Images Of Interference Patterns Research Articles

Deep-learning based 3D birefringence image generation using 2D multi-view holographic images

Refractive index stands as an inherent characteristic of a material, allowing non-invasive exploration of the three-dimensional (3D) interior of the material. Certain materials with different refractive indices produce a birefringence phenomenon in which incident light is split into two polarization components when it passes through the materials. Representative birefringent materials appear in calcite crystals, liquid crystals (LCs), biological tissues, silk fibers, polymer films, etc. If the internal 3D shape of these materials can be visually expressed through a non-invasive method, it can greatly contribute to the semiconductor, display industry, optical components and devices, and biomedical diagnosis. This paper introduces a novel approach employing deep learning to generate 3D birefringence images using multi-viewed holographic interference images. First, we acquired a set of multi-viewed holographic interference pattern images and a 3D volume image of birefringence directly from a polarizing DTT (dielectric tensor tomography)-based microscope system about each LC droplet sample. The proposed model was trained to generate the 3D volume images of birefringence using the two-dimensional (2D) interference pattern image set. Performance evaluations were conducted against the ground truth images obtained directly from the DTT microscopy. Visualization techniques were applied to describe the refractive index distribution in the generated 3D images of birefringence. The results show the proposed method’s efficiency in generating the 3D refractive index distribution from multi-viewed holographic interference images, presenting a novel data-driven alternative to traditional methods from the DTT devices.

Mathematical modeling of the parameters of an electro-optic modulator in the Mach–Zehnder interferometer configuration based on thin lithium niobate films

Subject of study. An electro-optic modulator in a Mach–Zehnder interferometer configuration based on ridge waveguides made of a thin lithium niobate film was studied. Aim of study. The study aimed to mathematically model the parameters of an electro-optic modulator in a Mach–Zehnder interferometer configuration based on ridge waveguides made of a thin lithium niobate film. Method. The dependence of the optical losses introduced by a Y-branch splitter on the angle of the splitter was investigated using a beam propagation method based on the fast Fourier transform. Main results. The results of mathematical simulation of the parameters of the electro-optic modulator in the Mach–Zehnder interferometer configuration based on thin lithium niobate films were presented. The dependence of the optical losses, introduced by the Y-splitter, on the waveguide separation angle was obtained. Images of interference patterns occurring in the output waveguide were examined. A comparison revealed that the effectiveness of the proposed interferometer configuration was higher than that of the alternative solutions available in the literature. The novelty of the results is that the configuration of the electro-optic modulator investigated in this study was fabricated in the form of an integrated optical circuit based on ridge waveguides of thin-film lithium niobate. Such a solution enables a reduction in the dimensions of the final device and increases the sensitivity compared with that of existing analogs based on bulk electro-optic crystals. Additionally, owing to the use of a semiconductor substrate, an electronic circuit can possibly be integrated into the substrate, which enables the implementation of an electro-optic sensor system on a single chip. Practical significance. The method for interference pattern analysis proposed in this study provides information on the magnitude of the voltage applied to the arm of the interferometer and enables the development of requirements for its further modernization for increasing the accuracy of measurements and developing optoelectronic devices based on thin lithium niobate films, including integrated optical electric-field sensors.

COMPUTER MODEL OF INTERFERENCE PICTURES OF THE NEWTON RINGS

Examples of computer processing images of interference patterns (Newton rings) obtained by digital video camera are considered. The sequence of computer processing of the obtained images of interference patterns is described and the possibility of comparing them with a theoretical model of the intensity distribution, for which an interpolation formula is proposed, is shown. To compare the distributions, a software product was developed, a series of so-called «sliders», each of which changes one of the parameters of the interpolation formula. By changing the position of the «sliders», it is possible to approximate the parameters of the theoretical model to the distribution of the radiation intensity in a real interference pattern. Computer processing of images obtained by a digital video camera can be used in subsequent courses in the study of special disciplines, when performing research work, in processing measurement results and constructing models of physical phenomena.

Investigation and classification of fibre deformation using interferometric and machine learning techniques

We established an experimental normalized dataset containing 340 images of interference patterns for several different polymeric fibres using a two-beam polarizing interference microscope. This dataset includes the three main classes for the deformation in fibres (normal stretching, necking and crazing phenomena). To our knowledge, this is first experimental dataset for the interference patterns that contains the deformation classes. To automate the detection and the classification for the deformation classes in our dataset, a pre-trained AlexNet deep convolution neural network was utilized. We fine-tuned this network to achieve our classification task by substituting the final three layers in AlexNet with novel layers that can classify the input interference patterns into 3 classes. After training our dataset using this network, we obtained an 82.22% validation accuracy. To improve this result, we suggested a combination of the AlexNet and the support vector machine; in which, the first five convolutions layers in AlexNet were utilized only to extract the features of interference patterns in our dataset and classified them using the support vector machine. This suggested network achieved 95.64% validation accuracy. Furthermore, the 3D birefringence profiles of fibres containing normal stretched, necking and crazing phenomena were calculated.

DIGITAL TECHNOLOGIES FOR OPTICAL IMAGES PROCESSING IN LABORATORY PRACTICE IN PHYSICS

Examples of a laboratory work on wave optics are considered, in which, using the MS Office Excel program, computer processing of images of interference patterns (Newton's rings) obtained with a digital video camera is performed. The sequence of computer processing of the obtained images is described and the possibility of comparing the experimentally obtained data with theoretical models of the intensity distribution is shown. Computer processing of the images obtained with the digital video camera can be used in subsequent courses in the study of special disciplines, when performing research work, in processing measurement results and constructing models of physical phenomena.

Live electrooptic imaging with a low-coherence optical LO signal source for suppression of interference noises.

Reported in this paper is the first application, to our knowledge, of a low-coherence optical local oscillator signal source to the live electrooptic imaging (LEI) scheme, where high frequency electric field (EF) distributions are visualized in real time. A fiber-optic super luminescent diode (SLD) in conjunction with a LiNbO3 Mach-Zehnder modulator (MZM) was found to work well for the real-time imaging of gigahertz-range EF distributions with high suppression of interference pattern image noises (IPINs), which have long been a problem to be solved. While the SLD-based LEI system works up to the MZM bandwidth (10GHz), IPINs caused by microscopic defects in an electrooptic sensor appear, suggesting a limitation given by the SLD coherence length.

FIVQ algorithm for interference hyper-spectral image compression

Based on the improved vector quantization (IVQ) algorithm [1] which was proposed in 2012, this paper proposes a further improved vector quantization (FIVQ) algorithm for LASIS (Large Aperture Static Imaging Spectrometer) interference hyper-spectral image compression. To get better image quality, IVQ algorithm takes both the mean values and the VQ indices as the encoding rules. Although IVQ algorithm can improve both the bit rate and the image quality, it still can be further improved in order to get much lower bit rate for the LASIS interference pattern with the special optical characteristics based on the pushing and sweeping in LASIS imaging principle. In the proposed algorithm FIVQ, the neighborhood of the encoding blocks of the interference pattern image, which are using the mean value rules, will be checked whether they have the same mean value as the current processing block. Experiments show the proposed algorithm FIVQ can get lower bit rate compared to that of the IVQ algorithm for the LASIS interference hyper-spectral sequences.

Revealing buried information: Statistical processing techniques for ultracold-gas image analysis

The techniques of principal and independent component analysis are applied to images of ultracold atoms. As an illustrative example, we present the use of these model-independent methods to rapidly determine the differential phase of a BEC interferometer from large sets of images of interference patterns. These techniques have been useful in the calibration of the experiment and in the investigation of phase randomization. The details of the algorithms are provided.

Tunable, all-reflective spatial heterodyne spectrometer for broadband spectral line studies in the visible and near-ultraviolet

A spatial heterodyne spectrometer (SHS) is an interferometric device that combines high resolving power and a large input acceptance angle in a compact format suitable for use at small telescope focal planes and spacecraft for observations of faint, angularly extended emission-line sources. The primary limitation of SHS instruments has come from the spatial sampling of their output interference pattern image, which limits their use to a narrow bandpass. We describe the first-light results from a broadband all-reflective SHS that can be mechanically aligned to any heterodyne wavelength from 300 to 700 nm. Such an instrument can be extremely useful for the near simultaneous study of the brightness and line shapes of major atomic and molecular diagnostic emissions from extended astrophysical targets such as comets or planetary atmospheres. We discuss the results of this validation program and the potential improvements that could be used to expand and/or improve the broadband spectral response of the instrument.

Sonoelastographic imaging of interference patterns for estimation of shear velocity distribution in biomaterials

The authors have recently demonstrated the shear wave interference patterns created by two coherent vibration sources imaged with the vibration sonoelastography technique. If the two sources vibrate at slightly different frequencies omega and omega+deltaomega, respectively, the interference patterns move at an apparent velocity of (deltaomega/2omega)upsilon(shear), where upsilon(shear) is the shear wave speed. We name the moving interference patterns "crawling waves." In this paper, we extend the techniques to inspect biomaterials with nonuniform stiffness distributions. A relationship between the local crawling wave speed and the local shear wave velocity is derived. In addition, a modified technique is proposed whereby only one shear wave source propagates shear waves into the medium at the frequency omega. The ultrasound probe is externally vibrated at the frequency omega-deltaomega. The resulting field estimated by the ultrasound (US) scanner is proven to be an exact representation of the propagating shear wave field. The authors name the apparent wave motion "holography waves." Real-time video sequences of both types of waves are acquired on various inhomogeneous elastic media. The distribution of the crawling/holographic wave speeds are estimated. The estimated wave speeds correlate with the stiffness distributions.

Sonoelastographic imaging of interference patterns for estimation of the shear velocity of homogeneous biomaterials

The shear wave velocity is one of a few important parameters that characterize the mechanical properties of bio-materials. In this paper, two noninvasive methods are proposed to measure the shear velocity by inspecting the shear wave interference patterns. In one method, two shear wave sources are placed on the opposite two sides of a sample, driven by the identical sinusoidal signals. The shear waves from the two sources interact to create interference patterns, which are visualized by the vibration sonoelastography technique. The spacing between the pattern bands equals half of the shear wavelength. The shear velocity can be obtained by taking the product of the wavelength and the frequency. An alternative method is to drive the two vibration sources at slightly different frequencies. In this case, the interference patterns no longer remain stationary. It is proved that the apparent velocity of the moving patterns is proportional to the shear velocity in the medium. Since the apparent velocity of the patterns can be measured by analysing the video sequence, the shear velocity can be obtained thereafter. These approaches are validated by a conventional shear wave time-of-flight approach, and they are accurate within 4% on various homogeneous tissue-mimicking phantoms.

Interference-pattern image formation in an optical system with a random phase screen in the space-frequency plane

The process of interference-pattern image formation in an optical system with a random phase screen in the space-frequency plane is analyzed. It is shown that an optical system of this kind can function, under certain conditions, as a shearing interferometer, which determines the dependence of contrast of the average intensity fringes in the interference pattern image on the normalized correlation function of the random phase screen complex transmittance. The dependence of the fringe contrast on the pattern period and aperture of the field of view is established, as well as dependence of the optical transfer function of the system under study on spatial coherence of the light in the pupil of the system with the random phase screen.

On the interpretation of high resolution electron micrographs of macromolecules

Electron optical as well as light optical image formation depends upon an amplitude image and images of interference patterns from edge diffraction, granular phase effects, and crystal diffraction. Each of these interference images can be used to estimate the potential resolution of an electron microscope. Extended specimens, such as the macromolecule arginine decarboxylase, are examined on a supporting substrate and both make up the optical object. Each may contribute independently to the several image components in the final electron micrograph. The phase image granularity produced by the substrate cannot be distinguished from that produced by the specimen and therefore contains no information about it. The apparent sharpness of any picture is a function of the size of the elemental points that make it. Thus in high resolution electron micrographs, the smallest possible size of the limiting phase image granularity allows the maximum sharpness and the best resolution. This is demonstrated in electron micrographs of arginine decarboxylase with different sizes of the phase image granularity. The arginine decarboxylase image is composed of at least 5 subunits each with smooth edges and of nearly uniform density. The subunits have no demonstrable substructure.

Electron-microscopic observations of the interference patterns from crystal lattices

Evidence is presented to show that some striated images of suitably oriented single crystals of the dyes indanthrene scarlet R and olive T and of the phthalocyanine pigments are not direct crystal-lattice images but are images of interference patterns in object space. These result from the crystals behaving primarily as phase gratings. The patterns exhibit considerable fine structure as a function of the distance away from the object and the molecular plane spacing for any wavelength. These patterns may be predicted to a first approximation by combining interference fringes assumed to originate at or between the properly oriented molecular planes.