Non-contact probe

• US 8,605,983 B2
• Filed: 08/15/2008
• Issued: 12/10/2013
• Est. Priority Date: 08/17/2007
• Status: Expired

• Current Assignee: Renishaw PLC
• Original Assignee: Renishaw PLC
• Inventors: Weston, Nicholas John, Huddart, Yvonne Ruth
• Primary Examiner(s): Werner, Brian P
• Assistant Examiner(s): Dunphy, David F
• Application Number:
  US12/733,021
• Publication Number:
  US 20100135534A1
• Time in Patent Office: 1,943 Days
• Field of Search: None
• US Class Current: 382/141
• CPC Class Codes: G01B 11/007 feeler heads therefor
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01B 11/2527 with phase change by in-plane movement of the patern
• CPC Class Codes: G06T 2207/30164 Workpiece; Machine component
• CPC Class Codes: G06T 7/0004 Industrial image inspection
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• CPC Class Codes: G06T 7/593 from stereo images

Abstract

A non-contact measurement apparatus and method. A probe is provided for mounting on a coordinate positioning apparatus, comprising at least one imaging device for capturing an image of an object to be measured. Also provided is an image analyzer configured to analyze at least one first image of an object obtained by the probe from a first perspective and at least one second image of the object obtained by the probe from a second perspective so as to identify at least one target feature on the object to be measured. The image analyzer is further configured to obtain topographical data regarding a surface of the object via analysis of an image, obtained by the probe, of the object on which an optical pattern is projected.

Claims

1. A non-contact measurement apparatus, comprising:

a probe configured to be mounted on a coordinate positioning apparatus, comprising an imaging device for capturing an image of an object to be measured;

a processor configured to;

a) analyse at least one first image of an object obtained by the imaging device from a first perspective and at least one second image of the object obtained by the imaging device, which is the same imaging device used to obtain the at least one first image of the object, from a second perspective so as to identify in each of the at least one first image and the at least one second image of the object at least one common photogrammetric target feature on the object to be measured, determine the two-dimensional coordinates of the at least one common photogrammetric target feature on the object within each image, and then, based on knowledge of the relative location and orientation of the imaging device that took the images, determine the three dimensional coordinates of the at least one common photogrammetric target feature; and

b) obtain topographical data regarding a form of a surface of the object via analysis of the distortion of a structured light pattern projected on the object caused by height variation on the surface of the object as imaged in at least one image, obtained by the imaging device, which is the same imaging device used to obtain the at least one first image and the at least one second image of the object,

wherein the non-contact measurement apparatus being further configured to use both the data obtained from a) and b) to provide a 3D point cloud that describes the shape of the object.

2. A non-contact measurement apparatus as claimed in claim 1, in which the probe comprises at least one projector for projecting an optical pattern onto the surface of the object to be measured.

3. A non-contact measurement apparatus as claimed in claim 1, in which the processor is configured to obtain the topographical data regarding the surface of the object via analysis of at least one of the at least one first image and the at least one second image.

4. A non-contact measurement apparatus as claimed in claim 1, in which the processor is configured to process a set of images in which the position of an optical pattern on the object is different for each image in the set in order to determine the topographical data.

5. A non-contact measurement apparatus as claimed in claim 1, in which the processor is configured to identify an irregularity in an optical pattern projected on the object in each of the first and second images as the at least one target feature.

6. A non-contact measurement apparatus as claimed in claim 5, in which the processor is configured to process:

a set of first images obtained by the imaging device from the first perspective, the position of an optical pattern projected onto the object being different for each image in the set; and

a set of second images obtained by the imaging device from the second perspective, the position of an optical pattern projected onto the object being different for each image in the set,

in order to identify at least one target feature on the object to be measured and to determine the position of the target feature on the object relative to the image sensor.

7. A non-contact measurement apparatus as claimed in claim 6, in which the processor is configured to process at least one of the first or second sets of images in order to determine the topographical data.

8. A non-contact measurement apparatus as claimed in claim 7, in which the processor is configured to calculate at least one of a first phase map from the set of first images and a second phase map from the set of second images.

9. A non-contact measurement apparatus as claimed in claim 8, in which the processor is configured to determine the topographical data from at least one of the at least one first phase map and second phase map.

10. A non-contact measurement apparatus as claimed in claim 2, in which the projector has a fixed optical pattern.

11. A device for use in a non-contact measurement apparatus that includes a probe that is configured to be mounted on a coordinate positioning apparatus, having an imaging device for capturing an image of an object to be measured, the device comprising:

a processor configured to;

a) analyse at least one first image of an object obtained by the imaging device from a first perspective and at least one second image of the object obtained by the imaging device, which is the same imaging device used to obtain the at least one first image of the object, from a second perspective so as to identify in each of the at least one first image and the at least one second image of the object at least one common photogrammetric target feature on the object to be measured, determine the two-dimensional coordinates of the at least one common photogrammetric target feature on the object within each image, and then, based on knowledge of the relative location and orientation of the imaging device that took the images, determine the three dimensional coordinates of the at least one common photogrammetric target feature; and

b) obtain topographical data regarding a form of a surface of the object via analysis of the distortion of a structured light pattern projected on the object caused by height variation on the surface of the object as imaged in at least one image, obtained by the imaging device, which is the same imaging device used to obtain the at least one first image and the at least one second image of the object,

wherein the device being further configured to use both the data obtained from a) and b) to provide a 3D point cloud that describes the shape of the object.

12. A non-contact method for measuring an object located within a measurement space using a probe comprising an imaging device, the method comprising:

a) analysing at least one first image of an object obtained by the imaging device from a first perspective and at least one second image of the object obtained by the imaging device, which is the same imaging device used to obtain the at least one first image of the object, from a second perspective so as to identify in each of the at least one first image and the at least one second image of the object at least one common photogrammetric target feature on the object to be measured, determining the two-dimensional coordinates of the at least one common photogrammetric target feature on the object within each image, and then, based on knowledge of the relative location and orientation of the imaging device that took the images, determining the three dimensional coordinates of the at least one common photogrammetric target feature; and

b) obtaining topographical data regarding a form of a surface of the object via analysis of the distortion of a structured light pattern projected on the object caused by height variation on the surface of the object as imaged in at least one image, obtained by the imaging device, which is the same imaging device used to obtain the at least one first image and the at least one second image of the object,

wherein both the data obtained from a) and b) is used to provide a 3Dpoint cloud that describes the shape of the object.

13. A method as claimed in claim 12, in which at least one of the at least one first image of the object from the first perspective and at least one second image of the object from the second perspective comprises the at least one image of the object on which an optical pattern is projected.

14. A method as claimed in claim 12 in which the method comprises relatively moving the object and the imaging device between the first and second perspectives.

15. A method as claimed in claim 12 in which the probe comprises a projector for projecting an optical pattern.

16. A memory and a processor, the memory storing instructions which, when executed by the processor, cause the processor to control the probe comprising the imaging device in accordance with the method of claim 12.

17. A non-transitory computer readable medium storing instructions, which when executed, perform the method of claim 12.