Patent Publication Number: US-2006018221-A1

Title: Optical information recording apparatus capable of optimizing laser power

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an optical information recording apparatus, and more particularly to optimization of power of light when recording information on a recording medium in an optical information recording apparatus.  
      2. Description of the Background Art  
      There has conventionally been known a technique to optimize laser power for recording on an optically writable recording medium. In this technique, test recording is carried out by irradiating a prescribed portion of the recording medium, specifically a power calibration area (PCA) in the case of an optical disc, with light while changing laser power in a plurality of stages. The optimization of the laser power is performed based on quality evaluation of reproduction radio frequency (RF) signals obtained by reproducing the test-recorded information.  
      To evaluate the quality of the reproduction RF signal, a modulation factor m is normally used. The modulation factor m is a parameter that is calculated from a peak voltage A and a bottom voltage B of an envelop of the reproduction RF signal including a direct current (DC) component, in accordance with the following expression ( 1 ): 
 
 m= ( A−B )/ A.    (1) 
 
      In the optical information recording apparatus, laser power with which a desired modulation factor m (reference modulation factor) is obtained is set as the optimum laser power, which is used for actual recording (writing of information).  
      Modulation factor m, used for determination of the laser power as described above, is sometimes set as a fixed value by each manufacturer of recording media. With such a fixed value, there may arise a problem that the optimum laser power cannot be determined corresponding to the state of a recording medium where information is actually recorded.  
      From this standpoint, Japanese Patent Laying-Open No. 2003-067925 discloses a technique to determine optimum laser power, wherein modulation factors are calculated from test recording carried out with different levels of laser power, and the optimum laser power is determined based on inclination of variation of the calculated modulation factors with respect to the laser power. The technique disclosed in Japanese Patent Laying-Open No. 2003-067925, however, may pose another problem that processing is complicated.  
      Based on the foregoing, Japanese Patent Laying-Open No. 2003-303416 discloses a technique to determine optimum laser power, wherein an optical disc is configured to have an area dedicated to reproduction in which an embossed part is formed in advance, and a modulation factor obtained by reproducing the embossed part is set as a target modulation factor.  
      However, with the technique disclosed in Japanese Patent Laying-Open No. 2003-303416, it is still hard to say that the laser power can be determined corresponding to the state of a recording medium where information is actually recorded, requiring further investigation.  
     SUMMARY OF THE INVENTION  
      The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical information recording apparatus that can determine laser power corresponding to a state of a recording medium where information is actually recorded.  
      An optical information recording apparatus according to an aspect of the present invention includes: a recording unit for recording information on a recording surface of a recording medium by irradiation of light beam by a laser; a reproduction unit for reproducing information recorded on a recording medium; a determination unit for determining optimum laser power for use in the recording unit by causing the recording unit to record prescribed information on a prescribed position of a recording medium and by performing quality evaluation of a reproduction signal reproduced by the reproduction unit for the prescribed information recorded on the prescribed position; and a storage unit for storing the numbers of times of overwriting of a recording medium in association with reference values of a modulation factor that is a ratio of amplitude of an alternating current component with respect to amplitude of a direct current component in the reproduction signal reproduced by the reproduction unit. In this apparatus, the determination unit determines the optimum laser power for the recording unit by causing the reproduction unit to reproduce information of the number of times of overwriting having been recorded on a recording medium, selecting one of the reference values of the modulation factor stored in the storage unit based on the number of times of overwriting recorded on the recording medium, and by setting laser power that can achieve the selected reference value of the modulation factor to be the optimum laser power.  
      An optical information recording apparatus according to another aspect of the present invention includes: a recording unit for recording information on a recording medium in the form of a disc by irradiation of light beam by a laser; a reproduction unit for reproducing information recorded on a recording medium; a determination unit for determining optimum laser power for use in the recording unit by causing the recording unit to record prescribed information on a prescribed position of a recording medium and by performing quality evaluation of a reproduction signal reproduced by the reproduction unit for the prescribed information recorded on the prescribed position; and a storage unit for storing locations in a radial direction of target recording areas on a recording medium in association with reference values of a modulation factor that is a ratio of amplitude of an alternating current component with respect to amplitude of a direct current component in the reproduction signal reproduced by the reproduction unit. In this apparatus, the determination unit determines the optimum laser power for the recording unit by selecting one of the reference values of the modulation factor stored in the storage unit based on a location in the radial direction of a target recording area on a recording medium and by setting laser power that can achieve the selected reference value of the modulation factor to be the optimum laser power.  
      An optical information recording apparatus according to yet another aspect of the present invention is an optical information recording apparatus that irradiates a recording surface of a disc-shaped recording medium with light beam to record information on and reproduce information recorded on the recording medium. The apparatus includes: a recording unit for recording information on a recording medium by irradiation of light beam by a laser; a reproduction unit for reproducing information recorded on a recording medium; a determination unit for determining optimum laser power for use in the recording unit by causing the recording unit to record prescribed information on a prescribed position of a recording medium and by performing quality evaluation of a reproduction signal reproduced by the reproduction unit for the prescribed information recorded on the prescribed position; and a storage unit for storing locations in a radial direction of target recording areas on a recording medium, the numbers of times of overwriting of a recording medium and information about manufacturers of recording media in association with reference values of a modulation factor that is a ratio of amplitude of an alternating current component with respect to amplitude of a direct current component in the reproduction signal reproduced by the reproduction unit. In this apparatus, the determination unit determines the optimum laser power for the recording unit by selecting one of the reference values of the modulation factor stored in the storage unit based on the number of times of overwriting that is obtained by causing the reproduction unit to reproduce information of the number of times of overwriting recorded on a recording medium, a location in the radial direction of a target recording area on the recording medium and the information about the manufacturer of the recording medium, and by setting laser power that can achieve the selected reference value of the modulation factor to be the optimum laser power.  
      According to the present invention, the modulation factor used by the optical information recording apparatus for determining laser power for use in recording information on a recording medium corresponds to the number of times of overwriting of the relevant recording medium.  
      As such, the optical information recording apparatus can set the laser power for use in recording information on a recording medium to correspond to the number of times of overwriting of the relevant recording medium, i.e., to correspond to the state of the recording medium where information is actually recorded.  
      Particularly, there conventionally was a case where the modulation factor for use in determination of laser power would be saturated as the number of times of overwriting of the recording medium increased. In contrast, according to the present invention, it is possible to avoid such saturation of the modulation factor.  
      Further, according to the present invention, the modulation factor used in the optical information recording apparatus for determination of laser power for use in recording information on a disc-shaped recording medium corresponds to a location in a radial direction of a target recording area on the recording medium.  
      As such, the optical information recording apparatus can set the laser power for use in recording information on the recording medium to correspond to the location of the target recording area on the recording medium, i.e., to correspond to the state of the recording medium where information is actually recorded.  
      Still further, according to the present invention, the laser power in the optical information recording apparatus can be determined in accordance with a manufacturer of the recording medium.  
      As described above, according to the present invention, the laser power is made to correspond to the state of a recording medium where information is actually recorded. Accordingly, it is possible to surely avoid failure in writing of information on a recording medium.  
      The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a block diagram of an embodiment of the optical information recording apparatus according to the present invention.  
       FIG. 2  schematically shows by way of example how reference values of the modulation factor are stored in a flash memory of the optical information recording apparatus of  FIG. 1 .  
       FIG. 3  is a flowchart of information recording processing carried out by a CPU of the optical information recording apparatus of  FIG. 1 .  
       FIGS. 4-9  schematically show how reference values of the modulation factor are stored in the flash memory of the optical information recording apparatus of  FIG. 1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Hereinafter, an embodiment of the present invention will be explained with reference to the drawings.  
      Referring to  FIG. 1 , an optical information recording apparatus  1  of an embodiment of the present invention includes a central processing unit (CPU)  31  that controls the entire operation of optical information recording apparatus  1 . Optical information recording apparatus  1  further includes a pickup drive circuit  32 , a laser control circuit  33 , a rotation control circuit  34 , a motor  35 , a laser pickup  36 , a decode circuit  38 , a buffer memory  39 , an interface control circuit  40 , a random access memory (RAM)  41 , a flash memory  42 , and a read only memory (ROM)  43 . Optical information recording apparatus  1  is connected to an external device  44  via interface control circuit  40 .  
      When an optical disc  50  is set to optical information recording apparatus  1 , motor  35  has its rotation controlled, and a spin-up operation is started. Here, rotation control circuit  34  carries out the rotation control of motor  35 , as instructed by CPU  31 . Laser pickup  36 , driven by pickup drive circuit  32 , reads data recorded on optical disc  50 . Pickup drive circuit  32  drives laser pickup  36 , as instructed by CPU  31 .  
      The data read out of optical disc  50  is input to laser control circuit  33 , where it is converted to an electric signal. The electric signal is sent from laser control circuit  33  to buffer memory  39  for storage.  
      RAM  41  has a part serving as a disc information storage portion.  
      CPU  31  reads management information, such as table of contents (TOC) and the like, out of the disc data received at buffer memory  39 , and stores the management information in the disc information storage portion within RAM  41 .  
      In the case where reading (or reproduction) of the information recorded on optical disc  50  is further conducted by a command from external device  100  or the like, the command is input to CPU  31 . In response to the input of the command, CPU  31  instructs rotation control circuit  34  to rotate motor  35 , and further instructs pickup drive circuit  32  to drive laser pickup  36 , as in the above-described case. The data read by laser pickup  36  is temporarily stored in buffer memory  39 , and then output via decode circuit  38  and interface control circuit  40  to external device  100 .  
      CPU  31 , based on the information input from external device  100 , carries out writing and reading of information with respect to optical disc  50 , in accordance with a control program stored in ROM  43 .  
      Laser control circuit  33  controls laser irradiation by laser pickup  36 , and also controls reading of information from the reflected light of the irradiated laser light. Rotation control circuit  34  controls the operation of motor  35 .  
      In optical information recording apparatus  1 , when information is to be recorded on optical disc  50  in accordance with a command from external device  100  or the like, CPU  31  outputs an instruction to rotation control circuit  34  to rotate motor  35 , and further outputs an instruction to pickup drive circuit  32  to drive laser pickup  36 .  
      When data to be recorded on optical disc  50  is transmitted from external device  100  to optical information recording apparatus  1 , the data received is temporarily stored in buffer memory  39  before being recorded on optical disc  50 .  
      Flash memory  42  stores reference values of the modulation factor used for determination of laser power of laser pickup  36  (laser power used when laser pickup  36  records information (data) on optical disc  50 ). It is noted that the reference values of the modulation factor are stored in association with the number of times of overwriting on optical disc  50 , as schematically shown in  FIG. 2 .  
      Hereinafter, referring to  FIG. 3 , an operation of optical information recording apparatus  1  in the case of recording data received from external device  100  onto optical disc  50  will be explained, including the contents related to determination of laser power as described above.  FIG. 3  is a flowchart of the information recording processing carried out by CPU  31  in this case.  
      In the information recording processing, firstly, in step (hereinafter, “step” will not be repeated) S 1 , CPU  31  reads a reference value of modulation factor (target modulation factor) recorded on flash memory  42 , as shown in  FIG. 2 , and stores the value in RAM  41 . Specifically, in S 1 , CPU  31  refers to the number of times of overwriting of relevant optical disc  50  having been recorded on its lead-in area, and reads a target modulation factor corresponding to the relevant number of times of overwriting from flash memory  42  and stores the same in RAM  41 .  
      Next, in S 2 , CPU  31  writes the data having been transmitted from external device  100  via interface control circuit  40  and decode circuit  38 , to buffer memory  39 .  
      In S 3 , CPU  31  determines whether information of an amount corresponding to the storage capacity of buffer memory  39  has been written into buffer memory  39 . If so, CPU  31  proceeds to S 4 .  
      In S 4 , CPU  31  causes test writing to be carried out on the PCA of optical disc  50 , while causing laser power of laser pickup  36  to be changed variously.  
      In S 5 , CPU  31  searches for laser power that can achieve the target modulation factor read in S 2 , based on reproduction signals of the data having been written during the test writing in the immediately preceding step S 4 , and determines the relevant laser power as optimum laser power for use in information recording by laser pickup  36 .  
      In S 6 , CPU  31  causes the data written in buffer memory  39  to be recorded on an appropriate area of optical disc  50 . In response to success in the data recording onto optical disc  50 , the data having been written in buffer memory  39  is erased.  
      In S 7 , CPU  31  determines whether the recording of the data received from external device  100  onto optical disc  50  has been finished. If so, the information recording processing is completed. If it is determined that the recording has not yet been finished, CPU  31  returns to S 2 , receives the remaining data to be recorded on optical disc  50  successively from external device  100 , and writes the data into buffer memory  39 . That is to say, in the present embodiment, the optimum laser power of laser pickup  36  for recording data is determined every time the data of the amount corresponding to the storage capacity of buffer memory  39  is recorded on optical disc  50 .  
      In the information recording processing described above, data is recorded onto optical disc  50  with the laser power corresponding to the number of times of data overwriting on the relevant optical disc  50 .  
      It is preferable in the above-described information recording processing that the number of times of overwriting that is recorded in the lead-in area of optical disc  50  is incremented by  1  before the relevant information recording processing is finished.  
      Further, optical information recording apparatus  1  may determine the laser power for use in recording data on optical disc  50  in accordance with a location on optical disc  50  where data is to be recorded (also referred to as a “target recording area”), rather than the number of times of overwriting of optical disc  50 . Here, the location of the target recording area on optical disc  50  refers, e.g., to a distance of the target recording area from the center of optical disc  50 , which may also be referred to as a radial location of the relevant area of optical disc  50 .  
      In such a case, flash memory  42  stores target modulation factors in association with the radial locations on optical disc  50  (DISC radial locations) as shown in  FIG. 4 , instead of storing the target modulation factors in association with the numbers of times of overwriting of optical disc  50  as shown in  FIG. 2 . In the information recording processing, in S 1 , the target modulation factors are written into RAM  41  for all the DISC radial locations shown in  FIG. 4 .  
      In determination of the optimum laser power in S 5 , CPU  31  detects the radial location of the area on optical disc  50  where data is to be written (recorded) in the next step S 6 , while moving laser pickup  36  to the inner-peripheral side of optical disc  50 . CPU  31  then selects one of the target modulation factors written in RAM  41  that corresponds to the thus detected radial location, and sets the laser power that can achieve the selected target modulation factor to be the optimum laser power.  
      Alternatively, optical information recording apparatus  1  may determine the laser power for use in recording data on optical disc  50  in accordance with the manufacturer (company name or the like) of optical disc  50 , instead of the number of times of overwriting of optical disc  50 . In this case, flash memory  42  stores target modulation factors in association with the manufacturers of optical discs  50  (DISC manufacturers) as shown in  FIG. 5 , instead of storing the target modulation factors in association with the numbers of times of overwriting of optical disc  50  as shown in  FIG. 2 . It is noted that the information related to the manufacturer of optical disc  50  is recorded, e.g., in the lead-in area of each optical disc  50 .  
      Still alternatively, optical information recording apparatus  1  may determine the optimum laser power of laser pickup  36  for use in recording based on two or all of the three conditions of: the number of times of overwriting of optical disc  50 ; the radial location of the target recording area on optical disc  50 ; and the manufacturer of optical disc  50 .  
      In such a case, flash memory  42  stores target modulation factors, either as shown in  FIGS. 6-8  such that one target modulation factor can be determined uniquely based on any two of the three conditions of the number of times of overwriting of optical disc  50 , the radial location of the target recording area on optical disc  50 , and the manufacturer of optical disc  50 , or as shown in  FIG. 9  such that one target modulation factor can be determined uniquely based on all the three conditions.  
       FIG. 6  shows information stored in the case where the target modulation factor is determined based on the two conditions of the number of times of overwriting of optical disc  50  and the radial location on the disc. According to the information shown in  FIG. 6 , the target modulation factor is determined as 0.61 when the number of times of overwriting is “1” and the radial location is 24 mm.  
       FIG. 7  shows information stored in the case where the target modulation factor is determined based on the two conditions of the number of times of overwriting and the manufacturer of optical disc  50 . According to the information shown in  FIG. 7 , the target modulation factor is determined as 0.62 when the number of times of overwriting is “1” and the manufacturer is “B”.  
       FIG. 8  shows information stored in the case where the target modulation factor is determined based on the two conditions of the manufacturer of optical disc  50  and the radial location on the disc. According to the information shown in  FIG. 8 , the target modulation factor is determined as 0.69 when the manufacturer is “B” and the radial location is 40 mm.  
       FIG. 9  shows information stored in the case where the target modulation factor is determined based on the three conditions of the number of times of overwriting of optical disc  50 , its manufacturer, and the radial location on the disc. According to the information shown in  FIG. 9 , the target modulation factor is determined to be 0.72 when the number of times of overwriting is “10”, the manufacturer is “B”, and the radial location is 40 mm.  
      Although an optical recording medium in the disc form has been explained in the above-described embodiment, the present invention is not restricted thereto. The optical recording medium may be in the form of a card, except the case where the above-described radial location is concerned.  
      Further, in the embodiment described above, when the target modulation factor is to be determined in accordance with the number of times of overwriting of optical disc  50 , the number of times of overwriting may be divided into sections, and the target modulation factor may be determined for each section. For example, the number of times of overwriting may be divided into three sections of 1-10, 11-100, and 101 or more, and the target modulation factor may be set for each of the sections.  
      Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.