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COMPACT DISC VIDEO DISCS
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Technical Examples
- A disc centering device includes a base plate, a chuck which is installed on the base plate, a hub unit which is detachably engaged to the chuck and in which a plurality of discs are stacked, disc pushers which are slidably provided outside the hub unit, and include corresponding plate springs which center the discs by pushing circumferences of the discs, supporting units which support the corresponding plate springs with respect to the disc pushers so as to reinforce a restoring force of the plate springs after a disc centering of the discs, and a driving unit which slides the disc pushers simultaneously. Accordingly, even though the disc centering is continuously performed, a centering value can be maintained within a desired range (deviation), and deformation of discs can be prevented.
- A disc storage unit includes a case, a tray supported by the case and configured to support an array of discs in respective parallel vertical planes across which respective coaxial axes of the discs pass horizontally. There is a disc-raising mechanism having a finger activatable to lift one of the discs from the tray within its respective plane to thereby render that disc non-coaxial with other discs that might be supported by the tray. The storage unit also includes an indexing mechanism that is configured to cause the disc-raising mechanism to raise others of the discs in a like manner. This enables labels of the raised discs to be viewed for selection by a user.
- A storage case (1) for a compact disc (2) comprises an outer shell (4) within which an inner carrier (5) for storing the compact disc (2) is slideable between an open and a closed position. The compact disc (2) is stored in a disc storing area (20) between a lower support plate (15) and an upper retaining member (19) of the inner carrier (5). Guide plates (25, 26) slideably guide the compact disc (2) into and out of the disc storing area (20). Resilient disc engaging clips (30) on a rear end wall (17) of the inner carrier (5) resiliently urges the compact disc (2) against corresponding abutment members (33) on the front end wall (16) for securing the compact disc (2) against sideward sliding from the disc storing area (20). The combination of the disc engaging clips (30) and the guide plates (25, 26) avoid the need for a central locating spigot for engaging a central opening of the compact disc (2).
- There is provided an objective lens for an optical pick-up which is used to record/reproduce data to/from at least three types of optical discs. Thicknesses t1, t2 and t3 of cover layers of first, second third optical discs are t1?0.6 mm, t2?0.6 mm, and t3?1.2 mm. Numerical apertures NA1, NA2 and NA3 for the first, second and third optical discs satisfy a relationship NA1?NA2>NA3. When the first optical disc is used, a substantially collimated light beam is incident on the objective lens. When the second or third optical disc is used, a diverging beam is incident on the objective lens. With regard to magnifications M1, M2 and M3 and focal lengths f1, f2 and f3 of the objective lens for the first, second and third optical discs, the following conditions (1), (2) and (3) are satisfied:
- The method and apparatus described utilise the fact that CDs manufactured from the same master will have distinctive physical characteristics attributable to the physical manufacturing process of the master to distinguish counterfeit CDs from genuine discs. For a genuine disc, the relative angular orientation of specified sections of the recorded data are determined and recorded. The relative angular orientation of the same sections of data on a test disc are also determined. Where the relative angular orientations are the same it is concluded that the test disc derives from the same source as the genuine disc and is therefore bona fide. Where there is no correlation, the test disc may be identified as counterfeit. The relative angular orientations, or other physical characteristics of the discs, may be physically measured, or may be calculated from information gained by reading the data on the disc. The disclosed technique can also be used to copy protect discs.
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