Patent ID: 8514674
Filing Date: 2013-08-20
Classification: G11B

Abstract:
1. An optical information recording medium reproducing apparatus, comprising: an optical system including (i) a laser light source for emitting laser light having a wavelength of λ nm and (ii) an objective lens having a numerical aperture NA, said optical information recording medium reproducing apparatus emitting the laser light to an optical information recording medium, in which marks and spaces formed between any adjacent ones of the marks are recorded as information, so as to reproduce the information recorded and acquire reproduction signal data, said optical information recording medium reproducing apparatus being capable of reproducing the optical information recording medium including marks each having a mark length shorter than λ/4NA, said optical information recording medium reproducing apparatus, further comprising: a signal extracting section for detecting a predetermined data pattern from the reproduction signal data, and for extracting, as extracted reproduction signal data, part of the reproduction signal data which part corresponds to the predetermined data pattern detected; a reproducing power control value finding section for finding, from the extracted reproduction signal data extracted by the signal extracting section, a reproducing power control value for controlling a reproducing power of the laser light; and a reproducing power control section for controlling the reproducing power of the laser light, in accordance with a comparison between the reproducing power control value and a predetermined reference value or a reference value which is determined by test reading of the optical information recording medium, the predetermined data pattern being a data pattern which is defined by (i) a space which has a space length shorter than λ/4NA and is sandwiched between marks so as to be adjacent to the marks, the marks each having a mark length of λ/2NA or longer and/or (ii) a mark which has a mark length shorter than λ/4NA and is sandwiched between spaces so as to be adjacent to the spaces, the spaces each having a space length of λ/2NA or longer.