Optical disc device

Abstract

An optical disc drive usable with discs to which data is continuously recorded and discs having a sector format can quickly resume playback signal output after passing imperfection causing potential reading errors, and plays disc with few read errors. A detection signal generator detects DC level fluctuation in the playback signal read from the disc and generates a detection signal tracking the DC level fluctuation. A selector selects a detection signal or a null signal without valid polarity based on the detection signal generated by the detection signal generator and input to the selector. A clamping unit performs a clamping process to suppress DC level fluctuation in the playback signal based on the detection signal when the selection unit selects the detection signal, and does not perform the clamping process when the selection unit selects the null signal. A signal processor performs specific signal processes based on clamping unit output.

1. An optical disc apparatus comprising:
 a detection signal generator which detects DC level fluctuation in a playback signal read from an optical disc and generates a detection signal tracking the DC level fluctuation;  
 a selection unit which selects the detection signal or a null signal without valid polarity based on the detection signal received from the detection signal generator;  
 a clamping unit which performs a clamping process to suppress DC level fluctuation in the playback signal based on the detection signal when the selection unit selects the detection signal, and which does not perform the clamping process when the selection unit selects the null signal; and  
 a signal processing unit which performs a specific signal process based on clamping unit output.  
 
     
     
       2. An optical disc apparatus as described in  claim 1 , further comprising a controller which generates a control signal instructing which signal to select,
 wherein the selection unit selects a signal based on the control signal generated by the controller.  
 
     
     
       3. An optical disc apparatus as described in  claim 2 , wherein the controller again generates a control signal instructing selection of the detection signal when a read error occurs after generating a control signal instructing selection of the null signal a plurality of times. 
     
     
       4. An optical disc apparatus as described in  claim 3 , wherein the detection signal generator is an amplitude fluctuation sensing unit which detects playback signal amplitude and generates an amplitude fluctuation signal. 
     
     
       5. An optical disc apparatus as described in  claim 4 , further comprising at least one additional one of the detection signal generator; and
 an amplitude fluctuation signal delay unit which delays the amplitude fluctuation signal generated by the amplitude fluctuation sensing unit, and generates an extended amplitude fluctuation signal extended by a delay period,  
 wherein the controller generates a control signal instructing selection of the extended amplitude fluctuation signal when a read error occurs after generating a control signal instructing selection of the amplitude fluctuation signal.  
 
     
     
       6. An optical disc apparatus as described in  claim 5  wherein a recording guide groove wobbling at a specific period is formed on the optical disc, the optical disc apparatus further comprising:
 a dropout detection unit which detects dropout of a wobble signal corresponding to the guide groove period when reading the optical disc, and generates a dropout detection signal; and  
 a signal delay unit which delays the dropout detection signal generated by the dropout detection unit, and generates an extended dropout detection signal that is extended for a delay period,  
 wherein the controller additionally generates a control signal instructing selection of the dropout detection signal, and generates a control signal instructing selection of the extended dropout detection signal when a read error occurs.  
 
     
     
       7. An optical disc apparatus for applying a specific signal process to a playback signal read from an optical disc, the optical disc apparatus comprising:
 a digitizing unit which digitizes the playback signal and outputs a digital playback signal;  
 a digital voltage generator which forms a feedback loop with the digitizing unit to output a voltage signal such that a duty ratio of the digitized playback signal from the digitizing unit is a specific value;  
 a differential amplifier which outputs a differential signal between the playback signal and the voltage signal of the digital voltage generator; and  
 a signal processing unit which performs a specific signal process based on the differential signal from the differential amplifier.  
 
     
     
       8. A signal processing circuit used for an optical disc apparatus, said signal processing circuit comprising:
   a detection signal generator operable to detect DC level fluctuation in a playback signal read from a optical disc, and to generate a detection signal indicating the DC level fluctuation;        a selection unit operable to select the detection signal or a null signal without valid polarity based on the detection signal received from the detection signal generator;        a unit operable to suppress the DC level fluctuation in the playback signal based on the detection signal when the selection unit selects the detection signal, and not perform the suppression when the selection unit selects the null signal; and        a signal processing unit operable to perform a specific signal process based on an output of the unit.     
     
     
       9. A signal processing circuit according to  claim 8 , wherein the detection signal generator is operable to detect the DC level fluctuation in an RF signal, and the unit is operable to suppress the DC level fluctuation in the RF signal based on the detection signal when the selection unit selects the detection signal, and not perform the suppression when the selection unit selects the null signal. 
     
     
       10. A signal processing circuit according to  claim 8 , wherein the detection signal generator is operable to detect the DC level fluctuation in a TE signal, and the unit is operable to suppress the DC level fluctuation in the TE signal based on the detection signal when the selection unit selects the detection signal, and not perform the suppression when the selection unit selects the null signal. 
     
     
       11. A signal processing method, comprising:
   detecting DC level fluctuation in a playback signal read from an optical disc and generating a detection signal indicating the DC level fluctuation;        selecting the detection signal or a null signal without valid polarity based on the detection signal;        suppressing the DC level fluctuation in the playback signal based on the detection signal when the detection signal is selected, and not performing the suppression when the null signal is selected; and        performing a specific signal process based on a result of the suppressing.     
     
     
       12. A signal processing method according to  claim 11 , wherein the playback signal is an RF signal. 
     
     
       13. A signal processing method according to  claim 11 , wherein the playback signal is a TE signal. 
     
     
       14. A signal processing circuit according to  claim 8 , wherein the unit comprises:
   a bypass filter including:      a capacitor;        a first resistor;        a second resistor; and        a switch,          the switch being turned to a first position to reduce a time constant of the bypass filter when the selection unit selects the detection signal to suppress the DC level fluctuation.