Abstract:
A method and apparatus for accomplishing an OPC (optimal power calibration) at a test area secured in data recording area of a writable optical recording medium and detecting an optimal writing power appropriate to the test area, are discussed. According to an embodiment, the method searches for a marginal area adjacent to a data section recorded on an optical recording medium, records test data on the marginal area discovered in the searching step while changing a writing power; and reproduces the test data recorded on the marginal area and determining an optimal writing power based upon the characteristics of the reproduction signal.

Description:
[0001]     This application is a Continuation of co-pending application Ser. No. 10/951,770 filed on Sep. 29, 2004, which is a continuation of application Ser. No. 09/549,045 filed on Apr. 13, 2000 (now U.S. Pat. No. 6,813,107), and for which priority is claimed under 35 U.S.C. § 120; and this application claims priority of Application No. 99-12903 filed in Korea on Apr. 13, 1999, under 35 U.S.C. § 119. The entire contents of all are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method and an apparatus for detecting an optimal writing power for recording user data on a writable optical recording medium.  
         [0004]     2. Description of the Related Art  
         [0005]      FIG. 1  is a simplified block diagram of a conventional apparatus for recording data on a writable optical disk. The apparatus comprises an A/D converter  20  for digitizing an analog signal, an MPEG encoder  30  for encoding the digitized data into the MPEG format, a digital recording signal processing unit  70   a  for converting the MPEG-formatted data into recording-formatted EFM (Eight to Fifteen Modulation) data while adding additional data such as error correction codes, a channel bit encoder  80  for converting the recording-formatted data into writing signals, an optical driver  81  for yielding signals to drive a LD (laser diode), an optical pickup  11  for recording signals onto surface of a writable optical disk  10  and reproducing recorded signals from the optical disk  10 , a driving unit  90  for driving the optical pickup  11  and a motor M to move and rotate respectively, an R/F unit  100  for equalizing and shaping the signals reproduced by the pickup  11  to produce binary signals, a servo unit  110  for controlling the driving unit  90  based upon a tracking and a focusing error signal provided by the pickup  11  and the rotation speed of the optical disk  10 , a digital reproduced signal processing unit  70   b  for restoring compressed data from the binary signals using a self clock synchronized with the binary signals in phase, an MPEG decoder  120  for restoring original video and/or audio data by decoding the compressed data, and a microcomputer  60  for controlling overall operation of recording and reproduction.  
         [0006]     Upon receiving a request for recording user data, the microcomputer  60  controls the pickup  11  through the servo unit  110  and the driving unit  90  to read the indicative target writing power recorded on the writable disk medium  10 . In case where the disk  10  is a rewritable recording medium such as a CD-RW, the target writing power is recorded as 3-bit data W 1 , W 2 , and W 3  in the M 1  information byte in the field of ATIP (Absolute Time In Pre-Groove) located in the lead-in area of the optical disk  10 .  FIG. 2  shows the recording format of the bits ‘WlW 2 W 3 ’ and the meaning of each value.  
         [0007]     After reading the target writing power data W 1 , W 2 , and W 3 , that is, the indicative target writing power P ind , recorded as above, the microcomputer  60  transfers predetermined test data, for example, a byte of 10101010, to the channel bit encoder  80  through the digital recording signal processing unit  70   a.  For recording digital bit streams outputted from the digital recording signal processing unit  70   a,  the channel bit encoder  80  converts the bit streams into PWM (pulse-width-modulated) signals and applies the modulated signals to the optical driver  81 .  
         [0008]     The microcomputer  60  applies power adjusting data to the optical driver  81  and changes its value in sequence as shown in  FIG. 3  for changing the writing power within a given range with respect to the read target writing power whose intensity is assumed to 8 mW in  FIG. 3 . In response to the power adjusting data, the optical driver  81  outputs writing signals whose power corresponds to the applied power adjusting data so that the pickup  11  records the digital bit streams for testing in the test area of the optical recording medium  10 . In the case where the optical recording medium  10  is a rewritable CD such as a CD-RW, the test data are recorded in test area A of the PCA (Power Calibration Area) as shown in  FIG. 4 .  
         [0009]     Along with recording the digital bit streams for power testing, the microcomputer  60  controls the optical pickup  11  to write null data of one ATIP in the count area B located in the PCA to indicate how many times test writing is accomplished. For example, if this recording of the digital bit stream for power testing is executed thirdly for the disk  10 , the null data are written to the third ATIP of the count area B located in the PCA as shown in FIG. 4  to indicate that test operations were executed three times.  
         [0010]     On the condition that the test data have been recorded in the test area A of the PCA with the varying writing power, the microcomputer  60  controls the pickup  11  to reproduce the most recently recorded digital bit streams for power testing. While reproducing the test data, the microcomputer  60  keeps detecting the jitter magnitude of the binary signals converted from the reproduced RF (Radio Frequency) signals by the R/F unit  100 . Then, if the detected jitter magnitude is lowest, the microcomputer  60  determines the writing power used to record the test data whose jitter magnitude is lowest as an optimal writing power for the disk  10 . That is, the power Pop is chosen to optimal in  FIG. 3 .  
         [0011]     If external video and/or audio signals are received for recording after the optimal writing power Pop is determined, the received video and/or audio signals are digitized by the A/D converter  20  and encoded into the MPEG formatted data by the MPEG encoder  30 . The digital recording signal processing unit  70   a  generates digital bit streams modulated from the encoded data and error correction codes added to the encoded data by itself. The channel bit encoder  80  converts the digital bit streams into PWM signals and applies the modulated signals to the optical driver  81  to record the modulated bit streams to the disk  10 .  
         [0012]     Meanwhile, the microcomputer  60  sets the optical driver  81  to generate a driving current corresponding to the optimal writing power Pop obtained through the previous procedure. Therefore, the PWM signals whose power is optimal for the disk  10  causes the received data to be recorded in the program area of the optical disk  10 .  
         [0013]     In the above-explained conventional method for recording data on an optical disk, when a request is received for recording new data successively from the record-ending point of the program area after a previous data recording operation is done, the microcomputer  60  performs the afore-mentioned OPC (Optimal Power Calibration) again. In other words, the microcomputer  60  repeats the OPC whenever a request for recording additional data is received.  
         [0014]     However, the OPC needs to move a pickup inwardly and outwardly, that is, between PCA and program area. This takes a relatively long time to start data recording, and delays the data recording operation.  
         [0015]     Moreover, since the test area A of PCA for an optimal writing power calibration is located inwardly from a lead-in area of the program area of an optical disk where user data are to be recorded, the characteristics of recording environment of the program area may be different from that of the test area. Accordingly, sometimes an optimal writing power detected from the test area is not optimal for the recording area where user data are to be written.  
       SUMMARY OF THE INVENTION  
       [0016]     It is an object of the present invention to provide a method and an apparatus for detecting an optimal writing power, which reserves OPC areas in the user data area and detecting an optimal writing power through test writing and reading at the reserved OPC areas.  
         [0017]     The optimal writing power detecting apparatus according to the present invention comprises a writing/reading means for recording and reproducing data to/from the recording medium; a servo controlling means for moving said writing/reading means to a reserved spare area adjacent to a data section recorded in the recording medium; and a controlling means for controlling said writing/reading means to record test data in the reserved spare area while changing a writing power and to reproduce the recorded test data from the spare area, and detecting an optimal writing power based upon the characteristics of the reproduced signals.  
         [0018]     The optimal writing power detecting method according to this invention comprises the steps of searching for a marginal area adjacent to a data section recorded on an optical recording medium; recording test data on the marginal area discovered in the searching step while changing a writing power; and reproducing the test data recorded on the marginal area and determining an optimal writing power based upon the characteristics of the reproduced signal.  
         [0019]     In the present invention, the servo controlling means moves the writing/reading means to the reserved area adjacent to the data section on which user data have been most recently recorded on the optical disk, and the writing/reading means writes test data in the reserved area. While the data are being written, the controlling means controls the writing power of the writing/reading means to be changed step by step. After such writing of the test data, the test data are then reproduced by the writing/reading means and an optimal writing power is determined based upon the quality of the reproduced signals. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     The accompanying drawings, which are included to provide a further understanding of the invention, illustrate the preferred embodiments of the invention, and together with the description, serve to explain the principles of the present invention.  
         [0021]     In the drawings:  
         [0022]      FIG. 1  is a simplified block diagram of a conventional data recording/reproducing apparatus;  
         [0023]      FIG. 2  is a data example corresponding to the indicative target writing powers recorded on a rewritable optical recording medium;  
         [0024]      FIG. 3  is an illustrative graph showing the writing power being changed within a range with respect to the designated target writing power when recording test data;  
         [0025]      FIG. 4  is a view of the test area reserved in the PCA of a CD-RW for detecting an optimal writing power;  
         [0026]      FIG. 5  is a data recorded example for a writable optical recording medium reserving test areas between data tracks of the present invention;  
         [0027]      FIG. 6  is another data recorded example of a writable optical recording medium reserving test areas between data sessions of the present invention; and  
         [0028]      FIG. 7  is a flow diagram of an optimal writing power detecting method for an optical recording medium according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     In order that the invention may be fully understood, preferred embodiments thereof will now be described with reference to the accompanying drawings.  
         [0030]     The apparatus embodying the present invention is all the same as that shown in  FIG. 1  except that the microcomputer  60  according to the present invention regards the part of marginal areas such as pre-gap areas, post-gap areas, and blank areas as test areas for OPC, and searches for OPC areas based upon sync data preceding and following each test area when data recording is requested.  
         [0031]     The pre-gap and post-gap areas are reserved for every data recording track, and the blank area is reserved for every a data session in a writable optical disk.  
         [0032]     The writable optical disk according to the present invention reserves the marginal areas located adjacent to data recording sections such as tracks or sessions as well as a conventional OPC area located inner than a lead-in area as OPC areas to be used for detecting optimal writing power. The marginal area consists of sync areas for a start sync and an end sync data, a test area reserved between the sync data, and a spare area. The test area is allocated 1-2 blocks in size with the sync areas included.  
         [0033]     The codes of a start sync data and an end sync data may be different each other, for example, if 16 bits are allocated for each sync data,  0 F 0 F (16)  is for the start sync code and  0 E 0 E (16)  is for the end sync.  
         [0034]     The data section means one track if data are recorded and grouped in a track unit, and it means one session if data are recorded and grouped in a session unit.  
         [0035]     The marginal area shall be a pre-gap and a post-gap, whose size may be more than 150 blocks, before and behind a data track if data recorded are grouped in a track unit as shown in  FIG. 5 , and it shall be a blank area, whose size may be also more than 150 blocks, following a data session if data recorded are grouped in a session unit as shown in  FIG. 6 .  
         [0036]      FIG. 7  is a flow diagram of the optimal writing power detecting method embodying the present invention. Referring to  FIG. 1  assumed to have the microcomputer  60  replaced with one according to the present invention, the operation of the apparatus and the optimal writing power detecting method in accordance with the present invention will be explained in detail.  
         [0037]     When the writable optical disk  10  having no recorded data is inserted (S 01 ), the microcomputer  60  moves the optical pickup  11  to the lead-in area of the optical disk  10  through controlling the servo unit  110  and the driving unit  90  to retrieve various recording/reproduction control information recorded in the lead-in area, and temporarily stores the retrieved information in an internal memory (S 02 ).  
         [0038]     The microcomputer  60  also performs the conventional optimal power calibration (S 03 ) which records test data in the PCA area of the optical disk  10  while changing a target writing power step by step, then reproduces the recorded data while detecting an optimal writing power based upon jitter characteristics of the reproduced signals.  
         [0039]     After the optimal writing power is detected, the microcomputer  60  determines the recording format of the disk  10 . If the recording format is track unit, the microcomputer  60  controls the optical pickup  11  to skip non-recorded area through the servo unit  110  and the driving unit  90  to secure a pre-gap of more than  150  blocks. Skipping the pre-gap area, the microcomputer  60  records the inputted user data on one or more data tracks having both of a pre-gap and a post-gap (S 04 ), and when the recording is done (S 05 ), the microcomputer  60  also secures a post-gap behind the last recorded track.  
         [0040]     Meanwhile, whenever a pre-gap or a post-gap is secured, the microcomputer  60  writes sync data in front of and to the rear of a selected test zone to specify the test zone inside of the secured area.  
         [0041]     When a new recording of user data is requested (S 10 ) after the previous user data recording is finished according to above operation, the microcomputer  60  does not move the optical pickup  11  to the PCA area at this time. Instead, the microcomputer  60  controls the servo unit  110  and the driving unit  90  to move the optical pickup  11  to one of both reserved areas of a pre-gap and a post-gap preceding and following the last track on which user data were recorded. Preferably, the microcomputer  60  moves the pickup  11  to the post-gap rather than to the pre-gap, since the post-gap is nearer to a track for in which the new data are to be recorded (S 11 ).  
         [0042]     Then, the microcomputer performs the optimal power calibration within the reserved test area in the post-gap (S 12 ) through writing and reading of the optical pick  11 . Before this writing process, the microcomputer  60  searches for the start sync data recorded before the reserved test area. When the start sync data are found, the microcomputer  60  records test data in the test area. At that time, the microcomputer  60  controls the optical driver  81  to change the writing power intensity.  
         [0043]     After test data recording to the reserved test area in the post-gap is finished, the microcomputer  60  determines an optimal writing power through the checking the jitter magnitude of test signals reproduced from the reserved test area (S 13 ), and adjusts the output power of the optical driver  81  to the determined optimal writing power (S 14 ).  
         [0044]     After the optimal writing power has been set, the microcomputer  60  secures a pre-gap area first, then records the inputted user data behind the secured pre-gap using the optimal writing power (S 15 ). When the recording of the user data is completed (S 16 ), the microcomputer  60  reserves a post-gap area following the final recording location.  
         [0045]     When testing for detecting an optimal writing power is accomplished in the reserved areas located before and/or behind data sections as explained above, it is preferable to write an additional information indicating that the reserved area is used for OPC in a TOC area to announce to other disk recording/reproducing devices not to misuse data recorded in this reserved area.  
         [0046]     If inputted user data are recorded in the optical disk  10  and grouped in a session unit, the microcomputer  60  reserves a blank area behind a just-recorded session as shown  FIG. 6 . Then, before recording of new user data for a next session is started, the microcomputer  60  performs the above-explained optimal writing power detection in the reserved blank area following the recorded session.  
         [0047]     The method and apparatus for detecting an optimal writing power according to the present invention reduces a delay time, which is required to move an optical pickup inwardly and outwardly to accomplish the OPC operation, from a recording request to practical data recording. The invention also enhances writing characteristics, since an optimal writing power is obtained from a test area which is very close to the area on which input user data are recorded.  
         [0048]     Although the preferred embodiment of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as recited in the accompanying claims.