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.

Abstract: A process for producing an azo pigment, which comprises coupling an aromatic diazonium compound with 3-hydroxy-2-naphthoic acid and at least one binaphthol and optionally, laking the resulting pigment.