Optical measurement of workpiece surface using sharpness maps

Patent metadata

Field	Value
Publication number	US-12555221-B2
Application number	US-202217736878-A
Country	US
Kind code	B2
Filing date	May 4, 2022
Priority date	May 5, 2021
Publication date	Feb 17, 2026
Grant date	Feb 17, 2026

Abstract

A method includes capturing images of a surface of a workpiece using an optical sensor. Each image respectively images a region of the surface. Each image is assigned a defined 6-DOF pose of the optical sensor relative to the workpiece and a defined focal plane position of the optical sensor. The captured images form an image stack. The method includes determining a sharpness value for each picture element of each image of the image stack to generate a sharpness map for each image. The sharpness maps of the images form a sharpness map stack. The method includes transforming the sharpness maps of the sharpness map stack into a defined reference system based on the respective assigned 6-DOF pose and focal plane position of the optical sensor in order to generate a sharpness cloud. The method includes generating a surface profile of the workpiece based on the sharpness cloud.

First claim

The invention claimed is:

1 . A method for measuring a surface of a workpiece using an optical sensor of a measuring apparatus, the method comprising:
capturing a plurality of images of the surface of the workpiece using the optical sensor, wherein each image respectively images a region of the surface of the workpiece, wherein each image is assigned a defined 6-DOF pose of the optical sensor relative to the workpiece and a defined focal plane position of the optical sensor, and wherein the captured images form an image stack; determining a sharpness value for each picture element of each image of the image stack in order to generate a sharpness map for each image of the image stack, wherein each sharpness map includes the determined sharpness value of each picture element of the respective image, and wherein the sharpness maps of the images form a sharpness map stack; transforming the sharpness maps of the sharpness map stack into a defined reference system based on the respective assigned 6-DOF pose and focal plane position of the optical sensor in order to generate a sharpness cloud, wherein the sharpness cloud includes the determined sharpness value of each picture element of each image of the plurality of images, wherein the sharpness cloud forms a three-dimensional scalar field that assigns each determined sharpness value to a respective point in a space of the defined reference system; and generating a surface profile of the workpiece based on local sharpness maxima of the sharpness cloud, wherein the generating includes determining local sharpness maxima of the sharpness cloud by analyzing the sharpness cloud, and wherein each local sharpness maximum of the local sharpness maxima represents a surface point of the workpiece.

2 . The method of claim 1 further comprising arranging the workpiece on a workpiece holder.

3 . The method of claim 1 further comprising moving the optical sensor and the workpiece relative to one another during the capturing in order to change the 6-DOF pose of the optical sensor in space relative to the workpiece.

4 . The method of claim 3 wherein a drive device of the measuring apparatus is used to move at least one of the optical sensor and a workpiece holder.

5 . The method of claim 3 wherein the moving includes moving the optical sensor in translational fashion, laterally in relation to the workpiece.

6 . The method of claim 3 wherein:
the moving includes moving the optical sensor in rotational fashion; and
the rotational fashion includes at least one of tilting and turning.

7 . The method of claim 3 wherein the moving includes moving the optical sensor along a predefined trajectory.

8 . The method of claim 3 wherein:
the capturing is performed while the optical sensor and the workpiece are moved relative to one another; and
each image is assigned a different, defined 6-DOF pose of the optical sensor.

9 . The method of claim 1 further comprising:
changing the focal plane position of the optical sensor during the capturing,
wherein the capturing is performed while the focal plane position of the optical sensor is changed, and
wherein each image is assigned a different, defined focal plane position of the optical sensor.

10 . The method of claim 1 further comprising:
determining the 6-DOF pose and/or the focal plane position of the optical sensor while an image is being captured by the optical sensor,
wherein the determined 6-DOF pose and/or the determined focal plane position are assigned to the captured image.

11 . The method of claim 1 wherein the sharpness value of each picture element is determined based on a sharpness of the picture element.

12 . The method of claim 1 wherein:
the generating includes segmenting the sharpness cloud, with the sharpness cloud being filtered based on a sharpness threshold method, and
the local sharpness maxima are determined based on the segmented sharpness cloud.

13 . The method of claim 1 wherein:
the generating includes determining one or more areas of maximum sharpness of the sharpness cloud; and
the areas of maximum sharpness represent the surface of the workpiece.

14 . The method of claim 1 further comprising applying a moving least squares method to the sharpness cloud to generate the surface profile.

15 . The method of claim 14 wherein sharpness values are used as weighting factors.

16 . The method of claim 1 wherein defined geometries are fitted to the sharpness cloud to generate the surface profile.

17 . The method of claim 16 wherein the geometries are fitted using a weighted least squares method.

18 . The method of claim 1 wherein a neural network trained to generate the surface profile based on the sharpness cloud is used to generate the surface profile.

19 . The method of claim 1 further comprising outputting the surface profile by an output device.

20 . The method of claim 12 further comprising applying a moving least squares method to the segmented sharpness cloud to generate the surface profile.

21 . The method of claim 20 wherein sharpness values are used as weighting factors.

22 . The method of claim 12 wherein defined geometries are fitted to the segmented sharpness cloud to generate the surface profile.

23 . The method of claim 22 wherein the geometries are fitted using a weighted least squares method.

24 . The method of claim 12 wherein a neural network trained to generate the surface profile based on the segmented sharpness cloud is used to generate the surface profile.

25 . A measuring apparatus for measuring a surface of a workpiece, the measuring apparatus comprising:
an optical sensor configured to image the surface of the workpiece; and a control device configured to: capture a plurality of images of the surface of the workpiece using the optical sensor, wherein each image respectively images a region of the surface of the workpiece, wherein each image is assigned a defined 6-DOF pose of the optical sensor and a defined focal plane position of the optical sensor, and wherein the captured images form an image stack; determine a sharpness value for each picture element of each image of the image stack in order to generate a sharpness map for each image of the image stack, wherein each sharpness map includes the determined sharpness value of each picture element of the respective image, and wherein the sharpness maps of the images form a sharpness map stack; transform the sharpness maps of the sharpness map stack into a defined reference system based on the respective assigned 6-DOF pose and focal plane position of the optical sensor to generate a sharpness cloud, wherein the sharpness cloud includes the determined sharpness value of each picture element of each image of the plurality of images, wherein the sharpness cloud forms a three-dimensional scalar field that assigns each determined sharpness value to a respective point in a space of the defined reference system; and generate a surface profile of the workpiece based on local sharpness maxima of the sharpness cloud by analyzing the sharpness cloud, wherein the generating includes determining local sharpness maxima of the sharpness cloud, and wherein each local sharpness maximum of the local sharpness maxima represents a surface point of the workpiece.

26 . The measuring apparatus of claim 25 further comprising a workpiece holder configure

Assignees

• Zeiss Carl Industrielle Messtechnik Gmbh

Inventors

• Baum Michael

Classifications

• G06T2207/30164

  Workpiece; Machine component · CPC title

• G06T2207/20081

  Training; Learning · CPC title

• G06T2207/20084

  Artificial neural networks [ANN] · CPC title

• G06T7/001 Primary

  using an image reference approach · CPC title

• G06T7/55 Primary

  from multiple images · CPC title