JP3800491B2 - Recording state judgment method for optical disc - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recording state judgment how the writable optical disk.
[0002]
[Prior art]
In general, an optical disc such as a CD-R (Compact Disc Recordable) has a basic structure in which a recording layer made of an organic dye film is provided on a transparent substrate and a reflective layer is further provided thereon.
[0003]
This type of optical disk rotates at a constant linear velocity and irradiates a laser beam along a spiral recording track formed on the recording layer from the transparent substrate side to form a series of pit rows corresponding to desired recording information. Information recording is performed by forming the recording track.
[0004]
The laser beam at the time of information recording is irradiated in response to a recording pulse based on the recording information. For example, when the recording pulse is at a high level, the recording layer of the optical disk is altered by irradiation with high intensity and on the recording track. When the recording pulse is at a low level, only a recording track is tracked without irradiating the recording layer of the optical disk with a low intensity when the recording pulse is at a low level.
[0005]
However, if the high-intensity laser beam is uniformly irradiated during the high level period of the recording pulse, that is, the pit formation period, the heat that has not been used to form the pits is accumulated in the recording layer as surplus heat. As a result, shape distortion and edge misalignment occur in the formed pits, resulting in degradation of the RF signal.
[0006]
Therefore, there is generally a technique for adjusting the amount of energy that the laser beam provides to the optical disc by appropriately correcting the recording pulse using a known pulse train method, powered method, rectangular method, etc., and suppressing the generation of excess heat. It is used.
[0007]
[Problems to be solved by the invention]
In recent years, a technique has been proposed that enables high-speed recording on an optical disc by increasing the rotation speed of the optical disc and increasing the period of the reference recording pulse based on the recorded information in response to this.
[0008]
In recent optical discs, further increase in storage capacity is required, and accordingly, optical discs with higher density are being studied.
[0009]
However, the higher the recording speed and the higher the recording density of the optical disc, the more likely the pit shape formed on the optical disc will vary greatly and the RF signal will be more likely to deteriorate. It becomes necessary to correct the recording pulse.
[0010]
Accordingly, the present invention is for the correction of the recording pulse higher-precision ones, and to provide a recording state judgment how the optical disc that can be easily detected deterioration condition of the RF signal.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 irradiates a laser beam whose output is controlled on the basis of a recording pulse corresponding to desired information onto an optical disk, and forms a series of pit rows on a recording track of the optical disk. In the recording state determination method for an optical disc to be formed, a series of pit strings formed on the optical disc are read, a plurality of read signals for a predetermined length of pits are extracted from the read read signal, and the predetermined read signal is based on the extracted read signal Measure the signal length of each of the long pits, determine the distribution of the respective deviation amounts with respect to the correct signal length of the plurality of measured signal lengths, and if the obtained distribution has bimodality, the recording state on the optical disc is It is characterized by determining that it is not appropriate.
[0012]
According to a second aspect of the present invention, there is provided a recording state in an optical disc in which a laser beam whose output is controlled based on a recording pulse corresponding to desired information is irradiated on the optical disc to form a series of pit rows on a recording track of the optical disc. In the determination method, a series of pit strings formed on the optical disc is read, an eye pattern of a reproduction signal is created from the read signal, and a predetermined spot shorter than the spot diameter of the laser beam is created from the eye pattern of the created reproduction signal. A blur width at a peak portion of the eye pattern with respect to a long pit is detected, and when the detected blur width exceeds a predetermined value, it is determined that a recording state on the optical disc is not appropriate.
[0013]
According to a third aspect of the present invention, there is provided a recording state in an optical disc in which a laser beam whose output is controlled based on a recording pulse corresponding to desired information is irradiated on the optical disc to form a series of pit rows on a recording track of the optical disc. In the determination method, a series of pit rows formed on the optical disc is read, a read signal for a pit having a predetermined length longer than the spot diameter of the laser beam is extracted from the read signal, and the leading end of the extracted read signal If there is an abnormal amplitude at the front end or rear end of the read signal, it is determined that the recording state on the optical disc is not appropriate. It is characterized by that.
[0016]
Embodiments of a recording state determination method for an optical disc according to the present invention will be described below in detail with reference to the accompanying drawings.
[0017]
FIG. 1 is a block diagram showing a part of the configuration of an optical disc recording / reproducing apparatus constructed by applying the present invention.
[0018]
In the optical disc recording / reproducing apparatus shown in FIG. 1, recording information is input to an encoder 11, encoded and modulated into an EFM (Eight to Fourteen Modulation) signal, etc., and output as a pulsed recording signal (recording pulse).
[0019]
The strategy storage unit 21 stores an optimum recording strategy corresponding to the type and recording speed of the optical disk obtained by conducting an experiment or the like in advance. The strategy selecting unit 22 stores the type of optical disk to be used and the recording speed. The corresponding recording strategy is read from the strategy storage unit 21 in accordance with the above, and the read recording strategy information is output to the recording pulse correction unit 12.
[0020]
Note that the recording strategy represents a correction form of the recording pulse, and is information necessary for setting a multi-pulse in the pulse train method, for example.
[0021]
The recording pulse output from the encoder 11 is input to the laser control circuit 17 after being corrected in accordance with the type, linear velocity, etc. of the optical disk used in the recording pulse correction unit 12.
[0022]
The recording pulse correction unit 12 corrects the recording pulse input from the encoder 11 based on information input from the strategy selection unit 22 and the strategy correction value calculation unit 23.
[0023]
The laser control circuit 17 controls the LD driver 18 according to the recording pulse corrected by the recording pulse correction unit 12, and the LD driver 18 drives a laser diode (not shown) included in the optical pickup 19 to generate a corrected recording pulse. A corresponding pulsed laser beam is irradiated onto the recording surface of the optical disc 30 to form pits to record information.
[0024]
In the optical disk recording / reproducing apparatus of the present invention, in order to further correct the recording strategy based on the RF signal degradation status, trial writing is performed prior to information recording, as will be described later, and the RF signal degradation status. Is detected.
[0025]
This trial writing is performed, for example, in a trial writing area (PCA: Power Control Area) of the optical disc 30.
[0026]
First, a sample recording pulse for evaluating the degradation state of the RF signal is input to the recording pulse correction unit 12, and the strategy selection unit 22 stores the strategy according to the type, recording speed, etc. of the optical disc 30. Based on the recording strategy read from the unit 21, the sample recording pulse is corrected and output.
[0027]
The sample recording pulse is a recording pulse that can form a pit row in which pits having a length of 3T to 11T are arbitrarily arranged at intervals of 3T to 11T.
[0028]
The optical pickup 19 irradiates a laser beam corresponding to the corrected sample recording pulse by moving directly under the test writing area of the optical disc 30 and forms a pit row corresponding to the sample recording pulse in the test writing area.
[0029]
Next, the optical pickup 19 irradiates a pit row formed in the test writing area of the optical disc 30 with a laser beam for information reproduction, converts the amount of return light into an electric signal, and reproduces the electric signal as an RF signal. Input to unit 15.
[0030]
The RF signal reproducing unit 15 reproduces an RF signal corresponding to the pit string formed in the test writing area of the optical disc 30 based on the electric signal input from the optical pickup 19, and the reproduced RF signal is used as the RF signal evaluating unit. 16
[0031]
As will be described later, the RF signal evaluation unit 16 analyzes and evaluates the input RF signal to detect its deterioration state, and inputs it to the strategy correction value calculation unit 23.
[0032]
The strategy correction value calculation unit 23 calculates the correction value of the recording strategy selected by the strategy selection unit 22 based on the deterioration state of the RF signal input from the RF signal evaluation unit 16 and inputs the correction value to the recording pulse correction unit 12. To do.
[0033]
The recording pulse correction unit 12 corrects the recording strategy input from the strategy selection unit 22 based on the correction value input from the strategy correction value calculation unit 23, and inputs from the encoder 11 based on the corrected recording strategy. Recording on the optical disc 30 is performed by correcting the recording pulse corresponding to the recorded information to be output and outputting it to the laser control circuit 17.
[0034]
Next, an RF signal analysis and evaluation method in the RF signal evaluation unit 16 will be described below.
[0035]
(First evaluation method)
FIG. 2 is a flowchart illustrating an example of an RF signal analysis and evaluation method in the RF signal evaluation unit 16.
[0036]
This evaluation method detects the signal length of a plurality of RF signals for a pit of a predetermined length, calculates the distribution status of deviation amounts (that is, jitter) with respect to the correct signal length, and detects the distortion of the RF signal from the calculated distribution status To do.
[0037]
If the recording state is good, the deviation amount distribution should show a narrow unimodality, and if it has two or more peaks, the signal length of each signal varies accordingly. Can be judged as bad.
[0038]
In this evaluation method, the RF signal evaluation unit 16 extracts a signal corresponding to a pit having a predetermined length, for example, a signal corresponding to a 3T pit, from the RF signal reproduced by the RF signal reproduction unit 15 (step 201). The length is measured (step 202).
[0039]
The RF signal evaluation unit 16 stores the correct signal length of the RF signal for the 3T pit, measures the deviation of the measured signal length with respect to the correct signal length (step 203), and extracts this operation from the RF signal. This is performed for signals corresponding to all 3T pits to be performed (step 204), and the distribution of deviation amounts is obtained (step 205).
[0040]
When the distribution state of the deviation amount is unimodal as shown in FIG. 3A (YES in step 206), it is determined that the recording state is good (step 207), as shown in FIG. 3B. If it has two peaks (NO in step 206), it is determined that the recording state is bad.
[0041]
Note that the distribution state of the shift amount is not limited to the bimodality, and a distribution state having a multimodality having several peaks may be obtained. Therefore, the bimodality as shown in FIG. It is determined that the recording state is not good not only when the distribution state is obtained but also when a multi-modal distribution is obtained.
[0042]
In this embodiment, the RF signal corresponding to the 3T pit has been described as an example of the RF signal corresponding to the pit having a predetermined length. However, of course, RF signals corresponding to other types of pits may be used.
[0043]
(Second evaluation method)
FIG. 4 is a flowchart illustrating an example of an RF signal analysis and evaluation method in the RF signal evaluation unit 16.
[0044]
This evaluation method obtains an eye pattern of an RF signal, detects a blur width of a peak corresponding to a predetermined length pit of the obtained eye pattern, and evaluates a deterioration state of the RF signal. The RF signal is evaluated based on the blur width of the portion corresponding to the pit shorter than the spot diameter formed by the laser beam on the recording surface of the optical disc 30.
[0045]
Here, 3T pits will be described as an example of pits shorter than the spot diameter.
[0046]
The RF signal evaluation unit 16 obtains an eye pattern of the RF signal reproduced by the RF signal reproduction unit 15 (step 301), detects a pattern corresponding to the 3T pit from the obtained eye pattern (step 302), and detects the detected 3T. The blur width of the peak portion of the pattern corresponding to the pit is detected (step 303).
[0047]
If the blur width is within a predetermined range as shown in FIG. 3 (a) (YES in step 304), it is determined that the recording state is good (step 305), and is large as shown in FIG. 3 (b). If it is blurred (NO in step 304), it is determined that the recording state is bad (step 306).
[0048]
(Third evaluation method)
FIG. 6 is a flowchart illustrating an example of an RF signal analysis and evaluation method in the RF signal evaluation unit 16.
[0049]
Usually, the peak portion of the amplitude of the RF signal corresponding to a pit longer than the spot diameter is substantially flat as shown in FIG. 7A, but due to the influence of excess heat, as shown in FIG. The peak portion of the amplitude may not be substantially flat but may be partially distorted.
[0050]
Therefore, in this embodiment, the RF signal is evaluated by detecting distortion in the peak portion of the amplitude of the RF signal corresponding to a pit longer than the spot diameter (hereinafter referred to as amplitude abnormality).
[0051]
Here, an 11T pit will be described as an example of a pit longer than the spot diameter.
[0052]
The RF signal evaluation unit 16 extracts a signal corresponding to the 11T pit from the RF signal reproduced by the RF signal reproduction unit 15 (step 401), and checks whether or not the extracted RF signal has an abnormal amplitude (step 402).
[0053]
This inspection is performed on signals corresponding to all 11T pits extracted from the RF signal (step 403), and the ratio of signals having an amplitude abnormality to all extracted signals is determined (step 404). If it is below the predetermined value (YES in step 405), it is determined that the recording state is good (step 406), and if it is above the predetermined value (NO in step 405), it is determined that the recording state is bad (step 407). ).
[0054]
FIG. 7B shows an example of the RF signal waveform in the case where there is an amplitude abnormality at the rear end portion of the signal corresponding to the 11T pit. Of course, an amplitude abnormality may be detected at the front end portion. Yes, the detection of the amplitude abnormality described above is to detect both of these abnormalities.
[0055]
Although the three RF signal analysis / evaluation methods have been described above, the RF signal analysis / evaluation unit 16 analyzes the RF signal by at least one of the three methods and detects the deterioration state.
[0056]
【The invention's effect】
As described above, according to the present invention, the deterioration state of the RF signal can be easily detected, so that the recording strategy can be corrected in detail based on the deterioration state of the RF signal. Since the correction becomes highly accurate, pits with high accuracy can be formed on the recording surface of the optical disc.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram showing a partial configuration of an optical disc recording / reproducing apparatus according to the present invention.
FIG. 2 is a flowchart illustrating an example of an RF signal evaluation unit 16;
FIG. 3 is a diagram showing a jitter distribution of an RF signal having a predetermined length.
4 is a flowchart illustrating an example of an RF signal evaluation unit 16. FIG.
FIG. 5 is a diagram showing an example of distortion of an RF signal corresponding to a short pit.
6 is a flowchart illustrating an example of an RF signal evaluation unit 16. FIG.
FIG. 7 is a diagram illustrating an example of distortion of an RF signal corresponding to a long pit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Encoder 12 Recording pulse correction | amendment part 15 RF signal reproduction | regeneration part 16 RF signal evaluation part 17 Laser control circuit 18 LD driver 19 Optical pick-up 21 Strategy memory | storage part 22 Strategy selection part 23 Strategy correction value calculation part 30 Optical disk

Claims (3)

In a recording state determination method in an optical disc in which a laser beam whose output is controlled based on a recording pulse corresponding to desired information is irradiated on the optical disc to form a series of pit rows on a recording track of the optical disc.
Read a series of pit rows formed on the optical disc,
Extracting a plurality of read signals for a predetermined length of pits from the read read signal,
Measure the signal length of the predetermined length pits based on the extracted read signal,
Obtain the distribution of each deviation amount with respect to the correct signal length of the plurality of measured signal lengths,
When the obtained distribution has bimodality, it is determined that the recording state with respect to the optical disc is not appropriate. In a recording state determination method in an optical disc in which a laser beam whose output is controlled based on a recording pulse corresponding to desired information is irradiated on the optical disc to form a series of pit rows on a recording track of the optical disc.
Read a series of pit rows formed on the optical disc,
Create an eye pattern of the reproduction signal from the read signal read,
Detecting a blur width at the peak portion of the eye pattern with respect to a pit having a predetermined length shorter than the spot diameter of the laser beam from the eye pattern of the generated reproduction signal;
A recording state determination method for an optical disc, wherein when the detected blur width exceeds a predetermined value, it is determined that the recording state on the optical disc is not appropriate. In a recording state determination method in an optical disc in which a laser beam whose output is controlled based on a recording pulse corresponding to desired information is irradiated on the optical disc to form a series of pit rows on a recording track of the optical disc.
Read a series of pit rows formed on the optical disc,
Extracting a read signal for a pit having a predetermined length longer than the spot diameter of the laser beam from the read signal,
Detecting whether there is an abnormal amplitude at the leading end or the trailing end of the extracted read signal,
A recording state determination method for an optical disc, characterized in that if the detection detects that there is an abnormal amplitude at the leading end or the trailing end of the read signal, the recording state on the optical disc is determined to be inappropriate.

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