System comprising optical discs and scanning device

A system includes optical discs of a first type and optical discs of a second type having a transparent substrate with a thickness greater than that of the transparent substrate of the optical discs of the first type. The system further comprises a scanning device which is capable of scanning optical discs of both types and which comprises an actuator and an objective for focusing a radiation beam passing through the substrate of an optical disc so as to form a scanning spot (S) on an information surface. The actuator comprises a first actuator section and a second actuator section including the objective, which second actuator section is movable relative to the first actuator section. The system further comprises compensation means for compensating for the difference in thickness (t2-t1) between substrates of optical discs of said types, so that both during scanning of an optical disc of the first type and during scanning of an optical disc of the second type the second actuator section is movable starting from the same reference position for the purpose of focusing.