Patent Application
20060262709
1. Field of the Invention
The field relates to an optical information recording apparatus, an optical information recording method, and a signal processing circuit. In particular, the present invention relates to an optical information recording apparatus capable of optimizing a recording condition depending on compatibility between a drive and a medium.
2. Description of the Related Technology
In a recording process onto an optical information recording medium (hereinafter, referred to as ‘medium’) as represented by CR-R, DVD-R, or the like, compatibility between a medium to be recorded and a recording apparatus (hereinafter, referred to as ‘drive’) to be used for recording depends on the combination of the drive and the medium. As a cause for the dependence, medium-side factors which affect an optimum recording condition due to a difference in type of a recording material constituting a medium or a manufacturing variation in deposited film properties, and drive-side factors which affect an optimum condition due to a difference in type of an optical pickup device or a semiconductor laser constituting a drive or a manufacturing variation in assemblies may be taken into account. However, the cause is actually due to a certain combination of these factors, and thus there exists an optimum recording condition for every combination of a medium and a drive.
In the past, a method has been employed in such a manner that ID information from which a type of a medium can be identified by a drive is stored to a medium side, and a recording condition prepared for each type of medium is stored to a drive side. According to this method, when actual recording is performed, the ID information on the medium is read from the medium being loaded in the drive and a recording condition (hereinafter, referred to as ‘write strategy’) associated with the ID information is used.
However, sometimes the above-described method cannot accept an unknown medium, which has not been examined, under a prepared recording condition, although it can select to some extent a recording condition appropriate for a known medium, which has been examined. Further, sometimes the above-described method cannot accept even a known medium under a prepared recording condition in case of a change in recording environment such as a recording rate, disturbance, or change with time.
A method intended to accept such an unknown medium is described in Japanese patent publication nos. JP-A-2003-30837 and JP-A-2004-110995. The paragraph [0020] of JP-A-2003-30837 describes ‘ . . . a phase error relative to a channel clock is detected for every recording pattern. A recording compensation parameter adjusting section 12 optimizes a light-emission waveform rule based on the detection result by a phase error detecting section 11 . . . ’. That is, in JP-A-2003-30837, there is disclosed a method which detects a phase error and corrects the phase error through the comparison with the channel clock.
The paragraph [0024] of JP-A-2003-30837 describes ‘A test pattern is then recorded to determine the light-emission waveform rule. Next, the relationship between a prepared light-emission waveform rule and a phase error amount is investigated by reproducing the region onto which the test pattern is recorded. That is, a phase error amount for every combination of a length of one of various marks and a space length immediately before the mark is measured. A desired light-emission waveform rule is then determined by estimating the light-emission waveform rule, under which the phase error becomes zero, from the phase error amount measured . . . ’. That is, there is disclosed a method which measures a phase error amount for every combination of a mark and a corresponding space and then estimates the light-emission waveform rule under which the phase error becomes zero (see
According to the method described in JP-A-2003-30837, the correction is performed based on the phase error of a recorded pattern, and thus it is effective for optimizing a strategy.
However, like the past, the method described in JP-A-2003-30837 involves the fine adjustment of the strategy which is previously stored in a drive. Accordingly, good recording quality is rarely implemented for a medium which is not adaptive to the previously stored strategy.
The paragraph [0045] of JP-2004-110995 describes ‘. . . a top pulse corresponding to a 3T period and a non-multi-pulse corresponding to an 8T period are integrally (successively) generated . . . ’. Further, the paragraph [0046] describes ‘. . . a laser power for a write pulse is adjusted in two stages and, when the ratio of a laser power (a pulse height value of the top pulse) Ph to a laser power (a pulse height value of the non-multi-pulse) Pm is optimum, an optimum power can be obtained . . . ’. That is, it is suggested that an optimization of the ratio Ph/Pm is effective.
However, in the method described in JP-A-2004-110995, initial values for Ph and Pm are temporarily set based on values stored in a drive or a medium, as described in the paragraph [0067] thereof, and then an optimum Ph/Pm ratio is obtained. Therefore, similarly to the case of JP-A-2003-30837, good recording quality is rarely implemented for a medium which is not adaptive to the temporarily set values.
On the other hand, in an optical information recording system, when data recording is performed onto a predetermined recording medium, in general, a recording condition adaptive to the recording medium is obtained by test recording using a test recording region provided in the recording medium, before actual data recording.
However, in an optical information recording system for high-speed recording, it is difficult to perform test recording at the same rate as that of actual recording due to the positional relationship of the test recording region and an actual recording region, and the limitation in rotational speed of a spindle motor for rotating the recording medium.
In the past, there has been generally used a method which previously stores a recording condition adaptive to each recording rate for every kind of recording medium in a recording apparatus for performing data recording, and reads out and sets the recording condition at the time of actual high-speed recording, thereby performing data recording.
In the related technology, the fine adjustment of a recording condition at the time of high-speed recording is also performed by using a different between an optimum recording condition when test recording is performed at a recording rate enabling test recording and an optimum condition stored in the recording apparatus.
However, the related art cannot sufficiently accept a variation in characteristics of a recording medium and a recording system. Further, the related art cannot accept a recording medium, which has not been previously stored in the recording apparatus, or ‘unknown medium’ such as a recording medium, which has been developed after the manufacture of the recording apparatus. Accordingly, a technology has been demanded which obtains an optimum recording condition for every recording rate depending on the characteristics of a medium onto which data recording is performed and a recording apparatus.
As a method for solving the problem, there has been known a method, as described in JP-A-2004-234698, which reads out the relationship between amplitude information of two kinds or more of recording rates previously recorded onto a recording medium and a recording power, and calculates a recording power of a recording rate to be recorded.
However, because this method has an assumption that information for recording power calculation is previously recorded onto a recording medium, the information cannot accept a recording rate, which has not been recorded. Further, the information is recorded during a production step of the recording medium, which causes a reduction in production efficiency and an increase in manufacturing cost due to an increase in production steps. In addition, a countermeasure may be insufficient when recording at a calculated recording power is difficult in a system.
In a high-speed or high-density recording system, a recording distortion is generated due to reproduction interference or thermal interference between marks, which tends to cause signal distortion in a reproduced signal when recorded data is reproduced. Accordingly, there is a problem in that recording quality suddenly deteriorates due to signal distortion. However, in the methods of the above-described documents, a countermeasure against this problem has not been taken into account. Accordingly, a stable recording environment is rarely provided due to the occurrence of signal distortion.
Accordingly, it is an object of certain inventive aspects to provide a method of optimizing a recording condition depending on compatibility between a drive and a medium. It is another object of certain inventive aspects to provide a method which is available for obtaining an appropriate recording condition even in case of high-speed recording where test recording is difficult, and a method which is available for setting an optimum recording condition preventing the occurrence of signal distortion in case of CAV (constant angular velocity) or CLV (constant linear velocity) recording where a recording rate changes from an inner circumference toward an outer circumference.
In order to achieve the above-described objects, according to a first aspect of the invention, an optical information recording apparatus for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes means for generating signal distortion in a test region of the medium by test recording onto the medium, means for specifying a recording condition with the signal distortion generated, and means for setting conditions of the recording pulse with a condition corresponding to the set recording condition as an upper limit.
As such, by setting the recording condition with the signal distortion generated using test recording, high-quality recording can be performed with no distortion. Moreover, the signal distortion means a state where distortion is generated in a reproduced signal due to a factor leading to a change by recording distortion, other than deformation of a pregroove constituting the medium or the like even when a pit is formed in a desired shape as well as when the shape of a pit is distorted due to known thermal interference or the like.
Moreover, the condition corresponding to the specified recording condition serving as the upper limit includes giving a margin in a certain range relative to a distortion generation condition.
According to a second aspect of the invention, an optical information recording apparatus for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes means for performing test recording onto the medium while gradually changing the conditions of the recording pulse, means for acquiring recording characteristics obtained by reproducing the result of test recording for every condition gradually changed, means for detecting change amounts in recording characteristics according to the change of the condition, means for specifying a maximum value of the detected change amounts and specifying a condition corresponding to the maximum value, and means for setting the conditions of the recording pulse with the condition corresponding to the specified condition as an upper limit.
As such, by specifying a region where the change in recording characteristic is the maximum, the generation region of the signal distortion can be suitably specified.
According to a third aspect of the invention, an optical information recording apparatus for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes means for performing test recording in a test region provided on an inner circumference side of the medium at a first rate, means for determining a power of the recording pulse at the first rate based on the result of test recording, means for determining a power of the recording pulse at a second rate higher than the first rate by using the determined power at the first rate, means for detecting signal distortion generated within the test region, means for specifying a power with which the detected signal distortion is generated, means for specifying a distortion generating power at the second rate by using the specified distortion generating power, and means for reducing the power of the recording pulse and/or increasing a duty in case that the determined power at the second rate is more than a power corresponding to the distortion generating power at the second rate.
Moreover, the power corresponding to the distortion generating power serving as the upper limit of the power includes a power having a margin in a certain range relative to the distortion generating power.
As such, by specifying the power with which the signal distortion is generated, and setting the recording condition with the condition corresponding to the power as the upper limit, high-quality recording can be performed with no distortion. For example, when the power is more than the upper limit, by increasing the duty, the amount of required energy can be ensured in a state where the increase in power is restricted. Therefore, even when the power already reaches the upper limit, a recording rate can be improved.
According to a fourth aspect of the invention, the optical information recording apparatus according to the third aspect of the invention may further include means for reducing a recording rate in case that the power of the recording pulse is more than the power corresponding to the distortion generating power even when the reduction in power and/or the increase in duty are performed.
As such, in case that only the reduction in power or the increase in duty is insufficient, by reducing the recording rate, high-speed recording can be maintained without drastically reducing the recording rate.
According to a fifth aspect of the invention, an optical information recording apparatus for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes means for performing test recording in a test region provided on an inner circumference side of the medium at a first rate, means for determining a duty of the recording pulse at the first rate based on the result of test recording, means for determining a duty of the recording pulse at a second rate higher than the first rate by using the determined duty at the first rate, means for detecting the signal distortion generated within the test region, means for specifying a duty with which the detected signal distortion is generated, means for specifying a distortion generating duty at the second rate by using the specified distortion generating duty, and means for reducing the power of the recording pulse and/or increasing a duty in case that the determined duty at the second rate is more than a duty corresponding to the distortion generating duty at the second rate.
As such, by specifying the duty with which the signal distortion is generated, and setting the recording condition with the duty corresponding to the specified duty as the upper limit, high-quality recording can be performed with no distortion. For example, when the duty is more than the upper limit, by reducing the power, the amount of required energy can be ensured in a state where the increase in duty is restricted. Therefore, even when the duty already reaches the upper limit, a recording rate can be improved.
Moreover, the duty corresponding to the distortion generating duty serving as the upper limit of the duty includes a duty having a margin in a certain range relative to the distortion generating duty.
Further, according to a sixth aspect of the invention, the optical information recording apparatus according to the fifth aspect of the invention may further include means for reducing a recording rate in case that the duty of the recording pulse is more than the duty corresponding to the distortion generating duty even when the reduction in power and/or the increase in duty are performed.
As such, in case that only the reduction in power or the increase in duty is insufficient, by reducing the recording rate, high-speed recording can be maintained without drastically reducing the recording rate.
According to a seventh aspect of the invention, an optical information recording apparatus for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes means for performing test recording in a test region provided on an inner circumference side of the medium at a first rate, means for determining a condition of the recording pulse at the first rate based on the result of test recording, means for determining a condition of the recording pulse at the second rate higher than the first rate by using the determined condition at the first rate, means for detecting the signal distortion generated within the test region, means for specifying a condition with which the detected signal distortion is generated, means for obtaining the relationship between the specified distortion generation condition and the determined condition at the first rate, means for specifying a distortion generation condition at the second rate by using the obtained relationship, and means for performing recording in a recording region provided on an outer circumference side from the test region at the second rate.
As such, the distortion generation condition for the rate capable of test recording is specified, and the distortion generation condition at the rate having a difficulty in test recording is specified by using the specified distortion generation condition. Therefore, in case of high-speed recording, high-quality recording can be also performed with no distortion.
In addition, the recording condition appropriate to each recording rate is obtained by test recording before actual data recording. Therefore, a medium or a drive which does not have information for the determination of a recording condition in advance can be accepted. As a result, a variation in characteristic of a medium or a drive can be absorbed, thereby improving stability of a system or productivity of a medium or a drive.
According to an eighth aspect of the invention, an optical information recording apparatus for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes means for performing test recording in a test region provided on an inner circumference side of the medium at a first rate, means for determining a condition of the recording pulse at the first rate based on the result of test recording, means for determining a condition of the recording pulse at a second rate higher than the first rate by using the determined condition at the first rate, means for detecting signal distortion within the test region, means for specifying a condition with which the detected signal distortion is generated, means for specifying a distortion generation condition at the second rate by using the specified distortion generation condition, means for judging whether or not recording can be performed in the recording region provided on the outer circumference side from the test region at the second rate with no distortion, by using the determined distortion generation condition at the second rate, means for changing a recording rate based on the judgment result, and means for reporting a recording rate after the judgment.
As such, by reporting the recording rate after the judgment, a user can know the limit value of the recording rate depending on the combination of a medium and a drive. When more high-speed and high-quality recording is desired, an index for selecting a high-sensitive medium fit to the drive can be provided.
The report of the recording rate is performed by a method which clearly states a recordable rate depending on the combination of a medium and a drive or a rate after the recording rate is reduced, by use of monitor display or the like.
According to a ninth aspect of the invention, an optical information recording apparatus for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes means for performing test recording in a test region provided on an inner circumference side of the medium at a first rate, means for determining a condition of the recording pulse at the first rate based on the result of test recording, means for determining a condition of the recording pulse at a second rate higher than the first rate by using the determined condition at the first rate, means for detecting signal distortion within the test region, means for specifying a condition with which the detected signal distortion is generated, means for specifying a distortion generation condition at the second rate by using the specified distortion generation condition, means for judging whether or not recording can be performed in the recording region provided on the outer circumference side from the test region at the second rate with no distortion, by using the determined distortion generation condition at the second rate, means for changing a recording rate based on the judgment result, and means for storing a recording condition after the judgment. In this case, the determination of the recording pulse condition at the second rate is performed by using the stored recording condition.
As such, by storing a high-speed recording condition obtained from a low-speed recording condition through the prediction in a memory of the drive, or the test region or the recording region of the medium, the prediction of a recording power at the time of next high-speed recording can be efficiently performed.
Here, the recording condition after the judgment to be stored includes the condition of the recording pulse, the distortion generation condition, other characteristics or relational expressions obtained from test recording, and the judgment results.
According to a tenth aspect of the invention, an optical information recording method for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes generating signal distortion in a test region of the medium by test recording onto the medium, specifying a recording condition with which the signal distortion is generated, and setting a condition of the recording pulse with a condition as corresponding to the specified recording condition as an upper limit.
According to an eleventh aspect of the invention, an optical information recording method for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes performing test recording onto the medium while gradually changing the condition of the recording pulse, acquiring recording characteristics obtained by reproducing the result of test recording for every condition gradually changed, detecting change amounts in recording characteristics according to the change of the condition, specifying a maximum value of the detected change amounts and specifying a condition corresponding to the maximum value, and setting a condition of the recording pulse with a condition as corresponding to the specified condition as an upper limit.
According to a twelfth aspect of the invention, an optical information recording method for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes performing test recording at a first rate in a test region provided on an inner circumference side of the medium, determining a power of the recording pulse at the first rate based on the result of test recording, determining a power of the recording pulse at a second rate higher than the first rate by using the determined power at the first rate, detecting signal distortion generated within the test region, specifying a power with which the detected signal distortion is generated, specifying a distortion generating power at the second rate by using the specified distortion generating power, and reducing the power of the recording pulse and/or increasing a duty in case that the determined power at the second rate is more than a power corresponding to the distortion generating power at the second rate.
According to a thirteenth aspect of the invention, an optical information recording method for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes performing test recording at a first rate in a test region provided on an inner circumference side of the medium, determining a duty of the recording pulse at the first rate based on the result of test recording, determining a duty of the recording pulse at the second rate higher than the first rate by using the determined duty at the first rate, detecting the signal distortion generated within the test region, specifying a duty with which the detected signal distortion is generated, specifying a distortion generating duty at the second rate by using the specified distortion generating duty, and reducing the power of the recording pulse and/or increasing a duty in case that the determined duty at the second rate is more than a duty corresponding to the distortion generating duty at the second rate.
According to a fourteenth aspect of the invention, an optical information recording method for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes performing test recording at a first rate in a test region provided on an inner circumference side of the medium, determining a condition of the recording pulse at the first rate based on the result of test recording, determining a condition of the recording pulse at the second rate higher than the first rate by using the determined condition at the first rate, detecting the signal distortion generated within the test region, specifying a condition with which the detected signal distortion is generated, obtaining the relationship between the specified distortion generation condition and the determined condition at the first rate, specifying a distortion generation condition at the second rate by using the obtained relationship, and performing recording in a recording region provided on an outer circumference side from the test region at the second rate.
According to a fifteenth aspect of the invention, an optical information recording method for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes performing test recording at a first rate in a test region provided on an inner circumference side of the medium, determining a condition of the recording pulse at the first rate based on the result of test recording, determining a condition of the recording pulse at the second rate higher than the first rate by using the determined condition at the first rate, detecting the signal distortion generated within the test region, specifying a distortion generation condition with which the detected signal distortion is generated, specifying a distortion generation condition at the second rate by using the specified distortion generation condition, judging whether or not recording can be performed in the recording region provided on the outer circumference side from the test region at the second rate with no distortion, by using the determined distortion generation condition at the second rate, changing a recording rate based on the judgment result, and reporting a recording rate after the judgment.
According to a sixteenth aspect of the invention, an optical information recording method for recording information onto an optical recording medium by irradiating laser light based on a recording pulse includes performing test recording at a first rate in a test region provided on an inner circumference side of the medium, determining a condition of the recording pulse at the first rate based on the result of test recording, determining a condition of the recording pulse at the second rate higher than the first rate by using the determined condition at the first rate, detecting the signal distortion generated within the test region, specifying a distortion generation condition with which the detected signal distortion is generated, specifying a distortion generation condition at the second rate by using the specified distortion generation condition, judging whether or not recording can be performed in the recording region provided on the outer circumference side from the test region at the second rate with no distortion, by using the determined distortion generation condition at the second rate, changing a recording rate based on the judgment result, and storing a recording condition after the judgment. In this case, the determination of the recording pulse condition at the second rate is performed by using the stored recording condition.
According to a seventeenth aspect of the invention, there is provided a signal processing circuit incorporated into an optical information recording apparatus configured to irradiate laser light based on a recording pulse for recording information onto an optical information medium at multiple rates, and configured by the optical information recording method according to any one of the tenth to sixteenth aspects.
Preferably, in certain aspects of the invention, there is provided a method for detecting the generation condition of ‘signal distortion’ by test recording to be performed before actual data recording. Further, there is also provided a method for predicting the generation condition of ‘signal distortion’ at the time of speed recording assigned with the generation condition of ‘signal distortion’ at the time of test recording at a recordable recording rate in case that an assigned recording rate is a condition having a difficulty in test recording. And then, the optimum recording PW and the optimum pulse condition in consideration with the generation condition of ‘signal distortion’ are determined as the optimum recording condition, thereby providing a stable recording and reproducing system.
Here, in certain aspects of the invention, the determination of the recording power at each recording rate is preferably performed such that a predetermined estimation parameter when data which was actually recorded at each recording rate is reproduced becomes a predetermined value or is in a predetermined range.
The predetermined estimation parameter includes an estimation index using amplitude information such as a β value, an asymmetry value, or a modulation index of the reproduced signal, or an estimation index using time or length information such as a jitter value or an error rate of the reproduced signal.
The predetermined value or the predetermined range includes a target level derived from the result of test recording performed before data recording or a target level previously set for each recording rate.
A condition of high-speed recording to be performed on the inner circumference side is calculated by using the condition obtained by low-speed recording performed on the inner circumference side, which results in obtaining a recording condition for a rate at which recording cannot be performed on the inner circumference side. This effect markedly appears when a rate at which recording can be performed in the test region is a first rate and a rate at which recording cannot be performed in the test region is a second rate.
Further, by using the change in characteristic of the result of test recording by at least two rates, a high-speed recording condition under which test recording can be performed with difficulty can be predicted from a low-speed recording condition capable of test recording. Moreover, a rate to be used for test recording preferably includes an allowable maximum rate in the test region.
Further, the relationship between the power and the duty for a rate capable of test recording is obtained, and the power or duty for a rate having a difficulty in test recording is temporarily set. Then, by using the relationship between the power and the duty, a power or a duty for a rate having a difficulty in test recording is obtained. Therefore, a high-speed recording condition having a difficulty in test recording can be predicted from a low-speed recording condition capable of test recording.
Here, a method for deriving the relationship between the power and the duty may derive the relationship by test recording, may read out a previously stored value, or may derive the relationship by the previously stored value and test recording.
The relationship between the power and the duty is preferably calculated as an expression or a coefficient. Further, a duty condition for each recording rate may be fixed to the maximum value derived with the recording rate condition capable of test recording or may be changed for every recording rate.
A change in duty of the recording pulse may be performed by changing the entire length of the recording pulse having a top pulse and a following pulse, may be performed by changing only the length of the top pulse, or may be performed by changing only the length of the following pulse.
Recording quality of a maximum density pulse having a high appearance frequency at which recording is extremely performed can be improved by changing the top pulse as an example of the change in duty. Therefore, an optimum recording environment can be provided.
Further, for the detection of the signal distortion, preferably, recording is performed with at least two recording conditions, and signal quality when recorded data is reproduced is used as an estimation parameter. As the estimation parameter, a jitter, an error rate, length information of one or plural mark data, or amplitude information of one or plural mark data when recorded data is reproduced can be used.
As a recording pattern to be used for test recording when detecting the signal distortion, a predetermined specific pattern or a random pattern can be used.
When predicting the generation condition of the signal distortion, from a predetermined prediction expression by using the distortion generation condition detected through test recording at a predetermined recording rate, a distortion generation condition in case of a recording rate different from the predetermined recording rate can be predicted. Here, the predetermined prediction expression can include a prediction function stored in a drive in advance, a prediction function stored in a medium, and a prediction function obtained when test recording.
In certain aspects of the invention, the recording pulse preferably has a top pulse and a following pulse. The top pulse is configured to correspond to the shortest pit that has the highest appearance frequency and the difficulty in recording. For example, in either case of a pit train having 3T to 11T for CD-R or a pit train having 3T to 11T and 14T for DVD-R, the top pulse preferably corresponds to the 3T pit. In either case of marks 2T to 8T for a Blue-ray system or marks 2T to 8T for an HD-DVD system, the top pulse preferably corresponds to the 2T mark.
Further, the following pulse can be configured to be a non-multi-pulse or a multi-phase. In case of a non-multi-pulse, a recording pulse is preferably optimized based on a power ratio of the top pulse to the following pulse. In case of a multi-pulse, a recording pulse is preferably optimized by adjusting a duty of each of a plurality of divided pulses constituting the following pulse.
Conditions of the top and following pulses may be determined in any combination of a pulse power, a pulse width, and a duty. Preferably, a recording pulse is optimized by adjusting a ratio of the top pulse to the following pulse.
The determination of the following pulse after the determination of the top pulse allows the realization of more stable recording quality. That is, the determination of an optimum top pulse condition is first performed, which results in finding the optimum top pulse condition. And then, a following pulse condition is determined. In contrast, as described in JP-2004-110995, the optimization of the ratio of the top pulse to the following pulse is preferentially performed, which leads to the reduction in accommodation capability for a medium unknown to a drive because sometimes an optimum solution for the top pulse is not obtained. Moreover, in order to improve accuracy, the determination of the top pulse condition followed by the determination of the following pulse condition may be repeated several times.
As described above, according to certain inventive aspects, in case of a medium unknown to a drive, a recording condition closer to an optimum can be obtained. In particular, in case of high-speed recording having a difficulty in test recording, a recording condition effective for avoiding signal distortion can be obtained.
An optical information recording apparatus according to certain inventive aspects will now be described in detail with reference to the accompanying drawings. Moreover, the invention may be modified from time to time, and shall not be limited to the embodiments described herein.
When a length of the recording pulse is n′T, the top pulse 12 has a length of m′T, and the following pulse 14 has a length of (n−m)T, where m and n in this embodiment have the values of m=3 and n=3 to 11 or 14, respectively, and T is a unit time defined in an optical disc system, a frequency of which is determined by a clock signal.
A condition of the recording pulse 10 is determined by executing the flow shown in
As shown in
When the information is recorded onto the medium 50, a recording signal corresponding to desired recording information is encoded in an EFM format by an encoder 101 and then encoded recording data is transmitted to a strategy circuit 102.
The strategy circuit 102 involves various setting parameters set for a predetermined strategy. The strategy circuit 102 generates a recording pulse that is expected to result in a desired recording state by controlling intensity or a pulse width of the laser beam emitted from the laser oscillator 103 through the correction of various setting parameters for the strategy.
The recording pulse formed by the strategy circuit 102 is transmitted to the laser oscillator 103, which controls an output laser beam in accordance with the recording pulse and irradiates the controlled laser beam onto the medium 50 rotating at a constant linear or rotational velocity through a lens 104, a half mirror 105, and a lens 106, whereby a recorded pattern having a pit/land train corresponding to desired recording data is recorded onto the medium 50.
On the other hand, when the information recorded onto the medium 50 is reproduced, a homogeneous reproducing laser beam emitted from the laser oscillator 103 is irradiated onto the medium 50 rotating at a constant linear or rotational velocity through the lens 104, the half mirror 105, and the lens 106.
The reproducing laser beam, which has less intensity than the laser beam emitted from the laser oscillator 103 during recording, is reflected at the medium 50, and the reflected laser beam from the medium 50 is received by a photo-receiving part 108 through the lens 106, the half mirror 105, and a lens 107, and then is converted into an electrical signal.
The electrical signal output from the photo-receiving part 108 corresponds to a recorded pattern having pits and lands recorded onto the medium 50. The electrical signal output from the photo-receiving part 108 is also used for extracting a clock signal with a predetermined frequency from a wobble component included in the electrical signal by a synchronizing signal detection circuit 109. The electrical signal is further binarized by a binarization circuit 110, then is decoded by a decoder 111, and is finally output as a reproduced signal.
As described above, recording quality in a recording system having a drive and a medium depends on a variation in characteristics of the drive and the medium. Accordingly, absorbing the influence of the dependence with the strategy allows the improvement of the recording quality. In addition, any of various optical information recording mediums including a dye-based medium represented by CD-R or DVD-R and a phase-change medium represented by CD-RW or DVD-RW can be applied to one embodiment.
The flow for determining a recording pulse condition to be executed by the drive described above, shown in
Determination of m′T Condition
Determination of Reference Condition
At the step S110 shown in
Determining of Reference Threshold
As will be described below, because one embodiment is intended to set a region below the jitter threshold as a range for the test recording condition (hereinafter, referred to as ‘test region’), the threshold serving as the judgment reference needs to be determined. A standard value depending on the kinds of a drive or a medium may be prepared for the threshold. The threshold representing a minimum line of a jitter allowable region varies depending on conditions of optical components and other elements constituting a pickup device shown in
Accordingly, it is recommended to set a more accurate test region by obtaining the threshold for every combination of a drive and a medium to be actually used and then giving a more accurate judgment reference.
However, setting the threshold for every combination of a drive and a medium results in the increase in the number of recording processes. Accordingly, the threshold appropriate to each drive may be stored in a storage region 115 during drive manufacturing, assuming that the variation in characteristics between respective drives is a major factor in the variation in threshold.
First, the step S150 for setting a recording condition is executed. At this step, predetermined patterns of conditions necessary for recording/reproducing, including a pulse width, power, a recording/reproducing rate, a recording address, and the like, are prepared. After the recording conditions are set to a drive, a reference medium is loaded in the drive. Preferably, as the reference medium, a medium with standard characteristics is selected from various mediums.
Next, by executing the step S152 for recording and reproducing the loaded reference medium under the recording condition set at the step S150, recording/reproducing characteristic values, such as jitters, are acquired under the respective recording conditions. As the characteristic values to be acquired at this step, values representing recording quality are selected.
Subsequently, the best value, such as a minimum jitter value, is obtained from the recording/reproducing characteristic values acquired at the step S152, and then the step S154 is executed with the best value as a system reference value. Accordingly, a jitter value deemed to be close to an optimum value for the drive is set as the reference value. Moreover, the reference value may be an intermediate value between two points at which a curve approximated for the jitters crosses a predetermined threshold, that is, an intermediate value of a power margin, instead of the optimum jitter value.
Finally, the step S156 is executed for calculating the threshold by multiplying the system reference value determined at the step S154 by a predetermined coefficient α (preferably α>1). Accordingly, the judgment is performed by using the system reference value including the predetermined margin. That is, the threshold can be calculated using the system reference value based on the expression Threshold=(System reference value)×α, where the value of the coefficient α is preferably about 1.5. Moreover, the coefficient α may have an appropriate value depending on a kind of a drive or a medium. For example, a value in a range of α=0.8 to 1.2 may be set so that the threshold is close to the system reference value, or alternatively, a larger value in a range of α=2.0 to 3.0 may be set.
Moreover, in case of simplifying a setting process for a threshold, a mean value may be calculated from the thresholds 1 to 5 obtained by recording/reproducing the information recorded on the common reference medium by some standard drives, and then the mean threshold may be used as the threshold for other drives.
The standard drives used for calculating the mean threshold may be identically designed ones or similarly designed ones instead of identically designed ones. The mean threshold may also be used as a threshold for the standard drives. Further, the calculated mean threshold may generally be used as a threshold for identically designed or similarly designed drives to be manufactured afterward. In addition, the mean threshold may be determined by calculating a mean value for a plurality of drives that have the variation in characteristics and are intentionally prepared.
Initialization of Recording Apparatus
The step S114 is executed for storing the reference condition and the reference threshold, which are described above and determined at the steps S110 and S112 in
Loading Medium to be Recorded
Subsequently, the step S116 is executed for loading the medium 50 onto which the information is to be recorded into the drive 100 already initialized at the step S114.
Recording/Reproducing Under Reference Condition
Under the condition set at the step S114, the step S118 is executed for recording onto the medium 50 loaded at the step S116. Specifically, three jitter values are obtained by recording/reproducing three times using one pulse width and three power values defined as the reference condition. Plotting the three jitter values against the power yields a clear tendency of recording characteristics depending on the combination of the drive 100 and the medium 50.
Inspection of Recording Quality
Referring to
This means that an optimum condition is easily detected in case of
That is, in case that the difference between the reproduced value and the reference reproduced value is small, the optimum condition is close to the above-described reference condition, while the optimum condition is distant from the reference condition in case that the difference is large. Consequently, when the reduction of the number of test recording is desired, it is preferable to vary the number of test runs depending on the difference between the reproduced value and the reference reproduced value.
Further, because the minimum jitter value is considered to exist on the higher power side in case of the downward-sloping patterns as shown in
Further, in case of the downward-sloping patterns, the optimum solution is considered to be further from the reference condition compared with the case of the downwardly convex patterns described above with reference to
Further, because the minimum jitter value is considered to exist on the lower power side in case of the upward-sloping patterns as shown in
Further, in case of the upward-sloping patterns, the optimum solution is considered to be further from the reference condition compared with the case of the downwardly convex patterns described above with reference to
Determination of Test Region
The approximated curve 206 varies depending on the pulse width. Accordingly, in case that the pulse width used as the reference condition is W4, recording is performed at the power values of P1, P2, and P3 for each of the pulse widths W1 to W6 centering on W4. Consequently, the approximated curve 206 can be obtained for each of the pulse widths W1 to W6, and the cross points of the approximated curve 206 with the threshold can be checked for each pulse width. Accordingly, a power range having a jitter equal to or less than the threshold is obtained for each pulse width and a hatched region in a matrix shown in
As such, because obtaining the power range for each pulse width can lead to intensive test runs in the region having a jitter equal to or less than the threshold, more appropriate condition may be found with a smaller number of test runs.
Moreover, the number of test runs can be reduced by setting a larger step amount for a power change in case of a large power margin or by setting a smaller step amount for a power change in case of a small power margin. For example, in case of a 10 mW margin, test recording may be performed five times with a step amount of 2 mW, assuming that an optimum value can be obtained even with rough tests. On the other hand, in case of a 1 mW margin, test recording may be performed ten times with a step amount of 0.1 mW due to the necessity of precise tests.
The test region determined in such a procedure has a shape in which a plane region defined by (power)×(pulse width) centering on the reference condition 208-1, 208-2, and 208-3 is shifted to a higher power side. In case of the downward-sloping patterns, a power range may be determined by shifting the test region to a wider pulse width region from the pulse widths W1 to W6 due to low sensitivity of the medium to be recorded, although the example uses the pulse widths W1 to W6, which are used for the case of the downwardly convex patterns.
The test region determined in such a procedure has a shape in which a plane region defined by (power)×(pulse width) centering on the reference condition 208-1, 208-2, and 208-3 is shifted to a lower power side. In case of the upward-sloping patterns, a power range may be determined by shifting the test region to a narrower pulse width region from the pulse widths W1 to W6 due to high sensitivity of the medium to be recorded, although the example uses the pulse widths W1 to W6, which are used for the case of the downwardly convex patterns.
That is, in the above-described method, because recording quality is inspected for each pulse width and the number of test runs is determined for the each pulse width based on the inspection result, the reduction in the number of test runs can be expected. The inspection of recording quality described above is an example of a case where the inspection is performed by patterning a jitter change depending on recording under the reference conditions. More preferably, it is recommended to perform the inspection by using eight patterns described below.
Subsequently, a curve approximation is performed for jitter characteristics obtained from additional recording and the region between two cross points of the approximated curve with the jitter threshold is applied to a reference power range.
Further, in case of the pattern 1, the pulse width region of the reference value ±0.2 T is determined as the test region and the optimum recording condition is detected while changing the pulse width by 0.2 T at a time in the test region during test recording, where T represents a unit time length of a recording pit.
If the pulse width serving as the reference value is denoted by a pulse condition 1 and the two expanded points are denoted by pulse conditions 2 and 3, the pulse conditions 2 and 3 of the pattern 1 correspond to the pulse widths after the ±0.2 T expansion respectively. With the change of the pulse width condition, a power range to be used as a test condition is also slightly changed.
For example, when a pulse width is varied by 0.1 T, (reference power range)×(1−0.05×1) mW is applied to a power range for the changed pulse width. Further, when a pulse width is changed by 0.2 T, (reference power range)×(1−0.05×2) mW is applied to a power range for the changed pulse width, and when a pulse width is changed by −0.1 T, (reference power range)×(1−0.05×(−1)) mW is applied to a power range for the changed pulse width.
Accordingly, in case of the pattern 1, the test condition involves the following three sets:
(1) Reference pulse width and Reference power range
(2) (Reference pulse width)−0.2 T, and (Reference power range)×(1−0.05×(−2)) mW
(3) (Reference pulse width)+0.2 T, and (Reference power range)×(1−0.05×(+2)) mW
Moreover, in one embodiment, the reference condition shown in the above-described (1) is not necessarily used for actual test recording.
The pattern 2 corresponds to the case of downwardly convex patterns and can be applied when the minimum jitter value is equal to or less than the threshold. In case of the pattern 2, ((reference pulse width) ±0.1 T) is selected as the pulse width condition based on an idea that the medium to be recorded has the same sensitivity as the reference medium. Subsequently, by the same procedure as that of the pattern 1, the power range is set for each of the pulse widths. Consequently, the test condition in case of the pattern 2 involves the following three sets:
(1) Reference pulse width and Reference power range
(2) (Reference pulse width)−0.1 T, and (Reference power range)×(1−0.05×(−1)) mW
(3) (Reference pulse width)+0.1 T, and (Reference power range)×(1−0.05×(+1)) mW
The pattern 3 corresponds to the case of downwardly convex patterns and can be applied when the minimum jitter value is more than the threshold. In case of the pattern 3, ((reference pulse width) ±0.2 T) is selected as the pulse width condition, based on an idea that the medium to be recorded has the same sensitivity as the reference medium and the difference in feature between them is large. Subsequently, by the same procedure as that of the pattern 1, the power range is set for each of the pulse widths. Consequently, the test condition in case of the pattern 3 involves the following three sets:
(1) Reference pulse width and Reference power range
(2) (Reference pulse width)−0.2 T, and (Reference power range)×(1−0.05×(−2)) mW
(3) (Reference pulse width)+0.2 T, and (Reference power range)×(1−0.05×(+2)) mW
The pattern 4 corresponds to the case of downward-sloping patterns and can be applied when the minimum jitter value is equal to or less than the threshold. In case of the pattern 4, three points including the reference pulse width, ((reference pulse width)+0.1 T), and ((reference pulse width)+0.2 T) are selected as the pulse width condition based on an idea that the medium to be recorded has slightly lower sensitivity than the reference medium. Subsequently, by the same procedure as that of the pattern 1, the power range is set for each of the pulse widths. Consequently, the test condition in case of the pattern 4 involves the following three sets:
(1) Reference pulse width and Reference power range
(2) (Reference pulse width)+0.1 T, and (Reference power range)×(1−0.05×(+1)) mW
(3) (Reference pulse width)+0.2 T, and (Reference power range)×(1−0.05×(+2)) mW
The pattern 5 corresponds to the case of downward-sloping patterns and can be applied when the minimum jitter value is more than the threshold. In case of the pattern 5, three points including the reference pulse width, ((reference pulse width)+0.2 T), and ((reference pulse width)+0.4 T) are selected as the pulse width condition, based on an idea that the medium to be recorded has significantly lower sensitivity than the reference medium. Subsequently, by the same procedure as that of the pattern 1, the power range is set for each of the pulse widths. Consequently, the test condition in case of the pattern 5 involves the following three sets:
(1) Reference pulse width and Reference power range
(2) (Reference pulse width)+0.2 T, and (Reference power range)×(1−0.05×(+2)) mW
(3) (Reference pulse width)+0.4 T, and (Reference power range)×(1−0.05×(+4)) mW
The pattern 6 corresponds to the case of upward-sloping patterns and can be applied when the minimum jitter value is equal to or less than the threshold. In case of the pattern 6, three points including the reference pulse width, ((reference pulse width)−0.1 T), and ((reference pulse width)−0.2 T) are selected as the pulse width condition, based on an idea that the medium to be recorded has slightly higher sensitivity than the reference medium. Subsequently, by the same procedure as that of the pattern 1, the power range is set for each of the pulse widths. Consequently, the test condition in case of the pattern 6 involves the following three sets:
(1) Reference pulse width and Reference power range
(2) (Reference pulse width)−0.1 T, and (Reference power range)×(1−0.05×(−1)) mW
(3) (Reference pulse width)−0.2 T, and (Reference power range)×(1−0.05×(−2)) mW
The pattern 7 corresponds to the case of upward-sloping patterns and can be applied when the minimum jitter value is more than the threshold. In case of the pattern 7, three points including the reference pulse width, ((reference pulse width)−0.2 T), and ((reference pulse width)−0.4 T) are selected as the pulse width condition, based on an idea that the medium to be recorded has significantly higher sensitivity than the reference medium. Subsequently, by the same procedure as that of the pattern 1, the power range is set for each of the pulse widths. Consequently, the test condition in case of the pattern 7 involves the following three sets:
(1) Reference pulse width and Reference power range
(2) (Reference pulse width)−0.2 T, and (Reference power range)×(1−0.05×(−2)) mW
(3) (Reference pulse width)−0.4 T, and (Reference power range)×(1−0.05×(−4)) mW
The pattern 8 corresponds to the case of upwardly convex patterns and can be applied when the maximum jitter value is more than the threshold. In case of the pattern 8, ((reference pulse width)±0.2 T) is selected as the pulse width condition, based on an idea that the patterns are abnormal. Subsequently, by the same procedure as that of the pattern 1, the power range is set for each of the pulse widths. Consequently, the test condition in case of the pattern 8 involves the following three sets:
(1) Reference pulse width and Reference power range
(2) (Reference pulse width)−0.2 T, and (Reference power range)×(1−0.05×(−2)) mW
(3) (Reference pulse width)+0.2 T, and (Reference power range)×(1−0.05×(+2)) mW
Moreover, in case of the detection of a pattern other than the pattern 2 that is closest to the reference medium among the eight patterns, a jitter may be detected again by further reproducing the recording result from which the pattern is obtained in order to confirm that the pattern is not due to a reproducing error. In this case, if a pattern other than the pattern 2 is again detected by the further reproduction, the recording condition may be added and expanded according to the condition shown in
Here, in case of the detection of the pattern 8 as a result of the above-described confirmation of the reproducing error, because the recording error can be considered, recording is again performed with the reference pulse width before additional recording or pulse width expansion. If the pattern 8 is once again detected by reproducing recording, additional recording is performed with the pulse width expansion, that is, the expansion of the pulse conditions 2 and 3, instead of the power extension to measure the margin for the pulse condition 1. The power expansion according to the expansion of the pulse conditions 2 and 3 may be performed by the above-described method.
That is, in case of the pattern 8, the margin cannot be ensured under the pulse condition 1, and therefore the power range that is a basis for the power extension cannot be obtained. Accordingly, an initial power condition is set as the reference power range.
Determination of Test Region: Determination of Power Range by Approximation Method
The test region effective for obtaining the optimum solution with a smaller number of test runs is determined by performing the above-described method. In addition, a method for the determination of the power range important to the determination of the test region will hereinafter be described.
In one embodiment, in order to improve the accuracy of finding the optimum solution with the smallest possible number of test runs, the test condition is focused on the region in which a jitter is equal to or less than the threshold or less, as described above. According to this concept, the power range to be used for test recording may be obtained from two power values that indicate the margin for the threshold. The margin for the threshold means a range in which a characteristic value equal to or less than the threshold can be obtained, and the two power values mean values on the lower and higher power sides that define the margin range.
Considering the reduction in test recording time and the efficient use of a test recording region of a medium, such as a write-once medium, in which the test recording region is limited, the number of recording points for test recording is preferably smaller. However, higher accuracy is much more needed for the power range because the power range is an important parameter as a judgment reference of the optimum recording condition.
Because obtaining the accurate power range leads to the test runs that are to be performed intensively in a more accurately selected region, it contributes to the reduction in the number of test runs. For example, when test recording is performed at a frequency of once per 0.1 mW, test recording is performed ten times for the power range of 1 mW. Further, in case of 2 mW, test recording is performed twenty times. Accordingly, narrowing a power range contributes to the reduction in the number of test runs.
Therefore, one embodiment propounds a method for obtaining a desired margin amount by approximating a characteristic curve using some recorded points, paying attention to recording quality of recording/reproducing signals that shows a change like a quadratic curve having an extreme value as an optimum point against recording power. Application of such an approximation method allows the power range with high accuracy to be easily obtained with some recording points and can reduce the number of test runs.
a>b, c>b, and threshold>b
The term ‘vicinity’ of the threshold is defined as a range between the upper and lower limits that are higher and lower than the threshold by certain amounts respectively. Preferably, the upper and lower limits are set to be higher and lower than the threshold by 40% and 5% thereof respectively. The a, b and c values are then approximated with a quadratic function and the region between the two cross points of the quadratic function with the threshold is applied to the power range. Moreover, the range to be defined as the vicinity of a threshold may be changed, such as −5% to +40%, −10% to +30%, or the like, in consideration of the interval between the recording points.
In addition, in the case of B>C, as shown in
At this time, because the relationship between the three recording points and the threshold are ‘A>C, D>C, and threshold>C’, which are appropriate for drawing an approximated curve, the approximated curve with high accuracy can be obtained with a three-point approximation. Moreover, an additional recording condition for the point D may be determined depending on the relationship among the recording points A, B, and C before additional recording, that is, ‘A>B and B>C’, and on the threshold.
Further, in case that a jitter value does not exist in the vicinity of the threshold on a lower power side, contrary to the case of
A power to be used for additional recording reference may be changed with a power step different from a predetermined power step and a power condition included in the additional recording condition may be set based on the previously obtained relationship of the change in jitter to the change in power.
In addition, in case that recording points enough to determine the power range are not obtained even with the additional recording condition described above, another recording point should be obtained again by adding a further recording condition by the same procedure as described above.
In case of a write-once medium, the test recording region of which is limited, in order to avoid the use of a large amount of test time, the number of the above-described additional recording conditions may have an upper limit, and an additional recording power may have an upper limit so as not to exceed a laser power due to the addition of the recording condition.
Further, in the above-described example, the power range is determined by the three-point approximation, but a power range may be determined in such a manner that two closest points to the threshold are first selected and then a different between two power values corresponding to the two closest points is applied to the power range.
An alternative method for selecting two points in the vicinity of the threshold may include, after recording is performed while changing a power until two points located on either side of the threshold is found, selecting two closest points to the threshold among the recording points or selecting the two points located on either side of the threshold. The method will hereinafter be described in detail.
Determination of Test Region: Determination of Power Range by Sampling
That is, as shown in
A method for selecting two points which are close to the threshold involves the following methods, one of which may be selected and used from time to time:
(1) A method for selecting two points which define the power margin, that is, selecting two points which are located in a power region meeting the reference reproduced value and are both the two closest points to the reference reproduced value
(2) A method for selecting two points which are located slightly outside the power margin and are both the two closest points to the reference reproduced value
(3) A method for selecting two points which are located on the lower power side and on either side of the reference reproduced value
(4) A method for selecting two points which are located on the higher power side and on either side of the reference reproduced value
(5) A method for selecting two points which are located on the lower and higher power sides respectively and on either side of the reference reproduced value and which are both the two closest points to the reference reproduced value
Further, an alternative method may further include selecting two cross points of an approximated curve, which is obtained using the two points selected by any one of the above-described methods, with the reference reproduced value.
Determination of m′T/(n−m)T Ratio
Here, an energy amount of the entire recording pulse is defined by the height of a main power PW and the length of a top pulse width Ttop defines an energy amount of the initial stage of the recording pulse that is provided to the front edge of a recording pit. The main power PW preferably corresponds to the highest value in each of the recording pulses 10-1 and 10-2, and the top pulse width Ttop has a width corresponding to the shortest recording pit having a length of 3T. Because the recording pulse having the shortest pulse width has the highest appearance probability and significantly influences recording quality, optimum conditions of the power PW and the width Ttop of the top pulse 12 are first determined by the m′T condition determination flow described above.
Subsequently, a condition of the following pulse 14 is determined by the m′T/(n−m)T ratio determination flow. In case of the single pulse 10-1, as shown in
Next, after the recorded patterns formed by test recording are reproduced (Step S212), reproduced binarized signals output from the binarization circuit 110 as a result of the reproduction are counted by a counter, which is synchronized with a predetermined clock, in a recording shift detection part 112 (Step S214). Then, the lengths of pits and lands included in the reproduced binarized signals are stored in the storage region 115 as count data (Step S216).
Next, the recording shift detection part 112 prepares a histogram representing an appearance frequency for every count by using count data stored in the storage region 115 (Step S218). Then, the thresholds for count results that are to be reference for the lengths of pits and lands are determined from the histogram (Step S220).
Subsequently, the recording shift detection part 112 searches various types of specific patterns including a specific pit/land pattern from count data stored in the storage region 115 with the thresholds as references (Step S222). Next, average lengths of respective pits and respective lands constituting the specific patterns are calculated by averaging the count results for the pits considered to have the same pit length included in the specific patterns and by averaging the count results for the lands considered to have the same land length (Step S224).
Subsequently, the recording shift detection part 112 sets one of various types of specific patterns extracted as an extracted pattern, and compares the length of a recording pit included in the extracted pattern with a reference length (Step S226). Next, the recording shift detection part 112 detects a shift length of the pit with respect to the recording pulse (Step S228).
Subsequently, an equation derivation part 113 derives an equation for determining an optimum strategy based on the shift length detected by the recording shift detection part 112. A strategy determination part 14 predicts a control result by various parameters by using the equation derived by the equation derivation part 113 (Step S230). Further, the strategy determination part 14 determines PWD or Tmp shown in
The details of respective steps from the search of specific patterns (Step S222) to the detection of shift lengths (Step S228) shown in
If the length of the variable pit PyT is measured, the length of the variable pit PyT should correspond to a predetermined pit length in an ideal recording condition.
However, in case that the length of the variable pit PyT is shifted with respect to the predetermined pit length, the shift amount from the defined length of the variable pit PyT corresponds to the shift length of the pit length of each of the pits P3T to P14T, that is, 3T to 14T, relative to the recording pulse generated with a strategy during recording because the land lengths of the lands LxT and LzT are both fixed.
Accordingly, using the reproduced pattern for test recording performed with a certain strategy, as shown in (b) to (f) of
Subsequently, count results for each of the land LxT, the pit PyT, and the land LzT are sorted, and the sorted count results are then averaged for each of the land LxT, the pit PyT, and the land LzT (Step S224 in
The shift lengths D1 and D2 detected as described above vary depending on various setting parameters of a strategy. And then, it has been found that the shift varying depending on various setting parameters of the strategy changes almost linearly as a result of analysis.
That is, the shift length to be detected for each test recording by the above-described recording shift detection part 112 can be considered as a point on a line approximated by a least-square method.
Therefore, in the drive of one embodiment, an optimum strategy can be determined in consideration of the linear relationship between various setting parameters of the strategy and the detected shift lengths D1 and D2 in case that test recording is performed two times. Besides, in the embodiment, a curve approximation may also be used instead of the linear approximation.
That is, PWD in case of the single pulse or Tmp in case of the multi-pulse is a typical parameter to be changed depending on the recording condition S1 or S2. With changing the parameter from S1 to S2, the effect of the change on the shift length is detected as the change from D1 to D2. Using the four values, the linear approximation is performed and the use of the approximated line results in obtaining the correction amount that can cancel the shift length.
As a result of test recording, a pattern S1 shown in (a1) is obtained for the recording pulse S1 and a pattern S2 shown in (b1) is obtained for the recording pulse S2. A shift length of D1 occurs in the pattern S1 according to the control amount S1 and a shift length of D2 occurs in the pattern S2 according to the control amount S2.
If the values of the shift lengths D1 and D2 for the control amounts S1 and S2 are known, a shift length occurring from a control amount for any of the parameters can be predicted. Therefore, using the relationship between the change in control amount and the change in shift length, the prediction of a control amount and the determination of a correction value are performed.
Further, in the example shown in
As such, the relationship between the change in strategy from S1 to S2 and the change in shift amount from D1 to D2 can be obtained by a linear or curve approximation if at least two points are obtained for each of the changes. Therefore, the optimum correction amount leading to a zero shift length can be obtained by using the approximated line or curve.
More specifically, some shift lengths D are first obtained while changing a strategy S. Next, by substituting the relationship between the strategy S and the shift amount D into a general expression ‘D=a×S+b’, simultaneous equations are obtained. By solving the simultaneous equations, constants a and b of the expression are calculated, resulting in obtaining an optimum strategy S for an ideal shift amount. Finally, by setting the optimum strategy S to the strategy circuit 102 shown in
For example, in case that a shift amount detected from a reproduced pattern for test recording with one strategy S1 and another shift amount detected from a reproduced pattern for test recording with another strategy S2 by the recording shift detection part 112 shown in
D1=a×S1+b
D2=a×S2+b
From the above equations, the constants a and b are calculated and the following function using the constants a and b calculated is derived:
S=(D−b)/a
By substituting a value to improve recording quality, for example, the output shift amount D to correct for an initial output shift or the like occurring in an equalizer or the like, to the above function, the optimum strategy S can be determined.
Further, in the example shown in
At this time, because PWD and Tmp have values obtained under the fixed top pulse condition, the values are with reference to an optimum m′T/(n−m)T ratio determined based on an mT pulse condition. Accordingly, the nT pulse having the top and following pulses is appropriate to improve recording quality. However, at this moment, a phase condition has not yet been determined, and therefore a phase condition determination flow to be described below is further performed to obtain the optimum strategy.
Correction for Phase Shift
As shown in
Next, after the recorded pattern formed by the test recording is reproduced (Step S412), reproduced binarized signals obtained from the binarization circuit 110 as a result of the reproduction is counted by a counter, which is synchronized with a predetermined clock, in the recording shift detection part 112 (Step S414), and the lengths of pits and lands included in the reproduced binarized signals are stored in the storage region 115 as count data (Step S416).
Subsequently, the recording shift detection part 112 prepares a histogram representing an appearance frequency for every count by using count data stored in the storage region 115 (Step S418) and determines thresholds for count results that are to be reference for the length of pits and lands from the histogram (Step S420).
Subsequently, the recording shift detection part 112 searches various types of specific patterns including a specific pit/land pattern from count data stored in the storage region 115 using the thresholds as references (Step S422) and respectively calculates average lengths of pits and lands constituting the specific patterns by averaging count results considered to be for the same pit length included in the specific patterns and by averaging count results considered to be for the same land length (Step S424).
Subsequently, the recording shift detection part 112 sets one of various types of specific patterns extracted as a reference pattern, and compares the reference pattern with other patterns (Step S426) to independently detect each of the following shift amounts (Step S428):
(1) A phase shift amount on the front side of a pit relative to a recording pulse
(2) A phase shift amount on the rear side of a pit relative to a recording pulse
(3) A shift length of a pit relative to a recording pulse due to thermal interference.
Subsequently, the equation derivation part 113 derives an equation for determining an optimum strategy based on the shift amount detected by the recording shift detection part 112. Using the equation derived by the equation derivation part 113, the strategy determination part 114 predicts a control result for various parameters (Step S430). Further, in the strategy determination part 114, based on the prediction result, Ttopr and Tlast shown in
Several steps of the flow shown in
If the length of the fixed land LyT in each of the recording patterns is measured, the length should be constant in an ideal recording condition. However, in case that the length of the fixed land LyT is shifted relative to a predetermined length, the shift length relative to the predetermined length corresponds to the phase shift amount on the front side of each of the pits P3T to P14T corresponding to 3T to 14T of recording pulses generated with a strategy during recording because the length of the fixed pit PxT is fixed.
Accordingly, by comparing the length of a fixed land LyT in a reference pattern with a length of a fixed land LyT in each comparative pattern, the phase shift amount on the front side of the each comparative pattern relative to the reference pattern can be obtained as FPS4T, FPS5T, FPS6T or FPS7T. Here, the reference pattern means a pattern in which the length of the variable pit PzT is 3T as shown in (b) and the comparative pattern means any of the other patterns as shown in (c) to (f).
The phase shift amount FPS3T, FPS4T, FPS5T, FPS6T or FPS7T may be detected as a relative value based on a certain part, and therefore a phase shift amount on the front side of the reference pattern FTS3T may be defined as zero or as a shift amount relative to an ideal length. Further, any one of the patterns shown in (c) to (f) may be defined as a reference pattern instead of the pattern shown in (b).
If the length of the fixed land LyT in each of the recording patterns is measured, the length should be constant in an ideal recording condition. However, in case that the length of the fixed land LyT is shifted relative to a predetermined length, the shift length relative to the predetermined length corresponds to a phase shift amount on the rear side of each of the pits P3T to P14T corresponding to 3T to 14T of recording pulses generated with a strategy during recording because the length of the pit PzT is fixed.
Accordingly, by comparing the length of a fixed land LyT in a reference pattern with a length of a fixed land LyT in each comparative pattern, the phase shift amount on the rear side of the each comparative pattern relative to the reference pattern can be obtained as RPS4T, RPS5T, RPS6T or RPS7T. Here, the reference pattern means a pattern in which a length of the variable pit PxT is 3T as shown in (b) and the comparative pattern means any of the other patterns as shown in (c) to (f).
The phase shift amount RPS3T, RPS4T, RPS5T, RPS6T or RPS7T may be detected as a relative value based on a certain part, and therefore a phase shift amount on the rear side of the reference pattern RTS3T may be defined as zero or as a shift amount relative to an ideal length. Further, any one of the patterns shown in (c) to (f) may be defined as a reference pattern instead of the pattern shown in (b).
If the length of the fixed pit PyT in each of the recording patterns is measured, the length should be constant in an ideal recording condition. However, in case that the length of the fixed pit PyT is shifted relative to a predetermined length, the shift length relative to the predetermined length corresponds to a shift length due to thermal interference occurring from a pit formed immediately before the each variable land LxT because the length of the land LzT is fixed.
Accordingly, by comparing the length of a fixed pit PyT in a reference pattern with the length of a fixed pit PyT in each comparative pattern, the shift amount on the front side of the each comparative pattern relative to the reference pattern can be obtained as HID3T, HID4T, HID5T, HID 6T or HID7T. Here, the reference pattern means a pattern in which the length of the variable land LxT is 3T as shown in (b) and the comparative pattern means any of the other patterns as shown in (c) to (f).
The shift amount HID3T, HID4T, HID5T, HID 6T or HID7T may be detected as a relative value based on a certain part, and therefore a shift amount on the front side of the reference pattern HID3T may be defined as zero or as a shift amount relative to an ideal length. Further, any one of the patterns shown in (c) to (f) may be defined as a reference pattern instead of the pattern shown in (b).
Subsequently, count results corresponding to the pit PxT, the land LyT, and the pit PzT are sorted and averaged (equivalent to the step S424 in
As a result of test recording, a reference pattern shown in (a1) is obtained for the recording pulse shown in (a), a comparative pattern S1 shown in (b1) is obtained for the recording pulse shown in (b), and a comparative pattern S2 shown in (c1) is obtained for the recording pulse shown in (c). Here, a shift amount D1 occurs in the comparative pattern S1 from the control amount of S1 and a shift amount D2 occurs in the comparative pattern S2 from the control amount S2.
If the values of the shift amounts D1 and D2 for the control amounts S1 and S2 are known, the relationship between a shift amount and a control amount for any of the parameters can be predicted. Therefore, using the relationship between the change in control amount and the shift amount, the prediction of a control amount and the determination of a correction value are performed.
In the example shown in
As such, the relationship between the change in strategy from S1 to S2 and the change in shift amount from D1 to D2 can be obtained by a linear or curve approximation if at least two different points are obtained for each of the changes. Therefore, an optimum correction amount leading to a zero shift amount can be obtained by using the approximated line or curve.
More specifically, some shift amounts D are first obtained while changing a strategy S. Next, by substituting the relationship between the strategy S and the shift amount D at that time into a general expression ‘D=a×S+b’, simultaneous equations are obtained. By solving the simultaneous equations, constants a and b in the expression are calculated, resulting in obtaining an optimum strategy S for an ideal shift amount D. Finally, by setting the optimum strategy S to the strategy circuit 102 shown in
For example, in case that a shift amount detected from a reproduced pattern for test recording with one strategy S1 and another shift amount detected from a reproduced pattern for test recording with another strategy S2 by the recording shift detection part 112 shown in
D1=a×S1+b
D2=a×S2+b
From the above equations, constants a and b are calculated and the following function using the constants a and b calculated is derived:
S=(D−b)/a
By substituting a value to improve recording quality, for example, an output shift amount D to correct for an initial output shift or the like occurring in an equalizer or the like, into the above function, an optimum strategy S can be determined.
Moreover, the function to obtain an optimum strategy S may be derived for each of the pits P3T, P4T, . . . and P14T corresponding to 3T, 4T, . . . and 14T respectively. Further, the function to obtain an optimum strategy S may be derived for each recording rate.
In case of the correction for a pit having a length equal to 4T or more, a PWD correction value for the length of the pit is read out from the table shown in
Moreover, in the embodiments described above, an optimum strategy S is determined by substituting a shift amount D into a function for obtaining the optimum strategy S. However, the strategy S may be determined based on a correction table obtained using the function.
The above optimum strategy S may be set whenever the type of an optical disc is changed or a recording rate is changed. Further, an optimum strategy condition set above may be stored in a memory for every optical disc type or for every recording rate, and then the optimum strategy may be read out from the memory and used when recording is performed with the optical disc type or recording is performed with the recording rate.
In the example shown in
Further, as shown in
Here, a difference between an allowable recording rate on the inner circumference side and an allowable recording rate on the outer circumference side occurs due to the rotation limitation of a spindle motor or the like. For example, in case of DVD-R, 16× recording can be performed on the outermost circumference with ability of a current spindle motor. On the other hand, in the test region 52 provided on the inner circumference, 6× recording is performed at the utmost.
Accordingly, as shown in
Here, as shown in
As described above, the energy amount of the entire recording pulse is defined with the height indicated by the main power PW, and the energy amount of the initial stage which is provided to the front edge of a recording pit is defined with the length indicated by the top pulse width Ttop. Therefore, in case that the main power PW tends to exceed the upper limit of the power of the laser oscillator 103 with the improvement of the recording rate, the length of the top pulse width Ttop is increased while the power within the upper limit is suppressed. As a result, an energy amount required for high-speed recording can be ensured.
The top pulse width Ttop has a width corresponding to the shortest recording pit having the length of 3T. The shortest recording pulse has the highest appearance probability and significantly influences recording quality. Therefore, when increasing the duty of the recording pulse, the length of the top pulse width Ttop is first increased. When the increase in length of the top pulse width Ttop is still insufficient, the length of the entire recording pulse is increased.
As shown in
For example, as shown in
Moreover, when increasing the duty, a duty after the increase is determined by adding a required amount with a duty of a recording rate capable of test recording indicated by a dotted line in
A method shown in each of
In this method, regardless of whether or not the power reaches the upper limit of the laser output, the duty condition is increased with the increase in recording rate, thereby expanding the maximum recording rate with a power equal to or less than the upper limit of the laser output.
Next, the power and duty for every rate of 8× to 16× having a difficulty in executing with the test region are predicted by using change coefficients of the power and the duty of 2× to 6× obtained by test recording (Step s502).
Next, when the predicted power exceeds the upper limit of the laser oscillator (YES at the step S504), the power for the recording rate is reduced, and the duty for the recording rate is increased (Step S506). On the other hand, when the predicted power is equal to or less than the upper limit of the laser oscillator (NO at the step S504), the power is determined as the condition for the recording rate, and then the process ends.
Subsequently, when the duty increased at the step S506 exceeds the upper limit of the duty (YES at the step S508), the recording rate is reduced, and then recording is performed under a condition meeting the upper limit of the power and the upper limit of the duty (Step S510). Here, the upper limit of the duty includes a value which is previously set for every mark length as an allowable duty having influence on the identification of the mark length. On the other hand, when the increased duty is equal to or less than the upper limit (NO at the step S508), the duty is determined for the recording rate, and then the process ends.
For example, the power of 4× is set to be lower than the power of 6×. Accordingly, when the power of 6× is p, the power of 4× is set to a power obtained by subtracting the coefficient 2 from the power of 6×. Further, because the power of 8× is set to be higher than the power of 6×, the power of 8× is set to a power obtained by adding 2 to the power p of 6×. Moreover, the duty condition for each rate is set to a value obtained for 6×.
Next, the power and the duty for each rate from 8× to 16× having a difficulty in executing with the test region are predicted by using the change coefficient of the power and the duty for 2× to 6× obtained by test recording (Step S602).
Next, when the predicted power exceeds the upper limit of the laser oscillator (YES at the step S604), the power for the recording rate is reduced (Step S606). On the other hand, the predicted power is equal to or less than the upper limit of the laser oscillator (NO at the step S604), the power is determined as the condition for the recording rate, and then the process ends.
Subsequently, when the power increased at the step S606 still exceeds the upper limit of the power (YES at the step S608), the duty is increased (Step S610).
Subsequently, when the duty increased at the step S610 exceeds the upper limit of the duty (YES at the step S612), the recording rate is reduced, and thus recording is performed under a condition meeting the upper limit of the power and the upper limit of the duty (Step S614). On the other hand, when the increased duty is equal to or less than the upper limit of the duty (NO at the step S612), the duty is determined as a condition for the recording rate, and then the process ends.
Subsequently, a function approximation is performed by using the power and the duty at the two points (Step S622), and the power and the duty for a rate having a difficulty in measuring with the test region, for example, up to 8× to 16×, are predicted by using the approximated function (Step S624).
If each recording rate is substituted into the parameter x of the resultant ‘y=5.5298*1n(x)+0.0361’, the power and duty values y for each rate can be obtained. In this example, the power and duty values of 8×=12, 12×=14, and 16×=15 are obtained.
Accordingly, even when the optimum power Po exceeds the upper limit Plimit of the laser output, the recording power is not immediately reduced to be equal to or less than the upper limit of the laser output at an allowable recording rate. The recording power is reduced to an allowable level within the margin range, thereby expanding the highest recording rate.
The allowable level may be set by directly using the recording power. Preferably, the allowable level is determined by using an index such as β or asymmetry correlated with the recording power. Further, the allowable level may be a previously set value or may be a value derived from the result of test recording to be performed before actual data recording.
For example, test recording at 4× and 6× capable of test recording is performed, and the relationship between the power and the duty indicated by a line in the drawing is obtained by using values indicated by black circles in the drawing. Further, the optimum power for each rate from 8× to 16× having a difficulty in test recording is temporarily set in advance, and the duty for each rate having a difficulty in test recording is obtained by using the relationship between the power and the duty. Therefore, values indicated by white circles in the drawing can be obtained. As a result, the high-speed recording condition having a difficulty in test recording can be suitably predicted from the low-speed recording condition capable of test recording.
Similarly, test recording at 4× and 6× capable of test recording is performed, and the relationship between the power and the duty indicated by a line in the drawing is obtained by using values indicated by black circles in the drawing. Further, the optimum power for each rate from 8× to 16× having a difficulty in test recording is temporarily set in advance, and the power for each rate having a difficulty in test recording is obtained by using the relationship between the power and the duty. Therefore, values indicated by white circles in the drawing can be obtained. As a result, the high-speed recording condition having a difficulty in test recording can be suitably predicted from the low-speed recording condition capable of test recording.
Moreover, the relationship between the power and the duty is preferably obtained as an expression or coefficient. Further, the duty condition for each recording rate may be fixed to the optimum value derived with the recording rate condition capable of test recording or may be changed for each recording rate.
As shown in (a), in the obtained RF signal with no thermal interference or recording distortion, the signal levels of the pits on both sides of the land are the same. As shown in (b), however, in the RF signal with thermal interference, heat when the formation of the preceding pit interferes when the formation of the subsequent pit, and the signal level obtained from the subsequent pit is different from that of the normal state.
On the other hand, as shown in (c), in the RF signal having the recording distortion, for example, the signal level obtained from the preceding pit is different from that of the normal state due to an optical influence of a pregroove deformed when the formation of the subsequent pit. The recording distortion has influence on the reproduction of the pits before and after the part having the distortion, and thus it is difficult to specify a generation source or generation condition.
For example, as shown in
As shown in
This is because, when recording is performed with the recording power to be higher than the optimum point and the recording pulse width to be longer than the optimum point, the recording state becomes an excessive storage state. When the excessive storage exceeds a predetermined level, the recording distortion occurs.
Accordingly, the excessive storage state can be formed while changing the recording condition, and a part where the degradation tendency of recording quality appears can be detected as the recording distortion generation condition. Specifically, as shown in
Moreover, although a detection method uses the jitter as the estimation parameter in the example shown in
For example, when high-speed recording having a difficulty in test recording is assigned to an arbitrary recording medium by a user, as shown in
For example, based on the result of test recording at 2×, 4×, and 6× indicated by black circles in the drawing, a curve for a power increase ratio from 6× to 16× having a difficulty in test recording is obtained, and the distortion generation conditions of 2×, 4×, and 6× indicated by the same black circles are obtained by test recording. From the relationship between these distortion generation conditions and the curve for a power increase ratio, the distortion characteristic ratios k2, k4, and k6 for individual rest rates are obtained.
Subsequently, the distortion characteristic ratios k2, k4, and k6 are averaged so as to obtain the distortion characteristic ratio k in a high-speed region from 6× to 16×. Further, by multiplying the curve for a power increase ratio by the distortion characteristic ratio k, the distortion generation conditions for individual rates from 6× to 16× are specified.
Moreover, the distortion characteristic ratio k of the high-speed region may be obtained by using only one distortion characteristic ratio in the test region, for example, k6 obtained by test recording of 6×. Although a case for predicting the distortion generation power is described in the example shown in
In the method for predicting the optimum condition shown in
Specifically, in case that a curve representing the distortion generation power for each rate shown in
More specifically, recording can be performed with no distortion by using the distortion generation power obtained by test recording as the upper limit of the power of the step S504 shown in
Similarly, recording can be performed with no distortion by using the distortion generation power obtained by test recording as the upper limit of the power of the steps S604 and S608 shown in
In addition, the optimum power is preferably set to be sufficiently smaller than the distortion generation power in consideration of a variation in laser output or an influence of fresh air. Specifically, the margin of about 0.8 to 0.9 is preferably provided between the optimum recording power and the distortion generation power. Moreover, like the recording power, the optimum condition of the recording pulse width can be determined with no distortion.
According to one embodiment, even in case of a medium unknown to a drive, a recording condition closer to an optimum can be obtained, and thus a closer accommodation to a recording environment is expected.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-092253 | Mar 2005 | JP | national |
