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In our previous work, four environment parameters including temperature, pressure, relative humidity and carbon dioxide concentration in a long gauge block interferometer chamber were measu...

A gauge block interferometer with a vacuum chamber was designed and constructed for the measurement of gauge block lengths between 10 to 1,000 mm. In the chamber, four gauge blocks under the length measurement can be mounted on the measuring table. Furthermore, the length of all four gauge blocks can be measured continuously in one measurement. In this study, four gauge blocks with the nominal length of 125, 200, 400 and 500 mm were used for the length measurement. The environment parameters in the vacuum chamber including temperature, pressure, relative humidity and CO2 concentration were measured. The refractive index of air which depends on environment parameters was determined by using updated Edlen equation. Then, the lengths of four gauge blocks were measured and found to be 125.00025, 200.00019, 400.00070 and 500.00064, respectively.

Line structured light systems have been widely applied in the measurement of various fields. Calibration has been a hot research topic as a vitally important process of the line structured light system. The accurate calibration directly affects the measurement result of the line structured light system. However, the external environment factors, such as uneven illumination and uncertain light stripe width, can easily lead to an inaccurate extraction of light stripe center, which will affect the accuracy of the calibration. An image analysis-based framework in the calibration process was proposed for the line structure light system in this paper. A three-dimensional (3D) vision model of line structure light system was constructed. An image filtering model was established to equalize the uneven illumination of light stripe image. After segmenting the stripe image, an adaptive window was developed, and the width of the light stripe was estimated by sliding the window over the light stripe image. The light stripe center was calculated using the gray centroid method. The light plane was fitted based on the calibration points coordinates acquired by the camera system. In the measurement experiment of standard gauge block width, the maximum and minimum average deviations of 0.021 pixels and 0.008 pixels and the maximum and minimum absolute deviations of 0.023 pixels and 0.009 pixels could be obtained by using the proposed method, which implies the accuracy of the proposed method.

We reported the application of longitudinal spatial coherence (LSC) properties of a pseudo thermal light source for the topography and tomography of multilayered objects. To synthesize the pseudo thermal light source, He–Ne laser (632.8 nm) is passed through a rotating diffuser and multi-multimode fiber bundle. We demonstrated the topography of gauge block with height difference of 20 µm and the tomography of RBC and onion cell slice placed onto one another. The higher axial resolution is achieved for sectioning due to LSC property of the light source which is otherwise not possible by means of purely temporal coherence property of He–Ne laser.

3D measurement of micro-sized components by Fringe projection profilometry (FFP) requires fringe patterns with high spatial resolution. In order to project high-resolution and fine fringe patterns, a MEMS scanning module is used to project the precise time-modulated line laser stripes into space to form high-resolution laser fringes. The micro-vibration mirror in the MEMS module works in a resonant state, and the internal position detection of the MEMS module generate precise time reference signal. The reference signal is used to project spatial fringe patterns and ensure the stability and high resolution. The high-resolution laser fringe patterns generated by MEMS scanning module are projected to micro-sized components for 3D measurement. The measurement experiment shows that the spatial resolution of the projected fringes can reach 0.47 mm and the phase shift resolution is 0.12 mm. The measurement results show that the tiny height changes of the measured components can be well measured and presented. The standard gauge block with a height of 1 mm is measured, and the root mean square error of the measured height is 0.037 mm. It has a good prospect to apply the proposed method to the 3D measurement of micro-sized components.

A system of measuring blind hole depth of the thermostat shell is designed by laser triangle method. The laser lines are extracted by using sub-pixel grayscale gradient arithmetic. And the standard gauge block is used to compensate the error caused by the measurement system. According to the shape and material of the shell, the CCD camera receives the shot picture by using the linear laser which is vertical to motion shell. By using the technology of three-dimensional reconstruction and point cloud splicing, the three-dimensional stereogram of the thermostat shell is got. And the thermostat shell is indirectly measured. The experiment shows that the system can effectively solve the problem of shell depth measurement. The arithmetic is simple. Compared with the traditional laser triangulation method, the accuracy has been improved by 6-8% by using compensation method based on standard gauge block. This system has a good reference and significance for other similar products.

A calibration pattern with linear light method for profile vision measurement is proposed. A plan for calibration pattern is made which of the pattern pins can fold back to pattern plate in accordance with rows separately. The unfolding pattern pins are photographed with linear light crossing that vertically one row at a time. The mathematical expression of transforming physical plane into pixel plane is derived by physical coordinates and pixel coordinates. With the least-square method the calibration coefficient is made. The method is validated through the means that magnetic gauge block used as a higher precision measurement standard is close to the profile. The experiment indicates that it is avoided that the pattern pins from different rows interrupt the linear light, and the profile measurement error is better than 0.2 mm.

Double-ended gauge block interferometers (DEI) are becoming more and more established. This paper suggests its extension for enabling interferometric measurement of diameter topographies of spheres as an alternative to the existing spherical Fizeau interferometers. The extension essentially consists in the addition of two lenses which are as similar as possible, which are arranged symmetrically around the sphere to be measured. The determination of the diameter topography from the interferometric measurements with inserted and without sphere in the extended DEI is derived and specific aspects are discussed. An adjustment strategy for the extended DEI is also suggested. In conclusion, the proposed extension appears to be a promising measurement tool, especially for measuring small spheres, as required for applications in coordinate metrology.

A compact and inexpensive iodine-stabilized diode laser system with an output at 531 nm has been applied to long gauge block measurements. Although the optical frequency of the output beam was widely modulated (modulation width of ∼22 MHz), the coherence length and interference phase stability are sufficiently long and high, respectively, for the interferometric measurement of long gauge blocks of up to 1000 mm in length. The effective uncertainty of laser frequency in the interferometric measurement was theoretically and experimentally confirmed to be less than 10−9.

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 (±2o) 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

The development of a new probing method to inspect the inner diameter of micro-scale holes is presented in this paper. This was accomplished by contact detection using acoustic emission with a O170 μm rotating wire probe tip. Contact is detected when the rotating probe approaches and impacts the hole’s inner surface. The effective diameter of the rotating probe is calibrated by using a high precision grade 0 Mitutoyo gauge block. The wire rotating probe used was fabricated with micro stainless steel wire and micro tubes. The probe’s effective diameter was compensated for in the measurement of the hole. The probe was used to measure the diameter and the roundness of micro-scale holes. Probes used in previous publications have different geometry than the probe in this paper and are used almost exclusively for external dimensions. Micro-scale holes of less than 1.0 mm in diameter and 10 mm in depth are successfully measured and the 3D profile is created accordingly. Also, the out-of-roundness values of each level spacing, 50 μm apart in height, are calculated.

We demonstrate a simple adaptation of the venerable Hilger-Watts gauge-block interferometer capable of performing automated, traceable calibrations of gauge block length by phase-stepping interferometry (PSI). We discuss the selection of robust PSI filtering algorithms to counteract in software the flaws of the hardware implementation, including markedly nonsinusoidal fringes and inhomogeneous phase step size. We find that the length measurement errors attributable to the phase measurement can be reduced to 0.6 nm, even with a simple retrofit to an instrument not originally designed for PSI.

This paper presents a new electronic Vernier fringe counter for the wavelength measurement of a diode laser in a scanning interferometer. The system is intended to be a low cost alternative to commercial systems used for gauge block calibration. The counter stage and phase coincidence detector are made with a microcontroller and high-speed CMOS logic to achieve the required resolution. The microcontroller also can synchronize with other elements to make a fully automated measurement system. This electronic design improves the resolution of the electronic counters in the previous designs.

Absolute length calibration of gauge blocks traceable to the definition of meter is an important task of the national metrology institutes responsible for providing reliable length artifacts for industrial use. The length of a gauge block (henceforth, represented as GB) is defined in ISO 3650 as the distance between its one measuring face and the surface of an auxiliary platen on which the other measuring face has been wrung. Accordingly, in central length calibration of K-grade GBs using interferometry, it is required that they be wrung onto an auxiliary platen whose characteristics are the same as the measuring face of the GBs. According to this definition, the length of a GB consists of its mechanical length between two faces and the wringing film thickness. This definition is practical and reasonable in many cases because GBs are used as length standards with wringing. Also this calibration method has the advantage that the thickness of the wringing film is propagated appropriately when lower grade GBs are calibrated by comparison to higher grade GBs via a mechanical comparator. In terms of this paper is briefly described interferometry method of gauge blocks calibration. The paper was written in conjunction with Czech Metrology Institute.

Many workers have published various methods to measure refractive index of various liquids. Mostly, the measurement results are not traceable to SI units. A novel method is developed at CSIR-NPL, India (NPLI) to measure refractive of index of liquids using gauge blocks, metrological microscope and displacement laser interferometer. A vessel with flat bottom is chosen to hold the liquid under test. A pair of gauge blocks of different lengths is fixed in the vessel. The vessel is arranged under a vertically movable microscope. A calibrated displacement laser interferometer is attached to the microscope stage. The microscope is focused to the surface of gauge block before poring liquid. After poring liquid in the vessel, the microscope is moved vertically to regain the focussed image of surface of submerged gauge blocks. The measurement method is simulated mathematically. The refractive index of liquid medium is calculated using this mathematical model. Refractive index of water, isopropyl alcohol is measured. Various error contributing sources are identified. The measurement uncertainty is evaluated.

Gauge block plays an important role in dimensional metrology as a standard for calibration. There are several techniques to calibrate gauge block, one of which is an optical method, such as, Michelson interferometer. The interference pattern is recorded for gauge block comparison. The stability of light source is important for the calibration. In this work, we developed a reliable constant current control circuit of 7 mW laser diode for the gauge block interferometer with a closed-loop feedback temperature control, which utilized the advantage of an embedded system. A PID controller was used to maintain the temperature at 25.0 °C within ± 0.5 °C of uncertainty. We tested the system for 60 minutes by monitoring the stability of the laser wavelength. The results showed that the wavelength of the laser was unstable during the first 20 minutes before becoming constant at 655.525 nm.

In this paper, a novel Newton interferometer, which consists of a phase compensation module (PCM) and a Newton interference module (NIM), is proposed to measure the surface contour such as surface flatness and surface step-height. Where the PCM separates the incident beam into two sub-beams; and the NIM further divides each of the two sub-beams into two sub–sub-beams and then exports an interference pattern, which is formed by the interference of the beams having optical path difference within the coherence length, with the phase information of the contour. Two measurement modes, phase-shifting and phase-scanning, are employed for manipulating the interference pattern and then retrieving the surface contour. The phase-shifting measurement mode, which involves a narrow-band source, is suitable for smooth surface examinations, whereas the phase-scanning measurement mode, which employs a broad-band source, can be used for smooth surface or piece-wise smooth surface measurements. This paper first introduces the measurement theory and a setup for realizing the interferometer, and then presents two experiments involving the use of the setup, one for determining the flatness of a gauge block using the phase-shifting mode and the other for measuring the step-height on a silicon substrate using the phase-scanning mode. The results of the experiments reveal the validity and feasibility of the proposed interferometer.

Double-ended interferometry has several benefits over single-ended gauge block interferometry: there is no need for wringing, which wears surfaces and requires expertise, and there is improved repeatability, since there is no variation due to inconsistent wringing conditions or form errors of the gauge block surfaces. Some disadvantages of double-ended interferometry are that absolute phase change correction is needed for the gauge block and its uncertainty has a double effect on total uncertainty. In addition, elimination of the wavefront error is more complicated than with single-ended interferometry. A simple optical modification that enables double-ended interferometer (DEI) measurements with the MIKES interferometer for long gauge blocks is presented. This modification is applicable to almost any single-ended interferometer (SEI). A procedure for evaluating the wave front correction for different parts of the interferogram of DEI is explained, and a modification and software with capability for nine-point phase stepping is presented. Three independent methods for evaluation of the phase correction were studied. One of them uses integrating sphere for the surface roughness correction and literature values for the phase change due to complex refractive index of material correction. The second evaluates the phase correction from the difference between DEI and SEI results obtained with a quartz platen. The third uses differences-from separate measurements-between the results obtained with quartz or steel auxiliary platens. Only a few gauge blocks per set need testing to obtain phase correction. SEI and DEI results with different phase correction determination methods are presented and evaluated. The uncertainty estimate for gauge block calibration with DEI gives a similar standard uncertainty to that with the best SEIs, u = (10.0 nm)2 + (118*10-9L)2 .

Application of broadband probing impulses in acoustic microscopy allows to increase depth resolution of visualization system and to improve measuring possibilities at fixed frequencies. The echo-pulse method with measuring the delay times is a basis of quantitative techniques of the pulse acoustic microscopy. To improve the accuracy of the method the attention should be paid to the changes in the echo-pulse shape that is caused by the focusing of elastic waves at the boundaries of a sample. Features of the separated echo-pulses formation, which is caused by reflecting the acoustic waves of various polarizations in the plate, are studied. The method of a stationary phase is applied to analyze the expression for the output echo-signal; dynamics in the shape transformation for individual echo-pulses depending on the focus position z are studied. Occurrence of the echo-pulse shifting dt outside the focal position is found theoretically. It is shown experimentally the echo-pulses shaping depends on focus position under the specimen. The technique with time delay correction has been applied to measure sonic velocity for standard steel gauge block. Systematic error avoided by the shape correction was 1% for the measured value of sonic velocity.

This paper focuses on obtaining high precision of a stabilized and interleaving high coherence and low coherence interferometric optical fiber system which is capable of the measurement of step height with a symmetric peak-searching method. The interferometer performing the measurement works in both modes of low coherence interferometry and high coherence interferometry simultaneously. The range of the step height is determined by the low coherence interferometric signal while the resolution of the measurement is decided by the high coherence interferometric signal which is also used to compensate for the influences induced by the environmental disturbances through a feedback loop. High addressing precision of the peak of the low coherence interferogram, which influences the measurement precision violently, has been obtained by searching symmetrically the peak from two sides of the low coherence interferogram. The maximum step height that can be measured is 6 mm, while the measurement resolution is less than 1 nm. The standard deviation of 10 times of the measurement results of a gauge block with the height of 1 mm is 0.5 nm.

In this paper we present both the design details and uncertainty budget for a National Institute of Standards and Technology (NIST)-developed high-accuracy Fizeau-type interferometer specifically adapted to measurement sphere diameter. To do this, we provide some historic details of the instrument's origins, an explanation of the clever accuracy-improving enhancements integrated into the design over the past several decades, and a detailed discussion of the role automation has played in achieving its current world-class accuracy. With utmost attention to the dominating components of a detailed uncertainty budget, we methodically improved a rather dated instrument design into a high-accuracy state-of-the-art system for sphere diameter measurement with an expanded uncertainty, U(k=2), of less than ± 10 nm for spheres with nominal diameters of between 0.4 mm and 26 mm. We conclude with a brief description of a novel application of this instrument for determining the phase-change upon reflection correction for both gauge blocks and gauge block platens. Applying corrections for phase-change upon reflection differences between different surfaces, gauge block and platen, is critically important for high-accuracy interferometric gauge block length measurements.

Metrologists at the National Institute for Standards-NIS (Egypt) develop length measuring devices to provide reliable and less expensive metrological systems for accurate measurement. Length Laboratory Group investigates the sources of errors in the absolute measurement of length using the improved Abbe vertical metroscope. The investigation includes analyzing of errors induced by optical alignment, environment, and instrument. Errors due to environment and vibration are reduced by controlling the area in which the technique is placed. The instability in the readings caused by temperature fluctuations is handled by averaging 1000 points/sec. To ensure ideal contact between the probe of the comparator and the surface of the artifact, holographic technique is used in testing the uniformity of the probe at the area of contact. Other factors influencing the measurements such as material expansion of the artifact and optical source used in the measurement are considered in the uncertainty evaluation. The uncertainty in the absolute measurement of gauge block length of 80mm is found to be ±0.2µm. The results of measuring some pieces using the absolute method are in good agreement with the corresponding reference values given in their calibration certificate.

Empirical estimation of uncertainty in dimensional metrology is a vital part in calibration processes. Uncertainty estimation in gauge block measurement mainly depends on three major areas, thermal effects, dimension metrology system that includes measurement strategy, and end standard surface perfection grades. This paper focuses precisely to estimate the uncertainty due to the geometrical imperfection of measuring surfaces and wringing thickness U ( L g +L w ) in calibration of end standards grade 0. An optomechanical system equipped with Zygo interferometer and AFM techniques have been employed. A novel protocol of measurement covering the geometric form of end standard surfaces and wrung base platen was experimentally applied. Surface imperfection characteristics of commonly used 6.5 mm GB have been achieved by AFM in 2D and 3D to be applied in three sets of experiments. The results show that there are obvious mapping relations between geometrical imperfection and wringing thickness of the end standards calibration. Moreover, the predicted uncertainties are clearly estimated within an acceptable range from 0.132 to 0.202 µm respectively. Experimental and analytical results are also presented and discussed.

This paper focuses on obtaining high measurement precision for large step-height by double-interferometry using waveform transforming technology. The interferometer performing the measurement, which is stabilized by a feedback loop and is robust enough for on-line measurement, works simultaneously in both modes of single-wavelength interferometry (SWI) and two-wavelength interferoemetry (TWI). In order to make the peak point of the TWI signal prominent and unique, the cosine-amplitude-modulated TWI signal has been transformed to be a triangular signal with the same frequency as the cosine-amplitude modulating and being in phase with it. The positions of the one-to-one corresponding peaks of the TWI signal and the triangular signal are the same. As the peak point of the triangular signal can be addressed much more precisely than that of the TWI signal, by employing the shifting range of the peak of the triangular signal instead of that of the TWI signal to determine the amplitude of the step height while using the SWI signal to measure the value of it, the system could measure the height with high precision. The standard deviation of measuring a gauge block with the height of 0.5mm is 0.8nm.

This paper shows the result of work of the Institute of Micromechanics and Photonics at Warsaw University of Technology and the Length and Angle Division of Central Office of Measures (GUM) [1] in building an automatic multiwavelength interferometric system with extended measurement range for calibration of long (up to 1 m) gauge blocks. The design of a full working setup with environmental condition control and monitoring systems, as well as image analysis software, is presented. For length deviation determination the phase fraction approach is proposed and described. To confirm that the system is capable of calibrating gauge blocks with assumed accuracy, a comparison between the results of 300 mm length gauge block measurement obtained by using other systems from the Central Office of Measures is made. Statistical analysis proved that the system can be used for high precision measurements with assumed standard uncertainty (125 nm for a length of 1 m). Finally the comparison between our results obtained for a long gauge block set (600 mm to 1000 mm long) and previous calibrations made by the Physikalisch-Technische Bundesanstalt (PTB) [2] is shown

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.

The environment parameters, i.e. temperature, pressure, humidity and CO2 concentration affecting the refractive index of air play an important role on the long gauge block measurement using interferometer. In this paper, the environment parameters in a measurement chamber had been continuously investigated more than 24 h. The refractive index was then calculated by using an updated Edlen equation. The stability of the refractive index of air in the experiment is 0.1 × 10−6 with the measurement uncertainty of 4.32 × 10−8 at the confidential level k = 2. While the sensitivity of the pressure of air was small, it was an evidence that the pressure of air mainly contributed to the stability of the refractive index of air due to its large variation. Furthermore, the calculated refractive index of air was employed to correct the length of long gauge blocks. The correction for 1 m long gauge block in interferometer system is 0.270 mm, 0.269 mm and 0.267 mm which are respectively based on the three laser wavelengths at 532 nm, 633 nm and 780 nm.

A new type nanometer Coordinate Measuring Machine(CMM) stage which meets the Abbe principle in three-dimensional directions is proposed to avoid the Abbe error in conventional CMMs and reduce the guide motion error that influences on the nano-CMM measurement uncertainty.The stage can move in three dimensional directions and its x guide and y guide are in a coplanar structure.The three measuring lines of the stage are orthogonal and intersect at one point which coincides with the center of a probe.Moreover,the measuring lines of x measurement system and y measurement system are coplanar with the plane of the xy stage.According to the characteristics of this stage,the impacts of various errors on the stage are analyzed,the main source errors to the measurement uncertainty are given and new correction methods for those errors are proposed.Finally,two pieces of first gauge block are measured on the developed stage.Measurement results show that the standard deviation of flatness error of first gauge block working surface is 11 nm,and that of step height is about 21 nm and the difference between the average of step heights and the calibrated value is about 1 nm.The theoretical analysis and experiment show that the nano-CMM avoids the impact of various error sources,especially the impact of Abbe error,and can be used in high-precision three-dimensional measurement.

A micro Coordinate Measuring Machine (CMM) with the measurement volume of 50 mm × 50 mm × 50 mm and measuring accuracy of about 100 nm (2σ) has been developed. In this new micro CMM, an XYZ stage, which is driven by three piezo-motors in X, Y and Z directions, can achieve the drive resolution of about 1 nm and the stroke of more than 50 mm. In order to reduce the crosstalk among X-, Y- and Z-stages, a special mechanical structure, which is called co-planar stage, is introduced. The movement of the stage in each direction is detected by a laser interferometer. A contact type of probe is adopted for measurement. The center of the probe ball coincides with the intersection point of the measuring axes of the three laser interferometers. Therefore, the metrological system of the CMM obeys the Abbe principle in three directions and is free from Abbe error. The CMM is placed in an anti-vibration and thermostatic chamber for avoiding the influence of vibration and temperature fluctuation. A series of experimental results show that the measurement uncertainty within 40 mm among X, Y and Z directions is about 100 nm (2σ). The flatness of measuring face of the gauge block is also measured and verified the performance of the developed micro CMM.

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.

The mounting eccentric error is one of the largest error sources for circular grating angle sensors (CGASs). To improve the measuring accuracy of CGASs, one error compensation method based on mounting eccentricity is proposed in this paper. The mounting eccentricity and measuring error of CGASs was modeled after analysis. Six joints mounted with CGASs were used in the eccentric error compensation experiment. The rotation error of the joints was calibrated with a coordinate measuring machine and a gauge block. Then with the calibration data, the parameters of the eccentric error compensation model were calculated. The experimental result shows that after error compensation the rotation angle errors of the joints are reduced about 58 to 543 times.

Based on dual polarization competition laser, we develop a new height gauge. By inserting a quartz crystal plate into the laser cavity, one laser beam splits into two orthogonally linear polarized laser beams, which appear one after another with the change in cavity length. After detecting their intensities, we obtain two power-turning curves. The longitudinal mode spacing is divided into 4 equal zones and each one has different intensity phenomena, which provides a new method of height measurement. According to experiments, the direct measuring range of this new method is 12 mm with resolution of 79.1 nm, and the indirect measuring range can be increased using first grade gauge blocks and a liftable platform. Compared to other height gauges such as vernier gauge, inductance sensor and gauge block interferometer, this new instrument has the advantage of self-calibration and simple structure without frequency stabilization system.

In this paper, taking MM6 metallographic microscope 160 × as an example, one kind of new method is studied on measuring actual total magnification of metallographic microscope by measuring digital images, the digital image is virtual image viewed through eyepiece of microscope and acquired by digital camera instead of eyes. Results show: 1) The digital images of 5/100 ocular micrometer and 1/100 stage micrometer in the eyepieces of microscope are acquired. The digital images of the 5 grade gauge block, which is 5mm length and is from camera 250 mm, are acquired in the same acquiring conditions. The lengths of the ocular micrometer and gauge block in the digital image are measured, and then the magnification of eyepieces is calculated. The lengths of the ocular micrometer and stage micrometer in the same digital image are measured, and then the magnification of objectives and tube factor is calculated. The actual total magnification of metallographic microscope is the product of magnification of eyepieces and magnification of objectives and tube factor; 2) For 160 × magnification of MM6 metallographic microscope, the measurement result of actual total magnification are stated as: 154.8 ×, U = 2.8 ×, k = 2, and the actual relative deviation is - 3.2%. 3)The digital image measuring method for actual total magnification of metallographic microscope can be a standardized method.

Biometric analyses of quantitative traits in eyes of mice can reveal abnormalities related to refractive or ocular development. Due to the small size of the mouse eye, highly accurate and precise measurements are needed to detect meaningful differences. We sought a non-contact measuring technique to obtain highly accurate and precise linear dimensions of the mouse eye. Laser micrometry was validated with gauge block standards. Simple procedures to measure eye dimensions on three axes were devised. Mouse eyes from C57BL/6J and rd10 on a C57BL/6J background were dissected and extraocular muscle and fat removed. External eye dimensions of axial length (anterior-posterior (A-P) axis) and equatorial diameter (superior-inferior (S-I) and nasal-temporal (N-T) axes) were obtained with a laser micrometer. Several approaches to prevent or ameliorate evaporation due to room air were employed. The resolution of the laser micrometer was less than 0.77 microns, and it provided accurate and precise non-contact measurements of eye dimensions on three axes. External dimensions of the eye strongly correlated with eye weight. The N-T and S-I dimensions of the eye correlated with each other most closely from among the 28 pair-wise combinations of the several parameters that were collected. The equatorial axis measurements correlated well from the right and left eye of each mouse. The A-P measurements did not correlate or correlated poorly in each pair of eyes. The instrument is well suited for the measurement of enucleated eyes and other structures from most commonly used species in experimental vision research and ophthalmology.

Based on the study of basic principle of interferometry using 2-D FFT arithmetic,a method to measure the length is proposed.The gauge block,as a measured sample,is placed into the light path in a Twyman-Green interferometer,and the interference fringes are generated between the reference beam and the reflected beam of the tested block upper surface and the assistant plane respectively.The interferogram is collected by a image acquisition system.The algorithm processing software is used to achieve block edge identification,region extension,filtering,phase unwrapping etc.The length distribution with block information can be obtained in the whole field and the length of the gauge block can be obtained automatically.The results indicate that the proposed method has advantages of high precision,whole field and non-contact in the measuring.

Practical length standards are remotely measured using a tandem low coherence interferometer through an optical fiber network for communication of about 20 km length between Tsukuba City and Tsuchiura City in Japan. The reference low-coherence interferometer is installed at the National Institute of Advanced Industrial Science and Technology (AIST) and the measurement interferometer with a gauge block of 100 mm nominal length is installed at a calibration laboratory in Tsuchiura City. The optical fibers work as a common path for the tandem interferometric system. Interference fringes are generated when the optical path difference between the reference and measurement interferometers is equal, and thus the gauge block is measured within a standard uncertainty of 46 nm remotely.

Vertical metro-scopes using Abbe’s principle AVM are used for different dimensional measurements. The accuracy of their measurement is low compared to other available techniques used in the calibration of gauge blocks. This uncertainty can be improved through the use of laser interferometer system in combination with it. This paper describes the improvement, the results of the calibration of a set of gauge blocks and the uncertainty budget for such a calibration. The uncertainty of such calibration is estimated to be within ± (0.06+L/650) *m; L in mm; for gauge blocks less than 200 mm. An inter-comparison between the results of such improved AVM and the results obtained from one of the gauge block electronic comparators available on the market proved that the differences in the mean results are insignificant.

An atomic force microscope (AFM) head designed for nanometrology is accomplished in this study. It is the sensing component of the nano-measuring machine, a nanometrological instrument with a working range of 50 mm × 50 mm × 2 mm, as well as a part of the metrological system of the instrument. Three reference mirrors are mounted on the head and arranged without Abbe error. Relative displacement of the AFM head and the specimen is measured by interferometers and results are traceable. The optical beam deflection method is used to detect the atomic force. The laser beam is introduced through a single-mode polarization-maintaining optical fibre from an external laser diode. With a compact design, a 100 mm optical lever is realized inside the AFM head that is less than 20 mm in thickness and 200 g in weight. A force–distance curve is obtained using a gauge block in a test. Furthermore, online tests of the measurement of a step scale have been made. According to the calculation and experimental verification, the resolution of our AFM head reaches 0.05 nm.

In this paper, we report a gauge block (GB) calibration that is traceable to the SI unit of time, the second. Four ultra-stable optical telecommunication wavelengths near 1556 nm are obtained by locking a narrow-tuning-range fiber laser to a fiber-based femtosecond frequency comb. Since the GB calibration system does not operate at this region of spectrum, the superior frequency stability of the laser is transferred to the 778 nm region by using a waveguide periodically poled lithium niobate crystal. After applying the locking scheme, the stability and accuracy of the laser become better than 8×10(-12). The frequency-doubled light is sent through 30 m optical fiber to a GB interferometer, which is installed at a different laboratory in the same building. Using this calibration scheme, a GB with a nominal length of 100 mm is calibrated with an uncertainty of ±52 nm. This uncertainty value is still comparable to or even better than other metrology laboratories for a similar block length.

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.

A new interferometric measurement system for gauge blocks which does not require wringing onto an auxiliary platen has been developed. The main characteristics of gauge blocks measured in this system are dimensions, coefficients of thermal expansion (CTE) and temporal stability. The repeatability is better than 3 nm for dimensional measurements and a comparison of this system to a conventional one showed good agreement. In CTE measurements, the expanded uncertainty is 3.5 × 10 −8 / K. Precision temporal stability measurement is improved since wringing is not required. This interferometer enables better quality control in our gauge block production process.

This investigation proposes a method, which is based on an external cavity diode laser (ECDL) and a double-ended interferometer, for directly measuring the thickness of opaque plane-parallel parts. The test part does not need to be wrung on a platen because a ring-like configuration enables the interferometer to view both surfaces of the part simultaneously. The optical path difference (OPD) of the interferometer is sequentially measured at a series of descending synthetic wavelengths to eliminate interference fringe order ambiguity. Every synthetic wavelength is a combination of a varied wavelength and the initial wavelength of the ECDL. The thickness of the part is finally determined following a succession of OPD calculations in terms of synthetic wavelengths and measured synthetic fractional fringes. The uncertainty in the measurement is gradually reduced as the measuring synthetic wavelength is progressively reduced. The results of performance testing indicate that the accuracy is about 0.5 μm for a 10 mm gauge block.

This paper describes improvements to a Hilger gauge block interferometer, including a fibre optic feed for a traceable laser radiation, use of a CCD camera for computer-controlled acquisition of fringe images and automatic analysis of the fringe image to obtain the fringe fraction. The gauge measuring process is now automated, computer-controlled, more accurate and significantly faster and easier to operate than the original design.

A new kind of high resolution, high accuracy comparator for dimensional measurements and its application for the measurement of the thickness of gauge blocks is presented. This comparator consists of two scanning tunnelling microscopes (STMs) whose tips probe the opposite sides of a sample. The STM tips are fixed on two high quality mirrors that are moved by piezoelectric actuators. The positions of the mirrors are measured by a high resolution laser interferometer, thereby coupling the length measurements to the unit of length. The detection of the sample's surface is performed by the STM probes and utilizes the high dependence of the tunnelling current on the tip-to-sample distance, which follows an exponential function and reaches about 1 nA at a tip-to-sample distance of less than 1 nm. This technique allows one to determine the position of the surface with a higher degree of accuracy than is possible using mechanical or optical probes. The determination of a distance consists of two consecutive displacement measurements by laser interferometer without and with the sample between the two tunnelling tips. The difference of these measurements corresponds to the object's length once environmental conditions such as temperature and refractivity are taken into account. In this paper we describe the construction and alignment of the instrument, the optimization of various components and experimental investigations of some parts of the measuring process, show first experimental results of the complete comparator obtained on thin gauge blocks and discuss the uncertainty budget.

A compact I2-stabilized frequency-doubled Nd:YAG laser has been developed for a long gauge block interferometer. The laser frequency stabilization is realized by the third-harmonic technique, where a fast frequency modulation (20 kHz) is applied to the piezoelectric transducer attached on the laser crystal. The relative uncertainty of the laser frequency has reached 3.6×10-12 for a 0.01-s averaging time. It is theoretically indicated that the phase error in the interferometric measurement due to the optical frequency modulation is sufficiently small to measure the long gauge block up to 1000 mm. Long gauge block measurement up to 1000 mm was successfully demonstrated with the developed I2-stabilized frequency-doubled Nd:YAG laser.

This paper presents a method for active angular alignment of gauge block 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.