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Two orthogonal least squares methods of the points approximation by a set of parallel planes are presented. Such an approximation can be used to study the measurement details of using a coordinate measuring machine (CMM). A calibrated gauge block and a CMM with a touch measuring probe were used in the experimental verification. A comparison of the different CMM strategies is provided. [ABSTRACT FROM AUTHOR]

This paper describes a diameter measurement method for micro-spheres via coherent scanning interferometry (CSI) with a gauge block as the reference. The CSI system measures the height difference between the sphere and gauge block surface from both the front and back sides; then, the diameter is calculated from the measured heights via CSI and the gauge block length. For the glass sphere measured in this study, the diameter was found to be 270.556 µm with an uncertainty of 0.16 µm (k=2). Interestingly, by selecting a gauge block that matches the sphere diameter, the measurement uncertainty remained virtually unchanged, even for different sphere diameters; the proposed method achieved a relative uncertainty of 10-3–10-4. By utilizing the calibrated reference and the highly sensitive CSI system, and based on the comparator principle, the proposed method enables accurate diameter measurement without requiring specific measurement instruments. [ABSTRACT FROM AUTHOR]

The paper discusses the derivation of an accurate coordinate measuring system consisting of two, three, or four sensors based on the records of four fixed laser triangulation sensors done for a gauge block in movement. Three-dimensional case is considered. In the simulations, using a set of distances quadruplets, parameters of sensors in a local sensors coordinate system are determined through a least squares minimization process using the Differential Evolution approach. The influence of the measurement and rounding inaccuracy on the identification accuracy using numerical simulation methods are assessed. [ABSTRACT FROM AUTHOR]

A simple technique for measuring the phase change on reflection with application to gauge block calibration is presented. The proposed technique measures the optical constants of the steel gauge block and the auxiliary platen which is made of fused silica using polarized light. The presented method considers the principal angle of incidence method and avoids the deviation of the quarterwave plate from exact λ/4 value. The phase change angle could be determined with high accuracy (±2°) and the uncertainty contribution of the phase change correction in the gauge block calibration could be reduced to (± 2 nm). The resulted phase change correction value was compared to the value obtained by interferometry using the stack method. The presented method is proposed to be convenient with the contactless measurement of gauge block length using the double ended interferometer. [ABSTRACT FROM AUTHOR]

This paper presents a micro-coordinate measuring machine (micro-CMM) for large-scale dimensional measurement of a micro-slit on a precision die coater by using a shear-mode micro-probe. A glass micro sphere with a nominal diameter of 52.3 urn was attached on one end of a tapered glass capillary tube as a probe tip ball. The micro-slit width of a slot die coater with a nominal slit width of 85 um was measured by the micro-CMM. The probe tip was placed in the slit for the measurement. The effective working length of the probe was confirmed experimentally to be at least 1 mm. In order to measure the gap width uniformity over the entire slot die length of 200 mm, an air-bearing linear slide with a travelling stroke of 300 mm was employed in the micro-CMM to position the probe along the length direction of the slot die. The angular alignment error and the motion error of the air-bearing linear slide as well as those of the stages for positioning the probe along the direction perpendicular to the length direction of the slot die were investigated for evaluation of the expanded uncertainty of gap width measurement. [ABSTRACT FROM AUTHOR]

This paper presents a method implemented in a system for automatic contactless calibration of gauge blocks designed at ISI ASCR. The system combines low-coherence interferometry and laser interferometry, where the first identifies the gauge block sides position and the second one measures the gauge block length itself. A crucial part of the system is the algorithm for gauge block alignment to the measuring beam which is able to compensate the gauge block lateral and longitudinal tilt up to 0.141 mrad. The algorithm is also important for the gauge block position monitoring during its length measurement. [ABSTRACT FROM AUTHOR]

We have developed an interferometer for gauge block calibration based on phase shifting algorithms. The measurement process can provide flatness, parallelism, and length. Wavelength values need to be corrected according to the refractive index of air. This correction is obtained indirectly using Edlén's equation. High-resolution sensors provide the temperature, pressure, and relative humidity readings. To preserve stability, the interferometer is encapsulated in a chamber with active temperature control. Its design, measurement principle, calibration, stability, and reproducibility are analyzed. Since one goal is to employ robust and cheap diode lasers as light sources, we describe the system developed to stabilize a red laser diode using a mode locking technique with a reference gas cell. The instruments and assembly are used to avoid the Doppler effect in the gas cell, which would limit wavelength resolution. Several experiments are carried out to restrict the influence of environmental changes, which affect laser diode frequency. [ABSTRACT FROM AUTHOR]

As it is know, the gauge blocks sizes should remain within a desired dimensional constancy in time. Many users have reported a change of the dimension of the hardened and aged gauge steel blocks. This dimensional instability has been report as shrinkage, growth or as change from one to the other at different times of measurement. Dimensional stability is a prime requirement for gage blocks, and stability could be affect by the structure and stresses within materials. The used steels have a metastable structure, which has a tendency to martensite transformation with an expected reduction in volume effect. After tempering operations, the phases are also metastable and can transform into bainite upon ageing at room temperature with an increasing effect. Residual stresses can induce in the gauge blocks at room temperature, a growth or shrinkage depending on the sign and orientation of the stress. Several other characteristics and properties are necessary in addition to dimensional stability: a high degree of surface finishing; flatness of surfaces; a parallelism of opposite faces for precise measurements, characteristics that are related to the surface hardness and structure. The coefficient of thermal expansion should be equal to those of high carbon steel. The materials with zero or very low coefficients are the best. Accuracy temperature control is essential and both gauge block and the measured piece must to come to the same temperature. [ABSTRACT FROM AUTHOR]

A novel method of gauge block measurement without wringing onto a glass platen is proposed. By using tandem low-coherence interferometry to perform remote measurements, wringing is rendered unnecessary. To measure its length, a gauge block for measurement without wringing is set several millimeters above a glass platen that is positioned on a triangle interferometer such that the distances between the surfaces of the block and the reflection surface of the platen can be measured from opposite directions. By using tandem low-coherence interferometry with a He-Ne laser as a reference length standard, gauge blocks with nominal lengths of 5, 10 and 75 mm have been measured remotely with an expanded uncertainty of about 86 nm [ABSTRACT FROM AUTHOR]

This paper presents the evaluation of the uncertainty for the length measurement of gauge blocks by optical interferometry. In order to improve the gauge block calibration method and to decrease measurement uncertainty the old Zeiss-Kösters gauge block interferometer has been modified and improved by DMDM (Directorate of Measures and Precious Metals of Serbia). The main modification of the interferometer covers introduction of two laser sources, as new wavelength standards, as well as new hardware system and interferometer software, developed to completely automate the calibration process. The validation of the new measurement procedure details the uncertainty budget. The measurement method and model equation, which serves as the basis for the uncertainty evaluation is described. The uncertainty evaluation is performed in accordance with the document JCGM 100:2008-Evaluation of measurement data – Guide to the expression of uncertainty in measurement (GUM). [ABSTRACT FROM AUTHOR]

In this paper we describe the progress we have made in our simultaneous length measurement and the femtosecond comb interferometric spectroscopy in a conventional arrangement with a moving mirror. Scanning and detection over an interval longer than the distance between two consecutive pulses of the frequency comb allow for a spectral resolution of the individual frequency modes of the comb. Precise knowledge of comb mode frequency leads to a precise estimation of the spectral characteristics of inspected phenomena. Using the pulse train of the frequency comb allows for measurement with highly unbalanced lengths of interferometer arms, i.e. an absolute long distance measurement. Further, we present a non-contact (double sided) method of measurement of the length/thickness of plane-parallel objects (gauge blocks, glass samples) by combining the fs comb (white light) with single frequency laser interferometry. The position of a fringe packet is evaluated by estimating the stationary phase position for any wavelength in the spectral band used. The repeatability of this position estimation is a few nanometres regardless of whether dispersion of the arms is compensated (transform limited fringe packet ∼10 fringes FWHM) or highly different (fringe packet stretched to >200 fringes FWHM). The measurement of steel gauge block by this method was compared with the standard method, and deviation (+13 ± 12) nm for gauge blocks (2 to 100) mm was found. The measurement of low reflecting ceramic gauges or clear glass samples was also tested. In the case of glass, it becomes possible to measure simultaneously both the thickness and the refractive index (and dispersion) of flat samples. [ABSTRACT FROM AUTHOR]

We developed a Fabry-Perot etalon to select high-frequency parts of repetition-frequency modes of a short pulsed, mode-locked fiber laser at the wavelength of 1.55 µm. The 2 GHz repetition-modified laser is transmitted to an unbalanced Michelson interferometer with gauge blocks wrung on a platen. Two interference fringes were generated from the gauge block and platen at different positions. The interference fringes have a temporal coherence pattern and can make positioning in space easy. The length of the gauge block was directly determined from different positions of the two interference fringes, without using the excess fractions method. [ABSTRACT FROM AUTHOR]

In this paper, a novel principle of contactless gauge block calibration is presented. The principle of contactless gauge block calibration combines low-coherence interferometry and laser interferometry. An experimental setup combines Dowell interferometer and Michelson interferometer to ensure a gauge block length determination with direct traceability to the primary length standard. By monitoring both gauge block sides with a digital camera gauge block 3D surface measurements are possible too. The principle presented is protected by the Czech national patent No. 302948. [ABSTRACT FROM AUTHOR]

A displacement interferometer is described for measuring gauge blocks, in which a spatial filter is used to combine a laser beam with a white-light beam, and the length of the block is calculated from the phase differences of the laser signal corresponding to the centers of gravity of the achromatic fringes from the gauge and from the reference plate. [ABSTRACT FROM AUTHOR]