Substrate crack method of detection and substrate crack detection device null of information record media of disk

摘要

PROBLEM TO BE SOLVED: To detect a crack of a substrate of a disc-like data-recording medium at high speed by shedding light on the crack of the substrate and detecting a reflecting light. ;SOLUTION: A data-recording medium 4 is loaded in such a manner that a center hole 11 is fitted with a projecting part 1a of a spindle 1. An inner peripheral transparent part of the medium 4 is vacuum-chucked. A spindle motor 5 rotates a spindle 1 and the medium 4. A semiconductor laser 2a is driven by a laser-driving source 21 to emit a laser light L to a crack of a substrate at the innermost peripheral part of the medium 4 with an angle of approximately 90°. If a crack 12 is present, the laser light L enters a horizontal plane of the medium 4 with an angle of approximately 40°, is reflected at the crack, and returns to a photodetector 2b. The light is detected there and a detection signal is brought into a crack judgment part 7 through an amplifier 3, whereby the presence of the crack is determined. If the crack 12 does not exist, the laser light L is not returned to the photodetector 2b. It is thus detected that the crack 12 is not present.;COPYRIGHT: (C)1997,JPO