Depth Of Focus Research Articles

Application of the Stochastic Finite Fault Model in the Study of the Source Rupture Process of the Mw7.6 Earthquake in the Noto Peninsula, Japan on January 1, 2024

On January 1, 2024, a Mw7.6 earthquake occurred on the Noto Peninsula in Japan, with a focal depth of 9.6 kilometers. To validate the effectiveness of using a finite fault hybrid slip model to simulate strong ground motion events, this study utilized strong motion records from the KiK-net station network of the National Research Institute for Earth Science and Disaster Resilience (NIED) in Japan. Initially, 29 fundamental stations were selected, and 13 of these stations were chosen for further study using the finite fault method. Constrained by the geometric parameters of the initial model from the strong motion inversion, a hybrid slip distribution model (HSM) was established based on the stochastic finite fault model and semi-empirical relationships between source parameters. This model accurately reflects the spatial and temporal characteristics of the source rupture, and its results are comparable to those obtained by the United States Geological Survey (USGS) using GNSS and other long-period effect data. Additionally, using the dynamic corner frequency-based stochastic ground motion synthesis method (EXSIM), a comparative study was conducted on the pseudo-acceleration response spectra (PSA) of the hybrid slip model, the strong motion inversion model, and the source rupture model provided by USGS at the selected stations. These were then compared with the response spectra of actual station records. It was found that all three models showed good fitting results, and in the short-period range, the simulated values of the HSM were closer to the actual records. Finally, the relative error mean and variance between the HSM and actual records’ PSA at different frequencies were calculated for 29 stations. It reveals that they still had good fitting results. Overall, the findings demonstrate that even without relying on extensive station data, the hybrid slip model efficiently and accurately simulated high-frequency strong ground motions near the fault with a damping ratio of 5%, verifying the reliability and applicability of this method.

Upgrading a Low-Cost Seismograph for Monitoring Local Seismicity

The use of a dense network of commercial high-cost seismographs for earthquake monitoring is often financially unfeasible. A viable alternative to address this limitation is the development of a network of low-cost seismographs capable of monitoring local seismic events with a precision comparable to that of high-cost instruments within a specified distance from the epicenter. The primary aim of this study is to compare the performance of an advanced, contemporary low-cost seismograph with that of a commercial, high-cost seismograph. The proposed system is enhanced through the integration of a 24-bit analog-to-digital converter board and an optimized architecture for a low-noise signal amplifier employing active components for seismic signal detection. To calibrate and assess the performance of the low-cost seismograph, an installation was deployed in a region of high seismic activity in Evgiros, Lefkada Island, Greece. The low-cost system was co-located with a high-resolution 24-bit commercial digitizer, equipped with a broadband (30 s—50 Hz) seismometer. An uninterrupted dataset was collected from the low-cost system over a period of more than two years, encompassing 60 local events with magnitudes ranging from 0.9 to 3.2, epicentral distances from 5.71 km to 23.45 km, and focal depths from 1.83 km to 19.69 km. Preliminary findings demonstrate a significant improvement in the accuracy of earthquake magnitude estimation compared to the initial configuration of the low-cost seismograph. Specifically, the proposed system achieved a mean error of ±0.087 when benchmarked against the data collected by the high-cost commercial seismograph. These results underscore the potential of low-cost seismographs to serve as an effective and financially accessible solution for local seismic monitoring.

Contrast Sensitivity and Stereopsis Outcomes Following LASIK Presbyopia Correction Based on the Corneal Aberration Modulation or Corneal Multifocality Induction Methods: A Systematic Review

Background. Modern laser vision correction for presbyopia treatment involves non-linear aspheric corneal ablation with the controlled induction of spherical aberration modulation to extend the depth of focus or corneal multifocality induction methods with or without micro-monovision in the non-dominant eye to provide continuous clear vision across distances. Anisometropia and the new higher-order aberrations pattern may be potential risk factors for postoperative stereopsis and contrast sensitivity (CS) deterioration. Purpose. The objective of this systematic review was to assess articles published until 2023 in which CS and/or stereopsis were reported following LASIK presbyopia treatment. Methods. We searched the PubMed, Scopus and Web of Science databases in accordance with the PRISMA 2020 flow diagram. The inclusion criteria specified original papers evaluating the outcomes of laser presbyopia correction as well as the pre- and postoperative assessment of stereopsis and/or CS. The Quality Assessment Tool was applied to assess the risk of bias. Results. We identified 13 studies, including 856 presbyopes (1712 eyes), with preoperative refractive errors from −11.13 D to +5.75 D, with the follow-up range between 3 and 30 months. Either contrast sensitivity improvement or no change following Presbyond® Laser Blended Vision and PresbyMAX® Hybrid was found in the reviewed articles. Some authors reported a significant CS reduction after symmetrical PresbyLASIK, wavefront-guided LASIK and aspheric monovision LASIK. Several studies assessing the effect of Presbyond® LBV on stereopsis showed conflicting results, with the near stereopsis being reduced, unchanged or increased. A significant decrease in stereopsis was reported after aspheric monovision LASIK. (5) Conclusions. The Presbyond® Laser Blended Vision is a safe procedure in terms of the preservation of contrast sensitivity for presbyopia treatment. More studies are needed to elucidate the impact of aspheric corneal ablation methods or other methods inducing corneal multifocality with or without micro-monovision on stereopsis and contrast sensitivity.

Focal beam position and shape manipulation enabled by polarization and plasmonic metasurfaces

Abstract Over the past few years, plasmonic metasurfaces have shown significant potential for the manipulation of the focal beam shape and position. However, traditional hole-type plasmonic metasurfaces have lower optical transmission (< 5%) and lack design freedom because most areas are opaque. Herein, we propose an island-type plasmonic metasurface design that achieves high optical transmission (approximately 50%), while allowing the focal position to be controlled via incident polarization. This plasmonic metasurface exhibits the geometric phase characteristics of anisotropic nano-ellipses, and an additional phase shift is induced by varying the nano-ellipse rotation angles. The metasurface can achieve phase modulation via a spatial nano-ellipse arrangement and enables focus at the desired location under specific incident polarization handedness. Moreover, the number of radial multiplexing in this plasmonic metasurface can be increased to provide multiple focal points to endow the metasurface with an extended focal depth (12.2 times the incident wavelength). The plasmonic metasurface performance was demonstrated through simulations and experiments. The proposed metasurface has a highly versatile design and has significant and diverse applications across multiple optical fields.

Unique thermal characteristics of polarization-insensitive metalenses over traditional refractive and diffractive lenses

The thermal characteristics of lenses play an essential role in the performance of optical systems, particularly infrared detection systems. Metalenses, composed of sub-wavelength nanostructured surfaces, have recently emerged as a promising technology to realize flat, lightweight, and mass-producible lenses. However, their thermal behavior remains largely unexplored. This study examines the impact of uniform temperature variations (both theoretically and experimentally) and laser heating (theoretically) on the performance of polarization-insensitive metalens (PIM) at a representative wavelength of 10.6 µm. We compare the thermal performance of PIMs with refractive and diffractive lenses, by a comprehensive structural, thermal, and optical performance (STOP) analysis through finite-element analysis (FEA) and finite-difference-time-domain (FDTD) simulations. A comprehensive analysis of various thermal aberration indicators reveals that the PIM exhibits smaller thermal aberrations than both the aspheric lens and the harmonic diffractive lens, and its performance is closer to that of a traditional diffractive optical element (DOE). We also find that the unique nanostructures of PIM make it highly sensitive to the refractive index change induced by temperature variations, allowing the PIM to achieve unique capabilities compared to other lenses. A typical example is that the PIM consistently demonstrates an opposite shift in focal length and depth of focus, contrary to conventional cases. We also experimentally verify the near-athermal properties of 5-centimeter-aperture metalens, confirming the advantages of large-aperture PIMs over refractive lenses in athermal infrared imaging applications. Additionally, our numerical analysis demonstrates that the broadband achromatic metalens notably outperforms the DOE in simultaneously achromatic (8 to 12 µm) and athermal (-60 to 80°C) performance. It is reasonable to speculate that the thermal diffraction efficiency of the achromatic metalens is likely superior to that of the achromatic multi-level diffractive lens (MDL). Our results confirm the strong potential of metalenses in athermal imaging applications.

Depth of focus as a function of spherical aberration using adaptive optics in pseudophakic subjects.

To measure visual acuity at three different defocus planes in pseudophakic subjects with varying levels of spherical aberration induced by an adaptive optics visual simulator. The study aimed to simulate Extended Depth of Focus (EDOF) intraocular lenses (IOLs). Private hospital (IMO, Barcelona, Spain). Observational case series; modelling theory. Through-focus visual acuity was measured in 26 pseudophakic subjects (age 63 ± 10 years old) with an adaptive optics visual simulator optimized for clinical use (VAO, Voptica SL, Murcia, Spain). Measurements were made under five different conditions of induced negative spherical aberration: 0, -0.07, -0.15, -0.23 and -0.30 μm (pupil diameter: 4.5 mm). Results were also modelled using ray tracing simulations. On average, depth of focus was extended when spherical aberration increased from -0.07 to -0.15 μm (4.5 mm pupil diameter). Some indivisuals (27%) experienced improved depth of focus with higher magnitudes of spherical aberration, while others (23%) exhibited no benefit from increased (negative) SA, as visual acuity dropped below acceptable levels. Depth of focus calculations based on ray tracing showed general agreement with the measurements. The visual conditions of EDOF IOLs were artificially recreated in a population of pseudophakic patients implanted with a monofocal IOL. The variability seen across subjects in visual acuity at different defocus planes suggests that visual simulators might be capable of screening subjects for suitability and tolerability of these advanced technology lenses.

Broadband reflective terahertz metalens employing Bessel beams for enhanced efficiency and depth of focus.

This paper presents a reflective terahertz (THz) Bessel metalens with broadband operation in the frequency range of 0.80-1 THz. The design employs a near-wavelength, polarization-insensitive resonator to achieve a wideband response. Optimized at 0.89 THz, the metalens integrates a hyperbolic phase configuration combined with a conical phase profile. By varying the cone angle, the metalens attains a focusing efficiency of up to 76% and an extended depth of focus of 21.7λ. Simulations demonstrate superior performance compared to conventional focusing metalenses. This design shows significant potential for applications in terahertz imaging, communications, and sensing technologies.

Outcomes of a non-diffractive extended depth of focus intraocular lens in patients with well-controlled glaucoma and ocular hypertension.

To assess visual outcomes and satisfaction of a non-diffractive extended depth of focus (EDOF) intraocular lens (IOL) in individuals with ocular hypertension (OHT) and well-controlled mild glaucoma undergoing cataract surgery. An investigator-initiated, single-center, prospective, interventional, noncomparative study conducted in Montreal, Canada. The study enrolled 31 patients (55 eyes) with OHT or mild glaucoma who received a non-diffractive EDOF IOL (Acrysof IQ Vivity). Participants underwent sequential cataract surgery with the Vivity IOL. Follow-up evaluations occurred at 1d, 1, and 3mo postoperatively, assessing uncorrected distance, intermediate, and near visual acuity. Questionnaires (QUVID: Questionnaire for visual disturbances and IOLSAT: Intraocular lens satisfaction) were administered pre and post-operatively to measure visual disturbances and spectacle independence in various lighting. Safety parameters included intraocular pressure (IOP), glaucoma medications, spherical equivalence, mean deviation and pattern standard deviation or square root of lost variance on Octopus visual field. At 1 and 3mo postoperatively, significant improvements were observed in uncorrected distance and intermediate visual acuity. Spectacle independence was enhanced for distance and intermediate vision, especially in bright light settings. Spectacle-free intermediate vision was improved even in dim lighting. Visual disturbances, particularly glare symptoms, were reduced, and there was a notable decrease in IOP and glaucoma medication burden at 3mo. There was more hazy vision postoperatively with no impact on visual acuity and visual satisfaction. The non-diffractive EDOF lens improves distance and intermediate spectacle-free visual function in patients with OHT and well-controlled glaucoma. The findings highlight significant improvements in visual acuity, reduced glare, enhanced spectacle independence, and improved visual performance in different lighting conditions.

High-efficiency focusing metalens based on metagrating arrays

The flexible and precise control of wavefronts of electromagnetic waves has always been a hot issue, and the emergence of metasurfaces has provided a platform to solve this problem, but their design and optimization remain challenging. Here, we demonstrate two design and optimization methods for metagrating-based metalenses based on the highest manipulation efficiency and highest diffraction efficiency. The metalens operating at 0.14 THz with numerical apertures of 0.434 is designed by these two methods for comparison. Then, the metalens is fabricated with photocuring 3D printing technology and an imaging system is built to characterize the distribution of focal spots. With the highest manipulation efficiency, the metalens shows a focal spot with the diameter of 0.93λ and depth of focus (DOF) of 22.7λ, and the manipulation and diffraction efficiencies reach 98.1% and 58.3%. With the highest diffraction efficiency, the metalens shows a focal spot with the diameter of 0.91λ and DOF of 24.6λ, and the manipulation and diffraction efficiencies reach 94.6% and 62.5%. The results show that the metalenses designed by both methods can perform a filamentous focal spot in the sub-wavelength scale with a long DOF; simultaneous high manipulation and diffraction efficiencies are obtained. A transmission imaging manner is used to verify the imaging capability of the metalenses, and the measurements are satisfactorily congruous with the anticipated results. The proposed methods can stably generate focal spots beyond the physical diffraction limit, which has a broad application in terahertz imaging, communications, etc.

Elongating the focal depth of a Bessel beam by manipulating polarization.

The limits on the numerical aperture and diameter of optical elements restrict the propagation distance of a Bessel beam, resulting in finite depth of focus. In this paper, a method is proposed to elongate the focal depth by splicing a Bessel beam with a circular Airy beam, which is respectively excited by left- and right-circularly polarized light with a birefringent dielectric metasurface. Simulation shows that the focal depth of the spliced Bessel beam at the wavelength of 532 nm is 2.56 times that of the original. The lateral resolution satisfies the Rayleigh criterion, and the focal spot remains consistent. This scheme not only breaks the transmission distance limit of a Bessel beam but also provides an alternative way to extend the beam focal depth. This can be applied in micromachining and microscopic imaging.

Physics-informed deep learning quantifies propagated uncertainty in seismic structure and hypocenter determination

Subsurface seismic velocity structure is essential for earthquake source studies, including hypocenter determination. Conventional hypocenter determination methods ignore the inherent uncertainty in seismic velocity structure models, and the impact of this oversight has not been thoroughly investigated. Here, we address this issue by employing a physics-informed deep learning (PIDL) approach that quantifies uncertainty in two-dimensional seismic velocity structure modeling and its propagation to hypocenter determination by introducing neural network ensembles trained on active seismic survey data, earthquake observation data, and the physical equation of wavefront movement. An analysis of an earthquake in southwest Japan using our method revealed that accounting for such uncertainty propagation significantly reduced the bias and uncertainty underestimation in the hypocenter determination, enabling quantitative evaluation of the focal depth relative to the plate boundary. Our results highlight the potential of PIDL for various geophysical inverse problems, such as investigating earthquake source parameters, which inherently suffer from uncertainty propagation.

Focal Depths and Mechanisms of Earthquakes in the Western Makran Region: A 30-Years Perspective

Focal Depths and Mechanisms of Earthquakes in the Western Makran Region: A 30-Years Perspective

Analysis of Ultrasonic Focusing in Silicon Wafers using the Angular Spectrum Approach and Ray Tracing

Understanding ultrasonic beam focusing in anisotropic media is crucial for optimizing nondestructive evaluation techniques, as many advanced materials exhibit anisotropic properties. This study investigates the focusing behavior of ultrasonic beams in silicon, a representative anisotropic material, across three crystallographic orientations (0°, 22.5°, and 45° offsets from the [1 0 0] axis) using the angular spectrum approach (ASA) and ray tracing to understand computational cost trade-offs between the two models while elucidating new focusing behaviors and profiles. The ASA model is used to construct three-dimensional wave field visualizations and localize focal depths. Ray tracing is then employed to map the focal profiles at the ASA-identified depths. The results demonstrate that focal behavior geometry and depth vary as the anisotropic orientation changes, with foci splitting for the 45° orientation and skewed focusing for the 22.5° orientation. For high-frequency approximations, the ASA method may effectively identify focal depths that can serve as focal planes for ray tracing, potentially reducing computational expense. This approach showed alignment in the present study for 25 MHz, though its validity depends on the material properties under consideration. These findings can be useful in devising alternative experimental configurations that optimize focusing within anisotropic solids.

Characterization of HVSR and VRSR in the Loess Plateau of China Based on Strong-Motion Data

In recent decades, China has collected extensive strong-motion data from the Loess Plateau, which is valuable for understanding the dynamic characteristics of loess sites and the effects of site conditions on seismic motions. The horizontal-to-vertical Fourier spectrum ratio (HVSR) and the horizontal-to-vertical velocity response spectrum ratio (VRSR) are widely used to study site dynamics. This study analyzes strong-motion data from the Loess Plateau to identify key features of the HVSR and VRSR curves. The results show that these spectral ratio curves effectively capture the dynamic behaviors of loess sites, minimizing the influences of earthquake magnitude and propagation path. While the spectral ratio peaks are less affected by magnitude, epicentral distance, and focal depth, they are significantly influenced by site conditions. Conversely, the dominant periods estimated from these curves are strongly influenced by magnitude, epicentral distance, and focal depth. For sites located on the Loess Plateau, the average amplification factor is approximately 3, with a mean predominant period of 0.4 s. These results provide valuable insights into the dynamic characteristics of loess sites and have practical implications for seismic design in the region.

Extended Depth of Focus (EDOF) and Trifocal Lenses: Advantages and Disadvantages. What Determines the Choice of Optical Correction? Review

The purpose: to compare the results of studies on intraocular lenses (IOLs) with extended depth of focus (EDOF) and trifocal intraocular lenses (THIOLs).Methods. The comparative analysis was conducted based on data from meta-analyses, systematic reviews, and randomized clinical trials. The electronic databases used were PubMed and Elibrary. The most commonly analyzed characteristics were postoperative refraction, visual acuity, optical aberrations, contrast sensitivity, visual quality, and dependence on glasses.Results. THIOL has significant advantages over EDOF in terms of postoperative refraction and visual acuity. This is demonstrated by a significantly lower postoperative residual spherical correction and spherical equivalent. There was no significant difference in postoperative astigmatism between the two groups. The analysis of visual acuity and eyeglass independence shows the advantages of EDOF for medium distances and THIOL for close distances. Some researchers prefer a combination of these two IOL types to achieve maximum results. Published data on optical phenomena indicate a higher number of dysphotopsias in the THIOL group. However, research results are highly contradictory due to their heterogeneity. A significant decrease in contrast sensitivity was observed in all groups for both photopic and mesopic conditions. Nevertheless, EDOF showed an advantage at lower spatial frequencies. In terms of satisfaction with the results obtained after surgery, there were no significant differences between the two groups of intraocular lenses (IOLs), as all patients reported a high level of satisfaction.Conclusion. Binocular implantation of a THIOL can provide greater independence from glasses and good vision at medium and short distances. However, patients should be aware of a possible decrease in contrast sensitivity and visual quality, especially at night, which may be accompanied by discomfort while driving. If more activity is required at intermediate distances in daily life, the choice of an EDOF IOL is crucial, and the patient may not require additional eyeglasses for closerange work if necessary. In clinical practice, knowing the characteristics of an IOL helps meet patient expectations and achieve high levels of satisfaction.

In Vivo Contactless, Cellular-Resolution Imaging of the Healthy and Pathological Human Limbus With 250-kHz Point-Scanning SD-OCT.

To demonstrate that high-seed, ultra-high-resolution spectral-domain optical coherence tomography (SD-OCT) technology can image in vivo fine morphological features in the healthy and pathological human limbus. A compact, fiberoptic SD-OCT system was developed for imaging the human limbus. It combines ∼1.5-µm isotropic spatial resolution in ocular tissue and an acquisition rate of 250,000 A-scans per second. The imaging probe was outfitted with two microscope objectives to provide flexibility in the choice of wide field of view and extended depth of focus versus high lateral resolution. The clinical potential of the system was evaluated by imaging subjects with limbal stem cell dysfunction (LSCD; n = 4) and healthy controls (n = 6). Limbus images acquired from the healthy controls showed normal cellular structure of the limbal crypts, palisades of Vogt (POVs), and vasculature of the underlying scleral tissue. Images acquired from the LSCD subjects showed distortions or absence of POVs, invasion of highly scattering conjunctival tissue over the limbal and peripheral corneal epithelium, scarring and thinning of the limbal epithelium, and neovascularization. The combination of high OCT spatial resolution and rapid image acquisition rate allows for in vivo, contactless, volumetric visualization of fine morphological details that could be beneficial for the precise diagnosis and grading of LSCD, planning of treatment, and evaluation of the effectiveness of the treatment approaches. The OCT technology described here could improve the clinical diagnostics and grading of LSCD, preoperative planning, and postoperative evaluation of LSCD subjects, in addition to monitoring the effectiveness of various LSCD treatments.

Three-dimensional energy-controllable focal spot array with extended depth of focus created by pure phase modulation

To produce a three-dimensional (3D) energy-controllable focal spot array with an extended depth of focus (EDOF), we propose a pure phase modulation that combines a two-dimensional (2D) pure phase sinusoidal grating (2D PSG) and a light sword optical element (LSOE). The intensity distribution in the 3D focal field is achieved by both simulation and experiment, exhibiting high energy controllability and EDOF. Additionally, the position of the maximum intensity value of any focusing spot exhibits a rotation characteristic, further indicating that the EDOF can be continuously extended. The transverse spacing between adjacent foci, the shape of the focusing spot, and the intensity distribution are achieved in comparison between simulations and experiments, showing good conformity in two situations of f1/f=10% and 20%. Our proposed method paves a new way to produce the 3D energy-controllable focal spot array with EDOF, laying a solid foundation for its application in various fields, such as 3D photonic crystal structures, 3D luminescence, and 3D optical sensing.

Motion-deblurring ghost imaging for an axially moving target.

For lensless ghost imaging (GI) with thermal light, the axially relative motion constrained in the range of the system's depth of focus (DOF) can still cause image blurring because of a variable magnification. We propose a motion-deblurring GI system with pseudo-thermal light, which can overcome the resolution degradation caused by the axial motion. Both the analytical and experimental results demonstrate that high-resolution GI can be always obtained as long as the target's random motion range is smaller than the system's DOF, without using the prior information of motion estimation. We also show that the system's DOF can be extended by optimizing the geometrical shape of the laser spot on the rotating ground glass disk (RGGD). The imaging performance comparison between the proposed GI system and the corresponding lensless GI system is also discussed. This technique can promote the practical application of GI in the field of moving-target detection and recognition.

The Unusual Seismic Activity from 2021 to 2024 in Eastern Austria: Insights from Seismic Sequences Relocation and Moment Tensor Inversion

ABSTRACT From 2021 to 2024, unusually strong seismic activity, including multiple sequences with five 3.8≤ML≤4.6 shocks, struck the Vienna basin and Mur-Mürz fault systems in Eastern Austria. Three earthquakes (ML 4.6, 4.5, and 3.8) occurred between March and May 2021. These earthquakes were followed by an increase in seismic activity in March 2023, with an ML 4.3 earthquake to the southwest of the 2021 events. In February 2024, an ML 4.5 earthquake occurred 10 km southwest of the ML 4.3 in 2023. We investigate activated faults relying on nonlinear relocations of the seismic sequences and probabilistic moment tensor inversion. The seismic sequences’ temporal evolution indicates a migration of seismic activity and a decrease of focal depths from northeast to southwest, suggesting a potential reactivation of the major fault systems in the region. The joint interpretation of the results shows distinct clusters along fault segments and focal mechanisms that match the region’s complex tectonic activity.

Design concepts for advanced-technology intraocular lenses [Invited

An intraocular lens (IOL) replaces the natural crystalline lens during cataract surgery, and although the vast majority of implants have simple optics, "advanced technology" IOLs have multifocal and extended depth of focus (EDOF) properties. Optical concepts are evaluated here, with image contrast, focal range, and unwanted visual phenomena being the primary concerns. Visual phenomena with earlier bifocal diffractive lenses led to alternative diffractive designs (trifocals, etc.) and also to exploring increasing the depth of focus for monofocal IOLs using refractive methods, where although the defocus range might be more modest, visual phenomena are much less obvious. The designs cover a range of possibilities that might provide the best overall vision for patients with differing motivations, needs, and sensitivity to visual side effects.