Use Of Interferometry Research Articles

Implementation of Radon transformation by rotating 1D interferometer

The use of interferometry to observe objects in three-dimensional space requires a corresponding rank of the system of interferometric base vectors. The paper considers one of the ways to solve such a problem using the rotation of a 1D interferometer at an angle to the rotation axis This, with the exception of special cases of parallelism or perpendicularity of the axes, makes it possible to form a consecutive 3D interferometer. Using the rotation of the Earth, such an interferometer performs Radon transform of the angular structure of the spatial image when observing sources far beyond the size of the interferometer base. For this, the elements of the interferometer should be placed at different latitudes. The obtained analytical expressions show that the two-dimensional representation of one-dimensional projections as a function of the rotation angle then takes the form of a sinogram. A rotating 1D interferometer can be used in a number of fields of science and technology, for example, to solve location problems, in ultrasonic de¬fectoscopy, in technical vision systems, in radio astronomy, etc.

Retrace error calibration for interferometric measurements using an unknown optical system.

In classical interferometric null test measurements, the measurement and reference beam path should be the same. A difference in the beam paths results in the so called retrace error. One very common approach to avoid retrace errors is to adapt the measurement wavefront to the reference wavefront with a computer generated hologram (CGH), which is costly and time consuming. A much more flexible approach is to do non nulltest measurement in combination with mathematical treatment of retrace errors. Most of such methods are based on iterative optimization or calibration of the nominal optical design of the interferometer. While this may be a convenient solution in the context of research, the more common use may be limited due to the need of the optical design of all interferometer components. In many cases, the optical designs of standard off the shelf optical assemblies are not available or disclosed by the manufacturer. This is especially true for transmission spheres of interferometers. We introduce the so called Black Box Model (BBM), used in the well known Tilted Wave Interferometry (TWI), as a mathematical model to account for retrace errors in interferometry. The Black Box Model is based on point characteristic functions which are adapted to the result and behavior of a real interferometer by calibration. With an extended calibration method, the need of a specific optical design of the interferometer is no longer necessary. Thus the method is attractive for a wide field of use in interferometry with standard off the shelf components.

Phase Perturbation as a Measurement Metric: A Novel Noncontact In-Line Production Measurement Through an All-Electronic Millimeter-Wave System Tracking Millidegree Perturbations in Phase

The market value for the plastics manufacturing industry is projected to exceed USd700 billion in the coming decade [1]. Technology for reliable quality control is an essential component of the manufacturing process. Present technology for monitoring the thickness profile of manufactured plastics typically makes use of interferometry with a white-light (broadband or tunable-wavelength) laser source. [2]-[5]. While this method has found satisfactory implementation as a quality control mechanism to monitor deviations in the thickness of plastics, the cost and complexity of implementation can be prohibitive. In addition, laser-based time-of-flight terahertz time-domain spectroscopic (THz-TDS) tomography systems have been presented as a suitable alternative; however, a femtosecond pulsed laser is still required to render measurements on the order of a micron (mm) [6].

Interferometry of binary stars using polymer optical fibres

We show a laboratory experiment in which students can learn the use of interferometry as a valuable tool in astronomy. We detail experiments based on the use of the classic Michelson stellar interferometer able to reproduce the size of single stars and to characterize double star systems. Stellar sources, single and double, are reproduced by a laser light emerging from the circular end faces of one or two step-index polymer optical fibres. Light coming from the fibre end faces passes through two identical pinholes located on a lid covering the objective of a small telescope, thus producing interference fringes. The measurement of the fringe visibilities allows us to estimate both the diameters of the simulated stars and the separation between them, with errors lower than 18% for a range of light sources that can recreate the apparent size of the outer Solar System planets Uranus and Neptune and the binary properties of the Alpha Centauri system. The exercises here described illustrate the optical principles of spatial interferometry and can be integrated into courses on astronomy, optics or space science, with close interaction between theory and experiment.

Microscopic Studies of Calcium Sulfate Crystallization and Transformation at Aqueous–Organic Interfaces

The calcium sulfate crystal system is of considerable fundamental and practical interest, consisting of the three hydrates, gypsum (CaSO4·2H2O), bassanite (CaSO4·0.5H2O), and anhydrite (CaSO4). Each has significant applications; however, synthesis of anhydrite via conventional aqueous methods requires elevated temperatures and therefore high energy costs. Herein, we investigate calcium sulfate crystal growth across a nonmiscible aqueous–organic (hexane or dodecane) interface. This process is visualized via in situ optical microscopy, which produces high magnification videos of the crystal growth process. The use of interferometry, Raman spectroscopy, and X-ray diffraction allows the full range of calcium sulfate morphologies and hydrates to be analyzed subsequently in considerable detail. In the case of dodecane, gypsum is the final product, but the use of hexane in an open (evaporating) system results in anhydrite crystals, via gypsum, at room temperature. A dissolution–precipitation mechanism between ne...

Bistatic three-dimensional interferometric ISAR image reconstruction

A three-dimensional (3D) bistatic inverse synthetic aperture radar (ISAR) imaging method is proposed in this paper. The proposed method makes use of interferometry and technically speaking, produces a 3D target reconstruction by estimating a scattering center position in 3D Cartesian space. The proposed method makes use of a combined ISAR/interferometry technique that also allows the ISAR image plane to orientation to be estimated. Cross- or L-shaped antenna configurations are discussed, and the effects of the baseline length along the horizontal and vertical direction on the scatterer’s position estimation are analyzed in detail. Finally, numerical simulations are used to evaluate the proposed method’s performance.

Application of self-mixing interferometry for depth monitoring in the ablation of TiN coatings

Among possible monitoring techniques, self-mixing interferometry stands out as an appealing option for online ablation depth measurements. The method uses a simple laser diode, interference is detected inside the diode cavity and measured as the optical power fluctuation by the photodiode encased in the laser diode itself. This way, self-mixing interferometry combines the advantages of a high resolution point displacement measurement technique, with high compactness and easiness of operation. For a proper adaptation of self-mixing interferometry use in laser micromachining to monitor ablation depth, certain optical, electronical, and mechanical limitations need to be overcome. In laser surface texturing of thin ceramic coatings, the ablation depth control is critically important to avoid damage by substrate contamination. In this work, self-mixing interferometry was applied in the laser percussion drilling of TiN coatings. The ∼4 μm thick TiN coatings were drilled with a 1 ns green fiber laser, while the self-mixing monitoring was applied with a 785 nm laser diode. The limitations regarding the presence of process plasma are discussed. The design criteria for the monitoring device are explained. Finally, the self-mixing measurements were compared to a conventional optical measurement device. The concept was validated as the measurements were statistically the same.

Microscopic heterodyne interferometry for determination of electron density in high-pressure microplasma

Electron density is paramount for understanding plasma characteristics and for control in plasma applications. To determine the electron density in a plasma by the use of interferometry, the phase shift of a probing electromagnetic (EM) wave induced by interaction with the plasma is measured. In this paper, for the determination of electron density in microplasmas generated under conditions of fluid density higher than that of ambient air, we discuss appropriate wavelength ranges for the probing EM wave (laser beam) in interferometry with consideration of the plasma parameters in the tested plasma source. On the basis of the discussion, we develop an interferometry system using a near-infrared diode laser in combination with a reflection system and a microscope for microplasma diagnostics, and measure the electron density in a 200 ns short-pulse microdischarge generated in a 0.3 MPa helium supercritical fluid.

전자처리스페클패턴 간섭법을 이용한 평판 용접시험편의 잔류응력 측정

용접구조물에는 외력이 부가되기 이전에 잔류응력이 걸려 있으므로 용접잔류응력 크기 및 분포 상태는 취성파괴, 피로강도, 응력부식균열, 좌굴, 시효변형과 같은 다양한 형태의 손상에 직접적으로 영향을 끼쳐 잔류응력을 정량적으로 해석하기 위한 지속적인 연구가 필요한 실정이다. 본 논문은 비파괴적인 기법 중 레이저를 이용한 전자처리스페클패턴 간섭법을 이용하여 평판 용접시험편의 외부하중에 따른 전체 거동에 잔류응력의 측정 기법을 제시하고자 한다. 용접시험편에 인장 하중을 가하였을 때, 이를 전자처리패턴스페클 기법을 이용하여 측정하였다. 측정된 결과로부터 용접시험편의 모재부와 용접부의 변형률을 측정하고, 이를 이용하여 탄성계수를 측정하였다. 본 논문은 전자처리스페클패턴 간섭법으로 용접시험편의 용접부와 모재부의 변형률의 차이를 이용하여 잔류응력 값을 산출하는 식을 제시하였고, 이를 수치적으로 계산하여 잔류응력 값을 산출하였으며 측정 결과, 모재부에 비해 용접부의 탄성계수가 약 3.7배 높은 약 8.46 MPa로 측정되었다. The size and distribution of welding residual stress and welding deformation in welding structures have an effect on various sorts of damage like brittle failure, fatigue failure and stress corrosion cracking. So, research for this problem is necessary continuously. In this study, non-destructive technique using laser electronic speckle pattern interferometry, plate of welding specimen according to the external load on the entire behavior of residual stress are presented measurement techniques. Once, welding specimen force tensile loading, using electronic speckle pattern interferometry is measured. welding specimen of base metal and weld zone measure strain from measured result, this using measure elastic modulus. In this study, electronic speckle pattern interferometry use weld zone and base metal parts of the strain differences using were presented in residual stress calculated value, This residual stress value were calculated by numerical calculation. Consequently, weld zone of modulus high approximately 3.7 fold beside base metal and this measured approximately 8.46 MPa.

Experimental study of surfactant transfer in fluid systems in microgravity conditions

The paper presents the results of the space experiment studying the process of surfactant dissolution from a binary fluid drop in microgravity conditions. The experiment was performed during the flight of the space satellite “Foton M-3” in September 2007. Investigation of the surfactant diffusion was made using a new original setup based on the interferometric method. The experimental cuvette represented a thin Hele-Shaw cell filled with water, which surrounded a drop in the form of a short liquid cylinder with a free lateral surface. The drop consisted of a binary mixture, in which one of the components was the surfactant easily dissolved in water. The use of interferometry made it possible to visualize and investigate evolution of the surfactant distributions and the flow structures in the drop and the surrounding liquid. The characteristic stages of the dissolution process were identified, and the rate of the concentration front propagation was defined. It was shown that in microgravity conditions the process of surfactant diffusion through the interface did not initiate an intensive solutal Marangoni convection as contrasted to the case of terrestrial simulation. The observed phenomenon has its origins in the long-lived fields of surfactant concentration formed near the interface due to the absence of the gravitational mechanisms of motion and large characteristic time of admixture diffusion which is hundreds of times longer than the time of thermal diffusion.

Optimum entangled photon generated by micro-ring resonators for new-generation interferometry use

We first propose a concept of a new interferometric technique, where the ultra-narrow spectral width of light pulse generated by using the micro-ring resonators can be used to perform the ultra-high-resolution interferometer. Firstly, the SHG using micro-ring resonators is analyzed and described, Secondly, the increasing in optical path difference (OPD) depends on the full-width at half-maximum (FWHM) width of the generated pulse is discussed. Finally, the optimum entangled photon visibility can be formed the quantum interferometer where the measurement resolution of 10 −5–10 −7 in term of birefringence is achieved. The use of such systems for quantum interferometer, high-resolution interferometer and surface characterization are described.

Advances in thick and thin film analysis using interferometry

The use of interferometry to measure transparent and semi-transparent films is becoming more and more important as understanding of the measurement becomes more widespread. Techniques for measurement of thick films of 1 μm or greater using interferometry have been available for some time but measurement of thin films using interferometry is a much newer technique, also the effect of films coatings on interferometry measurements in general is now becoming more widely understood. The measurement of thick and thin films using interferometry is discussed in this paper.

Output-Noise Statistical Characterization for Digital-Phase-Demodulation Systems With Intensity-Based Input Noise

A large fraction of fiber-optic-sensor systems make use of interferometry in the measurement process, implying the need for demodulation to obtain the encoded signal of interest. Of great interest for sensor characterization is the performance of the demodulation scheme under the influence of noise. In this paper, we construct a very general transfer function that relates intensity-induced input noise to its phase noise realization in the output for a wide class of digital-demodulation techniques. We proceed to compute analytically a probability density function of this output noise and use this to compute low-order statistical moments of the output noise. We compare the analytical formulations with simulated data from a representative demodulation scheme used in a currently existing fiber Bragg grating (FBG) sensor system and find excellent agreement

Far-Infrared/Submillimeter Astronomical Interferometry with Spaceborne Tether Formations

Through the continuing development of improved detectors and detector arrays, far-infrared/submillimeter astronomical space missions have had enormous successes in recent years. Despite these advances, the diffraction-limited angular resolving power has remained virtually constant. The advent of telescopes with apertures of several meters will improve this capability, but will still leave image resolution many orders of magnitude poorer than in most other spectral ranges. Here we point out that the only foreseeable way to improve image quality to rival that of modern optical telescopes will be with interferometers whose light collectors are connected by tethers. After making the scientific case for high spatial resolution far-infrared/submillimeter imaging and the use of interferometry as the most immediate way of producing results, we discuss recent advances in dynamic analysis and control of tethered formations, and argue that the further development and testing of tethers in space is a first step toward providing improved far-infrared/submillimeter angular resolution and astronomical image quality.

Comparison of Polyethylene Wear Associated with Cobalt-Chromium and Zirconia Heads After Total Hip Replacement<sbt aid="1024890">A Prospective, Randomized Study</sbt>

A ceramic femoral head is an alternative to a metal femoral head for the bearing surface of total hip arthroplasty. The purpose of this study was to compare polyethylene wear in patients who had undergone bilateral total hip arthroplasty with implants that differed only with regard to the material used for the femoral head: a zirconia head was used on one side, and a cobalt-chromium head was inserted on the contralateral side. A prospective, randomized study was performed to evaluate the outcomes in fifty-two patients who had undergone sequential bilateral primary total hip replacement. A zirconia head was used in one hip, and a cobalt-chromium head was used in the other. There were forty-eight men and four women; the mean age at the time of surgery was 44.2 years. The mean duration of follow-up was 7.1 years. Clinical and radiographic evaluations were performed preoperatively and at six weeks; three, six, and twelve months; and yearly postoperatively. Linear wear of the polyethylene liner was measured radiographically. Two femoral components with a zirconia head had aseptic loosening and were revised. The explanted heads were evaluated with use of interferometry, environmental scanning electron microscopy, and x-ray diffraction studies. The mean polyethylene wear rate was 0.08 mm/yr in association with the zirconia heads and 0.17 mm/yr in association with the cobalt-chromium heads (p = 0.004). The mean amount of volumetric polyethylene wear was 350.8 mm3 in association with the zirconia heads and 744.7 mm3 in association with the cobalt-chromium heads (p = 0.004). With regard to surface roughness, the Ra values of the two explanted zirconia heads were 15.87 and 17.35 nm and the Rpm values were 153.86 and 156.18 nm. Two identical zirconia heads that had not been implanted had Ra values of 5.31 and 5.48 nm and Rpm values of 65.27 and 66.35 nm. Four unimplanted cobalt-chromium heads that were identical to the ones implanted in this study had Ra values ranging between 25 and 50 nm and Rpm values ranging between 262.6 and 525.2 nm. Little phase transformation was noted in the two revised zirconia heads. The mean amount and rate of polyethylene wear were significantly lower in the hips with a zirconia head than they were in the hips with a cobalt-chromium head, presumably because the zirconia heads had a smoother articulating surface.

COMPARISON OF POLYETHYLENE WEAR ASSOCIATED WITH COBALT-CHROMIUM AND ZIRCONIA HEADS AFTER TOTAL HIP REPLACEMENT

Background: A ceramic femoral head is an alternative to a metal femoral head for the bearing surface of total hip arthroplasty. The purpose of this study was to compare polyethylene wear in patients who had undergone bilateral total hip arthroplasty with implants that differed only with regard to the material used for the femoral head: a zirconia head was used on one side, and a cobalt-chromium head was inserted on the contralateral side. Methods: A prospective, randomized study was performed to evaluate the outcomes in fifty-two patients who had undergone sequential bilateral primary total hip replacement. A zirconia head was used in one hip, and a cobalt-chromium head was used in the other. There were forty-eight men and four women; the mean age at the time of surgery was 44.2 years. The mean duration of follow-up was 7.1 years. Clinical and radiographic evaluations were performed preoperatively and at six weeks; three, six, and twelve months; and yearly postoperatively. Linear wear of the polyethylene liner was measured radiographically. Two femoral components with a zirconia head had aseptic loosening and were revised. The explanted heads were evaluated with use of interferometry, environmental scanning electron microscopy, and x-ray diffraction studies. Results: The mean polyethylene wear rate was 0.08 mm/yr in association with the zirconia heads and 0.17 mm/yr in association with the cobalt-chromium heads (p = 0.004). The mean amount of volumetric polyethylene wear was 350.8 mm3 in association with the zirconia heads and 744.7 mm3 in association with the cobalt-chromium heads (p = 0.004). With regard to surface roughness, the Ra values of the two explanted zirconia heads were 15.87 and 17.35 nm and the Rpm values were 153.86 and 156.18 nm. Two identical zirconia heads that had not been implanted had Ra values of 5.31 and 5.48 nm and Rpm values of 65.27 and 66.35 nm. Four unimplanted cobalt-chromium heads that were identical to the ones implanted in this study had Ra values ranging between 25 and 50 nm and Rpm values ranging between 262.6 and 525.2 nm. Little phase transformation was noted in the two revised zirconia heads. Conclusions: The mean amount and rate of polyethylene wear were significantly lower in the hips with a zirconia head than they were in the hips with a cobalt-chromium head, presumably because the zirconia heads had a smoother articulating surface. Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

Stellar surface imaging using closure phase

We describe the use of interferometry to make images of features on the surfaces of cool stars. We describe observations of Betelgeuse ( α Ori) and use this example to illustrate the requirements for astrophysical imaging with interferometers. We emphasise the importance of obtaining closure phase measurements and good Fourier plane coverage when imaging complex objects.

Ultrastable laser array at 633 nm for real-time dimensional metrology

We describe a laser system for very-high-accuracy dimensional metrology. A sealed-cavity helium–neon laser is offset locked to an iodine-stabilized laser in order to realize a secondary standard with higher power and less phase noise. Synchronous averaging is employed to remove the effect of the frequency modulation present on the iodine-stabilized laser. Additional lasers are offset locked to the secondary standard for use in interferometry. All servo loops are implemented digitally. The offset-locked lasers have intrinsic linewidths of the order of 2.5 kHz and exhibit a rms deviation from the iodine-stabilized laser below 18 kHz. The amplitude noise is at the shot-noise limit for frequencies above 700 kHz. We describe and evaluate the system in detail, and include a discussion of the noise associated with various types of power supplies.

Insights into MOCVD process control as revealed by laser interferometry

In-situ laser interferometry has been used to study the nucleation of CdTe on basal plane sapphire in MOCVD growth. The nucleation delay and nucleation thickness were seen to be influential in the determination of overall buffer layer quality. This nucleation process was seen to be highly complex and the nucleation delay and nucleation layer thickness were seen to vary for constant conditions of nucleation II:VI ratio and temperature. A possible link between nucleation delay and nucleation temperature has been commented on. The results for CdTe on sapphire suggest that for consistent metalorganic chemical vapor deposition (MOCVD) growth conditions from run to run during the nucleation stage, the nucleation delay and thickness may still vary as a function of subtle differences in the substrate growth surface. This argument is further substantiated by our observations using laser interferometry to study the nucleation of CdTe on Si (211) in MOCVD, where different surface preparatory treatments were employed. Laser interferometry was found to be sensitive to differences in surface treatment of the Si substrates prior to ZnTe/CdTe growth. The benefits of the use of interferometry to study and to control the nature of complex epitaxial systems is discussed.

Absolute sphericity measurement:?a comparative study of the use of interferometry and a Shack–Hartmann sensor

A comparison of absolute sphericity measurements with a ShackHartmann sensor and a TwymanGreen interferometer is presented. The absolute deviations of a test sphere from its ideal shape were calculated in both cases from the measured wave aberrations of three different positions. Very good qualitative and quantitative agreement of the results was achieved. The difference of the root-mean-square values of the two methods was 1/1000 of a wavelength.