| 摘要 |
According to one embodiment, this invention determines whether a maximum value Hmax and minimum value Hmin of an HF signal obtained when a data recording portion is irradiated with a laser having a wavelength of 450 nm or less and an NA of 0.6 or more meet (Hmax−Hmin)/Hmax<0.13 . . . (1), or whether a maximum value Hmax, a minimum value Hmin, and a most frequent voltage value Have of a signal level of an HF signal obtained when a data recording portion is irradiated with a laser having a wavelength of 450 nm or less and an NA of 0.6 or more meet Hmax/Have≦̸1.05 . . . (2) and Hmin/Have≦̸0.90 . . . (3).
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