Optical recording medium

Abstract

In an optical recording method used when information is recorded in a phase-change recording layer of a large-capacity rewritable optical recording medium such as a DVD-RW, one block pulse is used as a recording pulse for forming one recording mark when a recording velocity is higher than a recording linear velocity at which the rewritable optical recording medium can be rewritten, whereas a pulse train comprised of a plurality of short pulses is used as the recording pulse for forming one recording pulse when the recording velocity is within recording linear velocities at which the rewritable optical recording medium can be rewritten, whereby high-velocity recording is realized.

1 . A recording/retrieving apparatus, in which a disk-shaped rewritable optical recording medium is mounted, and in a state of rotating said rewritable optical recording medium a recording beam is applied onto said rewritable optical recording medium for recording information, where said rewritable optical recording medium having a phase-change recording layer in which a crystalline state of the phase-change recording layer is used as an unrecorded/erased state and recording marks in an amorphous state with various time lengths nT (where T is a reference clock period and n is an integer not less than 2) are formed in the unrecorded/erased state;
 said recording/retrieving apparatus has three recording beam radiation modes; a rewritable recording mode, a write-once recording mode and a DC erasing mode;   (A-1) in said rewritable recording mode, recording on the rewritable optical recording medium is performed;
 rotating said rewritable optical recording medium so that a linear velocity at a radial position of said rewritable optical recording medium for recording information therein is within a range of recording velocity at which said rewritable optical recording medium can be rewritten, 
 a plurality of recording marks with the time length nT are formed; 
 dividing said time length nT into n T, α 1 T, β 1 T, α 2 T, β 2 T, . . . , α i T, β i T, . . . , α m T, β m T and η 2 T (where m is a pulse dividing number, i is an integer not less than 1 and not larger than m, Σ i (α i +β i )+η 1 +η 2 =n, α i  (1≦i≦m) is a real number larger than 0, β i  (1≦i≦m−1) is a real number larger than 0, β m  is a real number not less than 0, and η 1  and η 2  are real numbers not less than −2 and not larger than 2) in this order, where said pulse dividing number m for the time length of at least one recording mark is not less than 2, and the every time length of recording marks satisfies n/m≧1.25; 
 applying a recording beam having a recording power Pw i  (1≦i≦m) during a time period of α i T; 
 applying a recording beam having a bias power Pb i  (1≦i≦m, Pb i <Pw i , Pb i <Pw i+1 ) during a time period of β i T; 
 applying a recording beam having an erasing power Pe (Pe is a value not less than any values of m Pb i 's where 1≦i≦m, and is a value smaller than any values of m Pw i 's where 1≦i≦m) on the spaces between said plural recording marks, 
   (A-2) in said write-once recording mode, recording on said rewritable optical recording medium is performed;
 rotating said rewritable optical recording medium so that the linear velocity at a radial position of said rewritable optical recording medium for recording information therein is higher than the recording velocity range in which recorded information in said rewritable optical recording medium can be rewritten; 
 forming a recording mark with a time length nT with one block pulse in which a recording beam having a recording power PwH and a recording beam having a bias power PbH can be applied; 
   (A-3) in said DC erasing mode, recorded information in said rewritable optical recording medium is erased;
 rotating said rewritable optical recording medium so that the linear velocity at a radial position of said rewritable optical recording medium in which recorded information is to be erased is within the range of recording velocity in which said rewritable optical recording medium can be rewritten, 
 applying a recording beam having an erasing power P DC ; and 
   (A-4) when executing said write-once recording mode after executing said rewritable recording mode, or when again executing said write-once recording mode after executing said write-once recording mode,
 said DC erasing mode is executed to erase recorded information in said rewritable optical recording medium. 
   
   
   
       2 . The recording/retrieving apparatus according to  claim 1 , wherein said bias powers Pb i  and PbH are smaller than said erasing power Pe. 
   
   
       3 . The recording/retrieving apparatus according to  claim 1 , wherein said recording power Pw i  is a constant value PwL within 1≦i≦m; and
 said bias power Pb i  is a constant value PbL within 1≦i≦m.   
   
   
       4 . The recording/retrieving apparatus according to  claim 1 , wherein said erasing power P DC  in said DC erasing mode is equal to said erasing power Pe in said rewritable recording mode.