U.S. Philips Corporation

Fredericus G Homburg

Bernardus Johannes Stinesen

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 (t.sub.2 -t.sub.1) 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.

System comprising optical discs and a scanning device

A scanning device comprises a lens (2) having an optical axis (2a). The lens is movable in a focussing direction (F) to form at least one radiation spot on a surface to be scanned and in a tracking direction (T) oriented transversely of the focussing direction, in order to follow a recording track. The scanning device comprises a stationary section (16) with a magnetic circuit and one air gap (20), and a section (6) which includes the lens and is movable relative to the stationary section. The movable section comprises at least one focussing coil (12) and two tracking coils (14a, 14b) for driving the lens, the focussing coil having a coil axis (12a) extending parallel to the optical axis. The air gap is situated between the optical axis of the lens and the coil axis of the focussing coil. The movable section is secured to the stationary section by a compliant mechanical suspension (22a, 22b), and its mass center is situated in or at least near the air gap.

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Eindhoven, Netherlands

Fredericus G Homburg