Abstract:
A method of improving a problem of a deviation of an optimum recording optical power, which is capable of reducing deviation of OPC (Optical Power Calibration) power and shortening a Lead-in time by previously setting an area in which an OPC operation may be conducted and erasing the area with an erase power.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of Korean Application No. 2005-20935, filed Mar. 14, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     An aspect of the present invention relates to an optical recording device, and, more particularly to a technique capable of reducing a deviation of an Optimum Power Calibration (Optimum Power Calibration) operation and of improving speed.  
         [0004]     2. Description of the Related Art  
         [0005]     In an optical recording/reproducing device, using an irradiated beam with accurate power to record information on an optical recording medium is important. Due to environments of combinations of all recording media and recording devices and also deviation between devices, such an accurate power may not be provided substantially all the time (e.g., by recording on a disk in advance).  
         [0006]     Thus, in order to find out an optimum optical power for a recording operation, an optical recording/reproducing device generally conducts an OPC (Optimum Power Calibration) operation in a test area of the optical disk inserted therein to detect an optimum optical power (Popt), and uses the detected optimum recording optical power in a recording operation.  
         [0007]     The test area is particularly reserved for recording test patterns. Such a reserved area is, for example, known as a Disk Test Zone or an OPC Test Zone. Such a test area may be configured as one successive region or as a plurality of sub regions.  
         [0008]     That is to say, an optical disk drive system controls a laser power (or, recording power) level required to record data on a corresponding optical disk through a Power Calibration Area (PCA), when conducting a recording mode for a once recordable optical disk such as CD-R and DVD-R. This is called Optimum Power Control (OPC).  
         [0009]     However, though an optimum recording power is obtained via an OPC operation, if an environment for recording is changed by the time an actual recording operation is conducted, producing an accurate recording characteristic may be impossible. For example, the optimum recording power determined by an OPC operation may be changed, and, thus, a Beta (or, an asymmetry) of recorded signals may also be changed to produce inaccurate recording characteristics. This could occur in the following exemplary cases: where a power sensitivity is generated at each position on the optical disk, where a wavelength of LD is shifted due to high temperatures, and a deviation is generated on beam spot due to a disk skew phenomenon, varying thicknesses of disks or a resulting defocus of the beam spot on the disks, and/or where disk and/or optical conditions are changed due to a fact that an actual recording may not be conducted until a long time after the OPC.  
         [0010]     In order to solve these problems, there has been proposed a method for β compensation by repeatedly recording and measuring test data while changing a recording optical power little by little.  
         [0011]     Hereinafter, the recording optical power compensation method of the related art as discussed above is described with reference to  FIG. 1 .  
         [0012]     As shown in  FIG. 1 , an optical disk is inserted into the apparatus, a recording operation is requested ( 21 ), and an OPC operation is conducted in the Power Calibration Area (PCA) of the optical disk before the recording operation to determine an optimum recording power ( 22 ). That is to say, an optimum optical power corresponding to an optimum beta value given to each MID is detected.  
         [0013]     According to the related art, generally, a test recording is made in a certain area of the optical disk using the optimum recording power detected by the OPC. Then, a Radio Frequency (RF) level of the recording signal in the area is measured to set a target beta.  
         [0014]     The detected recording power is recorded as a user data of the disk ( 24 ). Then, whether a recording medium is a DVD-R ( 26 ) is determined. If the recording medium is determined to be a DVD-R (or a CD-R, where appropriate) in operation  26 , a beta β compensation operation is conducted.  
         [0015]     In order to conduct the β compensation operation, a mode is switched to a read mode, namely a loader is switched into a standby mode ( 30 ), and a finally recorded area is found ( 31 ).  
         [0016]     Based on the RF level measured at the recorded area in operation  31 , a beta β value is calculated through an OPC operation ( 32 ). At this time, the RF level is calculated by measuring Top/Center/Bottom levels.  
         [0017]     In a common OPC (Optical Power Calibration) operation, a controller of the system applies a control signal to an optical drive and simultaneously varies a recording optical power little-by-little based on a target recording optical power (e.g., 8 mW) that is detected from the optical disk. Meanwhile, the optical drive outputs a recording signal for test data with an optical power corresponding to the applied control signal, and an optical pickup records a certain amount of test data in a test area of the PCA.  
         [0018]     If the test data is completely recorded, the system controller controls the optical pickup to read out the read test data in order, and then detects a β value from a regenerated RF signal that is output from an R/F unit.  
         [0019]     In addition, the system controller checks on how many measurements of the detected β value have been conducted (which is set to 5 times in the example of  FIG. 1 ) ( 33 ), stores the measured β value in an internal memory if the measurements have been conducted less than 5 times ( 40 ), and calculates an average of the measured β values if the measurements have been conducted over 5 times ( 34 ).  
         [0020]     The average value calculated in operation  34  is compared with the β value (or, the target β value) of the optical disk that is detected in operation  22  ( 35 ). If an absolute value of the difference between the measured β value and the target β value is found to be greater than a predetermined level (or, an allowable range: a), the recording power is decreased as much as 0.1 mW ( 39 ). In contrast, if the absolute value of the difference between the measured β value and the target β value is less than a predetermined level, the recording power is increased as much as 0.1 mW ( 37 ). Then, the β compensation operation is completed ( 38 ).  
         [0021]     If the recording medium is found to not be a DVD-R in operation  26  or after the β compensation operation is conducted, the loader progresses in a standby state until the next recording ( 28 ) operation, and then the process is ended ( 29 ). Otherwise, the process proceeds to operation  24  to record data in a user data area of the disk with the optimum optical power detected in the above operation.  
         [0022]     However, a problem exists in that the detected optimum optical power may generate a jitter due to a serious deviation of the recording optical power (commonly, not smaller than 0.4 mV) after a full DC erasing for the recording optical power the reserved PCA found first by an OPC operation in a non-recorded area of a new disk. Thus, the OPC operation may not be applicable to a Blu-ray set.  
         [0023]     In addition, the Blu-ray set requires a relatively large amount of time to search an area that is required for an OPC operation in comparison to a common optical disk.  
         [0024]     That is to say, referring to  FIG. 2 , if a Blu-ray disk is inserted and a recording operation is requested ( 50 ), the system controller searches a Bland area for an OPC operation in an OPC test zone of the Blu-ray disk (hereinafter, referred to as a Physical ADIP (Address in Pre-groove) Address (PAA) area) ( 52 ), before the recording operation. In addition, if a blank area is not found, all of the PAA area is erased using an erase DC power ( 54 ) operation.  
         [0025]     Thereafter, user data is recorded in the PAA area through a power swing operation and an optimum recording optical power is detected by measurement and a Kappa Curve ( 56 ). Then, a recording signal is recorded via an optical driving current corresponding to the optimum recording optical power ( 58 ).  
         [0026]     A common Blu-ray set requires  5  seconds on an average to conduct operation  52  in the above procedure, and about  30  seconds to execute operation s 54 .  
         [0027]     Thus, since at least 5 seconds and up to 35 seconds are required to set the PAA area, an entire recording time may be reduced by decreasing the area searching time.  
       SUMMARY OF THE INVENTION  
       [0028]     The present invention is designed to solve the above and/or other problems of the related art, and, therefore, an aspect of the present invention provides a method and apparatus capable of reducing a deviation of an optimum recording optical power in a Blu-ray disk and of reducing a recording time.  
         [0029]     In order to accomplish the above and/or other aspects of the invention, the present invention provides a method of setting an optimum recording optical power of a recording medium, which includes setting a test data recording area for measuring the optimum recording optical power of the recording medium; recording the test data after erasing the set recording area with erase power; and detecting the recorded data and then setting the optimal recording optical power.  
         [0030]     Preferably, the test data recording area is set using target address and length to which the test data is to be recorded, and the length is set to 5 tracks.  
         [0031]     The test data may be recorded in front of a middle tract of the set recording area so as to decrease crosstalk.  
         [0032]     The recording medium may be an optical disk, a Blu-ray disk, or a similar type of disk.  
         [0033]     In addition, the setting of the test data recording area preferably includes reading finally recorded address and length; generating a new address by adding the length to the read address; and generating a new length by allocating a predetermined track to the new address.  
         [0034]     The finally recorded address and length may be stored in and then read from a non-volatile memory or a user data area of the recording medium.  
         [0035]     In addition, the method of setting an optimum recording optical power according to the present invention may further include recording data in the recording medium with the set optimum recording optical power so that data may be recorded using the optimum recording optical power.  
         [0036]     In another aspect of the invention, there is also provided an apparatus for setting an optimum recording optical power of a recording medium, which includes an optical drive for outputting an intensity drive signal according to an input signal; an optical pickup for recording signals in the recording medium according to the intensity drive signal of the optical drive and also detecting a recording signal from a recording surface; and a controller for setting an area on which a test data for measuring the optimum recording optical power of the recording medium is to be recorded, controlling the optical drive to record the test data in the set recording area after erasing the set recording area with erase power, and detecting the recorded data to set the optimum recording optical power.  
         [0037]     Preferably, the test data recording area is set using target address and length to which the test data is to be recorded, and the length is set to 5 tracks, and the test data is recorded in front of a middle tract of the set recording area.  
         [0038]     In addition, the recording medium may be an optical disk.  
         [0039]     The controller generates a new address by reading finally recorded address and length and then adding the length to the read address, and at the same time sets the test data recording area by generating a new length by allocating a predetermined track to the new address.  
         [0040]     In addition, the finally recorded address and length are preferably stored in a non-volatile memory or a user data area of the recording medium.  
         [0041]     Additional and/or other aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0042]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0043]      FIG. 1  is a flowchart illustrating a conventional recording optical power compensation method;  
         [0044]      FIG. 2  is a flowchart illustrating an OPC test zone searching process of a conventional Blu-ray set;  
         [0045]      FIG. 3  shows an optical disk device to which an improved method for reducing deviation and recording time according to an embodiment of the present invention is applied; and  
         [0046]      FIG. 4  is a flowchart illustrating an OPC test zone of a Blu-ray set of according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0047]     Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.  
         [0048]      FIG. 3  shows an optical disk device to which an improved method to reduce a deviation of an OPC operation and a recording time, according to an embodiment of the present invention, is applied. As shown in  FIG. 3 , the optical disk device  100  includes a digital recording signal processor (DSP RECORD)  150 a to add an error correction code (ECC) to input digital data so as to convert the input digital data into a recording format, a channel bit encoder  160  to re-convert the data that is converted into the recording format into a bit stream, an optical drive  170  to output an intensity drive signal according to an input signal, an optical pickup  190  to record signals on an optical disk  110  according to the intensity drive signal and to detect a recording signal from a recording surface, an R/F unit  180  to filter and shape the signal detected by the optical pickup  190  to output the signal as a binary code, a drive unit  120  to drive a spindle motor M that rotates the optical pickup  190  and the optical disk  110 , a servo unit  130  to receive a tracking error signal (TE) and a focus error signal (FE) of the optical pickup  190  and a rotating speed of the optical disk  110  and to control an operation of the drive unit  120 , and a digital regenerated signal processor (DSP REGENERATE)  150   b  to restore the binary signal into an original data with its own clock synchronized to the binary signal output from the R/F unit  180 .  
         [0049]     A controller  140  optimally controls a recording optical power via a β value detected from a regenerated RF signal of recorded data and a power increase level that is set for each recording speed in consideration of the characteristic changes of the inserted optical disk  110  or the optical pickup  190  during the recording operation. The controller  140  calculates the β value by measuring Top/Bottom levels of the RF level in the recording area using commonly understood methods.  
         [0050]     In addition, the controller  140  includes a memory  142  that stores a Physical ADIP Addresses (PAA) area and lengths of data finally recorded in the PAA area. Thus, if the optical disk is inserted and a recording operation is requested, the controller  140  reads the PAAs and lengths that are stored in the memory  142 , selects a target PAA and length, and then controls the optical drive  170  to unconditionally erase the selected PAA and length using an Erasing Power.  
         [0051]     Though the controller  140  has been described as including the internal memory  142 , a use of a non-volatile memory such as NVRAM is also possible.  
         [0052]     Hereinafter, a process of searching an OPC test zone in a Blu-ray disc, according to an embodiment of the present invention, is described with reference to  FIG. 4 . As shown in  FIG. 4 , if an optical disk is inserted and a recording operation is requested ( 210 ), the controller  140  reads the last recorded area stored in the memory  142  so as to prepare to conduct a new OPC operation ( 220 ). That is to say, in operation  220 , the controller  140  reads a PAA area and a length of an area that is stored in the memory  142  at which the last OPC operation was carried out.  
         [0053]     The controller  140  then designates a new PAA area and length, in which a new OPC operation is conducted, in contrast to the PAA area and length read in operation  220  ( 230 ). Generally, the length is set to 5 tracks, and a test data record to actually execute the OPC operation is, according to an embodiment of the invention, recorded in a front of a middle tract of the set length in order to decrease crosstalk that may occur.  
         [0054]     Thereafter, the controller  140  unconditionally erases the area required to conduct the OPC operation by using an erase power with reference to the set PAA area and length ( 240 ). That is to say, the controller  140  operates the optical drive  170  regardless of the fact that the corresponding area may have been used in a recording operation or not. As a result, the optical pickup  190  forcibly erases the corresponding area once. According to the test results, an OPC recording deviation of the same set or the same disks is less than 0.1%, and a recording power was measured in the range of ±5%. Thus, the OPC operation discussed above may be applicable for the Blu-ray set.  
         [0055]     In addition, about 0.5 seconds are taken to forcibly erase the corresponding area. Thus, while the OPC area is set in about 0.5 seconds, the conventional methods required 5 to 35 seconds since approximately 5 seconds were required to search a Bland APP area and approximately 30 seconds were required to forcibly erase all of the PAA areas when there was no Blank PAA area. Thus, the present invention enables a reduction in operating time by at least 4.5 seconds and up to 34.5 seconds.  
         [0056]     Test data is recorded in the erased PM area through a power swing and then an optimum recording optical power is detected using measurement and an application of a Kappa Curve ( 250 ). Then, a recording signal is recorded using an optical drive power corresponding to the detected optimum recording optical power ( 260 ). Operations  250  and  260  are executed to record test data and to search an optimum recording optical power as in the conventional method. As such these operations are not described in detail here.  
         [0057]     In addition, though the finally recorded PM area was described as being stored in a memory, it is also possible that the finally recorded PM is recorded in a user area of the disk and that the relevant data is read in the user area before conducting the OPC operation. Thus, where the data is stored in a non-volatile memory, the data may not be used in another disk device. However, if the data is recorded in the user area as in the above, the data may be used though a disk device is changed, effectively. The controller  140  previously sets target PM area and length and erases data once with an erase power and then records the test data so as to measure an optimum optical power. Since, the process of recording the target PM area and length is well known in the art the process is not described in detail here.  
         [0058]     As is mentioned above, the controller  140  previously sets a PM area to conduct an OPC operation and then erases the area with an erase power in the process of searching for an optimum recording optical power, which may shorten time and reduce power deviation since the same processor is applied.  
         [0059]     According to the method and apparatus to improve deviation of an optimum recording optical power of the present invention, an OPC recording power deviation may be improved and then applied to a Blu-ray set, and a Lead-in time may be reduced by at least 4.5 seconds up to 34.5 seconds, which allows faster recording operation.  
         [0060]     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.