The invention concerns an objective lens for use with a dual layer optical information carrier. Such a carrier as used in Blu-ray Disks (BD) has a first information layer at a depth D1 below a top surface of the carrier and a second information layer at a depth D2, greater than depth D1. In accordance with the invention the objective lens is designed to produce substantially equal amounts of higher order spherical wavefront aberration when scanning the first and second information layers by providing minimum spherical aberration for scanning at a depth Dopt which is located between an average layer depth Dav = ((D1+D2)/2) and a depth (D1+Dav)/2. More specifically, the optimum depth Dopt is typically smaller than 0.995 Dav and most preferably less than 0.99 Dav. |