Device and method for scanning an optical recording medium and optical recording medium

Abstract

The present invention relates to a device ( 1 ) for scanning an optical recording medium ( 3 ), comprising an optical unit ( 5 ) for reading data from and/or writing data to said recording medium ( 3 ) by scanning said recording medium ( 3 ) with a radiation beam ( 21 ), said radiation beam ( 21 ) being positioned on said recording medium ( 3 ) in response to a tracking error signal, a tracking means ( 7 ) for generating said tracking error signal and a position control means ( 11 ) for controlling a radial scanning position of said radiation beam ( 21 ) in respect to a track on said recording medium ( 3 ). In order to provide a device ( 1 ) which allows a reliable tracking even in cases of asymmetric tracking conditions it is proposed that said device ( 1 ) further comprises a calibration means ( 9 ) for determining a radial offset of said tracking error signal, said radial offset being obtained by tracking a first test track ( 45 ) of a test track area ( 23 ) on said recording medium ( 3 ) having asymmetric tracking conditions, wherein the position control means ( 11 ) is adapted for controlling the radial scanning position of said radiation beam ( 21 ) in respect to a track on said recording medium ( 3 ) using said tracking error signal and said radial offset, in case of asymmetric tracking conditions. The invention further relates to a corresponding method for scanning an optical recording medium ( 3 ), a corresponding optical recording medium ( 3 ) and a corresponding computer program.

1 . A computer readable physical media containing a computer program for modifying a device for scanning an optical recording medium, the program being encoded as detectable variations in physical properties of the media, the device including:
 an optical unit for reading data from and/or writing data to said recording medium by scanning said recording medium with a radiation beam, said radiation beam being positioned on said recording medium in response to a tracking error signal,   a tracking means for generating said tracking error signal,   a position control means for controlling a radial scanning position of said radiation beam in respect to a track on said recording medium,   the program comprising:   means for modifying the device to provide a calibration means for determining a radial offset of said tracking error signal, said radial offset being obtained by tracking a first test track of a test track area on said recording medium having asymmetric tracking conditions, and   means for modifying the position control means for controlling the radial scanning position of said radiation beam in respect to a track on said recording medium using said tracking error signal and said radial offset, in case of asymmetric tracking conditions.   
   
   
       2 . The computer readable physical media according to  claim 1 ,
 wherein said program includes means for modifying the optical unit for generating said test track area.   
   
   
       3 . The computer readable physical media according to  claim 2 ,
 wherein said program includes means for modifying the optical unit for generating said test track area by writing a second test track adjacent to said first test track, said second test track comprising at least one written portion and at least one unwritten portion.   
   
   
       4 . The computer readable physical media according to  claim 3 ,
 wherein a third test track is provided adjacent to said first test track opposite to said second test track, wherein said first test track and said third test track are, preferably, at least partially empty tracks.   
   
   
       5 . The computer readable physical media according to  claim 3 ,
 wherein said second test track is surrounded by two at least partially empty tracks.   
   
   
       6 . The computer readable physical media according to  claim 3 ,
 wherein at least one of said written and/or said unwritten portions spans an angular range being smaller than a threshold time for reaction of said position control means times the angular velocity of the recording medium during operation.   
   
   
       7 . The computer readable physical media according to  claim 3 ,
 wherein said at least one written portion includes a high frequency data pattern.   
   
   
       8 . The computer readable physical media according to  claim 2 ,
 wherein said optical unit is adapted for generating said test track area in a power calibration area of said recording medium.   
   
   
       9 . The computer readable physical media according to  claim 1 ,
 wherein said tracking means is adapted to generate a three spot push pull tracking error signal and said calibration means is adapted for determining a satellite radial offset for a satellite spot and a main radial offset for a main spot individually and for determining said radial offset from said satellite radial offset and said main radial offset.   
   
   
       10 . The computer readable physical media according to  claim 1 ,
 wherein said position control means is adapted for using said radial offset being multiplied by a predetermined correction factor, said correction factor being in particular in the range of 1.0 to 1.7, preferably in the range of 1.0 to 1.5.   
   
   
       11 . The computer readable physical media according to  claim 1 ,
 further comprising
 a storing means for storing said radial offset, and 
 a retrieving means for checking whether or not a radial offset is stored for a recording medium and for retrieving said radial offset. 
   
   
   
       12 . Device for scanning according to  claim 11 ,
 further comprising
 identifying means for generating a medium identifier identifying said recording medium, and wherein said 
 storing means is adapted for storing said medium identifier together with said radial offset and said 
 retrieving means is adapted for checking using said medium identifier generated by said identifying means. 
   
   
   
       13 . The computer readable physical media according to  claim 11 , wherein said
 storing means is adapted for storing said radial offset together with a device identifier identifying said device on said recording medium and said   retrieving means is adapted for checking for the presence of an device identifier corresponding to said device on said recording medium.   
   
   
       14 . The computer readable physical media according to  claim 1 , wherein said
 calibration means is adapted for determining the sign of said radial offset from a test tracking error signal generated upon scanning said first test track, in particular from a duty cycle of said test tracking error signal.   
   
   
       15 . The computer readable physical media according to  claim 14 , wherein said
 calibration means is adapted for determining said sign by comparing said test tracking error signal to a pattern of written and unwritten portions of said test track area.   
   
   
       16 . The computer readable physical media according to  claim 15 , further comprising
 pattern storage means for storing a pattern of written and unwritten portions of said test track area and/or angular positions of written and/or unwritten portions of said test track area.   
   
   
       17 . (canceled) 
   
   
       18 . Method for scanning an optical recording medium, comprising the acts of:
 determining a radial offset for a radiation beam of an optical unit for reading data from and/or writing data to said recording medium by scanning said recording medium with said radiation beam being positioned on said recording medium in response to a tracking error signal, and   tracking of said optical recording medium using said radial offset, wherein a radial scanning position of said radiation beam in respect to a track on said recording medium is controlled using said tracking error signal and said radial offset, in case of asymmetric tracking conditions,   
     said determining including the acts of:
 tracking a first test track of a test track area on said recording medium having asymmetric tracking conditions, 
 generating said tracking error signal, and 
 determining said radial offset from said tracking error signal. 
 
   
   
       19 . A computer readable physical media containing information encoded as detectable variations of physical properties of the media, the information controlling the processor of a device for scanning an optical recording medium to program the device to perform a method comprising the acts of:
 determining a radial offset for a radiation beam of an optical unit for reading data from and/or writing data to said recording medium by scanning said recording medium with said radiation beam being positioned on said recording medium in response to a tracking error signal, and   tracking of said optical recording medium using said radial offset, wherein a radial scanning position of said radiation beam in respect to a track on said recording medium is controlled using said tracking error signal and said radial offset, in case of asymmetric tracking conditions,   said determining step including the steps of:   tracking a first test track of a test track area on said recording medium having asymmetric tracking conditions,   generating said tracking error signal, and   determining said radial offset from said tracking error signal.   
   
   
       20 . The method of  claim 18 , comprising generating said test track area. 
   
   
       21 . The method of  claim 20 , wherein generating the test track area includes writing a second test track adjacent to said first test track, said second test track comprising at least one written portion and at least one unwritten portion. 
   
   
       22 . The method of  claim 21 , wherein a third test track is provided adjacent to said first test track opposite to said second test track, wherein said first test track and said third test track are, preferably, at least partially empty tracks. 
   
   
       23 . The method of  claim 21 , wherein said second test track is surrounded by two at least partially empty tracks. 
   
   
       24 . The method of  claim 21 , wherein at least one of said written and/or said unwritten portions spans an angular range being smaller than a threshold time for reaction of said position control means times the angular velocity of the recording medium during operation. 
   
   
       25 . The method of  claim 21 , wherein said at least one written portion includes a high frequency data pattern. 
   
   
       26 . The method of  claim 20 , wherein said test track area is generated in a power calibration area of said recording medium. 
   
   
       27 . The method of  claim 18 , wherein generating the tracking error signal includes generating a three spot push pull tracking error signal and determining the radial offset includes determining a satellite radial offset for a satellite spot and a main radial offset for a main spot individually and for determining said radial offset from said satellite radial offset and said main radial offset. 
   
   
       28 . The method of  claim 18 ,
 wherein the radial scanning position is controlled depending on the radial offset multiplied by a predetermined correction factor, in the range of 1.0 to 1.7.   
   
   
       29 . The method of  claim 28 , wherein in the predetermined correction facto is in the range of 1.0 to 1.5. 
   
   
       30 . The method of  claim 18 , comprising
 storing said radial offset if it has not been stored, and   checking whether or not a radial offset is stored for a recording medium and retrieving said radial offset if it has been stored.   
   
   
       31 . The method of  claim 30 , comprising
 generating a medium identifier that identifies said recording medium   storing said medium identifier together with said radial offset if the medium identifier has not been stored   checking that the stored medium identifier matches the generated medium identifier.   
   
   
       32 . The method of  claim 30 , wherein said
 storing said radial offset together with a device identifier that identifies said device on said recording medium, and   checking for the presence of an device identifier corresponding to said device on said recording medium.   
   
   
       33 . The method of  claim 18 , comprising determining the sign of said radial offset from a test tracking error signal generated upon scanning said first test track, in particular from a duty cycle of said test tracking error signal. 
   
   
       34 . The method of  claim 33 , wherein said sign is determined by comparing said test tracking error signal to a pattern of written and unwritten portions of said test track area. 
   
   
       35 . The method of  claim 34 , comprising storing a pattern of written and unwritten portions of said test track area and/or angular positions of written and/or unwritten portions of said test track area.