Details
| Original language | English |
|---|---|
| Title of host publication | Optical Measurement Systems for Industrial Inspection XII |
| Editors | Peter Lehmann, Wolfgang Osten, Armando Albertazzi Goncalves |
| Publisher | SPIE |
| ISBN (electronic) | 9781510643987 |
| Publication status | Published - 20 Jun 2021 |
| Event | SPIE Optical Metrology - Online Duration: 21 Jun 2021 → 25 Jun 2021 https://spie.org/conferences-and-exhibitions/optical-metrology?SSO=1 |
Abstract
Triangulation based optical measuring systems are an important element of industrial quality assurance. Due to their robustness and cost-efficiency, laser light section sensors have become a widespread solution for geometry measurements. In order to reconstruct the scene, it is necessary to identify the corresponding laser line, which is distorted due to the geometrical properties of the specimen in the camera image. To achieve the highest precision possible, the line segmentation has to be performed at sub-pixel accuracy. Furthermore, in an industrial environment, interfering light sources may be present. A distinction between ambient influences and the laser light ensures a robust measurement. The projected laser line of a triangulation sensor is usually formed by a Powell lens from a point source, which results in a uniformly distributed intensity. Another option to achieve highly uniform intensity distributions is by means of a lenticular lens. A side effect of these optics is that the fine-structure of the projected line is formed by a chain of equidistant dots. In cross-section, the intensity distribution can be considered as a Gaussian profile. Challenges to the segmentation arise from the fine, dotted structure of the line. Although conventional methods, such as centroid based algorithms, can be applied, with the drawback of imprecise peak detection. To insure both segmentation accuracy und robustness, this paper introduces a novel segmentation method based on wavelet-transformation for lasers with lenticular lenses. In a first step the periodic fine structure of the line is utilized for a definite identification of the line with distinction from scattered light. In a second step a Gaussian wavelet is used to achieve sub-pixel accuracy in peak detection. The developed method is compared to conventional peak detection methods.
Keywords
- 3D measurement, Laser line segmentation, Triangulation, Wavelet transformation
ASJC Scopus subject areas
- Materials Science(all)
- Electronic, Optical and Magnetic Materials
- Physics and Astronomy(all)
- Condensed Matter Physics
- Computer Science(all)
- Computer Science Applications
- Mathematics(all)
- Applied Mathematics
- Engineering(all)
- Electrical and Electronic Engineering
Cite this
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- BibTeX
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Optical Measurement Systems for Industrial Inspection XII. ed. / Peter Lehmann; Wolfgang Osten; Armando Albertazzi Goncalves. SPIE, 2021. 1178216.
Research output: Chapter in book/report/conference proceeding › Conference contribution › Research
, 21 Jun 2021. https://doi.org/10.1117/12.2592657
}
TY - GEN
T1 - Robust and sub-pixel accurate wavelet-based segmentation of laser lines formed by lenticular lenses
AU - Bossemeyer, Hagen Johannes
AU - Kästner, Markus
AU - Reithmeier, Eduard
PY - 2021/6/20
Y1 - 2021/6/20
N2 - Triangulation based optical measuring systems are an important element of industrial quality assurance. Due to their robustness and cost-efficiency, laser light section sensors have become a widespread solution for geometry measurements. In order to reconstruct the scene, it is necessary to identify the corresponding laser line, which is distorted due to the geometrical properties of the specimen in the camera image. To achieve the highest precision possible, the line segmentation has to be performed at sub-pixel accuracy. Furthermore, in an industrial environment, interfering light sources may be present. A distinction between ambient influences and the laser light ensures a robust measurement. The projected laser line of a triangulation sensor is usually formed by a Powell lens from a point source, which results in a uniformly distributed intensity. Another option to achieve highly uniform intensity distributions is by means of a lenticular lens. A side effect of these optics is that the fine-structure of the projected line is formed by a chain of equidistant dots. In cross-section, the intensity distribution can be considered as a Gaussian profile. Challenges to the segmentation arise from the fine, dotted structure of the line. Although conventional methods, such as centroid based algorithms, can be applied, with the drawback of imprecise peak detection. To insure both segmentation accuracy und robustness, this paper introduces a novel segmentation method based on wavelet-transformation for lasers with lenticular lenses. In a first step the periodic fine structure of the line is utilized for a definite identification of the line with distinction from scattered light. In a second step a Gaussian wavelet is used to achieve sub-pixel accuracy in peak detection. The developed method is compared to conventional peak detection methods.
AB - Triangulation based optical measuring systems are an important element of industrial quality assurance. Due to their robustness and cost-efficiency, laser light section sensors have become a widespread solution for geometry measurements. In order to reconstruct the scene, it is necessary to identify the corresponding laser line, which is distorted due to the geometrical properties of the specimen in the camera image. To achieve the highest precision possible, the line segmentation has to be performed at sub-pixel accuracy. Furthermore, in an industrial environment, interfering light sources may be present. A distinction between ambient influences and the laser light ensures a robust measurement. The projected laser line of a triangulation sensor is usually formed by a Powell lens from a point source, which results in a uniformly distributed intensity. Another option to achieve highly uniform intensity distributions is by means of a lenticular lens. A side effect of these optics is that the fine-structure of the projected line is formed by a chain of equidistant dots. In cross-section, the intensity distribution can be considered as a Gaussian profile. Challenges to the segmentation arise from the fine, dotted structure of the line. Although conventional methods, such as centroid based algorithms, can be applied, with the drawback of imprecise peak detection. To insure both segmentation accuracy und robustness, this paper introduces a novel segmentation method based on wavelet-transformation for lasers with lenticular lenses. In a first step the periodic fine structure of the line is utilized for a definite identification of the line with distinction from scattered light. In a second step a Gaussian wavelet is used to achieve sub-pixel accuracy in peak detection. The developed method is compared to conventional peak detection methods.
KW - 3D measurement
KW - Laser line segmentation
KW - Triangulation
KW - Wavelet transformation
UR - http://www.scopus.com/inward/record.url?scp=85109409678&partnerID=8YFLogxK
U2 - 10.1117/12.2592657
DO - 10.1117/12.2592657
M3 - Conference contribution
BT - Optical Measurement Systems for Industrial Inspection XII
A2 - Lehmann, Peter
A2 - Osten, Wolfgang
A2 - Goncalves, Armando Albertazzi
PB - SPIE
T2 - SPIE Optical Metrology<br/>
Y2 - 21 June 2021 through 25 June 2021
ER -