Optical pick-up apparatus with diffractive optical element and optical recording/reproducing apparatus having the same

An optical pick-up apparatus for reproducing information recorded on an optical recording medium or recording information on the optical recording medium comprising:

• a light source unit generating beams;
• a diffraction element which diffracts beams which are generated from the light source unit;
• and
• an objective lens which focuses a p order diffracted beam which is used for recording and reproducing information among a plurality of diffracted beams which are diffracted by the diffraction element on any one of a plurality of information recording layers which are formed on the optical recording medium,
• wherein a p±1 order diffracted beam which is not used for recording and reproducing information is focused on a point that is away from the plurality of information recording layers and a surface of the optical recording medium, and wherein the optical recording medium includes a dual layer blu-ray disc, and
• a difference (fp−1−fp) between a focal point (fp−1) of the p−1 order diffracted beam and a focal point (fp) of the p order diffracted beam and a difference (fp+1−fp) between focal point (fp+1) of the p+1 order diffracted beam and the focal point (fp) of the p order diffracted beam satisfy following the following conditional equations:
• −60 μm≦fp−1−fp≦−40 μm
• 65 μm≦fp+1−fp≦85 μm

An optical pick-up apparatus which records and/or reproduces information on/from an optical recording medium, the optical pick-up apparatus comprising:

• a light source unit which generates beams;
• a diffraction element which diffracts the generated beams;
• and
• an objective lens which focuses a p order diffracted beam on a layer of the optical recording medium for recording and/or reproducing information and focuses a p±1 order diffracted beam on layers other than the layer of the optical recording medium for recording and/or reproducing information,
• wherein a difference (fp−1−fp) between a focal point (fp−1) of the p−1 order diffracted beam and a focal point (fp) of the p order diffracted beam, and a difference (fp+1−fp) between a focal point (fp+1) of the p+1 order diffracted beam and the focal point (fp) of the p order diffracted beam satisfy the following conditional equations:
• −Dmax−WD≦fp−1−fp≦−Dmax−s×t
• 2×Dmax−Dmin+s×t≦fp+1−fp≦600 μm, wherein Dmax represents a distance from the surface of the optical recording medium to a deepest information recording layer of the optical recording medium, Dmin represents a distance from the surface of the optical recording medium to a shallowest information layer of the optical recording medium, WD represents a working distance of the objective lens, t represents an absolute value of manufacturing tolerance of the optical recording medium, and s represents a safety factor.

An optical pick-up apparatus which records and/or reproduces information on/from an optical recording medium, the optical pick-up apparatus comprising;

• a light source unit which generates beams;
• a diffraction element which diffracts the generated beams;
• and
• an objective lens which focuses a p order diffracted beam on a layer of the optical recording medium for recording and/or reproducing information and focuses a p±1 order diffracted beam on layers other than the layer of the optical recording medium for recording and/or reproducing information, wherein the optical recording medium includes a dual layer blu-ray disc, and
• a difference (fp−1−fp) between a focal point (fp−1) of the p−1 order diffracted beam and a focal point (fp) of the p order diffracted beam and a difference (fp+1−fp) between focal point (fp+1) of the p+1 order diffracted beam and the focal point (fp) of the p order diffracted beam satisfy following the following conditional equations:
• −60 μm≦fp−1−fp≦−40 μm
• 65 μm≦fp+1−fp≦82 μm.

An apparatus used in a device which records and/or reproduces information on/from an optical recording medium, the apparatus comprising:

• a diffraction element which diffracts beams generated by a light source;
• and
• an objective lens which focuses a p order diffracted beam on a layer of the optical recording medium for recording and/or reproducing information and focuses a p±1 order diffracted beam on layers other than the layer of the optical recording medium for recording and/or reproducing information,
• wherein a difference (fp−1−fp) between a focal point (fp−1) of the p−1 order diffracted beam and a focal point (fp) of the p order diffracted beam, and a difference (fp+1−fp) between a focal point (fp+1) of the p+1 order diffracted beam and the focal point (fp) of the p order diffracted beam satisfy the following conditional equations:
• −Dmax−WD≦fp−1−fp≦−Dmax−s×t
• 2×Dmax−Dmin+s×t≦fp+1−fp≦600 μm, wherein Dmax represents a distance from the surface of the optical recording medium to a deepest information recording layer of the optical recording medium. Dmin represents a distance from the surface of the optical recording medium to a shallowest information layer of the optical recording medium. WD represents a working distance of the objective lens, t represents an absolute value of manufacturing tolerance of the optical recording medium, and s represents a safety factor.