Instrument for producing harmonics-free periodic signals

• US 5,332,896 A
• Filed: 11/04/1992
• Issued: 07/26/1994
• Est. Priority Date: 11/04/1991
• Status: Expired due to Fees

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr. Johannes Heidenhain GmbH
• Inventors: Holzapfel, Wolfgang
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): DAVENPORT, TERESA
• Application Number:
  US07/884,484
• Time in Patent Office: 629 Days
• Field of Search: 250/237 G, 250/227.11, 250/559, 250/560, 250/550, 250/231.16, 356/334, 356/395
• US Class Current: 250/237.00G
• CPC Class Codes: G01D 5/2457 Incremental encoders having reference marks
• CPC Class Codes: G01D 5/366 Particular pulse shapes

Abstract

An instrument for obtaining harmonics-free signals with the aid of a periodic measurement graduation and a nonperiodic scanning graduation, wherein the centers of scanning graduation markings are staggered in accordance with a modified arcsin function.

Claims

1. An instrument for obtaining harmonics-free signals up to a predeterminable bandwidth, comprising:

a periodic measurement graduation comprising a plurality of periodically spaced measurement graduation markings;

a scanning graduation comprising one or more scanning graduation markings which are offset from one another nonperiodically, such that the spacing of the scanning graduation marking centers is staggered by a modified arcsin function.

2. The instrument of claim 1, wherein said scanning graduation markings have the same width.

3. The instrument of claim 1, comprising a scanning unit to move said scanning graduation relative to said measurement graduation along a scanning direction X.

4. The instrument of claim 1, wherein said scanning graduation marking centers are offset from a corresponding measurement graduation marking center by an amount determined by a modified arcsin function.

5. The instrument of claim 3, wherein said scanning graduation marking centers are offset along said scanning direction X from a corresponding measurement graduation marking center by an amount determined by a modified arcsin function.

6. The instrument of claim 5, wherein the nth scanning graduation marking center is offset along said scanning direction X by an amount δ

_n which is determined by the formula;

space="preserve" listing-type="equation">n/2N=δ

.sub.n /P+1/2π

* sin(2π

δ

.sub.n /P)

wherein n=-N to +N, +-N=the maximum number of markings located to the left (-) or right (+) of the central marking denoted n=0) , and P is the period of said measurement graduation.

7. The instrument of claim 5, wherein the nth scanning graduation marking center is offset along said scanning direction X by an amount δ

_n which is determined by the formula;

space="preserve" listing-type="equation">n/2N=δ

.sub.n /P+1/4π

* sin(4π

δ

.sub.n /P)

wherein n=-N to +N, +-N=the maximum number of markings located to the left (-) or right (+) of the central marking denoted n=0) , and P is the period of said measurement graduation.

8. An instrument for obtaining harmonics-free signals up to a predeterminable bandwidth, comprising:

a periodic measurement graduation comprising a plurality of periodically spaced measurement graduation markings;

a scanning graduation comprising one or more scanning graduation markings which are shaped in accordance with a modified arcsin function.

9. The instrument of claim 8, wherein said scanning graduation markings are periodically spaced from one another.

10. The instrument of claim 8, comprising a scanning unit to move said scanning graduation relative to said measurement graduation along a scanning direction X.

11. The instrument of claim 10, wherein said scanning graduation markings are periodically spaced from one another along said scanning direction X.

12. The instrument of claim 9, wherein said period of spacing of said scanning graduation markings corresponds to the period of spacing of said measurement graduation markings.

13. The instrument of claim 11, wherein said period of spacing of said scanning graduation markings corresponds to the period of spacing of said measurement graduation markings.

14. The instrument of claim 11, wherein each scanning graduation marking has a shape determined by the term δ

(Y) which corresponds to the distance an edge of said scanning graduation marking is from a Y axis which

     1) is perpendicular to an X axis which bisects said scanning graduation along the measurement direction and

     2) is located at each point of said scanning graduation marking which intersects said X axis, and wherein δ

(Y) is determined by the formula;

space="preserve" listing-type="equation">Y/H=δ

(Y)/P+1/2π

* sin(2π

δ

(Y)/P)

wherein Y is the position along the Y axis at which distance δ

(Y) is to be determined, H is the width of said scanning graduation as measured along the Y direction, and P is the period of said measurement graduation.

15. The instrument of claim 11, wherein each scanning graduation marking has a shape determined by the term δ

(Y) which corresponds to the distance an edge of said scanning graduation marking is from a Y axis which

     1) is perpendicular to an X axis which bisects said scanning graduation along the measurement direction and

     2) is located at each point of said scanning graduation marking which intersects said X axis, and wherein δ

(Y) is determined by the formula;

space="preserve" listing-type="equation">Y/H=δ

(Y)/P+1/2π

* sin(4π

δ

(Y)/P)

wherein Y is the position along the Y axis at which distance δ

(Y) is to be determined, H is the width of said scanning graduation as measured along the Y direction, and P is the period of said measurement graduation.