Recovering physical fields with a two-dimensional fiber-optics measurement grid

A tomographic fiber-optics grid can be used to record two-dimensional field patterns. The structure of the grid is described, and a processing algorithm has been tested, which reduces the number of fiber lines required by a factor of 4. An experimental model has been tested successfully in the recovery of the two-dimensional transverse vibration pattern at the surface of a ship's fuel tank. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 24–30, March, 1999.     

Recovering the input signals to a means of measurement described by linear differential equations with constant coefficients

Translated from Izmeritel'naya Tekhnika, No. 2, pp. 12–13, February, 1990.     

Three-dimensional mapping and range measurement by means of projected speckle patterns

We present a novel approach for three-dimensional (3D) measurements that includes the projection of coherent light through ground glass. Such a projection generates random speckle patterns on the object or on the camera, depending if the configuration is transmissive or reflective. In both cases the spatially random patterns are seen by the sensor. Different spatially random patterns are generated at different planes. The patterns are highly random and not correlated. This low correlation between different patterns is used for both 3D mapping of objects and range finding.     

Three-dimensional magnetic field measurement of a modifiedthin-film magnetic head for vertical recording by means ofLorentz-tomography

The method of Lorentz tomography with an electron beam as a microprobe, combined with an analytical reconstruction procedure, has been successfully adapted to thin-film heads for vertical recording. It is noted that the measured results can be used as a basis for adjusting the magnetic parameters of the thin-film head to achieve good agreement with corresponding FEM or BEM (finite element or boundary element method) calculations. It is concluded that Lorentz tomography can be used as an important tool in the design of thin-film magnetic heads     

Characterization of two-dimensional finite-aperture wire grid polarizers by a spectral-domain technique

We investigate the transmission characteristics of perfectly conducting two-dimensional wire grid polarizers fabricated in finite and infinite apertures using a rigorous spectral-domain mode-matching method. Specifically, the transmission coefficient for both transverse-electric and transverse-magnetic polarizations, extinction ratio, and diffraction pattern are characterized for a wide variety of geometric and material parameters including aperture dimension, conducting wire fill factor, wire spacing, polarizer thickness, material dielectric constants, and incident wave arrival angle. The results indicate that the transmission behavior is largely insensitive to aperture dimension.     

Characterization of piezoceramic rectangular parallelepipeds by means of a two-dimensional model

The characterization of piezoelectric resonators is a field of intense scientific work; moreover, clear and accepted IEEE and IEC Standards have been published, showing the concepts and routes to perform the complete characterization of piezoelectric resonators. All of the accepted procedures define some resonator geometries, each of them related with a set of parameters, that can be obtained following resonance measurements at the corresponding resonance frequencies. The basis of the standards is the existence, for each geometry, of well-defined modes that have been analytically solved. The development of multi-dimensional models of the waves' propagation in piezoceramic materials opens the possibility of characterizing piezoelectric resonators with geometries different from those recommended in the standards. In this paper, a two-dimensional model, which takes into account the mechanical and dielectric losses, has been used to characterize piezoceramics with the shape of a regular parallelepiped. A set of elastic, dielectric, and piezoelectric parameters, which are useful for piezoelectric transducer design, can be obtained. For a given sample, the measured input electrical impedance is used to obtain the parameters by means of a fitting process with the corresponding model output. The results obtained with low and high loss materials show that the parameters found have values similar to those obtained following the procedures and geometries recommended by the standards. This procedure permits the characterization of materials when the manufacturing procedure does not allow the fabrication of the shapes recommended by the standards, making it a useful tool for transducer manufacturers and material scientists     

Step-height measurement by means of a dual-frequency interferometric confocal microscope

A novel instrument, the dual-frequency interferometric confocal microscope (DICM), which facilitates the measurement of step features, is investigated. It combines the advantages of the high resolution (subnanometer) of heterodyne interferometry and the relatively large measurement range (approximately 5 microm) of confocal microscopy. The axial response curves of the confocal microscopy system are compared in experiments in which microscopic objects with various numerical apertures and magnifications are used. The results prove that the variation in light intensity is enough to permit discrimination of different orders of interference fringes. The DICM has been successfully utilized to measure the step height of a standard mask, and the experimental results agree well with those measured by scanning probe microscopes. The results also show that the system has good repeatability, with a maximum deviation of 5 nm.     

The design of two-dimensional photonic quasicrystals by means of a fourier transform method

Abstract

We report a method of designing aperiodic photonic quasicrystals. The method is based on the recognition that the Fourier transform of the dielectric structure has a direct influence on the mode spectrum, and can be chosen to enhance the properties of the system. The diffraction of light by, and the band structure of, such modified photonic quasicrystals is investigated and compared to the properties of conventional photonic quasicrystals.     

Determining alignment in measurement of a large-diameter thread by means of devices for profile measurement

An analytic estimation of the inaccuracy of the alignment of a thread gauge on a device that must be taken into account in the measurement of the accumulated error of the thread pitch is given. For an M170.6 thread, the measurement error of the accumulated pitch reaches 0.008 mm on a length of 200 mm. Translated from Izmeritel’naya Tekhnika, No. 12, pp. 13–16, December, 2008. An erratum to this article can be found at     

Determining alignment in measurement of a large-diameter thread by means of devices for profile measurement

Measurement Techniques -     

Resolution limit for two-dimensional crossed-grating patterns projected by a coherent beam

The resolution limit for two-dimensional crossed-grating patterns created by projecting mask objects by using a coherent beam has been investigated. We consider first two conventional mask types, a binary-amplitude mask and a two-level phase-shifting mask, in analyzing relationships between a diffraction-beam configuration and an image-intensity distribution. Then we derive, as a mask that overcomes the resolution limit of the conventional ones, a four-level phase-shifting structure with which the minimum image period can be reduced to square root(2)/2 time that of the two-level phase-shifting mask.     

Ultrasonic vector velocity measurement by projection ComputedVelocimetry

A new method of measuring complete vector components of target velocity is proposed. This method makes it possible to measure target velocity components both along and transverse to the beam axis in two steps. The first step is Fourier transformation of the received signals in the direction of the time-axis (the ultrasonic pulse emission number). The second step is projection integration in the polar-axis direction. These two steps provide the two velocity components along and transverse to the beam axis. The new method is similar to the Computed Velocimetry method (CV) proposed previously by the authors, except that it does not require Fourier transformation in the polar-axis direction. The theory for this method and results of numerical simulation are presented