Displacement encoder

Patent metadata

Field	Value
Publication number	US-10094685-B2
Application number	US-201615391243-A
Country	US
Kind code	B2
Filing date	Dec 27, 2016
Priority date	Dec 27, 2016
Publication date	Oct 9, 2018
Grant date	Oct 9, 2018

Abstract

A detection head movable relative to a scale detects diffracted light and outputs a detection result. The diffracted light is diffracted by an incremental pattern. A signal processing unit calculates a relative displacement between the scale and the detection head. The detection head includes: a light source emitting the light to the scale; and a detection unit including a light-receiving unit in which a plurality of light-receiving elements that output a detection signal are arranged. The number of the plurality of light-receiving elements is an even number. A period of the arrangement of the plurality of light-receiving elements is an odd-number multiple of a fundamental period. The fundamental period is a period of interference fringes formed on the light-receiving unit by +1st and −1st order diffracted lights. A width of the light-receiving element is not equal to an integral multiple of the fundamental period.

First claim

What is claimed is:

1. A displacement encoder comprising:
a scale with an incremental pattern formed therein;
a detection head movable relative to the scale in a measurement direction, the detection head being configured to detect diffracted light and output a detection result, the diffracted light being obtained by diffraction of light emitted to the scale by the incremental pattern; and
a signal processing unit configured to calculate a relative displacement between the scale and the detection head based on the detection result obtained by the detection head, wherein
the detection head comprises:
a light source configured to emit the light to the scale; and
a detection unit comprising a light-receiving unit comprising a plurality of light-receiving elements arranged in the measurement direction, the plurality of light-receiving elements being configured to output a detection signal of the diffracted light from the scale,

the number of the plurality of light-receiving elements arranged in the measurement direction is an even number,
a period of the arrangement of the plurality of light-receiving elements is an odd-number multiple of a fundamental period, the fundamental period being a period of interference fringes formed on the light-receiving unit by +1st order diffracted light and −1st order diffracted light of the diffracted light, and
a width of the light-receiving element in the measurement direction is not equal to an integral multiple of the fundamental period.

2. The displacement encoder according to claim 1 , wherein the +1st order diffracted light, −1st order diffracted light, and 0th order diffracted light from the scale are incident on the detection unit.

3. The displacement encoder according to claim 1 , wherein
a plurality of light-receiving units are arranged in the measurement direction in the detection unit, and
among the plurality of light-receiving units, two light-receiving units adjacent to each other are shifted from each other by a distance equivalent to a quarter of the fundamental period so as to be apart from each other in the measurement direction.

4. The displacement encoder according to claim 3 , wherein
first and second light-receiving units are arranged in this order in the measurement direction in the detection unit, and
the detection unit outputs a detection signal output from the first light-receiving unit to the signal processing unit as an A phase signal and outputs a detection signal output from the second light-receiving unit to the signal processing unit as a B phase signal.

5. The displacement encoder according to claim 3 , wherein
first, second, third and fourth light-receiving units are arranged in this order in the measurement direction in the detection unit, and
the detection unit outputs a differential A phase signal and a differential B phase signal to the signal processing unit, the differential A phase signal being a differential signal between an A phase signal and an A− phase signal, the differential B phase signal being a differential signal between a B phase signal and a B− phase signal, the A phase signal being a detection signal output from the first detection unit, the A− phase signal being a detection signal output from the third detection unit, the B phase signal being a detection signal output from the second detection unit, and the B− phase signal being a detection signal output from the fourth detection unit.

6. The displacement encoder according to claim 1 , wherein
a plurality of light-receiving units are arranged in the measurement direction in the detection unit, and
among the plurality of light-receiving units, two light-receiving units adjacent to each other are shifted from each other by a distance equivalent to one third of the fundamental period so as to be apart from each other in the measurement direction.

7. The displacement encoder according to claim 6 , wherein
first, second and third light-receiving units are arranged in this order in the measurement direction in the detection unit, and
the detection unit outputs a differential A phase signal and a differential B phase signal to the signal processing unit, the differential A phase signal and the differential B phase signal being generated by combining an A phase signal, a B phase signal, and a C phase signal, and having phases different from each other by 90°, the A phase signal being a detection signal output from the first detection unit, the B phase signal being a detection signal output from the second detection unit, and the C phase signal being a detection signal output from the third detection unit.

8. A displacement encoder comprising:
a scale with an incremental pattern formed therein;
a detection head movable relative to the scale in a measurement direction, the detection head being configured to detect diffracted light and output a detection result, the diffracted light being obtained by diffraction of light emitted to the scale by the incremental pattern; and
a signal processor configured to calculate a relative displacement between the scale and the detection head based on the detection result obtained by the detection head, wherein
the detection head comprises:
a light source configured to emit the light to the scale; and
a detector comprising a light-receiver comprising a plurality of light-receiving elements arranged in the measurement direction, the plurality of light-receiving elements being configured to output a detection signal of the diffracted light from the scale,

the number of the plurality of light-receiving elements arranged in the measurement direction is an even number,
a period of the arrangement of the plurality of light-receiving elements is an odd-number multiple of a fundamental period, the fundamental period being a period of interference fringes formed on the light-receiver by +1st order diffracted light and −1st order diffracted light of the diffracted light, and
a width of the light-receiving element in the measurement direction is not equal to an integral multiple of the fundamental period.

9. The displacement encoder according to claim 8 , wherein the +1st order diffracted light, −1st order diffracted light, and 0th order diffracted light from the scale are incident on the detector.

10. The displacement encoder according to claim 8 , wherein
a plurality of light-receivers are arranged in the measurement direction in the detector, and
among the plurality of light-receivers, two light-receivers adjacent to each other are shifted from each other by a distance equivalent to a quarter of the fundamental period so as to be apart from each other in the measurement direction.

11. The displacement encoder according to claim 10 , wherein
first and second light-receivers are arranged in this order in the measurement direction in the detector, and
the detector outputs a detection signal output from the first light-receiver to the signal processor as an A phase signal and outputs a detection signal output from the second light-receiver to the signal processor as a B phase signal.

12. The displacement encoder according to claim 10 , wherein
first, second, third and fourth light-receivers are arranged in this order in the measurement direction in the detector, and
the detector outputs a differential A phase signal and a differential B phase signal to the signal processor, the differential A phase signal being a differential signal between an A phase signal and an A− phase signal, the differential B phase signal being a differential signal between a B phase signal and a B− phase signal, the A phase signal being a detection signal output from the first detector, the A− phase signal be

Assignees

• Mitutoyo Corp

Inventors

• Kimura Akihide
• Tobiason Joseph Daniel

Classifications

• G01D5/34746 Primary

  Linear encoders · CPC title

• G01D5/38 Primary

  by diffraction gratings · CPC title