Multilayer record carrier with shifted recording start and stop positions

Abstract

The present invention relates to a multilayer record carrier, to a recording apparatus and to a method of recording on such a multilayer record carrier, and to a manufacturing method, wherein start and stop positions of recording areas at header portions (H) are shifted, in a lower recording layer ( 8 ), by a predetermined distance (Δ) such that recording and reading in/from the lower layer ( 8 ) is not affected by a variation in the transmissivity of the upper layer ( 6 ) at the transitions between the recording areas (R) and the header portions. The shifting may be obtained by extending gap portions or adding mirror areas to the header portions (H).

1 . A multilayer record carrier comprising: 
 at least two substantially parallel and substantially aligned information layers suitable to be recorded by irradiation by a radiation beam; and    predetermined recording segments arranged in said at least two information layers, said predetermined recording segments being separated by header portions, wherein a recording area ends at a predetermined stop position at a beginning of a header portion and starts at a predetermined start position at an end of a header portion,    characterized in that    in a lower layer of said at least two information layers, said start position and said stop position are shifted, with respect to an upper layer of said at least two information layers, to a later position and to an earlier position, respectively, by a predetermined distance, and in that    said predetermined distance is selected such that an area in said upper layer, through which said radiation beam passes, has a uniform transmissivity within a beam diameter when said radiation beam is focused on the start or stop positions of said lower layer.    
   
   
       2 . The multilayer record carrier as claimed in  claim 1 , wherein in said upper layer, a gap portion is arranged between said start position and the end of said header portion, or between said stop position and the beginning of said header portion, and wherein said gap portion is extended by said predetermined distance such that a corresponding gap portion in said lower layer is extended by two times said predetermined distance.  
   
   
       3 . A multilayer record carrier comprising: 
 at least two substantially parallel and substantially aligned information layers suitable to be recorded by irradiation by a radiation beam; and    predetermined recording segments arranged in said at least two information layers, said segments being separated by header portions, wherein a recording area ends at a predetermined stop position at a beginning of a header portion and starts at a predetermined start position at an end of a header portion,    characterized in that in a lower layer of said at least two information layers, said beginning and said end of said header portions are shifted, with respect to said upper layer of said at least two information layers, by a predetermined distance to an earlier position and to a later position,    respectively, and in that    said predetermined distance is selected such that an area in said upper layer, through which said radiation beam passes, has a uniform transmissivity within a beam diameter when said radiation beam is focused on the start or stop positions of said lower layer ( 8 ).    
   
   
       4 . The multilayer record carrier as claimed in  claim 3 , wherein said shifting of the beginning and of the end of said header portions is obtained by providing a mirror area or by providing a dummy pit structure in said header portions.  
   
   
       5 . The multilayer record carrier as claimed in  claim 1 , wherein said predetermined distance is set to be greater than or equal to approximately the sum of half the diameter of said radiation beam in said upper layer when focused on said lower layer, and of a maximum allowed misalignment between said upper layer and said lower layer.  
   
   
       6 . The multilayer record carrier as claimed in  claim 1 , wherein said predetermined distance corresponds to one or to a half of a recording frame.  
   
   
       7 . A method of recording information on a multilayer record carrier irradiating the record carrier with a radiation beam, said multilayer record carrier comprising at least two substantially parallel and substantially aligned information layers, said method comprising a step of: 
 recording said information in predetermined segments of said at least two information layers, said segments being separated by header portions, and stopping said recording of said information at a predetermined stop position at the beginning of said header portions, and starting said recording at a predetermined start position at the end of said header portions, characterized in that the method also comprises the steps of:    shifting, in a lower layer of said at least two information layers with respect to an upper layer of said at least two information layers, said start position to a later position and said stop position to an earlier position by a predetermined distance; and    setting said predetermined distance such that an area in said upper layer, through which said radiation beam passes, is of a uniform transmission nature within the beam diameter when said radiation beam is focused on the start or stop positions of said lower layer.    
   
   
       8 . The method as claimed in  claim 7 , wherein said method further comprises the step of: 
 extending, in said upper layer, a gap portion arranged between said start position and the end of said header portion, or between said stop position and the beginning of said header portion, by said predetermined distance such that a corresponding gap portion in said lower layer is extended by two times said predetermined distance.    
   
   
       9 . The method as claimed in  claim 7 , wherein said predetermined distance is set to be greater than or equal to approximately the sum of half the diameter of said radiation beam in said upper layer when focused on said lower layer, and of a maximum allowed misalignment between said upper layer and said lower layer.  
   
   
       10 . The method as claimed in  claim 7 , wherein said predetermined distance corresponds to one or to a half of a recording frame.  
   
   
       11 . A method of manufacturing a multilayer record carrier comprising at least two substantially parallel and substantially aligned information layers, said method comprising the step of: 
 forming predetermined header portions in said at least two information layers, said header portions being arranged to separate recording segments,    characterized in that the method also comprises the steps of:    forming said header portions such that in a lower layer of said at least two information layers, ends of said header portions are shifted, with respect to an upper layer of said at least two information layers, to a later position, and beginnings of said header portions are shifted, with respect to said upper layer, to an earlier position, by a predetermined distance; and    setting said predetermined distance such that an area in said upper layer, through which a radiation beam used for recording or reading said record carrier passes, is of a uniform transmission nature within a beam diameter when said radiation beam is focused on start or end positions of said recording segments of said lower layer.    
   
   
       12 . The method as claimed in  claim 11 , wherein said shifting of the beginning and of the end of said header portions is obtained by providing a mirror area or by providing a dummy pit structure in said header portions.  
   
   
       13 . A recording apparatus for recording information on a multilayer record carrier, said record carrier comprising at least two substantially parallel and substantially aligned information layers, said apparatus comprising: 
 a radiation source for providing a radiation beam;    recording means for recording said information in predetermined segments of said at least two information layers by irradiating the record carrier with said radiation beam, said segments being separated by header portions; and    control means for stopping said recording of said information at a predetermined stop position at the beginning of said header portions, and starting said recording at a predetermined start position at the end of said header portions,    characterized in that    said control means shifts, in said lower layer, said start position to a later position, and shifts said stop position to an earlier position, by a predetermined distance with respect to said upper layer,    wherein said predetermined distance is set such that an area in said upper layer, through which said radiation beam passes, is of a uniform transmission nature within a beam diameter when said radiation beam is focused on the start and stop positions of said lower layer.    
   
   
       14 . The recording apparatus as claimed in  claim 13 , wherein said control means extends, in said upper layer, a gap portion arranged between said start position and the end of said header portion, or between said stop position and the beginning of said header portion, by said predetermined distance, such that a corresponding gap portion in said lower layer is extended by two times said predetermined distance.  
   
   
       15 . The multilayer record carrier as claimed in  claim 2 , wherein said predetermined distance is set to be greater than or equal to approximately the sum of half the diameter of said radiation beam in said upper layer when focused on said lower layer, and of a maximum allowed misalignment between said upper layer and said lower layer.  
   
   
       16 . The multilayer record carrier as claimed in  claim 3 , wherein said predetermined distance is set to be greater than or equal to approximately the sum of half the diameter of said radiation beam in said upper layer when focused on said lower layer, and of a maximum allowed misalignment between said upper layer and said lower layer.  
   
   
       17 . The multilayer record carrier as claimed in  claim 4 , wherein said predetermined distance is set to be greater than or equal to approximately the sum of half the diameter of said radiation beam in said upper layer when focused on said lower layer, and of a maximum allowed misalignment between said upper layer and said lower layer.  
   
   
       18 . The multilayer record carrier as claimed in  claim 2 , wherein said predetermined distance corresponds to one or to a half of a recording frame.  
   
   
       19 . The multilayer record carrier as claimed in  claim 3 , wherein said predetermined distance corresponds to one or to a half of a recording frame.  
   
   
       20 . The multilayer record carrier as claimed in  claim 4 , wherein said predetermined distance corresponds to one or to a half of a recording frame.  
   
   
       21 . The multilayer record carrier as claimed in  claim 5 , wherein said predetermined distance corresponds to one or to a half of a recording frame.  
   
   
       22 . The multilayer record carrier as claimed in  claim 15 , wherein said predetermined distance corresponds to one or to a half of a recording frame.  
   
   
       23 . The multilayer record carrier as claimed in  claim 16 , wherein said predetermined distance corresponds to one or to a half of a recording frame.  
   
   
       24 . The multilayer record carrier as claimed in  claim 17 , wherein said predetermined distance corresponds to one or to a half of a recording frame.  
   
   
       25 . The method as claimed in  claim 8 , wherein said predetermined distance is set to be greater than or equal to approximately the sum of half the diameter of said radiation beam in said upper layer when focused on said lower layer, and of a maximum allowed misalignment between said upper layer and said lower layer.  
   
   
       26 . The method as claimed in  claim 8 , wherein said predetermined distance corresponds to one or to a half of a recording frame.  
   
   
       27 . The method as claimed in  claim 9 , wherein said predetermined distance corresponds to one or to a half of a recording frame.  
   
   
       28 . The method as claimed in  claim 25 , wherein said predetermined distance corresponds to one or to a half of a recording frame.