Displacement information detector
AssigneeCanon Kabushiki Kaisha
InventorKo Ishizuka
Life of this patent
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Abstract
A displacement information detector in which a coherent luminous flux from a light source is applied to a diffraction grating scale adapted to be relatively moved to generate two diffracted rays of light having different orders, and the two diffracted rays of light are diffracted and deflected in a diffraction grating in which circular or toric curves are arranged in lattice at unequal pitches to be irradiated to the diffraction grating scale again to be rediffracted, and the diffracted rays of light are combined with each other to be made interfere each other, and the resultant interference light is introduced into a light receiving element to thereby detect a periodic signal due to the relative movement of the diffraction grating scale.
Claims4
A displacement information detector, comprising:
- a diffraction grating scale adapted to be relatively moved;
- illumination means for illuminating the diffraction grating scale with a coherent luminous flux;
- and
- a diffraction grating having circular or toric curves arranged at unequal pitches and arranged so as to diffract and deflect two diffracted rays of light having different orders generated from the diffraction grating scale and to reirradiate the diffraction grating scale.
Dependencies are inferred from the claim text.