Patent ID: 11887634
Assignee: KABUSHIKI KAISHA TOSHIBA
Field: Audio-visual technology (Electrical engineering)
Classification: CPC G | IPC G

Claim 6:
7. The control method of a magnetic disk device according to claim 5, wherein
in setting of the spacing, the spacing change amount Δd is measured by utilization of a following expression (2) on a basis of primary component amplitude V01 and tertiary component amplitude V03 in a contact state of a spacing measurement pattern, primary component amplitude V11 and tertiary component amplitude V13 of a reproduction signal, a gain G01, and a gain G03,, Δ
      ⁢
      d
     
     =
     
      
       λ
       
        4
        ⁢
        π
       
      
      ⁢
      
       (
       
        
         ln
         ⁢
         
          
           
            G
            
             0
             ⁢
             1
            
           
           ⁢
           
            V
            
             1
             ⁢
             1
            
           
          
          
           
            G
            
             0
             ⁢
             3
            
           
           ⁢
           
            V
            
             1
             ⁢
             3
            
           
          
         
        
        -
        
         ln
         ⁢
         
          
           V
           
            0
            ⁢
            1
           
          
          
           V
           
            0
            ⁢
            3
           
          
         
        
       
       )
      
     
    
   
   
    
     expression
     ⁢
        
     
      (
      2
      )
     
    
   
  
 

here, λ is a wavelength of a fundamental frequency,
the gain G01=A01/A11 is defined
as the gain G01 in a case of an amplifier output A01 at the rotational speed at the time of the contact and an amplifier output A11 at the normal rotational speed of primary component amplitude in an amplifier output, and
the gain G03=A03/A13 is defined
as the gain G03 in a case of an amplifier output A03 at the rotational speed at the time of the contact and an amplifier output A13 at the normal rotational speed of tertiary component amplitude in the amplifier output.