Notes on some physical and optical characteristics of the stylus-on-celluloid method of recording

Abstract

It is shown that the stylus-on-celluloid record consists of a cylindrical depression forming a minute cylindrical lens, bordered by ridges forming quasi-cylindrical lenses of positive form and beyond these concave cylinders. When viewed with a properly focussed microscope, the record appears as a dark band on a bright ground and at the centre of the dark band is a fine bright line on which precise measurements can be made. The record is not made by scratching but by plastic deformation.