Maciej Karaszewski

On-line, collision-free positioning of a scanner during fully automated three-dimensional measurement of cultural heritage objects

Fully automated three-dimensional (3D) measurement (either with contact or non-contact measurement heads) cannot be easily completed without detailed a priori knowledge of the measured object. This requirement may be easily fulfilled for objects whose CAD models are available (for example, mechanical parts); however, for unique artifacts (such as sculptures), such models are usually unavailable. A description of the objects shape is required to create a list of positions at which the scanning head should be placed to completely measure the whole object (so-called next best views list). For unique objects, this analysis has to be performed on-line during measurements, using obtained data to update the list. For a fully automated measurement, the scanning system must be positioned mechanically, and the transition between subsequent head positions has to be collision free. This paper presents a novel system for 3D digitization of cultural heritage objects which allows one to perform completely automated shape measurements in a given volume with sampling resolutions up to 10000 points/ mm^2. Its main novelties are the next best view module for identifying the best position and orientation of the measurement head in subsequent directional scans (optimized for artifacts of size much bigger than the measurement volume) and flexible software modules for inverse kinematics and collision detection, which allow one to build a positioning system tailored to specific measurement objects. The system is used for digitization of a collection from the Wilanow Palace Museum, Warsaw.

Automated processing of data from 3D scanning of cultural heritage objects

In this paper, the concept of computational environment for processing of very large datasets (clouds of points with amount up to 1011 measurement points) obtained from 3D shape measurement systems, is presented. The software design is directed at maximum automation of processing, allows for defining scripts describing complicated calculations which make user interaction and attendance during operations unnecessary. The following paper describes main postulates of the environment along with its practical exemplary implementation as the application controlling fully automated 3D shape measurement system, 3DMADMAC AUTO, designed for precise, autonomous digitization of cultural heritage objects.

Automated full-3D digitization system for documentation of paintings

In this paper, a fully automated 3D digitization system for documentation of paintings is presented. It consists of a specially designed frame system for secure fixing of painting, a custom designed, structured light-based, high-resolution measurement head with no IR and UV emission. This device is automatically positioned in two axes (parallel to the surface of digitized painting) with additional manual positioning in third, perpendicular axis. Manual change of observation angle is also possible around two axes to re-measure even partially shadowed areas. The whole system is built in a way which provides full protection of digitized object (moving elements cannot reach its vicinity) and is driven by computer-controlled, highly precise servomechanisms. It can be used for automatic (without any user attention) and fast measurement of the paintings with some limitation to their properties: maximum size of the picture is 2000mm x 2000mm (with deviation of flatness smaller than 20mm) Measurement head is automatically calibrated by the system and its possible working volume starts from 50mm x 50mm x 20mm (10000 points per square mm) and ends at 120mm x 80mm x 60mm (2500 points per square mm). The directional measurements obtained with this system are automatically initially aligned due to the measurement head’s position coordinates known from servomechanisms. After the whole painting is digitized, the measurements are fine-aligned with color-based ICP algorithm to remove any influence of possible inaccuracy of positioning devices. We present exemplary digitization results along with the discussion about the opportunities of analysis which appear for such high-resolution, 3D computer models of paintings.

Remote online monitoring and measuring system for civil engineering structures

In this paper a distributed intelligent system for civil engineering structures on-line measurement, remote monitoring, and data archiving is presented. The system consists of a set of optical, full-field displacement sensors connected to a controlling server. The server conducts measurements according to a list of scheduled tasks and stores the primary data or initial results in a remote centralized database. Simultaneously the server performs checks, ordered by the operator, which may in turn result with an alert or a specific action. The structure of whole system is analyzed along with the discussion on possible fields of application and the ways to provide a relevant security during data transport. Finally, a working implementation consisting of a fringe projection, geometrical moiré, digital image correlation and grating interferometry sensors and Oracle XE database is presented. The results from database utilized for on-line monitoring of a threshold value of strain for an exemplary area of interest at the engineering structure are presented and discussed.

Color-Based Algorithm for Automatic Merging of Multiview 3D Point Clouds

In this article, a method of merging point clouds using the modified Harris corner detection algorithm for extracting interest points of textured 3D point clouds is proposed. A new descriptor characterizing point features for identifying corresponding points in datasets is presented. The merging process is based on the Random Sample Consensus (RANSAC) algorithm, which enables calculation of the geometric transformation between point clouds based on a set of interest points that includes incorrect samples, called outliers. The proposed processing path is designed to integrate many directional measurements, which are acquired with a 3D scanner and are represented as unsorted point clouds (x, y, z) with color information (R, G, B). Exemplary measurements shown in this article represent sections of ceiling in the Kings Chinese Cabinet of the Museum of King Jan IIIs Palace at Wilanow in Warsaw, Poland, as well as some more complex objects. Experimental verification confirms the effectiveness of the proposed method in integrating directional measurements of objects with detailed texture, particularly if they have no unique geometric features.

Automated full-3D shape measurement of cultural heritage objects

In this paper a fully automated 3D shape measurement system is presented. It consists of rotary stage for cultural heritage objects placement, vertical linear stage with mounted robot arm (with six degrees of freedom) and structured light measurement set-up mounted to its head. All these manipulation devices are automatically controlled by collision detection and next-best-view calculation modules. The goal of whole system is to automatically (without any user attention) and rapidly (from days and weeks to hours) measure whole object. Measurement head is automatically calibrated by the system and its possible working volume starts from centimeters and ends up to one meter. We present some measurement results with different working scenarios along with discussion about its possible applications.

Two-stage automated measurement process for high-resolution 3D digitization of unknown objects

In this paper, a process for high-resolution, automated 3D digitization of unknown objects (i.e., without any digital model) is presented. The process has two stages-the first leads to a coarse 3D digital model of the object, and the second obtains the final model. A rough model, acquired by a 3D measurement head with a large working volume and relatively low resolution, is used to calculate the precise head positions required for the full digitization of the object, as well as collision detection and avoidance. We show that this approach is much more efficient than digitization with only a precise head, when its positions for subsequent measurements (so-called next-best-views) must be calculated based only on a partially recovered 3D model of the object. We also show how using a rough object representation for collision detection shortens the high-resolution digitization process.

Colour and Space in Cultural Heritage: Key Questions in 3D Optical Documentation of Material Culture for Conservation, Study and Preservation

The paper introduces some key interdisciplinary questions concerning the development of optical measuring techniques and electronic imaging applied to documentation and presentation of artefacts, as identified through the work of Colour and Space in Cultural Heritage (www.COSCH.info), a trans-domain European Action (TD1201) in the area of Materials, Physics and Nanosciences (MPNS) supported, since 2013, by the European Cooperation in Science and Technology http://www.cost.eu/domains_actions/mpns/Actions/ TD1201. Some 125 international researchers and professionals participate in COSCH activities which have been organised around six main subjects: (1) spectral object documentation; (2) spatial object documentation; (3) algorithms and procedures; (4) analysis and restoration of cultural heritage surfaces and objects; (5) visualisation of cultural heritage objects and its dissemination; and (6) the semantic development of the COSCH Knowledge Representation.

Colour and Space in Cultural Heritage: Interdisciplinary Approaches to Documentation of Material Culture

Colour and Space in Cultural Heritage (www.COSCH.info) is a transdomain European Action (TD1201) in the area of Materials, Physics and Nanosciences (MPNS). The Action runs from 2013 to 2017 and benefits from the support of the European Cooperation in Science and Technology http://www.cost.eu/domains_actions/mpns/Actions/TD1201. The Authors are active participants of the COSCH network. They represent different disciplines involved in documentation and conservation of material cultural heritage. COSCH aims to enhance applications of optical measuring techniques and electronic imaging in this area. The paper outlines scientific, theoretical and practical solutions promoted by COSCH. COSCH activities have been organised around six main subjects: (1) spectral object documentation; (2) spatial object documentation; (3) algorithms and procedures; (4) analysis and restoration of cultural heritage surfaces and objects; (5) visualisation of cultural heritage objects and its dissemination; and (6) the semantic devel...

Effect of temperature on calibration quality of structured-light three-dimensional scanners

This paper presents the outcome of research into the effects of ambient temperature changes on structured-light three-dimensional (3D) scanners. The tests were conducted in a thermal chamber and consisted of a comparison of the 3D measurement of a special reference unit (made of a carbon composite) performed at different temperatures, with measurements performed at the calibration temperature. A contact measuring arm with temperature compensation was used as a reference. Based on the results of these experiments, we propose a method that allows us to extend the existing scanner calibration method by using a temperature-correction procedure that is based on linear and nonlinear mathematical models. An exemplary application of this procedure has shown that the range of temperatures in which scanner accuracy is within declared limits can be increased 11-fold.