| 摘要 |
PROBLEM TO BE SOLVED: To attain high resolution when a light source and a scale are arranged so as to be relatively close in an optical encoder using a face emission laser. SOLUTION: In an optical encoder, a distance between a moving scale 20 on the central axis of a light beam and the light beam outgoing face of a face emission laser light source 10 is defined as L, the wavelength of the light beam is defined as 2, the scale pitch of the moving scale 20 is defined as (p), and the opening length of the face emission laser light source along a direction in which the pitch direction of the moving scale is projected to a face vertical to the central axis of the light beam is defined as (a). When L<=1.0a<2> /λ, a relation that p/cosθ<a is fulfilled.
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