An optical scanning device is adapted for scanning a record carrier having an outer face. The optical scanning device comprises a radiation source for generating a radiation beam, and an objective system having an exit face arranged for evanescent coupling of the radiation beam between the exit face and the outer face and for converging the radiation beam to a focus. A gap servo maintains a distance between the exit face and the outer face at a predetermined gap height. The optical scanning device includes a control unit for setting the predetermined gap height at at least two different values.