Patent ID: 7933179

Claim:
An optical information reproducing method for irradiating light to an optical information recording medium and thus reproducing information from the optical information recording medium, the method comprising: in the case where the optical information recording medium contains a material, an optical characteristic of which changes with irradiated light and returns to an optical characteristic before the light irradiation when the irradiated light power is reduced, a step of performing a focusing servo function and thus causing a light spot to track a recording surface of the optical information recording medium; and a step of detecting a detection signal including reflected light of the irradiation light as a cross track signal with a photo detector, without performing a tracking servo function, and extracting a change-point of an upper envelope of the cross track signal and a change-point of a lower envelope of the cross track signal, and determining an optimum reproduction power by varying reproduction power between the change-point of the upper envelope and the change-point of the lower envelope.