Laser power control technique and apparatus for recording and reproducing data in and from optical disk under laser power control

Abstract

A laser power control apparatus for controlling the output power of a semiconductor laser used to record and reproduce data in and from a recording medium is provided. The laser power control apparatus includes a controller configured to vary the peak output power level of the semiconductor laser in a stepwise manner, calculate a differential efficiency at each of the varied peak output power levels, and determine a laser driving current based on a relation between the differential efficiency and the peak output power level. In addition, a laser driving unit is configured to drive the semiconductor laser using the laser driving current determined by the controller.

1 - 4 . (canceled)  
   
   
       5 . A laser power control apparatus for controlling an output power level of a semiconductor laser used to record and reproduce data in and from a recording medium, comprising: 
 a controller configured to cause the semiconductor laser to output the laser beam with different irradiation waveforms corresponding to different recording speeds, calculate a differential efficiency for each of the recording speeds, and determine a laser driving current based on a relation between the differential efficiency and the recording speed; and    a laser driving unit configured to drive the semiconductor laser using the laser driving current determined by the controller.    
   
   
       6 . The laser power control apparatus of  claim 5 , wherein the controller is configured to derive a formula defining the differential efficiency as a function of recording speed based on the calculated differential efficiencies.  
   
   
       7 . The laser power control apparatus of  claim 6 , wherein the controller derives the formula prior to a recording operation carried out using the laser beam, and the controller is further configured to determine a laser driving current corresponding to a target recording power level and a target recording speed for the recording operation based on the formula.  
   
   
       8 . The laser power control apparatus of  claim 6 , wherein the controller derives the formula prior to test writing carried out for determining an optimum recording power level for a recording operation, and the controller is further configured to determines the laser driving current corresponding to the optimum recording power level based on the formula.  
   
   
       9 . (canceled)  
   
   
       10 . A laser power control method for controlling an output power level of a semiconductor laser used to record and reproduce data in and from a recording medium, comprising the steps of: 
 causing the semiconductor laser to output the laser beam with different irradiation waveforms corresponding to different recording speeds;    calculating a differential efficiency for each of the recording speeds;    deriving a formula defining the differential efficiency as a function of recording speed based on the calculated differential efficiencies; and    determining a laser driving current suitable for a target recording power level and a target recording speed for a recording operation based on the formula.    
   
   
       11 . (canceled)  
   
   
       12 . An apparatus for recording and reproducing data in and from a recording medium, comprising: 
 a semiconductor laser configured to emit a laser beam at two or more levels of output power;    an optical system configured to guide the laser beam onto the recording medium;    a controller configured to cause the semiconductor laser to output the laser beam with different irradiation waveforms corresponding to different recording speeds to calculate a differential efficiency for each of the recording speeds prior to a recording operation and determine a laser driving current suitable to a target recording power level based on a relation between the differential efficiency and the recording speed; and    a laser driving unit configured to drive the semiconductor laser using the laser driving current determined by the controller.    
   
   
       13 - 25 . (canceled)