Document Type and Number:
Japanese Patent JPS4824043
Kind Code:
B1
Abstract:
1,196,047. Optical playback of magnetic records. AMPEX CORP. 11 Oct., 1967 [12 Oct., 1966], No. 46438/67. Heading G5R. To reduce noise in optical playback of magnetic records, light reflected from, or transmitted through, the record is filtered to pass only that part of the light subtending a preselected solid angle. As shown, a playback system employing the Kerr-effect comprises a light source 14 (e.g. a laser), a polarizer 16 and lens 20 to focus the light on a magnetic recording medium 12. The reflected light consists of a narrow information band 19 and noise signals 21 which are more widespread due to surface imperfections of the medium and which may, therefore, be removed by a filter 24. The filter 24 may be placed before or after the objective lens 22 and may either consist of an adjustable iris or an aperture formed in a plate of opaque material. The method may be applied to systems employing the Faraday-effect. Equations are given by which the location and size of the filter may be determined according to the size of recorded information bits, the wavelength of the light and the focal length of the objective lens 22.
Application Number:
JP6521367A
Publication Date:
July 18, 1973
Filing Date:
October 12, 1967
Export Citation:
International Classes:
G11B11/10; G11B11/105; G11C13/06