scholarly journals Reference Measurement of Roundwood by Fringe Projection

2021 ◽  
Vol 71 (4) ◽  
pp. 352-361
Author(s):  
Christian Keck ◽  
René Schödel
Keyword(s):  
International System ◽  
Fringe Projection ◽  
Evaluation Procedure ◽  
Systematic Effect ◽  
Projection System ◽  
Reference Measurement ◽  
System Of Units ◽  
Coordinate Metrology ◽  
Unit Of Length ◽  
Test Objects

Abstract The metrological verification of log scanners requires logs with accurately known dimensions as test objects. The measurement of the lengths and diameters must be traceable back to the SI (International System of Units) unit of length. The results have to be reported with the corresponding measurement uncertainties. The uncertainties are required to be 5 to 10 times lower than the corresponding maximum permissible errors allowed for the log scanner under test. This article presents a procedure for the reference measurement of logs using an off-the-shelf fringe projection system along with uncertainty budgets for the measured dimensions. The length and diameters are determined from the highly resolved mesh obtained by fringe projection using techniques from computational geometry and coordinate metrology. Corrections are applied to the length and diameter values to remove the systematic effect caused by scattering of projected light below the partially transparent log surface. The influence of the fringe projection system on the measured dimensions is determined by measurements of calibrated artifacts, which also provide the traceability back to the SI unit of length. The measurement is illustrated by the example of a log with a length of 2 m and a diameter of 280 mm. The corresponding uncertainty budgets, confirmed by repeat measurements, result in expanded uncertainties (confidence interval 95%) of 6 mm and 0.13 mm for length and diameter, respectively. These low values qualify the fringe projection measurement along with accompanying evaluation procedure to provide logs as reference objects for the verification of log scanners.

scholarly journals System of astronomical constants in the relativistic framework

1986 ◽  
Vol 114 ◽  
pp. 187-188
Author(s):  
T. Fukushima ◽  
M. K. Fujimoto ◽  
H. Kinoshita ◽  
S. Aoki
Keyword(s):  
Light Propagation ◽  
International System ◽  
Propagation Time ◽  
Long Baseline ◽  
System Of Units ◽  
Numerical Transformation ◽  
Unit Of Length ◽  
Range Rate ◽  
Definition Of ◽  
Astronomical Constants

The relation between the units and the readings of time and space coordinates of the terrestrial and the barycentric frames is discussed from the viewpoint of general relativity. Attention is paid to the unit of space coordinates since the International Astronomical Union (IAU) regulates only the unit of time coordinate in the above two frames. Two definitions on unit of length are examined and their effects on the numerical expression of coordinate transformation, equations of planetary motions, and those for light propagation time are discussed. A clear conflict is found between the IAU(1976) recommendation on the definition of the time-scales in different frames and the statement that all constants in the IAU(1976) new system of astronomical constants are defined in terms of the international system of units (SI units). In order to dissolve this conflict, one of the two examined definitions on unit of length is proposed to be adopted, which requests the least alteration on the current procedures to analyze the astrometric observations such as radar/laser rangings, range and range-rate measurements, and very long baseline interferometric observations. An interpretation of numerical values in the IAU(1976) system of astronomical constants is also presented. It is stressed that the definition proposed in this paper requires that a slightly different formula from the current one be used in the numerical transformation of coordinates between the terrestrial and the barycentric frames.

Performance criteria for reference measurement procedures and reference materials

2015 ◽  
Vol 53 (6) ◽  
Author(s):  
Heinz Schimmel ◽  
Ingrid Zegers
Keyword(s):  
Reference Materials ◽  
International System ◽  
Metrological Traceability ◽  
International Standards ◽  
Performance Criteria ◽  
Systematic Bias ◽  
End User ◽  
Reference Measurement ◽  
System Of Units ◽  
Measurement Results

AbstractThe concept of metrological traceability of measurement results to property values assigned to measurement standards of higher metrological order or to the International System of Units (SI) through sequential calibrations, using reference materials and reference measurement procedures, plays a key role in ensuring that end user measurement procedures perform at an acceptable level in the clinical context. The aim is that measurement results produced over time or by different end users or with different end user measurement procedures for the same measurand will be equivalent within their corresponding uncertainties. These goals can only be reached under certain conditions and if requirements laid down in international standards on calibration concepts, reference measurement procedures and reference materials are fulfilled. Calibration hierarchies have to be implemented correctly and parameters contributing to measurement uncertainty and systematic bias need to be controlled and eliminated, respectively, by technically improving methods and reference materials and intermediate calibrators used for effectively achieving equivalence of measurement results and for meeting analytical performance requirements for in vitro diagnostic devices.

Dimensions of plane and solid angles and their units in the International System of Units (SI)

2020 ◽  
pp. 26-32
Author(s):  
M. I. Kalinin ◽  
L. K. Isaev ◽  
F. V. Bulygin
Keyword(s):  
Solid Angle ◽  
International System ◽  
International Committee ◽  
Plane Angle ◽  
Arc Length ◽  
Weights And Measures ◽  
International System Of Units ◽  
System Of Units ◽  
In Series ◽  
Solid Angles

The situation that has developed in the International System of Units (SI) as a result of adopting the recommendation of the International Committee of Weights and Measures (CIPM) in 1980, which proposed to consider plane and solid angles as dimensionless derived quantities, is analyzed. It is shown that the basis for such a solution was a misunderstanding of the mathematical formula relating the arc length of a circle with its radius and corresponding central angle, as well as of the expansions of trigonometric functions in series. From the analysis presented in the article, it follows that a plane angle does not depend on any of the SI quantities and should be assigned to the base quantities, and its unit, the radian, should be added to the base SI units. A solid angle, in this case, turns out to be a derived quantity of a plane angle. Its unit, the steradian, is a coherent derived unit equal to the square radian.

scholarly journals A quantum ampere

2020 ◽  
Vol 87 (4) ◽  
pp. 258-265
Author(s):  
Luca Callegaro
Keyword(s):  
Electric Current ◽  
International System ◽  
International System Of Units ◽  
System Of Units ◽  
Elementary Charge ◽  
User Friendly

AbstractThe revision of the International System of Units (SI), implemented since 20 May 2019, has redefined the unit of electric current, the ampere ( A), linking it to a fixed value of the elementary charge. This paper discusses the new definition and the realisation of the electrical units by quantum electrical metrology standards, which every year become more and more accessible, reliable and user friendly.

scholarly journals Absolute Phase Retrieval Using One Coded Pattern and Geometric Constraints of Fringe Projection System

2018 ◽  
Vol 8 (12) ◽  
pp. 2673 ◽  
Author(s):  
Xu Yang ◽  
Chunnian Zeng ◽  
Jie Luo ◽  
Yu Lei ◽  
Bo Tao ◽  
...  
Keyword(s):  
Phase Shift ◽  
Phase Retrieval ◽  
Code Word ◽  
Geometric Constraints ◽  
Fringe Projection ◽  
Average Intensity ◽  
Fringe Order ◽  
Projection System ◽  
Absolute Phase ◽  
Three Phase

Fringe projection technologies have been widely used for three-dimensional (3D) shape measurement. One of the critical issues is absolute phase recovery, especially for measuring multiple isolated objects. This paper proposes a method for absolute phase retrieval using only one coded pattern. A total of four patterns including one coded pattern and three phase-shift patterns are projected, captured, and processed. The wrapped phase, as well as average intensity and intensity modulation, are calculated from three phase-shift patterns. A code word encrypted into the coded pattern can be calculated using the average intensity and intensity modulation. Based on geometric constraints of fringe projection system, the minimum fringe order map can be created, upon which the fringe order can be calculated from the code word. Compared with the conventional method, the measurement depth range is significantly improved. Finally, the wrapped phase can be unwrapped for absolute phase map. Since only four patterns are required, the proposed method is suitable for real-time measurement. Simulations and experiments have been conducted, and their results have verified the proposed method.

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