Beam position control system of an optical disk unit

An optical disk unit comprising:

• an object lens;
• an optical head for passing at least two beams including a write beam and a read beam through said object lens, and simultaneously writing and reading data to and from a medium with a plurality of the beams;
• lens drive means for driving said object lens to simultaneously move a plurality of the beams across tracks of the medium;
• a galvanomirror;
• galvanomirror drive means for driving said galvanomirror to move only the read beam across tracks of the medium;
• position detection means for detecting the position of said galvanomirror and providing a galvanomirror position signal;
• tracking error detection means for detecting and providing a tracking error signal according to a return beam of the read beam from the medium;
• position servo means for driving said galvanomirror according to the tracking error signal, to carry out tracking control of the read beam;
• position lock means for locking said galvanomirror at a predetermined position according to said galvanomirror position signal;
• a first servo switch turned ON for tracking control of the read beam and enabling said position servo means;
• and
• a second servo switch turning ON when the tracking control of the read beam is disabled, and enabling said position lock means, a read beam control system comprising:
• offset addition means for adding an offset signal to said galvanomirror position signal provided by said position detection means;
• and
• control means for turning ON said servo switch for enabling the position lock control of said galvanomirror when the unit is energized or retried, reading said galvanomirror position signal, finding the offset signal for zeroing the galvanomirror position signal, and providing the offset signal to said offset addition means during a seek operation with the write beam.

An optical disk unit comprising:

• an optical head for writing and reading data to and from a medium with write and read beams, respectively;
• lens drive means for driving an object lens to simultaneously move the write and read beams across tracks of the medium;
• a direction change means for changing direction of at least one of the write and read beams;
• direction changer drive means for driving said direction change means to move one of the write and read beams across the tracks of the medium;
• position detection means for detecting the position of said direction change means and providing a position signal;
• tracking error detection means for detecting and providing a tracking error signal according to a return beam from the medium;
• position servo means for driving said direction change means according to the tracking error signal, to carry out tracking control of one of the write and read beams;
• and
• position lock means for locking said direction change means at a predetermined position according to the positional signal;
• a beam position control system, comprising:
• a first servo switch for starting and stopping a position servo operation of said position servo means;
• a second servo switch for starting and stopping a position lock operation of the position lock means;
• control means for turning ON and OFF said first and second servo switches according to a beam position control status, to enable one combination of one of the position servo operation and the position lock operation, both of the position servo operation and the position lock operation, and neither of the position servo operation and position lock operation;
• first abnormality detection means for detecting an abnormality in the tracking error signal and notifying said control means of the abnormality;
• and
• second abnormality detection means for detecting an abnormality in the position signal of said direction change means and notifying said control means of the abnormality.

An optical disk unit comprising:

• an optical head for writing data to a medium with a write beam and reading data from a medium with a read beam;
• lens drive means for driving an object lens to simultaneously move the read and write beams across tracks of the medium;
• direction change means for changing the direction of at least one of the read and write beams;
• direction changer drive means for driving said direction change means to move one of the read and write beams across tracks of the medium;
• position detection means for detecting a position of said direction changing means and providing a position signal;
• tracking error detection means for detecting and providing a tracking error signal according to a return beam from the medium;
• position servo means for driving said direction change means according to the tracking error signal, to carry out tracking control of one of the read and write beams;
• position lock means for locking said direction change means at a predetermined position according to the position signal;
• and
• a beam position control system, comprising:
• a first servo switch for starting and stopping a position servo operation of said position servo means;
• a second servo switch for starting and stopping a position lock operation of said position lock means;
• a third servo switch for applying a forward drive signal to said direction changer drive means;
• a fourth servo switch for applying a reverse drive signal to said direction changer drive means;
• and
• control means for turning ON and OFF said first and second servo switches according to a beam position control status and for enabling one combination of one of the position servo operation and the position lock operation, both of the position servo operation and the position lock operation, and neither of the position servo operation and the position lock operation, said control means turning OFF said first servo switch when only the read beam is jumped across tracks during the position servo operation of the read beam to disable both the position servo operation and the position lock operation, and said control means controlling one of said third servo switch and said fourth servo switch.

An optical disk unit comprising:

• an optical head for writing data to a medium with a write beam and reading data from a medium with a read beam;
• lens drive means for driving an object lens to simultaneously move the read and write beams across tracks of the medium;
• direction change means for changing the direction of at least one of the read and write beams;
• direction changer drive means for driving said direction change:
• means to move :one of the read and write beams across tracks of the medium;
• position detection means for detecting a position of said direction changing means and providing a position signal;
• tracking error detection means for detecting and providing a tracking error signal according to a return beam from the medium;
• position servo means for driving said direction change means according to the tracking error signal, to carry out tracking control of one of the read and write beams;
• and
• position lock means for locking said direction change means at a predetermined position according to the position signal;
• a beam position control system, comprising:
• a first servo switch for starting and stopping a position servo operation of said position servo means;
• a second servo switch for starting and stopping a position lock operation of said position lock means;
• and
• control means for turning ON and OFF said first and second servo switches according to a beam position control status, and for enabling one combination of one of the position, servo operation and the position lock operation, both of the position servo operation and the position lock operation, and neither of the position servo operation and the position lock operation, said control means turning ON said first servo switch to carry out the position servo operation of the read beam, fetching, during this operation, the position signal from said position detecting means and finding an offset signal for zeroing the position signal, said control means turning OFF said first servo switch when only the write beam is jumped across tracks, to disable the position servo operation of the read beam until the jump is completed, and at the same time, applying the offset signal to lock said direction change means at an offset state, and said control means turning OFF said second servo switch and turning ON said first servo switch after the completion of the track jump, to resume the position servo operation.

An optical disk unit comprising:

• an optical head for writing data to a medium with a write beam and reading data from a medium with a read beam;
• lens drive means for driving an object lens to simultaneously move the read and write beams across tracks of the medium;
• direction change means for changing the direction of at least one of the read and write beams;
• direction changer drive means for driving said direction change means to move one of the read and write beams across tracks of the medium;
• position detection means for detecting a position of said direction changing means and providing a position signal;
• tracking error detection means for detecting, and providing a tracking error signal according to a return beam from the medium;
• position servo means for driving said direction change means according to the tracking error signal, to carry out tracking control of one of the read and write beams;
• and
• position lock means for locking said direction change means at a predetermined position according to the position signal;
• a beam position control system, comprising:
• a first servo switch for starting and stopping a position servo operation of said position servo means;
• a second servo switch for starting and stopping a position lock operation of said position lock means;
• a third servo switch for applying a forward drive signal to said direction changer drive means;
• a fourth servo switch for applying a reverse drive signal to said direction changer drive means, when a higher device provides said control means with a seek instruction indicating differences for positional deviations of the read beam and the write beam, the difference for positional deviation of the write beam specified in the seek instruction is zero;
• and
• control means for turning ON and OFF said first and second servo switches according to abeam position control,status, and for enabling one combination of one of the position servo operation and the position lock operation, both of the position servo operation and the position lock, operation and neither of the position servo operation and the position lock operation, said control means turning OFF said first servo switch to disable both the position servo operation of the read beam and the position lock operation, and controlling one of said third servo switch and said fourth servo switch.

An optical disk unit comprising:

• an optical head for writing data to a medium with a write beam and reading data from a medium with a read beam;
• lens drive means for driving an object lens to simultaneously move the read and write beams across tracks of the medium;
• direction change means for changing the direction of at least one of the read and write beams;
• direction changer drive means for driving said direction change means to move one of the read and write beams across tracks of the medium;
• position detection means for detecting a position of said direction changing means and providing a position signal;
• tracking error detection means for detecting and providing a tracking error signal according to a return beam from the medium;
• position servo means for driving said direction change means according to the tracking error signal to carry out tracking control of one of the read and write beams;
• and
• position lock means for locking said direction change means at a predetermined position according to the position signal;
• a beam position control system comprising:
• a first servo switch for starting and stopping a position servo operation of said position servo means;
• a second servo switch for starting and stopping a position lock operation of said position lock means;
• and
• control means for turning ON and OFF said first and second servo switches according to a beam position control status, and for enabling one combination of one of the position servo operation and the position lock operation, both of the position servo operation and the position lock operation, and neither of the position servo operation and the position lock operation, when a higher device provides said control means with a seek instruction indicating differences for positional deviations of the read beam and the write beam, the difference for the write beam specified in the seek instruction being greater than zero, said control means fetching the position signal from said position detection means during said position servo operation of the read beam with said first servo switch being ON, finding an offset signal with .which the position signal is unchanged under a position locked state, and adding an offset corresponding to a difference between the read beam and the write beam to the offset signal to form an offset signal for a new lock position, turning OFF said first servo switch, to disable the position servo operation of the read beam during a track jump of the write beam and applying the offset signal to lock the position of said direction change means at an offset state, and turning OFF said second servo switch after the completion of the track jump and turning ON said first servo switch to resume the position operation.

An optical disk unit comprising:

• an optical head for Writing and reading data to and from a medium with write and read beams, respectively;
• lens drive means for driving an object lens to simultaneously move the write and read beams across tracks of the medium;
• direction change means for changing direction of at least one of the write and read beams;
• direction changer drive means for driving said direction change means to move one of the write and read beams across the tracks of the medium;
• position detection means for detecting the position of said direction change means and providing a position signal;
• tracking error detection means for detecting and providing a tracking error signal according to a return beam from the medium;
• position servo means for driving said-direction change means according to the tracking error signal, to carry out tracking control of one of the write and read beams;
• and
• position lock means for locking said direction change means at a predetermined position according to the positional signal;
• a beam position control system, comprising:
• a first servo switch for starting and stopping a position servo operation of said position servo means;
• and
• a second servo switch for starting and stopping a position lock operation of said position lock means;
• control means for turning ON and OFF said first and second servo switches according to a beam position control status, to enable one combination of one of the position servo operation and the position lock operation, both of the position servo operation and the position lock operation, and neither of the position servo operation and position lock operation;
• first abnormality detection means for detecting an abnormality in the tracking error signal and notifying said control means of the abnormality;
• and
• second abnormality detection means for detecting an abnormality in the position signal of said direction change means and notifying said control means of the abnormality,
• when said beam position control system receives the abnormality notices from said first and second abnormality detection means, said control means turns OFF said first servo switch to disable the tracking control of one of the write and read beams, and turns ON said second servo switch to carry out position lock control for returning said direction change means to a predetermined position.