Patent ID: 7471610

Claim:
An optical pickup for focusing first, second, and third light beams of wavelengths λ 1 , λ 2 , and λ 3 , which are related to one another by λ 1 <λ 2 <λ 3 , on information recording faces of first, second, and third recording media respectively having light transmissive layers, the light transmissive layers being formed on the information recording faces and respectively having thicknesses t 1 , t 2 , and t 3 , which are related to one another by t 1 =t 2 <t 3 , said optical pickup comprising: an objective lens for respectively focusing the first, second, and third light beams on the respective information recording faces of the first, second, and third recording media; and a diffraction optical element, provided on an incident side of the first, second, and third light beams and provided as an integral unit with the objective lens, for diffracting and refracting the first, second, and third light beams so as to cause the first, second, and third light beams to be incident on the objective lens as diffracted rays of predetermined diffraction orders, the diffraction optical element causing the third light beam to be focused on the objective lens as a diverging ray, and the diffraction optical element satisfying |Φin3|<|Φout3| where Φin3 is a degree of convergence or divergence of an incident ray of the third light beam on the diffraction optical element, and Φout3 is a degree of divergence of an incident ray of the third light beam on the objective lens.