# US 10,119,844 B2 · Scale for an absolute position detection type photoelectric encoder with three or more two-bit combination patterns are used to represent a two-level code pattern

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- Number: US 10,119,844 B2
- Document ID: US10119844B2
- Status: Granted
- Kind: B2
- Application number: 15/262,423
- Filed: 2016-09-12
- Published: 2017-03-16
- Granted: 2018-11-06
- Earliest claimed: 2015-09-14
- Assignees: Mitutoyo Corporation
- Applicants: Mitutoyo Corporation
- Inventors: Shu Hirata
- Web page: https://patentgrep.com/patent/US10119844B2

## CPC

- G01D 5/34792: {with only digital scales or both digital and incremental scales}
- G01D 5/34707: {Scales; Discs, e.g. fixation, fabrication, compensation}
- G01D 5/34776: {Absolute encoders with analogue or digital scales}
- G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR

## Abstract

There is provided an absolute position detection type photoelectric encoder which improves robustness to dirt while maintaining high resolution. A two-level code pattern according to a pseudo random code sequence is provided on a scale along a length measurement direction. Each code of the two-level code pattern indicates a code “1” or a code “0”, and includes two bits. Each of the two bits is L or H. The code “1” is represented by an A pattern which is a combination of L and H, and the code “0” is represented by a B pattern which is a combination of L and L or a C pattern which is a combination of H and H. When the codes “0” are continued, the B pattern and the C pattern are alternately used.

## Claims

### Claim 1

A scale used for an absolute position detection type photoelectric encoder, the scale comprising:
a two-level code pattern, according to a pseudo random code sequence, provided along a length measurement direction,
wherein codes in the two-level code pattern each consist of a combination of two bits, and three or more two-bit combination patterns are used to represent the codes in the two-level code pattern.

### Claim 2 (depends on 1)

The scale according to claim 1, wherein:
each of the codes of the two-level code pattern indicates a code “1” or a code “0”,
each of the two bits is a light transmitting bit (L) or a light reflecting bit (H),
the number of continuous L in the two-level code pattern is equal to or less than a predetermined upper limit value, and
the number of continuous H in the two-level code pattern is equal to or less than the predetermined upper limit value.

### Claim 3 (depends on 2)

The scale according to claim 2, wherein:
the code “0” is represented by two or more of the two-bit combination patterns, and
a two-bit combination pattern different from a previous two-bit combination pattern is used for each successive code “0” in the two-level code pattern.

### Claim 4 (depends on 2)

The scale according to claim 2, wherein:
the code “1” is represented by an A pattern which is a combination of L and H,
the code “0” is represented by a B pattern which is a combination of L and L, or by a C pattern which is a combination of H and H, and
the B pattern and the C pattern are alternately used for each successive code “0” in the two-level code pattern.

### Claim 5 (depends on 1)

The scale according to claim 1, wherein:
each of the codes of the two-level code pattern indicates a code “1” or a code “0”,
each of the two bits is a light transmitting bit (L), a light reflecting bit (H), or a halftone bit (M),
the code “1” is represented by an A pattern which is a combination of L and H,
the code “0” is represented by two or more patterns selected from a B pattern which is a combination of L and L, a C pattern which is a combination of H and H, and a D pattern which is a combination of M and M, and
a two-bit combination pattern different from a previous two-bit combination pattern is used for each successive code “0” in the two-level code pattern.

### Claim 6 (depends on 3)

The scale according to claim 3, wherein the code “1” and the code “0” are replaceable with each other.

### Claim 7 (depends on 1)

A photoelectric encoder comprising:
the scale according to claim 1; and
a detection unit provided to be relatively movable along the scale and configured to detect an absolute position on the scale based on the pseudo random code sequence on the scale.