High density magnetic recording apparatus including a hologram type magnetic head positioning system

A magnetic recording apparatus comprising:

• a magnetic head portion for recording information on a disc-shaped recording medium and reproducing recorded information from said recording medium;
• a light emitting portion for emitting light;
• a hologram portion for converting said light from said light emitting portion into positioning light for positioning said magnetic head portion and for radiating it onto said recording medium and for receiving the reflected light therefrom;
• a light receiving portion for receiving said reflected light through said hologram portion and outputting a received light intensity signal;
• a carriage having said magnetic head portion located thereon and arranged so as to be freely movable in a radial direction;
• and
• a control portion for driving said carriage in response to said received light intensity signal from said light receiving portion and being operable to position said magnetic head portion at a predetermined position;
• said hologram portion including a body member having first and second major surfaces;
• said body member of the hologram portion having a first thin film layer made of a predetermined metal or a composition thereof located on said first major surface and a first reflection surface made of metallic material located on said first thin film layer
• said hologram portion having a second thin film layer made of a predetermined metal or a composition thereof located on said second major surface and a second reflection surface made of metallic material located on said second thin film layer;
• and
• said body member of the hologram portion further including a light path for transmitting light therethrough in a zig-zag manner between said first and second reflection surfaces and a plurality of optical means located on said body member and in said light path for converting the light from said light emitting portion into said positioning light.