Method and apparatus for optical recording and reproducing with tracking servo reducing track offset

Abstract

Disclosed is an optical recording and reproducing apparatus comprising a light source directing a light spot toward a recording medium, a detection system detecting light reflected from the recording medium to derive an electrical signal from the reflected light, an information processing circuit modulating the intensity of the light spot according to writing pulses to record information on the recording medium and using the electrical signal to reproduce information from the recording medium, and a tracking servo circuit carrying out tracking servo operation on the basis of the electrical signal and including an extracting circuit connected to a source of extracting pulses having a pulse width at least equal to the writing pulse width so that writing pulse parts contained in the electrical signal are extracted during recording information, whereby a track offset occurring during information recording can be minimized, and the stability of the tracking servo system can be improved.

1. An optical recording and reproducing apparatus comprising:
 light illuminating means for illuminating a light spot toward a recording medium;  
 a detection system detecting light reflected from said recording medium to derive an electrical signal from said reflected light;  
 an information processing circuit modulating the intensity of said light spot according to writing pulses to record information on said recording medium and using said electrical signal to reproduce information from said recording medium; and  
 a tracking servo circuit carrying out a tracking servo operation on the basis of said electrical signal, said tracking servo circuit including an extracting circuit for extracting time-wise portions of said electrical signal, and means for applying extracting pulses having a pulse width at least equal to greater than the writing pulse width to said extracting circuit so that time-wise portions of said electrical signal corresponding to the writing pulses during recording of information are not utilized for the tracking servo operation when the extracting pulses are present.  
 
     
     
       2. An optical recording and reproducing apparatus according to  claim 1 , wherein the pulse width of said extracting pulses applied to said extracting circuit is determined while taking into account the frequency characteristics of a tracking servo signal of said tracking servo circuit. 
     
     
       3. An optical recording and reproducing apparatus according to  claim 1 , wherein said tracking servo circuit includes a gain change-over circuit for changing over the gain of said tracking servo circuit depending on whether information is to be recorded or reproduced. 
     
     
       4. An optical recording and reproducing apparatus according to  claim 1 , wherein the means for applying extracting pulses applies the extracting pulses to the extracting circuit at a timing corresponding to a timing of the writing pulses, the tracking servo circuit including a tracking servo loop with a variable gain. 
     
     
       5. An optical disk apparatus comprising:
 a light source;  
 an optical system guiding light emitted from said light source toward a recording medium on a disk plate;  
 an information detection circuit separating light reflected from said recording medium on said disk plate from said optical system and photoelectrically converting said reflected light into an electrical signal;  
 an information processing circuit recording and reproducing information on and from said recording medium on said disk plate; and  
 means connected to said information detection circuit for applying extracting pulses having a pulse width at least equal to greater than that of writing pulses for recording of information to said information detection circuit so that time-wise portions of said electrical signal corresponding to the writing pulses during recording of information are not utilized for a tracking servo operation of a tracking servo circuit when the extracting pulses are present.  
 
     
     
       6. An optical disk apparatus according to  claim 5 , wherein the pulse width of said extracting pulses applied to said information detection circuit is determined while taking into account the frequency characteristics of a tracking servo signal of said tracking servo circuit. 
     
     
       7. An optical disk apparatus according to  claim 5 , wherein the means for applying extracting pulses applies the extracting pulses to said information detection circuit at a timing corresponding to a timing of the writing pulses, the tracking servo circuit including a tracking servo loop with a variable gain. 
     
     
       8. A method of optical recording and reproduction including the steps of directing a light spot toward a recording medium, modulating the intensity of said light spot according to writing pulses to record information on said recording medium, and detecting light reflected from said recording medium to reproduce information from said recording medium, said method comprising the step of carrying out a tracking servo operation on the basis of an electrical signal detected from said reflected light and including applying extracting pulses having a pulse width at least equal to greater than that of said writing pulses so that time-wise portions of said electrical signal corresponding to the writing pulses during recording of information are not utilized for the tracking servo operation when the extracting pulses are present. 
     
     
       9. A method of optical recording and reproduction according to  claim 8 , wherein the pulse width of said extracting pulses is determined while taking into account the frequency characteristics of a tracking servo signal of said tracking servo operation. 
     
     
       10. A method of optical recording and reproduction according to  claim 8 , wherein the gain of a circuit carrying out said tracking servo operation is changed over depending on whether information is to be recorded or reproduced. 
     
     
       11. A method of optical recording and reproduction according to  claim 8 , wherein the applying of extracting pulses includes applying the extracting pulses at a timing corresponding to a timing of the writing pulses, the tracking servo operation providing a tracking servo loop with a variable gain.