Method and apparatus for phase and/or copy window control for use with a domain expansion recording medium and record carrier

Abstract

The present invention relates to a method, apparatus and record carrier for controlling read-out and/or synchronization between an external magnetic field and written data during a reading operation from a magneto-optical recording medium comprising a storage layer and a read-out layer. An expanded domain leading to a pulse in a reading signal is generated in said read-out layer by copying a mark region from said storage layer to said read-out layer upon heating by a radiation power and with the help of the external magnetic field. The waveform of the reading signal is analyzed, and the analyzing result is used for correcting a phase deviation and/or for controlling a copy window size of the mark copying. Thereby, phase errors can be corrected for any size of the copy window. Even small changes in the copy window can be detected and corrected.

1 . A method of controlling synchronization between an external magnetic field and data written on a magneto-optical recording medium ( 10 ), said recording medium comprising a storage layer and a read-out layer, wherein an expanded domain leading to a pulse in a reading signal is generated in said read-out layer by copying a mark region from said storage layer to said read-out layer upon heating by a radiation power and with the aid of said external magnetic field, said method comprising
 an analyzing step for analyzing the waveform of said reading signal, and   a correction step for correcting, on the basis of the result of said analyzing step, a phase deviation between said external magnetic field and said written data.   
   
   
       2 . A method according to  claim 1 , wherein said correction step is performed by shifting the timing of said external magnetic field. 
   
   
       3 . A method according to  claim 1  or  2 , wherein said correction step is based on at least one predetermined correction rule which depends on a write strategy used and/or a read strategy used. 
   
   
       4 . A method according to  claim 4 , also comprising the step of using said at lest one correction rule for an additional copy window correction. 
   
   
       5 . A method according to  claim 3  or  4 , wherein said at least one correction rule defines a correction amount and direction. 
   
   
       6 . A method of controlling read-out from a magneto-optical recording medium ( 10 ), said recording medium comprising a storage layer and a read-out layer, wherein an expanded domain leading to a pulse in a reading signal is generated in said read-out layer by copying a mark region from said storage layer to said read-out layer upon heating by a radiation power and with the aid of an external magnetic field, said method comprising
 an analysis step for analyzing the waveform of said reading signal, and   a controlling step for controlling a copy window size of said mark copying on the basis of the result of said analyzing step.   
   
   
       7 . A method according to  claim 6 , wherein said controlling step is performed by controlling said radiation power and/or the strength of said external magnetic field. 
   
   
       8 . A method according to  claim 6  or  7 , wherein synchronization phase errors between the external magnetic field, used for said mark copying, and written data are determined and used in said analyzing step. 
   
   
       9 . A method according to any one of the  claims 6  to  8 , wherein said analyzing step is applied to a reading signal obtained by reading a test area provided on said recording medium ( 10 ). 
   
   
       10 . A method according to any one of the  claims 6  to  8 , wherein said analyzing step is applied to a reading signal obtained by reading written user data. 
   
   
       11 . A method according to any one of the preceding claims, wherein said analyzing step comprises comparison of the timing of the rising edge of a predetermined pulse of said reading signal with a reference value. 
   
   
       12 . A method according to any one of the preceding claims, wherein said analyzing step comprises comparison of the duration of a predetermined pulse of said reading signal with a reference value. 
   
   
       13 . A method according to  claim 11  or  12 , wherein said predetermined pulse is the first pulse of a code run-length. 
   
   
       14 . A method according to  claim 12 , wherein said duration is determined by detecting the pulse amplitude of said predetermined pulse after a filter operation. 
   
   
       15 . A method according to any one of the preceding claims, wherein said analyzing step is performed by using information from a look-up table ( 23 ). 
   
   
       16 . A method according to  claim 15 , wherein said look-up table ( 23 ) is updated on the basis of information read from said recording medium ( 10 ). 
   
   
       17 . A method according to  claim 15 , wherein said information defines a relation between said waveform and at least one of a phase error and a copy window size. 
   
   
       18 . A method according to any one of the  claims 15  to  17 , wherein said look-up table is provided by a control program of a driver function used for generating said external magnetic field. 
   
   
       19 . A method according to any one of the preceding claims, also comprising the step of storing on said recording medium ( 10 ) strategy information defining a write strategy of said recording medium ( 10 ), and using said strategy information in said analyzing step. 
   
   
       20 . A method according to  claim 19 , wherein said strategy information is used for generating a reference waveform used in said analyzing step. 
   
   
       21 . A reading apparatus for controlling synchronization between an external magnetic field and data written on a magneto-optical recording medium ( 10 ), said recording medium comprising a storage layer and a read-out layer, wherein an expanded domain leading to a pulse in a reading signal is generated in said read-out layer by copying a mark region from said storage layer to said read-out layer upon heating by said radiation power and with the aid of said external magnetic field, said apparatus comprising:
 analyzing means ( 21 - 23 ) for analyzing the waveform of said reading signal, and   correction means ( 25 ) for correcting a phase deviation between said external magnetic field and said written data on the basis of the result of said analyzing step.   
   
   
       22 . A reading apparatus for controlling read-out from a magneto-optical recording medium ( 10 ), said recording medium comprising a storage layer and a read-out layer, wherein an expanded domain leading to a pulse in a reading signal is generated in said read-out layer by copying a mark region from said storage layer to said read-out layer upon heating by a radiation power and with the aid of an external magnetic field, said apparatus comprising:
 analyzing means ( 21 - 23 ) for analyzing the waveform of said reading signal; and   control means ( 25 ) for controlling a copy window size of said mark copying on the basis of the result of said analyzing step.   
   
   
       23 . A reading apparatus according to  claim 21  or  22 , wherein said analyzing means ( 21 - 23 ) comprises storing means ( 23 ) for storing information defining a relation between said waveform and at least one of a phase error and a copy window size. 
   
   
       24 . A reading apparatus according to  claim 23 , wherein said analyzing means ( 21 - 23 ) comprises comparing means ( 22 ) for comparing said analyzed waveform on the basis of said relation stored in said storing means ( 23 ). 
   
   
       25 . An apparatus according to any one of the  claims 21  to  24 , wherein said reading apparatus is a disk player for MAMMOS disks. 
   
   
       26 . A magneto-optical record carrier comprising a storage layer and a read-out layer, wherein an expanded domain leading to a pulse in a reading signal is generated in said read-out layer by copying a mark region from said storage layer to said read-out layer upon radiation heating and with the aid of an external magnetic field, said record carrier ( 10 ) comprising pre-recorded control information defining a relation between a waveform of said reading signal and at least one of a phase error and a copy window size. 
   
   
       27 . A record carrier according to  claim 26 , wherein said control information comprises a strategy information defining a write strategy of said record carrier ( 10 ). 
   
   
       28 . A record carrier according to  claim 26  or  27 , wherein said record carrier is a MAMMOS disk ( 10 ).