Multiple measuring point configuration for a chromatic point sensor

• US 8,456,637 B2
• Filed: 08/26/2010
• Issued: 06/04/2013
• Est. Priority Date: 08/26/2010
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Emtman, Casey Edward, Xie, Yong
• Primary Examiner(s): Toatley, Gregory J
• Assistant Examiner(s): Valentin, II, Juan D
• Application Number:
  US12/869,687
• Publication Number:
  US 20120050722A1
• Time in Patent Office: 1,013 Days
• Field of Search: None
• US Class Current: 356/445
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01B 2290/20 Dispersive element for generating dispersion

Abstract

A dual beam assembly is provided for attachment to a chromatic confocal point sensor optical pen. The optical pen provides a single source beam having a measurement range R in the absence of the dual beam assembly. The dual beam assembly includes a first reflective element that is positioned in the source beam and divides it into a first measurement beam and a second measurement beam. The dual beam assembly outputs the first and second measurement beams along first and second measurement axes to different workpiece regions and returns workpiece measurement light arising from the first and second measurement beams back to the optical pen. A second reflective element may be included and configured to deflect the second measurement beam along a desired direction. An offset may be provided between the measuring ranges of the first and second measurement beams.

Claims

1. A dual beam assembly to be attached to a chromatic confocal point sensor pen which provides a single source beam having a measurement range R in the absence of the dual beam assembly, the dual beam assembly comprising:

a mounting element configured to be attached to the chromatic confocal point sensor pen; and

a first reflective element,

wherein;

the dual beam assembly is configured such that when the mounting element is operably attached to the chromatic confocal point sensor pen;

the first reflective element is positioned in the source beam and divides the source beam into a first measurement beam and a second measurement beam; and

the dual beam assembly outputs the first and second measurement beams to different workpiece portions along first and second measurement axes, and returns workpiece measurement light arising from the first and second measurement beams back to the chromatic confocal point sensor pen; and

the first reflective element comprises one of;

a pattern of reflective regions and transmissive regions that divides the source beam; and

a prismatic element which includes at least one partially reflective and partially transmissive surface that divides the source beam.

2. The dual beam assembly of claim 1, wherein the reflective regions comprise planar surface reflective mirror regions, and the transmissive regions are open holes.

3. The dual beam assembly of claim 1, wherein the reflective regions have a total reflective area in the source beam and the transmissive regions have total transmissive area in the source beam, and the total reflective area is within +/−

25% of the total transmissive area.

4. The dual beam assembly of claim 1, wherein the pattern of the first reflective element has reflective symmetry across its center.

5. The dual beam assembly of claim 1, further comprising a second reflective element configured to deflect the second measurement beam along the second measurement axis.

6. The dual beam assembly of claim 5, wherein the second reflective element comprises a planar first surface reflective mirror.

7. The dual beam assembly of claim 5, wherein:

the first reflective element includes a first planar reflective surface that is configured to divide the source beam and the second reflective element comprises a second planar reflective surface that is configured to deflect the second measurement beam; and

the dual beam assembly is configured such that the planar reflective surfaces of the first and second reflective elements are parallel to one another.

8. The dual beam assembly of claim 5, wherein:

the first reflective element includes a first planar reflective surface that is configured to divide the source beam and the second reflective element comprises a second planar reflective surface that is configured to deflect the second measurement beam; and

the dual beam assembly is configured such that the planar reflective surfaces of the first and second reflective elements are orthogonal to one another and arranged such that the first and second measurement axes are parallel to one another and facing in opposite directions.

9. The dual beam assembly of claim 8, wherein the dual beam assembly is configured such that the first measurement axis is perpendicular to an optical axis of the chromatic confocal point sensor pen and the second measurement axis is parallel to the first measurement axis.

10. The dual beam assembly of claim 5, wherein the dual beam assembly is configured such that the first and second measurement axes are transverse to an optical axis of the chromatic confocal point sensor pen.

11. The dual beam assembly of claim 1, wherein the mounting element includes at least one external alignment surface that is one of parallel to and orthogonal to one of the first and second measurement axes.

12. The dual beam assembly of claim 1, wherein the mounting element includes an interface surface configured such that when it abuts an interface surface of the chromatic confocal point sensor pen, at least one of the first and second measurement axes is one of parallel to and orthogonal to an optical axis of the chromatic confocal point sensor pen.

13. The dual beam assembly of claim 1, wherein the second measurement axis is transverse to the first measurement axis.

14. The dual beam assembly of claim 5, wherein:

the first reflective element includes a first planar reflective surface that is configured to divide the source beam and the second reflective element comprises a second planar reflective surface that is configured to deflect the second measurement beam; and

a distance SEPP between the reflecting surfaces of the first and second reflecting elements along the second measurement beam is less than a maximum focus distance MF of the chromatic confocal point sensor pen.

15. The dual beam assembly of claim 14, wherein the distance SEPP is less than the measurement range R.

16. The dual beam assembly of claim 14, wherein the distance SEPP is at least the measurement range R.

17. The dual beam assembly of claim 1, wherein the dual beam assembly comprises at least one of:

(a) an adjustable mount for positioning the first reflective element relative to the mounting element such that a reflecting plane of the first reflective element is adjustably positioned along an axis of the source beam; and

(b) an adjustable mounting arrangement for positioning the mounting element relative to the chromatic confocal point sensor pen such that a reflecting plane of the first reflective element is adjustably positioned along an axis of the source beam.

18. The dual beam assembly of claim 5, wherein the dual beam assembly comprises an adjustable mounting arrangement for positioning the second reflective element relative to the first mounting element such that a reflecting plane of the second reflective element is adjustably positioned along an axis of the second measurement beam.

19. The dual beam assembly of claim 1, wherein at least one of the dual beam assembly and the chromatic confocal point sensor pen further comprises a single confocal aperture which provides dual signals to a spectrometer.

20. The dual beam assembly of claim 1, wherein:

the first reflective element comprises a pattern of reflective regions and transmissive regions,

the reflective regions have a total reflective area in the source beam and the transmissive regions have total transmissive area in the source beam, and

the total reflective area has a difference of at least +/−

5% from the total transmissive area.

21. The dual beam assembly of claim 1, wherein:

a fixed Z offset exists with respect to a measurement range R1 of the first measurement beam and a measurement range R2 of the second measurement beam,

the dual beam assembly is configured to be able to measure a nominal step height of a specified dimension, and

the difference between the fixed Z offset and the nominal step height is greater than 5% of the measurement range R.

22. The dual beam assembly of claim 1, wherein the first and second measurement axes are not coincident.

23. A dual beam assembly to be attached to a chromatic confocal point sensor pen that provides a single source beam having a measurement range R in the absence of the dual beam assembly, the dual beam assembly comprising:

a mounting element configured to be attached to the chromatic confocal point sensor pen; and

a first reflective element,

wherein the dual beam assembly is configured such that when the mounting element is operably attached to the chromatic confocal point sensor pen;

the first reflective element is positioned in the source beam and divides the source beam into a first measurement beam and a second measurement beam; and

the dual beam assembly outputs the first and second measurement beams to different workpiece portions along first and second measurement axes, and returns workpiece measurement light arising from the first and second measurement beams back to the chromatic confocal point sensor pen, and

wherein the second measurement axis is transverse to the first measurement axis.

24. A dual beam assembly to be attached to a chromatic confocal point sensor pen that provides a single source beam having a measurement range R in the absence of the dual beam assembly, the dual beam assembly comprising:

a mounting element configured to be attached to the chromatic confocal point sensor pen;

a first reflective element; and

a second reflective element,

wherein the dual beam assembly is configured such that when the mounting element is operably attached to the chromatic confocal point sensor pen;

the first reflective element is positioned in the source beam and divides the source beam into a first measurement beam and a second measurement beam; and

the dual beam assembly outputs the first and second measurement beams to different workpiece portions along first and second measurement axes, and returns workpiece measurement light arising from the first and second measurement beams back to the chromatic confocal point sensor pen,

wherein the second reflective element is configured to deflect the second measurement beam along the second measurement axis, and

wherein the dual beam assembly comprises an adjustable mounting arrangement for positioning the second reflective element relative to the first mounting element such that a reflecting plane of the second reflective element is adjustably positioned along an axis of the second measurement beam.