| 摘要 |
A focus actuator for controlling the focal position of an objective lens used in an optical recording system to maintain a write/read laser beam in focus on a moving optical recording element. In a preferred embodiment, such actuator comprises a pair of juxtaposed coils which concentrically surround a ferromagnetic cylindrical member of low coercivity (e.g. soft iron). The cylindrical member, in turn, is concentrically arranged with respect to the objective lens and is rigidly coupled thereto. When current is applied to one coil or the other, the cylindrical member (and its coupled lens) move along the optical axis of the lens, in one direction or the other, depending on which of the coils is receiving current. Preferably, the cylindrical member is supported for movenent within the coils by a pair of flexure blades. A particularly important advantage over similar devices of the prior art is that the focus actuator of the invention requires no permanent magnet.
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