| 摘要 |
<p>VIDEO DISC PLAYBACK APPARATUS AND STYLUS THEREFOR A stylus support element of dielectric material (e.g., sapphire) has a tip formed with a tapering, flat rear face, having converging straight edges which terminate in a curved bottom edge. Sides of the support element tip extend in converging fashion toward a narrow stylus front, while a curved surface, extending forward from the bottom of the rear face with a gradually diminishing width, forms the bottom of the support element. The rear surface of the support element is coated with a thin layer of conductive material (e.g., hafnium) which forms a stylus electrode. Overlying the conductive layer is an additional layer of dielectric material (e.g., aluminum oxide) having a thickness which is large relative to the thickness of the conductive layer, but small relative to the length of the curved bottom of the stylus support element. In use of the stylus in video disc playback apparatus, the stylus tip is received in the groove of a disc having a conductive surface covered with a dielectric coating. As geometric variations of the groove bottom, representative of recorded picture and sound information, pass beneath the stylus, the capacitance between the stylus electrode and the disc's conductive layer varies. The capacitance variations are converted to electrical signal variations representative of the recorded information. Presence of the dielectric overcoating on the stylus electrode establishes a degree of symmetry for the stylus response, that eliminates or reduces spurious effects of sound interference with picture information that may be encountered in the absence of the overcoating use.</p> |
