Igor Malinovsky

Fringe-image processing gauge block comparator of high precision

Interferometric image-analyzing comparator for gauge blocks of 1-100 mm length is reported. Sophisticated image processing software, that supports 0.1 nm resolution in central length and 1 nm in 3D surface measurements, has been developed. Resolution of the comparator reaches the value of 1 X 10-9 for 100 mm blocks. Inclination error is reduced to the value of 8 X 10-9. The relative uncertainty for inclination correction can be statistically diminished to about 2 X 10-9. The instrument and a new method have been used to study the deformations of steel plates, caused by wringing forces. In these experiments, 3D surface profiles of plates and blocks are being recorded while gradually diminishing the wringing forces by the oil, that slowly penetrates into the wringing contact. Shorter blocks are shown to be significantly deformed by the steel plate, while the deformations of the plate are quite negligible. This allows to realize reproducible wringing, and to perform precise correction on interferometer optics and curvature of the base plate. Blocks longer than 25 mm are shown not to be deformed, practically, by the plate.

Determination of saturation parameter in iodine and precise molecular linewidth measurements in He-Ne/I2 standard at 633 nm

Abstract A new method for linewidth studies in a primary wavelength standard is proposed, resulting in the determination of a saturation parameter in iodine, the physical quantity that defines the amplitude and the power broadening of the inverted Lamb dip in the absorption medium. Precise linewidth information is obtained by comparison of the experimental beat-frequency data of the laser locked to the zero crossings of the discriminant curve, with the results of calculations that use the high-power gas laser theory with Gaussian intensity distribution beam profile. The method is based on the variation principle, the saturation parameter value being found by the computer fit, which gives a constant value of the homogeneous linewidth of iodine for several laser modulation width values. The saturation parameter in iodine has been determined for the first time. Its dependence on iodine pressure is found to be parabolic. The relation between the saturation parameter and the laser output power is presented, giving the possibility to calculate the saturation parameter of an auxiliary He-Ne/I 2 laser at 633 nm.

Nanometrology and high-precision temperature measurements under the temperature conditions varying in time temperature conditions

Significant progress in high-precision temperature measurements of material artifacts has been achieved as a result of a development of a new approach which takes explicitly into account the effect of a heat waves propagation in a sample. The approach requires a complete change of a routine procedure in temperature measurements. In order to detect the time delay in a heat wave propagation, it is necessary to have two detectors which synchronously measure the temperatures and temperature rates in two different points of a sample. When these four parameters are recorded for a number of slow heating and cooling procedures, the measurement results can be corrected on the velocity error, which is associated with the time delay in the wave propagation between the two measurement points on a sample. As an intermediate result in the new method, we obtain the value of the thermal field variation (temperature gradient) between the two points of the artifact. We also use a special type of synchronous detection, with a complete averaging within a half-cycle of a modulation procedure, in order to measure precisely a self-heating effect of a resistance thermometer, which is attached to the artifact surface. This results in a reduction of the uncertainty of measurements to a few μK level.

Precise interferometric length and phase-change measurement of gauge blocks based on reproducible wringing.

A modern fringe-pattern-analyzing interferometer with a resolution of 1 x 10(-9) and without exclusion of systematic uncertainties owing to optic effects of less than 1 nm was used to test a new method of interferometric length measurement based on a combination of the reproducible wringing and slave-block techniques. Measurements without excessive wringing film error are demonstrated for blocks with nominal lengths of 2-6 mm and with high surface flatness. The uncertainty achieved for these blocks is less than 1 nm. Deformations of steel gauge blocks and reference platens, caused by wringing forces, are investigated, and the necessary conditions for reproducible wringing are outlined. A subnanometer uncertainty level in phase-change-correction measurements has been achieved for gauge blocks as long as 100 mm. Limitations on the accuracy standard method of interferometric length measurements and shortcomings of the present definition of the length of the material artifact are emphasized.

Deformations of a gauging surface texture under wringing conditions

This paper deals with some basic problems of interferometric length measurements. Traditionally, all the deformations of a material artifacts, associated with the wringing procedure, were included into the length of a block, as there were no reliable ways to measure these deformations and to apply the corresponding corrections. Here, we present the first measurements of the surface texture deformations, arising in the wringing contact between the two gauging surfaces of similar materials and surface finish. The deformation value is obtained as a result of the measurements of the peak-to-peak length value of a free, unperturbed block and of the mechanical length of the block, which is obtained with the reproducible wiring technique and the slave-block method. Basically new concept for the optical length metrology - the physical length of a free artifact has been introduced in to the measuring practice. The way for crucial improvement of the realization of the SI length unit in the corresponding range has been outlined.

Wringing deformation effects in basic length measurements by optical interferometry

The effect of wringing deformations on the result of the main types of measurements by optical interferometry is studied in some detail. The wringing bending deformations can be used to improve by 10-20 times the accuracy of length measurements of gauge blocks with nominal lengths of a few millimeters. The data on the surface deformations of steel and quartz reference plates, resulting from the writing procedure of gauge blocks to their surface, are presented. Ways of crucial reduction of the plate surface deformations are reported. Surface texture deformations, arising in the tight wringing contact, are measured to be about 2.5-3 nm for modern steel and tungsten carbide blocks. Thanks to extremely high level of their reproducibility, the surface texture deformations, practically, do not affect the accuracy of the mechanical length measurements of gauge blocks.

Interferometric length and roughness measurements with nanometer accuracy level

Gauge blocks are known to be the most important and commonly used material standards in maintaining traceability in dimensional metrology. They are regularly used in international comparisons of interferometric measurements to assess the accuracy of the length SI-unit, reproduced in different countries, as with the help of interferometric comparators the length of the block can be directly determined in terms of vacuiini wavelengths of standard radiations [1]. In many countries the primary level comparators are similar to the big KOsters interferometer [2-3], where a plane light wave of big aperture is propagating in vacuum and after reflection from a plane mirror forms a standing wave, with a precisely known separation between the points of equal intensity (fringes). This standing wave is then used to find the length of a gauge block in terms of the vacuum wavelength, which is calculated as the ratio of the speed of light (explicitly fixed in the present definition of the Metre) and the laser frequency, known from the absolute frequency measurements performed against the primary Cs standard. The procedure of length measurement in this instrument requires a flat reference plate to be wrung to one of the faces of the gauge block. For short gauge blocks, of a few mm nominal lengths, the largest uncertainties in the accuracy budget of the interferometric measurement [4] arises due to the phase change correction [2] (±12 nm at 95% confidence level [4]) and due to the variability of the wringing film thickness (±12 nm at 95% confidence level [4]). In some papers [3,5], for selected blocks with smaller deviations in flatness, the variability of the wringing film thickness is reported to be about nm (at 95% confidence level). In this paper, we describe a new approach in the interferometric length measurements that is based on the technique of the reproducible wringing [6-9]. It gives the opportunity to measure the physical length of the material artifact without the excessive wringing film thickness and results in the accuracy of the phase change measurements at the optical reflection from surface of the material standard of better than I nm.

Realizing subnanometer accuracy level in gauge block measurements

A new fringe-pattern analyzing interferometer, featuring ultimate resolution of a few parts in 109, stability of readings of about 0.1 nm and non-excluded systematic uncertainties due to optic effects of less than 1 nm, has been study some systematic effects in gauge block length measurements. Measurements on steep and quartz plates are analyzed. Limitations of the present definition of the length of the block are outlined. Stability and reproducibility of the wringing procedure for steel and quartz plates are reported. A new double-ended method in length measurements of gauge blocks has been realized. It includes determination of the corrections for non-ideal optics of the interferometer, curvature of the pate and deformations of the quartz plate due to wringing of the block to its surface. The result of the length measurement is not affected, in the first approximation, by deformation of the pate and the quality of wringing.

Asymmetry studies of iodine resonances and realization of unperturbed molecular transition in a laser standard at 633 nm

Abstract A detailed study of the asymmetry of saturated absorption resonances in a laser wavelength standard operating at 633 nm is presented. Analysis of the results for the third and fifth harmonic frequency stabilization techniques has been performed. A new approach in the studies has made it possible to handle the problem of correlated pressure, modulation width and power shifts in the laser standard. As a result, the laser frequency shift due to the resonance asymmetry has been separated from the iodine pressure (inelastic collision) shift. The frequency shift associated with the resonance asymmetry has been shown to increase nonlinearly (quadratically) with the iodine pressure. Collisions with small angle of scattering are found to be the main reason for this effect. The unperturbed molecular transition frequency for the i-component of iodine has been found to be 473 612 214 858.5 ± 12.7 kHz. The validity of the method is confirmed by frequency measurements performed with a special standard, featuring ten times smaller line asymmetry than that of a conventional laser standard.

Precise certification of the temperature measuring system of the original Koesters interferometer and ways of its improvement

Large Koesters interferometer for long gauge block measurements is known as a unique instrument, which for many decades is being used for the realization of the SI length unit with extremely low uncertainty values. High-precision certification of the temperature measuring system of the original Koesters interferometer has been realized, when using two alternative systems, operating simultaneously. The uncertainty level of each of the reference system is well below 1 mK. Our systems are based on platinum resistance thermometers (PRTs), calibrated directly on a gauge block with the application of the correction on velocity error. Advantages and some drawbacks of the original system are outlined. We show that in the original Koesters interferometer of INMETRO, as a result of systematic thermocouple offsets, which are specific for each particular thermocouple and the way how it is located inside the instrument, the accuracy of the system is limited to about 2 mK. The basic result of this study is that the chamber of the interferometer permits to improve gauge block temperature measurements, when the fine effects, associated with a small overheating of the gauge block surface by the measurement current of resistance thermometer, can be detected. Those effects are energy dissipation of a heat wave during its propagation in the artifact and the velocity effect in self-heating measurements. Local overheating of long gauge blocks by PRT current, which lies in range of ~0.1 mK, is found to be one of the limiting factors in precise temperature measurements of the blocks.