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- Khodadad, Davood
(författare)
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Multiplexed Digital Holography incorporating Speckle Correlation
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)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 accurateas 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 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 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 onsingle-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 twotemperature 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 singleshotonline 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 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 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 torecord 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 singleshot dual wavelength digital holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve and evaluate the object shape. Usingmultidirectional 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.
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| 2. |
- Löfstrand, Magnus
(författare)
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A modelling and simulation approach for linking design activities to business decisions
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The business environment of the manufacturing industry is changing from a hardware-based product focus to a process and function focus. A current industrial interest is the development and sale of functions. This function could be realised as a product based on hardware, software and services, and may be sold as a function rather than as hardware. This function view is referred to as Functional Products (FP). The new focus for the customer is on value rather than hardware. This presents new challenges for how engineering hardware design may best be carried out. Sale of functional products requires a changed business model in which the price of the functional product is related to the functionality of the product itself; hence the name functional product. The supplier can in such a scenario no longer sell maintenance and spare parts. Instead, these activities become a cost, thus motivating the supplier to increase process efficiency, decrease internal production cost by using less energy per produced unit and increase knowledge about use-cases. The researcher's challenge is how to create new knowledge regarding functional product development for academic as well as for industrial benefit. The research question was formulated as: How may methods or tools for design process modelling and simulation be developed to support functional product development? Four case studies were carried out in Swedish industry. Case study 1 was carried out in cooperation with Hägglunds Drives AB. Case study 2 was carried out in cooperation with companies Hägglunds Drives AB, Volvo Aero and Volvo Car Corporation. Case study 3 was carried out in cooperation Volvo Aero and Case study 4 was carried out in cooperation with nine industrial companies during the formation of the Faste Laboratory, Centre for Functional Product Innovation. Results include the need for integrating product development process and company strategy for functional product development and the identification of the need for new methods and tools to enable better understanding of technology and business processes. The research shows the possibility of evaluating cost and time of development before doing the actual product development work by modelling and simulating the design process. Thus, the knowledge that previously was implicit in the work process is made explicit and possible to manipulate for a desired outcome. Linking the future business cases to work processes by modelling and simulation enables knowledge re-use and work-process predictions concerning cost and time. Hence, modelling and simulation of work processes results in better knowledge of company development capacity earlier than before, thus allowing shorter reaction time to changes in the business domain.
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