Encoder
First Claim
1. An encoder comprising:
- a scale having a plurality of pattern areas having a plurality of patterns arranged in a measurement direction with an equal predetermined pitch and including at least one pattern area disposed with an offset, in the measurement direction, from a neighboring pattern area by 1/(2×
s) of the predetermined pitch (wherein “
s”
is an integer of 1 or greater), the plurality of patterns comprising at least first and second patterns, each of which comprises a plurality of spaced pattern elements, that are linearly arranged in the measurement direction;
a detection head configured to be relatively movable in the measurement direction with respect to the scale, and detect interference fringes caused by positive s-th-order diffracted beams and negative s-th-order diffracted beams diffracted by the scale, and output a detection result; and
a signal processor configured to detect a reference position based on a position where light intensity is lower than a predetermined value which appears in a light intensity distribution of the interference fringes, and detect incremental positions based on the interference fringes which appear at positions other than the position where light intensity is lower than the predetermined value,wherein, the detection head includes;
a light source configured to radiate beams onto the scale;
a detecting unit, arranged in parallel with the scale, having a plurality of light receiving devices aligned along the measurement direction to obtain the light intensity distribution, and configured to output the detection result of the beams radiated onto the plurality of light receiving devices, to the signal processor; and
an optical system disposed between the scale and the detecting unit, and configured to image positive s-th-order diffracted beams and negative s-th-order diffracted beams generated when the beams are radiated onto the scale, on the detecting unit.
1 Assignment
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Accused Products
Abstract
A scale has a first pattern area and a second pattern areas disposed with an offset from the first pattern area in a measurement direction by 1/(2×s) of pitch. A detection head detects interference fringes caused by positive s-th-order diffracted beams and negative s-th-order diffracted beams diffracted by the scale, and output a detection result. A signal processing unit detects a reference position based on a position where light intensity is lower than a predetermined value which appears in a light intensity distribution of the interference fringes, and detects incremental positions based on the interference fringes which appear at other positions. The detection head includes a light source, a detecting unit configured to output the detection result of the beams radiated onto light receiving devices to the signal processing unit, and an optical system configured to image positive s-th-order diffracted beams and negative s-th-order diffracted beams on the detecting unit.
38 Citations
13 Claims
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1. An encoder comprising:
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a scale having a plurality of pattern areas having a plurality of patterns arranged in a measurement direction with an equal predetermined pitch and including at least one pattern area disposed with an offset, in the measurement direction, from a neighboring pattern area by 1/(2×
s) of the predetermined pitch (wherein “
s”
is an integer of 1 or greater), the plurality of patterns comprising at least first and second patterns, each of which comprises a plurality of spaced pattern elements, that are linearly arranged in the measurement direction;a detection head configured to be relatively movable in the measurement direction with respect to the scale, and detect interference fringes caused by positive s-th-order diffracted beams and negative s-th-order diffracted beams diffracted by the scale, and output a detection result; and a signal processor configured to detect a reference position based on a position where light intensity is lower than a predetermined value which appears in a light intensity distribution of the interference fringes, and detect incremental positions based on the interference fringes which appear at positions other than the position where light intensity is lower than the predetermined value, wherein, the detection head includes; a light source configured to radiate beams onto the scale; a detecting unit, arranged in parallel with the scale, having a plurality of light receiving devices aligned along the measurement direction to obtain the light intensity distribution, and configured to output the detection result of the beams radiated onto the plurality of light receiving devices, to the signal processor; and an optical system disposed between the scale and the detecting unit, and configured to image positive s-th-order diffracted beams and negative s-th-order diffracted beams generated when the beams are radiated onto the scale, on the detecting unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification