Abstract: A disk-form magnetic recording medium having a minimized change in output on an output envelope is produced by a process which comprises coating a nonmagnetic substrate with a magnetic paint and applying a magnetic field for orientation to the magnetic paint in a yet unsolidified state on the substrate moved in a direction. The magnetic field for orientation is made stronger in a direction perpendicular to the moving direction of the coated substrate than in the moving direction. The directional change in magnetic field for orientation is provided, e.g., by a plurality of magnetic poles having different magnetic powers or disposed with increasing angular spacing in a direction leaving the moving direction of the substrate, or by an electromagnet supplied with a positionally varying current.

Abstract: An optical system for scanning a medium with a beam spot includes a light beam generator, a deflector for deflecting the light beam in a predetermined direction and in deflection plane, and an imaging optical system between the deflector and the medium for imaging the light beam from the deflector on the medium as a beam spot, the imaging optical system having at least one lens element mode of a moisture absorbing material. The lens element has a shape in which the dimension in a direction parallel to the deflection plane of the light beam is greater than the dimension in a direction perpendicular to the deflection plane of the light beam. A device mitigates any influence on the imaged condition of the light beam on the medium caused by the lens element being subjected to moisture.