Optical pickup device, optical recording and reproducing apparatus and gap detection method

An optical pickup device comprising:

• a light source configured to generate a plurality of light beams, said plurality of light beams including a first light beam and a second light beam;
• a head unit including first and second lenses, said second lens being located in an opposing relation to an optical recording medium and being configured to converge said plurality of light beams emitted from said light source to generate near field light toward said optical recording medium;
• and
• a photo-detecting unit configured to detect a plurality of quantities of returned light respectively of said plurality of light beams returned from said head unit so as to detect a tilt angle of said head unit relative to a recording surface of said optical recording medium based on a difference between two quantities of returned light from among said plurality of quantities of returned light, said two quantities of returned light being quantities of returned light respectively of said first light beam and said second light beam that are returned from said head unit, wherein said head unit generates near field light by said second lens at its end face opposing said optical recording medium and reflects said plurality of light beams introduced from said light source at said end face.

An optical recording and reproducing apparatus for recording and/or reproducing an optical recording medium by irradiating said optical recording medium with light from a light source, comprising:

• a light source configured to generate a plurality of light beams, said plurality of light beams including a first light beam and a second light beam;
• a head unit located in an opposing relation to said optical recording medium and configured to irradiate said plurality of light beams emitted from said light source on said optical recording medium as near field light so as to form a plurality of light beam spots on said optical recording medium;
• and
• a photo-detecting unit configured to detect a plurality of quantities of returned light respectively of said plurality of light beams returned from said head unit so as to detect a gap between said head unit and a recording surface of said optical recording medium based on at least one of said plurality of quantities of returned light, and so as to detect a tilt angle of said head unit relative to said recording surface of said optical recording medium based on a difference between two quantities of returned light from among said plurality of quantities of returned light, said two quantities of returned light being quantities of returned light respectively of said first light beam and said second light beam that are returned from said head unit,
• wherein said head unit includes a first lens and a second lens located between said first lens and said optical recording medium, and wherein said second lens is configured to generate near field light.

A detection method comprising the steps of:

• emitting a plurality of light beams from a light source to a head unit, said plurality of light beams including a first light beam and a second light beam;
• irradiating the plurality of light beams on an optical recording medium though said head unit so as to generate a plurality of near field lights;
• detecting a plurality of quantities of returned light respectively of said plurality of light beams returned from said head unit;
• and
• detecting a tilt angle between a recording surface of said optical recording medium and said head unit based on a difference between two quantities of returned light from among said plurality of quantities of returned light, said two quantities of returned light being quantities of returned light respectively of said first light beam and said second light beam that are returned from said head unit.