Abstract:
An optical disk apparatus which has first and second light-emitting elements for emitting laser beams, and records data on a recording medium with laser beams from the first and second light-emitting elements includes first and second recording abnormality detectors, first and second protective circuits, and abnormality signal synchronization circuits. The first and second recording abnormality detectors detect abnormalities of recording by the first and second light-emitting elements from beams reflected by the recording medium during execution of recording. The first and second protective circuits immediately stop recording being executed by the first and second light-emitting elements, and protect data on the recording medium when the first and second recording abnormality detectors detect abnormalities. The abnormality signal synchronization circuits inform the second and first protective circuits of abnormalities in synchronism with completion of recording being executed by the second and first light-emitting elements when the first and second recording abnormality detectors detect the abnormalities.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an optical disk apparatus and, more particularly, to an optical disk apparatus capable of recording data on an optical disk medium using a plurality of laser beams. 
     In a conventional optical disk apparatus, data are recorded on an optical disk medium by irradiating the optical disk medium with a beam. In this case, data are recorded on the optical disk medium using changes in shape of those portions of the optical disk medium which are heated by irradiation of the optical disk medium with a beam, the direction of magnetic fields aligned under the influence of an external magnetic field when a high temperature decreases to room temperature, and changes in crystalline state caused by the temperature difference between a high temperature and room temperature. 
     In an optical disk apparatus of this type, when the servo becomes unstable during recording/erase of data on/from an optical disk medium, the recording/erase immediately stops in order to protect user data near portions where data are to be recorded/erased. Also, when an abnormal portion is detected on an optical disk medium, recording/erase immediately stops. 
     The above optical disk apparatus is constructed by a recording head  319  and an erase head  320 , as shown in FIG.  5 . The recording head  319  is constituted by a semiconductor laser  301 , a laser driver  302 , a protective circuit  303 , a recording data generator  304 , a photodetector  305 , a medium reflection signal generator  306 , a recording abnormality detector  307 , a reproducing circuit  308 , and an abnormal sector memory  309 . 
     The erase head  320  is constituted by a semiconductor laser  310 , a laser driver  311 , a protective circuit  312 , an erase data generator  313 , a photodetector  314 , a medium reflection signal generator  315 , an erase abnormality detector  316 , a reproducing circuit  317 , and an abnormal sector memory  318 . 
     When data are simultaneously recorded and erased with a plurality of heads, they are substantially simultaneously recorded by the recording head  319  and erased by the erase head  320  at the same portion of a recording medium  321  on the same track. 
     A signal obtained from the recording data generator  304  is transmitted to the laser driver  302  via the protective circuit  303 . On the basis of the recording signal transmitted via the protective circuit  303 , the laser driver  302  records data on the recording medium  321  using the semiconductor laser  301 . 
     A signal obtained from the erase data generator  313  is transmitted to the laser driver  311  via the protective circuit  312 . On the basis of the erase signal transmitted via the protective circuit  312 , the laser driver  311  records erase data on the recording medium  321  using the semiconductor laser  310  to erase data from the recording medium  321 . 
     In recording, a signal obtained via the photodetector  305  is converted into a medium reflection signal by the medium reflection signal generator  306 . The medium reflection signal is transmitted to the recording abnormality detector  307 . The recording abnormality detector  307  detects based on the medium reflection signal whether focusing control and tracking control fall within normal ranges, and the medium is free from any defect. 
     A recording abnormality detection signal detected by the recording abnormality detector  307  is transmitted to the protective circuit  303  and the abnormal sector memory  309 , and in addition, to the protective circuit  312  and abnormal sector memory  318  of the erase head  320 . Upon reception of the recording abnormality detection signal, the protective circuit  303  immediately stops transmission of recording data to the laser driver  302 . In the abnormal sector memory  309 , a sector detected to have a recording abnormality is stored on the basis of signals obtained from the reproducing circuit  308  and the recording abnormality detector  307 . 
     In the erase head  320 , the protective circuit  312  immediately stops transmission of erase data to the laser driver  311  upon reception of the recording abnormality detection signal. In the abnormal sector memory  318 , a sector subjected to forcible stop due to the recording abnormality is stored on the basis of signals obtained from the reproducing circuit  317  and the recording abnormality detector  307 . The abnormal recording sector and the abnormal erase sector obtained from the abnormal sector memories  309  and  318  are subjected to recording and erase retries or swapping of recording data on other sectors. 
     In erase, a signal obtained via the photodetector  314  is converted into a medium reflection signal by the medium reflection signal generator  315 . The medium reflection signal is transmitted to the erase abnormality detector  316 . The recording abnormality detector  316  detects based on the medium reflection signal whether focusing control and tracking control fall within normal ranges, and the medium is free from any defect. 
     An erase abnormality detection signal detected by the erase abnormality detector  316  is transmitted to the protective circuit  312  and the abnormal sector memory  318 , and in addition, to the protective circuit  303  and abnormal sector memory  309  of the recording head  319 . Upon reception of the erase abnormality detection signal, the protective circuit  312  immediately stops transmission of erase data to the laser driver  311 . In the abnormal sector memory  318 , a sector detected to have an erase abnormality is stored on the basis of signals obtained from the reproducing circuit  317  and the erase abnormality detector  316 . 
     In the recording head  319 , the protective circuit  303  immediately stops transmission of recording data to the laser driver  302  upon reception of the erase abnormality detection signal. In the abnormal sector memory  309 , a sector subjected to forcible stop due to the erase abnormality is stored on the basis of signals obtained from the reproducing circuit  308  and the erase abnormality detector  316 . The abnormal recording sector and the abnormal erase sector obtained from the abnormal sector memories  309  and  318  are subjected to recording and erase retries or swapping of recording data on other sectors. 
     In the conventional optical disk apparatus described above, if the recording abnormality detector  307  or the erase abnormality detector  316  detects an abnormality, the other circuit (erase head  320  or recording head  319 ) is also informed of this abnormality, and erase or recording in the other circuit is forcibly stopped. 
     For this reason, a sector, which may normally undergo recording or erase, is processed as an abnormal sector by an abnormal stop signal from one head. As a result, the recording and erase times of the optical disk apparatus are prolonged. 
     The above operation will be explained on the time axis shown in FIGS. 2A to  2 D,  2 G, and  2 H. FIGS. 2A to  2 D,  2 G, and  2 H show the case wherein the recording head  319  records data on recording sectors  200  “X, X+1, X+2, . . . ”, and the recording head  320  erases data from erase sectors  203  “Y, Y+1, Y+2, . . . ”, as shown in FIG.  2 D. 
     When a recording abnormality occurs in the recording sector  200  “X+1” (FIG.  2 A), and an abnormality signal  201  (FIG. 2B) is output upon detection of the recording abnormality, an abnormal recording stop signal  202  (FIG. 2C) is input to the protective circuit  303  to stop current recording. “X+1” is stored as an abnormal recording sector in the abnormal sector memory  309 . 
     At the same time, on the erase head  320  side, the abnormal recording stop signal  202  (FIG. 2C) input to the protective circuit  312  immediately stops current erase. “Y+1” is stored as an abnormal erase sector in the abnormal sector memory  318 . As for the erase sector, no recording abnormality occurs in the sector “Y+1”, but only the abnormal recording stop signal  202  (FIG. 2C) is input from the recording head  319 . Processing for the sector “Y+1”, which may normally end, abnormally stops a time T 1  before the end, and thus “Y+1” is recorded as an abnormal sector. 
     When an erase abnormality occurs in the erase sector  203  “Y+4” (FIG.  2 D), and an abnormality signal  206  (FIG. 2G) is output upon detection of the erase abnormality, an abnormal erase stop signal  207  (FIG. 2H) is input to the protective circuit  312  to stop current erase. “Y+4” is stored as an abnormal erase sector in the abnormal sector memory  318 . 
     At the same time, on the recording head  319  side, the abnormal erase stop signal  207  (FIG. 2H) input to the protective circuit  303  immediately stops current recording. “X+4” is stored as an abnormal recording sector in the abnormal sector memory  309 . As for the recording sector, no erase abnormality occurs in the sector “X+4”, but only the abnormal erase stop signal  207  is input from the erase head. Processing for the sector “X+4”, which may normally end, abnormally stops a time T 2  before the end, and thus “X+4” is recorded as an abnormal sector. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an optical disk apparatus capable of increasing the recording and erase speeds without performing abnormal sector processing for a sector which can normally undergo processing when recording or erase urgently stops. 
     In order to achieve the above object, according to the present invention, there is provided an optical disk apparatus which has first and second light-emitting elements for emitting laser beams, and records data on a recording medium with laser beams from the first and second light-emitting elements, comprising first and second abnormality detection means for detecting abnormalities of recording by the first and second light-emitting elements from beams reflected by the recording medium during execution of recording, first and second data protective means for immediately stopping recording being executed by the first and second light-emitting elements, and protecting data on the recording medium when the first and second abnormality detection means detect abnormalities, and abnormality signal synchronization means for informing the second and first data protective means of abnormalities in synchronism with completion of recording being executed by the second and first light-emitting elements when the first and second abnormality detection means detect the abnormalities. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing the arrangement of an optical disk apparatus according to an embodiment of the present invention; 
     FIGS. 2A to  2 H are timing charts showing the processing operation when a recording abnormality and an erase abnormality occur in the optical disk apparatus shown in FIG. 1; 
     FIGS. 3A to  3 J are timing charts showing the detailed operations of respective blocks when a recording abnormality occurs in the optical disk apparatus shown in FIG. 1; 
     FIGS. 4A to  4 J are timing charts showing the detailed operations of the respective blocks when an erase abnormality occurs in the optical disk apparatus shown in FIG. 1; and 
     FIG. 5 is a block diagram showing the arrangement of a conventional optical disk apparatus. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be described in detail below with reference to the accompanying drawings. 
     FIG. 1 shows the arrangement of an optical disk apparatus according to an embodiment of the present invention. In FIG. 1, the optical disk apparatus according to an embodiment of the present invention is constituted by a recording head  119 , an erase head  120 , and abnormality signal synchronization circuits  122  and  123 . 
     The recording head  119  is constituted by a semiconductor laser  101 , a laser driver  102 , a protective circuit  103 , a recording data generator  104 , a photodetector  105 , a medium reflection signal generator  106 , a recording abnormality detector  107 , a reproducing circuit  108 , and an abnormal sector memory  109 . 
     The erase head  120  is constituted by a semiconductor laser  110 , a laser driver  111 , a protective circuit  112 , an erase data generator  113 , a photodetector  114 , a medium reflection signal generator  115 , an erase abnormality detector  116 , a reproducing circuit  117 , and an abnormal sector memory  118 . 
     When data are simultaneously recorded and erased with a plurality of heads, they are substantially simultaneously recorded by the recording head  119  and erased by the erase head  120  at the same portion of a recording medium  121  on the same track. 
     A signal obtained from the recording data generator  104  is transmitted to the laser driver  102  via the protective circuit  103 . On the basis of the recording signal transmitted via the protective circuit  103 , the laser driver  102  records data on the recording medium  121  using the semiconductor laser  101 . 
     A signal obtained from the erase data generator  113  is transmitted to the laser driver  111  via the protective circuit  112 . On the basis of the erase signal transmitted via the protective circuit  112 , the laser driver  111  records erase data on the recording medium  121  using the semiconductor laser  110  to erase data from the recording medium  121 . 
     In recording, a signal obtained via the photodetector  105  is converted into a medium reflection signal by the medium reflection signal generator  106 . The medium reflection signal is transmitted to the recording abnormality detector  107 . The recording abnormality detector  107  detects based on the medium reflection signal whether focusing control and tracking control fall within normal ranges, and the medium is free from any defect. That is, a recording abnormality is detected using the medium reflection signal used for focusing control, tracking control, and data reproduction. 
     A recording abnormality detection signal detected by the recording abnormality detector  107  is transmitted to the protective circuit  103 , the abnormal sector memory  109 , and the abnormality signal synchronization circuit  122 . Upon reception of the recording abnormality detection signal, the protective circuit  103  immediately stops transmission of recording data to the laser driver  102 . In the abnormal sector memory  109 , a sector detected to have a recording abnormality is stored on the basis of signals obtained from the reproducing circuit  108  and the recording abnormality detector  107 . 
     When a synchronized recording abnormality detection signal is transmitted from the recording head  119  to the erase head  120  via the abnormality signal synchronization circuit  122 , the protective circuit  112  immediately stops transmission of erase data to the laser driver  111 . At this time, when the recording abnormality detection signal is transmitted from the recording head  119 , the abnormality signal synchronization circuit  122  holds transmission of the synchronized recording abnormality detection signal to the protective circuit  112  on the basis of a signal from the reproducing circuit  117  of the erase head  120  until completion of current processing (erase) is detected. Upon detecting completion of the current processing, the abnormality signal synchronization circuit  122  transmits the synchronized recording abnormality detection signal to the protective circuit  112 . 
     In the abnormal sector memory  118 , a sector subjected to forcible stop due to the recording abnormality is stored on the basis of signals obtained from the reproducing circuit  117  and the abnormality signal synchronization circuit  122 . The abnormal recording sector and the abnormal erase sector obtained from the abnormal sector memories  109  and  118  are subjected to recording and erase retries or swapping of recording data on other sectors. 
     In erase, a signal obtained via the photodetector  114  is converted into a medium reflection signal by the medium reflection signal generator  115 . The medium reflection signal is transmitted to the erase abnormality detector  116 . The recording abnormality detector  116  detects based on the medium reflection signal whether focusing control and tracking control fall within normal ranges, and the medium is free from any defect. In other words, an erase abnormality is detected using the medium reflection signal used for focusing control, tracking control, and data reproduction. 
     An erase abnormality detection signal detected by the erase abnormality detector  116  is transmitted to the protective circuit  112 , the abnormal sector memory  118 , and the abnormality signal synchronization circuit  123 . Upon reception of the erase abnormality detection signal, the protective circuit  112  immediately stops transmission of erase data to the laser driver  111 . In the abnormal sector memory  118 , a sector detected to have an erase abnormality is stored on the basis of signals obtained from the reproducing circuit  117  and the erase abnormality detector  116 . 
     When a synchronized erase abnormality detection signal is transmitted to the recording head  119  from the erase head  120  via the abnormality signal synchronization circuit  123 , the protective circuit  103  immediately stops transmission of recording data to the laser driver  102 . At this time, when the erase abnormality detection signal is transmitted from the recording head  120 , the abnormality signal synchronization circuit  123  holds transmission of the synchronized erase abnormality detection signal to the protective circuit  103  on the basis of a signal from the reproducing circuit  108  of the erase head  119  until completion of current processing (recording) is detected. Upon detecting completion of the current processing, the abnormality signal synchronization circuit  123  transmits the synchronized erase abnormality detection signal to the protective circuit  103 . 
     In the abnormal sector memory  109 , a sector subjected to forcible stop due to the erase abnormality is stored on the basis of signals obtained from the reproducing circuit  108  and the abnormality signal synchronization circuit  123 . The abnormal recording sector and the abnormal erase sector obtained from the abnormal sector memories  109  and  118  are subjected to recording and erase retries or swapping of recording data on other sectors. 
     FIGS. 2A to  2 H show the processing operation when a recording abnormality and an erase abnormality occur in the optical disk apparatus shown in FIG.  1 . 
     FIGS. 2A to  2 H show the case wherein the recording head records data on recording sectors  200  “X, X+1, X+2, . . . ”, and the erase head erases data from erase sectors  203  “Y, Y+1, Y+2, . . . ”. 
     When a recording abnormality occurs in the recording sector  200  “X+1” (FIG.  2 A), and an abnormality signal  201  (FIG. 2B) is output upon detection of the recording abnormality, an abnormal recording stop signal  202  (FIG. 2C) is input to the protective circuit  103  to stop current recording. “X+1” is stored as an abnormal recording sector in the abnormal sector memory  109 . 
     When the abnormality signal synchronization circuit  122  receives the abnormal recording stop signal  202  (FIG.  2 C), it generates a synchronized abnormal recording stop signal  204  (FIG. 2E) based on a signal obtained from the reproducing circuit  117  of the erase head  120 . Based on the signal from the reproducing circuit  117 , the abnormality signal synchronization circuit  122  holds transmission of the synchronized recording abnormality detection signal  204  (FIG. 2E) to the protective circuit  112  until completion of current processing (erase) is detected. Upon detecting completion of the current processing, the synchronized recording abnormality detection signal  204  (FIG. 2E) is transmitted to the protective circuit  112 . 
     On the erase head  120  side, the synchronized abnormal recording stop signal  204  (FIG. 2E) input to the protective circuit  112  stops erase. That is, erase stops upon completion of processing for the sector “Y+1”. “Y+2” is stored as an abnormal erase sector in the abnormal sector memory  118 . The abnormal recording sector “X+1” and the abnormal erase sector “Y+2” obtained from the abnormal sector memories  109  and  118  are subjected to recording and erase retries or swapping of recording data on other sectors. 
     When an erase abnormality occurs in the erase sector  303  “Y+4”, and an abnormality signal  206  (FIG. 2G) is output upon detection of the erase abnormality, an abnormal erase stop signal  207  (FIG. 2H) is input to the protective circuit  112  to stop current erase. “Y+4” is stored as an abnormal erase sector in the abnormal sector memory  118 . 
     When the abnormality signal synchronization circuit  123  receives the abnormal erase stop signal  207  (FIG.  2 H), it generates a synchronized abnormal erase stop signal  205  (FIG. 2F) based on a signal obtained from the reproducing circuit  108  of the recording head  119 . Based on the signal from the reproducing circuit  108 , the abnormality signal synchronization circuit  123  holds transmission of the synchronized erase abnormality detection signal  205  (FIG. 2F) to the protective circuit  103  until completion of current processing (recording) is detected. Upon detecting completion of the current processing, the synchronized erase abnormality detection signal  205  (FIG. 2F) is transmitted to the protective circuit  103 . 
     On the recording head  119  side, the synchronized abnormal erase stop signal  205  (FIG. 2F) input to the protective circuit  103  stops recording. That is, recording stops upon completion of processing for the sector “X+4”. “X+5” is stored as an abnormal recording sector in the abnormal sector memory  109 . The abnormal recording sector “X+5” and the abnormal erase sector “Y+4” obtained from the abnormal sector memories  109  and  118  are subjected to recording and erase retries or swapping of recording data on other sectors. 
     Since an urgent stop signal between the recording and erase heads  119  and  120  is synchronized with the end timing of current processing for a sector, processing for the sector, which abnormally stops in a conventional apparatus, can normally end. Accordingly, the recording and erase speeds with respect to the recording medium  121  increase. 
     FIGS. 3A to  3 J show the detailed operations of the respective blocks upon occurrence of a recording abnormality. 
     In the recording head  119  during recording, the recording data generator  104  transmits recording data to the laser driver  102  via the protective circuit  103  (FIG.  3 C). When the recording abnormality detector  107  detects a recording abnormality on a recording sector (FIG.  3 A), it outputs a recording abnormality detection signal to the protective circuit  103  and the abnormality signal synchronization circuit  122  (FIG.  3 B). Immediately after receiving the recording abnormality detection signal, the protective circuit  103  stops outputting recording data from the recording data generator  104  to the laser driver  102 . Then, the laser driver  102  stops outputting recording LD emission data (FIG.  3 D), and the semiconductor laser  101  stops emitting light (FIG.  3 E). 
     Upon reception of the recording abnormality signal, the abnormality signal synchronization circuit  122  waits outputting the recording abnormality signal to the erase head  120 , and monitors completion of processing for an erase sector. When the abnormality signal synchronization circuit  122  detects completion of processing for the erase sector (FIG.  3 F), it outputs the recording abnormality signal as a synchronized recording abnormality detection signal to the protective circuit  112  of the erase head  120  (FIG.  3 G). 
     In recording, the erase data generator  113  periodically outputs erase data to the laser driver  111  via the protective circuit  112  in synchronism with the start of an erase sector (FIG.  3 H). Upon reception of the synchronized recording abnormality detection signal, the protective circuit  112  stops outputting erase data from the erase data generator  113  to the laser driver  111 . Then, the laser driver  111  stops outputting erase LD emission data (FIG.  3 I), and the semiconductor laser  110  stops emitting light (FIG.  3 J). 
     FIGS. 4A to  4 J show the detailed operations of the respective blocks upon occurrence of an erase abnormality. 
     In the erase head  120  during erase, the erase data generator  113  periodically transmits erase data to the laser driver  111  via the protective circuit  112  in synchronism with the start of an erase sector (FIG.  4 C). When the erase abnormality detector  116  detects an erase abnormality on an erase sector (FIG.  4 A), it outputs an erase abnormality detection signal to the protective circuit  112  and the abnormality signal synchronization circuit  123  (FIG.  4 B). Immediately after receiving the erase abnormality detection signal, the protective circuit  112  stops outputting erase data from the erase data generator  113  to the laser driver  111 . Then, the laser driver  111  stops outputting erase LD emission data (FIG.  4 D), and the semiconductor laser  110  stops emitting light (FIG.  4 E). 
     Upon reception of the erase abnormality signal, the abnormality signal synchronization circuit  123  waits outputting the erase abnormality signal to the recording head  119 , and monitors completion of processing for a recording sector. When the abnormality signal synchronization circuit  123  detects completion of processing for the recording sector (FIG.  4 F), it outputs the erase abnormality signal as a synchronized erase abnormality detection signal to the protective circuit  103  of the recording head  119  (FIG.  4 G). 
     In recording, the recording data generator  104  periodically outputs recording data to the laser driver  102  via the protective circuit  103  (FIG.  4 H). Upon reception of the synchronized erase abnormality detection signal, the protective circuit  103  stops outputting recording data from the recording data generator  104  to the laser driver  102 . Then, the laser driver  102  stops outputting recording LD emission data (FIG.  4 I), and the semiconductor laser  101  stops emitting light (FIG.  4 J). 
     In the above embodiment, the optical disk apparatus comprises the two abnormality signal synchronization circuits  122  and  123 , but may be constituted by one circuit. The abnormality signal synchronization circuits  122  and  123  are arranged outside the recording and erase heads  119  and  120 , but may be respectively incorporated in the erase and recording heads  120  and  119 . 
     The recording and erase abnormality detectors  107  and  116  detect recording abnormalities with medium reflection signals used for focusing control, tracking control, and data reproduction. However, recording abnormalities may be detected with a medium reflection signal used for one of them. 
     As has been described above, according to the present invention, when an abnormality is detected in the second circuit, the first head is informed of the abnormality in the second circuit in synchronism with completion of current recording, and abnormal sector processing is performed after completion of processing for a normal sector. As a result, the recording and erase speeds increase without abnormally processing a normal sector.