lnu.sePublikationer
Ändra sökning
RefereraExporteraLänk till posten
Permanent länk

Direktlänk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Multiplexed Digital Holography incorporating Speckle Correlation
Luleå University of Technology.ORCID-id: 0000-0003-2960-3094
2016 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

In manufacturing industry there is a high demand for on line quality control to minimize therisk of incorrectly produced objects. Conventional contact measurement methods are usuallyslow and invasive, meaning that they cannot be used for soft materials and for complexshapes without influencing the controlled parts. In contrast, interferometry and digitalholography in combination with computers become faster, more reliable and highly accurateas an alternative non-contact technique for industrial shape evaluation. For example in digitalholography, access to the complex wave field and the possibility to numerically reconstructholograms in different planes introduce a new degree of flexibility to optical metrology. Withdigital holography high resolution and precise three dimensional (3D) images of themanufactured parts can be generated. This technique can also be used to capture data in asingle exposure, which is important when doing measurements in a disturbed environment.

The aim of this thesis is devoted to the theoretical and experimental development of shapeand deformation measurements. To perform online process control of free-formmanufactured objects, the measured shape is compared with the CAD-model to obtaindeviations. To do this, a new technique to measure surface gradients and shape based onsingle-shot multiplexed dual-wavelength digital holography and image correlation of speckledisplacements is demonstrated. Based on an analytical relation between phase gradients andspeckle displacements it is shown that an object is retrieved uniquely to shape, position anddeformation without the unwrapping problems that usually appear in dual-wavelengthholography. The method is first demonstrated using continues-wave laser light from twotemperature controlled laser diodes operating at 640 nm. Then a specially designed dual corediode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm isused. In addition, a Nd:YAG laser with the wavelength of 532 nm is used for 3D deformationmeasurements.

One significant problem when using the dual-wavelength single-shot approach is that phaseambiguities are built in to the system that needs to be corrected. An automatic calibrationscheme is therefore required. The intrinsic flexibility of digital holography gives a possibilityto compensate these aberrations and to remove errors, fully numerically without mechanicalmovements. In this thesis I present a calibration method which allows multiplexed singleshotonline shape evaluation in a disturbed environment. It is shown that phase maps andspeckle displacements can be recovered free of chromatic aberrations. This is the first time that a multiplexed single-shot dual-wavelength calibration is reported by defining a criteria tomake an automatic procedure.

Further, Digital Speckle Photography (DSP) is used for the full field measurement of 3Ddeformations. In order to do 3D deformation measurement, usually multi-cameras andintricate set-up are required. In this thesis I demonstrate the use of only one single camera torecord four sets of speckle patterns recorded by illuminating the object from four differentdirections. In this manner, meanwhile 3D speckle displacement is calculated and used for themeasurement of the 3D deformations, wrapping problems are also avoided. Further, the samescale of speckle images of the surface for all four images is guaranteed. Furthermore, a needfor calibration of the 3D deformation measurement that occurs in the multi-camera methods,is removed.

By the results of the presented work, it is experimentally verified that the multiplexed singleshotdual wavelength digital holography and numerically generated speckle images can beused together with digital speckle correlation to retrieve and evaluate the object shape. Usingmultidirectional illumination, the 3D deformation measurements can also be obtained. Theproposed method is robust to large phase gradients and large movements within the intensitypatterns. The advantage of the approach is that, using speckle displacements, shape anddeformation measurements can be performed even though the synthetic wavelength is out ofthe dynamic range of the object deformation and/or height variation.

Ort, förlag, år, upplaga, sidor
Luleå tekniska universitet, 2016. , s. 155
Serie
Doctoral thesis / Luleå University of Technology, ISSN 1402-1544
Nationell ämneskategori
Signalbehandling
Forskningsämne
Teknik
Identifikatorer
URN: urn:nbn:se:lnu:diva-55810ISBN: 978-91-7583-517-4 (tryckt)OAI: oai:DiVA.org:lnu-55810DiVA, id: diva2:956021
Tillgänglig från: 2016-08-29 Skapad: 2016-08-29 Senast uppdaterad: 2018-09-10Bibliografiskt granskad

Open Access i DiVA

fulltext(13579 kB)299 nedladdningar
Filinformation
Filnamn FULLTEXT01.pdfFilstorlek 13579 kBChecksumma SHA-512
0039101ba228ddc271d7b80f3b8925d1f1fbe5a69aaf636af2dc0eecb2a7eb4ff433e4a5c8e3c808f8991b633f12c83d52ca96969174c69df15fdf3a6f6a55c5
Typ fulltextMimetyp application/pdf

Övriga länkar

Fulltext

Personposter BETA

Khodadad, Davood

Sök vidare i DiVA

Av författaren/redaktören
Khodadad, Davood
Signalbehandling

Sök vidare utanför DiVA

GoogleGoogle Scholar
Totalt: 299 nedladdningar
Antalet nedladdningar är summan av nedladdningar för alla fulltexter. Det kan inkludera t.ex tidigare versioner som nu inte längre är tillgängliga.

isbn
urn-nbn

Altmetricpoäng

isbn
urn-nbn
Totalt: 4193 träffar
RefereraExporteraLänk till posten
Permanent länk

Direktlänk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf