Patent ID: 7606134

Claim:
An optical pickup for recording or reproducing information with respect to (a) a first recording medium having a light transmissive layer of a thickness t 1 on an information recording face and (b) a second recording medium having a light transmissive layer of a thickness t 2 greater than t 1 on an information recording face, the optical pickup recording or reproducing information with respect to the first recording medium by forming a first light spot on the information recording face of the first recording medium by focusing a first light beam of a wavelength λ 1 on the information recording face, and the optical pick up recording or reproducing information with respect to the second recording medium by forming a second light spot on the information recording face of the second recording medium by focusing a second light beam of a wavelength λ 2 greater than λ 1 on the information recording face, said optical pickup comprising: a diffraction optical element for diffracting and refracting incident rays of the first and second light beams so as to emit the first and second light beams, the diffraction optical element including a converging diffraction grating and a diverging lens; and an objective lens for causing respective diffracted rays of predetermined diffraction orders of the first and second light beams emitted from the diffraction optical element to focus on the respective information recording faces of the first and second recording media so as to form the first and second light spots, the first light beam and the second light beam being incident on the diffraction optical element as light beams with different degrees of convergence or divergence.