Method and apparatus for calibrating an optical disk system

A method for calibrating the focus of an optical beam in an optical disk system having a controllable focus system and at least one mark having a center written on the disk comprising:

• (a) directing a light beam through said adjustable focus system to impinge on said disk, defining a substantially circumferential path of said impingment, said path being no more than a maximum tolerable distance from the center of the mark;
• (b) obtaining a first value related to the reflectance of said beam at a point along said path in the vicinity of said center of said mark;
• (c) obtaining a second value related to reflectance a first distance in a first direction away from said mark;
• (d) obtaining a third value related to the difference between said first value and said second value;
• and
• (e) using said third value to adjust said adjustable focus system by a focus adjustment amount.

A method for obtaining timing calibration of a write pulse to within a minimum tolerance with respect to timing of a read circuit in an optical disk system, comprising:

• (a) providing an optical disk having at least one unwritten mark position having a center;
• (b) providing a light source for impingement of light on said disk wherein light from said light source can be pulsed at a desired power level, the timing of said pulsing being controllable by a write delay, said write delay being adjustable to any of a plurality of delay amounts;
• (c) setting said adjustable write delay to a first value;
• (d) using said write delay set at said first delay value to pulse said light source to impinge on said disk no more than a first distance from the center of said unwritten mark position wherein said light source is pulsed at a power level sufficiently low that there is no writing of a mark;
• (e) using the read circuit to obtain a first quantity related to the reflectance of said pulsed light;
• (f) setting the amount of delay of said write delay to a second value different from said first value;
• (g) using said write delay set at said second delay value to pulse said light source wherein said light source is pulsed at a power level sufficiently low that there is no writing of a mark;
• (h) using said read circuit to obtain a second quantity related to the reflectance of said pulsed light;
• and
• (i) using at least said first quantity and said second quantity to determine whether said write beam has been calibrated to within the minimum tolerance.

A method of conducting read, focus and write calibration in an optical disk system for reading and recording marks along a circumferential path comprising:

• adjusting a programmable read delay circuit in response to a first value related to reflectance at a point along the path preceding a first mark and a second value related to reflectance at a point along the path following said first mark;
• performing a focus calibration by adjusting a focus in response to a difference between reflectances in the vicinity of a second mark and at an adjacent location spaced from said second mark;
• and
• conducting a write calibration by repeatedly adjusting a programmable write delay circuit at least until a reflectance value is obtained by a read circuit which is greater than a reflectance value obtained using least one other delay circuit adjustment.

A method for automatically calibrating an adjustable calibration point for at least one of a read clock delay, a write clock delay, and an adjustable focus in an optical disk system having a disk for reading and recording marks at a plurality of mark positions, said calibration occurring after substantially each activation of the system and prior to each initial access of the system by the user, the method comprising:

• detecting the occurrence of activation of the system;
• calibrating said adjustment point after said detection of activation by a method comprising:
• obtaining a first value related to reflectance in the vicinity of a mark position on the disk;
• obtaining a second value related to reflectance in the vicinity of a mark position on the disk;
• obtaining a third value related to the difference between said first value and said second value;
• and
• determining whether the adjustable calibration point is adjusted to within a calibration criterion using said third value.

Apparatus for adjusting the timing of data extraction from a read signal in an optical disk system comprising:

• an optical disk having at least one mark having a center written thereon;
• a light source controllable to cause a light beam to impinge on substantially the center of said mark at a first point in time;
• a clock circuit for generating a periodic signal having an adjustable phase which defines a second point in time within a first time interval of said first point in time;
• means for obtaining at least first and second values, said first value being related to a magnitude of the read signal at a third point in time previous to said second point in time and said second value related to a magnitude of the read signal at a fourth point in time subsequent to said second point in time;
• means for obtaining a third value related to the difference of said first value and said second value;
• and
• means for adjusting the phase of said clock using said third value.

Apparatus for focusing light onto an optical disk having at least one mark having a center written thereon comprising:

• an adjustable focus system;
• a light source for providing a light beam;
• means for directing said light beam through said adjustable focus system to impinge on said disk along a substantially circumferential path of impingment, said path being no more than a maximum tolerable distance from the center of the mark;
• means for obtaining a first value related to the reflectance of said beam at a point along said path in the vicinity of said center of said mark;
• means for obtaining a second value related to reflectance a first distance in a first direction away from said mark;
• means for obtaining a third value related to the difference between said first value and said second value;
• and
• means for adjusting said adjustable focus system using said third value.

Apparatus for obtaining timing calibration of a write pulse to within a minimum tolerance with respect to timing of a read circuit in an optical disk system comprising:

• an optical disk having at least one unwritten mark position having a center;
• a light source for impingment of light on said disk wherein light from said light source can be pulsed at a desired power level, the timing of said pulsing being controllable by a write delay, said write delay being adjustable to any of a plurality of delay amounts;
• means for setting said write beam delay amount to a first value;
• means for pulsing said light source to impinge on said disk a first distance from the center of said unwritten mark position using said write delay set at said first delay value wherein said light source is pulsed at a power level sufficiently low that there is no writing of a mark;
• means for obtaining a first quantity related to the reflectance of said pulsed light using the read circuit;
• means for setting the amount of delay of said write delay to a second value different from said first value;
• means for pulsing said light source using said write delay set at said second delay value wherein said light source is pulsed at a power level sufficiently low that there is no writing of a mark;
• means for obtaining a second quantity related to the reflectance of said pulsed light using the read circuit;
• and
• means for determining whether said write beam has been calibrated to within minimum tolerance using
• at least said first quantity and said second quantity.