Interference Fringe Pattern Research Articles

Measurement of microstrains across loaded resin–dentin interfaces using microscopic moiré interferometry

Little is known about the mechanical behavior of resin–dentin interfaces during loading. The presence of relatively compliant hybrid and adhesive layers between stiffer dentin and resin composite should deform more during compressive loading. Objective The objective of this study was to measure changes in microstrain across bonded dentin interfaces in real time using a recently developed microscope moiré interferometer. Method This system used a miniature moiré interferometer, using two CCD cameras for simultaneous recording of longitudinal and transverse deformation fields, a piezotransducer for fringe shifting and use of a microscope objective with magnification up to 600×. Small beams (1 mm × 2 mm × 6 mm) of moist resin-bonded dentin covered with cross-lined diffraction grating replica were placed in a miniature compression tester to allow controlled loading from 2 to 37 N while imaging the interference fringe patterns. Results Resin-dentin interfaces created by bonding dentin with Single Bond/Z100, under compressive loading, exhibited comparatively large strains across the adhesive–hybrid interface. When the wrapped phase maps were unwrapped to permit conversion of fringe order to displacements, the 2-D profiles of strain fields revealed non-uniform strains across the adhesive interface. In the adhesive/hybrid layer zone, the negative strain was larger (i.e. −6000 μɛ) than that seen in the adjacent resin composite or underlying mineralized dentin. The changes were elastic because they disappeared when the load was removed. Significance Microscopic moiré interferometry can be very useful in revealing real-time strain across bonded interfaces under load.

Digital speckle interferometry for assessment of surface roughness

In this work, the principle of interferometry is used to assess the surface roughness of the machined surfaces. Interferometry produces an interference fringe pattern when two or more light waves interact with each other. It is one of the important tool for precision optical metrology and testing. Well-known advantages of the phase shifting interferometry include high measurement accuracy, rapid measurement, good result even with low contrast fringes and that the polarity of the wave front can be determined. In fringe projection techniques, a known optical fringe pattern is projected onto the surface of interest. The fringe pattern on the surface is perturbed in accordance with the profile of the test surface, thereby enabling direct derivation of surface profile. In this work, an attempt has been made to assess the surface roughness using a speckle fringe analysis method of five frame phase shift algorithm for machined surface (ground surface). As these fringes are too noisy, advanced filtering technique has been used so as to reduce noise and to get improved wrapped phase map from the phase shifted fringes. A phase unwrapping software has been developed using discrete cosine transform (DCT) to generate the three-dimensional (3-D) profiles. Finally, it is compared with R a values measured using a mechanical stylus instrument, showing good agreement.

Experimental realization of macroscopic coherence by phase-covariant cloning of a single photon

We investigate the multiphoton states generated by high-gain optical parametric amplification of a single injected photon, polarization encoded as a ``qubit.'' The experiment configuration exploits the optimal phase-covariant cloning in the high gain regime. The interference fringe pattern showing the nonlocal transfer of coherence between the injected qubit and the mesoscopic amplified output field involving up to 4000 photons has been investigated. A probabilistic method to extract full information about the multiparticle output wave function has been implemented.

Using micro-FTIR spectroscopy to measure volatile contents in small and unexposed inclusions hosted in olivine crystals

A new technique is described that makes it possible to use micro-Fourier Transform Infra-Red (micro-FTIR) spectroscopy to determine H 2O and CO 2 concentrations in unexposed melt inclusions hosted in olivine crystals. Previously, inclusions have had to be doubly polished, and even then it has been problematic to obtain pure glass spectra through inclusions smaller than 100 μm. The new technique involves calculating the proportion of inclusion in transmittance spectra taken through the inclusion and the olivine host, which, when combined with accurate overall thickness determinations from interference fringe patterns on reflectance spectra, allows the inclusion thickness to be calculated. This thickness can then be used with the absorbance of volatile species in the transmittance spectra to calculate accurate and precise analyte concentrations. Application of this technique will greatly ease sample preparation and allow the H 2O and CO 2 concentrations to be measured in many more olivine hosted inclusions than was previously possible by FTIR. The minimum size of an inclusion that can be completely analysed will be limited by the analytical sensitivity of FTIR, and the resolution of other in situ analytical techniques used to fully characterise the geochemistry of inclusions.

Multiplexing of Fiber-Optic Long-Period Grating-Based Interferometric Sensors

Two long-period gratings (LPGs) fabricated in series in an optical fiber form a Mach-Zehnder interferometer, producing a sinusoidal channelled spectrum within the characteristic LPG attenuation bands, which has the appearance of an interference fringe pattern. The phase of the fringes is sensitive to changes in the surrounding environmental parameters, such as refractive index. Fabrication of a number of identical cascaded LPG pairs with different separations produces independent fringe patterns of different frequencies within the attenuation bands. The application of basic Fourier techniques to analyze the transmission spectrum allows the phase of each fringe pattern to be determined independently, facilitating the differentiation of external effects acting on each interferometer

Quantum interference between multi photon absorption pathways in organic solid

We demonstrate spatial interference fringe pattern by simultaneous one- and three-photon absorption of UV and near-IR femtosecond pulses in thin film organic solid at room temperature. We use organic dendrimers that are specially designed to have strong fluorescence and very large three-photon absorption cross-section. High fringe visibility allows the quantum interference to be observed by eye.

Measurement of Shock Waves Using an Acousto-Optic Laser Deflector

Laser interference fringe patterns and shadowgraphs were obtained with a minimum exposure time of 200 ns using an acousto-optic laser deflector. Experimental results showed that this method has sufficient spatial and temporal resolution to image the wavefront of shock waves generated by laser-induced breakdown in air. The shock waves propagated at a speed of over 103 m/s immediately after breakdown, and at a nearly constant speed of about 510 m/s for 3-9 μs after breakdown. The width of the wavefront of the shock wave was measured to be 0.17 mm, and the neutral density variation at the wavefront was estimated to be 9×1024 m-3.

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Passive control of the shock wave/turbulent boundary-layer interaction utilizing slotted plates and a porous plate over a cavity has been carried out. Effect of various slot configurations on the characteristics of the interaction has been observed. Pitot/wall surface pressure distributions and flow visualizations including Schlieren images, kerosene-lampblack tracings and interference fringe patterns over a thin oil-film have been obtained at the downstream of the shock interactions. For the streamwise-slot configuration, a local higher pitot pressure was noticed at the downstream of the interaction as compared with the case of no control, however, not much improvement in pitot pressure was observed for the spanwise-slot configuration.Ā؀會Ā؀㢖ﾖ⨀㡡綴ࠀĀࠀ會Āࠀ邖ﾖ⨀쁧綴Ā᐀會Ā᐀ﾖ⨀⡧綴ሀĀ저會Ā저䂗ﾖ⨀큡綴ഀĀ᐀會Ā᐀颗ﾖ⨀桢綴ഀĀ᐀會Ā᐀ﾖ⨀つ綴먁瀀ꀏ會Ā䢘ﾖ⨀쁧綴Ā᐀會Ā᐀ꂘﾖ⨀塨綴ሀĀ㰀會Ā㰀ﾖ⨀綴؀Ā㈀會Ā㈀備ﾖ⨀衩綴Ā᐀會Ā᐀ꢙﾖ⨀綴Ā᐀會Ā᐀šﾖ⨀롪綴Ā저會Ā저墚ﾖ⨀恥綴ጀĀ저會Ā저낚ﾖ⨀綴Ā저會Ā저࢛ﾖ⨀遦綴Ā저會Ā저悛ﾖ⨀c綴؀Ā؀會Ā؀뢛ﾖ⨀顣綴⸀

Interference fringe pattern analysis using inverse cosine function

AbstractThe analysis of interference fringe patterns is a technique which is indispensable in estimating the shape of an object or the refractive index field of a solution from the interference fringe pattern image. In the methods proposed to date, however, satisfactory analysis has been difficult in situations where the image contains only a few fringes, the object shape is not smooth, or the target of measurement is continuously changing with time. This paper proposes the following method of analysis. The inverse cosine function (arccos function) is applied to the interference fringe pattern image after normalizing the intensity. Then the phase inversion is estimated by assuming a monotonically increasing phase. The method is a combination of simple ideas derived from the principles of interference fringe patterns, but can be used to calculate the phase for each pixel from a single interference fringe pattern image. Depending on the conditions, analysis with higher temporal and spatial resolutions than in the Fourier transform method can be achieved. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(1): 61–73, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20325

Head–disk spacing measurement based on Michelson interferometry using white light illumination

Head–disk spacing of hard disk drives was measured based on Michelson interferometry using white light illumination. This method utilizes the phase comparison of two interference fringe patterns formed respectively on the inner surface of a glass disk and the air bearing surface of a slider through the glass disk. To suppress interference noise and to further enhance measurement accuracy, low coherent white light was adopted as an illuminating source to replace high coherent laser. A high sensitive CCD digital camera was used to compensate for the attenuation of the brightness and contrast of the interference fringe pattern in the white light-based Michelson interferometer. The captured images and the measured results indicate that the application of white light illumination effectively improves the interference fringe pattern, and the measurement error of extracting the ridgeline can be consequently reduced five times in comparison with a laser. Spacing resolution (=λ/2w) was enhanced to 0.68 nm/pixel in our experiment, closely approaching the extreme spacing resolution (at the largest fringe interval wmax) of 0.64 nm/pixel. Indirect and direct methods for determining fringe interval were proposed, and the latter provides higher accuracy. Head–disk spacing was measured at different spacing resolutions of 2.61 and 0.68 nm/pixel to clarify the effect of fringe interval on measurement accuracy. The results show that tested spacing at larger fringe interval achieves not only better agreement with the calculated example, but also better deviation tolerance characteristics. Based on the advantages, measurement of 10 nm spacing was realized with high accuracy and good repeatability.

Theoretical and experimental investigation of low-noise optoelectronic system configurations for low-coherent optical signal detection

In low-coherent measurement techniques two kinds of optical signal processing can be used -spectral and temporal. When the temporal signal processing is used, the most critical problem is to identify the position of the central fringe in the interference fringe pattern. It is so important because this position corresponds to the zero of optical path difference and gives information about a measurand. Therefore, it is necessary to use the low-noise optical signal detection set-up in the low-coherent measurement systems. One of the most effective methods of noise-reduction in low-coherent system is using detection system in balanced configuration. In this article, authors present the designed low-coherent optical signal detection system. This system enables us to perform balanced and un-balanced detection, which allows to compare parameters of both configurations. The authors describe theoretical and experimental investigation of balanced and un-balanced low-coherent optical signal detection system.

Measuring the refractive indices of liquids with a capillary tube interferometer

A theoretical analysis of the fringe pattern produced by a capillary tube interferometer is presented, which is expected to be two-beam interference, and a computer program to simulate the interference fringe pattern is established. By comparing the simulated fringe pattern and the experimental fringe pattern, the refractive index of the liquid can be given when the two fringes coincide best. The results of this method are close to those of the Abbe refractometer.

Complete chirp analysis of a gain-switched pulse using an interferometric two-photon absorption autocorrelation

We propose a simple but powerful scheme for the complete analysis of the frequency chirp of a gain-switched optical pulse using a fringe-resolved interferometric two-photon absorption autocorrelator. A frequency chirp imposed on the gain-switched pulse from a laser diode was retrieved from both the intensity autocorrelation trace and the envelope of the second-harmonic interference fringe pattern. To verify the accuracy of the proposed phase retrieval method, we have performed an optical pulse compression experiment by using dispersion-compensating fibers with different lengths. We have obtained close agreement by less than a 1% error between the compressed pulse widths and numerically calculated pulse widths.

Characters of surface deformation and surface wave in thermal capillary convection

In the field of fluid mechanics, free surface phenomena is one of the most important physical processes. In the present research work, the surface deformation and surface wave caused by temperature difference of sidewalls in a rectangular cavity have been investigated. The horizontal cross-section of the container is 52 mm×42 mm, and there is a silicon oil layer of height 3.5 mm in the experimental cavity. Temperature difference between the two side walls of the cavity is increased gradually, and the flow on the liquid layer will develop from stable convection to un-stable convection. An optical diagnostic system consisting of a modified Michelson interferometer and image processor has been developed for study of the surface deformation and surface wave of thermal capillary convection. The Fourier transformation method is used to interferometer fringe analysis. The quantitative results of surface deformation and surface wave have been calculated from a serial of the interference fringe patterns. The characters of surface deformation and surface wave have been obtained. They are related with temperature gradient and surface tension. Surface deformation is fluctuant with time, which shows the character of surface wave. The cycle period of the wave is 4.8 s, and the amplitudes are from 0 to 0.55 μm. The phase of the wave near the cool side of the cavity is opposite and correlative to that near the hot side. The present experiment proves that the surface wave of thermal capillary convection exists on liquid free surface, and it is wrapped in surface deformation.

Determination of the membrane permeability coefficient under concentration polarisation conditions

Diffusive transport of a substance through a membrane separating solutions of different concentrations leads to the formation of concentration boundary layers (CBLs) adjacent to its surfaces. This phenomenon, commonly referred as concentration polarisation, causes the permeability coefficient measured in a membrane system to be smaller than the permeability of the membrane. The diffusion processes in the membrane system consisting of two cells separated by a horizontally located membrane were studied by using aqueous binary solutions of ethanol. To observe the time evolution of the CBLs, the laser interferometric technique was used: the interference fringe pattern provided quantitative measurement of the substance concentration C( x,t) at position x and time t. The concentration profiles were constructed by recording the interferograms with a given time step Δ t; and on this basis, the CBL thicknesses were obtained. On the basis of these investigations, a practical and valuable method is proposed which can determine the membrane permeability coefficient under concentration polarisation conditions without the need for stirring solutions.

Infrared Spectroscopy of Solid Hydrogen Sulfide and Deuterium Sulfide

The infrared spectra of solid hydrogen sulfide (H2S) and deuterium sulfide (D2S) were collected at very low temperatures. Vapor deposition of thin films at the lowest temperature of 10 K produced amorphous solids while deposition at 70 K yielded the crystalline phase III. Infrared interference fringe patterns produced by the films during deposition were used to determine the film thickness. Careful measurement of the integrated absorbance peaks, along with the film thickness, allowed determination of the integrated band intensities. This report represents the first complete presentation of the infrared spectra of the amorphous solids. Observations of peaks near 3.915 and 1.982 microm (ca. 2554 and 5045 cm(-1), respectively) may be helpful in the conclusive identification of solid hydrogen sulfide on the surface of Io, a moon of Jupiter.

An optical probe stage and its applications in mechanical behavior measurements of micro-objects and thin films

The rapid development of a wide variety of new devices in microelectronics, sensors, MEMS and NEMS has led to new challenges in characterizing their mechanical behavior and assessing their reliability. Static and dynamic mechanical behavior measurement of micro-objects and low-dimension films has become a key issue. In this paper, an optical probe stage has been proposed to test the deformation of micro-objects. The technique is based on optical interferometry and actuator-driven cantilever/plate deformed probes. In the proposed apparatus, a monochromatic object light is used to illuminate the deformed probes and measured micro-objects. The interference fringe pattern related to deformations of deflections of the probes and the micro-objects was analyzed to obtain the loading forces exerted by the probes and the deformations of micro-objects. Properties of static and dynamic deformations of different kinds of probes were investigated and the optical probe stage was applied in deformation measurement, microforce testing and bonded wire fatigue analysis of a metal-oxide semiconductor chip.

Delamination under Hertzian cyclic loading of a glass coating on Ti6al4v for implants

In this work, the interfacial response of a glass-based coating on Ti6Al4V to monotonic and cyclic Hertzian (spherical) indentation is investigated. This coating belongs to the SiO2-CaO-MgO-Na2O-K2O-P2O5 system and it is specifically designed to be used as the inner layer of a bioactive bilayer coating with an outer layer of lower SiO2 content to ensure bioactivity. During Hertzian monotonic loading, delamination of the coating occurs, which is revealed in the microscope by the presence of a colour pattern of interference fringes at the interface. Hertzian cyclic loading at maximum loads, Pmax, lower than the monotonic delamination load, PDel, also generates delamination damage. A plot of Pmax versus the number of cycles for delamination shows a two-slope curve with a “knee” for Pmax close to the critical load to induce a radial crack from the interface, PRc. The analysis of the delamination morphology and the results for different load ratios, R = Pmin/Pmax, confirmed the existence of two different delamination mechanisms with a common feature of plastic deformation of the substrate but with a different dependence with the maximum applied load: for Pmax > PRc the process is mostly controlled by the presence of the radial cracks (Pmax dependent), meanwhile, for Pmax < PRc radial cracks are not observed and delamination is attributed to the residual stress at the interface induced by the cyclic plastic deformation of the substrate and the elastic recovery of the coating during unloading part.

Quantitative phase demodulation from a free-running Michelson interferometer by using a novel quadrature moiré grating with misalignment error compensation

This paper describes a novel technique to perform fast phase demodulation in Michelson interferometers without any need for phase locking or heterodyning, thus enabling quantitative detection of vibrations in a noncontacting mode. The new scheme greatly simplifies the optical design of laser interferometers used for nondestructive evaluation of materials. It uses a matched moire grating to transform the interference fringe pattern formed between the reference and signal beams into intensity modulation. It one divides the filter into four quadrants so that the gratings in each quadrant have been shifted to represent an equivalent phase difference of /2, the intensity signals collected behind the four quadrants effectively represent four simultaneous data points due to phase stepping, covering the full cycle. This means that a unique phase measurement can be obtained at any arbitrary phase position, and thus the interferometer may be left to operate in free-running mode. Since all the four signals originate from the same laser source, appropriate differential signal processing can be incorporated to remove intensity noise due to fluctuations in the laser source. In addition, we have studied the effect of angular misalignment between the grating filter and the interference fringe pattern. Our results show that such misalignments may be compensated through a back-substitution algorithm. This further enhances the practical benefits of our scheme in real situations.

A Method to Remove Fringes from Images Using Wavelets

We have developed a new method that uses wavelet analysis to remove interference fringe patterns from images. This method is particularly useful for flat fields in the common case where fringes vary between the calibration and object data. We analyze the efficacy of this method by creating fake flats with fictitious fringes and removing the fringes. We find that the method removes 90% of the fringe pattern if its amplitude is equal to the random noise level and 60% if the fringe amplitude is ≈1/10 of the noise level. We also present examples using real flat-field frames. A routine written in IDL that implements this algorithm is available from the authors and as an attachment to this paper.