Patent ID: 8456979

Claim:
An optical information recording/reproducing apparatus for recording information to and/or reproducing information from an optical disc based on a predetermined standard by using a light beam having a wavelength of λ (unit: nm), the optical information recording/reproducing apparatus comprising: a biconvex objective lens that converges the light beam onto a recording surface of the optical disc and satisfies a condition: 0.48 < d · ( n - 1 ) f 2 < 0.75 ( 1 ) where f represents a focal length (unit: mm) of the objective lens with respect to the wavelength λ, d represents a thickness (unit: mm) of the objective lens along an optical axis of the objective lens, and n represents a refractive index with respect to the wavelength λ; a photoreceptor that receives the light beam reflected from the recording surface of the optical disc; a detector that detects quality of a signal outputted by the photoreceptor based on the light beam reflected from the recording surface of the optical disc; and an objective lens driving unit configured to tilt the objective lens in a direction to improve the quality of the signal based on a result of detection by the detector, wherein the objective lens is configured such that an offence against a sine condition takes a local minimum value within a range larger than or equal to 20% and smaller than 80% of an effective beam radius with respect to the optical axis, the offence against the sine condition takes a maximum value within a range of 80% to 100% of the effective beam radius, and the maximum value of the offence against the sine condition falls within a range of 0.001 to 0.01.