Disc record with tapered groove
US4525751A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 27, 1982 |
| Grant date | Jun 25, 1985 |
| Priority date | — |
| Expiry date | Aug 27, 2002 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/903
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A video disc record of the constant angular velocity type (CAV) includes a spiral groove of constant pitch formed in a band on a surface thereof. The groove has a substantially constant nominal vertical dimension and vertical displacements which taper monotonically from an outer radius of the band to an inner radius. One component of the vertical displacement of the groove conveys an FM carrier wave of constant amplitude and relatively high frequency representative of picture information. A second component of the vertical displacement conveys one or more lower frequency FM carrier waves representative of sound information. The amplitude of the second component varies monotonically as a function of the groove radius within the record band to provide a disc having an improved audio FM carrier-to-noise ratio with no substantial perceptible increase in undesirable sound beat effects in images displayed when the disc is played. A mastering system exemplary of the method of forming the grooved disc includes variable gain units in an audio FM carrier wave processing path of the system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.