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Fiber Bragg grating (FBG) is the most widely used optical fiber sensor due to its compact size, high sensitivity, and easiness for multiplexing. Conventional FBGs fabricated by using an ultraviolet (UV) laser phase-mask method require the sensitization of the optical fiber and could not be used at high temperatures. Recently, the fabrication of FBGs by using a femtosecond laser has attracted extensive interests due to its excellent flexibility in creating FBGs array or special FBGs with complex spectra. The femtosecond laser could also be used for inscribing various FBGs on almost all fiber types, even fibers without any photosensitivity. Such femtosecond-laser-induced FBGs exhibit excellent thermal stability, which is suitable for sensing in harsh environment. In this review, we present the historical developments and recent advances in the fabrication technologies and sensing applications of femtosecond-laser-inscribed FBGs. Firstly, the mechanism of femtosecond-laser-induced material modification is introduced. And then, three different fabrication technologies, i.e., femtosecond laser phase mask technology, femtosecond laser holographic interferometry, and femtosecond laser direct writing technology, are discussed. Finally, the advances in high-temperature sensing applications and vector bending sensing applications of various femtosecond-laser-inscribed FBGs are summarized. Such femtosecond-laser-inscribed FBGs are promising in many industrial areas, such as aerospace vehicles, nuclear plants, oil and gas explorations, and advanced robotics in harsh environments.

The aim of this study was to quantify vibrations and their influence on visual acuity. The study consisted of two parts, laboratory and clinical. Time-averaged holographic interferometry (TAHI) method was used in laboratory for measuring the amplitude of tooth vibrations induced by dental handpiece. The amplitudes of tooth vibrations were measured for the three diameters and three speeds. The larger diameter coupled with increasing speed resulted in greater vibration amplitudes, whereby a maximum amplitude of less than one micrometer was detected. For quantifying the natural visual acuity for the corresponding tooth vibrations, we have used the clinical condition approach with miniaturized Snellen optotype as an assessing tool. Central visual acuity did not display variance in visual acuity at rest or under load. Results indicate that the vibrations induced during cavity preparation are not sufficient to negatively affect visual acuity of dentists.

In this paper, we have studied the deformation of cylindrical nanostructured silica aerogels prepared with methyltrimithoxysilane (MTMS) precursor. Two beam phase-shifting digital holographic interferometry (PSDHI) is applied along with a two-beam illumination technique to study in-plane displacements. To obtain the aerogels with different densities, the MeOH/MTMS molar ratio was systematically increased from the value 20 to 26. The cylindrical aerogels are loaded with various loads from the top surface. Phase shifted holograms of silica aerogels with varying densities, with and without deformation, are recorded with two beam illumination by CCD camera. Fresnel Diffraction integral is used to reconstruct the complex amplitude of aerogel samples. For in-plane displacements, phase distribution in deformed aerogels is determined by measuring the change in the two-phase distributions. The patterns corresponding to the phase distribution of aerogels for different loads and densities are recorded. It has been observed that the deformation of silica aerogels reduces by the value 0.02058 cm to 0.0017 cm, with an increase in bulk density 0.01742 gm/cc to 0.1952 gm/cc. The elastic behavior of aerogels has been explained under various loads by considering the phase distribution patterns and condensation reaction.

In semiconductor device manufacturing, optical overlay metrology measures pattern placement between two layers in a chip with sub-nm precision. Continuous improvements in overlay metrology are needed to keep up with shrinking device dimensions in modern chips. We present first overlay metrology results using a novel off-axis dark-field digital holographic microscopy concept that acquires multiple holograms in parallel by angular multiplexing. We show that this concept reduces the impact of source intensity fluctuations on the noise in the measured overlay. With our setup we achieved an overlay reproducibility of 0.13 nm and measurements on overlay targets with known programmed overlay values showed good linearity of R2= 0.9993. Our data show potential for significant improvement and that digital holographic microscopy is a promising technique for future overlay metrology tools.

A modification of the method of digital holographic interferometry for the determination of deformations of an object with a diffuse surface by comparing two complex wavefronts reflected from the object at its two different states is considered. The difference of the proposed method with classical digital holography methods is that digital holograms by which the images are reconstructed have complex values determined by the phase shift method (‘‘complex’’ hologram), while classical digital holograms have only real values. Besides, digital holograms are reconstructed with allowance for inhomogeneity of the reference beam, which improves the reconstruction quality. For this purpose, a tunable neutral optical filter is introduced into the reference arm of the optical scheme of the interferometer. The method is verified experimentally.

This paper presents the results of experimental studies and digital methods for recording of holograms using spatial light modulators. The use of holographic interference methods for measuring nanoscale irregularities is described for the case of a nanostep (70 nm in height and 30 $$\mu$$ m in width). Examples are given of the method of increased sensitivity for nanostep measurements and the method of hooks using a digital technique. Correction of internal system distortions in the interferometer has been shown to be a workable method. The holographic interference methods with digital processing of holograms allows the sensitivity of interferograms to be increased without loss of basic information about the object and without increasing the measurement accuracy.

In this paper, we propose a two-to-one deep learning (DL) framework for three- wavelength phase-shifting interferometry. The interferograms at two different wavelengths are used as the input of the proposed hybrid-net, and the interferogram of the third wavelength is used as the output. Using the advantages of the hybrid learning network, the interferogram of the third wavelength can be obtained accurately. Finally, the three-wavelength phase-shifting interferometry is realized. Compared with the previous DL-based dual-wavelength interferometry (DWI), the proposed method can further improve the measurement range of the sample without changing the DWI system. Especially for the independent step sample, the problem of limited measurement range is solved due to the input of auxiliary information. More importantly, the third wavelength can be set freely according to the measurement requirements, which is no longer limited by the actual laser and can provide more measuring ruler for phase measurement. Both experimental results and simulation analysis demonstrate the proposed method in the feasibility and the performance in improving the measurement range.

Based on the hologram inpainting via a two-stage Generative Adversarial Network (GAN), we present a precise phase aberration compensation method in digital holographic microscopy (DHM). In the proposed methodology, the interference fringes of the sample area in the hologram are firstly removed by the background segmentation via edge detection and morphological image processing. The vacancy area is then inpainted with the fringes generated by a deep learning algorithm. The image inpainting finally results in a sample-free reference hologram containing the total aberration of the system. The phase aberrations could be deleted by subtracting the unwrapped phase of the sample-free hologram from our inpainting network results, in no need of any complex spectrum centering procedure, prior knowledge of the system, or manual intervention. With a full and proper training of the two-stage GAN, our approach can robustly realize a distinct phase mapping, which overcomes the drawbacks of multiple iterations, noise interference or limited field of view in the recent methods using self-extension, Zernike polynomials fitting (ZPF) or geometrical transformations. The validity of the proposed procedure is confirmed by measuring the surface of preprocessed silicon wafer with a Michelson interferometer digital holographic inspection platform. The results of our experiment indicate the viability and accuracy of the presented method. Additionally, this work can pave the way for the evaluation of new applications of GAN in DHM.

We apply a novel laser diagnostic technique — Resonant Holographic Interferometry (RHI) to measure the concentration of hydroxyl radical (∼2000 ppm) in a co-flow diffusion flame of diluted hydrogen and air stabilized on a Wolfhard-Parkerburner. This methodology is based upon the dispersion of light of frequency close to an electronic transition of a target molecule. The two-color setup utilized in RHI provides a two-dimensional distribution of the target species concentration and quantitative information can be obtained from the interferogram without requiring any calibration. To provide independent flame data for comparison, a two-dimensional numerical simulation was performed taking into account the effects of detailed chemical kinetics and transport phenomena. In spite of a number of simplifying assumptions made in the simulation, computational and experimental results are in good agreement with respect to the magnitude and width of the region where OH is found. We do observe a difference of approximately 1 mm in the flame position due to the simplifying assumptions made in the simulation. The comparison between the experimental and numerical results clearly demonstrated the potential of RHI in flame diagnostics.

In this paper, we discuss the quality of holograms generated by two-femtosecond laser pulses of two different colors based on the interference and holography processes by the calculation of the modulation depth. Some numerical simulations for the two Higher-order sh- and ch-Gaussian temporal profiles (shnGTP and chnGTP) are investigated. These simulations show that, when two lasers with a very large frequency detuning are used, the considered profiles exhibit more precise results and give new frequency detuning zones that allow a very significant value of the modulation depth to fringe contrast (MDFC) ratio to obtain the best hologram compared to Gaussian profile. The proposed theory will be a good basis for the development of some new experiments on holographic interferometry and it will certainly be very useful for the specialists using these femtosecond laser pulses.

This report proposes a method for measuring object phase changes in real time. This new method utilises photorefractive holographic interferometry to form a hologram that contains an object phase variation and extracts this phase variation using a fringe analysis method involving two-step generalized phase-shifting interferometry. Compared to traditional methods, instead of using four holograms to achieve phase reconstruction, only two holograms are needed to record the proposed algorithm, and this approach is immune to phase-shifting errors arising from various sources. This algorithm may be useful for designing a detecting system for the real-time measurement of object variations.

Residual stress levels induced during the process are one of the more relevant characteristics of thermal spray coatings. Therefore, there are different techniques, such as the x-ray diffractometry or the classical micro hole drilling and milling method, to analyse and optimize the thermal spray coating process in order to obtain a desired level of residual stresses on coatings. The state of the art of the new developed non-contact, quasi non-destructive residual stress analysis method is presented. The material removal is based on laser ablation and complex ablation geometries are possible by using a spatial light modulator (SLM) for beam conditioning. 3D deformations on the specimen surface are measured in the nanoscale range by high-resolution digital holographic interferometry. Numerical procedures using the finite differences method are performed in order to calculate the shape geometry and the calibration curves required for the residual stress calculation from the measured 3D displacements, coating-substrate material combination and the ablation geometry. Experimental results on thermal spray coatings are presented and discussed with comparative measurements by the hole-drilling method. The potentials and difficulties of the method are discussed.

In this article, we have used double exposure digital holographic interferometry (DEDHI) technique for surface deformation study and hologram recording during synthesis of the Bi2Te3 thin films by electrodeposition method. The synthesized Bi2Te3 thin films were characterized structural, morphological, electrochemical, wettability and surface deformation study. Further the holograms are recorded during the electrodeposition process by varying the concentration of electrolyte. From the recorded fringes the stress, deposited mass and thickness have been calculated. It is observed that the fringe width, mass of deposited thin films, and stress to substrate changes with the concentration of electrolyte. The DEDHI technique is found more reliable for thickness measurement in electrodeposition process. The EIS study confirms that the deposited material is highly conducting.

Problems associated with changes in the shape and size of red blood cells in patients with atherosclerosis are considered. The applicability of physical optics techniques (in particular, holography) for the examination of red blood cells is discussed. An interferographic technique for analyzing the shape of red blood cells and estimating quantitatively their cross section and size is suggested. Experimental data on the comparative characteristics of red blood cells in normal and pathological states are presented.

The work is devoted to an experimental study of the digital holographic interferometry method for flaw detection of optical fiber preforms (preforms). Flaw detection of the production of optical fibers plays an important role. This article describes the process of digital holographic shooting and image processing of holograms. Based on the Leith–Upatnieks optical scheme, a holographic interferometer scheme has been developed, in which a hologram is recorded directly on a CCD array. A series of experiments on holographic interferometry of flaw detection of optical fiber blanks has been carried out. Holographic interferometry allows you to record objects in different states. Based on the experimental data, the possibilities of the method are studied and the possibility of its use is justified, its advantages over other analyzers of optical fiber preforms are also presented.

Accounting for nonlinear elasticity of modern materials becomes very important due to their rising operation at high dynamic loads. Generation of strain solitary waves (solitons for brevity) is one of the processes of interest, however details of a transformation of an initial impact into the soliton are not completely clear yet. In this paper we demonstrate the advantages of a combination of classical and digital holographic recording for investigation of the early stages of soliton formation. While classical realization of holographic interferometry allowed for visualizing sharp phase gradients representing, in particular, shock waves, digital recording supplied quantitative data on parameters of smoother disturbances evolving in the course of soliton formation. The applied holographic techniques allowed us to monitor the entire process of soliton formation, to visualize intermediate wave patterns and to obtain quantitative data on the resulting soliton.

Photonic crystals (PCs) are artificial micro-nano structures consisting of different materials periodically arranged. They can be divided into two categories: simple and compound PCs. They have broad application prospects in many fields such as micro-nano photonics and optoelectronic integration. Laser holography method is an important method for fabricating PCs. In this work, a theoretical study on the production of compound PCs by multi-beam holographic interferometry is carried out, and a four-beam configuration with a certain symmetry is designed to produce two-dimensional compound PCs. Simulations based on MATLAB program are in good agreement with the theoretical analysis. The evolution of the unitcell and contrast of the compound PC under different polarization combinations of a single beam and double beams are further studied. The results indicate that the polarization affects the unitcell of the PC sensitively. Under different polarization combinations, a variety of rich unitcell shapes of compound PCs such as elliptical-like rods and wave-like stripes are obtained. When all interfering beams are linearly polarized within the xoy plane, the compound PC has the best contrast. These above results hold promise for the design and fabrication of compound PCs with various unitcell shapes.

Phase-derived parameters and time autocorrelation functions were used to analyze the behavior of murine B16 cells exposed to different amplitudes of electroporation pulses. Cells were observed using an off-axis digital holographic microscope equipped with a fast camera. Series of quantitative phase images of cells were reconstructed and further processed using MATLAB codes. Projected area, dry mass density, and entropy proved to be predictors for permeabilized cells that swell or collapse. Autocorrelation functions of phase fluctuations in different regions of the cell showed a good correlation with the local effectiveness of permeabilization.

Digital holographic microscopy (DHM) is a technique that has high potential for analyzing biological samples and has been successfully applied to the study of cells and cell lines providing information about important parameters such as refractive index, morphology, and dry mass, among others; it has also found applicability to study the effects of therapeutic treatments. Finding the size and shape of cells is important since they tend to change in the presence of some pathologies. In this research work, we obtain the morphology thickness and refractive index of the A375 melanoma cell line through a slight tilting of the cell in a DHM setup. Further, the development of a novel mathematical expression based on this tilt and in the optical phase difference is presented. We show images of melanoma cells with the refractive index information included, and their morphology thickness as rendered from the holographic phase maps recorded with DHM.

Time average digital holography under random excitation or square wave excitation is established as an on-site non-destructive testing tool for defect detection in large metallic and composite sandwich structures due to its high sensitivity, single exposure interferogram, and fast inspection capability. However, extensive calibration studies are necessary to corroborate the defect type and defect size with the excitation frequency range and excitation magnitude. In this paper, a method to simulate a time average digital holographic fringe pattern under random excitation is proposed with the idea to minimize the number of calibration experiments and also for better evaluation of the size and type of defect. The proposed method circumvents the requirement for a closed form expression for the complex characteristic fringe function for time average interferometry under random excitation. The computed fringe pattern is illustratively compared with an experimental time average digital holographic fringe pattern.

Precise surgical procedures such as deep brain tumor ablation may benefit from intra-operative image guidance using magnetic resonance imaging (MRI). However, the MRI’s strong magnetic fields and constrained space pose the need for robotic devices to assist the surgeon. Piezoelectric motors are often used to actuate these robots. The piezoelectric resonant motor (PRM) is a class of such motors that consist of a bonded piezoelectric ring stator and a frictionally coupled rotor. Steady-state excitation at certain frequencies leads to specific mode shapes on the stator with surface waves having both in-plane and out-of-plane displacement components that cause the coupled rotor to spin. High-speed digital holography (HDH) can be used to measure time variant displacements with nanometer and microsecond resolution. We present initial measurements acquired at 67 k frame per second (fps) of two custom-designed plastic stator components operating at drive frequencies of 6.788 kHz and 6.980 kHz, respectively. Circumferential motion of the traveling surface waves with out-of-plane peak-to-peak displacement of approximately 100 nm peak-to-peak amplitude and a settling time of 2.99 ms was observed. Results demonstrate that plastic stators may be a promising alternative to metallic stators for use in the MRI environment.

International audience; JPEG Pleno is a standardization framework addressing the compression and signaling of plenoptic modalities. While the standardization of solutions to handle light field content is currently reaching its final stage, the Joint Photographic Experts Group (JPEG) committee is now preparing for the standardization of solutions targeting point cloud and holographic modalities. This paper addresses the challenges related to the standardization of compression technologies for holographic content and associated test methodologies.

Digital holographic Interferometry is a contactless, fast and precise technique which can be utilized for study of dynamic processes. In the present work temperature profile of kerosene lamp flame has been measured using digital holographic interferometry without unwrapping of phase which substantially reduces effort and time of computation. The measured temperature through this technique is found to be in good agreement with the temperature value achieved through thermocouple.

Digital acousto-optic holography uses sound wave field interacted with interested object to modulate laser beam to generate an optical digital hologram. A numerical reconstruction of the digital hologram is carried out to reproduce the object information. This technology is able to image the interior structure of non-transparent object with high precision.

A new method of performing holography and holographic interferometry is proposed, whereby the film does not have to be developed in the manner that traditional film needs to be developed. This is done by implementing a photopolymer film, a film that develops via a reaction diffusion-driven photo-polymerization process. The utilization of photopolymer film rapidly simplifies the process of performing holography and holographic interferometry as it removes the wet development process that was previously required in holography.

Scattering in biological tissues is a major barrier for in vivo optical imaging. The resulting distortion can be corrected by shaping the excitation wavefront to redirect power into a single point in the imaging plane, but finding the optimal correction pattern is nontrivial. Several strategies have been developed to this end, including indirect wavefront sensing techniques which aim to redirect light from a subset of the scattered modes into the focus using an iterative approach. Two indirect wavefront sensing techniques, termed IMPACT and F-SHARP, have recently enabled impressive in-vivo imaging results in various tissues including the mouse brain [1] , [2] . However, further development is required to increase the imaging depth and match the persistence times of many living tissues.

Fringe projection profilometry and off-axis digital holographic interferometry are two techniques commonly used for non-contact optical surface measurement and movement tracking; however, they can be difficult to implement due to the complex software involved. To address this, we introduce a MATLAB-based graphical application that performs phase map retrieval for these techniques. Designed with a pipeline-based architecture, PhaseWare assembles the most commonly used algorithms and includes pre-processing (cropping, DC offset removal, filtering), fringe and phase extraction (hologram reconstruction, phase demodulation), and post-processing (denoising, masking, phase unwrapping, background removal, image enhancement).

The materials currently used in modern structures do dramatically change their mechanical properties under the influence of low operating temperatures. One of the factors affecting the breakdown of various structural elements at low temperatures, is the placement of the stress concentrations. The existing analytical design schemes cannot always correctly take into account the material mechanical properties changes caused by the temperature decrease. In the present work we consider the method of contact holographic interferometry, which made it possible to efficiently determine surface displacements and strains at the temperature of –50 °C. The contact holographic interferometer is presented as an assembly of the object surface section and holographic plate in an immediate vicinity to the object. This technique is used to determine in-plane and out-of-plane displacements of tested object. If a hologram is recorded at metallized grating surface it restores information peculiar to some optical methods: holographic interferometry, speckle photography, holographic moire and mirror-optical method. For the interpretation of interference patterns new simple analytical equations are obtained. Contact holographic interferometers are used effectively to solve some elasto-plastic deformation measurement problems of isotropic and polycristalline materials. It is specially designed to permit the accurate measurement of the in-plane component of strain in the immediate vicinity of stress concentrators in plates.

A quick and accurate way for testing collimation of laser beams is desired to achieve correct results in many optical instruments. Laser beam collimation is generally performed using glass wedge plates. For better accuracy, a set of wedge plates of different thicknesses and wedge angles are required to acquire first-hand visual information about collimation of laser beams having a wide range of diameters. Use of a compact holographic lateral shearing interferometer (HLSI) is demonstrated for collimation testing of laser beams having different beam diameters. The interferometer uses two holographic optical elements (HOEs) with provision of variable tilt in one of the HOEs to maintain a constant number of fringes in the interferograms for different diameters of input test beams. An angle of rotation of interference fringes from a reference position is measured to be 0.9 deg for a test beam of diameter 2 mm and 16 deg for the test beam of diameter 35 mm. We experimentally demonstrated range of optimum number of interference fringes in the interferogram for visual inspection of the collimation state of the test beam. Thus the proposed interferometer could replace a set of wedge plates generally required for collimation testing of beams having different diameters. The functioning of the interferometer for collimation testing of beams having different diameters is discussed and experimentally demonstrated.

The method of holographic interferometry is based on observation in real-time value of the change of the refractive index of solution during and after its illumination with laser light. This method was used to compare the effects of laser illumination on nanosystems containing polymer (in nonionic and anionic form), Au nanoparticles (AuNPs), and photosensitizer Chlorine e6 (Ce6) at variation of these components. The size distribution of scattering objects in the nanosystems in aqueous solution was determined by dynamic light scattering method. It was shown that under illumination with light the variation of the refractive index is localized mostly near the laser beam transmission region for all nanosystems containing AuNPs. For these systems, thermal diffusion into the non-illuminated volume was practically absent. The presence in the nanosystems Ce6 didn’t change the behavior of nanosystems. However, there was heat propagation after the light absorption to the top area of the cuvette for system containing only polymer and Ce6. This might indicate heating of the solvent.

Today digital holographic interferometry (DHI) is considered a modern full-field non-destructive technique that allows generating 3D quantitative data of a wide variety of specimens. There are diverse optical setups for DHI that enable the study of specimens in static and dynamic conditions: it is a viable alternative to characterize a wide diversity of parameters in the micro and macro world by conducting repeatable, reliable and accurate measurements that render specimen data, e.g., displacements, shape, spatial dimensions, physiological conditions, refractive indices, and vibration responses. This paper presents a review and progress on the most significant topics, contributions and applications involving DHI for the study of different specimens such as: cells, bio tissues, grains, insects, and nano-structures. For most of the research work involving macro and micro specimens the wave-like source used in the measurements were photons from a laser, while the studies carried out in the nano regime used the wave-like nature of the electron.

Birefringence is an important optical property of anisotropic materials arising from anisotropies of tissue microstructures. Birefringence parameters have been found to be important to understand optical anisotropic architecture of many materials and polarization imaging has been applied in many researches in the field of biology and medicine. Here, we propose a scheme to miniaturize a double-channel polarization holographic interferometer optics to create a polarization holographic microscope slide (P-HMS) suitable for integrating with microfluidic lab-on-a-chip (LoC) systems. Based on the P-HMS combined with a simple reconstruction algorithm described in the paper, we can not only simultaneously realize holographic imaging of two orthogonal polarization components of dynamic samples in a microfluidic channel but also quantitative measurement of 2D birefringence information, both including the birefringence phase retardation and optic-axis orientation. This chip interferometer allows for off-axis double-channel polarization digital holographic recording using only a single illumination beam without need of any beam splitter or mirror. Its quasi-common path configuration and self-aligned design also make it tolerant to vibrations and misalignment. This work about the P-HMS could play a positive role in promoting the application of birefringence imaging in microfluidic LoC technology.

In this paper, a volume phase holographic optical element based digital holographic interferometer is designed and used for quantitative phase imaging of biological cells [white blood cells, red blood cells, platelets, and Staphylococcus aureus (S. aureus) bacteria cells]. The experimental results reveal that sharp images of the S. aureus bacteria cells of the order of ∼ 1 µ m can be clearly seen. The volume phase holographic grating will remove the stray light from the system reaching toward the grating and will minimize the coherent noise (speckle noise). This will improve the sharpness in the image reconstructed from the recorded digital hologram.

Ionizing radiations are being widely used in a variety of medical and industrial applications in which the exact determination of the absorbed dose distribution is of crucial importance. Digital holographic interferometry (DHI) is an optical technique that uses lasers to produce fringe patterns which must be reconstructed to measure the physical quantities of interest. The DHI technique is sensitive to noise that makes it difficult to adopt this technique for practically measuring the absorbed dose. In this paper, a new approach to DHI has been developed based on using fringe contouring, polynomial phase fitting and inverse Abel transformation, to reconstruct the three-dimensional dose distribution in noisy conditions. In order to assess the feasibility of this approach in measuring the absorbed dose distributions in noisy conditions, the whole approach is modeled for high energy electrons. It is shown that the three-dimensional dose distribution inside the absorbing medium can be obtained with good accuracy even in the presence of considerable amounts of deliberately added noise to the holograms.

Materials research in holography has attracted significant interest and is aiming at facilitating the development of light-weight, cost effective optical devices. Among the most researched materials, photopolymers are playing an indispensable role due to many advantages they offer such as their self-processing nature, high spectral sensitivity and relatively inexpensive mass production cost; hence they are extensively studied to make possible the applications of holographic technology such as holographic interferometry [1], holographic solar concentrators [2], holographic data storage [3] and holographic sensors [4]. Additionally photopolymers can be easily functionalised utilising different methods; one approach, previously proven to be successful, is to dope the host polymer with nanoparticles (NP’s) [4].

Noise suppression is one of the most important tasks in imaging through inhomogeneous mediums. Here, we proposed a denoising approach based on compressive in-line holography for imaging through an inhomogeneous medium. A reference-beam-free system with a low-cost continuous-wave laser is presented. The suppression against the noise, which is brought by the scattering photons, is presented in simulations using the proposed algorithm. The noise immunity is demonstrated in lensless imaging behind a random phase mask with an optical depth of 1.42 by single exposure, as well as behind a ground glass with an optical depth of 6.38 by multiple exposures.

International audience; This paper presents a deep-learning-based algorithm dedicated to the processing of speckle noise in phase measurements in digital holographic interferometry. The deep learning architecture is trained with phase fringe patterns including faithful speckle noise, having non-Gaussian statistics and non-stationary property, and exhibiting spatial correlation length. The performances of the speckle de-noiser are estimated with metrics, and the proposed approach exhibits state-of-the-art results. In order to train the network to de-noise phase fringe patterns, a database is constituted with a set of noise-free and speckled phase data. The algorithm is applied to de-noising experimental data from wide-field digital holographic vibrometry. Comparison with the state-of-the-art algorithm confirms the achieved performance.

Acousto-optic deflectors (AODs) allow the creation of multiple optical traps by time-sharing, that is, by rapidly cycling the laser focus between designated spatial locations. The traps thus formed are not permanent. In this Letter, we successfully demonstrate the creation of multiple and permanent traps by means of AODs driven by specially encoded radio frequency signals. The generation of complex acoustic signals allows us to treat such devices as super-fast spatial light modulators. Using this technique, it is possible to generate several static optical trap arrays and switch them at kilohertz (kHz) rates, allowing independent control of each trap group. Additionally, we discuss the compatibility of this method with precise force and position measurements, and the improvement in their frequency bandwidth compared to time-sharing optical tweezers, especially when many objects are trapped.

Spatial phase scanning is introduced for wide area acquisition of quantitative phase microscopy. Both phase shifting and wide area acquisition is achieved by scaning the object across the tilted reference phase field of holographic interferometer.

We introduce a holographic imaging concept that is conditioned on photonic entanglement. We show that entanglement-encoded phase images can be retrieved through dynamic phase disorder and in the presence of classical noise, with practical advantage over classical holography.

Here we design a compact, portable and cost-effective holographic microscope based on the concept of holographic microscope slide. We developed a wavefront division holographic interferometer deployable for in-situ environmental monitoring and point-of care diagnostics.

Photoconducting polymeric composites (PPCs) containing nanosized organic or inorganic dopants (dyes and their aggregates, nanoparticles of inorganic semiconductors) are already employed as photoactive media in OLEDs, in photoelectric solar energy converters, in optoelectronic elements, and in electrography and holography. The final application is the subject of this chapter. The basic requirements of holographic recording media (HRM) for the photothermoplastic (PTP) recording technique are considered. Features of the PTP recoding are described and the main demands to HRM are formulated: low electric conductivity, high photoconductivity at the light wavelength of the used laser, good film-forming, and optical and thermoplastic properties. The mechanisms of PPC photoconductivity are studied, including photogeneration, recombination, transport, and capture of nonequilibrium charge carriers. These mechanisms are particular to the organic and inorganic disordered nanomaterials with photosemiconducting properties and differ from the mechanisms in crystal materials due to the absence of long- and short-distance orders in the disordered nanomaterials. Possibilities for the development of new polymeric bases for PPC are discussed to provide a realization of the requirements for HRM. A comparison of the photophysical and information properties of HRM based on cooligomers with linear and radial structure is fulfilled similarly to investigations into the influence of nanoparticle size on the photophysical properties of semiconductor materials. The potentials for the improvement of the information characteristics of HRM is considered with concrete examples. “Wet” development of holograms is not required in the PTP holographic recording technique. Thus, this technique can be used not only in visual holography, but mainly, and more effectively, in holographic interferometry for nondestructive quality control, for detection of the residual stresses in metallic units, and for measurements of refractive index, etc. Concrete examples of HRM and devices for their application are described. This information is not only of scientific interest for widening knowledge about the photo processes in PPC, but is also useful for practical applications of photosemiconducting nanomaterials for quality control of the means of production and products, for prevention breakage, crashes, and catastrophes.

Holographic interferometry is one of the most useful applications of holography. It allows measurement of the phase of an object or a scene, which evolves over time. In particular, it can measure the phase variations resulting from surface displacements or deformations of solids, the shape of objects or variations of refractive index in transparent media, to name of few. At the beginning of holography history, the tremendous potentialities of holographic interferometry were immediately recognized for industrial applications. This generated a lot of researches and developments, which encompasses the ways of recording holograms (through photosensitive materials and later through electronic recording) and the way to interpret the fringe pattern returned by the methods in a variety of situations. This chapter aims at reviewing the different periods of history of holographic interferometry, from the pioneering experiments to the latest achievements, some having led to marketed systems with commercial successes.

This chapter presents an overview of the field of holography and is a prerequisite to the rest of the book. We are taking the approach of introducing holography by the viewpoint of diffraction optics. We will start by looking at the definition and properties of the simplest holograms: diffraction gratings. There is a lot to learn, and intuition to acquire, by understanding how these simple structures interact with light. We will then generalize the concept of diffraction to any pattern by introducing the scalar theory of diffraction. This theory allows to compute hologram for any image and location. Once these mathematic foundations are laid down, we will see the different experimental configurations to record, use, and take advantage of holograms.

We present the results of a study of milk as a complex biological fluid. The simultaneous occurrence of both direct and reverse sedimentation associated, respectively, with the protein and fat components of milk is demonstrated. Digital holographic interferometry enables the determination of the spatial and temporal changes in the refractive index of the suspension under study caused by fractionation processes with an accuracy of 10–6, which exceeds the capabilities of other research methods. The results can be used to create a mathematical model of biological fluid fractionation processes and to develop physical models (phantoms) of such systems.

The article presents a method to estimate multiple phases from a single moire fringe pattern in digital holographic interferometry. The proposed method relies on analysing the holographic moire signal using subspace rotational invariance approach and offers feasibility for single shot multi-component estimation without multiple frames or spatial carrier and high performance against severe noise. Simulation and experimental results demonstrate the applicability of the proposed method.

Modern methods of laser photonics, which make it possible to measure the dynamics of micro-deformations of volumetric objects without contact and with high sensitivity, find increasing application in a wide variety of fields. Particularly attractive is the use of such a delicate, non-perturbing technique in medicine. The article reports on experiments using laser photonics methods in dental implantology, which allowed to give practical medical recommendations. In the work, a study was made of the possibilities of holographic and speckle interferometry methods for measuring the deformation of the jaw bone tissue with a step-by-step installation of cylindrical and conical mini implants. The possibility of determining the relaxation time of deformations after the installation of mini implants was demonstrated. The purpose of this work is to justify the possibility and feasibility of using laser photonics to solve this medical problem.

A combination of digital holographic interferometry (DHI) and digital speckle photography (DSP) allows in-plane and out-of-plane displacement measurement between two states of an object. The former can be determined by correlating the two speckle patterns whereas the latter is given by the phase difference obtained from DHI. We show that the amplitude of numerically reconstructed object wavefront obtained from Fresnel in-line digital holography (DH), in combination with phase shifting techniques, can be used as speckle patterns in DSP. The accuracy of in-plane measurement is improved after correcting the phase errors induced by reference wave during reconstruction process. Furthermore, unlike conventional imaging system, Fresnel DH offers the possibility to resize the pixel size of speckle patterns situated on the reconstruction plane under the same optical configuration simply by zero-padding the hologram. The flexibility of speckle size adjustment in Fresnel DH ensures the accuracy of estimation result using DSP.