Code wheel for reflective optical rotary encoders
AssigneeAlps Electric Co., Ltd.
InventorsYoshihiro Takahashi, Hiraku Abe, Yasuhiro Mamiya
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Abstract
A code wheel for use in a reflective optical rotary encoder includes a code wheel body formed of a light-reflective material, and a photosensitive layer directly coated on a flat surface of the code wheel body and exposed to light to produce angularly spaced non-reflecting surfaces, thereby providing alternate reflecting and non-reflecting surfaces on the code wheel body. The speed and direction of rotation of the code wheel can be detected by radiating light onto the reflecting and non-reflecting surfaces and detecting light reflected by the reflecting surfaces.
Claims6
In a reflective optical rotary encoder of the type having a code wheel with a surface provided with alternating reflective and non-reflective sectorial areas spaced at predetermined angular intervals, and a photodetector for radiating light onto said areas and detecting light reflected from the reflective areas, whereby the speed and direction of rotation of the code wheel can be determined,
- the improvement wherein a code wheel body of said code wheel including said surface is formed of a light-reflective material and has directly coated on said surface a non-reflective photosensitive layer having alternating sectorial areas etched away by exposure to light to expose said light-reflecting surface beneath, so as to provide said alternating reflective and non-reflective sectorial areas.
In a method of making a reflective optical rotary encoder of the type having a code wheel with a surface provided with alternating reflective and non-reflective sectorial areas spaced at predetermined angular intervals, and a photodetector for radiating light onto said areas and detecting light reflected from the reflective areas, whereby the speed and direction of rotation of the code wheel can be determined,
- the improvement comprising the steps of:
- forming a code wheel body of said code wheel including said surface of a light-reflective material;
- directly coating on said surface a non-reflective photosensitive layer;
- and
- etching away alternating sectorial areas of said photosensitive layer by exposure to light through a mask to expose said light-reflecting surface beneath, thereby providing said alternating reflective and non-reflective sectorial areas.
Dependencies are inferred from the claim text.