| 摘要 |
A high-density information record comprises a stamped thermoplastic (e.g., vinyl) disc having a constant-width spiral surface groove, the center-to-center spacing of successive closely spaced convolutions of the groove spiral being substantially constant and independent of the recorded information. The recorded information appears as an information track constituting variations in the geometry of the groove bottom along its length. Playback apparatus employs a stylus having a tip conformed to be received in the disc groove in engagement with smoothly curved side walls of groove. As a disc-supporting turntable rotates, the stylus rides in the groove passing over successive dimension-varying information track elements in the groove bottom, which serve to vary the capacitance presented between a conductive electrode incorporated in the stylus tip and a reference conductor (e.g., a conductive surface of the disc-supporting turntable). The capacitance variations occurring during playback are translated into electrical signal variations by appropriate circuitry. Per illustrative embodiment, inexpensively replicated video disc of appreciable playing time is subject to playback by above-described techniques. |
