Process for determining fluctuations in level in magnetizable layers

Claim 1

A process for determining fluctuations in level in magnetic recording materials which contain at least one magnetizable layer consisting of a nonmagnetic binder to which particles are applied by casting, which cast particles are subsequently magnetizable in a magnetic orientation so that variations in light-scattering capabilities are present in the surface structure of the layer, the improvement of projecting a beam of electromagnetic waves incident on the surface of the layer, said beam consisting of substantially parallel waves, producing scattered radiation of said incident beam from said surface, said scattered radiation being of varying intensity, receiving radiation from said surface in at least two detecting receivers along radiating beams of divergent angles to the axis of the incident beam, said reception in a first of said receivers being along a plane passing through the incident light beam and magnetic orientation of said particles when magnetized, said reception in a second of said receivers being along a plane passing through the incident light beam and the perpendicular to said magnetic orientation and measuring the intensity of the emitted scattered radiation.