Optical disc drive, method of moving beam spot and computer-executable program implementable by the optical disc drive

Abstract

An optical disc drive includes a light source, a lens, a focusing section, a spherical aberration corrector, a focus signal generator, a gain calculator and a processor. The focusing section forms a beam spot in a focusing state on the information storage layer of an optical disc by controlling the position of the lens. The spherical aberration corrector changes a spherical aberration with the beam spot in a focusing state according to a drive value of a driving signal supplied to the spherical aberration corrector. The focus signal generator generates a focus signal representing the focusing state of the beam spot. The gain calculator calculates a loop gain of a focus control system in response to the focus signal. The processor determines the drive value for the spherical aberration corrector by the loop gain.

1 . An optical disc drive for gaining access to a target location on an optical disc, the optical disc including multiple information storage layers, which are stacked one upon the other and each of which includes a track thereon, the optical disc drive comprising: 
 a light source for emitting a light beam toward the optical disc;    a lens for converging the light beam that has been emitted from the light source and forming a beam spot of the light beam on a selected one of the multiple information storage layers;    a beam spot controller for jumping the beam spot from a first one of the information storage layers to a second one of the information storage layers by controlling the position of the lens; and    a spherical aberration corrector for adjusting the focusing state of the beam spot by changing the spherical aberration of the lens,    wherein the spherical aberration corrector holds a first spherical aberration associated with the first information storage layer, and then corrects the first spherical aberration into a second spherical aberration, associated with the second information storage layer, after the beam spot controller has jumped the beam spot over to the second information storage layer.    
   
   
       2 . The optical disc drive of  claim 1 , wherein while the beam spot controller is jumping the beam spot over to the second information storage layer, the spherical aberration corrector provides a third spherical aberration, which is different from the first and second spherical aberrations.  
   
   
       3 . The optical disc drive of  claim 2 , wherein the third spherical aberration is associated with a focal point to be obtained by moving the beam spot in the opposite direction to that defined from the first information storage layer to the second information storage layer.  
   
   
       4 . The optical disc drive of  claim 2 , wherein the third spherical aberration is associated with a focal point that is located between the first and second information storage layers.  
   
   
       5 . The optical disc drive of  claim 3 , wherein the third spherical aberration is associated with a focal point that is located between the first and second information storage layers.  
   
   
       6 . The optical disc drive of  claim 1 , further comprising a focus detector for generating a signal representing the focusing state of the beam spot on the optical disc, 
 wherein the beam spot controller adjusts the gain of the signal that has been generated by the focus detector and then jumps the beam spot from the first information storage layer to the second information storage layer.    
   
   
       7 . The optical disc drive of  claim 2 , further comprising a focus detector for generating a signal representing the focusing state of the beam spot on the optical disc, 
 wherein the beam spot controller adjusts the gain of the signal that has been generated by the focus detector and then jumps the beam spot from the first information storage layer to the second information storage layer.    
   
   
       8 . The optical disc drive of  claim 3 , further comprising a focus detector for generating a signal representing the focusing state of the beam spot on the optical disc, 
 wherein the beam spot controller adjusts the gain of the signal that has been generated by the focus detector and then jumps the beam spot from the first information storage layer to the second information storage layer.    
   
   
       9 . The optical disc drive of  claim 1 , wherein the beam spot controller controls the position of the lens both parallelly and perpendicularly to the multiple information storage layers.  
   
   
       10 . The optical disc drive of  claim 2 , wherein the beam spot controller controls the position of the lens both parallelly and perpendicularly to the multiple information storage layers.  
   
   
       11 . The optical disc drive of  claim 3 , wherein the beam spot controller controls the position of the lens both parallelly and perpendicularly to the multiple information storage layers.  
   
   
       12 . The optical disc drive of  claim 4 , wherein the beam spot controller controls the position of the lens both parallelly and perpendicularly to the multiple information storage layers.  
   
   
       13 . The optical disc drive of  claim 5 , wherein the beam spot controller controls the position of the lens both parallelly and perpendicularly to the multiple information storage layers.  
   
   
       14 . The optical disc drive of  claim 6 , wherein the beam spot controller controls the position of the lens both parallelly and perpendicularly to the multiple information storage layers.  
   
   
       15 . The optical disc drive of  claim 7 , wherein the beam spot controller controls the position of the lens both parallelly and perpendicularly to the multiple information storage layers.  
   
   
       16 . The optical disc drive of  claim 8 , wherein the beam spot controller controls the position of the lens both parallelly and perpendicularly to the multiple information storage layers.