| 摘要 |
<p>In a focus servo apparatus for an optical type information read-out system having a light source, a condenser lens for focusing light from the light source on a recording surface of a recording medium and for focusing light reflected by the surface and containing the information recorded on the surface, a cylindrical lens for passing the reflected light, a light receiving element responsive to the reflected light from the cylindrical lens for providing an output and a driving device responsive to the output for regulating the position of the condenser lens relative to the surface, the cylindrical lens has its primary principal point substantially at the focusing point of the condenser lens for the reflected light and the physical axis of the cylindrical lens makes and angle of about 45.degree. with respect to the moving direction of the recording medium.</p> |
