Patent ID: 7668056

Claim:
A warpage angle measurement method comprising: accommodating at least one of an optical disc and a cartridge for the optical disc as an object to be measured in a first constant temperature chamber; adjusting an inside of the first constant temperature chamber to have a predetermined environmental condition including at least one of a temperature and a humidity; preparing a second constant temperature chamber, wherein the environmental conditions inside the first constant temperature chamber and the second constant temperature chamber are adjusted to have a different environmental condition from each other, and the object to be measured is first accommodated in the first constant temperature chamber and then carried into the second constant temperature chamber; and thereafter, measuring an angle of warpage of the object to be measured by emitting laser light to the object to be measured, receiving the laser light reflected from the object to be measured, and detecting a relative angle of an optical path of the reflected laser light with respect to an optical path of the emitted laser light.