Abstract:
A method for recording data on an optical disk, capable of detecting an abnormal state which may occur in the middle of data recording, preventing the abnormal state from damaging the optical disk, and recording data continuously from the position wherein the abnormal state happened after the abnormal state terminates. The method of the present invention comprises the steps of (a) examining if an abnormal recording state is encountered while recording data on the optical disk, (b) suspending data recording if an abnormal recording state is detected in step (a), (c) requesting retransmission of the data received in step (a) and receiving said data after said abnormal recording state terminates, and (d) recording said retransmitted data in a selected area on the optical disk.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical information recording method and apparatus, and more particularly, but not by way of limitation, to a method for recording data on an optical disk, capable of detecting an abnormal state which may occur during data recording, preventing the abnormal state from damaging the optical disk, and recording data continuously after the abnormal state terminates. 
     2. Description of the Related Art 
     In an optical information recording/reproducing apparatus, abnormal states caused by external shocks, malfunction of the apparatus, and so forth may occur in the middle of data recording. In an abnormal state, normal data recording cannot be performed since the laser beam spot is likely to deviate beyond an error limit from the center of the track which the laser beam spot has followed. 
     Such abnormal states encountered during data recording may possibly entail critical problems. In the case of CD-R, the recordable optical disk becomes not usable, and moreover, the data recorded before the abnormal state happens may not be accessible because recording of navigation information concerning the recorded data has not been completed. In the case of a rewritable disk such as CD-RW, the data recorded before the abnormal state occurs should be rewritten, which results in a long recording time. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method for recording data on an optical disk. According to the recording method of the present invention, although an abnormal state is encountered in the middle of data recording, the optical disk medium and data recorded thereon are still available and accessible because data recording suspended by the abnormal state is completed after the abnormal state terminates. 
     A method for recording data on an optical disk in accordance with an embodiment of the present invention comprises the steps of: checking if an abnormal recording state is encountered while recording data on the optical disk; suspending data recording if an abnormal recording state is detected; requesting retransmission of the data received in the above step after the abnormal recording state terminates; and selecting a part of data being retransmitted and recording the selected data on the optical disk. 
     A method for recording data on an optical disk in accordance with another embodiment of the present invention comprises the steps of: checking if an abnormal recording state is encountered while recording data on the optical disk; suspending data recording if an abnormal recording state is detected and memorizing the position in which the abnormal recording state occurs; storing input data in a memory; continuing to store input data in said memory after the abnormal recording state terminates until said memory becomes full; moving the recording position a distance away from the memorized position and resuming input data recording on the optical disk, said distance amounting to the size of said memory; and recording the data stored in said memory in the area starting from the memorized position after said input data recording finishes. 
     In the first embodiment of the present invention, if an abnormal recording state is detected during data recording, the data recording operation is suspended until the abnormal recording state terminates. Once the abnormal recording state terminates, the data transmitted before the abnormal recording state occurred are retransmitted. The optical information recording/reproducing apparatus retrieves data recorded on the optical disk from the initial recording position and compares the retrieved data with the retransmitted data to locate the position in which the abnormal recording state occurred. If the position is detected, the data recording operation is resumed from the detected position. 
     In the second embodiment of the present invention, if an abnormal recording state is detected, the position of the optical pickup is memorized in a memory and the data transmitted after the abnormal state occurred are stored in memory means until the memory means becomes full. If the memory means becomes full, the optical pickup moves to the position a certain distance away from the memorized position and the suspended data recording operation resumes, the distance amounting to the size of the memory means. After the resumed data recording operation finishes, the optical pickup moves to the memorized position and records the data stored in the memory means on the optical disk drive, thereby completing the recording operation without any rewriting of data. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention, illustrate the preferred embodiment of this invention, and together with the description, serve to explain the principles of the present invention. 
     In the drawings: 
     FIG. 1 is a block diagram of an optical information recording/reproducing apparatus in which the invention may be practiced; 
     FIG. 2A is a detailed circuit diagram of the detrack detector shown in FIG. 1; 
     FIG. 2B is a signal diagram showing signals in some important nodes shown in FIG. 2A; 
     FIG. 3 is a flow diagram of a method according to an embodiment of the present invention; 
     FIG. 4 is a flow diagram of a method according to another embodiment of the present invention; and 
     FIGS. 5A and 5B are illustrative examples showing the data recording process when an abnormal state occurs in the middle of data recording. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In order that the invention may be fully understood, preferred embodiments thereof will now be described with reference to the accompanying drawings. 
     FIG. 1 shows a block diagram of an optical information recording/reproducing apparatus in which the present invention may be employed. 
     The optical information recording/reproducing apparatus comprises an optical pickup  2  for retrieving data recorded on an optical disk  1 , an RF unit  3  for creating a tracking error signal by collecting and converting laser beams reflected from optical disk  1  and equalizing and shaping signals reproduced from the reflected laser beams, a digital signal processing unit  4  for retrieving original digital data from the shaped signals outputted from RF unit  3 , an encoder  5  for converting the retrieved digital data into data in the format useable by a host computer and vice versa, a comparator  12  for comparing the data outputted from encoder  5  with recording data outputted from the host computer, a recording pulse generator  7  for generating recording pulses corresponding to the data outputted from encoder  5 , a detrack detector  8  for detecting detrack states utilizing the tracking error signal (T.E.) created by RF unit  3 , a servo unit  9  for controlling optical pickup  2  to perform recording or reproduction of data, an LD driver  10  for driving a laser diode, a memory  13  for temporarily storing data, and a microprocessor  11  for supervising the overall operation of the apparatus. 
     As shown in FIG. 2A, detrack detector  8  further comprises a low-pass filter  81  for only passing low-frequency components of the tracking error signal, interval detectors  82   a  and  82   b  for detecting intervals in which the level of the low-pass filtered tracking error signal is higher than a threshold level and lower than a threshold level by comparing the low-pass filtered tracking error signal with the threshold levels, monostable multivibrators  83   a  and  83   b  for extending the interval signals outputted from comparators  82   a  and  82   b  for a predetermined time duration, and an AND gate  84  for logical AND operation of the extended interval signals. 
     FIG. 3 is a flow diagram of a method for recording optical information in accordance with an embodiment of the present invention. 
     If a host computer makes a request for data recording and starts transmitting recording data, encoder  5  converts the input data transmitted by the host computer into a bit stream after reconfiguring the data in a recording format and provides the bit stream to recording pulse generator  7 . 
     Recording pulse generator  7  generates pulse signals corresponding to the bit stream after packing the bit stream into groups. In response to the pulse signals, LD driver  10  provides an electric current to a laser diode in optical pickup  2 , thereby allowing the transmitted data to be recorded sequentially on the tracks of optical disk  1  (S 01 ). 
     During the recording process, laser beams reflected from optical disk  1  are collected and converted into an electric signal by photo diodes in optical pickup  2  (S 02 ). RF unit  3  generates a tracking error signal from the electric signal by the push-pull method (S 03 ), and provides the generated tracking error signal to detrack detector  8 . Utilizing the received tracking error signal, detrack detector  8  examines if a detrack state is encountered (S 04 ). The operation of detrack detector  8  is explained below in detail with reference to FIGS. 2A and 2B. 
     The tracking error signal ({circle around (1)} in FIG. 2B) is first provided to low-pass filter  81  in detrack detector  8 , wherein high-frequency components of the tracking error signal are attenuated and so a low-pass filtered tracking error signal ({circle around (2)} in FIG. 2B) is created. The low-pass filtered tracking error signal is applied to interval detectors  82   a  and  82   b , each of which generates interval signals by comparing the low-pass filtered tracking error signal with its threshold voltage. Interval detector  82   a  generates a pulse signal while the input signal level exceeds its threshold level, whereas interval detector  82   b  generates a pulse signal while the input signal level is lower than its threshold voltage. 
     The duration of the pulse signals ({circle around (3)} and {circle around (4)} in FIG. 2B) yielded by interval detectors  82   a  and  82   b  are extended for a time duration Td ({circle around (5)} and {circle around (6)} in FIG. 2B) determined by a pair of a capacitor and a resistor. The extended-duration pulse signal from each interval detector is applied to input of AND gate  84 , wherein a level “H” signal ({circle around (7)} in FIG. 2B) is generated while both extended-duration pulse signals have the level of “H”. 
     A level “H” signal at the output of AND gate  84  indicates that there is a large fluctuation in the tracking error signal as shown in FIG.  2 B. This in turn implies that the laser beam spot deviates by external shocks from the center of the track to be followed by the laser beam spot and therefore normal recording cannot be performed. 
     If detrack detector  8  detects a detrack state by the aforementioned mechanism, microprocessor  11  controls LD driver  10  to stop emitting laser beams of a writing power (S 11 ) and makes optical pickup  2  return to its initial recording position in which data recording started (S 12 ). Completing these operations, microprocessor  11  keeps examining if the signal at the output of AND gate  8  remains low for a prescribed time duration. If it is confirmed that the detrack state by external shocks has terminated (S 13 ), microprocessor  11  sends a control signal to the host computer requesting retransmission of the recording data transmitted before the detrack state occurred (S 14 ) and starts reproduction of recorded data from the initial recording position (S 15 ). 
     The recording data retransmitted from the host computer are processed by encoder  5  as were done before and converted to data in the format usable by the recording apparatus. In this case, however, the converted data are not recorded on optical disk  1 . Rather, the signals reproduced from optical disk  1  by optical pickup  2  are converted into digital data after being processed by RF unit  3  and digital signal processing unit  4 . The retrieved digital data are converted by encoder  5  into data in the format interpretable by the host computer and provided to data comparator  12 . 
     Comparator  12  continues comparing the data outputted from encoder  5  with the data retransmitted from the host computer for each prescribed time duration, for example a time duration between sync signals (S 16 ) and examines if any data mismatch is found (Sl 7 ). 
     If a data mismatch is detected in S 17 , comparator  12  transmits a control signal indicative of the data mismatch to microprocessor  11 . In response to the indicating signal, microprocessor  11  controls encoder  5  so that the data retransmitted from the host are reconfigured in a recording format and the reformatted data are provided to recording pulse generator  7 . Finally, the data retransmitted from the host computer are recorded on optical disk  1  by LD driver  10  (S 18 ), which completes the data recording process suspended by the detrack state. 
     FIG. 4 is a flow diagram of a method for recording optical information in accordance with another embodiment of the present invention. In this embodiment, the same apparatus shown in FIG. 1 is employed and memory  13  has a designated size to temporarily store recording data transmitted by a host computer after a detrack state is detected. 
     As in the previous embodiment, detrack detector  8  continues examining if a detrack state occurs (S 21 ˜S 23 ). If a detrack state is detected (S 24 ), microprocessor  11  controls LD driver  10  to stop emitting laser beams of a writing power (S 31 ) and temporarily memorizes the current position of optical pickup  2  in an internal memory of microprocessor  11  (S 32 ). 
     Subsequently, microprocessor  11  temporarily stores the reformatted data transmitted by encoder  5  in memory  13  and keeps examining if the abnormal state comes to an end. 
     If it is confirmed that the detrack state has terminated (S 33 ), microprocessor  11  controls optical pickup  2  to move to the position a certain distance away from the position temporarily memorized in the internal memory, the distance amounting to the size of memory  13  (S 34 ). One method for this is to move the laser beam spot to the initial recording position first, then to the position memorized in the internal memory, and finally to the target position by jumping tracks corresponding to the size of memory  13 . In the case where the optical disk contains address information recorded on its entire area, the laser beam spot can be directly positioned on the target track by calculating the number of tracks to be crossed with reference to the size of memory  13  and the positions where the detrack state began and ended. 
     After positioning the laser beam on the target track, microprocessor  11  stores recording data transmitted by the host computer in memory  13  until memory  13  becomes full (S 35 ). Once memory  13  becomes full (S 36 ), microprocessor  11  resumes recording of the data transmitted by the host computer after memory  13  becomes full on optical disk  1  through recording pulse generator  7  and LD driver  10  (S 37 ). 
     When data transmission from the host computer finishes and data recording is completed (S 38 ), microprocessor  11  controls optical pickup  2  to move to the position temporarily memorized in the internal memory (S 39 ). Next, microprocessor  11  begins to read recording-formatted data stored in memory  13  and provides the data to recording pulse generator  7 , thereby recording the data temporarily stored in memory  13  in the area on optical disk  1  where the abnormal state occurred (S 40 ). 
     When the data recording method according to the present invention is applied to a rewritable recording medium like CD-RW, the whole recording data are not retransmitted as done in the embodiment shown in FIG. 3, but only the recording data to be recorded in the area where the recording process has not been completed are retransmitted. In the case, however, some part of the retransmitted data are recorded overlapping with the previously recorded data because it is almost impossible to resume the data recording exactly from the point where the shock happened. Data can be recorded on CD-RW by several methods such as disk at once, session at once, track at once, or packing writing and thus the overlapping interval depends upon which recording method is adopted. 
     FIG. 5A illustrates the data recording method according to the present invention when the session at once method is employed, where data recording on track  1  has been completed but data recording on track  2  has not been completed due to a shock occurring in the middle of recording process as shown in (a). If only the data which have not been recorded are intended to be recorded after the shock, a data gap may occur between the data recorded before and after the shock and therefore a critical error may happen when the recorded data are retrieved. To prevent this problem, data corresponding to track  2  is retransmitted and recorded from the start point of track  2  as shown in (b). Consequently, the leading data of track  2  are recorded twice, thereby improving the data recording reliability against shocks. 
     FIG. 5B illustrate the data recording method according to the present invention when the track at once method is employed, where a shock happens while recording data in packet  3 . In this case, the recording data corresponding to packet  3  are retransmitted and recorded. The leading data of packet  3  are therefore overwritten and the rest of the recording data are recorded by the normal recording process. 
     In the method for recording data on an optical disk according to the present invention, although an abnormal recording state occurs by external shocks and the laser beam spot deviates from the center of the track in the middle of data recording, the optical disk medium and data recorded thereon are still available and accessible because data recording suspended by the abnormal state is completed after the abnormal state terminates. 
     The invention may be embodied in other specific forms without departing from the sprit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.