The quality of an image formed by an optical system is determined by its modulation transfer factors at different spatial frequencies. In order to ensure uniformity in the measurement of modulation transfer factors and to create a standards base for the reproduction, maintenance, and dissemination of the corresponding unit, GET 205-2013 State primary standard for the optical power of spectacle lenses was improved in terms of realizing the unit of the modulation transfer factor within the wavelength range of 450–1550 nm. The composition, operating principle, and main metrological characteristics of GET 205-2025 State Primary Standard for the optical power and modulation transfer function of spectacle lenses and objectives are presented. GET 205-2025 comprises a setup for measuring the modulation transfer factors of optical systems and a set of standard objectives. GET 205-2025 ensures uniformity in measuring the modulation transfer factors of optical systems within the discrete spectral range of 450–1550 nm and provides a means to transfer the corresponding unit to working standards (measures of modulation transfer factors in the form of lenses) by means of a comparator, i.e., via the comparison method. From the working standards, the modulation transfer factor is transferred via the direct measurement method to appropriate measuring instruments: devices and systems for measuring modulation transfer factors, optical benches, and test stations for optical systems.

Приведена схема дифференциального фазового поляриметра, применяемого для исследования оптически активных веществ. Для анализа влияния ошибки юстировки вращающегося анализатора на результаты измерений угла вращения плоскости поляризации (УВПП) применено математическое моделирование процесса формирования информативного сигнала при наличии отклонения от перпендикулярности плоскости анализатора относительно оси распространения излучения. Приведены результаты исследования влияния ошибки юстировки на точность восстановления разности фаз двух гармонических сигналов. Полученные результаты позволяют выработать требования к юстировке элементов дифференциального фазового поляриметра с целью повышения точности измерений УВПП. The purpose of this work is to improve the accuracy of measurements of the optical rotation angle (ORA) by analyzing the effect of the adjustment error of the differential phase polarimeter analyzer. The paper presents a scheme of a differential phase polarimeter used for the study of optically active substances. To analyze the effect of the alignment error of the rotating analyzer on the ORA measurements results, mathematical modeling of the process of forming an informative signal in the presence of a deviation from the perpendicular plane of the analyzer relative to the axis of radiation propagation is applied. The results of the study of the influence of the adjustment error on the accuracy of restoring the phase difference of two harmonic signals are presented. The results obtained make it possible to develop requirements for the adjustment of the elements of the differential phase polarimeter to increase the accuracy of the ORA measurements.

We present a dynamic goniometer-spectrometer for measuring the refractive index (RI) of transparent triangular prisms by converting the beam deviation angles into time intervals. The proposed measuring scheme allows the automatic determination of the RI simultaneously for several different wavelengths by measuring the time intervals between the moments of autocollimation of the reference and refracted rays reflected from a mirror continuously rotating around the object with constant angular speed. This makes it possible to avoid the use of an expensive ring laser or encoder for angle measurements and to use relatively inexpensive instruments for time measurements, which reduces the cost of measuring equipment. To calculate the RI value, we used the minimum deviation technique. A functional diagram of the measuring equipment is given. A reference prism made of NBK-7 Schott optical glass was experimentally studied and the measurement errors were estimated. The proposed measuring scheme can be used for automated RI measurement and to study the dispersion characteristics of triangular prisms made of optically transparent materials and liquid optically transparent substances filling a hollow triangular prism.

Dispersion characteristics of optical glass are considered. An approach to research of dispersion characteristics of optical glass is proposed, requiring the measurement of the refractive index at only three wavelengths, which simplifies the measurement process compared with the use of the widely used Sellmeier equation. An approximation function for the refractive index of optical glass is proposed, the approximation error for various glass grades is calculated, and a method for correcting the approximation error is proposed. The refractive index measurements of optical glass samples are carried out at 3 wavelengths of He-Ne and Ar-Cr lasers, and values of the refractive index for spectral lines necessary for determining the dispersion characteristics are calculated. The value of the error in calculating the refractive index does not exceed ±1×10-5, which proves the prospect of using the proposed approximating function for studying the dispersion characteristics of optical glass.

This paper considers the features of polarimetric methods used for the analysis of optically active substances. It presents a design of a differential spectropolarimeter operating by analyzing the phase difference between two harmonical signals received when splitting a laser beam from a common source into separate reference and object beams. The expediency of using the Fourier transform to calculate the phase difference of differential spectropolarimeter signals is noted. The results of calculating the parameters of the measuring method and the results of an experimental study of reference polarimetric plates at various wavelengths are presented. The error in measuring the optical rotation angle in the wavelength range 405-780 nm did not exceed +/- 0.005 degrees.

In many areas of science and technology, there is a task to measure the optical and geometric characteristics of thin fi lms. The need to ensure the uniformity of measurements in this area led to the creation of the State primary standard of complex refractive index units GET 203-2012. In it, the complex refractive index was measured using spectral ellipsometry by measuring ellipsometric angles. However, this standard did not provide metrological support for coating thickness measurements when measuring their complex refractive index. In the period 2020–2023, VNIIOFI GET 203-2012 improved and expanded its functionality in terms of reproducing the unit of length in the fi eld of thickness measurements of optical coatings. The improved standard has been approved as the State primary special standard for units of complex refractive index and units of length in the fi eld of thickness measurements of optical coatings GET 203-2024. GET 203-2024 ensures the unity of measurements of complex refractive index and units of length in the fi eld of optical thickness measurements in the range from 1 nm to 50 μm. The range expansion was achieved by introducing an ellipsometer with an infrared range wavelength range equipped with an FTIR Fourier spectrometer. This range expansion is important for such industries as optics, microelectronics, optoelectronics, integrated optics and other areas of science and technology. This article presents the composition, operating principle and main metrological characteristics of GET 203-2024.

We present a new autocollimation method for measuring the refractive index (RI) of transparent triangular prisms. The classical autocollimation method is simple, but due to total internal reflection it is suitable only for prisms with small angles, which limits the accuracy of RI measurements. The proposed new method makes possible the autocollimation measurements of the RI for prisms with large angles designed to implement the minimum deviation method. A comparative accuracy analysis of the proposed and classical goniometric methods of RI measurements is carried out. A reference prisms set made of Schott optical glass was studied and the measurement errors were estimated. The calculated absolute error does not exceed +/- 1 10-5, which proves the prospect of using the presented method for high-precision RI measurements. The autocollimation method can be used for RI measurements and to study the dispersion characteristics of triangular prisms made of optically transparent materials and liquid optically transparent substances filling a hollow triangular prism.

The issues of metrological support of the instruments for measuring a two-dimensional spatial distribution (profile) of a unit of refractive index for solids are considered. A reference system has been developed, which is included into the State Primary Refractive Index Standard (GET 138-2021). The composition, principle of operation, and main metrological characteristics of the reference system, based on a digital interferometer for measuring a two-dimensional spatial distribution (profile) of the refractive index for thin sections of the preforms of graded-index glass fibers, are presented. The reference system according to GET 138-2021 provides the uniformity of measurements for the instruments used to measure the refractive index profile-so-called optical analyzers of preforms of the graded-index and optical glass fibers. The results of experimental studies of GET 138-2021 in terms of reproducing a two-dimensional spatial distribution of the refractive index unit are presented.

Methods for measuring the refractive index of optically transparent dielectric materials are considered. Modified methods based on the methods of minimum deviation and constant deviation are proposed and allow determining the refractive index of triangular prisms with unknown apex angles. In the proposed methods, the angles of light deviation on three faces of the prism are measured, and the refractive index of the material and the prism angles are determined from the solution of a system of equations. To implement the proposed methods, a goniometric system is used. That system was designed to measure angles between the flat surfaces of objects in manual and automated modes. Reference prism samples made of N-SF 1 optical glass, and a hollow prism filled with distilled water are studied. The proposed methods are compared and the measurement error is estimated. It is shown that the modified methods can be used for high-precision measurements of the refractive index in cases where the angles of the prism are unknown, or their measurement is associated with technical difficulties.

The paper proposes a modified method for measuring the refractive index of a triangular prism using an autocollimation angle measuring system designed to measure angles formed by flat surfaces of objects. The method involves using a fixed mirror to reflect the refracted beam, measurement of the angles of incidence of the beam on the face of the prism corresponding to the autocollimation positions and calculating the refractive index of the prism material using the solution of a system of equations. The paper presents the experimental study results for a triangular prism made of K8 optical glass using the proposed method, and a comparison of the results with the readings obtained using the State Primary Standard of the Refractive Index Unit GET 138-2021. The proposed method makes it possible to simplify the process of measuring the refractive index since there is no need to measure the angle of deviation of the beam.

Goniometric methods of measuring the refractive index of optically transparent materials based on the refraction of light by a triangular prism are studied. A modified minimum deviation method and 3 modified constant deviation methods are examined which make it possible to determine the refractive indices of triangular prisms with unknown refracting angles. According to the modified prism methods the deflection angles of the light by the prism are measured with a goniometer, while the refractive index of the material and the refraction angles of the prism are determined by solving systems of equations. Thus, there is no need for preliminary measurement of the prism angles, which would require special autocollimation goniometers. In addition, in the modified prism methods, light reflected from the faces of the prism is not used, which makes it possible to extend the spectral range of a measurement of the refractive index to the infrared and ultraviolet ranges. The errors in measurements of the refractive index by these methods are compared for the example of a prism with a refractive index of 1.5 and a refraction angle of 60°. It is shown that the modified minimum deviation method has the smallest error among all the prism methods, so it can be recommended for high-precision measurements of the refractive index in those cases where the refractive angles of the prism are unknown or it is technically difficult to measure them. The modified methods examined here can be used for measuring the refractive index of triangular prisms made of optically transparent materials, as well as of liquids poured into hollow prisms with plane-parallel transparent windows. Practical implementation of methods of this type should be useful in the optical, chemical, and food industries for monitoring the composition and properties of optically transparent materials.

In this article, goniometric methods for measuring the refractive index of optically transparent materials are discussed, and a modified method for measuring the refractive index of triangular prisms is proposed. A modified constant deviation method for measuring the refractive index was proposed in the previous study [1] that did not require refractive angle measurement of the prism and simplified the measurement process; however, its implementation required low-intensity radiation reflected from the input face of the prism, which created difficulties in processing signals from a photoelectric receiver and can increase measurement error. In this study, this problem was eliminated with the usage of two fixed mirrors to obtain the reflection of the refracted beam and determine the initial position of the prism, and the refractive index of the prism material was calculated from the solution of a system of equations. This approach avoids the use of radiation reflected from the prism faces, which helped in increasing the accuracy by automating the measurement process. Herein, the results of an experimental study of a triangular prism made of optical glass using the proposed modified prism method are compared with the values obtained using the least deviation method, which has the highest accuracy in determining the refractive index. The proposed method can be used to study triangular prisms made of optically transparent materials as well as optically transparent liquids poured in a hollow triangular prism.

The purpose of this work is to analyze the effect of the polarimeter signal processing algorithm on the results of measurements of the optical rotation angle of the polarization plane to improve the accuracy of measurements in differential polarimetry. Methods. The paper considers the methods of polarimetry used for the analysis of optically active substances, based on the methods of phase measurements used to calculate the optical rotation angle. The expediency of using the Fourier transform to calculate the phase difference of differential polarimeter signals is noted. To analyze the error of the algorithm, mathematical modeling of the measurement information processing for various signal parameters is applied. Results. The results of the study of the effect of the bit depth of the analog-to-digital converter, the number of samples over the period of the signal and the accumulation time on the accuracy of restoring the phase difference are presented. The influence of the ratio of signal amplitudes and the level of amplitude and phase noise caused by the imperfection of the measuring system has also been investigated. Conclusion. The obtained results make it possible to optimize the operating mode and improve the accuracy of the optical rotation angle measurements using a differential phase polarimeter based on the Fourier transform.

Goniometric methods of measuring the refractive index of optically transparent materials based on the refraction of light by a triangular prism are considered. Modified method of the minimum deviation and 3 modified constant deviation methods are considered, which allows determining the refractive index of triangular prisms with unknown apex angles. According to modified methods, the angles of light deviation by a prism are measured with goniometer, and the refractive index of the material and the prism angles are determined from solving the systems of equations. Thus, there is no need for preliminary measurement of the prism angles, which requires the use of special autocollimation goniometers. In addition, the modified methods do not use radiation reflected from the faces of the prism, which makes it possible to extend the spectral range of measurement of the refractive index to the infrared and ultraviolet regions. A comparative accuracy analysis of the considered methods for a prism with a refractive index of 1.5 and an angle of 60° as example is carried out. It is shown that the modified methods can be used for high-precision measurements of the refractive index in cases if the apex angles of the prism are unknown or their measurement is associated with technical difficulties. The considered methods can be used to measure the refractive index of triangular prisms made of optically transparent materials, as well as liquids poured into hollow prisms with plane-parallel transparent windows. The practical implementation of such a methods can be useful in the optical, chemical and food industries to control the composition and properties of optically transparent substances.

Test objects of various types are utilized in the creation and utilization of video measuring systems that are part of robots' technical vision, television sight units, triangulation measuring systems, as well as 3D scanners. Simultaneously, a specific test object was created for each type of device. This paper examines the possibility of creating and constructing universal test objects for calibration (verification) of 2D and 3D video measuring systems that are used to measure the geometric parameters of two-dimensional (2D) and three-dimensional (3D) objects, respectively. We suggest using a liquid crystal monitor-based test object (measure) to calibrate 2D systems. This measure is calibrated using a high-precision laser interferometer displacement measurement device and subpixel image resolution algorithms. The developed measure corresponds to the standard of the 3rd category according to the State verification scheme for measuring instruments of length in the range of 1∙10−9–100 m and wavelengths in the range of 0.2–50 μm. This measure can be used to determine the modulation transfer function of a video system and the point spread function. To calibrate (verify) 3D systems, a gage block stack that can move in space according to a given program using a translator and an external linear encoder is proposed. We present the technical specifications of the developed measures that can be used as working standards for the calibration (verification) of a wide variety of video measuring systems.

We present a method for measuring the refractive index (RI) and spectral characteristics of transparent triangular prisms based on the minimum deviation technique. The proposed method has been developed to automatically measure RI simultaneously for three different wavelengths to determine the spectral dependence of RI. A high precision dynamic goniometer with a He-Ne ring laser and continuously rotating autocollimation mirror was used to implement the proposed method. A set of reference prisms made of optical glass were experimentally studied and the measurement uncertainty budget was estimated. The obtained values of the expanded measurement uncertainty did not exceed 4.6 × 10 −6 for near-infrared and 1.2 × 10 −5 for visible wavelength ranges with a coverage factor k = 2 (95% level of confidence). It is shown that this method can be used for high-precision measurements of the RI and determine the spectral characteristics.

Subject of study. A method for the measurement of the refractive index using an automated autocollimating gonio-metric system is proposed. Aim of study. The study facilitates the precise measurement of the refractive indices of transparent solid and liquid optical materials. Method. Goniometric methods based on the measurement of angles of light refraction caused by a substance are often used to measure the refractive indices of trihedral prisms. A method to determine the refractive index via measuring the light deviation angle caused by a prism after reflection from the internal facet in the automated mode is proposed. Main results. The refractive indices of two trihedral prisms composed of different glass types, namely, N-BK7 and SF-1, measured using the proposed method and autocollimating goniometric system are presented. The measurement error did not exceed 1.5 x 10-4 when com-pared with the nominal value for these prisms at the wavelength of the radiation source of the autocollimator, thus confirming the prospect of application of this method in high-precision refractive index measurements. Practical significance. The method proposed in this study can be used to measure the refractive indices of trihedral prisms made of optically transparent materials with different apex angles using the goniometric system in an automated mode. The method can also be applied to optically transparent liquid materials located in a hollow trihedral prism.

The paper presents a new original technique for accurate reconstructing the wave front phase at interferometry measurements based upon the estimation of the signals’ amplitudes. The optical signals’ processing is implemented within the Rice statistical model. The required phase of the wave front to be reconstructed is calculated from the geometrical considerations from the calculated undistorted amplitudes values. The paper provides both the mathematical basics of the technique and the results of its testing by means of both numerical and physical experiments. The proposed technique can be efficiently applied in a wide circle of scientific and technical tasks in numerous ranging and communication systems.

Methods for measuring the salinity of sea water are considered. The results of an experimental study of samples of common and sea salt solutions with different salinity poured into a hollow trihedral optical glass prism are presented. The light refraction angles are measured with a goniometric system by use of which the minimum deviation method possessing a high accuracy of determining the refractive index is implemented. Using dispersion analysis of experimental results, it is proved that the refractive index of water does not depend on its salt composition. An equation describing the dependence of the refractive index on salinity and temperature for a fixed wavelength is proposed.