Diffraction Fringes Research Articles

Non-contact online inspection method for the appearance diameter uniformity of chemical fiber filaments

As chemical fiber filaments diameter variation directly affects spinning quality, spinning condition monitoring becomes more and more important in an intelligent manufacturing environment. Firstly, based on the single-slit Fraunhofer diffraction model and the Babinet principle, the non-contact filaments diffraction model is developed to generate diffraction fringe patterns by irradiating chemical fiber filaments with He–Ne laser. Secondly, for the characteristics of diffraction fringe patterns, a segmentation mask window-based diffraction fringe center of gravity extraction method is proposed, and a zero-phase Butterworth low-pass filter is designed and applied to the diffraction light intensity curves to accurately extract the extreme points positions of the adjacent dark fringe and calculate the diameter information. Finally, the non-contact chemical fiber filaments appearance diameter online inspection experiment platform is built to carry out static and dynamic experiments of filaments. The experimental results show that the maximum absolute value of absolute error is less than 1.1 μm for static measurement and less than 10 μm for dynamic measurement.

Measurement of transparent liquid concentration based on ultrasonic grating method

In this experiment, ultrasonic grating method is used to measure the concentration of transparent liquid. The principle is that the liquid forms standing waves, namely ultrasonic grating, by using a signal generator. The monochromatic parallel light diffracted after entering the ultrasonic grating, and the sound velocity could be obtained by the spacing of diffraction fringes. The experimental equipment includes three parts: light source system, ultrasonic generation system and digital observation system. The experimental test shows that the experimental device can be used to measure the concentration of sugar water, salt water and other transparent liquid, with simple operation and high measurement accuracy.

NON-CONTACTLESS MEASUREMENT OF ALPACA HAIR DIAMETER

The article presents the results of a study of the diameter of alpaca hair using the laser technology. The dependence of the hair diameter change on such fac-tors as the distance of the hair from the screen, the position of the diffraction fringes was analyzed. The values of these factors caused the hair diameter to fluctuate. Based on the experiments, it was shown that by using of laser light diffraction, it is possible to measure very thin alpaca hair.

Improving diameter measurement from Fraunhofer diffraction with fringe segment splicing.

Fraunhofer diffraction is an easy but powerful method for measuring the diameter of a thin filament. In practice, however, the diffraction pattern attainable is always subject to limits imposed by various imperfections in real systems, such as small angle approximation and sensor threshold, thus degrading the measurement resolution. In this Letter, we propose a method of fringe segment splicing for improving the diameter measurement from Fraunhofer diffraction. The fringe segment is chosen from a real diffraction pattern and is used to reproduce an ideal diffraction fringe, where the theoretical estimates give the best approximation to the observations. The problem of diameter measurement is solved in the spatial frequency-domain with an ideal diffraction fringe. Our results show that the relative error in this method is less than 0.1% and is far superior to that of previous methods.

Electron Diffraction Experiment Disturbed by Magnetic Field

The Copenhagen interpretation of quantum mechanics believes that as long as it is monitored, the diffraction fringes of electrons will disappear. There have been no scientific reports on the "electron diffraction experiment monitored by a magnetic field" for a long time (there are only popular science reports in this area). Now, the electron diffraction experiment disturbed by the permanent magnet has been completed. As a result, the interference of the magnetic field can deform and drift the electron diffraction fringes, but will not cause the diffraction fringes to disappear. It clearly shows that the interference of the measurement cannot make the wave-particle duality particles collapse into complete particles. This is an experimental counterexample in quantum mechanics (also a dark cloud over quantum mechanics). Both "the existence of the superposition of quantum states" and "the superposition of quantum states cannot withstand any observation and surveillance" are doubtful.

Investigation of wrinkle artifacts along metallic fatigue cracks in phase contrast synchrotron tomography via simulations and experiments

• X ray imaging simulations are used to study the formation of artifacts (wrinkle artifact) in phase contrast tomographic images. • Practical solutions to reduce those wrinkle artifacts are predicted and their efficiency is demonstrated in the case of fatigue cracks in metals. • The physical origin of wrinkle artifacts is discussed. Due to higher lateral coherence length of beams available at high brilliance synchrotron sources, the presence of diffraction fringes on crack edges and at crack tips can improve crack detectability in the reconstructed Synchrotron Radiation Computed Tomography (SRCT) images. However, when the crack shape is less planar and more disturbed, strong artifacts (named here wrinkle artifacts) in SRCT images are found all along crack edges leading to difficulties in quantitative analysis of cracks. To investigate the origin of these artifacts and to find some ways to reduce them, phase contrast tomography simulations (using GATE software) associated with experiments (conducted at ESRF) were performed. We show that these artifacts come from Fresnel interference patterns on the detector which are especially strong when the crack orientation is normal to the rotation axis, and they can be reduced by minimizing the phase contrast intensity (smaller sample-to-detector distance or higher X-ray energy) or simply by inclining cracks with respect to the plane defined by the beam trajectory.

Application of Optical Path Drawing Technology: The Light Intensity Problem of Double-Slit Interference

The wave nature of light has been widely demonstrated in a double-slit experiment, which has played a special role in physics teaching. When monochromatic light passes through the double-slit sheet, the diffraction and interference fringes can be observed in the far-field regime. The interference of light causes the beams passing through the two slits to interact with each other, but each slit still retains the diffraction characteristics of a single slit, so the result is a combination of diffraction and interference patterns.

Long-Range Blockage Prediction Based on Diffraction Fringe Characteristics for mmWave Communications

Blockage prediction is significant to support mobility for millimeter wave (mmWave) communications, while the prediction range is limited to centimeters in current work. This letter proposes a long-range blockage prediction scheme leveraging the frequency-dependent diffraction fringe characteristics. Firstly, Fresnel-Kirchhoff diffraction is introduced into a communication blockage scenario to analyze the received power of a mobile terminal. An interesting diffraction phenomenon is found that the received power fluctuates with an increasing amplitude before the blockage occurs, and the fluctuation range is frequency-dependent. Inspired by the diffraction fringe characteristics, a blockage feature (BF) based scheme is proposed to predict an upcoming blockage. Then, long-range mmWave blockage prediction is achieved by leveraging sub-6 GHz BF. Finally, a ray-tracing based simulation is utilized to validate our scheme and blockage prediction range can be extended to several meters.

Lensless light intensity model for quasi-spherical cell size measurement.

Quasi-spherical cell size measurement plays an important role in medical test. Traditional methods such as a microscope and a flow cytometer are either it depends on professionals and cannot be automated, or it is expensive and bulky, which are not suitable for point-of-care test. Lab-on-a-chip technology using the lensless imaging system gives a good solution for obtaining the quasi-spherical cell size. The diffraction effects and the low resolution are the two main problems faced by the lensless imaging system. In this paper, a lensless light intensity model for the quasi-spherical cell size measurement is given. First, the diffraction characteristics of a quasi-spherical cell edge are given. Then, a diffraction model at an arc edge is constructed based on the Fresnel diffraction at a straight edge. Using the diffraction model at an arc edge, we explained the mechanism of the formation of the quasi-spherical cell diffraction fringes. Finally, the light intensity of the first bright ring of the quasi-spherical cell diffraction pattern is used to achieve quasi-spherical cell size measurement. The required equipment and the measurement methods are extremely simple, very suitable for point-of-care test. The experimental results show that the proposed model can realize the statistical measurement of the quasi-spherical cells and the classification of the quasi-spherical cells with a difference of 1 [Formula: see text].

Characterisation of needle edge quality using diffraction pattern

The performance of hypodermic needlesismainlydependentonquality of theiredges. The quality oftheneedle edges directly impactspenetration forces, tissue healing time, andpatientpain. At present, only subjective techniques are used to access quality of edges of the needles which are not capable to contribute during manufacturing. Thus anappropriatetechnique is desirable to characterize the defects of the needle edges. This study aims to develop a characterization technique for measurement of defects such as roughness, chips and tip bending on the edges of needles. The proposed technique uses the diffraction fringes, obtained from the superposition of diffracted light from needle edges and the direct propagated light from the source. Variations in the fringes and their intensity profiles are utilized to study the defects. Further, the results are compared with results obtained from a standard optical profiler and a microscope. The standard deviation of proposed technique for repeatability and reproducibility of measurements are σ = 0. 104 a.u and σ = 0. 87 a.u, respectively. This technique is simple, non-contact in nature, uses compact configuration and is capable for qualitative and quantitative evaluation of the hypodermic needles.

TILTED FIBER BRAGG GRATING SENSORS FOR REFRACTIVE INDEX MEASUREMENTS OF LIQUID SOLUTIONS

This publication presents the basic assumptions about the light guiding mechanisms in tilted fiber Bragg gratings, transmission spectra of the fiber with such structures and their sensor properties related to the occurrence of the so-called cladding modes. The light in the form of modes coupled to the optical fiber cladding causes their spectral properties to depend on the difference in the refractive indices of the surrounding medium and the fiber cladding. With the introduction of a small inclination angle of the diffraction fringes forming the Bragg grating, the cladding modes show sensitivity to changes in the refractive index of the environment of aqueous solutions, which makes the spectrum of their applications broad. This publication presents changes in the spectra of selected modes measured for solutions with a specific refractive index, shift sensitivity, and changes in the mode transmission coefficient and processing characteristics at a selected concentration range of solutions. Experimental results show that high order cladding modes respond both by shifting the central wavelength as well as by changing the transmission minimum. In selected ranges, these parameters show a linear characteristic as a function of changes in the concentration of the cane sugar aqueous solution. In the case of TFBG with a tilt angle of 8 °, the sensitivity of wavelength changes is 0.012nm / RIU for solutions with concentrations ranging from 0% to 10% by weight.

Crystalline quality of GaAs1−x Bi x grown below 250 °C using molecular beam epitaxy

This study revealed the crystalline quality of the dilute bismide alloy GaAs1−x Bi x grown on a GaAs(001) substrate below 250 °C using molecular beam epitaxy. The substrate temperature and As flux played a dominant role in tuning the crystal structure between amorphous and single crystalline GaAs1−x Bi x , as well as in the Bi introduction in GaAs below 250 °C. Sample characterization demonstrated a substrate temperature of 250 °C produced single crystalline ∼200 nm thick GaAs0.982Bi0.018 with clear X-ray diffraction fringes, while the lower substrate temperature of 180 °C yielded an amorphous film. Rutherford backscattering spectrometry showed sufficient As supply at the growing surface provides uniform Bi distribution.

Negative index metamaterial at ultraviolet range for subwavelength photolithography.

A negative index metamaterial (NIM) at ultraviolet range is constructed with stacked plasmonic waveguides. Based on the waveguides performing antisymmetric modes, the negative refractions of both wavevector and energy flow are realized when a TM-polarized light with a wavelength of 365nm incidents on the plane of the layers. It is proved that the NIM could be introduced into subwavelength photolithography for extending working distance. Both theoretical and experimental results indicate that the patterns with a feature size of 160nm can be reproduced in photoresist with a 100nm-thick air working distance. Moreover, arbitrary two-dimensional patterns with a depth reach 160nm can be obtained without diffraction fringe by employing a nonpolarized light. This design gives new insights into the manipulation of light. The improved working distance, well-shaped patterns over large area present an innovative method for improving subwavelength photolithography.

Evaluation and comparison of a CdTe based photon counting detector with an energy integrating detector for X-ray phase sensitive imaging of breast cancer.

To compare imaging performance of a cadmium telluride (CdTe) based photon counting detector (PCD) with a CMOS based energy integrating detector (EID) for potential phase sensitive imaging of breast cancer. A high energy inline phase sensitive imaging prototype consisting of a microfocus X-ray source with geometric magnification of 2 was employed. The pixel pitch of the PCD was 55μm, while 50μm for EID. The spatial resolution was quantitatively and qualitatively assessed through modulation transfer function (MTF) and bar pattern images. The edge enhancement visibility was assessed by measuring edge enhancement index (EEI) using the acrylic edge acquired images. A contrast detail (CD) phantom was utilized to compare detectability of simulated tumors, while an American College of Radiology (ACR) accredited phantom for mammography was used to compare detection of simulated calcification clusters. A custom-built phantom was employed to compare detection of fibrous structures. The PCD images were acquired at equal, and 30% less mean glandular dose (MGD) levels as of EID images. Observer studies along with contrast to noise ratio (CNR) and signal to noise ratio (SNR) analyses were performed for comparison of two detection systems. MTF curves and bar pattern images revealed an improvement of about 40% in the cutoff resolution with the PCD. The excellent spatial resolution offered by PCD system complemented superior detection of the diffraction fringes at boundaries of the acrylic edge and resulted in an EEI value of 3.64 as compared to 1.44 produced with EID image. At equal MGD levels (standard dose), observer studies along with CNR and SNR analyses revealed a substantial improvement of PCD acquired images in detection of simulated tumors, calcification clusters, and fibrous structures. At 30% less MGD, PCD images preserved image quality to yield equivalent (slightly better) detection as compared to the standard dose EID images. CdTe-based PCDs are technically feasible to image breast abnormalities (low/high contrast structures) at low radiation dose levels using the high energy inline phase sensitive imaging technique.

Fresnel diffraction lithography

Lithography plays a vital important role in modern information technologies. Patterning on a nanoscale in a handy way is highly desired for both scientific and industrial purposes. In this work, we propose a convenient nanolithography method based on Fresnel diffraction patterns. We start with the explanation of the “dense-inside-sparse-outside” Fresnel diffraction fringes resulting from the apertures of finite extent, by using the fast Fourier transform algorithm through appropriately choosing the number of uniformly spaced samples. Moderately focusing the diffraction patterns via high-numerical-aperture objectives ( the method is termed the “Fresnel diffraction lithography”), the rotationally symmetric patterns with a minimum feature size of ~190 nm, and the scanning lines with a width of ~350 nm are realized, respectively, The calculation using vectorial diffraction theory suggests a better resolution when perfectly focused. This method shows good tolerance to defocus and does not require complex lens combinations or micro/nano-diffraction optical elements, Therefore, this method can find some applications in widespread areas, e.g. functional metasurfaces, as a novel and low-cost nano-patterning technology with sub-wavelength resolution and high flexibility.

Lensing from small-scale travelling ionospheric disturbances observed using LOFAR

Observations made using the LOw-Frequency ARray (LOFAR) between 10:15 and 11:48 UT on the 15th of September 2018 over a bandwidth of approximately 25–65 MHz contain discrete pseudo-periodic features of ionospheric origin. These features occur within a period of approximately 10 min and collectively last roughly an hour. They are strongly frequency dependent, broadening significantly in time towards the lower frequencies, and show an overlaid pattern of diffraction fringes. By modelling the ionosphere as a thin phase screen containing a wave-like disturbance, we are able to replicate the observations, suggesting that they are associated with small-scale travelling ionospheric disturbances (TIDs). This modelling indicates that the features observed here require a compact radio source at a low elevation and that the TID or TIDs in question have a wavelength <~30 km. Several features suggest the presence of deviations from an idealised sinusoidal wave form. These results demonstrate LOFAR’s capability to identify and characterise small-scale ionospheric structures.

Talbot photolithography optimization with engineered hybrid metal-dielectric mask: High-contrast and highly-uniform Talbot stripes

Conventional projection Talbot lithography usually employs opaque (amplitude) or transparent (phase) masks for creating a periodic array of Fresnel diffraction fringes in the photosensitive substrate. For particular mask design the longitudinal periodicity of Talbot carpet can be avoided producing quasi uniform striped pattern (Talbot stripes). We propose a novel hybrid amplitude-phase mask which is engineered for obtaining extremely smooth Talbot stripes and simultaneously high lateral optical contrast and extreme spatial resolution better than a third of laser wavelength. By means of the numerical simulations, we demonstrate the robustness of produced striped diffraction patterns against mask design deviation and light incidence angle variations. The reproducibility of the Talbot stripes is reported also for 1D and 2D metal-dielectric projection masks.

A novel experimental approach for direct observation of magnetic field induced structuration in ferrofluid

This article proposes a novel approach to investigate the field-induced structuration in ferrofluids (FFs) at room temperature. The in-house experimental setup has been fabricated to perceive the influence of dipolar interaction and particle size of dispersed magnetic nanoparticles (MNPs) in FFs on the static magneto-optical (MO) properties under the influence of an external magnetic field. The diffraction fringes are observed in FF when a high-power laser passing from the diluted fluid system which appearing at a specific dilution and varies with the different sizes and volume fraction of MNPs. The change in shape and size of the diffraction fringes is observed with the variation of both, size of dispersed MNPs and the Dilution of the FFs which is used to calculate the refractive index coefficient. The number of diffraction rings increases with an increase in the size of dispersed MNPs and its diameter decrease with an increase in particle volume fraction. The effect of thermal lens and nonlinear optical (NLO) behavior gives the validation of field-induced refractive index coefficient appearing in FFs commutated by the fringe diffraction method. Further, the variation of intensity of transmitted light has been corroborated with the forward scattering resulting from the Brownian motion of the nanoparticle. The experiment validates the chain formation in FFs, as MNPs are working as mesoscopic cylinders resulting in specified scattering patterns. This experimental approach can lead to a new pathway for the development of potential applications such as tunable optical filters, optical limiters, and various photonics fields based on the tunable MO properties of FFs.

Application of Fresnel diffraction from the edge of a transparent plate to measurement of glucose concentration.

We present a new method for measuring the solution concentration based on laser light diffraction from the edge of a glass plate immersed in the solution. It is shown experimentally that the visibility of diffraction fringes is varied periodically with solution concentration and the period is related to light wavelength and thickness of the glass plate. There are intervals of concentrations in which the visibility-concentration curve is very near to linear. By choosing a suitable glass plate, one can change the extent of measurable concentrations and the resolution of the method. Using a 1 mm thick glass plate, we obtained a resolution of7.67×10-6g/cc in the detection of glucose concentration. The presented method is accurate and much simpler than other methods for measuring the solution concentration.

Seeking missing pieces in learning about single slit diffraction: results from a teacher survey

Single slit diffraction is part of many high-school physics curricula throughout the world. In this study, we aimed to investigate whether high-school physics teachers from Bosnia and Herzegovina, Serbia and North Macedonia are adequately prepared to discuss with their students about various aspects of the single slit diffraction pattern, particularly about vertical length of diffraction fringes. To that end we conducted a written survey which included 57 high-school physics teachers. Besides asking teachers about students’ difficulties in learning about single slit diffraction, we also asked them to specify their own difficulties with this topic and required them to solve a conceptual task. Almost every second teacher believed that vertical length of diffraction fringes can be increased by changing shape or width of the slit and only 1 out of 57 teachers managed to correctly answer why diffraction fringes become shorter when we move away from the central maximum. We concluded that physics teacher education programmes should be changed to develop understanding of both, horizontal and vertical aspects of the diffraction pattern. To that end it is useful to provide learning opportunities which encourage combining ray and wave model of light.