Optical position-measuring device having incremental detector and absolute detector disposed in a common detection plane at a defined perpendicular distance from a scanning grating

Patent metadata

Field	Value
Publication number	US-9863791-B2
Application number	US-201615232830-A
Country	US
Kind code	B2
Filing date	Aug 10, 2016
Priority date	Aug 26, 2015
Publication date	Jan 9, 2018
Grant date	Jan 9, 2018

Abstract

An optical position-measuring device for absolute position determination includes a material measure extending along a measurement direction and including an incremental graduation and an absolute code. A scanning unit movable relative to the material measure has a light source, a scanning grating for optically scanning the incremental graduation and a detector device. The detector device includes an incremental detector for generating incremental signals from the optical scanning of the incremental graduation and an absolute detector for generating absolute signals from optical scanning of the absolute code. A common detection plane is located at a defined perpendicular distance from the scanning grating and/or a periodicity of a fringe pattern on the incremental detector is selected such that, in the event of scattering contamination in a region of the material measure and/or the scanning grating, amplitudes of the incremental signals and the absolute signals drop off equally.

First claim

What is claimed is:

1. An optical position-measuring device for absolute position determination, comprising:
a material measure extending along a measurement direction and including at least one incremental graduation and an absolute code; and
a scanning unit which is movable relative to the material measure along the measurement direction, the scanning unit having alight source, a scanning grating for optically scanning the incremental graduation and a detector device, the detector device including an incremental detector configured to generate incremental signals from the optical scanning of the incremental graduation and an absolute detector configured to generate absolute signals from optical scanning of the absolute code, the incremental detector and the absolute detector being disposed in a common detection plane, the detection plane being located at a defined perpendicular distance front the scanning grating and/or a periodicity of a fringe pattern on the incremental detector being selected such that, in the event of scattering contamination in a region of the material measure and/or the scanning grating, amplitudes of the incremental signals and amplitudes of the absolute signals drop off equally.

2. The optical position-measuring device as recited in claim 1 , wherein the perpendicular distance between the scanning grating and the detection plane is selected either in accordance with:

v
=

u
·

(

1

d
1

-

1

2
·

d
ABS

)

(

1

d
3

+

1

2
·

d
ABS

)

±

10
⁢
%

or in accordance with:

v
=

u
·

(

1

d
1

+

1

2
·

d
ABS

)

(

1

d
3

-

1

2
·

d
ABS

)

±

10
⁢
%

where:
v=perpendicular distance between the scanning grating and the detection plane,
u=perpendicular distance between the material measure and the scanning grating,
d 1 =grating period of the incremental graduation on the material measure,
d 3 =periodicity of the fringe pattern on the incremental detector, and
d ABS =width of the smallest structure of the absolute code in the measurement direction.

3. The optical position-measuring device as recited in claim 1 , wherein the periodicity of the fringe pattern on the incremental detector is selected in accordance with
d 3 =2· d ABS ±10%

where:
d 3 =periodicity of the fringe pattern on the incremental detector, and
d ABS =width of the smallest structure of the absolute code in the measurement direction.

4. The optical position-measuring device as recited in claim 1 , wherein the perpendicular distance between the scanning grating and the detection plane is selected in accordance with

v
=

1
2

⁢

u
·

d
3

·

(

1

d
1

-

1

2
·

d
ABS

)

±

10
⁢
%

where:
v=perpendicular distance between the scanning grating and the detection plane,
u=perpendicular distance between the material measure and the scanning grating,
d 1 =grating period of the incremental graduation on the material measure,
d 3 =periodicity of the fringe pattern on the incremental detector, and
d ABS =width of the smallest structure of the absolute code in the measurement direction.

5

Assignees

• Heidenhain Gmbh Dr Johannes

Inventors

• Holzapfel Wolfgang
• Lingk Christoph
• Trautner Johannes

Classifications

• G01D5/34776 Primary

  Absolute encoders with analogue or digital scales · CPC title

• G01D5/34784

  with only analogue scales or both analogue and incremental scales · CPC title

• G01D5/24438 Primary

  Special design of the sensing element or scale · CPC title

• G01D5/36

  Forming the light into pulses · CPC title

• G01D5/341 Primary

  controlling the movement of a following part · CPC title