This is a master thesis of the Master of Science degree program in Applied Physics and Electrical Engineering at Linköping University. The goal of this thesis is to find out how the Microsoft Kinect can be used as a part of a camera rig to create accurate 3D-models of an indoor environment. The Microsoft Kinect is marketed as a touch free game controller for the Microsoft Xbox 360 game console. The Kinect contains a color and a depth camera. The depth camera works by constantly projecting a near infrared dot pattern that is observed with a near infrared camera. In this thesis it is described how to model the near infrared projector pattern to enable external near infrared cameras to be used to improve the measurement precision. The depth data that the Kinect output have been studied to determine what types of errors it contains. The finding was that the Kinect uses an online calibration algorithm that changes the depth data.

Ahlberg Cameras is a company that manufactures advanced camera systems and inspection equipment for the nuclear industry. Every nuclear plant shuts down their reactors approximately every 18 months to perform visual inspections of the vessels to find cracks and other damage. The company has received a request from Electric Power Research Institute (EPRI) to develop a distance meter that will operate in the reactor vessel, placed in an inspection camera. The device should measure the distance between the camera and an object, and the angle between them. The measurement is performed in air and underwater and the device has therefore a requirement to be waterproof and radiation tolerant.   This thesis work has studied different possible technologies and technically excluded the ones that are not suitable for the intended application. A large part of the study has been about whether sound or light is a good enough source to use in the different technologies. The study has excluded to use sound mainly because the reflection back to the receiver at large angles becomes too weak. The choice of technology stands between structured light and a self-designed trigonometry technology, both using lasers. Tests have been made to determine if laser light underwater can be observed by the camera and the results indicates that lasers work well enough for this kind of application. Further in-depth studies into the sources of errors and measurement accuracy are needed for determining which of the two technologies is the most suitable.

A miniaturized spatial light modulator (SLM)-based structured-light illumination module with optical fiber input is designed to generate a coded 256 x 256 spots pattern for 3-D areal mapping applications. The projector uses the light from a He-Ne laser coupled to a polarization-maintaining (PM) fiber to illuminate a specially made hologram so that four virtual point sources are regenerated. The interference pattern of the four sources are filtered and modulated by an SLM. The output intensity can thus be encoded to form any arbitrary pattern through the electronic input applied to the SLM with a high speed. In this thesis, a complete optical diffraction analysis of the system is presented to provide guidelines for the optimal design of the system parameters. Through the theoretical analysis for square beam array generation, the important parameters for fabricating a hologram are given. The final system optical design and arrangement based on optical analysis are described. The detailed opto-mechanical construction of the LIM and the associated alignment, the computer simulation and the preliminary test results of the developed LIM are also provided. / Master of Science

Urban Search and Rescue (USAR) is the emergency response function that deals with the collapse of man-made structures. USAR environments contain concrete rubble, dust and debris, and provide poor lighting conditions. Due to the dangers that USAR rescue workers and their canines face, robots have become of interest in aiding rescue workers in searching. Experiences with robots in USAR missions have shown that a compact 3D sensor for 3D mapping of the environment is beneficial in providing the robot and identified victims’ locations within the structurally unstable environment. This thesis presents the developments of a novel 3D sensory system that provides both 3D and 2D texture information for mapping of cluttered unknown USAR environments. The sensor has been integrated into a robot platform, and experiments conducted to validate its usability in such applications. The experimental results show the potential for using this sensor in USAR robot mission.

Urban Search and Rescue (USAR) is the emergency response function that deals with the collapse of man-made structures. USAR environments contain concrete rubble, dust and debris, and provide poor lighting conditions. Due to the dangers that USAR rescue workers and their canines face, robots have become of interest in aiding rescue workers in searching. Experiences with robots in USAR missions have shown that a compact 3D sensor for 3D mapping of the environment is beneficial in providing the robot and identified victims’ locations within the structurally unstable environment. This thesis presents the developments of a novel 3D sensory system that provides both 3D and 2D texture information for mapping of cluttered unknown USAR environments. The sensor has been integrated into a robot platform, and experiments conducted to validate its usability in such applications. The experimental results show the potential for using this sensor in USAR robot mission.

In dimensional metrology, contact and non-contact measurement methods each have their own respective strengths and weaknesses. Touch-trigger probes have low uncertainty, and perform well inside deep holes, but have a relatively slow data acquisition speed. By contrast, non-contact digitizers collect high density surface point clouds in seconds, and are much less likely to suffer from sensor collision with the part, but have a higher uncertainty than touch probes. In sheet metal forming, iterative design of the stamping die is needed due to the springback of the sheet metal part. Holes or other features of first article parts may be significantly out of tolerance, so the tactile measurement path created from the Computer Aided Design (CAD) nominal has to be adjusted to avoid cosine error. In more serious cases, probe collisions or missed touches may occur. When measuring holes in thin sheet metal, determination of the touch probe path height is also a challenge if the actual surface location differs from the nominal. To solve this problem and seize the complimentary advantages of contact and non-contact measurement methods, a multi-sensor blue Light Emitting Diode (LED) snapshot sensor and touch-trigger probe inspection system was developed, and affixed to a Coordinate Measuring Machine (CMM). The tactile measurement path was adjusted according to the approximate positions and sizes of the features obtained from the scanner data. The system includes an in-house designed calibration target for scanner calibration and a lightweight 2-axis rotary table for multiple-orientation scanning as well. Software in programming language C for interacting with the scanner and the CMM was developed. A sample stamped sheet metal automobile part was experimentally measured. This system is currently applied to an orthogonal CMM. Suggested future works include implementation on non-Cartesian CMMs, such as articulated arm CMMs, or Computer Numerical Control (CNC) machine tools. / Thesis / Master of Applied Science (MASc)

No / Excavation of the Schöningen lignite mine in Germany produced the earliest examples of hunting spears to date, and a large assemblage of anthropogenically fragmented faunal remains deposited in anaerobic lacustrine silt sediments during the Middle Pleistocene. The exceptional preservation of the assemblage makes the site of prime importance to our understanding of the behavioural, social and economic patterns of hominins in the Lower Palaeolithic of the Middle Pleistocene in Europe. This chapter describes the digital refitting analysis, part of the AHRC-funded Fragmented Heritage project, undertaken to address the logistical challenge posed by manually comparing individual bone fragments within the assemblage to identify refitting sequences. This logistical refit challenge uses the Schöningen assemblage to investigate the effectiveness of a digital refit approach to the analysis of large faunal assemblages. We describe the process from digitisation of the bone fragments by macro structured light scanning, digital segmentation of refitting surfaces, and digital comparison of the refitting and non-refitting surfaces to produce statistical matches. We discuss how taphonomic data can be visualised from the analysis and can be used to inform interpretation of the taphonomic histories of these faunal remains and the human behaviours associated with the formation of this unique assemblage. / The research was funded through an AHRC doctoral award as part of the AHRC Digital Transformations funded Theme Large Grant Fragmented Heritage (AH/L00688X/1) and through in-kind contributions from MONREPOS.

Phase measuring Profilometry (PMP) is an important technique used in 3D data acquisition. Many variations of the PMP technique exist in the research world. The technique involves projecting phase shifted versions of sinusoidal patterns with known frequency. The 3D information is obtained from the amount of phase deviation that the target object introduces in the captured patterns. Using patterns based on single frequency result in projecting a large number of patterns necessary to achieve minimal reconstruction errors. By using more than one frequency, that is multi-frequency, the error is reduced with the same number of total patterns projected as in the single frequency case. The first major goal of our research work is to minimize the error in 3D reconstruction for a given scan time using multiple frequency sine wave patterns. A mathematical model to estimate the optimal frequency values and the number of phase shift patterns based on stochastic analysis is given. Experiments are conducted by implementing the mathematical model to estimate the optimal frequencies and the number of patterns projected for each frequency level used. The reduction in 3D reconstruction errors and the quality of the 3D data obtained shows the validity of the proposed mathematical model. The second major goal of our research work is the implementation of a post-processing algorithm based on stereo correspondence matching adapted to structured light illumination. Composite pattern is created by combining multiple phase shift patterns and using principles from communication theory. Composite pattern is a novel technique for obtaining real time 3D depth information. The depth obtained by the demodulation of captured composite patterns is generally noisy compared to the multi-pattern approach. In order to obtain realistic 3D depth information, we propose a post-processing algorithm based on dynamic programming. Two different communication theory principles namely, Amplitude Modulation (AM) and Double Side Band Suppressed Carrier (DSBSC) are used to create the composite patterns. As a result of this research work, we developed a series of low-cost structured light scanners based on the multi-frequency PMP technique and tested them for their accuracy in different 3D applications. Three such scanners with different camera systems have been delivered to Toyota for vehicle assembly line inspection. All the scanners use off the shelf components. Two more scanners namely, the single fingerprint and the palmprint scanner developed as part of the Department of Homeland Security grant are in prototype and testing stages.

Final accepted manuscripts of parts 4 and 5 from Roadmap on Structured Light, authored by Masud Mansuripur, College of Optical Sciences, The University of Arizona.

"3D shape measurements are critical in a range of fields, from manufacturing for quality measurements to art conservation for the everlasting archival of ancient sculptures. The most important factor is to gather quantitative 3D information from measurement devices. Currently, there are limitations of existing systems. Many of the techniques are contact methods, proving to be time consuming and invasive to materials. While non-contact methods provide opportunities, many of the current systems are limited in versatility. This project focuses on the development of a fringe projection based system for 3D shape measurements. The critical advantage of the fringe projection optical technique is the ability to provide full field-of-view (FOV) information on the order from several square millimeters to several square meters. In the past, limitations in speed and difficulties achieving sinusoidal projection patterns have restricted the development of this particular type of system and limited its potential applications. For this reason, direct coding techniques have been incorporated to the developed system that modulate the intensity of each pixel to form a sinusoidal pattern using a 624 nm wavelength MEMS based spatial light modulator. Recovered phase data containing shape information is obtained using varying algorithms that range from a single image FFT analysis to a sixteen image, phase stepping algorithm. Reconstruction of 3D information is achievable through several image unwrapping techniques. The first is a spatial unwrapping technique for high speed applications. Additionally, the system uses an optimized Temporal Phase Unwrapping (TPU) algorithm that utilizes varying fringe frequencies ranging from 4 to 512 pixels per fringe to recover shape information in the time domain. This algorithm was chosen based on its robustness and accuracy for high resolution applications [Burke et al., 2002]. Also, unwrapping errors are minimized by approximately 90% as the number of images used is increased from the minimum to maximum fringe density. Cxoontrary to other systems, the 3D shape measurement system developed in the CHSLT laboratories has unprecedented versatility to accommodate a variety of applications with the z-depth resolution of up to 25.4 µm (0.001 inches) and speeds close to 200 frames per second. Hardware systems are integrated into user-friendly software that has been customized for fringe projection. The system has been tested in two extreme environments. The first is for quantification of cracks and potholes in the surface of roads under dynamic conditions. The second application was digitization of an art sculpture under static conditions. The system shows promising results and the potential for high quality images via algorithm optimization. Most importantly, there is potential to present real time 3D information at video speeds."