| 摘要 |
<p>An optical system for locating the center of concentric spiral or circular information tracks on a videodisc detects the central maximum of the diffraction pattern resulting when the disc is illuminated by light from a point source. Because the central maximum coincides with an extended straight line connecting the point source and the center of the tracks, determination of the position of the central maximum permits the center of either opaque or transparent discs to be located accurately.</p> |
