Auto calibration from epipolar line distance in projection pattern

Patent metadata

Field	Value
Publication number	US-12087003-B2
Application number	US-202318363420-A
Country	US
Kind code	B2
Filing date	Aug 1, 2023
Priority date	May 31, 2021
Publication date	Sep 10, 2024
Grant date	Sep 10, 2024

Abstract

A detector for determining a position of at least one object, the detector including:at least one projector for illuminating the object with at least one illumination pattern;at least one sensor element having a matrix of optical sensors; andat least one evaluation device configured for determining initial distance information of reflection features by analysis of their respective beam profiles, where the evaluation device is configured for performing a calibration method.

First claim

The invention claimed is:

1. A detector for determining a position of at least one object, the detector comprising:
at least one projector for illuminating the object with at least one illumination pattern, wherein the illumination pattern comprises a plurality of illumination features;
at least one sensor element having a matrix of optical sensors, the optical sensors each having a light-sensitive area, wherein each optical sensor is designed to generate at least one sensor signal in response to an illumination of its respective light-sensitive area by a reflection light beam propagating from the object to the detector, wherein the sensor element is configured to determine at least one reflection image comprising a plurality of reflection features, wherein each of the reflection features comprises a beam profile; and
at least one evaluation device configured for determining initial distance information of the reflection features by analysis of their respective beam profiles, wherein the analysis of a beam profile comprises evaluating a combined signal Q from the at least one sensor signal, wherein the evaluation device is configured for performing a calibration method comprising:
a) matching the reflection features to reference features of a reference image using the initial distance information thereby determining pairs of matched reflection and reference features;
b) determining an epipolar line of the matched reference feature in the reference image for each of the pairs of matched reflection and reference features;
c) determining an epipolar line distance d of a center of the matched reflection feature to said epipolar line;
d) evaluating the epipolar line distances d as a function of an image position (x,y) in the reference image thereby determining a geometric pattern; and
e) determining at least one correction for rotation and/or translation of the reflection image depending on the geometric pattern.

2. The detector according to claim 1 , wherein the evaluation device is configured for correcting the reflection image based on the determined correction.

3. The detector according to claim 1 , wherein the evaluation device is configured for determining at least one triangulation distance information of the reflection feature by using triangulation considering the determined correction.

4. The detector according to claim 1 , wherein the evaluation device is configured for performing the calibration method on the fly during determining the triangulation distance information.

5. The detector according to claim 1 , wherein the evaluation device is configured for determining at least one extrinsic parameter of the detector, wherein the extrinsic parameter comprise at least one parameter selected from the group consisting of: rotation angles between the projector and coordinates of the sensor element, translation components between the projector and coordinates of the sensor element, aperture angles, center of the sensor element, apertures, focal distance.

6. The detector according to claim 1 , wherein the evaluation device is configured for performing steps b) to e) even if also false pairs of matched reflection and reference features are determined.

7. The detector according to claim 1 , wherein the evaluation device is configured for determining the correction of the reflection image by evaluating one or more of shape, repetitions, steepness, discontinuities, and curvatures of the geometric pattern.

8. The detector according to claim 1 , wherein the illumination pattern comprises at least one periodic regular pattern selected from the group consisting of: at least one periodic regular point pattern; at least one hexagonal pattern; at least one rectangular pattern.

9. The detector according to claim 8 , wherein the projector is configured for generating a cloud of points such that the illumination pattern comprises a plurality of point features.

10. The detector according to claim 1 , wherein the light beam may have a non-Gaussian beam profile.

11. The detector according to claim 1 , wherein the projector is configured to generate two or more illumination patterns each comprising a plurality of illumination features.

12. The detector according to claim 1 , wherein the projector comprises a diffractive optical element.

13. The detector according to claim 10 , wherein the diffractive optical element for diffracting and replicating the light beam.

14. The detector according to claim 1 , wherein the projector comprises an array of laser sources.

15. The detector according to claim 1 , wherein the optical sensors are sensitive in the range of 780 nm to 3.0 micrometers.

16. The detector according to claim 14 , wherein the projector comprises an array of laser sources.

17. The detector according to claim 1 , wherein the evaluation device is configured for deriving the combined signal Q by one or more of dividing the sensor signals, dividing multiples of the sensor signals, dividing linear combinations of the sensor signals, wherein the evaluation device is configured for using at least one predetermined relationship between the combined signal Q and the longitudinal coordinate for determining the initial distance information.

18. The detector according to claim 16 , wherein the evaluation device is configured to determine the combined signal Q based on a first area of the beam profile and a second area of the beam profile, wherein the first area of the beam profile comprises essentially edge information of the beam profile and the second area of the beam profile comprises essentially center information of the beam profile.

19. The detector according to claim 1 , wherein the evaluation device is configured for performing an image analysis of the reflection image thereby identifying reflections features of the reflection image.

20. The detector according to claim 1 , wherein the evaluation device is configured for identifying at least one reference feature in the reference image having an essentially identical longitudinal coordinate as the selected reflection feature.

21. The detector according to claim 1 , wherein the evaluation device is configured for deciding between more than one epipolar line and/or reference feature to be assigned to a reflection feature such as by comparing distances of reflection features and/or epipolar lines within the reference image and/or by comparing error weighted distances.

22. The detector according to claim 1 , wherein the evaluation device is configured for using the epipolar line for matching the respectively matched reference and reflection feature as epipolar line of said pair of matched reflection and reference features.

23. The detector according to claim 1 , wherein the evaluation device is configured for pre-classifying the selected reflection feature using the combined signal Q such that an unambiguous assignment to one reference feature is possible.

24. The detector according to claim 1 , wherein the evaluation device is configured for deriving the combined signal Q by

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Assignees

• Trinamix Gmbh

Inventors

• Schindler Patrick
• Schick Friedrich
• Lennartz Christian
• Schillen Peter
• Unger Jakob

Classifications

• G06T7/80

  Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration · CPC title

• G06T2207/30208

  Marker matrix · CPC title

• G06T7/85

  Stereo camera calibration · CPC title

• G01B21/045

  Correction of measurements (G01B9/02055 takes precedence) · CPC title

• G01B11/03

  by measuring coordinates of points · CPC title