Optical Aberrations Research Articles

Angle‐Based Neuromorphic Wave Normal Sensing

AbstractAngle‐based wavefront sensing has a rich historical background in measuring optical aberrations. The Shack–Hartmann wavefront sensor is widely employed in adaptive optics systems due to its high optical efficiency and high robustness. However, simultaneously achieving high sensitivity and large dynamic range is still challenging, limiting the performance of diagnosing fast‐changing turbulence. To overcome this limitation, angle‐based neuromorphic wave normal sensing, which serves as a differentiable framework developed on the asynchronous event modality is proposed. Herein, it is illustrated that the emerging computational neuromorphic imaging paradigm enables a direct perception of a high‐dimensional wave normal from the highly efficient temporal diversity measurement. To the best of available knowledge, the proposed scheme is the first to successfully surpass the spot‐overlapping issue caused by the curvature constraint in classical angle‐based wavefront sensing setups under challenging dynamic scenarios.

Optical phase aberration correction with an ultracold quantum gas

Optical phase aberration correction with an ultracold quantum gas

Analysis of Macromolecular Size Distributions in Concentrated Solutions

AbstractThe solution state of macromolecules in concentrated solutions impacts fields ranging from cell biology, to colloid chemistry and engineering of protein pharmaceuticals. Dependent on the interplay between repulsive and weakly attractive forces, proteins may exhibit oligomerization, aggregation, crystallization, liquid‐liquid phase separation, or the formation of multiprotein complexes. The particle size‐distribution is a key characteristic, but difficult to determine when interparticle distances are on the order of their size and macromolecular motion is coupled through hydrodynamic interactions. Here we extend sedimentation velocity analytical ultracentrifugation to measure macromolecular size distributions under these conditions: We apply results from statistical fluid mechanics for the concentration‐dependence of hindered settling and diffusion, embedded in a mean‐field approximation that can resolve coupled sedimentation and diffusion processes of different sized species given experimental sedimentation data. This is combined with a description of transient optical aberrations from lensing in the refractive index gradients associated with sedimentation boundaries (Wiener skewing). We demonstrate this approach in the application to protein solutions with macromolecular volume fractions up to ≈10 %, for example, resolving monomers and dimers of albumin at 140 mg/ml. This enables size‐distribution analysis of proteins at concentrations of therapeutic antibody formations and close to physiological concentration in serum and cells.

A Bifurcated Reconnecting Current Sheet in the Turbulent Magnetosheath

We report the Magnetospheric Multiscale (MMS) observation of a bifurcated reconnecting current sheet in Earth’s dayside magnetosheath. Typical signatures of the ion diffusion region, including sub-Alfvénic demagnetized ion outflow, super-Alfvénic electron flows, Hall magnetic fields, electron heating, and energy dissipation, were found when MMS traversed the current sheet. The weak ion exhaust at the current sheet center was bounded by two current peaks in which super-Alfvénic electron flow directed toward and away from the X line were observed, respectively. Both off-center current peaks were primarily carried by electrons, one of which was supported by field-aligned current, while the other was mainly supported by current driven by electric field drift. The two current peaks also exhibit other differences, including electron heating, electron pitch angle distributions, electron nongyrotropy, energy dissipation, and magnetic field curvature. An ion-scale magnetic flux rope was detected between the two current peaks where electrons showed field-aligned bidirectional distribution, in contrast to field-aligned distribution parallel to the magnetic field in two current peaks. The observed current sheet was embedded in a background shear flow. This shear flow worked together with the guide field and asymmetric field and density to affect the electron dynamics. Our results reveal the reconnection properties in this special plasma and field regime which may be common in turbulent environments.

Simulation Study of High-Precision Characterization of MeV Electron Interactions for Advanced Nano-Imaging of Thick Biological Samples and Microchips

The resolution of a mega-electron-volt scanning transmission electron microscope (MeV-STEM) is primarily governed by the properties of the incident electron beam and angular broadening effects that occur within thick biological samples and microchips. A precise understanding and mitigation of these constraints require detailed knowledge of beam emittance, aberrations in the STEM column optics, and energy-dependent elastic and inelastic critical angles of the materials being examined. This simulation study proposes a standardized experimental framework for comprehensively assessing beam intensity, divergence, and size at the sample exit. This framework aims to characterize electron-sample interactions, reconcile discrepancies among analytical models, and validate Monte Carlo (MC) simulations for enhanced predictive accuracy. Our numerical findings demonstrate that precise measurements of these parameters, especially angular broadening, are not only feasible but also essential for optimizing imaging resolution in thick biological samples and microchips. By utilizing an electron source with minimal emittance and tailored beam characteristics, along with amorphous ice and silicon samples as biological proxies and microchip materials, this research seeks to optimize electron beam energy by focusing on parameters to improve the resolution in MeV-STEM/TEM. This optimization is particularly crucial for in situ imaging of thick biological samples and for examining microchip defects with nanometer resolutions. Our ultimate goal is to develop a comprehensive mapping of the minimum electron energy required to achieve a nanoscale resolution, taking into account variations in sample thickness, composition, and imaging mode.

Adaptive optical correction for in vivo two-photon fluorescence microscopy with neural fields.

Adaptive optics (AO) restore ideal imaging performance in complex samples by measuring and correcting optical aberrations, but often require custom-built microscopes with carefully aligned wavefront sensing/shaping devices and can be susceptible to sample motion. Here we describe NeAT, a computational framework using neural fields for AO two-photon fluorescence microscopy. NeAT estimates wavefront aberration and recovers sample structure from a 3D image stack without requiring external datasets for training. Incorporating motion correction in learning and correcting conjugation errors commonly found in commercial microscopes, NeAT is designed for deployment in biological laboratories for in vivo imaging. We validate NeAT's performance using a custom-built microscope with a wavefront sensor under varying signal-to-noise ratios, aberration, and motion conditions. With a commercial microscope, we demonstrate real-time aberration correction for in vivo morphological and functional imaging in the living mouse brain, with NeAT improving signal and accuracy of glutamate and calcium imaging of synapses and neurons.

Multifocal Rigid Gas Permeable Contact Lenses with Multi-Tangential Positioning and Corrected Spherical Aberration for Myopia Control

Slowing the progression of myopia has become an extensive concern for parents of children with myopia. According to research findings in animals, eye growth is primarily influenced by the peripheral retina. Treatment options such as orthokeratology, daytime bifocal or multifocal soft contact lens usage are available because they can induce relative myopia in the periphery. In this work, a new multifocal rigid gas permeable (MFRGP) contact lens for myopia prevention and control in adolescents was designed specifically for preventing and controlling myopia in adolescents. This lens features a multi-tangent alignment curve, smaller spherical aberration, and transition defocus. FocalPoints and UPC 100 Vision were used for lens design and lathing, respectively. The lens structure and power profile were measured using IS830 and CONTEST 2, respectively. The elimination of lens aberrations was achieved through design optimization using ZEMAX with ray tracing. Lens fitting was evaluated using slit-lamp microscopy and corneal topography.

Evaluation of monocular and binocular contrast perception on virtual reality head-mounted displays.

Visualization of medical images on a virtual reality (VR) head-mounted display (HMD) requires binocular fusion of a stereoscopic pair of graphical views. However, current image quality assessment on VR HMDs for medical applications has been primarily limited to time-consuming monocular optical bench measurement on a single eyepiece. As an alternative to optical bench measurement to quantify the image quality on VR HMDs, we developed a WebXR test platform to perform contrast perceptual experiments that can be used for binocular image quality assessment. We obtained monocular and binocular contrast sensitivity responses (CSRs) from participants on a Meta Quest 2 VR HMD using varied interpupillary distance (IPD) configurations. The perceptual result shows that contrast perception on VR HMDs is primarily affected by optical aberration of the VR HMD. As a result, monocular CSR degrades at a high spatial frequency greater than 4 cycles per degree when gazing at the periphery of the display field of view, especially for mismatched IPD settings consistent with optical bench measurements. On the contrary, binocular contrast perception is dominated by the monocular view with superior image quality measured by the contrast. We developed a test platform to investigate monocular and binocular contrast perception by performing perceptual experiments. The test method can be used to evaluate monocular and/or binocular image quality on VR HMDs for potential medical applications without extensive optical bench measurements.

Quality control for single-cell analysis of high-plex tissue profiles using CyLinter.

Tumors are complex assemblies of cellular and acellular structures patterned on spatial scales from microns to centimeters. Study of these assemblies has advanced dramatically with the introduction of high-plex spatial profiling. Image-based profiling methods reveal the intensities and spatial distributions of 20-100 proteins at subcellular resolution in 103-107 cells per specimen. Despite extensive work on methods for extracting single-cell data from these images, all tissue images contain artifacts such as folds, debris, antibody aggregates, optical aberrations and image processing errors that arise from imperfections in specimen preparation, data acquisition, image assembly and feature extraction. Here we show that these artifacts dramatically impact single-cell data analysis, obscuring meaningful biological interpretation. We describe an interactive quality control software tool, CyLinter, that identifies and removes data associated with imaging artifacts. CyLinter greatly improves single-cell analysis, especially for archival specimens sectioned many years before data collection, such as those from clinical trials.

Method for Extracting Optical Element Information Using Optical Coherence Tomography.

This study examines the measurement of film thickness, curvature, and defects on the surface or inside of an optical element using a highly accurate and efficient method. This is essential to ensure their quality and performance. Existing methods are unable to simultaneously extract the three types of information: thickness, curvature, and defects. Spectral-domain optical coherence tomography (SD-OCT), a non-invasive imaging technique with imaging depths down to the millimeter scale, provides the possibility of detecting the optical element components' parameters. In this paper, we propose an error correction model for compensating delay differences in A-scan, field curvature, and aberration to improve the accuracy of system fitting measurements using SD-OCT. During data processing, we use the histogram-equalized gray stretching (IAH-GS) method to deal with strong reflections in the thin film layers inside the optics using individual A-scan averages. In addition, we propose a window threshold cutoff algorithm to accurately identify defects and boundaries in OCT images. Finally, the system is capable of rapidly detecting the thickness and curvature of film layers in optical elements with a maximum measurement depth of 4.508 mm, a diameter of 15 × 15 mm, a resolution of 5.69 microns, and a sampling rate of 70 kHz. Measurements were performed on different standard optical elements to verify the accuracy and reliability of the proposed method. To the best of our knowledge, this is the first time that thickness, curvature, and defects of an optical film have been measured simultaneously, with a thickness measurement accuracy of 1.924 µm, and with a difference between the calibrated and nominal curvature measurements consistently within 1%. We believe that this research will greatly advance the use of OCT technology in the testing of optical thin films, thereby improving productivity and product quality.

On massive higher spin supermultiplets in d = 4

In this work we discuss the cubic interactions for massless spin 3/2 gravitino with massive higher spin supermultiplets using three superblocks (2, 3/2), (5/2, 2) and (3, 5/2) as the first non-trivial examples. We use gauge invariant formalism for the massive higher spin fields and, as is common in such cases, we face an ambiguity related with the possible field redefinitions due to the presence of Stueckelberg fields. From one hand, we show how this ambiguity can be used as one more way to classify possible cubic vertices. We also note that all these field redefinitions do not change the part of the Lagrangian which appears in the unitary gauge (where all Stueckelberg fields are set to zero) so we still have some important independent results. From the other hand, we show how using the so-called unfolded formalism one can fix these ambiguities and obtain consistent deformations for all massive field gauge invariant curvatures which is the most important step in the Fradkin-Vasiliev formalism. Unfortunately, this works for the massive fields only so the way to construct deformations for the massless field curvatures is still has to be found.

Electric Field Intensity Assessment on Curved Wires for Domestic Installations

The increasing complexity of domestic electrical installations necessitates a thorough understanding of electric field intensity, particularly when dealing with curved wires. This paper presents the results on the assessment of the electric field intensity in curved wire configurations, which are commonly encountered in residential settings due to architectural constraints. This study employs both theoretical and simulation approaches with the help of the Finite Element Based Software (COMSOL Multiphysics). The theoretical and simulations were used for a case of straight wire to allow validation of the model through comparing simulation results with the theoretically computed electric field intensity using mathematical formula. Later on, the COMSOL Multiphysics were used to compute electric field intensity under various curvature radii. The results of maximum electric field intensity against curvature radii were then plotted as scatter in excel and then fitted by the equation from the trendline option. The results show that the curvature of wires significantly influences electric field distribution. The electric field intensity was observed to be much higher for a case of small curvature radius as compared to larger curvature radius. For example, for the type of the geometry presented in this paper to represent the PVC wire used in domestic buildings’ electrical installations, the maximum electric field intensity for curvature radius of 0.025 mm was observed to be about 7 times for a case when the curvature radius was 10 mm. In additional, the power equation was found to model well the relationship between the maximum electric field intensity and curvature radius of the geometry presented in this paper

Off-axis freeform optical design for large curved field of view imaging

Recording neuron activities is pivotal for elucidating the functionality of the nervous system. However, the curved cortex surface of experimental mice presents a significant challenge for optical systems, particularly when a larger field of view (FOV) is required. To address this challenge, we have designed an off-axis three-mirror system that incorporates freeform surfaces on both the primary and secondary mirrors. This system achieves a large imaging FOV of 18°×9°, delivering near-diffraction-limit imaging quality across a curvature spectrum of −14.7 to −15.3mm. A manufacturability analysis indicates that the freeform surfaces are straightforward to produce, and the overall system demonstrates low sensitivity to tolerance and measurement errors. This study introduces a novel, to the best of our knowledge, solution to the field curvature constraints in optical imaging of cortical activity, providing substantial technical support for in vivo neuronal imaging endeavors.

Deformation and optical aberration prediction in ultra-precision Single Point Diamond Turning of optical components

Aluminum is the material of choice for the majority of aerospace components, and, in the past few years, its application has been extended also to the mirrors of space telescopes because of the improved thermal behavior and the possibility to build the entire telescope with the same material. However, the low elastic modulus of such material, combined with the extremely tight tolerances of optical applications, make the production of these components very challenging and, usually, based on a trial-and-error approach. This paper presents a structured methodology for the prediction of the results of manufacturing in Single Point Diamond Turning of optical components, both in terms of absolute deformation as well as optical aberrations (via Zernike polynomials). All the most significant parameters acting on the workpiece have been simulated and combined. The proposed approach has been experimental validated on an actual aluminum mirror, proving its good accuracy (<5 % rms error). While some improvement can be performed to better match the experimental data in terms of Zernike coefficients, especially for non-symmetric aberrations, this paper forms the basis for an off-machine optimization of the SPDT process, drastically reducing the trial-and-error efforts.

Practical limits to spatial resolution of magnetic imaging with a quantum diamond microscope

Widefield quantum diamond microscopy is a powerful technique for imaging magnetic fields with high sensitivity and spatial resolution. However, current methods to approach the ultimate spatial resolution (&amp;lt;500 nm) are impractical for routine use as they require time-consuming fabrication or transfer techniques to precisely interface the diamond sensor with the sample to be imaged. To address this challenge, we have designed a co-axial sensor holder that enables simple, repeatable sensor–sample interfacing while being compatible with high numerical aperture (NA) optics. With our new design we demonstrate low standoffs &amp;lt;500 nm with a millimeter sized sensor. We also explore the relationship between spatial resolution and NA spanning from 0.13 to 1.3. The spatial resolution shows good agreement with the optical diffraction limit at low NA but deviates at high NA, which is shown to be due to optical aberrations. Future improvements to our design are discussed, which should enable magnetic imaging with &amp;lt;500 nm resolution in an accessible, easy-to-use instrument.

A Kernel-Based Calibration Algorithm for Chromatic Confocal Line Sensors.

In chromatic confocal line sensors, calibration is usually divided into peak extraction and wavelength calibration. In previous research, the focus was mainly on peak extraction. In this paper, a kernel-based algorithm is proposed to deal with wavelength calibration, which corresponds to the mapping relationship between peaks (i.e., the wavelengths) in image space and profiles in physical space. The primary component of the mapping function is depicted using polynomial basis functions, which are distinguished along various dispersion axes. Considering the unknown distortions resulting from field curvature, sensor fabrication and assembly, and even the inherent complexity of dispersion, a typical kernel trick-based nonparametric function element is introduced here, predicated on the notion that similar processes conducted on the same sensor yield comparable distortions.To ascertain the performance with and without the kernel trick, we carried out wavelength calibration and groove fitting on a standard groove sample processed via glass grinding and with a reference depth of 66.14 μm. The experimental results show that depths calculated by the kernel-based calibration algorithm have higher accuracy and lower uncertainty than those ascertained using the conventional polynomial algorithm. As such, this indicates that the proposed algorithm provides effective improvements.

Chromatic aberration compensation in a digital camera lens for fringe projection profilometry

This work presents a simplified method for compensating the chromatic aberration of a digital camera lens using orthogonal fringe patterns displayed on an LCD monitor. The proposed compensation method drastically reduces the complex mathematical calculations to an arithmetic procedure of the simple rule of three. First, the implemented method is simulated, and then the experimental results confirm the simulated model. The mean squared error and standard deviation of the chromatic aberration compensation are calculated. Additionally, an arrangement is presented to avoid systematic errors when calculating the chromatic aberration of the lens to be compensated without additional digital processing.

Spatial phase distortion compensation technology based on combinatorial optimization method in heterodyne detection

The spatial phase distortion caused by turbulent atmosphere, target speckle, or optical system aberration causes decoherence of heterodyne signals. The decoherence effect is the key problem that imposes restrictions on the application of laser heterodyne techniques. We propose an approach for spatial phase distortion correction based on a genetic algorithm by establishing a one-to-one correspondence between combination of spatial phase compensation amounts and heterodyne efficiency of the system. The spatial phase distortion compensation problem is converted into a combinatorial optimization problem. The experiment results show that the method achieves excellent compensation performance for the spatial phase distortion, significantly contributing to the applications of heterodyne techniques.

The possibilities of using adaptive optics in modern ophthalmology

Until recently, the assessment of individual retinal cells was possible only with the help of histological examination, since such retinal imaging methods as scanning laser ophthalmoscopy and optical coherence tomography had low resolution to obtain images of structures at the cellular level, which was mainly due to aberrations caused by the optics of the eye. Adaptive optics technology has improved the performance of optical systems by correcting optical wavefront aberrations. Adaptive optics allows noninvasively visualizing the retina at the microscopic level in vivo, providing the opportunity to analyze individual structures such as photoreceptors, blood vessels, nerve fibers, ganglion cells and a lattice plate. Adaptive optics imaging in patients with diabetic retinopathy makes it possible to accurately determine the spatial distribution of cones, a decrease in which is associated with the presence of diabetic retinopathy and an increase in the severity of the disease. The detection of differences in cone distribution density between the control group and patients with diabetes mellitus without clinical signs of diabetic retinopathy may contribute to its early diagnosis, as well as a deeper understanding of the consequences of changes in the photoreceptor apparatus. Adaptive optics imaging methods are able to identify disorders of photoreceptor cells and assess the degree of progression of age-related macular degeneration, which definitely expands diagnostic capabilities at the early stages of its detection. Assessment of the condition of nerve fiber bundles through the use of Adaptive optics helps to identify changes associated with glaucoma, and also provides the ability to visualize details that cannot be evaluated using optical coherence tomography. Adaptive optics imaging allows you to directly measure the wall of retinal vessels and the diameter of their lumen. The ratio of wall thickness to vessel lumen and the cross-sectional area of the vessel wall directly reflect the remodeling process and can be used for the purpose of early diagnosis and monitoring of hypertension.

Dynamic 3D Fresnel incoherent correlation holography imaging based on single-shot mirrored phase-shifting technology.

Fresnel incoherent correlation holography (FINCH) records coaxial holograms for wide-field 3D imaging with incoherent light, but its temporal phase-shifting strategy makes dynamic imaging challenging. Here, we present a compact, portable single-shot mirrored phase-shifting (SSPMS) module that can be easily integrated into the FINCH system, achieving secondary modulation of self-interference beams to enable the simultaneous acquisition of four phase-shift holograms in a single exposure. Compared with previously reported methods that use diffraction gratings to spatially separate self-interference beams at specific angles, this module duplicates a laterally shifted mirrored beam using a simply modified Michelson interferometer, so the phase-shifting holograms obtained via this module are free from optical aberrations or higher-order diffracted light noises. The feasibility of the proposed method is experimentally demonstrated through imaging dynamic 3D grayscale scenes.