OBJECTIVE OPTICAL ELEMENT FOR OPTICAL PICKUP DEVICE, OPTICAL PICKUP DEVICE AND METHOD FOR DESIGNING OBJECTIVE OPTICAL ELEMENT

摘要

An objective optical element for an optical pickup device which can record and/or reproduce information appropriately using a material of high refractive index. An optical pickup device and a method for designing the objective optical element are also provided. Assuming that the relation of expression (2) is satisfied when the number of apertures NA satisfies the expression (1), and the relation of expression (4) is satisfied when the number of apertures NA satisfies the expression (3) in an objective optical element, the focal length, the thickness on the axis and the working distance required for mounting an actual optical pickup device can be secured while improving the temperature characteristics. 0.80NA0.90 (1) 40,000β/γ50,000 (2) 0.60NA0.70 (3) 800β/γ1,600 (4)