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3D precision measurements of meter sized surfaces using low cost illumination and camera techniques
KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
2017 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 28, no 4, article id 045403Article in journal (Refereed) Published
Abstract [en]

Using dedicated stereo camera systems and structured light is a well-known method for measuring the 3D shape of large surfaces. However the problem is not trivial when high accuracy, in the range of few tens of microns, is needed. Many error sources need to be handled carefully in order to obtain high quality results. In this study, we present a measurement method based on low-cost camera and illumination solutions combined with high-precision image analysis and a new approach in camera calibration and 3D reconstruction. The setup consists of two ordinary digital cameras and a Gobo projector as a structured light source. A matrix of dots is projected onto the target area. The two cameras capture the images of the projected pattern on the object. The images are processed by advanced subpixel resolution algorithms prior to the application of the 3D reconstruction technique. The strength of the method lays in a different approach for calibration, 3D reconstruction, and high-precision image analysis algorithms. Using a 10 mm pitch pattern of the light dots, the method is capable of reconstructing the 3D shape of surfaces. The precision (1 sigma repeatability) in the measurements is < 10 mu m over a volume of 60 x 50 x 10 cm(3) at a hardware cost of similar to 2% of available advanced measurement techniques. The expanded uncertainty (95% confidence level) is estimated to be 83 mu m, with the largest uncertainty contribution coming from the absolute length of the metal ruler used as reference.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2017. Vol. 28, no 4, article id 045403
Keywords [en]
3D reconstruction, large area measurement, camera calibration, structured light, image processing, image metrology
National Category
Computer Vision and Robotics (Autonomous Systems)
Identifiers
URN: urn:nbn:se:kth:diva-205442DOI: 10.1088/1361-6501/aa5ae6ISI: 000395884500001Scopus ID: 2-s2.0-85014505994OAI: oai:DiVA.org:kth-205442DiVA, id: diva2:1097090
Note

QC 20170522

Available from: 2017-05-22 Created: 2017-05-22 Last updated: 2018-01-13Bibliographically approved
In thesis
1. Enhanced image analysis, a tool for precision metrology in the micro and macro world
Open this publication in new window or tab >>Enhanced image analysis, a tool for precision metrology in the micro and macro world
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The need for high speed and cost efficient inspection in manufacturing lineshas led to a vast usage of camera-based vision systems. The performance ofthese systems is sufficient to determine shape and size, but hardly to an accuracylevel comparable with traditional metrology tools. To achieve highprecision shape/position/defect measurements, the camera techniques haveto be combined with high performance image metrology techniques whichare developed and adapted to the manufactured components. The focus ofthis thesis is the application of enhanced image analysis as a tool for highprecision metrology. Dedicated algorithms have been developed, tested andevaluated in three practical cases ranging from micro manufacturing at submicronprecision to meter sized aerospace components with precision requirementsin the 10 μm range.The latter measurement challenge was solved by low cost standard consumerproducts, i.e. digital cameras in a stereo configuration and structured lightfrom a gobo-projector. Combined with high-precision image analysis and anew approach in camera calibration and 3D reconstruction for precise 3Dshape measurement of meter sized surfaces, the achievement was fulfilledand verified by two conventional measurement systems; a high precisioncoordinate measurement machine and a laser scanner.The sub-micron challenge was the implementation of image metrology forverification of micro manufacturing installations within a joint Europeaninfrastructure network, EUMINAfab. The results were an unpleasant surprisefor some of the participating laboratories, but became a big step forwardto improve the dimensional accuracy of the investigated laser micromachining, micro milling and micro-printing systems, since the accuracy ofthese techniques are very difficult to assess.The third high precision metrology challenge was the measurement of longrange,low-amplitude topographic structures on specular (shiny) aerodynamicsurfaces. In this case Fringe Reflection Technique (FRT) was appliedand image analysis algorithms were used to evaluate the fringe deformationas a measure of the surface slopes to obtain high resolution data. The resultwas compared with an interferometric analysis showing height deviation inthe range of tens of micrometers over a lateral extension of several cm.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. p. 120
Series
TRITA-IIP, ISSN 1650-1888 ; TRITA IIP-17-05
Keywords
Image processing, image metrology, precision metrology, image correlation, subpixel, accuracy, uncertainty
National Category
Engineering and Technology
Research subject
Production Engineering
Identifiers
urn:nbn:se:kth:diva-207594 (URN)978-91-7729-392-7 (ISBN)
Public defence
2017-06-15, M311, Brinellvägen 68, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
LOCOMACHSEUMINAfabCleansky
Note

QC 20170523

Available from: 2017-05-23 Created: 2017-05-22 Last updated: 2017-05-23Bibliographically approved

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Ekberg, PeterDaemi, BitaMattsson, Lars

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