Focusing control system for use in an information recording and reproducing apparatus

A focusing control system for use in an information recording and reproducing apparatus, said focusing control system performing a focusing control operation wherein a beam for reproducing signals from a recording surface of a recording medium is focused on the recording surface of the recording medium, said focusing control system comprising:

• a deviation detection means for detecting an amount of deviation between a position of a point on which the beam is focused and a position of the recording surface of the recording medium;
• an amplification means for amplifying an output signal from said deviation detection means, said amplification means having a variable amplification factor;
• an A/D conversion means for converting an output signal from said amplification means to a digital signal;
• a drive means for moving said point on which the beam is focused in a direction perpendicular to the recording surface of the recording medium;
• a focusing control means for controlling said drive means in response to an output signal from said A/D conversion means so that said point on which the beam is focused is positioned on the recording surface of the recording medium, said focusing control means having a variable gain;
• and
• a decision means for determining as to whether an output value of said deviation detection means falls within a given range, said decision means outputting a signal when the output value of said deviation detection means falls within the given range;
• wherein the amplification factor of said amplification means is reduced between the time when the focusing control operation is triggered and the time said decision means outputs the signal and the gain of said focusing control means is increased in accordance with a reduction in amplification factor of said amplification means.

A focusing control system for use in an information recording and reproducing apparatus, said focusing control system performing a focusing control operation wherein a beam for reproducing signals from a recording surface of a recording medium is focused on the recording surface of the recording medium, said focusing control system comprising:

• a deviation detection means for detecting an amount of deviation between a position of a point on which the beam is focused and a position of the recording surface of the recording medium;
• an amplification means for amplifying an output signal from said deviation detection means, said amplification means having a variable amplification factor;
• an A/D conversion means for converting an output signal from said amplification means to a digital signal;
• a drive means for moving said point on which the beam is focused in a direction perpendicular to the recording surface of the recording medium;
• a focusing control means for controlling said drive means in-response to an output signal from said A/D conversion means so that said point on which the beam is focused is positioned on the recording surface of the recording medium, said focusing control means having a variable gain;
• and
• a decision means for determining as to whether an output value of said deviation detection means falls within a given range, said decision means outputting a first signal when the output value of said deviation detection means falls within the given range, said decision means outputting a second signal when the output value of said deviation detection means deviates from the given range;
• wherein the amplification factor of said amplification means is reduced during a period in which said decision means outputs said second signal during the focusing control operation and the gain of said focusing control means is increased in accordance with a reduction in amplification factor of said amplification means.