Method and apparatus for determining an optimum power level

Abstract

A fast optimum power control method is disclosed, with a laser power level being adjusted in a predetermined sequence at an ADIP/ATIP frame of an optical recording medium. Jitter is measured at each ADIP/ATIP frame in order to obtain an average jitter value for that particular frame, and hence power level.

1 . A method of determining an optimum power level for a laser device for writing to an optical storage medium, the method comprising the acts of:
 defining a test region of the optical storage medium;   using a laser device having an operating output power level, writing a predetermined data pattern to the test region;   measuring jitter values for the predetermined data pattern; and   selecting an optimum operating output power level of the laser device for writing data to the optical storage medium depending upon the measured jitter values, the optimum power level minimizing the jitter value for the optical storage medium,   wherein, during writing of the predetermined data pattern to the test region in a first scan of the medium, the operating output power level of the laser device is varied according to a first predetermined profile, and, during writing of the predetermined data pattern to the test region in a second scan of the medium, the operating output power level of the laser device is varied according to a second predetermined profile, the predetermined write power profile of the second scan being different from the predetermined write power profile of the first scan, whereby possible problems associated with non-homogeneities of the disc along its circumference are averaged out to reduce their effects.   
   
   
       2 . The method of  claim 1 , wherein the predetermined profiles comprise a plurality of power level steps. 
   
   
       3 . The method of  claim 2 , wherein at least one jitter value is measured for each of the power level steps of the first and second predetermined profiles. 
   
   
       4 . The method of  claim 3 , wherein the step of selecting the optimum power level comprises:
 determining a function which relates jitter value to power level, over the range of power levels in the first and second predetermined profiles;   determining from said function an optimum power level that minimizes the jitter value.   
   
   
       5 . A method of determining an optimum power level for a laser device for writing to an optical storage medium, the method comprising the acts of:
 defining a test region of the optical storage medium;   using a laser device having an operating output power level, writing a predetermined data pattern to the test region;   measuring jitter values for the predetermined data pattern; and   selecting an optimum operating output power level of the laser device for writing data to the optical storage medium depending upon the measured jitter values, the optimum power level minimizing the jitter value for the optical storage medium,   wherein, during writing of the predetermined data pattern to the test region in a first scan of the medium, the operating output power level of the laser device is varied according to a first predetermined profile, and, during writing of the predetermined data pattern to the test region in a second scan of the medium, the operating output power level of the laser device is varied according to a second predetermined profile, different from the first predetermined profile,   wherein the predetermined profiles comprise a plurality of power level steps,   wherein at least one jitter value is measured for each of the power level steps of the first and second predetermined profiles,   wherein the step of selecting the optimum power level comprises: determining a function which relates jitter value to power level, over the range of power levels in the first and second predetermined profiles; and determining from said function an optimum power level that minimizes the jitter value,   wherein the step of determining the function relating jitter value to power level comprises:   for respective pairs of consecutive power levels, obtaining respective average power levels and respective average jitter values from the jitter values corresponding to those consecutive power levels; and   determining a function which relates the average jitter values to the average power levels.   
   
   
       6 . A method of determining an optimum power level for a laser device for writing to an optical storage medium, the method comprising the acts of:
 defining a test region of the optical storage medium;   using a laser device having an operating output power level, writing a predetermined data pattern to the test region;   measuring jitter values for the predetermined data pattern; and   selecting an optimum operating output power level of the laser device for writing data to the optical storage medium depending upon the measured jitter values, the optimum power level minimizing the jitter value for the optical storage medium,   wherein, during writing of the predetermined data pattern to the test region in a first scan of the medium, the operating output power level of the laser device is varied according to a first predetermined profile, and, during writing of the predetermined data pattern to the test region in a second scan of the medium, the operating output power level of the laser device is varied according to a second predetermined profile, different from the first predetermined profile,   wherein the predetermined profiles comprise a plurality of power level steps,   wherein at least one jitter value is measured for each of the power level steps of the first and second predetermined profiles,   wherein the step of selecting the optimum power level comprises: determining a function which relates jitter value to power level, over the range of power levels in the first and second predetermined profiles; and determining from said function an optimum power level that minimizes the jitter value,   wherein the step of determining the function relating jitter value to power level comprises:   for respective triads of consecutive power levels, obtaining respective average power levels and respective average jitter values from the jitter values corresponding to those consecutive power levels; and   determining a function which relates the average jitter values to the average power levels.   
   
   
       7 . A method of determining an optimum power level for a laser device for writing to an optical storage medium, the method comprising the acts of:
 defining a test region of the optical storage medium;   using a laser device having an operating output power level, writing a predetermined data pattern to the test region;   measuring jitter values for the predetermined data pattern; and   selecting an optimum operating output power level of the laser device for writing data to the optical storage medium depending upon the measured jitter values, the optimum power level minimizing the jitter value for the optical storage medium,   wherein, during writing of the predetermined data pattern to the test region in a first scan of the medium, the operating output power level of the laser device is varied according to a first predetermined profile, and, during writing of the predetermined data pattern to the test region in a second scan of the medium, the operating output power level of the laser device is varied according to a second predetermined profile, different from the first predetermined profile,   wherein the predetermined profiles comprise a plurality of power level steps,   wherein at least one jitter value is measured for each of the power level steps of the first and second predetermined profiles,   wherein the step of selecting the optimum power level comprises: determining a function which relates litter value to power level, over the range of power levels in the first and second predetermined profiles; and determining from said function an optimum power level that minimizes the litter value,   wherein the step of determining the function relating jitter value to power level comprises:   for respective pairs of consecutive power levels, obtaining respective average power levels and respective average jitter values from the jitter values corresponding to those consecutive power levels;   for respective triads of consecutive power levels, obtaining respective average power levels and respective average jitter values from the jitter values corresponding to those consecutive power levels; and   determining a function which relates the average jitter values to the average power levels.   
   
   
       8 . The method of  claim 5 , wherein the function is a quadratic function of the form σ=aP 2 +bP+C, where σ represents jitter value, P represents power level and a, b and c are constants, and the optimum power level is determined by setting the differential of the function to zero (dσ/dP=0, P optimum =−b/2a). 
   
   
       9 . The method of  claim 1 , wherein the optical storage medium is a disc having address in pre-groove frames (ADIP) defined therein, and wherein the power level is varied for each ADIP frame of the disc. 
   
   
       10 . The method of  claim 1 , wherein the optical storage medium is a disc having absolute time in pre-groove frames defined therein, and wherein the laser power level is varied for each ATIP frame of the disc. 
   
   
       11 . The method of  claim 1 , wherein the optical recording medium comprises one of CD-R, CD-RW, DVD-R, DVD-RW, DVD-R_DL, DVD-RW_DL, DVD+R, DVD+RW, DVD+R_DL, DVD+RW_DL, DVD-RAM or Blu-Ray discs. 
   
   
       12 . Apparatus for determining an optimum power level for a laser device for writing to an optical storage medium, the apparatus comprising:
 means for defining a test region of the optical storage medium;   a laser device having an operating output power level, operable to write a predetermined data pattern to the test region;   means for measuring jitter values for the predetermined data pattern; and   means selecting an optimum operating output power level of the laser device for writing data to the optical storage medium depending upon the measured jitter values, the optimum power level minimizing the jitter value for the optical storage medium,   power adjustment means operable, during writing of the predetermined data pattern to the test region in a first scan of the medium, to vary the operating output power level of the laser device according to a first predetermined profile, and, during writing of the predetermined data pattern to the test region in a second scan of the medium, to vary the operating output power level of the laser device according to a second predetermined profile, the predetermined write power profile of the second scan being different from the predetermined write power profile of the first scan, whereby any possible problems associated with non-homogeneities of the disc along its circumference are averaged out to reduce their effects.   
   
   
       13 . The apparatus as claimed in  claim 12 , wherein said means for selecting the optimum power level comprises:
 means for determining a function which relates jitter value to power level, over the range of power levels in the first and second predetermined profiles;   means for determining from said function an optimum power level that minimizes the jitter value.   
   
   
       14 . Apparatus for determining an optimum power level for a laser device for writing to an optical storage medium, the apparatus comprising:
 means for defining a test region of the optical storage medium;   a laser device having an operating output power level, operable to write a predetermined data pattern to the test region;   means for measuring jitter values for the predetermined data pattern; and   means selecting an optimum operating output power level of the laser device for writing data to the optical storage medium depending upon the measured jitter values, the optimum power level minimizing the jitter value for the optical storage medium,   power adjustment means operable, during writing of the predetermined data pattern to the test region in a first scan of the medium, to vary the operating output power level of the laser device according to a first predetermined profile, and, during writing of the predetermined data pattern to the test region in a second scan of the medium, to vary the operating output power level of the laser device according to a second predetermined profile, different from the first predetermined profile,   wherein said means for selecting the optimum power level comprises: means for determining a function which relates jitter value to power level, over the range of power levels in the first and second predetermined profiles; and means for determining from said function an optimum power level that minimizes the jitter value,   wherein said means for determining the function relating jitter value to power level comprises:   means for obtaining, for respective pairs of consecutive power levels, respective average power levels and respective average jitter values from the jitter values corresponding to those consecutive power levels; and   means for determining a function which relates the average jitter values to the average power levels.   
   
   
       15 . Apparatus for determining an optimum power level for a laser device for writing to an optical storage medium, the apparatus comprising:
 means for defining a test region of the optical storage medium;   a laser device having an operating output power level, operable to write a predetermined data pattern to the test region;   means for measuring jitter values for the predetermined data pattern; and   means selecting an optimum operating output power level of the laser device for writing data to the optical storage medium depending upon the measured jitter values, the optimum power level minimizing the jitter value for the optical storage medium,   power adjustment means operable, during writing of the predetermined data pattern to the test region in a first scan of the medium, to vary the operating output power level of the laser device according to a first predetermined profile, and, during writing of the predetermined data pattern to the test region in a second scan of the medium, to vary the operating output power level of the laser device according to a second predetermined profile, different from the first predetermined profile,   wherein said means for selecting the optimum power level comprises: means for determining a function which relates litter value to power level, over the range of power levels in the first and second predetermined profiles; and means for determining from said function an optimum power level that minimizes the jitter value,   wherein said means for determining the function relating jitter value to power level comprises:   means for obtaining, for respective triads of consecutive power levels, respective average power levels and respective average jitter values from the jitter values corresponding to those consecutive power levels; and   means for determining a function which relates the average jitter values to the average power levels.   
   
   
       16 . Apparatus for determining an optimum power level for a laser device for writing to an optical storage medium, the apparatus comprising:
 means for defining a test region of the optical storage medium;   a laser device having an operating output power level, operable to write a predetermined data pattern to the test region;   means for measuring litter values for the predetermined data pattern; and   means selecting an optimum operating output power level of the laser device for writing data to the optical storage medium depending upon the measured litter values, the optimum power level minimizing the litter value for the optical storage medium,   power adjustment means operable, during writing of the predetermined data pattern to the test region in a first scan of the medium, to vary the operating output power level of the laser device according to a first predetermined profile, and, during writing of the predetermined data pattern to the test region in a second scan of the medium, to vary the operating output power level of the laser device according to a second predetermined profile, different from the first predetermined profile   wherein said means for selecting the optimum power level comprises: means for determining a function which relates jitter value to power level, over the range of power levels in the first and second predetermined profiles; and means for determining from said function an optimum power level that minimizes the jitter value,   wherein said means for determining the function relating jitter value to power level comprises:   means for obtaining, for respective pairs of consecutive power levels, respective average power levels and respective average jitter values from the jitter values corresponding to those consecutive power levels;   means for obtaining, for respective triads of consecutive power levels, respective average power levels and respective average jitter values from the jitter values corresponding to those consecutive power levels; and   means for determining a function which relates the average jitter values to the average power levels.   
   
   
       17 . The apparatus of  claim 12 , wherein the optical storage medium is a disc having address in pre-groove frames (ADIP) defined therein, and wherein power adjustment means is operable to vary the power level for each ADIP frame of the disc. 
   
   
       18 . The apparatus of  claim 12 , wherein the optical storage medium is a disc having absolute time in pre-groove frames defined therein, and wherein power adjustment means is operable to vary the laser power level for each ATIP frame of the disc. 
   
   
       19 . The apparatus of  claim 12 , wherein the optical recording medium comprises one of CD-R, CD-RW, DVD-R, DVD-RW, DVD-R_DL, DVD-RW_DL, DVD+R, DVD+RW, DVD+R_DL, DVD+RW_DL, DVD-RAM or Blu-Ray discs. 
   
   
       20 . Recording apparatus for recording data to a disc, comprising an apparatus for determining an optimum power level, the apparatus comprising:
 means for defining a test region of the optical storage medium;   a laser device having an operating output power level, operable to write a predetermined data pattern to the test region;   means for measuring jitter values for the predetermined data pattern; and   means selecting an optimum operating output power level of the laser device for writing data to the optical storage medium depending upon the measured jitter values, the optimum power level minimizing the jitter value for the optical storage medium,   wherein power adjustment means operable, during writing of the predetermined data pattern to the test region in a first scan of the medium, to vary the operating output power level of the laser device according to a first predetermined profile, and, during writing of the predetermined data pattern to the test region in a second scan of the medium, to vary the operating output power level of the laser device according to a second predetermined profile, different from the first predetermined profile.   
   
   
       21 . The method of  claim 1 , wherein the write power level is different in write steps of the first predetermined profile than in corresponding write steps in the second predetermined profile. 
   
   
       22 . The apparatus of  claim 12 , wherein the write power level is different in write steps of the first predetermined profile than in corresponding write steps in the second predetermined profile. 
   
   
       23 . The method of  claim 21 , wherein radially adjacent ADIP/ATIP frames in concentric tracks of the data pattern are written with different power levels. 
   
   
       24 . The apparatus of  claim 22 , wherein radially adjacent ADIP/ATIP frames in concentric tracks of the data pattern are written with different power levels. 
   
   
       25 . The method of  claim 21 , wherein a maximum power level is written at a different step in the first predetermined profile than a maximum power level is written in a corresponding step in the second predetermined profile. 
   
   
       26 . The apparatus of  claim 22 , wherein a maximum power level is written at a different step in the first predetermined profile than a maximum power level is written in a corresponding step in the second predetermined profile. 
   
   
       27 . The method of  claim 1 , wherein the profiles are selected so that any variations along the circumference of the disc are averaged out. 
   
   
       28 . The apparatus of  claim 12 , wherein the profiles are selected so that any variations along the circumference of the disc are averaged out. 
   
   
       29 . The method of  claim 1  wherein the first write scan is in a different physical location on the disc then the second scan. 
   
   
       30 . The apparatus of  claim 12  wherein the apparatus is adapted to control the physical locations of the first and second scans on the disc so that the first scan in a different physical location on the disc then the second scan.