Spherical Aberration Error Detection for Blu-ray Disc Optical Pickups

Abstract

For a high-numerical-aperture (NA) optical pickup system, the spherical aberration (SA) caused by cover layer thickness error should be corrected. We detected the SA error signal using a newly designed hologram optical element (HOE). The HOE has both sufficient signal sensitivity and constant signal level independent of objective lens shift. In addition, we fabricated on SA servo for a dual-layer Blu-ray disc.

Fast adjustment method of spherical aberration and focus offset by elliptic equation

“…In order to make the light spot size small, it is necessary to increase a numerical aperture (NA) of an objective lens, but this leads to increase of spherical aberration [1,2]. The spherical aberration is proportional to the fourth power of NA of the objective lens [3].…”