OBJECTIVE LENS FOR OPTICAL PICKUP DEVICE, AND OPTICAL PICKUP DEVICE

摘要

Provided is a objective lens for an optical pickup device, and optical pickup device which, by ensuring the function of comma aberration correction by objective lens tilt, is capable of performing comma aberration correction at the same time as contributing to the creation of thinner optical pickup devices. Defining M as the magnification and T as the optical disc substrate thickness, in combinations (M, T) in which third-order spherical aberration is minimized, if M=0, then T=Tcen (µm); or, defining LT as the value of third-order comma aberration relative to the objective lens tilt and DT as the value of third-order comma aberration relative to the optical disc tilt, the aforementioned combination (M, T) for which ||LT|-|DT|| is minimized is M=Mcmc and T=Tcmc(µm). By designing an objective lens in a state with a low design substrate thickness in order to fulfill formula (1), an objective lens can be provided that is optimal for thin optical pickup devices, but there is a reduction in objective lens tilt sensitivity. In response to this, by upsetting the sine condition in order to fulfill formula (2), if the objective lens tilt sensitivity increases, the comma aberration correction amount increases relative to the tilt amount of the objective lens, and by this means even poor quality optical discs can be supported. 0.5*T0 = Tcen = 0.85*T0 (1) Tcen<Tcmc (2), wherein TO is the greatest substrate thickness (µm) of the optical disc