Optical disc apparatus

An objective lens tilt control apparatus comprising:

• first driving means for outputting a drive value to drive first focus direction transferring means for transferring one end of an objective lens in the focus direction thereof;
• second driving means for outputting a drive value to drive second focus direction transferring means for transferring the other end of the objective lens in the focus direction thereof;
• drive level difference detecting means for detecting the drive values of said first driving means and said second driving means and outputting the difference thereof;
• and
• controlling means for controlling said first driving means and said second driving means in such a way that the difference between said drive values becomes a predetermined value.

A focus drive apparatus comprising:

• driving means for outputting a drive value for driving focus direction transferring means for transferring an objective lens in the focus direction thereof;
• and
• drive level detecting means for detecting said drive value,
• wherein using the output of said drive level detecting means when said drive value is set to zero as a reference level, the DC level of the output of said driving means is corrected based on said reference level.

A focus drive apparatus comprising:

• driving means for outputting a drive value for driving focus direction transferring means for transferring an objective lens in the focus direction thereof;
• and
• drive level detecting means for detecting said drive value,
• wherein using the output of said drive level detecting means when the operation of said driving means is stopped for a predetermined period as a reference level, the DC level of the output of said driving means is corrected based on said reference level.

A focus drive apparatus comprising:

• driving means for outputting a drive value for driving focus direction transferring means for transferring an objective lens in the focus direction thereof;
• and
• drive level detecting means for detecting said drive value,
• wherein using the output of said drive level detecting means when said drive level detecting means is electrically seperated from said focus direction transferring means and a drive value to be output to said focus direction transferring means is set to zero as a reference level, the DC level of the output of said driving means is corrected based on said reference level.

A tracking drive apparatus comprising:

• driving means for outputting a drive value for driving tracking direction transferring means for transferring an objective lens in a radius direction of an information recording medium;
• and
• drive level detecting means for detecting said drive value,
• wherein using the output of said drive level detecting means when said drive value is set to zero as a reference level, the DC level of the output of said driving means is corrected based on said reference level.

A tracking drive apparatus comprising:

• driving means for outputting a drive value for driving tracking direction transferring means for transferring an objective lens in a radius direction of an information recording medium;
• and
• drive level detecting means for detecting said drive value,
• wherein using the output of said drive level detecting means when an operation of said driving means is stopped for a predetermined period as a reference level, the DC level of the output of said corrected based on said reference level.

A tracking drive apparatus comprising:

• driving means for outputting a drive value for driving tracking direction transferring means for transferring an objective lens in a radius direction of an information recording medium;
• and
• drive level detecting means for detecting said drive value,
• wherein using the output of said drive level detecting means when said drive level detecting means is electrically separated from said tracking direction transferring means and a drive value to be output to said tracking direction transferring means is set to zero as a reference level, the DC level of the output of said driving means is corrected based on said reference level.

An objective lens tilt control apparatus comprising:

• driving means for outputting a drive value for driving objective lens tilting means for changing tilt of an objective lens;
• and
• drive level detecting means for detecting said drive value,
• wherein using the output of said drive level detecting means when said drive value is set to zero as a reference level, the DC level of the output of said driving means is corrected based on said reference level.

An objective lens tilt control apparatus comprising:

• driving means for outputting a drive value for driving objective lens tilting means for changing tilt of an objective lens;
• and
• drive level detecting means for detecting said drive value,
• wherein using the output of said drive level detecting means when the operation of said driving means is stopped for a predetermined period as a reference level, the DC level of the output of said driving means is corrected based on said reference level.

An objective lens tilt control apparatus comprising:

• driving means for outputting a drive value for driving objective lens tilting means for changing tilt of an objective lens;
• and
• drive level detecting means for detecting said drive value,
• wherein using the output of said drive level detecting means when said drive level detecting means is electrically separated from the objective lens tilting means and a drive value to be output to said tracking direction transferring means is set to zero as a reference value, the DC level of the output of said driving means is corrected based on said reference level.

An optical disc apparatus comprising:

• a light source for irradiating a light beam onto a data side of an information recording medium;
• converging means for converging said light beam;
• transferring means for transferring said converging means in such a way that the distance between said converging means and said data side changes;
• photo-receiving means for receiving returned light of the light beam reflected by said data side;
• converging state detecting means for generating a signal according to a converging state of the light beam on the data side of said information recording medium based on a signal from said photo-receiving means;
• focus controlling means for outputting a drive signal to said transferring means based on a signal from said converging state detecting means and controlling said light beam in such a way that said light beam is in a predetermined converging state;
• tilting means for tilting said converging means;
• tilt calculating means for determining at least one calculation expression used for calculating a shape of said data side based on said drive signal and determining an amount of tilt of said data side and said converging means using said determined calculation expression;
• and
• tilt controlling means for driving the tilting means according to said amount of tilt and irradiating the light beam onto said data side in a direction substantially perpendicular to said data side.

A method of controlling an optical disc apparatus comprising the steps of:

• driving converging means for converging a light beam irradiated onto a data side of an information recording medium in a direction perpendicular to said data side in such a way that said light beam keeps a predetermined converging state;
• calculating an average value of drive signals for driving said converging means obtained for a period which is an integer multiple of a period during which said information recording medium makes one rotation;
• calculating said average value at two different points in the radius direction of said information recording medium and calculating tilt of said data side based on the average values at said two different points;
• and
• changing the tilt of said converging means based on the tilt of said data side.

A method of controlling tilt of an objective lens comprising the steps of:

• driving both ends of an objective lens in the focus direction thereof;
• detecting a difference between drive signals for driving said both ends;
• and
• controlling means for controlling said first driving means and said second driving means in such a way that the difference between said drive signals takes a predetermined value.

A method of driving an objective lens comprising the steps of:

• outputting a drive signal for driving an objective lens in a predetermined direction;
• detecting said drive signal;
• and
• using a value detected in said detecting step when said drive signal is set to zero as a reference level and correcting the DC level of said drive signal based on said reference level.

A method of driving an objective lens comprising the steps of:

• outputting a drive signal for driving an objective lens in a predetermined direction;
• detecting said drive signal;
• and
• using a value detected in said detecting step when the output of said drive signal is stopped for a predetermined period as a reference level and correcting the DC level of said drive signal based on said reference level.

A method of driving an objective lens comprising the steps of:

• outputting a drive signal for driving transferring means for transferring an objective lens in a predetermined direction;
• detecting said drive signal;
• and
• using a value detected in said detecting step when means for outputting said drive signal is electrically separated from said transferring means and said drive signal is set to zero as a reference level and correcting the DC level of said drive signal based on said reference level.

A method of controlling an optical disc apparatus comprising the steps of:

• driving converging means for converging a light beam irradiated onto a data side of an information recording medium in a direction perpendicular to said data side so as to change the converging state of said light beam;
• receiving returned light of the light beam reflected by said data side;
• generating a signal according to the converging state of the light beam on the data side of said information recording medium based on a signal from said photo-receiving means;
• outputting a drive signal to means for transferring said converging means based on a signal from said converging state detecting means and controlling said light beam in such a way that said beam is in a predetermined converging state;
• determining at least one calculation expression used to calculate the shape of said data side based on said drive signal and calculating an amount of tilt of said data side and said converging means using said determined calculation expression;
• and
• driving means for changing tilt of said converging means according to said amount of tilt and controlling the light beam in such a way that the light beam is irradiated onto said data side in a direction substantially perpendicular to said data side.

A method of controlling an optical disc apparatus comprising the steps of:

• (A) acquiring a plurality of focus drive signals which are obtained by irradiating a light beam a data side of an information recording medium at a plurality of detection positions different with each other in a radial direction of the information recording medium, under the condition that a focus control is conducted such that the light beam irradiating the data side is in a predetermined conversing state;
• (B) determining at least one calculation expression used for calculating a shape of said data side based on the acquired focus drive signals;
• and
• (C) calculating an amount of tile of said data side by using the determined calculation expression and changing the tile of an objective lens based on the calculated amount of the tilt.