Laser Tracker and Terrestrial Laser Scanner Range Error Evaluation by Stitching.

Laser trackers (LTs) are dimensional measurement instruments commonly employed in the manufacture and assembly of large structures. Terrestrial laser scanners (TLSs) are a related class of dimensional measurement instruments more commonly employed in surveying, reverse engineering, and forensics. Commercially available LTs typically have measurement ranges of up to 80 m.

ASME B89.4.23 Performance Evaluation Tests and Geometry Errors in X-Ray Computed Tomography Systems.

A documentary standard produced by the American Society of Mechanical Engineers (ASME) for performance evaluation of industrial X-ray computed tomography (XCT) systems for dimensional measurements was released in early 2021. This standard, ASME B89.4.

Validation of the network method for evaluating uncertainty and improvement of geometry error parameters of a laser tracker.

Five National Metrology Institutes (NMIs) worked together to validate the assessment of laser tracker's (LT) uncertainty for large scale dimensional metrology in subsequent measurements using the network method. The LT uncertainty is assessed by measuring a set of a fixed network of targets from different LT positions. Afterward, we must perform a "bundled adjustment" of all the measurements to determine the transformations of the LT positions that minimize the residuals (differences) between a computed "virtual" group of targets, called composite points, and the redundant targets coming from the LT positions transformed to a unique LT position.

X-Ray Computed Tomography Instrument Performance Evaluation, Part III: Sensitivity to Detector Geometry and Rotation Stage Errors at Different Magnifications.

With steadily increasing use in dimensional metrology applications, especially for delicate parts and those with complex internal features, X-ray computed tomography (XCT) has transitioned from a medical imaging tool to an inspection tool in industrial metrology. This has resulted in the demand for standardized test procedures and performance evaluation standards to enable reliable comparison of different instruments and support claims of metrological traceability. To meet these emerging needs, the American Society of Mechanical Engineers (ASME) recently released the B89.

Performance Evaluation of Terrestrial Laser Scanners - A Review.

Terrestrial laser scanners (TLSs) are increasingly used in several applications such as reverse engineering, digital reconstruction of historical monuments, geodesy and surveying, deformation monitoring of structures, forensic crime scene preservation, manufacturing and assembly of engineering components, and architectural, engineering, and construction (AEC) applications. The tolerances required in these tasks range from few tens of millimeters (for example, in historical monument digitization) to few tens of micrometers (for example, in high precision manufacturing and assembly). With numerous TLS instrument manufacturers, each offering multiple models of TLSs with idiosyncratic specifications, it is a considerable challenge for users to compare instruments or evaluate their performance to determine if they meet specifications.

Terrestrial laser scanner calibration and performance evaluation using the network method.

In this paper, we discuss two aspects concerning terrestrial laser scanners (TLSs) - error model calibration and performance evaluation. Error model calibration is the process of determining parameters of an error model to improve the accuracy of TLSs. Performance evaluation refers to a series of tests to determine if a TLS meets specifications provided by the manufacturer.

Improvised Long Test Lengths via Stitching Scale Bar Method: Interim Testing of Laser Trackers.

Performance verifications of laser tracker systems (LTSs) often rely on calibrated length artifacts that are 2.3 m in length or more, as specified in International Standards Organization (ISO) and American Society of Mechanical Engineers (ASME) standards. The 2.

Improvised Long Test Lengths via Stitching Scale Bar Method: Performance Evaluation of Terrestrial Laser Scanners per ASTM E3125-17.

Periodic performance evaluation is a critical issue for ensuring the reliability of data from terrestrial laser scanners (TLSs). With the recent introduction of the ASTM E3125-17 standard, there now exist standardized test procedures for this purpose. Point-to-point length measurement is one test method described in that documentary standard.

X-ray Computed Tomography Instrument Performance Evaluation, Part I: Sensitivity to Detector Geometry Errors.

X-ray computed tomography (XCT), long used in medical imaging and defect inspection, is now increasingly used for dimensional measurements of geometrical features in engineering components. With widespread use of XCT instruments, there is growing need for the development of standardized test procedures to verify manufacturer specifications and provide pathways to establish metrological traceability. As technical committees within the American Society of Mechanical Engineers (ASME) and the International Organization for Standardization (ISO) are developing documentary standards that include test procedures that are sensitive to all known error sources, we report on work exploring one set of error sources, instrument geometry errors, and their effect on dimensional measurements.

X-ray Computed Tomography Instrument Performance Evaluation, Part II: Sensitivity to Rotation Stage Errors.

The development of standards for evaluating the performance of X-ray computed tomography (XCT) instruments is ongoing within the American Society of Mechanical Engineers (ASME) and the International Organization for Standardization (ISO) working committees. A key challenge in developing documentary standards is to identify test procedures that are sensitive to known error sources. In Part I of this work, we described the effect of geometry errors associated with the detector and determined their influence through simulations on sphere center-to-center distance errors and sphere form errors for spheres located in the tomographically reconstructed measurement volume.

METROLOGICAL EVALUATION OF CONTRAST TARGET CENTER ALGORITHM FOR TERRESTRIAL LASER SCANNERS.

Terrestrial Laser Scanners (TLSs) are used in a variety of large scale scanning applications such as reverse engineering, assembly of aircraft or ships and surveying. Contrast targets are used with such instruments for enabling scene registration or to establish a scale when used on a scale bar. Currently, the algorithms to calculate the centers of contrast targets (CCT) are either proprietary to the original equipment manufacturers (OEMs) or not precise and accurate.

Concept to Commercialization of an Artifact for Evaluating Three-Dimensional Imaging Systems per ASTM E3125-17.

The relative-range error test is one of several tests described in the ASTM E3125-2017 standard for performance evaluation of spherical coordinate three-dimensional (3D) imaging systems such as terrestrial laser scanners (TLS). We designed a new artifact, called the plate-sphere target, that allows the realization of the relative-range error tests quickly and efficiently without the need for alignment at each position of the test.Use of a simple planar/plate target requires careful alignment of the target at each position of the relative-range error test, which is labor-intensive and time-consuming.

METHODS AND CONSIDERATIONS TO DETERMINE SPHERE CENTER FROM TERRESTRIAL LASER SCANNER POINT CLOUD DATA.

The Dimensional Metrology Group (DMG) at the National Institute of Standards and Technology (NIST) is performing research to support the development of documentary standards within ASTM E57 committee. This committee is addressing the point-to-point performance evaluation of a subclass of 3D imaging systems called Terrestrial Laser Scanners (TLSs) which are laser-based and use spherical coordinate system. This paper discusses the usage of sphere targets for this effort and methods to minimize the errors due to the determination of their centers.

Relative range error evaluation of terrestrial laser scanners using a plate, a sphere, and a novel dual-sphere-plate target.

Terrestrial laser scanners (TLS) are a class of 3D imaging systems that produce a 3D point cloud by measuring the range and two angles to a point. The fundamental measurement of a TLS is range. Relative range error is one component of the overall range error of TLS and its estimation is therefore an important aspect in establishing metrological traceability of measurements performed using these systems.

Determining geometric error model parameters of a terrestrial laser scanner through Two-face, Length-consistency, and Network methods.

Terrestrial laser scanners (TLS) are increasingly used in large-scale manufacturing and assembly where required measurement uncertainties are on the order of few tenths of a millimeter or smaller. In order to meet these stringent requirements, systematic errors within a TLS are compensated in-situ through self-calibration. In the Network method of self-calibration, numerous targets distributed in the work-volume are measured from multiple locations with the TLS to determine parameters of the TLS error model.

A Model for Geometry-Dependent Errors in Length Artifacts.

We present a detailed model of dimensional changes in long length artifacts, such as step gauges and ball bars, due to bending under gravity. The comprehensive model is based on evaluation of the gauge points relative to the neutral bending surface. It yields the errors observed when the gauge points are located off the neutral bending surface of a bar or rod but also reveals the significant error associated with out-of-straightness of a bar or rod even if the gauge points are located in the neutral bending surface.

Geometric Effects When Measuring Small Holes With Micro Contact Probes.

A coordinate measuring machine with a suitably small probe can be used to measure micro-features such as the diameter and form of small holes (often about 100 μm in diameter). When measuring small holes, the clearance between the probe tip and the part is sometimes nearly as small as other characteristic lengths (such as probe deflection or form errors) associated with the measurement. Under these circumstances, the basic geometry of the measurement is much different than it is for the measurement of a macroscopic object.

RECIST versus volume measurement in medical CT using ellipsoids of known size.

Two hundred eighty three uniaxial ellipsoids with sizes from 4 mm to 11 mm were measured with a coordinate measuring matching (CMM) and also scanned using a medical computed tomography (CT) machine. Their volumes were determined by counting voxels over a threshold, as well as using equivalent volumes from the length given by the RECIST 1.1 criterion (Response Evaluation Criteria in Solid Tumors).