This paper presents the results of a metrological analysis of the additively manufactured (AM) copies of a complex geometrical object, namely the fossil skull of Madygenerpeton pustulatum. This fossil represents the unique remains of an extinct “reptiliomorph amphibian” of high importance for palaeontological science. For this research, the surface was scanned and twelve different copies were 3D-printed using various devices, materials, and AM techniques. The same digitized model was used as a reference to compare with the surfaces obtained by Mitutoyo Coordinate Measuring Machine (CMM) CRYSTA-Apex S 9166 for each copy. The fidelity of the copies was assessed through statistical analysis of the distances between compared surfaces. The methodology provided a good background for the choice of the most accurate copies and the elimination of the less accurate ones. The proposed approach can be applied to any object of complex geometry when reproduction accuracy is to be assessed.

Digital photoelasticity is an important optical metrology follow-up for stress and strain analysis using full-field digital photographic images. Advances in digital image processing, data acquisition, procedures for pattern recognition and storage capacity enable the use of the computer-aided technique in automation and facilitate improvement of the digital photoelastic technique. The objective of this research is to find new equations for a novel phase-shifting method in digital photoelasticity. Some innovations are proposed. In terms of phaseshifting, only the analyzer is rotated, and the other equations are deduced by applying a new numerical technique instead of the usual algebraic techniques. This approach can be used to calculate a larger sequence of images. Each image represents a pattern and a measurement of the stresses present in the object. A decrease in the mean errors was obtained by increasing the number of observations. A reduction in the difference between the theoretical and experimental values of stresses was obtained by increasing the number of images in the equations for calculating phase. Every photographic image has errors and random noise, but the uncertainties due to these effects can be reduced with a larger number of observations. The proposed method with many images and high accuracy is a good alternative to the photoelastic techniques.

This article proposes an unequivocal method of labeling and numbering the cladding modes propagating in single-mode opticalwaveguides with tilted periodic structures. The unambiguous determination of individual propagating modes in this type of optical fiber is crucial for their use in sensory systems. The selection of the appropriate spectral range and mode determines the sensitivity and measuring range of tilted fiber Bragg grating (TFBG) sensors. The measurement methods proposed by individual research teams using TFBGs as transducers are usually based on the selection of specific modes. Unification of the labeling of modes and their numbering enables comparison of the basic metrological parameters of individual measurement methods and reproduction and verification of the proposed sensors and methods in the laboratories of other scientific and research centers.

Digital metrologywas applied to evaluate 3D models of the unique skull of a fossil tetrapod, Madygenerpeton pustulatum, generated using various 3D digitization methods. The skull surface is covered by minute tubercles making it challenging for digitization with appropriate accuracy. Uniqueness and fragility of the specimen preclude the use of tactile measuring systems for creating a standardized reference model. To overcome this problem, comparative analysis of the triangulated models generated from the clouds of points obtained with seven different devices was conducted using the Geomagic Studio and Autodesk PowerShape CAD software. In the proposed approach, geometrically and dimensionally closest-fitting models underwent detailed statistical analysis between surface polygons in three steps. First, 3D models obtained from different scanning methods were compared with each other in couples. Next, statistical analysis of the differences between the coupled models was performed. Finally, a rating list of the models related to the required accuracy was prepared. The proposed approach is applicable to any other scanned object, especially in palaeontological applications, where each object is unique and exhibits individual features.

We present a prototype of a simple, low-cost setup for a fast scatterometric surface texture measurements. We used a total integrated scatter method (TIS) with a semiconductor laser (λ =  638 nm) and a Si photodiode. Using our setup, we estimated the roughness parameters Rq for two reference surfaces (Al mirrors with flatness λ/10) and seven equal steel plates to compare. The setup is easily adaptable for a fast, preliminary manufacturing quality control. We show is possible to construct a low-cost measurement system with nanometric precision.

Present paper is a continuation of works on evaluation of red, green, blue (RGB) to hue, saturation, intensity (HSI) colour space transformation in regard to digital image processing application in optical measurements methods. HSI colour space seems to be the most suitable domain for engineering applications due to its immunity to non-uniform lightning. Previous stages referred to the analysis of various RGB to HSI colour space transformations equivalence and programming platform configuration influence on the algorithms execution. The main purpose of this step is to understand the influence of computer processor architecture on the computing time, since analysis of images requires considerable computer resources. The technical development of computer components is very fast and selection of particular processor architecture can be an advantage for fastening the image analysis and then the measurements results. In this paper the colour space transformation algorithms, their complexity and execution time are discussed. The most common algorithms were compared with the authors own one. Computing time was considered as the main criterion taking into account a technical advancement of two computer processor architectures. It was shown that proposed algorithm was characterized by shorter execution time than in reported previously results.

Maintenance of assets and equipment in power plants is essential for their safety and is required to help the plant stay active. In this paper, the specimens manufactured from a pipe of X10CrMoVNb9-1 (P91) power engineering steel in the as-received state and after operating for 80000 h at internal pressure of 8.4 MPa and temperature of 540ºC were subjected to tests using electronic speckle pattern interferometry (ESPI) under static loading of up to 2.5 kN. Such a procedure enables assessment of strain and stress distribution maps to compare material integrity in the as-received state and after exploitation in its elastic range. The measurements conducted showed no effect of long time operation on the mechanical response of P91 steel under the power installations conditions since the field strain distributions for each type of specimen were found to be similar.

The use of technology in sports has increased in recent years. One of the most influential of these technologies is referee support systems. Team sports such as volleyball require accurate and robust tracking systems that do not affect either the players or the court. This paper introduces the application of intrinsic and extrinsic camera calibration in a 12-camera volleyball referee system. Intrinsic parameters are calculated by using the classic pinhole model and Zhang’s method. To perform extrinsic calibration in real time, the volleyball court is treated as a global calibration artifact. Calibration keypoints are defined as court-line intersections. In addition, a new keypoint detection algorithm is proposed. It enables achievement of an accurate camera pose in regard to the court. With all 12 cameras calibrated in a common coordinate system, a dynamic camera stereo pair creation is possible. Therefore, with known ball 2D image coordinates, the 3D real ball coordinates can be reconstructed and the ball trajectory can be estimated. The performance of the proposed method is tested on a synthetic data set, including 3Ds Max rendering and real data scenarios. The mean camera pose error calculated for data biased with keypoint detection errors is approximately equal to 0.013% of the measurement volume. For the real data experiment with a human hand phantom, it is possible to determine the presence of the human phantom on the basis of the ball reflection attitude.