Scanning device including plastic high-numerical aperture objective

摘要

An optical scanning device for scanning an information layer ( 104 ) of an optical record carrier ( 102 ) includes a radiation source ( 110 ) for generating a radiation beam ( 108 ) and a high-NA objective system ( 118 ) for converging the radiation beam on the information layer. The objective system includes a first lens ( 116 ) and a second lens ( 117 ). The first lens and the second lens are made of plastic. The signs of the temperature-dependence of the spherical aberration of the first and second lens are different and the magnitudes of the temperature-dependence of the spherical aberration of the two lenses is substantially equal such that the temperature-dependence of the spherical aberration of the objective system as a whole is reduced to less than 30 mlambda OPDrms for a temperature change of 30 K.