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A bifocal interference confocal microscopy system (BICMS) is proposed in which bifocal lenses are used to overcome the tradeoff between high resolution and long working distance, which cannot be achieved simultaneously in devices with small numerical apertures (NAs). In this work, a bifocal lens is introduced in the proposed system to ensure signals (generating the interference) originate from the same point on the surface of the object to be measured. The annular interference region generated by the bifocal lenses can be used to sharpen the width of the central bright spot. This reduces the full width at half maximum for the normalized lateral intensity point spread function, thereby improving the stability, anti-disturbing capabilities, and lateral resolution. A theoretical analysis (using a wavelength of 632.8 nm and an objective NA of 0.1) demonstrated BICMS improved the lateral resolution of the confocal microscope from 2.34 μ m to 1.33 μ m, which is 1.7 times that of a CMS; in the case of NA = 0.2, BICMS improved the lateral resolution of the confocal microscope from 1.24 μ m to 0.92 μ m, which is 1.3 times that of the CMS. As such, the proposed system is bringing the possibility of a wide range of applications for high-resolution confocal microimaging systems. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the effects of exposure energy on the lateral resolution and mechanical strength of dental zirconia manufactured using digital light processing (DLP). MATERIALS AND METHODS. A zirconia suspension and a custom top-down DLP printer were used for in-office manufacturing. The viscosity of the suspension and uniformity of the exposed light intensity were controlled. Based on the exposure energy dose delivered to each layer, the specimens were classified into three groups: low-energy (LE), medium-energy (ME), and high-energy (HE). For each energy group, a simplified molar cube was used to measure the widths of the outline (Xo and Yo) and isthmus (Xi and Yi), and a bar-shaped specimen of the sintered body was tested. A Kruskal-Wallis test for the lateral resolution and one-way analysis of variance for the mechanical strength were performed (α = .05). RESULTS. The zirconia green bodies of the ME group showed better lateral resolution than those of the LE and HE groups (both P < .001). Regarding the flexural strength of the sintered bodies, the ME group had the highest mean value, whereas the LE group had the lowest mean value (both P < .05). The ME group exhibited fewer agglomerates than the LE group, with no distinctive interlayer pores or surface defects. CONCLUSION. Based on these findings, the lateral resolution of the green body and flexural strength of the sintered body of dental zirconia could be affected by the exposure energy dose during DLP. The exposure energy should be optimized when fabricating DLPbased dental zirconia. [ABSTRACT FROM AUTHOR]

We proposed a reduction method of the computational cost for the minimum variance (MV) adaptive beamforming. In the method, a receiving aperture was divided into several sub-apertures, and outputs of the delay-and-sum (DAS) beamformer in the divided sub-apertures were used as inputs of the MV beamformer. Lateral resolutions were evaluated under different division numbers, distances between sub-apertures, and their overlapping ratios in sub-aperture averaging. As a result, the resolution was improved by 44.3% compared with the DAS method at a distance between sub-apertures of 1 mm (5 elements) when dividing the aperture by 5 in sub-aperture averaging. [ABSTRACT FROM AUTHOR]

• The spatial dimensions of nanopatterns are quantified using RBS with a mm-sized ion beam. • The quantification is based on the effect of the pattern on the substrate signal. • The methodology is demonstrated for structures as small as 35 nm. We realize the quantitative determination of the spatial dimensions of nanopatterns using Rutherford backscattering spectrometry (RBS) with a mm-sized ion beam. The methodology is based on the effects of the nanopatterns on the RBS signal from the substrate. We demonstrate the approach with the study of a periodic pattern of 35 nm wide and 75 nm high SiO 2 lines which have a periodicity of 90 nm. We analyse the relation between the features in the experimental spectra and the properties of the nanostructures. Current voxel-based simulation software allows to reproduce many of the experimental observations well. However, we found that the present simulation software inadequately incorporates the effect of the angular spread due to the finite detector size. We propose a method to model the effect more accurately and through this we demonstrate a dramatically improved agreement with the experimental spectra. [ABSTRACT FROM AUTHOR]

Abstract The shallow subsurface defects are difficult to be identified and quantified by ultrasonic time-of-flight diffraction (TOFD) due to the low resolution induced by pulse width and beam spreading. In this paper, Sparse-SAFT is proposed to improve the time resolution and lateral resolution in TOFD imaging by combining sparse deconvolution and synthetic aperture focusing technique (SAFT). The mathematical model in the frequency domain is established based on the l 1 and l 2 norm constraints, and the optimization problem is solved for enhancing time resolution. On this basis, SAFT is employed to improve lateral resolution by delay-and-sum beamforming. The simulated and experimental results indicate that the lateral wave and tip-diffracted waves can be decoupled with Sparse-SAFT. The shallow subsurface defects with a height of 3.0 mm at the depth of 3.0 mm were detected quantitatively, and the relative measurement errors of flaw heights and depths were no more than 10.3%. Compared to conventional SAFT, the time resolution and lateral resolution are enhanced by 72.5 and 56% with Sparse-SAFT, respectively. Finally, the proposed method is also suitable for improving resolution to detect the defects beyond dead zone.

The shallow subsurface defects are difficult to be identified and quantified by ultrasonic time-of-flight diffraction (TOFD) due to the low resolution induced by pulse width and beam spreading. In this paper, Sparse-SAFT is proposed to improve the time resolution and lateral resolution in TOFD imaging by combining sparse deconvolution and synthetic aperture focusing technique (SAFT). The mathematical model in the frequency domain is established based on the l1 and l2 norm constraints, and the optimization problem is solved for enhancing time resolution. On this basis, SAFT is employed to improve lateral resolution by delay-and-sum beamforming. The simulated and experimental results indicate that the lateral wave and tip-diffracted waves can be decoupled with Sparse-SAFT. The shallow subsurface defects with a height of 3.0 mm at the depth of 3.0 mm were detected quantitatively, and the relative measurement errors of flaw heights and depths were no more than 10.3%. Compared to conventional SAFT, the time resolution and lateral resolution are enhanced by 72.5 and 56% with Sparse-SAFT, respectively. Finally, the proposed method is also suitable for improving resolution to detect the defects beyond dead zone. [ABSTRACT FROM AUTHOR]

The high-quality imaging of vascular networks in biological tissue is significant to accurate cancer diagnosis with acoustic-resolution-based photoacoustic microscopy (AR-PAM). So far, many new back-projection (BP) models have been proposed to improve the image quality of AR-PAM in the off-focal regions. However, many essential arguments are still open regarding the effectiveness of these methods. To settle these remaining questions and explore the potential and adaptability of these BP methods in vascular network imaging, we conducted extensive simulations of a complex vascular network based on a GPU-based data generation framework. Results show that the SAFT-CF algorithm effectively improves the reconstructed image but mainly highlights point targets. In contrast, the STR-BP algorithm can effectively balance the computational cost, signal-to-noise ratio (SNR), and consistency of target intensity for both point and line targets. Results proved that data interpolation for more A-line numbers would not improve the image quality due to information lost. Thus, the detector number in the scan should be sufficiently large. Results also showed that the STR-BP method improved the PSNR of the image by 4.7 to 7.5 dB, which helps the image withstand a noise level of higher than 25%. The proposed simulation framework and the intuitive findings will guide the design of AR-PAM systems and image reconstruction. [ABSTRACT FROM AUTHOR]

Acoustic-resolution photoacoustic microscopy (AR-PAM) is a promising imaging modality that renders images with ultrasound resolution and extends the imaging depth beyond the optical ballistic regime. To achieve a high lateral resolution, a large numerical aperture (NA) of a focused transducer is usually applied for AR-PAM. However, AR-PAM fails to hold its performance in the out-of-focus region. The lateral resolution and signal-to-noise ratio (SNR) degrade substantially, thereby leading to a significantly deteriorated image quality outside the focal area. Based on the concept of the synthetic-aperture focusing technique (SAFT), various strategies have been developed to address this challenge. These include 1D-SAFT, 2D-SAFT, adaptive-SAFT, spatial impulse response (SIR)-based schemes, and delay-multiply-and-sum (DMAS) strategies. These techniques have shown progress in achieving depth-independent lateral resolution, while several challenges remain. This review aims to introduce these developments in SAFT-based approaches, highlight their fundamental mechanisms, underline the advantages and limitations of each approach, and discuss the outlook of the remaining challenges for future advances.

ISO 18516:2019 Surface chemical analysis—Determination of lateral resolution and sharpness in beam‐based methods with a range from nanometres to micrometres revises ISO 18516:2006 Surface chemical analysis—Auger electron spectroscopy and X‐ray photoelectron spectroscopy—Determination of lateral resolution. It implements three different methods delivering parameters useful to express the lateral resolution: (1) the straight edge method, (2) the narrow line method and (3) the grating method. The theoretical background of these methods is introduced in ISO/TR 19319:2013 Surface chemical analysis—Fundamental approaches to determination of lateral resolution and sharpness in beam‐based methods. The revised International Standard ISO 18516 delivers standardized procedures for the determination of the (1) effective lateral resolution by imaging of square‐wave gratings, the (2) lateral resolution expressed as the parameter D12–88 characterizing the steepness of the sigmoidal edge spread function (ESF) determined by imaging a straight edge and (3) the lateral resolution expressed as the full width of half maximum of the line spread function (LSF), wLSF, determined by imaging a narrow line. The last method also delivers information on the shape of the LSF, which characterizes an individual imaging instrument. Finally, the implementation of all three standardized methods in the field of imaging laboratory X‐ray photoelectron spectroscopy (XPS) is shortly presented. This part of the letter is based on the use of a new test sample developed at ETH Zurich, Switzerland. This test sample displays a micrometre scaled pattern motivated by the resolving power of recent imaging XPS instruments. [ABSTRACT FROM AUTHOR]

A creative engineer tends to understand the principles and phenomena not only based on mathematical physics but also by intuition. Author has picked up several topics among such principles and phenomena in the area of medical ultrasound and challenges to explain them intuitively in this article. The chosen topics are the lateral resolution, Doppler blood flow measurement, a piezoelectric element, ultrasonic absorption by biological tissues, and intensive/extensive variables. Author hopes that the presented intuitive explanation will help the readers to enhance their creativity as an engineer [ABSTRACT FROM AUTHOR]

The lateral resolution in microscopic imaging generally depends on both, the wavelength of light and the numerical aperture of the microscope objective lens. To quantify the lateral resolution Ernst Abbe considered an optical grating illuminated by plane waves. In contrast, the Rayleigh criterion holds for two point sources or point scatterers separated by a lateral distance, which are supposed to emit spherical waves. A portion of each spherical wave is collected by the objective lens and results in an Airy disc corresponding to a diffraction limited intensity point spread function (PSF). If incoherent illumination is employed the intensity PSFs related to different scatterers on an object are added resulting in the well-known Rayleigh resolution criterion. In interference microscopy instead of the intensity the electric field scattered or diffracted by an object will be affected by the transfer function of the optical imaging system. For a reflective object the lateral resolution of an interference microscope can be again characterized by the Abbe limit if the object under investigation is a grating. However, if two irregularities on a flat surface are being imaged the resolution no longer obeys the Rayleigh criterion. Instead, it corresponds to an optical system with an annular aperture and thus surpasses the prediction given by the Rayleigh criterion. This holds true for both, amplitude as well as phase objects, as it will be elucidated in this study by theoretical considerations, simulation results and an experimental proof of principle.

Stimulated emission depletion (STED) microscopy allows high lateral and axial resolution, long term imaging in living cells. Here we review recent technical advances in STED microscopy, with emphasis on resolution and measurement range of XYZt four dimensions. Different STED technical advances and novel STED probes are discussed with their respective application in biological subcellular imaging. This review may serve as a practical guide for choosing a suitable approach to the advanced STED super‐resolution imaging. [ABSTRACT FROM AUTHOR]

Copyright of Hydrographic Surveying & Charting / Haiyang Cehui is the property of Hydrographic Surveying & Charting Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An amplitude-dependent downshift in the fundamental wave spectrum of a propagating ultrasonic pulse caused by non-linear wave propagation is described. The effects of non-linearity and the associated downshift on spatial resolution are also studied. The amounts of downshift and spatial resolution are extracted from the numerically simulated beam profile based on the KZK equation. Results for a 25-MHz transducer reveal that non-linear effects can lead to 58% additional downshift in the centre frequency of a pulse compared with a linear case with downshift caused only by attenuation. This additional downshift causes about 50% degradation in axial resolution. However, as the beam becomes narrower from the non-linear effects, the overall effect of non-linearity still leads to improved lateral resolution (≤26%). Therefore, as non-linearity increases with wave pressure, it is concluded that the increase in source pressure improves lateral resolution and degrades axial resolution. [ABSTRACT FROM AUTHOR]

Purpose: In circular‐scanning‐based photoacoustic tomography (PAT), the effect of finite transducer aperture has not been effectively resolved. The goal of this paper is to propose a practical reconstruction method that accounts for the finite transducer aperture to improve the lateral resolution. Methods: We for the first time propose to calculate the spatial‐temporal response (STR) of the employed finite‐sized transducer in a forward model, and then compensate the time delay and the directional sensitivity of the transducer in the framework of the back‐projection method. Both simulation and phantom experiments were carried out to evaluate the lateral resolution improvement with the proposed method. The performance of this new method for imaging complicated targets was also assessed by calculating the mean image gradient. Results: Simulation results showed that with this new method the lateral resolution for off‐center targets can be as good as that for the center targets. Phantom experimental results showed that this new method can improve the lateral resolution more than two times for a point target about 5 mm far from the rotation center. Phantom experimental results also showed that many blurred fine structures of a piece of leaf veins at the off‐center regions were well restored with the new method, and the mean image gradient improved about 1.3 times. Conclusion: The proposed new method can effectively account for the effect of finite transducer aperture for circular‐scanning‐based PAT in homogenous acoustic media. This new method also features its robustness and computational efficiency, so that it is a worthy replacement to the conventional back‐projection algorithm in circular‐scanning‐based PAT. This new method can be of great importance to the design of circular‐scanning or spherical‐scanning‐based PAT systems. [ABSTRACT FROM AUTHOR]

Abstract Interference signals in coherence scanning interferometry at high numerical apertures and narrow bandwidth illumination are spectrally broadened. This enables phase analysis within a spectral range much wider than the spectral distribution of the light emitted by the light source. Consequently, different surface features can be resolved depending on the wavelength used for phase analysis of the interference signals. In addition, the surface topography itself affects the spectral composition of interference signals in different ways. Signals related to tilted surfaces or step height structures show special spectral characteristics. Thus, spectral amplitude and phase analysis enables a better understanding of the underlying physical mechanisms and gives hints how to improve the measurement accuracy.

The high-quality imaging of vascular networks in biological tissue is significant to accurate cancer diagnosis with acoustic-resolution-based photoacoustic microscopy (AR-PAM). So far, many new back-projection (BP) models have been proposed to improve the image quality of AR-PAM in the off-focal regions. However, many essential arguments are still open regarding the effectiveness of these methods. To settle these remaining questions and explore the potential and adaptability of these BP methods in vascular network imaging, we conducted extensive simulations of a complex vascular network based on a GPU-based data generation framework. Results show that the SAFT-CF algorithm effectively improves the reconstructed image but mainly highlights point targets. In contrast, the STR-BP algorithm can effectively balance the computational cost, signal-to-noise ratio (SNR), and consistency of target intensity for both point and line targets. Results proved that data interpolation for more A-line numbers would not improve the image quality due to information lost. Thus, the detector number in the scan should be sufficiently large. Results also showed that the STR-BP method improved the PSNR of the image by 4.7 to 7.5 dB, which helps the image withstand a noise level of higher than 25%. The proposed simulation framework and the intuitive findings will guide the design of AR-PAM systems and image reconstruction.

The lateral resolution is one of the most important hallmarks for evaluating the imaging performance of a confocal Raman microscope (CRM). A method based on the resolution test chart for testing the lateral resolution of the CRM was proposed. The test imaging target comprised a polished silicon substrate coated with a thin metallic pattern, which provided a high contrast and negligible edge effects. By using a single-bar target instead of a conventional three-bar target, quantitative measurements of the lateral resolution of the CRM were possible. Single-bar targets with different widths were used to test a CRM with a nominal lateral resolution of approximately 1 μm. The response of the CRM to the single-bar target was studied further with a theoretical model, and the relationship between the Michelson contrast of the response function and the lateral resolution was investigated. Finally, the method used to calculate the lateral resolution was described and tested and shown to have a relative repeatability of only 5.6%, which is ideal for resolution testing. Overall, our experimental results showed excellent agreement with simulation results and proved that the single-bar target method was capable of measuring the lateral resolution of CRMs with high accuracy, efficiency and reproducibility. [ABSTRACT FROM AUTHOR]

The goal of this work is to compare experimentally achievable resolution limits of three different optical microscopy techniques in chiral nematic liquid crystals: (i) standard optical polarisation microscopy, (ii) confocal optical microscopy using fluorescently labelled liquid crystal and (iii) Stimulated Emission Depletion (STED) microscopy using custom synthesised fluorescent dyes. The microscopy experiments on micrometre thin LC samples reveal that the lateral resolution better than ~90 nm can be achieved using STED technique in thin layers of liquid crystals. The standard optical microscopy with index matching between the objective and the sample cover glass in combination with short-wavelength narrow-band optical illumination is quite competitive to STED technique and optical details as small as ~150 nm could be resolved using aberration limited microscope. [ABSTRACT FROM AUTHOR]

New functional interfaces with controlled heterogeneity having a lateral resolution in the nanometre range are of great importance for many promising applications. One of the easiest ways to produce such patterned interfaces is the deposition of insoluble amphiphilic monolayers on the substrate surface, according to the well-known approach developed by Langmuir and Blodgett. Under some specific conditions, deposited monolayers can form not homogeneous layers, but well-controlled structured films. Such structured films are a result of monolayer interaction with the substrate surface and instabilities developed within the receding menisci. In particular, regular stripe patterns can be obtained by deposition of charged fatty acid monolayers, which are formed due to contact line auto-oscillations during the deposition process. In the previous studies, symmetrical systems were considered, where the monolayer is deposited onto substrate surface already covered by the previously deposited similar monolayer. In this article, we consider asymmetrical configurations, where the monolayer is deposited onto a bare substrate surface. As shown, the similar mechanism of structure formation is realized also in this case, but for significantly larger deposition rates. [ABSTRACT FROM AUTHOR]

Copyright of Hydrographic Surveying & Charting / Haiyang Cehui is the property of Hydrographic Surveying & Charting Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abdominal imaging suffers from a particularly difficult acoustic environment—targets are located deep and overlying tissue layers with varying properties generate acoustic clutter. Increasing array size can overcome the penetration and lateral resolution problems in ideal conditions, but how the impact of clutter scales with increasing array extent is unknown and may limit the benefits in vivo. Previous ex vivo experimental work showed the promise of large arrays but was technically limited to a length of 6.4 cm and to only partial sampling of the array elements. We present an extension of those studies using the Fullwave simulation tool to create a 10 cm $\times 2$ cm matrix array with full lateral element sampling. We used a numerical model of the abdomen based on the maps of tissue acoustical properties and found that propagation through the modeled abdominal layers generated on average 25.4 ns of aberration and 0.74 cm of reverberation clutter across the array extent. Growing the full aperture from 2 to 10 cm improved contrast by 8.6 dB and contrast-to-noise ratio by 22.9% in addition to significantly improving target resolution. Alternative array strategies that may be useful for implementation—mismatched aperture sizes or a swept synthetic aperture—also produced improved quality with growing aperture size. These results motivate the development of larger diagnostic imaging arrays for the purpose of high-resolution imaging in challenging environments. [ABSTRACT FROM AUTHOR]

A broadband generalized sidelobe canceler (Broadband-GSC) application for near-field beamforming is proposed. This approach is implemented in the wavelet domain. Broadband-GSC provides a set of complex, adapted apodization weights for each wavelet subband. The proposed method constrains interference and noise signal to improve the lateral resolution with only one single emission. Performance of the proposed beamforming is tested on simulated data obtained with Field II. Experiments have proved that the new beamforming can significantly increase the image quality compared with delay-and-sum (DAS) and synthetic aperture (SA). Imaging of scattering points show that Broadband-GSC improves the lateral resolution by 43.2% and 58.0% compared with SA and DAS, respectively. Meanwhile，Broadband-GSC reduces the peak sidelobe level by 11.6 dB and 26.4 dB compared with SA and DAS, respectively. Plane wave emission experiment indicates that Broadband-GSC can improve the lateral resolution by 44.2% compared with DAS. Furthermore, the new beamforming introduces the possibility for higher frame-rate and higher investigation depth with increased lateral resolution. [ABSTRACT FROM AUTHOR]

We report a Fresnel lens based spectral domain optical coherence tomography (SDOCT) setup to overcome the trade-off between lateral resolution and focusing depth which is one of the main problems for OCT system. We demonstrated the feasibility of the Fresnel lens based SDOCT system by measuring the lateral resolution at different depth positions and compared these results with that obtained by conventional SDOCT illuminated with a light source of a central wavelength of 840 nm and a bandwidth of 50 nm. These results indicated that the Fresnel lens based SDOCT can maintain a constant lateral resolution (~ 6.2 μm or better in our system) over a depth of ~ 2 mm which is nearly 1.2 mm larger than conventional SDOCT. This advantage of the proposed method is very useful for SDOCT based imaging technique applied in the clinical application. [ABSTRACT FROM AUTHOR]

Assessing the instrumental resolution of confocal Raman microscopy is a key aspect in 2D or 3D imaging in various applications. An important issue in this regard is the experimental measurement of a lateral resolution for the Raman microscope system. Several methods have been proposed for the resolution measurement in fluorescence microscopy; however, these methods have rather limited applications. In this paper, we demonstrate an experimental approach for evaluating the lateral resolution with well‐defined nano‐patterns in confocal Raman microscopy and discuss the factors that can improve estimation of instrumental resolution. This study contributes to the further understanding of the assessment of instrumental resolution in confocal scanning Raman microscopy. [ABSTRACT FROM AUTHOR]

The use of oversampling in MALDI (matrix-assisted laser desorption/ionization) imaging mass spectrometry (IMS) to improve lateral resolution is a common practice. However, its application is still controversial and recent studies reported a spot size–dependent change in the relative intensity of the spectra. Previously, using oversampling, we described the lipidome of the human colon epithelium, a 20–30 μm wide cell monolayer; even assessing the changes occurring within this monolayer associated with complex biological processes. Interestingly, the K-means analysis of those experiments unveiled the presence of a third epithelial cluster that anatomically matched the nuclei position. Taking into account the nucleus size (9–12 μm of diameter) and its distinctive lipidome, we decided to test whether this cluster was really of nuclear origin. Hence, the spectra obtained directly from tissue sections were compared with those recorded from the nuclei isolated from colon biopsies. The highest correlation coefficient was obtained when comparing the spectrum of the isolated nuclei with that of the tissue nuclear cluster, demonstrating the successful identification of the nuclear lipidome in the MALDI-IMS experiments run using oversampling and a lateral resolution of 10 μm/pixel. Importantly, it was established that phosphatidylinositol 38:4 nuclear levels remained stable along the colon crypt. That is, it mimicked neither the regular decrease observed in the epithelium nor the regular increase observed in the stroma, eliminating the chance of inter-pixel contamination. Altogether, besides confirming the usefulness of the oversampling technique, these results strongly reinforce the pivotal role IMS may have in promising fields such as single-cell analysis. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this paper is to present a more convenient and practical alternate way of increasing the lateral discrete array sampling while using a typical λ pitch linear array transducer at receive for photoacoustic tomography (PAT) application. Methods: We have employed a linear translation-based approach, in which the array transducer is translated by sub-pitch amount to create an augmented RF frame data having denser lateral spatial sampling. The denser λ/2 and λ/4 pitch data were reconstructed and compared against conventional λ pitch reconstructed PAT image using simulation and tissue mimicking phantom experiments in terms of improvements in resolution and contrast. Results: The results from experiments demonstrate a 34.48% improvement in lateral resolution (LR), measured in terms of full-width at half-maximum of the lateral profile of point spread function, and a maximum of 7-dB improvement in contrast is achieved while using a λ/2-pitch configuration when compared to the conventional λ-pitch configuration. Conclusion: It was demonstrated that λ/2- and λ/4-pitch configurations result in better LR and contrast than λ-pitch configuration. Significance: Based on the results obtained, the proposed method has the potential to serve as an easy-to-integrate and simple way of achieving better image quality without requiring to increase the system complexity with existing transducer array probe technology in regular clinical scanners. [ABSTRACT FROM AUTHOR]

In optical coherence tomography (OCT), axial and lateral resolutions are determined by the source coherence length and numerical aperture of the sampling lens, respectively. While axial resolution can be improved using a broadband light source, there is a trade-off between lateral resolution and focus depth when conventional optical elements are used. In this paper, we report on the incorporation of an axicon lens into the sample ann of the interferometer to overcome this limitation. Using an axicon lens with a top angle of 160 degrees, 10 μm or better lateral resolution is maintained over a focus depth of at least 6 mm. In addition to high lateral resolution, the focusing spot intensity is approximately constant over the whole focus depth.

In optical coherence tomography (OCT), axial and lateral resolutions are determined by the source coherence length and numerical aperture of the sampling lens, respectively. While axial resolution can be improved using a broadband light source, there is a trade-off between lateral resolution and focus depth when conventional optical elements are used. In this paper, we report on the incorporation of an axicon lens into the sample ann of the interferometer to overcome this limitation. Using an axicon lens with a top angle of 160 degrees, 10 μm or better lateral resolution is maintained over a focus depth of at least 6 mm. In addition to high lateral resolution, the focusing spot intensity is approximately constant over the whole focus depth.

Abstract Confocal microscopy is widely used, but its resolution is limited. To improve confocal microscopy resolution, tangentially polarized illumination light and image subtraction are studied. Tangentially polarized light or vortex phase modulated tangentially polarized light are used as confocal microscopy illumination light. The effective point spread function difference of the confocal microscopy using tangentially polarized light and using vortex phase modulated tangentially polarized light is got first. The full width at half maximum of the point spread function difference is smaller. Simulation shows that the resolution of the confocal microscopy using tangentially polarized light illumination and image subtraction is increased by 19.9% compared with ordinary circularly polarized light. When compared with confocal microscopy using vortex phase modulated tangentially polarized light, simulation and fluorescence beads imaging experiment show that the resolution of the aforementioned confocal microscopy is improved by 13.6% and 11.2%. In conclusion, the resolution of confocal microscopy using tangentially polarized light illumination and image subtraction could be improved. Compared with other resolution enhancement technologies, this method is much simpler and does not need strong lasers. Highlights • We propose a method to improve confocal microscopy resolution by tangentially light illumination and image subtraction. • The resolution of this method is enhanced by 19.9% compared with ordinary confocal microscopy. • Compared with other resolution enhancement technologies, this method is much simpler and does not need strong lasers. [ABSTRACT FROM AUTHOR]

Minimum Variance (MV) beamforming is known to improve the lateral resolution of ultrasound images and enhance the separation of isolated point scatterers. This paper aims to evaluate the adaptive beamformer’s performance with flowing microbubbles (MBs) which are relevant to super-resolution ultrasound imaging. Simulations using point scatterer data from single emissions were complemented by an experimental investigation performed using a capillary tube phantom and the Synthetic Aperture Real-time Ultrasound System (SARUS). The MV performance was assessed by the minimum distance that allows the display of two scatterers positioned side-by-side, the lateral Full-Width-at-Half-Maximum (FWHM), and the Peak-Sidelobe-Level (PSL). In the tube, scatterer responses separated by down to $196~\mu \text{m}$ (or $1.05\lambda $) were distinguished by the MV method, while the standard Delay-And-Sum (DAS) beamformers were unable to achieve such separation. Up to ninefold FWHM decrease was also measured in favor of the MV beamformer for individual echoes from MBs. The lateral distance between two scatterers impacted on their FWHM value, and additional differences in the scatterers’ axial or out-of-plane position also impacted on their size and appearance. The simulation and experimental results were in agreement in terms of lateral resolution. The point scatterer study showed that the proposed MV imaging scheme provided clear resolution benefits compared to DAS. Current super-resolution methods mainly depend on DAS beamformers. Instead, the use of the MV method may provide a larger number of detected, and potentially better localized, MB scatterers. [ABSTRACT FROM AUTHOR]

Abstract In laser-ablation spark-induced breakdown spectroscopy (LA-SIBS), the discharge channel is an important factor to affect both analytical sensitivity and lateral resolution on the sample surface. In order to study this effect, a gated pulsed high-voltage power supply was selected as the power source of the spark discharge, the dependence of the discharge channel on the time delay between the high voltage pulse and the laser pulse was studied in this work. It was demonstrated that under suitable laser pulse energy and geometrical arrangement of the electrodes, it was possible to change V-shape discharge to parallel discharge by increasing this time delay. In the V-shape discharge, the spark discharge could ablate more samples and increase the diameters and depths of the craters; however, in the parallel discharge, the spark discharge hardly ablated new samples, to make sure that the spatial resolution in LA-SIBS was only determined by the laser ablation. Under parallel discharge, the intensity of the atomic emission of the plasma decreases with the increasing of time delay but increases with the increasing of the discharge voltage. 4–10 folds enhancement factors have been achieved in the detection limits of the analytes in the employed targets under current experimental conditions. It is suggested that spark discharge under external trigger mode should be selected to realize parallel discharge if high spatial resolution elemental analysis of solid samples is required. Graphical abstract Unlabelled Image Highlights • A gated pulsed HV power supply was used as excitation source of the spark discharge. • Parallel discharge was realized by increasing time delay between HV and laser pulses. • No samples could be ablated by the spark discharge under parallel discharge mode. • Obvious signal enhancement has been observed under parallel discharge mode. • 4–10 folds enhancement factors in LOD of the analytes have been achieved currently. [ABSTRACT FROM AUTHOR]

• Below 10 nm lateral resolutions in nuclear microprobes are achieved by the near-axis STIM technology, as demonstrated here for H 2 +. • Monolayer depth resolution is reached by the double-fragment scattering (DFS) technology. • The ionization of a H 2 + by a single layer graphene is demonstrated experimentally. • Single and few layers of freestanding graphene can be differentiated by a nuclear microprobe. The spatial resolution plays a crucial role in determining the performance of a nuclear microprobe. However, the formation of spatial resolutions below 10 nm remains a challenge in nuclear microprobes. Here, we propose novel technologies (near-axis scanning transmission ion microscopy and double-fragment scattering) utilizing molecular ions to address this challenge and demonstrate a H 2 + molecular beam with 6.0 × 10 nm2 lateral resolution and monolayer thickness resolution respectively. Using the improved nuclear microprobe, we directly demonstrate that the ionization of a H 2 + can be efficiently achieved using one single layer graphene, and also that single and few layers of freestanding graphene can be clearly differentiated and identified. The precise control of fast molecular ions at sub-10 nm scales has the potential to unlock new avenues of applications. [ABSTRACT FROM AUTHOR]

A broadband generalized sidelobe canceler (Broadband-GSC) application for near-field beamforming is proposed. This approach is implemented in the wavelet domain. Broadband-GSC provides a set of complex, adapted apodization weights for each wavelet subband. The proposed method constrains interference and noise signal to improve the lateral resolution with only one single emission. Performance of the proposed beamforming is tested on simulated data obtained with Field II. Experiments have proved that the new beamforming can significantly increase the image quality compared with delay-and-sum (DAS) and synthetic aperture (SA). Imaging of scattering points show that Broadband-GSC improves the lateral resolution by 43.2% and 58.0% compared with SA and DAS, respectively. Meanwhile，Broadband-GSC reduces the peak sidelobe level by 11.6 dB and 26.4 dB compared with SA and DAS, respectively. Plane wave emission experiment indicates that Broadband-GSC can improve the lateral resolution by 44.2% compared with DAS. Furthermore, the new beamforming introduces the possibility for higher frame-rate and higher investigation depth with increased lateral resolution.

A mathematical model of cylindrical shaped plane-ended scanning Kelvin probe output signal is proposed considering the case of an infinite plane sample's surface with local defects represented by dot charges. Modeling results were obtained for the case of two closely situated dot charges anddifferent combinations of scanning Kelvin probe tip's diameter and sample-to-probe gap. It was found that the most effective way to improve the lateral resolution of a scanning Kelvin probe is to reduce the sample-to-probe gap in line with the reduction of sensor's vibration amplitude.

Purpose: This study aims to evaluate the effects of exposure energy on the lateral resolution and mechanical strength of dental zirconia manufactured using digital light processing (DLP)., Materials and Methods: A zirconia suspension and a custom top-down DLP printer were used for in-office manufacturing. The viscosity of the suspension and uniformity of the exposed light intensity were controlled. Based on the exposure energy dose delivered to each layer, the specimens were classified into three groups: low-energy (LE), medium-energy (ME), and high-energy (HE). For each energy group, a simplified molar cube was used to measure the widths of the outline ( X o and Y o ), and a bar-shaped specimen of the sintered body was tested. A Kruskal-Wallis test for the lateral resolution and one-way analysis of variance for the mechanical strength were performed (α = .05).X i and Y i ), and a bar-shaped specimen of the sintered body was tested. A Kruskal-Wallis test for the lateral resolution and one-way analysis of variance for the mechanical strength were performed (α = .05)., Results: The zirconia green bodies of the ME group showed better lateral resolution than those of the LE and HE groups (both P < .001). Regarding the flexural strength of the sintered bodies, the ME group had the highest mean value, whereas the LE group had the lowest mean value (both P < .05). The ME group exhibited fewer agglomerates than the LE group, with no distinctive interlayer pores or surface defects., Conclusion: Based on these findings, the lateral resolution of the green body and flexural strength of the sintered body of dental zirconia could be affected by the exposure energy dose during DLP. The exposure energy should be optimized when fabricating DLP-based dental zirconia., (© 2023 The Korean Academy of Prosthodontics.)