Playback device and playback method

A playback method for a playback device in which light emitted by a light source is radiated onto an optical recording medium via an objective lens, and reflected light obtained from a recording surface of the optical recording medium in accordance with the radiated light is condensed by a condenser lens and detected by a photodetecting section, the playback method comprising:

• imparting, on a light path from the light source to the photodetecting section, a designated phase difference between a reflected light component from a readout track and a reflected light component from a track neighboring the readout track from among tracks formed on the recording surface of the optical recording medium;
• and
• provided that a confocal position is a focal position of the condenser lens when light emitted by the light source is focused onto the recording surface by the objective lens, λ is a wavelength of light radiated onto the optical recording medium by the objective lens, and NA is a numerical aperture of the objective lens, extracting and detecting light within a range of a diameter less than 1.5λ/NA centered on an optical axis at the confocal position, the light being central light of the reflected light at the confocal position,
• wherein the central light of the reflected light is extracted with a pinhole disposed at the confocal position.

A playback device comprising:

• a light source;
• an objective lens that radiates light emitted by the light source onto an optical recording medium, and onto which is incident reflected light obtained from a recording surface of the optical recording medium in accordance with the radiated light;
• a condenser lens, onto which is incident the reflected light obtained via the objective lens, that condenses the reflected light;
• a photodetecting section configured in a manner that, provided that a confocal position is a focal position of the condenser lens when the light emitted by the light source is focused onto the recording surface by the objective lens, λ is a wavelength of light radiated onto the optical recording medium by the objective lens, and NA is a numerical aperture of the objective lens, the photodetecting section extracts and detects light within a range of a diameter less than 1.5λ/NA centered on an optical axis at the confocal position, the light being central light of the reflected light at the confocal position;
• and
• a phase difference imparting section, inserted on a light path from the light source to the photodetecting section, that imparts a designated phase difference between a reflected light component from a readout track and a reflected light component from a track neighboring the readout track from among tracks formed on the recording surface of the optical recording medium, wherein
• provided that a groove with a depth less than λ/6 is formed on the recording surface, and a recording mark sequence is formed on both the groove and a land disposed between the groove, and in addition,
• provided that an outward path is a light path from being emitted by the light source to being radiated onto the optical recording medium, and a return path is a light path from being reflected off the optical recording medium to being detected by the photodetecting section, the phase difference imparting section is inserted at a position that imparts a phase difference to light on only one of the outward path and the return path, wherein
• the phase difference imparting section is configured to be capable of varying a phase difference imparted between a reflected light component from the groove and a reflected light component from the land, and
• the phase difference imparting section is equipped with a controller that controls the phase difference imparting section in a manner that the phase difference imparted between the reflected light component from the groove and the reflected light component from the land is varied between when reading out the groove and when reading out the land.

A playback device comprising:

• a light source;
• an objective lens that radiates light emitted by the light source onto an optical recording medium, and onto which is incident reflected light obtained from a recording surface of the optical recording medium in accordance with the radiated light;
• a condenser lens, onto which is incident the reflected light obtained via the objective lens, that condenses the reflected light;
• a photodetecting section configured in a manner that, provided that a confocal position is a focal position of the condenser lens when the light emitted by the light source is focused onto the recording surface by the objective lens, λ is a wavelength of light radiated onto the optical recording medium by the objective lens, and NA is a numerical aperture of the objective lens, the photodetecting section extracts and detects light within a range of a diameter less than 1.5λ/NA centered on an optical axis at the confocal position, the light being central light of the reflected light at the confocal position;
• and
• a phase difference imparting section, inserted on a light path from the light source to the photodetecting section, that imparts a designated phase difference between a reflected light component from a readout track and a reflected light component from a track neighboring the readout track from among tracks formed on the recording surface of the optical recording medium, wherein, in the optical recording medium,
• a recording mark sequence is formed in a concentric circular shape or a spiral shape on a same flat surface on the recording surface, and
• provided that an outward path is a light path from being emitted by the light source to being radiated onto the optical recording medium, and a return path is a light path from being reflected off the optical recording medium to being detected by the photodetecting section, the phase difference imparting section is inserted at a position that imparts a phase difference to light on both of the outward path and the return path.