| 摘要 |
In an optical encoder, in a case where a distance between the movable scale and a light beam emission plane of the surface emitting laser light source along a center axis of the light beam is L, a wavelength of the light beam is lambd, a scale pitch of the movable scale is p, an angle between a pitch direction of the movable scale and a plane perpendicular to the center axis of the light beam is theta, and an opening width of the surface emitting laser light source along a direction in which the pitch direction of the movable scale is projected on the plane perpendicular to the center axis of the light beam is a, a relationship, p.cos theta<a, is satisfied when L<=1.0a2/lambd.
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