Process for determining the location of a positioning body in relation to a reference body and device for implementing the process

• US 5,598,268 A
• Filed: 03/03/1995
• Issued: 01/28/1997
• Est. Priority Date: 07/31/1992
• Status: Expired due to Fees

• Current Assignee: EMS Technik GmbH
• Original Assignee: EMS Technik GmbH
• Inventors: Kellner, Helmut
• Primary Examiner(s): Pham, Hoa Q.
• Application Number:
  US08/374,574
• Time in Patent Office: 697 Days
• Field of Search: 356/375, 356/373, 356/374, 356/399, 33/707, 250/237 G
• US Class Current: 356/620
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates

Abstract

The description relates to a process for determining the location of a positioning body in relation to a reference body and a device for implementing it. The positioning body (10) bears a scale with evenly spaced markings and the reference body comprises a scanner (12) with a projection surface on which the mark (16) of the scale are projected and imaging optics. The coordinates of the center of projection of the imaging optics are calculated by evaluating the mark (16) arranged on the scale. Here, coded marks of two perpendicular surface scales of the scale or the positioning body are decoded and at least four centers of intersection regions of the marks of both surface scales confining an area are determined. The calculation is made via the protective relationship between the projection surface of the scanner and the plane of the scale bearing the marks.

Claims

1. A process for determining a location of a positioning body in relation to a reference body, said process comprising the steps of:

providing on a positioning body a scale with marks of known coordinates in a plane;

providing a scanner on the reference body, the scanner including a projection surface, on which the marks of a scale are projected, and an imaging lens;

calculating coordinates of a center of projection of the imaging lens from the known coordinates of the marks on the scale via a projecting relationship between the projection surface of the scanner and the plane of the scale, whereby the marks provide their coordinate information with respect to the scale in coded form and are decoded for the calculation,

wherein the scale comprises two orthogonal surface scales;

wherein the marks of both surface scales form intersection regions; and

wherein the calculation is based on at least four centers of intersection regions of the marks of both surface scales defining an area as the known coordinates of the marks.

2. A process as claimed in claim 1, wherein the calculating step calculates the coordinates based on more than four centers of the intersection regions of the marks of both surface scales and further comprises the step of performing a balancing calculation according to a Gaussian curve.

3. A process as claimed in claim 2, wherein the intersection regions of the marks are reproduced exclusively on the scanner.

4. A process as claimed in claim 3, wherein the calculating step includes evaluating the intersection regions of the marks separately according to a direction of the coordinates by determining according to a process of edge division an absolute frequency of brightness values of the intersection regions of the marks in directions of columns and lines of light-sensitive pixels of the scanner and by comparing with a threshold value;

wherein absolute values above the threshold value are determined to be coordinates occupied by the marks.

5. A process as claimed in claim 3, further comprising the step of determining centers of the intersection regions of the marks by forming an average value in both coordinate directions, by selecting the respective pixel fields of the scanner as search fields and by determining in each search field the coordinates of the center XS and YS according to the following equations:

##EQU5## where NLok are the number of points in the pixel field.

6. A process as claimed in claim 1, wherein the intersection region of the marks are reproduced exclusively on the scanner.

7. A process as claimed in claim 6, wherein the calculating step includes evaluating the intersection regions of the marks separately according to a direction of the coordinates by determining according to a process of edge division an absolute frequency of brightness values of the intersection regions of the marks in directions of columns and lines of light-sensitive pixels of the scanner and by comparing with a threshold value;

wherein absolute values above the threshold value are determined to be coordinates occupied by the marks.

8. A process as claimed in claim 7, further comprising the step of determining centers of the intersection regions of the marks by forming an average value in both coordinate directions, by selecting the respective pixel fields of the scanner as search fields and by determining in each search field the coordinates of the center XS and YS according to the following equations:

##EQU6## where NLok are the number of points in the pixel field.

9. A process as claimed in claim 6, further comprising the step of determining centers of the intersection regions of the marks by forming an average value in both coordinate directions, by selecting the respective pixel fields of the scanner as search fields and by determining in each search field the coordinates of the center XS and YS according to the following equations:

##EQU7## where NLok are the number of points in the pixel field.

10. A process for determining a location of a positioning body in relation to a reference body, said process comprising the steps of:

providing on a the positioning body a scale with marks of known coordinates in a plane;

providing a scanner on the reference body, the scanner including a projection surface, on which the marks of a scale are projected, and an imaging lens;

calculating coordinates of a center of projection of the imaging lens from the known coordinates of the marks on the scale via a projecting relationship between the projection surface of the scanner and the plane of the scale, where by the marks provide their coordinate information with respect to the scale in coded form and are decoded for the calculation,

wherein the scale comprises two orthogonal surface scales;

wherein the marks of both surface scales form intersection regions;

wherein the calculation is based on at least four centers of intersection regions of the marks of both surface scales defining an area as the known coordinates of the marks; and

wherein said calculating step includes calculating in three dimensions coordinates XO, YO, ZO of the center of projection and angles of orientation K, φ

, ω

between the projection surface of the scanner and the plane of the scale are calculated according to the following functions and equations;

##EQU8## where K denotes an angle of orientation relative to the Z axis;

φ

denotes an angle of orientation relative to the Y axis;

ω

denotes an angle of orientation relative to the X axis;

c denotes a chamber constant in accordance with the distance between the center of projection O and the vertical base point H'"'"' of the reference body;

δ and

γ

denote transformation variables; and

a1, a2, a3, b3, c1, c2 represent the transformation constants.

11. A process as claimed in claim 10, wherein the calculating step calculates the coordinates based on more than four centers of the intersection regions of the marks of both surface scales and further comprises the step of performing a balancing calculation according to a Gaussian curve.

12. A process as claimed in claim 11, wherein the intersection regions of the marks are reproduced exclusively on the scanner.

13. A process as claimed in claim 12, wherein the calculating step includes evaluating the intersection regions of the marks separately according to a direction of the coordinates by determining according to a process of edge division an absolute frequency of brightness values of the intersection regions of the marks in directions of columns and lines of light-sensitive pixels of the scanner and by comparing with a threshold value;

wherein absolute values above the threshold value are determined to be coordinates occupied by the marks.

14. A process as claimed in claim 12, further comprising the step of determining centers of the intersection regions of the marks by forming an average value in both coordinate directions, by selecting the respective pixel fields of the scanner as search fields and by determining in each search field the coordinates of the center XS and YS according to the following equations:

##EQU9## where NLok are the number of points in the pixel field.

15. A process as claimed in claim 10, wherein the intersection regions of the marks are reproduced exclusively on the scanner.

16. A process as claimed in claim 15, wherein the calculating step includes evaluating the intersection regions of the marks separately according to a direction of the coordinates by determining according to a process of edge division an absolute frequency of brightness values of the intersection regions of the marks in directions of columns and lines of light-sensitive pixels of the scanner and by comparing with a threshold value;

wherein absolute values above the threshold value are determined to be coordinates occupied by the marks.

17. A process as claimed in claim 16, further comprising the step of determining centers of the intersection regions of the marks by forming an average value in both coordinate directions, by selecting the respective pixel fields of the scanner as search fields and by determining in each search field the coordinates of the center XS and YS according to the following equations:

##EQU10## where NLok are the number of points in the pixel field.

18. A process as claimed in claim 15, further comprising the step of determining centers of the intersection regions of the marks by forming an average value in both coordinate directions, by selecting the respective pixel fields of the scanner as search fields and by determining in each search field the coordinates of the center XS and YS according to the following equations:

##EQU11## where NLok are the number of points in the pixel field.

19. A device for determining the location of a positioning body in relation to a reference body, comprising:

a positioning body bearing a scale including two orthogonal surface scales with marks of known coordinates on a plane on which the marks of both surface scales form intersection regions;

a reference body including a scanner with a projection surface, on which the marks of the scale are projected, and an imaging lens; and

a computer calculating coordinates of a center of projection of the imaging lens from the known coordinates of the marks on the scale via a projecting relationship between the projection surface of the scanner and the plane of the scale, whereby the marks provide their coordinate information with respect to the scale in coded form and are decoded for the calculation, and

wherein of respective intersection regions of the marks of both surface scales defining an area as the known coordinates of the marks.

20. A device as claimed in claim 19, wherein the intersection regions of the marks of both surface are present exclusively on the plane of the scale bearing the marks.