Optical head device, optical information recording/reproducing apparatus and operation method of optical information recording/reproducing apparatus

An optical information recording/reproducing apparatus comprising:

• an optical head device;
• and
• a calculating circuit,
• wherein said optical head device comprises:
• an objective lens configured to condense an emitted light from a light source onto an optical recording medium;
• a diffractive optical element configured to separate a incident light into a plurality of light beams;
• and
• a photo detector,
• said emitted light is reflected by said optical recording medium and incidents as said incident light through said objective lens into said diffractive optical element,
• said plurality of light beams includes a first light beam group which is generated from an entire region in a section of said incident light and a second light beam group which is generated from at least a partial region in said section,
• said photo detector is configured to receive said first light beam group and said second light beam group by different light receiving portions for detecting a focus error signal used for focus servo and a protective-layer-thickness-deviation signal indicating a protective-layer-thickness deviation of said optical recording medium, and
• said calculating circuit is configured to detect said focus error signal and said protective-layer-thickness-deviation signal based on output signals from said different light receiving portions.

An operating method of optical information recording/reproducing apparatus, comprising:

• providing an optical information recording/reproducing apparatus which includes an optical head device, a calculating circuit, a compensating section and a driving circuit, wherein said optical head device includes a light source, an objective lens, a diffractive optical element and a photo detector;
• said objective lens condensing an emitted light from said light source onto an optical recording medium;
• said diffractive optical element separating a incident light into a plurality of light beams, wherein said emitted light is reflected by said optical recording medium and incidents as said incident light through said objective lens into said diffractive optical element, and said plurality of light beams includes a first light beam group generated from an entire region in a section of said incident light and a second light beam group generated from at least a partial region in said section;
• different light receiving portions of said photo detector receiving said first light beam group and said second light beam group;
• said calculating circuit detecting a focus error signal used for a focus servo and a protective-layer-thickness-deviation signal based on output signals from said different light receiving portions;
• said driving circuit outputting a drive signal based on said protective-layer-thickness-deviation signal;
• and
• said compensating section compensating a protective-layer-thickness deviation of said optical recording medium based on said drive signal.