Holographic Sensor Research Articles

Creation of multimodal digital twins with reflexive AGI multilogic and multisensory

Reflexive AGI multilogic, multimodality and multisensors are the basis for the multidisciplinary development of intelligent digital twins. Multimodality is implemented in several formats: text, image, speech, formulas, etc. Multilogic is implemented according to several rules or methods or ways of working with knowledge and data, and the criterion for selecting the best result from all implementations. AGI multilogic carries out judgment, understanding, perception, comparison, analysis, choice, etc. Understanding is realized using the technology of unified objectification of the ontology of subject areas for the implementation of specific activities. Multisensor systems are combined groups of electro-optical, spectroscopic and holographic sensors, and combined series of sensors, such as a thermal imager, color camera, low-light camera, laser rangefinder, laser designator, laser, pointer-illuminator and others. Multisensory systems help monitor the psyche and performance of a person at the level of medical indicators of his physical condition in the process of joint activities with digital twins. Multimodal digital twin with AGI multilogic and multisensory is good human assistant in many areas of activity.

Theoretical Aspects of Creating Multimodal Digital Twins with AGI Multilogic and Multisensory

AGI multilogic, multimodality and multisensors are the basis for the multidisciplinary development of intelligent digital twins. Multimodality is implemented in several formats: text, image, speech, formulas, etc. Multilogic is implemented according to several rules or methods or ways of working with knowledge and data, and the criterion for selecting the best result from all implementations. AGI multilogic carries out judgment, understanding, perception, comparison, analysis, choice, etc. Understanding is realized using the technology of unified objectification of the ontology of subject areas for the implementation of specific activities. Multisensor systems are combined groups of electro-optical, spectroscopic and holographic sensors, and combined series of sensors, such as a thermal imager, color camera, low-light camera, laser rangefinder, laser designator, laser, pointer-illuminator and others. Multisensory systems help monitor the psyche and performance of a person at the level of medical indicators of his physical condition in the process of joint activities with digital twins. Multimodal digital twin with AGI multilogic and multisensory is good human assistant in many areas of activity.

Storage Optimization of Transmission Holographic Gratings in Photohydrogels.

The development and optimization of holographic materials represent a great challenge today. These materials must be synthesized according to the characteristics that are desirable in photonic devices whose application is the object of investigation. In certain holographic sensors and biosensors, it is essential that the recording material be stable in liquid media. Furthermore, the holographic gratings stored in them must have temporal and structural stability, so that they can act as transducers of the analytical signal. Therefore, it is essential to optimize its storage in terms of the chemical composition of the material and the optical parameters of recording. This work focuses on the study of the storage optimization of unslanted transmission volume phase holograms in photohydrogels based on acrylamide and N,N'-methylenebis(acrylamide). Hydrogel matrices, also composed of acrylamide and N,N'-methylenebis(acrylamide), with different degrees of cross-linking were used and analyzed by scanning electron microscopy and UV-visible spectroscopy. The best results in terms of diffraction efficiency were reached for hydrogel matrices with an acrylamide/N,N'-methylenebis(acrylamide) molar ratio between 19.9 and 26. This relationship was also optimized in the incubator solution used to incorporate the components necessary for the formation of the holograms in the hydrogel matrices. The maximum diffraction efficiency, about 35%, was achieved when using an incubation solution with an acrylamide/N,N'-methylenebis(acrylamide) molar ratio of 4.35. The influence of the physical thickness of the hydrogel layers, the intensity, and the exposure time on the diffraction efficiency was also investigated and optimized. In addition, the behavior of the hologram was analyzed after a washing stage with PBST. A simple model that considered the effects of bending and attenuation of holographic gratings was proposed and used to obtain the optical parameters of the holograms.

Lensless multi-spectral holographic interferometry for optical inspection

We explore the principles, implementation details, and performance characteristics of a lensless multi-spectral digital holographic sensor and demonstrate its potential for quality assurance in semiconductor manufacturing. The method is based on capturing multi-spectral digital holograms, which are subsequently utilized to evaluate the shape of a reflective test object. It allows for a compact setup satisfying high demands regarding robustness against mechanical vibrations and thus overcomes limitations associated with conventional optical inspection setups associated with lens-based white light interferometry. Additionally, the tunable laser source enhances the versatility of the system and enables adaptation to various sample characteristics. Experimental results based on a wafer test specimen demonstrate the effectiveness of the method. The axial resolution of the sensor is ±2.5 nm, corresponding to 1σ.

Comparing thin and volume regimes of analog holograms for wavefront sensing.

Two analog holographic wavefront sensors, for measurement of defocus, have been fabricated as both thin and volume phase transmission holograms in a self-developing photopolymer. This represents the first reported direct comparison of hologram regimes when designed for wavefront sensing. An analysis of the effect of crosstalk in the presence of one other aberration mode (astigmatism X (0/90°), coma X (horizontal), and primary spherical aberration) was carried out with each version of the sensor. The performance of thin and volume analog holographic wavefront sensors was characterized under emulated conditions associated with moderate atmospheric turbulence.

Optically accessible gas exposure apparatus for testing and characterization of holographic gas sensors

Holographic gas sensors are of great interest due to their widespread applicability and potential for high sensitivity, fast response, immunity to electromagnetic interference, and compact and lightweight nature. For effective design and development of holographic gas sensors, it is essential to have a reliable and safe gas exposure system allowing for optical access for testing purposes. Here, the design and operation of a custom gas exposure apparatus for the performance evaluation of holographic grating-based gas sensors within a research laboratory setting is presented. The apparatus enables the real-time measurement of analyte-induced changes in key holographic grating parameters: grating diffraction efficiency and reconstruction wavelength. A demonstration of the capabilities of the optically accessible apparatus to evaluate sensor response time, sensitivity to different volatile organic compound analytes, and response to cyclical gas exposure is presented. The AutoCAD designs, as well as the material and equipment specifications for the custom apparatus, are provided to facilitate reproduction of the gas development and gas exposure setup.

Holographic multiplexing in a photopolymerisable hybrid sol-gel

Holographic multiplexing techniques enhance functionality and information storage by leveraging the inherent selectivity of holograms. This is crucial for advancing holographic sensors, which excel in simultaneously detecting multiple parameters from a single input signal. This study explores the potential of the recent photopolymerisable hybrid sol-gel (PHSG) material for application in Space sensing systems through the investigation of its holographic angular multiplexing capabilities. For the first time, to the best of our knowledge, we report the successful recording of up to five angularly multiplexed gratings with diffraction efficiencies (DE) ≥ 15% in 187 ± 18 µm PHSG layers. A 3 mW/cm2 laser beam was used to record gratings (0–20° angular separation) with a spatial frequency of 800 ± 20 lines/mm utilising different exposure times. The study revealed that each successive multiplexing in the single-layer region resulted in a decrease in the material's recording sensitivity. Holographic recording sensitivity and DE growth during the grating formation period depend on the number of gratings multiplexed in the layer. The seven-month-old, multiplexed gratings demonstrate consistent DE, stable angular selectivity and diffraction angle. This study positions the PHSG material as a promising candidate for developing reliable multiplexed devices.

Monitoring Bioindication of Plankton through the Analysis of the Fourier Spectra of the Underwater Digital Holographic Sensor Data.

The study presents a bioindication complex and a technology of the experiment based on a submersible digital holographic camera with advanced monitoring capabilities for the study of plankton and its behavioral characteristics in situ. Additional mechanical and software options expand the capabilities of the digital holographic camera, thus making it possible to adapt the depth of the holographing scene to the parameters of the plankton habitat, perform automatic registration of the "zero" frame and automatic calibration, and carry out natural experiments with plankton photostimulation. The paper considers the results of a long-term digital holographic experiment on the biotesting of the water area in Arctic latitudes. It shows additional possibilities arising during the spectral processing of long time series of plankton parameters obtained during monitoring measurements by a submersible digital holographic camera. In particular, information on the rhythmic components of the ecosystem and behavioral characteristics of plankton, which can be used as a marker of the ecosystem well-being disturbance, is thus obtained.

Diagnostics of luminescent recording media based on the polarized scattering spectra of hologram sensors formed in the substance analyzed

The article is devoted to the diagnosis and identification of luminescent holographic information carriers in particular wine products using polarization holographic spectroscopy methods. For the first time, to our best knowledge, a technique has been developed for measuring and analyzing scattered polarized light (depolarization spectra) on polarization-holographic sensors formed in analyte. Polarized scattering spectra on a hologram sensor (measuring transducers) are of particular interest, since they provide information not only about the chemical composition of the media, for example, luminescence and absorption spectra, but also about particles that may be present in the analyte – the higher the anisotropy of the molecules and atoms, the greater the depolarization. Methods for measuring polarized scattering and excitation spectra carried out for various samples of holographic materials, as well as methods for processing and presenting the obtained spectral data are described. This may be of interest, since recording media, in particular wine, are complex colloidal systems. For the diagnosis, classification and identification of recording materials, it is proposed for the first time to use reflective holographic sensors (Yu.N. Denisyuk) of various physical natures (the concept of a spectral holographic portrait).

Principle and application of holographic modal wavefront sensor for extended objects and general aberration modes

By employing a computer-generated hologram (CGH) to modulate the incident wavefront, the holographic modal wavefront sensor (HMWFS) can efficiently measure multiple aberration modes in a single shot, providing significant advantages such as computational simplicity, rapid measurement speed, and customizable assessment of aberration modes. However, the current HMWFS is confined to point-like objects and aberrations with specific orthogonality, thereby limiting its application scope. In this paper, we introduce a novel HMWFS that, to the best of our knowledge, is compatible with extended objects and general aberration modes. We establish the theoretical relationship between the second moment of the image intensity and the coefficients of general aberration modes for extended objects. Simulation and experimental results confirm the feasibility and performance of the proposed HMWFS. Additionally, we demonstrated its practical use in measuring misalignments of the secondary mirror of a space telescope. Simulations show that the misalignments can be effectively corrected within 2∼3 iterations.

A Conformable Holographic Sensing Bandage for Wound Monitoring

AbstractChronic wound monitoring can provide personalized pathophysiological information for wound management and treatment. Continuously monitoring the wound milieu via the holographic pH sensor can reflect the wound healing processes. However, the integration with wearable devices is hindered by its inherently restricted interrogation angle dependency within 5°. Herein, a ball bearing‐based double photopolymerization method is developed to fabricate holographic pH sensors with a broader interrogation angle range of 15°–60° in wound exudates. The fabricated holographic pH sensor is then integrated with the flexible ultrathin polyurethane substrate, which replays a total Bragg peak shift of approximately 150 nm with physiological pH changes from 7.00 to 8.75. The conformable holographic pH sensing bandages demonstrate the ability to quantify the pH value under various bending manipulations, simulating the mounting on the body surface. The reversibility in artificial wound exudate demonstrates the durability and capability of real‐time pH monitoring in the wound milieu with minimal effect on the replay wavelength. The addition of electrolytes, albumin, urea, uric acid, lactate, and glucose does not interfere with the readout over the physiological pH range of wound exudates. The obtained conformable holographic sensing bandage benefits the wound healing process monitoring through colorimetric interrogation at point‐of‐care (POC) settings.

Detecting vibrations in digital holographic multiwavelength measurements using deep learning.

Digital holographic multiwavelength sensor systems integrated in the production line on multi-axis systems such as robots or machine tools are exposed to unknown, complex vibrations that affect the measurement quality. To detect vibrations during the early steps of hologram reconstruction, we propose a deep learning approach using a deep neural network trained to predict the standard deviation of the hologram phase. The neural network achieves 96.0% accuracy when confronted with training-like data while it achieves 97.3% accuracy when tested with data simulating a typical production environment. It performs similar to or even better than comparable classical machine learning algorithms. A single prediction of the neural network takes 35µs on the GPU.

Holographic Sensor Based on Bayfol HX200 Commercial Photopolymer for Ethanol and Acetic Acid Detection.

This paper presents a holographic sensor based on reflection holograms recorded in the commercial photopolymer Bayfol® HX 200. The recording geometry and index modulation of the hologram were optimised to improve accuracy for this specific application. The sensor was subjected to tests using various analytes, and it exhibited sensitivity to acetic acid and ethanol. The measurements revealed a correlation between the concentration of the analyte in contact with the sensor's surface and the resulting wavelength shift of the diffracted light. The minimum detectable concentrations were determined to be above 0.09 mol/dm3 for acetic acid and 5% (v/v) for ethanol. Notably, the sensors demonstrated a rapid response time. Given that ethanol serves as a base for alcoholic beverages, and acetic acid is commonly found in commercial vinegar, these sensors hold promise for applications in food quality control.

Non-interferometric stand-alone single-shot holographic camera using reciprocal diffractive imaging

An ideal holographic camera measures the amplitude and phase of the light field so that the focus can be numerically adjusted after the acquisition, and depth information about an imaged object can be deduced. The performance of holographic cameras based on reference-assisted holography is significantly limited owing to their vulnerability to vibration and complex optical configurations. Non-interferometric holographic cameras can resolve these issues. However, existing methods require constraints on an object or measurement of multiple-intensity images. In this paper, we present a holographic image sensor that reconstructs the complex amplitude of scattered light from a single-intensity image using reciprocal diffractive imaging. We experimentally demonstrate holographic imaging of three-dimensional diffusive objects and suggest its potential applications by imaging a variety of samples under both static and dynamic conditions.

Construction of beta-cyclodextrin modified holographic sensor for the determination of ibuprofen in plasma and urine

The drug abuse has become a worldwide social and medical problem. The development of drug-sensitive sensors is of vital importance to the point-of-care (POC) analysis, providing fast instructions for medical and forensic diagnosis. The holographic sensor as a feasible optical sensor shows merits of label-free, quantitative detection, reusability and continuous detection. In this work, we designed a beta-cyclodextrin (β-CD) modified holographic sensor which achieved two important sensing functions simultaneously, response to ibuprofen and then serve as an optical transducer. Via the host-guest interaction, ibuprofen could come into the cavity of β-CD with a high binding constant and stability. Due to the repulsion interaction among the ionized ibuprofen molecules and increased osmotic pressure in the polymer, the exterior water molecules came into the holographic polymer, enlarging the grafting spacing and inducing the red-shift in the reflection wavelength. When applied for the determination of ibuprofen in biological samples, the prepared functional holographic sensor showed good linearity, negligible matrix interference, fast response within 5 min, satisfactory precision and accuracy. The reflection wavelength could occur around 30 nm red-shift and its color obviously changed from green to red under the trigger of highly toxic concentration of ibuprofen which could be used for the POC diagnosis.

Analog holographic wavefront sensor for defocus and spherical aberration measurement recorded in a photopolymer.

An analog holographic wavefront sensor (AHWFS), for measurement of low and high order (defocus and spherical aberration) aberration modes has been developed as volume phase holograms in a photopolymer recording medium. This is the first time that high order aberrations such as spherical aberration can be sensed using a volume hologram in a photosensitive medium. Both defocus and spherical aberration were recorded in a multi-mode version of this AHWFS. Refractive elements were used to generate a maximum and minimum phase delay of each aberration which were multiplexed as a set of volume phase holograms in an acrylamide based-photopolymer layer. The single-mode sensors showed a high degree of accuracy in determining various magnitudes of defocus and spherical aberration generated refractively. The multi-mode sensor also exhibited promising measurement characteristics and similar trends to the single-mode sensors were observed. The method of quantifying defocus was improved upon and a brief study into material shrinkage and sensor linearity is presented.

Reusable Dual‐Photopolymerized Holographic Glucose Sensors

AbstractDiabetes is well established as a widespread, incurable, and fatal disease with glucose monitoring and tight glycaemic control vital for effective illness prevention and management. Hydrogel‐based holographic sensors serve as a low‐cost and label‐free colorimetric sensing platform, directly identifiable by the naked eye and spectroscopy for quantitative monitoring. Herein, a cost‐effective and reusable holographic glucose sensor is developed via single pulse UV‐induced dual‐photopolymerization of boronic acid functionalized hydrogels for point‐of‐care (POC) diagnosis. Computational modeling of holographic sensors response is conducted following Braggs law alongside the study of fabrication parameter optimization and sensor swelling dynamics. Fabrication conditions, responsive and interference hydrogel compositions of holographic sensors are investigated to improve response time, sensitivity in urine (13.03 nm mmol−1 L−1), limit of detection (0.06 mmol L−1), and reusability. Photolithographic patterning of hydrogel‐based holographic sensors permits the inscription of additional information into the sensors for qualitative measurement. Selectivity, reversibility, and continuous monitoring of urine samples are conducted over a physiological glucose concentration range (0.0–9.4 mmol L−1) to demonstrate the viability for diabetic risk identification. The simple incorporation of glucose sensors in a reusable urinary analysis prototype is validated in human urine, showing potential for POC to reduce patient dependency on invasive diabetic monitoring procedures.

Breaking of Wavelength-Dependence in Holographic Wavefront Sensors Using Spatial-Spectral Filtering.

Nowadays, wavefront sensors are widely used to control the shape of the wavefront and detect aberrations of the complex field amplitude in various fields of physics. However, almost all of the existing wavefront sensors work only with quasi-monochromatic radiation. Some of the methods and approaches applied to work with polychromatic radiation impose certain restrictions. However, the contemporary methods of computer and digital holography allow implementing a holographic wavefront sensor that operates with polychromatic radiation. This paper presents a study related to the analysis and evaluation of the error in the operation of holographic wavefront sensors with such radiation.

Пространственно-спектральная фильтрация светового поля с помощью фазового модулятора света

An improved approach to the synthesis of holographic filters, which are achromatic computer-generated Fourier holograms, is demonstrated, taking into account the spatial and spectral characteristics of the light field. An experimental testing of the obtained filters was carried out based on the use of a holographic wavefront sensor operating on the principles of correlation analysis, using several quasi-monochromatic radiation sources. Using the proposed filters, the longitudinal chromatic aberration was measured, the value of which was λ/3 with an error of λ/50.

Field evaluation of a novel holographic single-image depth reconstruction sensor

A camera-based single-image sensor is presented, that is able to measure the distance of one or multiple object points (light emitters). The sensor consists of a camera, whose lens is upgraded with a diffractive optical element (DOE). It fulfils two tasks: adding a vortex point spread function (PSF) and replication of the vortex PSFs to a predefined pattern of K spots. Both, shape and rotation of the vortex PSF is sensitive to defocus. The sensor concept is presented and its capabilities evaluated both on axis and off-axis. The achieved standard deviation of the error ranges between 8.5 μm (on-axis) and 3.5 μm (off-axis) within a measurement range of 20 mm. However, as soon as calibration and measurement position no longer match, the accuracy is limited. An analysis of the effects responsible for this are also part of the publication.