Objective lens driving system in a optical pick-up and method of modulating the resonance frequency of its lens holder

A method of modulating the resonance frequency of a lens holder in an objective lens driving system of an optical pick-up having:

• a lens holder which holds an objective lens and has a shaft hole;
• a fixed member which has a journal inserted into said shaft hole;
• a driving coil and a magnet which are arranged opposite each other so as to generate a magnetic force for driving said lens holder along said journal;
• and
• a magnetic piece which is arranged opposite said magnet to hold said lens holder at a neutral position using said magnetic force generated between said magnet and said driving coil while said driving coil is not excited, said method comprising the steps of:
• using a magnetic piece that is magnetized until it is saturated by the emf from the magnetic field generated by said magnet;
• and
• changing said magnetic piece to another magnetic piece with different saturation flux density to modulate the resonance frequency of said lens holder.

A method of modulating resonance frequency of a lens holder in an objective lens driving system of an optical pick-up having:

• a lens holder which holds an objective lens and has a shaft hole;
• a fixed member which has a journal inserted into said shaft hole;
• a driving coil and a magnet which are arranged opposite each other so as to generate a magnetic force for driving said lens holder along said journal;
• and
• a magnetic piece which is arranged opposite said magnet to hold said lens holder at a neutral position using said magnetic force generated between said magnet and said driving coil while said driving coil is not excited, said method comprising the steps of:
• using a magnetic piece which is magnetized until it is saturated by an emf from the magnetic field generated by said magnet;
• and
• changing said magnetic piece to another magnetic piece with different volume, while the saturation flux density for said magnetic piece is maintained constant, to modulate the resonance frequency of said lens holder.