Patent attributes
An optical pickup includes a light source emitting a light beam, an objective lens condensing the light beam emitted from the light source onto an optical disc, at least one divergent angle conversion lens (collimator lens) disposed between the light source and the objective lens and changing a divergent angle of the incident light beam, a driving unit (collimator lens driving mechanism) configured to drive the divergent angle conversion lens in a direction of an optical axis, an optical detection device (optical detector) detecting a return light beam reflected at the optical disc, and an environmental change detecting unit (temperature sensor) configured to detect change in environmental temperature, wherein the objective lens is made of a refractive element having, on one surface thereof, a diffraction structure in a stepped shape or a blazed sectional shape, which generates diffraction light providing a spot adapted to perform satisfactory recording and/or reproducing, the objective lens satisfying certain relationships among an amount of wavefront aberration thereof corresponding to change in environmental temperature, an amount of the change in environmental temperature, and a focal length.
