Three-Dimensional Microscopic Image Reconstruction Based on Structured Light Illumination

In this paper, we propose and experimentally demonstrate a three-dimensional (3D) microscopic system that reconstructs a 3D image based on structured light illumination. The spatial pattern of the structured light changes according to the profile of the object, and by measuring the change, a 3D image of the object is reconstructed. The structured light is generated with a digital micro-mirror device (DMD), which controls the structured light pattern to change in a kHz rate and enables the system to record the 3D information in real time. The working distance of the imaging system is 9 cm at a resolution of 20 μm. The resolution, working distance, and real-time 3D imaging enable the system to be applied in bridge and road crack examinations, and structure fault detection of transportation infrastructures

Distortion Correction for Non-Planar Deformable Projection Displays through Homography Shaping and Projected Image Warping

Video projectors have advanced from being tools for only delivering presentations on flat or planar surfaces to tools for delivering media content in such applications as augmented reality, simulated sports practice and invisible displays. With the use of non-planar surfaces for projection comes geometric and radiometric distortions. This work dwells on correcting geometric distortions occurring when images or video frames are projected onto static and deformable non-planar display surfaces. The distortion-correction process involves (i) detecting feature points from the camera images and creating a desired shape of the undistorted view through a 2D homography, (ii) transforming the feature points on the camera images to control points on the projected images, (iii) calculating Radial Basis Function (RBF) warping coefficients from the control points, and warping the projected image to obtain an undistorted image of the projection on the projection surface. Several novel aspects of this work have emerged and include (i) developing a theoretical framework that explains the cause of distortion and provides a general warping pattern to be applied to the projection, (ii) carrying out the distortion-correction process without the use of a distortion-measuring calibration image or structured light pattern, (iii) carrying out the distortioncorrection process on a projection display that deforms with time with a single uncalibrated projector and uncalibrated camera, and (iv) performing an optimisation of the distortioncorrection processes to operate in real-time. The geometric distortion correction process designed in this work has been tested for both static projection systems in which the components remain fixed in position, and dynamic projection systems in which the positions of components or shape of the display change with time. The results of these tests show that the geometric distortion-correction technique developed in this work improves the observed image geometry by as much as 31% based on normalised correlation measure. The optimisation of the distortion-correction process resulted in a 98% improvement of its speed of operation thereby demonstrating the applicability of the proposed approach to real projection systems with deformable projection displays

Metodologias de calibração de projetores para aplicações robóticas de projection mapping

O objetivo inerente a esta dissertação consiste no desenvolvimento de técnicas de integração de projetor num sistema de projection mapping baseado em manipulador industrial (projector in hand). O sistema em que este trabalho se insere deve ser capaz de projetar imagens a três dimensões em vigas de construção metálicas, utilizando um projetor laser ou DLP, e aplicando técnicas de projection mapping, para uma projeção correta da informação do ponto de vista do operador. Para obter essa finalidade, é necessário aplicar algoritmos para calibrar eficientemente o projetor. Dada a natureza do projection mapping, em que se efetuam projeções em superficies tridimensionais, as questões de profundidade de foco são essenciais para a eficiência do sistema. Aliado a isto, surge a necessidade de avaliar pormenorizadamente em ambiente de simulação robótica a melhor localização para acoplar o projetor no manipulador industrial

3D high resolution techniques applied on small and medium size objects: from the analysis of the process towards quality assessment

The need for metric data acquisition is an issue strictly related to the human capability of describing the world with rigorous and repeatable methods. From the invention of photography to the development of advanced computers, the metric data acquisition has been subjected to rapid mutation, and nowadays there exists a strict connection between metric data acquisition and image processing, Computer Vision and Artificial Intelligence. The sensor devices for the 3D model generation are various and characterized by different functioning principles. In this work, optical passive and active sensors are treated, focusing specifically on close-range photogrammetry, Time of Flight (ToF) sensors and Structured-light scanners (SLS). Starting from the functioning principles of the techniques and showing some issues related to them, the work highlights their potentialities, analyzing the fundamental and most critical steps of the process leading to the quality assessment of the data. Central themes are the instruments calibration, the acquisition plan and the interpretation of the final results. The capability of the acquisition techniques to satisfy unconventional requirements in the field of Cultural Heritage is also shown. The thesis starts with an overview about the history and developments of 3D metric data acquisition. Chapter 1 treats the Human Vision System and presents a complete overview of 3D sensing devices. Chapter 2 starts from the enunciation of the basic principle of close-range photogrammetry considering digital cameras functioning principles, calibration issues, and the process leading to the 3D mesh reconstruction. The case of multi-image acquisition is analyzed, deepening the quality assessment of the photogrammetric process through a case study. Chapter 3 is devoted to the range-based acquisition techniques, namely ToF laser scanners and SLSs. Lastly, Chapter 4 focuses on unconventional applications of the mentioned high-resolution acquisition techniques showing some examples of study cases in the field of Cultural Heritage