| 摘要 |
In an optical disc player or other apparatus in which a light beam is directed through an objective lens to be focused thereby at a record medium surface for optically reading information recorded in a track on such surface; the objective lens is mounted eccentrically in a circular end wall of a body member having a cylindrical side wall depending from the periphery of the end wall, a bearing sleeve extends axially from the center of the end wall and is slidable on a shaft extending upwardly from a base member so that the body member is both angularly displaceable about the shaft axis and axially displaceable relative to the base member to correct for tracking and focusing errors, respectively, inner and outer yokes extend upwardly from the base member at the inside and outside, respectively, of the cylindrical side wall and have respective radially aligned gaps, a magnet is associated with the yokes for generating magnetic flux through the side wall of the body member between the inner and outer yokes, and tracking and focusing coils are provided on the cylindrical side wall of the body member, with the tracking coils being shaped to have first and second portions extending parallel to the shaft axis and through which current will flow in opposed directions in response to the supplying of a tracking error signal to the tracking coils, with each first tracking coil portion being located between the inner and outer yokes to interact with the magnetic flux and thereby effect angular or rotary displacement of the body member in response to tracking error signals and each second tracking coil portion being located proximate to gaps of said inner and outer yokes so as to be substantially free of the magnetic flux, and with the path of a light beam through the objective lens being arranged to pass through a gap of the inner yoke and between the bearing sleeve and the cylindrical side wall of the body member.
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