Device for interferential distance measurement

• US 9,739,598 B2
• Filed: 03/11/2014
• Issued: 08/22/2017
• Est. Priority Date: 04/15/2013
• Status: Active Grant

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr. Johannes Heidenhain GmbH
• Inventors: Joerger, Ralph, Huber, Walter
• Primary Examiner(s): Hansen, Jonathan
• Application Number:
  US14/784,518
• Publication Number:
  US 20160061587A1
• Time in Patent Office: 1,260 Days
• Field of Search: 356498
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01B 11/14 for measuring distance or clearance between spaced objects or spaced apertures G01B11/26 takes precedence; rangefinders G01C3/00
• CPC Class Codes: G01B 2290/30 Grating as beam-splitter
• CPC Class Codes: G01B 9/02018 Multipass interferometers, e.g. double-pass
• CPC Class Codes: G01B 9/02035 Shaping the focal point, e.g. elongated focus
• CPC Class Codes: G01B 9/02058 by particular optical compensation or alignment elements, e.g. dispersion compensation
• CPC Class Codes: G01B 9/02061 Reduction or prevention of effects of tilts or misalignment
• CPC Class Codes: G01B 9/02097 Self-interferometers

Abstract

A device for interferential distance measurement between two objects that are situated in a movable manner with respect to each other along at least one shifting direction includes at least one light source as well as at least one splitting element, which splits a beam of rays emitted by the light source at a splitting location into at least two partial beams that propagate onward at different angles. The device furthermore includes at least one deflecting element that effects a deflection of the incident partial beams in the direction of a merging location, where the split partial beams are superimposed in an interfering manner and the optical paths of the partial beams of rays between the splitting location and the merging location being arranged such that the traversed optical path lengths of the partial beams between the splitting location and the merging location are identical in the event of a change of distance between the two objects. Furthermore, at least one detector system is provided for detecting distance-dependent signals from the superimposed pair of interfering partial beams.

Claims

1. A device for interferential distance measurement between two objects movable with respect to each other along at least one shifting direction, comprising:

at least one light source;

at least one splitting element adapted to split a beam of rays emitted by the light source at a splitting location into at least two partial beams that propagate onward at different angles;

at least one deflecting element adapted to deflect the partial beams striking it in a direction of a merging location, where the split partial beams are interferingly superimposed and where optical paths of the partial beams between the splitting location and the merging location are adapted such that traversed optical path lengths of the partial beams between the splitting location and the merging location are identical in the event of a change of distance between the two objects; and

at least one detector system adapted to detect distance-dependent signals from the superimposed pair of interfering partial beams.

2. The device according to claim 1, wherein a first one of the two objects is connected with at least one scanning unit, which includes at least one light source, at least one detector system, and at least one first deflecting element, and a second one of the two objects is connected either with a measuring reflector or with a splitting element.

3. The device according to claim 2, wherein the partial beams in the scanning unit propagate symmetrically, at least in a portion of the optical path, with respect to at least one axis of symmetry of the scanning unit.

4. The device according to claim 2, wherein either (a) the scanning unit includes two partial scanning units situated in mirror symmetry with respect to a mirror plane oriented parallel to the shifting direction or (b) in the case of a single utilized scanning unit, the scanning unit is arranged in mirror symmetry with respect to a mirror plane oriented parallel to the shifting direction.

5. The device according to claim 1, wherein the position and/or arrangement of the at least one deflecting element ensure that the traversed optical path lengths of the partial beams between the splitting location and the merging location are identical in the event of a change of distance between the two objects.

6. The device according to claim 2, wherein the splitting element is arranged as a one-dimensional transmission grating and the scanning unit includes at least one first measuring standard, which has a two-dimensional transmission cross grating and a reflector arranged parallel to it.

7. The device according to claim 6, wherein the transmission cross grating and the reflector are arranged perpendicularly with respect to the transmission grating of the splitting element.

8. The device according to claim 6, wherein the deflecting element includes a deflecting prism.

9. The device according to claim 6, wherein:

the beam of rays emitted by the light source is split into two partial beams at the splitting element and the two partial beams propagate in the direction of scanning unit;

in the scanning unit, the partial beams are deflected via the deflecting element in the direction of the measuring standard;

the partial beams passing through the transmission cross grating of the measuring standard, are deflected and then strike the reflector;

a reflection occurs from the reflector back in the direction of the transmission cross grating, where after a new transmission through the transmission cross grating another deflection results such that the partial beams propagate in a parallel offset manner with respect to the direction of incidence to the deflecting element;

the partial beams are deflected on the deflecting element in the direction of the merging location; and

the superimposed partial beams then propagate in the direction of the detector system.

10. The device according to claim 6, wherein the scanning unit includes a second deflecting element and a second measuring standard, which includes a two-dimensional transmission cross grating and a reflector, the second deflecting element and the second measuring standard being arranged in the scanning unit in mirror symmetry with respect to the first deflecting element and to the first measuring standard.

11. The device according to claim 2, wherein the scanning unit (120) connected with a first one of the objects includes at least four deflecting elements, each arranged as a one-dimensional reflection grating, and at least one splitting element, which is arranged as a one-dimensional transmission grating, and a measuring reflector is connected with a second one of the two object, which is arranged as a plane reflector.

12. The device according to claim 11, wherein the scanning unit includes a transparent carrier body having a truncated pyramid-shaped cross section, the splitting element being situated on a surface of the transparent carrier body facing the measuring reflector, and the at least four deflecting elements being situated on lateral surfaces of the transparent carrier body.

13. The device according to claim 11, wherein:

the beam of rays emitted by the light source is split into two partial beams at the splitting element and the two partial beams propagate in the direction of the measuring reflector;

a reflection of the partial beams occurs from the measuring reflector back in the direction of the first and second deflecting elements in the scanning unit, where the partial beams are deflected in the direction of the third and fourth deflecting elements; and

a deflection of the partial beams of rays to the measuring reflector occurs via the third and fourth deflecting elements;

from the measuring reflector, the partial beams are reflected back in the direction of the merging location in the scanning unit; and

the superimposed partial beams then propagate in the direction of the detector system.

14. The device according to claim 11, wherein the deflecting elements located in the scanning unit are configured to provide a focusing effect on the partial beams propagating in the scanning unit such that a line focus results in a center of symmetry of the scanning unit.