Optical Disc Alignment Tool
Original Publication Date: 1988-May-01
Included in the Prior Art Database: 2005-Feb-15
In order for servo mechanism tracking grooves on optical discs to work effectively, it is necessary for the grooves to be aligned accurately to the center of rotation. At present, this is done by using the center hole of the disc as a mechanical locator, on a boss, when printing the grooves, and later using a similar method to locate the disc to the hub. Hence, the hub-to-groove concentricity is a second-order mechanical location with which it is difficult to achieve accuracy to better than 10 microns. Proposed is an alignment system in which the grooves are printed reasonably accurately onto the disk (as at present) but the final alignment of the hub to the grooves (not the disk) is done optically, a method capable of much greater accuracy, and suitable for automated manufacturing.