Determination of a Sampling Criterion for 3D Reconstruction

2017 ◽  
Vol 61 (4) ◽  
pp. 405011-4050114
Author(s):  
Deokwoo Lee ◽  
Hamid Krim
Keyword(s):  
2008 ◽  
Vol 191 (5) ◽  
pp. 1552-1558 ◽  
Author(s):  
Adam L. Summerlin ◽  
Mark E. Lockhart ◽  
Andrew M. Strang ◽  
Peter N. Kolettis ◽  
Naomi S. Fineberg ◽  
...  

Author(s):  
D. Typke ◽  
G. Pfeifer ◽  
R. Hegerl ◽  
W. Baumeister

The method of quasi-conical tilting for the 3D reconstruction of single macromolecules utilizes the fact that particles tend to adsorb to the supporting film in a few preferred orientations, though with arbitrary azimuthal angles. Therefore, a single electron micrograph of a tilted specimen containing a large number of particle projections provides the data of a conical tilt series with projection directions distributed randomly on a cone. For the selection of particles of equal orientation with respect to the supporting film and for the determination of their azimuth angles, a zero tilt image taken after the minimum dose “tilt image” is utilized.A disadvantage of the method is the large focal range of the tilt image, which e.g. at 30,000× magnification exceeds 5 μm. This, however, can be overcome by small-spot illumination in conjunction with dynamic focusing. For this, the illuminating beam is reduced to a diameter of 50-200 nm, and shifted stepwise or continuously over the object; for each spot position the focus is properly adjusted. Thus the focus range of the whole image is restricted to that of a single spot. Another way to realize dynamic focusing of a tilted object is the use of a narrow slit aperture in the condenser C2, thus illuminating a straight line parallel to the tilt axis.


2018 ◽  
Vol 4 (1) ◽  
pp. 517-520 ◽  
Author(s):  
Andreas Wachter ◽  
Jan Kost ◽  
Werner Nahm

AbstractContemporary surgical microscope systems have excellent optical properties but some desirable features remain unavailable. The number of co-observers is currently restricted, by spatial and optical limitations, to only two. Moreover, ergonomics poses are a problem: Current microscope systems impede free movement and sometimes demand that surgeons take uncomfortable postures over long periods of time. To rectify these issues, some companies developed surgical microscope systems based on a streaming approach. These systems remove some of the limitations. Multi-observer positions, for example, are not independent from each other, for example. In order to overcome the aforementioned limitations, we are currently developing an approach for the next generation of surgical microscope: Namely the fully digital surgical microscope, where the current observation system is replaced with a camera array, allowing real-time 3D reconstruction of surgical scenes and, consequently, the rendering of almost unlimited views for multiple observers. These digital microscopes could make the perspective through the microscope unnecessary allowing the surgeon to move freely and work in more comfortable postures. The requirements on the camera array in such a system have to be determined. For this purpose, we propose of estimation the minimal number of cameras and their positions needed for the 3D reconstruction of microsurgical scenes. The method of estimation is based on the requirements for the 3D reconstruction. Within the MATLAB simulation environment, we have developed a 3D model of a microsurgical scene, used for the determination of the number of required cameras. In a next step a small, compact and costefficient system with few opto-mechanical components could be manufactured.


Author(s):  
L. Zhang ◽  
J.Q. Zuo ◽  
L.P. Huang ◽  
X.G. Zhang ◽  
L.G. Shuai ◽  
...  

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 158
Author(s):  
Barış Özcan ◽  
Raimund Schwermann ◽  
Jörg Blankenbach

Determining the roughness of technical surfaces is an important task in many engineering disciplines. In civil engineering, for instance, the repair and reinforcement of building component parts (such as concrete structures) requires a certain surface roughness in order to ensure the bond between a coating material and base concrete. The sand patch method is so far the state-of-the-art for the roughness measurement of concrete structures. Although the method is easy to perform, it suffers from considerable drawbacks. Consequently, more sophisticated measurement systems are required. In a research project, we developed a novel camera-based alternative, which comes with several advantages. The measurement system consists of a mechanical cross slide that guides an industrial camera over a surface to be measured. Images taken by the camera are used for 3D reconstruction. Finally, the reconstructed point clouds are used to estimate roughness. In this article, we present our measurement system (including the hardware and the self-developed software for 3D reconstruction). We further provide experiments to camera calibration and evaluation of our system on concrete specimens. The resulting roughness estimates for the concrete specimens show a strong linear correlation to reference values obtained by the sand patch method.


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