Automatic focus servomechanism in optical information reading device
AssigneeUniversal Pioneer Corporation
InventorHitoshi Kanamaru
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Abstract
A focus servo apparatus for an optical information reading system is disclosed, which includes an optical system for a light from an information carrying surface of a recording medium composed of a condenser lens, a cylindrical lens and a light receiving element. A subsystem is employed for maintaining light illuminating focussed on the information carrying surface in response to an output of the light receiving element. The distance between the cylindrical lens and the light receiving element is larger than the focus distance of the lenticular lens.
Claims8
In a focus servo apparatus in which an information recording surface of a recording medium is illuminated with light from an illumination source and information recorded on the recording surface is read out by using light reflected from the recording surface, the improvement comprising;
- a condenser lens for condensing the light from the recording surface, a cylindrical lens for passing the condensed light, light receiving means having a light receiving surface positioned for receiving the light from said cylindrical lens, a distance D between said cylindrical lens and said light receiving means being larger than the focus distance F of said cylindrical lens, and means responsive to an output of said light receiving means moving said condenser lens for condensing the illumination light onto the recording surface of said recording medium.
Dependencies are inferred from the claim text.