Optoelectronic harmonically filtered detector system for a scanning unit

• US 7,268,883 B2
• Filed: 05/03/2004
• Issued: 09/11/2007
• Est. Priority Date: 05/02/2003
• Status: Active Grant

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr. Johannes Heidenhain GmbH
• Inventors: Holzapfel, Wolfgang
• Primary Examiner(s): Turner; Samuel A.
• Application Number:
  US10/838,619
• Publication Number:
  US 20040218190A1
• Time in Patent Office: 1,226 Days
• Field of Search: 356/450, 356/498, 356/488, 356/494, 356/499, 250/231.13, 250/231.14
• US Class Current: 356/450
• CPC Class Codes: G01D 5/34715 Scale reading or illumination devices
• CPC Class Codes: G01D 5/366 Particular pulse shapes
• CPC Class Codes: G01D 5/38 by diffraction gratings

Abstract

An optoelectronic detector system is for generating a plurality of periodic, phase-shifted scanning signals from the scanning of a periodic fringe pattern. The fringe pattern extends in a detection plane with fringe-pattern period P in a fringe-displacement direction. The detector system is made up of a plurality of detector elements, the geometrical shape of the detector elements being selected such that a defined filtering of unwanted harmonics from the scanning signals thereby results. Within one fringe-pattern period P, a total of N detector elements of the same geometrical shape are arranged one immediately after the other in measuring direction x.

Claims

1. An optoelectronic detector system for generating a plurality of periodic, phase-shifted scanning signals from scanning of a periodic fringe pattern that extends in a detection plane with a fringe-pattern period in a fringe-displacement direction, comprising:

a plurality of detector elements, a geometrical form of individual detector elements adapted to provide a defined filter of unwanted harmonics from the scanning signal;

wherein in one fringe-pattern period, a total number of detector elements of a same non-rectangular geometrical form and of a same geometrical orientation are arranged one immediately after another in the fringe-displacement direction to provide a densest possible arrangement of the individual detector elements, wherein the detector elements are arranged successively such that one detector element is convertible into another detector element by a displacement transformation by a multiple of the fringe-pattern period divided by the total number of detector elements arranged within one fringe-pattern period.

2. The optoelectronic detector system according to claim 1, wherein adjacent detector elements contact each other along a shared contact line.

3. The optoelectronic detector system according to claim 2, wherein the contact lines form an angle with the fringe-displacement direction unequal to 90°

.

4. The optoelectronic detector system according to claim 2, wherein the detector elements have curved boundary lines in a region of longitudinal ends.

5. The optoelectronic detector system according to claim 1, wherein each detector element has a geometrical shape that deviates from a rectangle to filter at least one odd-order harmonic out of the scanning signals.

6. The optoelectronic detector system according to claim 1, wherein each detector element has a same width along a line of intersection parallel to the fringe-displacement direction.

7. The optoelectronic detector system according to claim 6,

wherein the width of each detector element along the line of intersection satisfies the following relationship:

b=P/N-e;

wherein b represents the width of one detector element along the line of intersection;

wherein P represents the fringe-pattern period;

wherein N represents the number of detector elements per fringe-pattern period; and

e represents a technology-dependent minimum distance of active detector-element areas.

8. The optoelectronic detector system according to claim 1, wherein the total number of detector elements within one fringe-pattern period is one of (a) four and (b) three.

9. The optoelectronic detector system according to claim 1, wherein the detector elements are configured to generate in-phase scanning signals from scanning of the fringe pattern and are electroconductively interconnected.

10. The optoelectronic detector system according to claim 1, wherein all of the detector elements have the same geometrical form.

11. An optoelectronic detector system for generating a plurality of periodic, phase-shifted scanning signals from scanning of a periodic fringe pattern that extends in a detection plane with a fringe-pattern period in a fringe-displacement direction, comprising:

a plurality of detector systems adjacently arranged in parallel, perpendicular to the fringe-displacement direction, each detector system including a plurality of detector elements, a geometrical form of individual detector elements adapted to provide a defined filter of unwanted harmonics from the scanning signal;

wherein in one fringe-pattern period, a total number of detector elements in each detector system of a same non-rectangular geometrical form and of a same geometrical orientation are arranged one immediately after another in the fringe-displacement direction to provide a densest possible arrangement of the individual detector elements, wherein the detector elements are arranged successively such that one detector element is convertible into another detector element by a displacement transformation by a multiple of the fringe-pattern period divided by the total number of detector elements arranged within one fringe-pattern period.

12. The optoelectronic detector system according to claim 11, wherein all of the detector elements have the same geometrical form.

13. A position-measuring device for determining a position of two objects movable relative to each other, comprising:

a measuring graduation extending in a measuring direction;

a scanning unit movable relative to the measuring graduation, the scanning unit including;

a light source; and

an optoelectronic detector system configured to generate a plurality of periodic, phase-shifted scanning signals from scanning of a periodic fringe pattern that extends in a detection plane with a fringe-pattern period in a fringe-displacement direction, the optoelectronic detector system including a plurality of detector elements, a geometrical form of individual detector elements adapted to provide a defined filter of unwanted harmonics from the scanning signal, in one fringe-pattern period, a total number of detector elements of a same non-rectangular geometrical form and of a same geometrical orientation arranged one immediately after another in the fringe-displacement direction to provide a densest possible arrangement of the individual detector elements, wherein the detector elements are arranged successively such that one detector element is convertible into another detector element by a displacement transformation by a multiple of the fringe-pattern period divided by the total number of detector elements arranged within one fringe-pattern period.

14. The position-measuring device according to claim 13, wherein the measuring direction extends along a straight line.

15. The position-measuring device according to claim 13, wherein the measuring direction extends along a circular path.

16. The position-measuring device according to claim 13, wherein all of the detector elements have the same geometrical form.