Importance

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Abstract

Video information is commonly recorded on a master record device such as a video disc by focussing a modulated recording beam on the master disc and rotating the disc relative to the focussed recording beam. During exposure, the recording beam travels across the rotating master disc so that a spiral track of video information is recorded. Because of the extremely small depth of focus, typically less than a micron, focus maintenance is simplified if the master disc recording surface is optically flat. This requirement has led to the use of a relatively expensive master video disc comprised of optically polished glass, quartz or other rigid material. In accordance with the present invention, a method of recording video information on a master disc is provided which permits the use of an inexpensive flexible master disc comprised of ESTAR or other similar material, and yet which enables an extremely small depth of focus to be accurately maintained.

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First Claim