Optical position-measuring device

Patent metadata

Field	Value
Publication number	US-9291481-B2
Application number	US-201314135043-A
Country	US
Kind code	B2
Filing date	Dec 19, 2013
Priority date	Dec 20, 2012
Publication date	Mar 22, 2016
Grant date	Mar 22, 2016

Abstract

An optical position-measuring device is adapted to detect the position of an object in several spatial degrees of freedom. The object is disposed in a manner allowing it to move at least along a first direction of movement and along a second direction of movement. The position-measuring device includes at least one light source and at least one first and second measuring standard which are located on the object, extend along a first extension direction and a second extension direction and include graduation regions disposed periodically along the first and second extension directions. In addition, a scanning plate is provided, into which at least first and second retroreflector elements are integrated, the first retroreflector element extending parallel to the first extension direction and the second retroreflector element extending parallel to the second extension direction, and via which, sub-beams that fall on them from the first and second measuring standard, are reflected back in the direction of the respective measuring standard. From superposed sub-beams, a detector system is able to generate position signals at least with respect to the movement of the object along the first and second direction of movement.

First claim

What is claimed is:

1. An optical position-measuring device for detecting a position of an object in several degrees of freedom, the object being movable at least along a first direction of movement and along a second direction of movement, comprising:
at least one light source;
at least one first measuring standard, arranged on the object, extending along a first extension direction and including graduation regions arranged periodically along the first extension direction;
at least one second measuring standard, arranged on the object, which extending along a second extension direction and including graduation regions arranged periodically along the second extension direction;
a single scanning plate, including integrated first and second retroreflector elements, a length direction of the first retroreflector element extending parallel to the first extension direction and a length direction of the second retroreflector element extending parallel to the second extension direction, the first and second retroreflector elements adapted to reflect back in a direction of a respective measuring standard sub-beams that fall on the first and second retroreflectors from the first and second measuring standards; and
a detector system adapted to generate, from superposed sub-beams, at least position signals with respect to movement of the object along the first and second directions of movement;
wherein the retroreflector elements are arranged as diffractive retroreflector elements, including:
a plurality of diffractive elements provided on a first side of the scanning plate;
and at least one reflector element that is provided on an opposite second side of the scanning plate and having a reflective side oriented in a direction of the diffractive elements, the reflector element extending parallel to the first extension direction or the second extension direction.

2. The optical position-measuring device according to claim 1 , wherein four diffractive elements per retroreflector element are provided on a first side of the scanning plate, so that a pair of sub-beams incoming from a first point of incidence on an associated measuring standard initially passes through first and second diffractive elements and in each instance is thereby focused and deflected to the reflector element on the opposite second side of the scanning plate, at the reflector element, the two sub-beams are reflected back to a third and fourth diffractive element, via which traversing sub-beams in each case are collimated and deflected in a direction of a second point of incidence on the associated measuring standard.

3. The optical position-measuring device according to claim 1 , wherein the diffractive elements include locally limited transmission gratings provided on the first side of the scanning plate and having curved grating lines.

4. The optical position-measuring device according to claim 1 , wherein the scanning plate includes an integrated third retroreflector element that extends parallel to the second extension direction, the third retroreflector element adapted to reflect back in a direction of the second measuring standard sub-beams that fall on the third retroreflector element from the second measuring standard.

5. The optical position-measuring device according to claim 1 , wherein the first and second measuring standards include reflection gratings, and the graduation regions of the first and second measuring standards are oriented perpendicularly to each other.

6. The optical position-measuring device according to claim 5 , wherein the first and second measuring standards are superimposed with each other in the form of a cross grating.

7. The optical position-measuring device according to claim 1 , further comprising:
at least one measuring reflector provided on the object;
at least one beam-splitter element, mechanically coupled to the scanning plate, adapted to split a beam of rays falling on beam-splitter element into at least one measurement beam and at least one reference beam, so that at least one interferometer measuring arm is formed by the measurement beam propagating in a direction of the measuring reflectors, and an interferometer reference arm is formed by the reference beam; and
an interferometer detector system adapted to generate, from superposed measurement and reference beams, position signals with respect to movement of the object along a third direction of movement that is oriented perpendicularly to the first and second directions of movement.

8. The optical position-measuring device according to claim 7 , wherein the beam-splitter element, a plurality of diffractive elements, and at least one reflector element are integrated into the scanning plate, so that between the splitting at the beam-splitter element and the superposition with the measurement beam, the reference beam propagates exclusively in the scanning plate.

9. The optical position-measuring device according to claim 7 , wherein the measuring reflector includes a diffractive element and a reflector element.

10. The optical position-measuring device according to claim 7 , wherein at least three measurement beams, arranged symmetrically relative to each other, propagate in a direction of the at least one measuring reflector.

11. The optical position-measuring device according to claim 1 , wherein a single light source is provided at least for scanning the first and second measuring standards.

12. The optical position-measuring device according to claim 1 , wherein the first direction of movement is oriented parallel to the first extension direction, and the second direction of movement is oriented parallel to the second extension direction.

13. The optical position-measuring device according to claim 7 , wherein at least one splitting element is adapted to direct at least a portion of the sub-beams to a position-sensitive electro-optical detector element adapted to detect a point of incidence of the sub-beams falling on the position-sensitive electro-optical detector element to determine the position of the object in the case of a rotation about at least one direction of movement.

14. The optical position-measuring device according to claim 13 , wherein the first direction of movement forms an angle of 45° with the first extension direction, and the second direction of movement forms an angle of 45° with the second extension direction.

Assignees

• Heidenhain Gmbh Dr Johannes

Inventors

• Meissner Markus
• Holzapfel Wolfgang

Classifications

• G01D5/38 Primary

  by diffraction gratings · CPC title

• G01B11/002

  for measuring two or more coordinates · CPC title