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US 8,710,425 B2Granted
Encoder that optically detects positional information of a moving body from different optical paths lengths
AssigneeNikon Corporation
InventorsSusumu Makinouchi, Akihiro Watanabe
Life of this patent
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Abstract
An encoder emits modulated light from a light source section and lets a first light and a second light separated from the modulated light interfere with each other in a moving grating. In the encoder, the light emitted from the light source section is electrically modulated, and the first light and the second light have different light path lengths.
Claims15
An encoder comprising:
- a light source section which emits a light, a wavelength of which periodically changes, in a parallel fashion;
- a first optical member which receives the light emitted from the light source section and then emits a first light and a second light, the first optical member emitting the first light and the second light from different positions;
- a second optical member which changes a travelling direction of the first light or the second light such that the first and second lights emitted from the first optical member overlap each other;
- a diffraction grating member which is disposed at a position where the first light and the second light overlap each other, is displaced relatively with respect to the light source section, the first optical member, and the second optical member, and has a diffraction grating periodically formed along a movement direction by the displacement;
- a first light receiving section which receives an interfering light of the first and second lights, which is emitted from the diffraction grating member, and detects an interference intensity of the interfering light,
- wherein an optical path length of a first optical path of the first light from the light source section to the diffraction grating member and an optical path length of a second optical path of the second light from the light source section to the diffraction grating member are different from each other, and
- the encoder further comprising a transmissive member which is disposed between the light source section and the first optical member in either the first optical path or the second optical path and has a predetermined refractive index.
4 more elements
An encoder comprising:
- a light source section which includes a modulating device and emits a light, a wavelength of which periodically changes;
- an index grating, into which the light from the light source section enters and from which a first diffracted light and a second diffracted light are emitted, the index grating emitting the first diffracted light and the second diffracted light from different positions;
- a transmissive member which is disposed between the light source section and the index grating in either a first optical path or a second optical path and has a predetermined refractive index;
- a moving grating, into which the first diffracted light and the second diffracted light enter and which can be displaced relatively with respect to the index grating;
- and
- a light beam receiving section which detects interfering light of the first and second diffracted lights, that is emitted from the moving grating, wherein
- an optical distance from the light source section to the moving grating is substantially different between the first diffracted light and the second diffracted light.
4 more elements
An encoder comprising:
- a light source section which emits a light, a wavelength of which periodically changes;
- an optical member that is configured to separate the light emitted from the light source section into a first light and a second light;
- a moving member that is arranged to relatively move with respect to the light source section, the moving member having a diffraction grating into which the first light and the second light enter and from which a first interfering light of the first light and the second light is emitted:
- and
- a first light receiving section which receives the first interfering light, wherein
- the first light has a first optical path length and the second light has a second optical path length different from the first optical path length such that there is an optical path length difference between the first light and the second light, and
- a phase difference between the first light and the second light is determined by the optical path length difference between the first light and the second light and the changes of the wavelength.
4 more elements
Dependencies are inferred from the claim text.