Optical position measuring device

Patent metadata

Field	Value
Publication number	US-9733068-B2
Application number	US-201514733435-A
Country	US
Kind code	B2
Filing date	Jun 8, 2015
Priority date	Jun 10, 2014
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

In an optical position measuring device for detecting the relative position of a first measuring standard and a second measuring standard, movable relative to each other along at least one measuring direction, at a splitting grating, a beam bundle emitted by a light source is split up into at least two partial beam bundles. When passing through scanning beam paths, the partial beam bundles undergo different polarization-optical effects. After the differently polarized partial beam bundles are recombined at a combination grating, a plurality of phase-displaced, displacement-dependent scanning signals is able to be generated from the resulting beam bundle. No polarization-optical components are arranged in the scanning beam paths of the partial beam bundles between the splitting and recombination. To generate the different polarization-optical effects on the partial beam bundles, a conically incident illumination beam bundle impinges upon the splitting grating, the incident illumination beam bundle extending in a plane perpendicular to the measuring direction at an angle other than 0°, the plane of incidence being defined by the grating normal to the splitting grating and the direction of incidence of the illumination beam bundle. The scanning beam paths of the partial beam bundles are arranged in mirror symmetry with respect to the plane of incidence between the splitting and recombination.

First claim

What is claimed is:

1. An optical position measuring device, comprising:
a splitting grating adapted to split an illumination beam bundle emitted by a light source into at least two partial beam bundles;
a combination grating adapted to recombine the partial beam bundles, so that a plurality of phase-displaced, displacement-dependent scanning signals is generatable from the resulting signal beam bundle, no polarization-optical components being located in scanning beam paths of the partial beam bundles between the splitting grating and the combination grating;
wherein, in order to attain different polarization-optical effects on the partial beam bundles when passing through the scanning beam paths:
a conically incident illumination beam bundle impinges upon the splitting grating, the incident illumination beam bundle extending in a plane of incidence perpendicular to the measuring direction at an angle other than 0°, and the plane of incidence defined by a grating normal to the splitting grating and a direction of incidence of the illumination beam bundle; and
the scanning beam paths of the partial beam bundles are formed in mirror symmetry with respect to the plane of incidence; and

wherein the optical position measuring device is adapted to detect a relative position of a first measuring standard and a second measuring standard, movable relative to each other along at least one measuring direction.

2. The optical position measuring device according to claim 1 , wherein the illumination beam bundle emitted by the light source has a linear polarization having a symmetrical or antisymmetrical mirror symmetry with respect to the plane of incidence.

3. The optical position measuring device according to claim 2 , wherein at least one grating is arranged in the scanning beam paths of the partial beam bundles between the splitting grating and the combination grating such that:
the mirror symmetry with respect to the plane of incidence is maintained for the partial beam bundles; and
a polarization crosstalk of partial beam bundles that are polarized in a perpendicular and parallel manner is possible.

4. The optical position measuring device according to claim 3 , wherein the partial beam bundles have an opposite circular polarization at the recombination location.

5. The optical position measuring device according to claim 3 , wherein the partial beam bundles have a mutually orthogonal elliptical polarization at the recombination location.

6. The optical position measuring device according to claim 3 , wherein the partial beam bundles are polarized such that, at the recombination location, a vector product of associated Jones vectors does not exceed ⅔.

7. The optical position measuring device according to claim 1 , wherein the first measuring standard includes a first reflection grating or transmission grating, which extends in the measuring direction and functions as a splitting grating for the illumination beam bundle.

8. The optical position measuring device according to claim 7 , wherein the first measuring standard includes a second reflection grating or transmission grating, which extends in the measuring direction and functions as a combination grating for the partial beam bundles.

9. The optical position measuring device according to claim 7 , wherein the second measuring standard includes a transparent plate in which a diffractive roof prism having a lens and a reflector is provided for each partial beam bundle.

10. The optical position measuring device according to claim 9 , wherein:
on a first side of the transparent plate facing the first measuring standard, the lenses include at least one transmission grating; and
on a second side of the transparent plate facing away from the first measuring standard, the reflector includes at least one reflecting layer, having a reflecting side oriented in a direction of the first side of the plate.

11. The optical position measuring device according to claim 9 , wherein the first measuring standard and the second measuring standard are arranged such that:
the illumination beam bundle incident from the light source is split up into two partial beam bundles at the first reflection grating of the first measuring standard and the partial beam bundles then propagate in a direction of the second measuring standard;
the partial beam bundles pass through a diffractive retro-reflector or a roof reflector in the transparent plate of the second measuring standard and then propagate back again in a direction of the first measuring standard at a perpendicular offset with respect to the measuring direction; and
the partial beam bundles are superposed at a recombination location on the second reflection grating of the first measuring standard, and a signal beam bundle with the pair of superposed partial beam bundles propagates back again in the direction of the second measuring standard.

12. The optical position measuring device according to claim 11 , further comprising a scanning unit, stationary in relation to the two measuring standards, including a path-folding mirror, a grating, a lens, and a plurality of polarizers, the scanning unit being coupled via at least one optical fiber to a light source and a plurality of detector elements.

13. The optical position measuring device according to claim 11 , further comprising a scanning unit, stationary in relating to the two measuring standards, including a light source, a path-folding mirror, a grating, a lens, a plurality of polarizers, and a plurality of detector elements.

14. The optical position measuring device according to claim 8 , wherein the second measuring standard includes a transparent plate in which a diffractive retro-reflector or a diffractive roof prism having a lens and a reflector is provided for each partial beam bundle.

15. The optical position measuring device according to claim 14 , wherein:
on a first side of the transparent plate facing the first measuring standard, the lenses include at least one transmission grating; and
on a second side of the transparent plate facing away from the first measuring standard, the reflector includes at least one reflecting layer, having a reflecting side oriented in a direction of the first side of the plate.

16. The optical position measuring device according to claim 14 , wherein the first measuring standard and the second measuring standard are arranged such that:
the illumination beam bundle incident from the light source is split up into two partial beam bundles at the first reflection grating of the first measuring standard and the partial beam bundles then propagate in a direction of the second measuring standard;
the partial beam bundles pass through a diffractive retro-reflector or a roof reflector in the transparent plate of the second measuring standard and then propagate back again in a direction of the first measuring standard at a perpendicular offset with respect to the measuring direction; and
the partial beam bundles are superposed at a recombination location on the second reflection grating of the first measuring standard, and a signal beam bundle with the pair of superposed partial beam bundles propagates back again in the direction of the second measuring standard.

17. The optical position measuring device according to claim 16 , further comprising a scanning unit, stationary in relation to the two measuring standards, including a path-folding mirror, a grating, a lens, and a plurality of polarizers, the scanning unit being coupled via at least one optical fiber to a light source and a plurality of detector ele

Assignees

• Dr Johannes Heidenhan Gmbh
• Heidenhain Gmbh Dr Johannes

Inventors

• Drescher Jörg
• Holzapfel Wolfgang
• Joerger Ralph
• Kälberer Thomas
• Meissner Markus
• Musch Bernhard
• Spanner Erwin

Classifications

• G01D5/266 Primary

  by interferometric means (G01D5/353 takes precedence) · CPC title

• G01B9/02015

  characterised by the beam path configuration · CPC title

• G01B11/14 Primary

  for measuring distance or clearance between spaced objects or spaced apertures (G01B11/26 takes precedence; rangefinders G01C3/00) · CPC title

• G01D5/34707

  Scales; Discs, e.g. fixation, fabrication, compensation · CPC title

• G01D5/345

  Polarising encoders · CPC title