# US 10,119,802 B2 · Optical position-measuring device having grating fields with different step heights

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- Number: US 10,119,802 B2
- Document ID: US10119802B2
- Status: Granted
- Kind: B2
- Application number: 15/410,806
- Filed: 2017-01-20
- Published: 2017-07-27
- Granted: 2018-11-06
- Earliest claimed: 2016-01-21
- Assignees: Dr. Johannes Heidenhain GmbH
- Applicants: DR. JOHANNES HEIDENHAIN GmbH
- Inventors: Peter Speckbacher; Tobias Gruendl; Christian Baeuml; Josef Weidmann
- Web page: https://patentgrep.com/patent/US10119802B2

## CPC

- G01B 9/02034: {characterised by particularly shaped beams or wavefronts}
- G01B 9/02017: with multiple interactions between the target object and light beams, e.g. beam reflections occurring from different locations
- G01D 5/38: by diffraction gratings
- G01B 2290/30: Grating as beam-splitter
- G01B 2290/65: Spatial scanning object beam
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- 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

An optical position-measuring device includes a scale and a scanning reticle, whose relative position is determinable in three linearly independent spatial directions using interfering light beams. A splitter grating is disposed on the scanning reticle and adapted to split light into sub-beams of different diffraction orders. An optical grating is disposed on the scale and adapted to further split the sub-beams and to recombine them after they have been reflected back from the scanning reticle. Grating fields configured as phase gratings are disposed on a side of the scanning reticle that faces the scale. The grating fields act as diffractive optics that influence the further split sub-beams. The grating fields have different step heights. An output grating is disposed on the scanning reticle and adapted to output, as interfering sub-beams, light that has been multiply reflected between the scale and the scanning reticle.

## Claims

### Claim 1

An optical position-measuring device, comprising:
a scale and a scanning reticle, whose relative position is determinable in three linearly independent spatial directions using a plurality of interfering light beams, two of the spatial directions being parallel to a plane of the scale and parallel to a plane of the scanning reticle, and the other one of the spatial directions having a component being perpendicular thereto;
a splitter grating disposed on the scanning reticle and adapted to split light into a plurality of sub-beams of different diffraction orders;
an optical grating disposed on the scale and adapted to further split the sub-beams and to recombine the further split sub-beams after the further split sub-beams have been reflected back from the scanning reticle;
a plurality of grating fields configured as phase gratings disposed on a side of the scanning reticle that faces the scale, the grating fields acting as diffractive optics that influence the further split sub-beams, each of the grating fields comprising a plurality of graduation periods and a same step height, the step heights of the grating fields being different from each other; and
an output grating disposed on the scanning reticle and adapted to output, as interfering sub-beams, light that has been multiply reflected between the scale and the scanning reticle.

### Claim 2 (depends on 1)

The device as recited in claim 1, wherein grating fields having the same step height are arranged in pairs symmetrically with respect to a center of the scanning reticle.

### Claim 3 (depends on 2)

The device as recited in claim 2, wherein the center of the scanning reticle is located between the splitter grating and the output grating.

### Claim 4 (depends on 1)

The device as recited in claim 1, wherein the scanning reticle includes a glass-ceramic having a thermal expansion coefficient of nearly zero, on which is disposed a layer in which the grating fields are formed by etching.

### Claim 5 (depends on 4)

The device as recited in claim 4, wherein the layer is a silicon dioxide layer.

### Claim 6 (depends on 1)

The device as recited in claim 1, wherein the scanning reticle includes a quartz glass substrate in which the grating fields are formed by etching.

### Claim 7 (depends on 1)

The device as recited in claim 1, wherein the scanning reticle includes a glass-ceramic having a thermal expansion coefficient of nearly zero, on which is disposed a layer stack including layers having different refractive indices, and wherein the grating fields are formed in the layer stack by etching.

### Claim 8 (depends on 7)

The device as recited in claim 7, wherein the layer stack includes layers of silicon dioxide and silicon.

### Claim 9 (depends on 1)

The device as recited in claim 1, further comprising a monochromatic light source configured to generate the light.