US 5,844,866 A · Method and apparatus for checking the quality of CD-ROMS or the like for reading them at matching speeds

Abstract

CD-ROMS of more or less poor quality, such as those having eccentric center holes or uneven weight distributions circumferentially, tend to overload tracking and focusing servos and hence to invite read errors and retries. Each disk on being loaded into the disk drive is therefore checked as to its eccentricity and wobbling preparatory to reading. The disk is set into rotation at a predetermined speed of, typically, eight times the standard audio CD speed. Disk eccentricity is checked by counting the pulses produced by the transducer as the spot of the read beam crosses the track turns, the tracking servo being cut off for this check. The greater the number of pulse generated during a complete disk revolution, the more eccentric is the disk. Wobble check is done by measuring the maximum amplitude of a focusing servo signal being applied to a focusing actuator coil. The disk is read at eight times the standard audio CD speed if it clears both checks, and at four times the standard audio CD speed if it fails to clear either check.

Claims14

Dependent claims

In an apparatus for data recovery from rotating data storage disks of varying physical qualities, a method comprising the steps of:

(a) rotating a data storage disk at a first predetermined speed;
(b) ascertaining whether at least either of the eccentricity and wobbling of the disk is more than a prescribed limit or not while the disk is in rotation at the first predetermined speed;
(c) reading the disk at the first predetermined speed if said at least either of the eccentricity and wobbling of the disk is found to be not more than the prescribed limit at step (b);
and
(d) reading the disk at a second predetermined speed, which is less than the first predetermined speed, if said at least either of the eccentricity and wobbling of the disk is found to be more than the prescribed limit at step (b).

2 more elements

An apparatus for data recovery from rotating data storage disks of varying physical qualities, wherein the improvement resides in the combination of:

(a) drive means for imparting multiple speed rotation to a data storage disk;
(b) speed command means connected to the drive means for causing the same to rotate the disk at either of a first and a second predetermined speed, the first predetermined speed being higher than the second;
and
(c) disk check means for ascertaining whether at least either of the eccentricity and wobbling of the disk is more than a prescribed limit or not while the disk is in rotation at the first predetermined speed, the disk check means being connected to the speed command means for causing the disk to be read at the first predetermined speed if said at least either of the eccentricity and wobbling of the disk is found to be not more than the prescribed limit, and at the second predetermined speed if said at least either of the eccentricity and wobbling of the disk is found to be more than the prescribed limit.

1 more element

An apparatus for data recovery from rotating data storage disks of varying physical qualities, each disk having data prerecorded thereon along a multiturn track, wherein the improvement resides in the combination of:

(a) drive means for imparting multiple speed rotation to a data storage disk;
(b) a transducer for reading the rotating disk by irradiating the same with a beam of light;
(c) a tracking servo for holding the spot of the beam on the disk in alignment with the multiturn data track thereon;
(d) a focusing servo for holding the beam focused on the disk, the focusing servo including a focusing servo circuit for producing a focusing servo signal, and a focusing actuator activated by the focusing servo signal;
(e) speed command means connected to the drive means for causing the same to rotate the disk at either of a first and a second predetermined speed, the first predetermined speed being higher than the second;
and
(f) disk eccentricity check means connected to the transducer for ascertaining the eccentricity of the disk in terms of a number of pulses produced by the transducer as the beam spot crosses track turns on the disk, the disk eccentricity check means being also connected to the speed command means for causing the disk to be read at the first predetermined speed if the eccentricity of the disk is found to be not more than a prescribed limit, and at the second predetermined speed if the eccentricity of the disk is found to be more than the prescribed limit;
(g) disk wobbling check means connected to the focusing servo for ascertaining the wobbling of the disk in terms of the magnitude of the focusing servo signal, the disk wobbling check means being also connected to the speed command means for causing the disk to be read at the first predetermined speed if the wobbling of the disk is found to be not more than a prescribed limit, and at the second predetermined speed if the wobbling of the disk is found to be more than the prescribed limit.

5 more elements

Dependencies are inferred from the claim text.

Method and apparatus for checking the quality of CD-ROMS or the like for reading them at matching speeds

Life of this patent

Method and apparatus for checking the quality of CD-ROMS or the like for reading them at matching speeds

Life of this patent

Abstract

Claims14