Optical pickup apparatus employing a grating and a hologram that generate multiple beams detected by a photodetector

Abstract

An optical pickup apparatus is characterized in that the optical pickup comprises a light emission part 60 for emitting first and second laser beams having different wavelengths from each other, a grating 62 for generating a pair of sub-beams from the laser beam emitted from the light emission part, and a hologram 63 for generating plus and minus high-order beams from the laser beam reflected by a recording medium to guide the high-order beams to a light receiving part, and the light receiving part comprises a pair of three-division light receiving elements for receiving the plus and minus high-order beam generated from the first or second laser beam reflected by the recording medium, respectively, to generate a focus error signal by a beam size method and two pairs of sub-beam light receiving elements provided by one pair with respect to each of a pair of the three-division light receiving elements, the two pairs of sub-beam light receiving elements for receiving the high-order beams generated from the sub-beams reflected by the recording medium to generate a tracking error signal by a three-beam method, and each of the three-division light receiving elements is divided into three light receiving regions by two parallel division lines, and the light emission part is placed so that a straight line connecting light emission points of the first and second light emission sources is parallel to the division lines of the three-division light receiving element.

1 . An optical pickup, comprising: 
 a light source that emits a first light beam;    a grating that generates a first sub-beam and a second sub-beam from the first light beam, wherein the first light beam, the first sub-beam, and the second sub-beam reflect off of a recording medium as a reflected first light beam, a reflected first sub-beam, and a reflected second sub-beam, respectively;    a hologram that generates a first beam and a second beam from the reflected first light beam, that generates a third beam and a fourth beam from the reflected first sub-beam, and that generates a fifth beam and a sixth beam from the reflected second sub-beam; and    a detector that detects the first beam, the second beam, the third beam, the fourth beam, the fifth beam, and the sixth beam.    
   
   
       2 . The optical pickup as claimed in  claim 1 , wherein the detector generates a focus error signal and a tracking error signal based on the first beam, the second beam, the third beam, the fourth beam, the fifth beam, and the sixth beam.  
   
   
       3 . The optical pickup as claimed in  claim 2 , wherein the tracking error signal is determined based on the third beam, the fourth beam, the fifth beam, and the sixth beam.  
   
   
       4 . The optical pickup as claimed in  claim 3 , wherein the tracking error signal is determined based on a difference between a sum of the third beam and the fourth beam and a sum of the fifth beam and the sixth beam.  
   
   
       5 . The optical pickup as claimed in  claim 2 , wherein the focus error signal is determined based on the first beam and the second beam.  
   
   
       6 . The optical pickup as claimed in  claim 5 , wherein the detector comprises a first photodetector, a second photodetector, a third photodetector, a fourth photodetector, a fifth photodetector, and a sixth photodetector, 
 wherein the first photodetector, the second photodetector, and the third photodetector detect the first beam, and    wherein the fourth photodetector, the fifth photodetector, and the sixth photodetector detect the second beam.    
   
   
       7 . The optical pickup as claimed in  claim 6 , wherein the focus error signal is determined based on a difference between a sum of outputs of the first photodetector, the third photodetector, and the fifth photodetector and a sum of outputs of the second photodetector, the fourth photodetector, and the sixth photodetector.  
   
   
       8 . The optical pickup as claimed in  claim 6 , wherein the detector comprises a seventh photodetector, an eight photodetector, a ninth photodetector, and a tenth photodetector, and 
 wherein the seventh photodetector detects the third beam, the eighth photodetector detects the fifth beam, the ninth photodetector detects the fourth beam, and the tenth photodetector detects the sixth beam.    
   
   
       9 . The optical pickup as claimed in  claim 1 , wherein the light source emits a second light beam, 
 wherein the grating generates a third sub-beam and a fourth sub-beam from the second light beam, wherein the second light beam, the third sub-beam, and the fourth sub-beam reflect off of a recording medium as a reflected second light beam, a reflected third sub-beam, and a reflected fourth sub-beam, respectively,    wherein the hologram generates a seventh beam and a eighth beam from the reflected second light beam, that generates a ninth beam and a tenth beam from the reflected third sub-beam, and that generates a eleventh beam and a twelfth beam from the reflected fourth sub-beam, and    wherein the detector detects the seventh beam, the eighth beam, the ninth beam, the tenth beam, the eleventh beam, and the twelfth beam.    
   
   
       10 . The optical pickup as claimed in  claim 9 , wherein the light source comprises a first laser that emits the first light beam at a first wavelength and comprises a second laser that emits the second light beam at a second wavelength, 
 wherein the first wavelength is different than the second wavelength, and    wherein the first laser is integrally formed with the second laser.    
   
   
       11 . The optical pickup as claimed in  claim 9 , wherein the detector comprises: 
 a first photodetector that detects the first beam and the seventh beam;    a second photodetector that detects the second beam and the eighth beam;    a third photodetector that detects the third beam and the ninth beam;    a fourth photodetector that detects the fourth beam and the tenth beam;    a fifth photodetector that detects the fifth beam and the eleventh beam; and    a sixth photodetector that detects the sixth beam and the twelfth beam.    
   
   
       12 . The optical pickup as claimed in  claim 9 , wherein the light source comprises a first laser that emits the first light beam at a first wavelength and comprises a second laser that emits the second light beam at a second wavelength, 
 wherein the first wavelength is different than the second wavelength, and    wherein the first laser is integrally formed with the second laser.    
   
   
       13 . The optical pickup as claimed in  claim 9 , wherein the detector comprises a first photodetector, a second photodetector, a third photodetector, a fourth photodetector, a fifth photodetector, a sixth photodetector, a seventh photodetector, and an eight photodetector, 
 wherein the first photodetector detects the first beam and the ninth beam,    wherein the second photodetector detects the second beam and the tenth beam,    wherein the third photodetector detects the third beam,    wherein the fourth photodetector detects the fourth beam,    wherein the fifth photodetector detects the fifth beam and the seventh beam,    wherein the sixth photodetector detects the sixth beam and the eighth beam,    wherein the seventh photodetector detects the eleventh beam, and    wherein the eighth photodetector detects the twelfth beam.    
   
   
       14 . The optical pickup as claimed in  claim 13 , wherein the first photodetector comprises a first sub-detector, a second sub-detector, and a third sub-detector, 
 wherein the second photodetector comprises a fourth sub-detector, a fifth sub-detector, and a sixth sub-detector, and    wherein a first focus error signal is determined based on a difference between a sum of outputs of the first sub-detector, the third sub-detector, and the fifth sub-detector and a sum of outputs of the second sub-detector, the fourth sub-detector, and the sixth sub-detector when the first light beam is emitted.    
   
   
       15 . The optical pickup as claimed in  claim 14 , wherein the fifth photodetector comprises a seventh sub-detector, an eighth sub-detector, and a ninth sub-detector, 
 wherein the sixth photodetector comprises a tenth sub-detector, an eleventh sub-detector, and a twelfth sub-detector, and    wherein a second focus error signal is determined based on a difference between a sum of outputs of the seventh sub-detector, the ninth sub-detector, and the eleventh sub-detector and a sum of outputs of the eighth sub-detector, the tenth sub-detector, and the twelfth sub-detector when the second light beam is emitted.    
   
   
       16 . The optical pickup as claimed in  claim 15 , wherein a first tracking signal is determined based on a difference between a sum of outputs of the third photodetector and the fourth photodetector and a sum of outputs of the fifth photodetector and the sixth photodetector when the first light beam is emitted, and 
 wherein a second tracking signal is determined based on a difference between a sum of outputs of the first photodetector and the fourth photodetector and a sum of outputs of the seventh photodetector and the eighth photodetector when the second light beam is emitted.    
   
   
       17 . The optical pickup as claimed in  claim 9 , wherein the detector comprises a first photodetector, a second photodetector, a third photodetector, a fourth photodetector, a fifth photodetector, a sixth photodetector, a seventh photodetector, an eight photodetector, a ninth photodetector, a tenth photodetector, an eleventh photodetector, and a twelfth photodetector, 
 wherein the first photodetector detects the third beam and the ninth beam,    wherein the second photodetector detects the fourth beam and the tenth beam,    wherein the third photodetector, the fifth photodetector, and the seventh photodetector detect the first beam,    wherein the fourth photodetector, the sixth photodetector, and the eighth photodetector detect the second beam,    wherein the fifth photodetector, the seventh photodetector, and the ninth photodetector detect the seventh beam,    wherein the sixth photodetector, the eighth photodetector, and the tenth photodetector detect the eighth beam,    wherein the eleventh photodetector detects the fifth beam and the eleventh beam, and    wherein the twelfth photodetector detects the sixth beam and the twelfth beam.    
   
   
       18 . The optical pickup as claimed in  claim 17 , wherein a first focus error signal is determined based on a difference between a sum of outputs of the third photodetector, the sixth photodetector, and the seventh photodetector and a sum of outputs of the fourth photodetector, the fifth photodetector, and the eighth photodetector when the first light beam is emitted.  
   
   
       19 . The optical pickup as claimed in  claim 18 , wherein a second focus error signal is determined based on a difference between a sum of outputs of the fifth photodetector, the ninth photodetector, and the eighth photodetector and a sum of outputs of the sixth photodetector, the seventh photodetector, and the tenth photodetector when the second light beam is emitted.  
   
   
       20 . The optical pickup as claimed in  claim 19 , wherein a first tracking signal is determined based on a difference between a sum of outputs of the first photodetector and the second photodetector and a sum of outputs of the eleventh photodetector and the twelfth photodetector when the first light beam is emitted, and 
 wherein a second tracking signal is determined based on a difference between a sum of outputs of the first photodetector and the second photodetector and a sum of outputs of the eleventh photodetector and the twelfth photodetector when the second light beam is emitted.