OBJECTIVE LENS AND SCANNING DEVICE USING SUCH AN OBJECTIVE LENS

摘要

A scanning device for optical record carriers is provided with an objective lens (7) suitable for scanning record carriers (1, 21) having a transparent substrate (2, 23) of different thicknesses. The lens comprises an outer annular part (25) and an inner central part (26) within the annular part. Only the central part of the lens is used for forming a focus through a first substrate (2) having a first thickness. The central part is corrected for the spherical aberration of the first substrate. The annular and central part of the lens are used for forming a focus through a second substrate (23) having a different, second thickness. The annular part is corrected for the spherical aberration of the second substrate.