DOCTORAL T H E SIS Department of Engineering Sciences and Mathematics Division of Fluid and Experimental Mechanics Davood Khodadad Multiplexed Digital incorporating Holography Khodadad Multiplexed Speckle Correlation Davood ISSN 1402-1544 Multiplexed Digital Holography ISBN 978-91-7583-517-4 (print) ISBN 978-91-7583-518-1 (pdf) incorporatingMultiplexed SpeckleDigital Holography Correlation Luleå University of Technology 2016 incorporating Speckle Correlation Davood Khodadad Davood Khodadad Experimental Mechanics Multiplexed Digital Holography incorporating Speckle Correlation Davood Khodadad Luleå University of Technology Department of Engineering Sciences and Mathematics Division of Fluid and Experimental Mechanics February 2016 Printed by Luleå University of Technology, Graphic Production 2016 ISSN 1402-1544 ISBN 978-91-7583-517-4 (print) ISBN 978-91-7583-518-1 (pdf) Luleå 2016 www.ltu.se To you who always believe in me, my beloved parents and sisters, words could never explain how I feel about you. i Preface This work has been carried out at the Division of Fluid and Experimental Mechanics, Department of Engineering Sciences and Mathematics at Luleå University of Technology (LTU) in Sweden. The research was performed during the years 2012-2016, under the supervision of Prof. Mikael Sjödahl, LTU, Dr. Emil Hällstig, Fotonic, and Dr. Erik Olsson, LTU. First I would like to thank my supervisors Prof. Mikael Sjödahl, Dr. Emil Hällstig and Dr. Erik Olsson for their valuable support, ideas and encouragement during this work. I would also like to thank Dr. Per Gren, Dr. Henrik Lycksam and Dr. Eynas Amer for all the help in the lab. Secondly, I would like to express my gratitude to Prof. Wolfgang Osten and Dr. Giancarlo Pedrini at the Institute of Applied Optics at University of Stuttgart, for inviting me to Stuttgart and giving me the opportunity to work in one of the most exciting places in optics in the world. Thanks to Alok Kumar Singh for his help in the laboratory and many fruitful discussions. I am also grateful to the rest of the Coherent Measurement Techniques group at the Institute of Applied Optics for making my visit there both a pleasant and an interesting experience. This work has been a part of the HOLOPRO project and has been financially supported by the Swedish Governmental Agency for Innovation Systems, VINNOVA. I would also like to thank the collaboration partners in this project; the research group at the Division of Scientific Computing at LTU especially Dr. Per Bergström for nice cooperation. I am also grateful for the collaboration with Emil Melander from the Department of Physics and Astronomy, Uppsala University. Furthermore I would like to thank my office mates, Ammar Hazim Saber and Yiling Li; also my colleagues at the Division of Fluid and Experimental Mechanics for interesting discussions and everyone else at the department that made my time here so amazingly inspiring and enjoyable. Finally, I give my deepest gratitude to my beloved family for caring and believing in me, even though not always understanding the meaning of what I have been doing for all these years. Davood Khodadad Luleå, Februaty 2016 ii iii Abstract In manufacturing industry there is a high demand for on line quality control to minimize the risk of incorrectly produced objects. Conventional contact measurement methods are usually slow and invasive, meaning that they cannot be used for soft materials and for complex shapes without influencing the controlled parts. In contrast, interferometry and digital holography in combination with computers become faster, more reliable and highly accurate as an alternative non-contact technique for industrial shape evaluation. For example in digital holography, access to the complex wave field and the possibility to numerically reconstruct holograms in different planes introduce a new degree of flexibility to optical metrology. With digital holography high resolution and precise three dimensional (3D) images of the manufactured parts can be generated. This technique can also be used to capture data in a single 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 shape and deformation measurements. To perform online process control of free-form manufactured objects, the measured shape is compared with the CAD-model to obtain deviations. To do this, a new technique to measure surface gradients and shape based on single-shot multiplexed dual-wavelength digital holography and image correlation of speckle displacements is demonstrated. Based on an analytical relation between phase gradients and speckle displacements it is shown that an object is retrieved uniquely to shape, position and deformation without the unwrapping problems that usually appear in dual-wavelength holography. The method is first demonstrated using continues-wave laser light from two temperature controlled laser diodes operating at 640 nm. Then a specially designed dual core diode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm is used. In addition, a Nd:YAG laser with the wavelength of 532 nm is used for 3D deformation measurements. One significant problem when using the dual-wavelength single-shot approach is that phase ambiguities are built in to the system that needs to be corrected. An automatic calibration scheme is therefore required. The intrinsic flexibility of digital holography gives a possibility to compensate these aberrations and to remove errors, fully numerically without mechanical movements. In this thesis I present a calibration method which allows multiplexed single- shot online shape evaluation in a disturbed environment. It is shown that phase maps and speckle displacements can be recovered free of chromatic aberrations. This is the first time iv that a multiplexed single-shot dual-wavelength calibration is reported by defining a criteria to make an automatic procedure. Further, Digital Speckle Photography (DSP) is used for the full field measurement of 3D deformations. In order to do 3D deformation measurement, usually multi-cameras and intricate set-up are required. In this thesis I demonstrate the use of only one single camera to record four sets of speckle patterns recorded by illuminating the object from four different directions. In this manner, meanwhile 3D speckle displacement is calculated and used for the measurement of the 3D deformations, wrapping problems are also avoided. Further, the same scale of speckle images of the surface for all four images is guaranteed. Furthermore, a need for 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 single- shot dual wavelength digital holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve and evaluate the object shape. Using multidirectional illumination, the 3D deformation measurements can also be obtained. The proposed method is robust to large phase gradients and large movements within the intensity patterns. The advantage of the approach is that, using speckle displacements, shape and deformation measurements can be performed even though the synthetic wavelength is out of the dynamic range of the object deformation and/or height variation. v Thesis This thesis consists of a background of the work and the following papers: Paper A D. Khodadad, E. Hällstig, and M. Sjödahl, "Dual-wavelength digital holographic shape measurement using speckle movements and phase gradients," Optical Engineering, vol. 52, pp. 101912-101912, 2013. Paper B P. Bergström, D. Khodadad, E. Hällstig, and M. Sjödahl, "Dual-wavelength digital holography: single-shot shape evaluation using speckle displacements and regularization," Applied Optics, vol. 53, pp. 123-131, 2014. Paper C D. Khodadad, P. Bergström, E. Hällstig, and M. Sjödahl, "Single Shot Dual- Wavelength Digital Holography: Calibration Based on Speckle Displacements," International Journal of Optomechatronics 8, 326-339 (2014). Paper D D. Khodadad, P. Bergström, E. Hällstig, and M. Sjödahl, "Fast and robust automatic calibration for single-shot dual-wavelength digital holography based on speckle displacements," Applied Optics, vol. 54, pp. 5003-5010 (2015). Paper E D. Khodadad, A. K. Singh, G. Pedrini, W. Osten, and M. Sjödahl, " Full field 3D deformation measurement based on 3D laser speckle displacements," manuscript. Additional papers, related to the thesis but not included: Paper F D. Khodadad, "Phase-derivative-based estimation of digital reference wave from single off-axis digital hologram," Applied Optics, vol. 55(12), 2016. Paper G D. Khodadad, E. Amer, P. Gren, E. Melander, E. Hällstig and M. Sjödahl, " Single-shot dual-polarization holography: measurement of the polarization state of a magnetic sample," Proc. SPIE 9660, SPECKLE 2015: VI vi International Conference on Speckle Metrology, 96601E (August 24, 2015); doi:10.1117/12.2189782; http://dx.doi.org/10.1117/12.2189782 Paper H D. Khodadad, P. Bergström, E. Hällstig, and M. Sjödahl, " Dual-wavelength digital holography: single shot calibration ", Proc. SPIE 9203, Interferometry XVII: Techniques and Analysis, 920305 (August 18, 2014); doi:10.1117/12.2062101; http://dx.doi.org/10.1117/12.2062101 Paper I P. Bergström, D. Khodadad, E. Hällstig, and M. Sjödahl, " Single Shot Shape Evaluation Using Dual-Wavelength Holographic