by the erase power Pe1 and the erase power Pe2; and

a driver circuit that updates and controls an amount of light emitted from a laser light source in accordance with the updated erase power Pe1 and the updated erase power Pe2.

Accordingly, even in a case where an information recording method, such as the CAV method, in which the recording linear velocity is varied is used for an optical disk medium corresponding to a wide range of the recording linear velocity, it is possible to calculate the set values for an erasing pulse sequence with respect to a desired recording linear velocity with a simple and small circuit configuration. Also, it is possible to drive a laser light source with a high degree of accuracy. Hence, it is possible to perform recording with good overwriting characteristics and with reduced variations in signal characteristics over an entire surface of the optical disk medium.

Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram showing a format of a disk in the conventional CLV method;

FIG. 1B is a graph showing the relationship between track position and linear density in the conventional CLV method;

FIG. 1C is a graph showing the relationship between the track position and the number of revolutions in the conventional CLV method;

FIG. 1D is a graph showing the relationship between the track position and a channel clock frequency in the conventional CLV method;

FIG. 2A is a schematic diagram showing a format of a disk in the conventional CAV method;

FIG. 2B is a graph showing the relationship between track position and linear density in the conventional CAV method;

FIG. 2C is a graph showing the relationship between the track position and the number of revolutions in the conventional CAV method;

FIG. 2D is a graph showing the relationship between the track position and a channel clock frequency in the conventional CAV method;

FIG. 3 is a pulse waveform chart showing the recording pulse sequences used at the innermost track position, the intermediate track position, and the outermost track position of a phase change optical disk in one embodiment of the present invention;

FIGS. 4A, 4B and 4C are graphs for explaining examples of updating Ttop, Tecp, and .epsilon.0 in accordance with recording linear velocity;

FIGS. 5A and 5B are schematic diagrams for explaining the use of multiple pulses in a space part;

FIGS. 6A, 6B and 6C are graphs for explaining examples of updating Te1, .epsilon.1 and .epsilon.2 in accordance with the recording linear velocity;

FIGS. 7A, 7B and 7C are graphs for explaining examples of updating Te1, Pe1 and Pe2 in accordance with the recording linear velocity;

FIG. 8 is a graph showing asymmetry characteristics;

FIG. 9 is a flow chart for explaining an information recording method according to a second embodiment of the present invention; and

FIG. 10 is a block diagram showing the structure of an information recording apparatus according to a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 3A through 8, a description is given below of a first embodiment of the present invention.

As shown in FIG. 3B, in a basic recording pulse sequence used in a phase change optical disk, which is an optical disk medium, the pulse width is set by: a top heating pulse duty ratio Ttop of the top heating pulse constituting a recording pulse sequence; a duty pulse Tmp of a heating pulse in a multi-pulse part following the top heating pulse; and an end-off cooling pulse duty ratio Tecp of the end-off cooling pulse of the recording pulse sequence. In addition, recording power is set by heating power Pw, erase power Pe0, and bias power Pb. With respect to the recording power, since the state of mark formation is affected not only by the erase power Pe0 but also by the heating power Pw in an interacting manner, an erase power ratio .epsilon.0 (=Pe0/Pw) of the erase power Pe0 to the heating power Pw is set. In this embodiment, as shown in FIGS. 3C and 3D, a heating pulse (erasing pulse) in an erasing region, which forms a space part between mark parts, is set in more detail by setting a duty ratio Te1 of the erasing pulse for multiple pulses formed by erase power Pe1 and erase power Pe2.

When recording control is performed by using the CAV method with respect to a phase change DVD having a diameter of 120 mm, if the DVD standard recording linear velocity is 3.5 m/s (1-speed), 3-time speed (10.5 m/s) is obtained at the innermost track position and about 7.3-time speed (25.6 m/s) is obtained at the outermost track position as a phase change optical disk corresponding to high speed. The frequency of a recording clock is approximately 78.5 MHz at the innermost track position and approximately 191 MHz at the outermost track position. When the same setting values of a recording pulse sequence are used for the recording linear velocity covering such a wide range, it is difficult for a general phase change optical disk to perform uniform recording.

As the recording linear velocity is increased, heating by heating power Ptop and the duty ratio Ttop of the top heating pulse, and heating power Pmp and the duty ratio Tmp of the multiple pulses following the top heating pulse becomes insufficient, and the degree of modulation of the RF signal is decreased or/and asymmetry is decreased. Hence, as shown in FIG. 4A, by updating the set values Ttop, for example, such that the set values are increased in accordance with the increase in the recording linear velocity, it is possible to apply a sufficient amount of heat in order to maintain good formation of marks.

On the other hand, as the recording linear velocity is increased, the cooling speed is increased. Hence, the average length of formed marks becomes long and the asymmetry of the RF signal is increased. Accordingly, by decreasing the end-off cooling pulse duty ratio Tecp in accordance with the increase in the recording linear velocity, it is possible to maintain the characteristics of the RF signal even at different recording linear velocities.

However, with the increase in the recording linear velocity, as shown in FIG. 5A, the erase power required at the time of overwriting also becomes insufficient due to the increase in the cooling speed. Thus, degradation of jitter occurs due to faulty erasing. Accordingly, by updating the set value of the erase power ratio .epsilon.0 (=Pe/Pw) such that the set value thereof is increased in accordance with the increase in the recording linear velocity, it is possible to apply sufficient erase power and maintain good formation of spaces.

However, when making a phase change optical disk correspond to high recording linear velocity, the erase power ratio .epsilon.0 is reduced compared to a disk corresponding to low speed. This is because even if the erase power is set to a sufficiently high value at which optimum overwriting characteristics are obtained at low speeds, the reflection rate is reduced at high speeds due to formation of an amorphous phase, which is achieved during a cooling state from the time at which the erase power is applied. Thus, with respect to the recording linear velocity in the high-speed side, by dividing an erasing pulse, which constitutes a space part, into multiple pulses (multi-pulse part) and applying a high heating power required for overwriting in combination with a low heating power for relaxing an increase in the cooling speed, recording achieving uniform and good jitter characteristics may be performed while preventing a decrease in the number of times of overwriting.

In this embodiment, in a case where recording is performed while varying the recording linear velocity depending on the radial position by using such a basic waveform as in the CAV method, the set values are updated in the following manner so as to perform good recording over the entire surface of a disk. Specific examples of the set values are as follows. As shown in FIG. 4A, the top heat pulse duty ratio Ttop is varied from 0.55 T (.apprxeq.7.0 ns) at the minimum velocity (the innermost track position) to 0.75 T (.apprxeq.3.5 ns) at the maximum velocity (the outermost track position). That is, the set value (the top heat pulse duty ratio Ttop) is updated (varied) such that the set value is varied by 0.2 T in total. Similarly, the end-off cooling pulse duty ratio Tecp is varied from 0.5 T (.apprxeq.6.4 ns) at the innermost track position to 0.2 T (.apprxeq.1.0 ns) at the outermost track position. That is, the set value (the end-off cooling pulse duty ratio Tecp) is updated (changed) such that the set value is varied by 0.3 T in total. Additionally, the intervals at which the set value of the end-off cooling pulse duty ratio Tecp is updated are the same as those at which the top heat pulse duty ratio Ttop is updated.

As for the erase power Pe, the set value of the erase power ratio .epsilon.0 of the erase power Pe to the heating power Pw is updated (varied) from 0.4 at the innermost track position to 0.5 at the outermost track position, that is, a variation of 0.1 in total.

In this embodiment, each of the set values relating to a recording mark part with respect to the recording linear velocity is calculated by linear approximation (linear expression) by using the set values of the recording linear velocity for two positions: the innermost track position and the outermost track position. Each of the set values may be obtained, for example by using the following approximate expressions. Ttop[T]=0.013.times.LV[m/s]+0.41 Tecp[T]=0.007.times.LV[m/s]+0.33 .epsilon.0=-0.029.times.LV[m/s]+1.45

FIGS. 4B and 4C show cases where each of the set values is updated in stages or at intervals, each stage or interval being approximately 1.0 m/s in the recording linear velocity.

The description is given above of an exemplary setting for recording a recording mark part with low jitter. It should be noted that, in this embodiment, an erasing pulse part (space part) is set in more detail at a high recording linear velocity.

Specific examples of the set values are as follows. As shown in FIGS. 6A and 7A, the duty ratio Te1 of an erasing pulse having the erase power of Pe1 is 1 (.apprxeq.12.7 ns) at the innermost track position but is varied from 0.8 T (.apprxeq.5.9 ns) at an intermediate track position (intermediate track speed) to 0.3 T (.apprxeq.1.6 ns) at the outermost track position. That is, the set value of the duty ratio Te1 is updated (varied) such that the set value is decreased by 0.7 T in total.

It can be seen that the duty ratio Te1 of an erasing pulse of the erase power Pe1 is not linearly varied in the range from the innermost track position to the outermost track position. This is because, in a case where recording is performed on a phase change optical disk at the recording linear velocity that is varied in a wide range as mentioned above, it is possible to achieve both overwriting characteristics and jitter characteristics (reproduction signal quality) at a low recording linear velocity even if erasing pulses are of a constant power level. However, at a high recording linear velocity, it is necessary to form an erasing pulse by multiple pulses defined by: a high erase power Pe1, which is a high erasing level; and a low erase power Pe2, which can reduce the average erasing power.

Accordingly, with respect to a phase change optical disk that, between the maximum velocity (at the outermost track position) and the intermediate velocity of the recording linear velocity, uses a recording linear velocity requiring multiple pulses for the erase power as in this embodiment, the duty ratio Te1 of the erase power is decreased or/and the range is set where the difference between the erase power Pe1 and the erase power Pe2 is increased. In addition, as shown in FIG. 6A, the range may be set where the difference between the ratios .epsilon.1 and .epsilon.2 of the erase power is increased.

That is, various applicable ranges may be used for the recording linear velocity of a phase change optical disk. It is possible to determine the set values relating to an erasing pulse at an arbitrary recording linear velocity based on the parameters (the duty ratio Te1 and the power ratios .epsilon.1 and .epsilon.2) composing erasing pulses that correspond to the recording linear velocities of at least three positions. In this embodiment, when calculating each of the set values for a recording linear velocity, a region that requires multiple pulses as an erasing pulse is derived from linear approximation (linear expression) by using two kinds of the set values: the set values at the intermediate velocity and those at the maximum velocity. Each of the parameters may be obtained, for example, by using the following approximations. Te1[T]=-0.066.times.LV[m/s]+1.99 .epsilon.1=0.066.times.LV[m/s]+0.0056 .epsilon.2=-0.029.times.LV[m/s]+1.45

Further, approximately 15 m/s is obtained as the recording linear velocity at which all of the set values of Te1, .epsilon.1 and .epsilon.2 become 1, i.e., an erasing pulse becomes a single pulse, through calculation of the above-mentioned linear approximation. The position corresponding to the obtained recording linear velocity defines the inner track region where an erasing pulse formed by a single pulse, which is used at low recording linear velocity, and the outer track region where an erasing pulse is formed by multiple pulses, which are used at high recording linear velocity. FIGS. 6B and 7B show cases where each of the set values is updated in stages or at intervals, each stage or interval being approximately 1.0 m/s in the recording linear velocity.

In another embodiment of the present invention, the duty ratio of an erasing pulse composed by multiple pulses may be set to a fixed value, and only the set values of the erase powers Pe1 and Pe2 may be updated in accordance with the variation of the recording linear velocity. In this case, by correcting the erase power ratios .epsilon.1 and .epsilon.2 so as to calculate an optimum value with respect to the erase power, it is possible to perform recording while practically preventing degradation of jitter characteristics and overwriting characteristics.

In still another embodiment of the present invention, the erase power Pe1 (or .epsilon.1) and the erase power Pe2 (or .epsilon.2) of an erasing pulse composed by multiple pulses may be set to fixed values, and the set value of the duty ratio Te1, which is the pulse width of the erase power Pe1 with respect to the multi-pulse cycle, may be updated in accordance with the variation of the recording linear velocity. In this case, by correcting the duty ratio Te1 of an erasing pulse so as to calculate an optimum value with respect to the duty ratio serving as an execution value instead of setting again the erase power level in accordance with the recording linear velocity, it is possible to perform recording while practically preventing degradation of jitter characteristics and overwriting characteristics.

The recording speed for a phase change optical disk depends on the crystallization speed of the material of a recording layer. For this reason, there exists two kinds of ranges for the recording linear velocity: a range allowing good erasing with a single erasing pulse and erase power; and a range allowing the optimum erasing without faulty erasing with multiple erasing pulses and erase powers as shown in FIG. 5B. Accordingly, at least in the recording linear velocity range in which multiple erasing pulses are used, the erase power Pe1 is increased, which is the higher erase power and affects the overwriting characteristics, to a further higher power in accordance with the increase of the recording linear velocity. Additionally, with respect to the jitter characteristics, which are signal characteristics, the erase power Pe2 is decreased, which is the lower erase power, to a further lower power in accordance with the increase of the recording linear velocity. That is, in yet another embodiment of the present invention, by increasing the difference between the erase power Pe1 and the erase power Pe2, i.e., by decreasing the duty ratio Te1, in accordance with the increase of the r