Abstract
Abstract. The 3D digitisation of small artefacts is a very complicated procedure because of their complex morphological feature structures, concavities, rich decorations, high frequency of colour changes in texture, increased accuracy requirements etc. Image-based methods present a low cost, fast and effective alternative because laser scanning does not meet the accuracy requirements in general. A shallow Depth of Field (DoF) affects the image-based 3D reconstruction and especially the point matching procedure. This is visible not only in the total number of corresponding points but also in the resolution of the produced 3D model. The extension of the DoF is a very important task that should be incorporated in the data collection to attain a better quality of the image set and a better 3D model. An extension of the DoF can be achieved with many methods and especially with the use of the focus stacking technique. In this paper, the focus stacking technique was tested in a real-world experiment to digitise a museum artefact in 3D. The experiment conditions include the use of a full frame camera equipped with a normal lens (50mm), with the camera being placed close to the object. The artefact has already been digitised with a structured light system and that model served as the reference model in which 3D models were compared and the results were presented.
Highlights
The depth of field (DoF) defines a range of distances, in which a scene appears to be acceptably sharp and is affected mainly by the camera’s focal length, the lens aperture and the focusing distance
It may lead to a very sparse set of points with areas on the surface of an object with no point correspondences. We investigate exactly this eventual effect of 3D reconstruction by applying automatic image based modelling using SfM and multi-viewstereo algorithm (MVS) techniques to images of “best focus” and images created with focus stacking techniques
This seems that the focus stacking technique affects the process of the dense image matching and 3D triangulation mesh
Summary
The depth of field (DoF) defines a range of distances, in which a scene appears to be acceptably sharp and is affected mainly by the camera’s focal length, the lens aperture and the focusing distance. In the case of small artefacts, it is very difficult to capture all the details of the objects and the alignment process with a shallow DoF is expected to be based on a limited amount of salient points from regions in focus. This may affect the point matching procedure, the number of conjugate points determined and the resolution of the 3D model. The rest of the paper is organised as follows: section 2 describes the focus stacking technique and section 3 presents related work of the focus stacking in 3D reconstruction; section 4 presents the experimental setup and section 5 describes how these data were integrated; the evaluation of the results and some concluding remarks are presented
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