High-performance Imaging Research Articles

Convolutional Neural Network-Assisted Photoresist Formulation Discriminator Design of a Contact Layer for Electron Beam Lithography.

The photoresist formulation is closely related to the material properties, and its composition content determines the lithography imaging quality. To satisfy the process requirements, imaging verification of extensive formulations is required through lithography experiments. Identifying photoresist formulations with a high imaging performance has become a challenge. Herein, we develop a formulation discriminator of a metal oxide nanoparticle photoresist for a contact layer applied to electron beam lithography. This discriminator consists of convolutional neural network photoresist imaging and formulation classification models. A photoresist imaging model is adopted to predict the contact width of variable formulations, while a formulation classification model is used to classify formulations according to relative local critical dimension uniformity (RLCDU). The verification results indicate that the discriminator can accurately recognize photoresist formulations that simultaneously meet the conditions of contact width and RLCDU, and its feasibility has been demonstrated, providing a valuable reference for the preparation of photoresist materials.

Endogenous Messenger RNA-Stimulative Self-Enhanced Orthogonal Catalytic DNA Nanomachine under Near-Infrared Light Mediation for High-Performance Imaging in Living Biosamples

Endogenous Messenger RNA-Stimulative Self-Enhanced Orthogonal Catalytic DNA Nanomachine under Near-Infrared Light Mediation for High-Performance Imaging in Living Biosamples

Hyperbranched Polymeric 19F MRI Contrast Agents with Long T2 Relaxation Time Based on β-Cyclodextrin and Phosphorycholine.

19F magnetic resonance imaging (19F MRI) is gaining attention as an emerging diagnostic technology. Effective 19F MRI contrast agents (CAs) for in vivo applications require a long transverse (or spin-spin) relaxation time (T2), short longitudinal (or spin-lattice) relaxation time (T1), high fluorine content, and excellent biocompatibility. Here, we present a novel hyperbranched polymeric 19F MRI CA based on β-cyclodextrin and phosphorylcholine. The influence of the branching degree and fluorine content on T2 was thoroughly investigated. Results demonstrated a maximum fluorine content of 11.85% and a T2 of 612 ms. This hyperbranched polymeric 19F MRI CA exhibited both great biocompatibility against cells and organs of mice and high-performance imaging capabilities both in vitro and in vivo. The research provides positive insights into the synthesis strategies, topological design, and selection of fluorine tags for 19F MRI CAs.

High-Performance and Low-Noise Trantenna Sub-THz Imager With Low-Impedance Analog Buffers and Reset Switch

High-Performance and Low-Noise Trantenna Sub-THz Imager With Low-Impedance Analog Buffers and Reset Switch

The Tobin Coefficient: A Relevant Photodetector Performance Metric for IR Imaging

The well-known Rule07 is a simple thus efficient way to compare available technologies for IR imaging detectors in terms of dark current. The noise is then often estimated using a shot noise approximation on the dark current. Both II–VI and III–V communities use this rule of thumb as a reference for well-performing IR photodiodes. For HOT applications, a dark current close to this rule07 is considered a necessary condition but not a sufficient one to obtain a high-performance IR imager. Indeed, when limited by shot noise, rule07 describes well the noise behavior of the considered device. However, when considering low-frequency noise, it fails to describe the expected performances. In this paper, we focus on another figure-of-merit, dedicated to detector low-frequency noise rather than dark current. Systemic 1/f noise investigation in an IR detector was first reported by Tobin et al. in 1980. There is today a relative consensus on the fact that measured 1/f noise is proportional to the dark current. The ratio between the amplitude of the 1/f noise and the dark current of the same devices may therefore be used as a figure-of-merit for a given technology. This ratio (called the Tobin factor αT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\alpha }_{\ ext{T}}$$\\end{document}) therefore appears adequate to compare different technologies as a figure-of-merit qualifying 1/f noise properties. This dimensionless ratio can also be very useful for optimizing a particular technology or process. However, in order to be relevant, this figure-of-merit must be estimated carefully as it appears, for instance, pixel pitch-dependent. Different examples of Tobin coefficient extraction are presented in this paper. We show that, depending on the technologies, the values of the Tobin coefficient can spread over several orders of magnitude. However, only low values result in high-quality IR imagers. Today, the best results we obtained show that αT=10-5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\alpha }_{\ ext{T}}={10}^{-5}$$\\end{document} is a state-of-art value to be compared with.

The added value of a new high-performance ring-gantry CBCT imaging system for prostate cancer patients

Background and purposeA novel Cone-Beam Computed Tomography (CBCT) named HyperSight provides superior CBCT image quality compared to conventional ring gantry CBCT imaging, and it is suitable for dose calculations for prostate cancer, but it comes with considerable additional costs. The aim of this study was to determine the added value of HyperSight CBCT imaging compared to conventional CBCT imaging in terms of organ visibility in the male pelvic region. Materials and methodsTwenty prostate cancer patients were included in this prospective clinical study. For each patient three CBCT pairs, consisting of HyperSight and conventional CBCT scans acquired on consecutive days, were included. CBCT scans were evaluated by four observers in terms of visibility of the prostate, bladder, rectum and seminal vesicles. Visibility was scored on a 1-to-5 scale and by annotating axial slices where the organs were hard to delineate. Lastly, observers indicated whether the CBCT scans were of sufficient quality for an online adaptive radiation therapy workflow. ResultsAll four organs were better visible on HyperSight CBCT scans compared to conventional CBCT scans. The mean visibility scores increased from 3.1 to 4.5 on a 1––5 scale of and the mean number of annotated slices reduced from 4.5 to 1.1. 99% Of the HyperSight CBCT scans were considered suitable for an online adaptive workflow vs 25–83% for the conventional CBCT scans. ConclusionHyperSight CBCT scans yielded a visibility of prostate, bladder, rectum and seminal vesicles comparable to planning CT scans and, can replace a repeat planning CT scan in case of anatomical changes requiring a new treatment plan.

Bottom-up construction of low-dimensional perovskite thick films for high-performance X-ray detection and imaging

Quasi-two-dimensional (Q-2D) perovskite exhibits exceptional photoelectric properties and demonstrates reduced ion migration compared to 3D perovskite, making it a promising material for the fabrication of highly sensitive and stable X-ray detectors. However, achieving high-quality perovskite films with sufficient thickness for efficient X-ray absorption remains challenging. Herein, we present a novel approach to regulate the growth of Q-2D perovskite crystals in a mixed atmosphere comprising methylamine (CH3NH2, MA) and ammonia (NH3), resulting in the successful fabrication of high-quality films with a thickness of hundreds of micrometers. Subsequently, we build a heterojunction X-ray detector by incorporating the perovskite layer with titanium dioxide (TiO2). The precise regulation of perovskite crystal growth and the meticulous design of the device structure synergistically enhance the resistivity and carrier transport properties of the X-ray detector, resulting in an ultrahigh sensitivity (29721.4 μC Gyair−1 cm−2) for low-dimensional perovskite X-ray detectors and a low detection limit of 20.9 nGyair s−1. We have further demonstrated a flat panel X-ray imager (FPXI) showing a high spatial resolution of 3.6 lp mm−1 and outstanding X-ray imaging capability under low X-ray doses. This work presents an effective methodology for achieving high-performance Q-2D perovskite FPXIs that holds great promise for various applications in imaging technology.

Hybrid design scheme for enabling large-aperture diffractive achromat imaging

Diffractive achromats (DAs) combined with image processing algorithms offer a promising lens solution for high-performance ultra-thin imagers. However, the design of large-aperture DAs that align seamlessly with image processing algorithms remains challenging. Existing sequential methods, which prioritize focusing efficiency in DAs before selecting an algorithm, may not achieve a satisfactory match due to an ambiguous relationship between efficiency and final imaging quality. Conversely, image-quality-oriented end-to-end design often entails high computational complexity for both front-end optics and back-end algorithms, impeding the development of large-aperture designs. To address these issues, we present a hybrid design scheme that begins with end-to-end optimization of the DA with the simplest image processing algorithm, i.e., Wiener filter, significantly reducing the back-end complexity. Subsequently, we apply complex algorithm fine-tuning to further enhance image quality. We validate this hybrid design scheme through extensive investigations on several DA imagers. Our results demonstrate a reduction in memory requirement by approximately 50% while maintaining a high imaging quality with a reasonably large aperture. As a case in point, we simulated a DA imager with a 25 mm diameter aperture. Furthermore, our hybrid design scheme provides two crucial insights. Firstly, we find no strong linear correlation between focusing efficiency and imaging quality, which challenges the conventional understanding. Secondly, we establish a prediction formula for imaging quality, benefiting from the hybrid design scheme.

High-performance laser speckle contrast image vascular segmentation without delicate pseudo-label reliance

Laser speckle contrast imaging (LSCI) is a noninvasive, label-free technique that allows real-time investigation of the microcirculation situation of biological tissue. High-quality microvascular segmentation is critical for analyzing and evaluating vascular morphology and blood flow dynamics. However, achieving high-quality vessel segmentation has always been a challenge due to the cost and complexity of label data acquisition and the irregular vascular morphology. In addition, supervised learning methods heavily rely on high-quality labels for accurate segmentation results, which often necessitate extensive labeling efforts. Here, we propose a novel approach LSWDP for high-performance real-time vessel segmentation that utilizes low-quality pseudo-labels for nonmatched training without relying on a substantial number of intricate labels and image pairing. Furthermore, we demonstrate that our method is more robust and effective in mitigating performance degradation than traditional segmentation approaches on diverse style data sets, even when confronted with unfamiliar data. Importantly, the dice similarity coefficient exceeded 85% in a rat experiment. Our study has the potential to efficiently segment and evaluate blood vessels in both normal and disease situations. This would greatly benefit future research in life and medicine.

Fast and high-responsivity MoS2/MoSe2 heterostructure photodetectors enabled by van der Waals contact interfaces

Two-dimensional (2D) materials are ideal candidates for building optoelectronic devices, owing to their fascinating photoelectric properties. However, most photodetectors based on individual 2D materials face difficulties in achieving both high responsivity and fast response. In this paper, we have fabricated high-quality vertically stacked MoS2/MoSe2 van der Waals (vdW) heterostructures using dry transfer method. The strong built-in electric field at the interface of type II heterostructure effectively facilitates the separation of photogenerated carriers. The vdW contact between channel material and transferred metal electrode effectively avoids the introduction of defects. These methods effectively enhance the performance of hybrid devices. Under 532 nm laser illumination, this photodetector exhibits high responsivity (528.1 A/W) and fast photoresponse (rise time ∼3.0 μs/decay time ∼31.3 μs). Furthermore, we demonstrated single-pixel image sensing capabilities of the device at room temperature across various modulation frequencies. Importantly, imaging at a frequency as high as 15 000 Hz was attained, indicating its great potential for next-generation, high-performance single-pixel image sensing applications.

Spin–orbit optical broadband achromatic spatial differentiation imaging

Spatial optical analog differentiation allows ultrahigh-speed and low-power-consumption of image processing, as well as label-free imaging of transparent biological objects. Optical analog differentiation with broadband and incoherent sources is appealing for its multi-channels and multi-task information processing, as well as the high-quality differentiation imaging. Currently, broadband and incoherent optical differentiation is still challenging. Here, a compact and broadband achromatic optical spatial differentiator is demonstrated based on the intrinsic spin–orbit coupling in a natural thin crystal. By inserting a uniaxial crystal just before the camera of a conventional microscope, the spin to orbit conversion will embed an optical vortex to the image field and make a second-order topological spatial differentiation to the field, thus an isotropic differential image will be captured by the camera. The wavelength-independent property of the intrinsic spin–orbit coupling effect allows us to achieve broadband analog computing and achromatic spatial differentiation imaging. With this differentiation imaging method, both amplitude and pure phase objects are detected with high contrast. Transparent living cells and biological tissues are imaged with their edge contours and intracellular details protruded in the edge detection mode and edge enhancement mode, respectively. These findings pave the way for optical analog computing with broadband incoherent light sources and concurrently drive the advancement of high-performance and cost-effective phase contrast imaging.

Miniaturized confocal Raman and Laser-induced breakdown spectroscopy imaging system based on micro-electro-mechanical mirror

Detection of the elemental and molecular structural distribution with high resolution and miniaturization of unknown minerals is a main bottleneck in deep space exploration and geology analysis. The aim is to enhance the accuracy of the chemical analysis of micro-samples by combining the distribution information from Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS). The existing Raman-LIBS imaging methods are difficult to balance the imaging performance and system volume. There is an urgent need to develop a Raman-LIBS imaging method with miniaturization, and high imaging performance. A miniaturized Raman-LIBS imaging instrument based on the micro-electro-mechanical (MEMS) mirror has been developed to overcome these challenges. The instrument utilizes dual 2D MEMS mirror scanning technology to shorten the optical length of the system and improve the detection efficiency of hybrid spectral signals. The optical probe measures 94 mm × 66 mm, and has an axial focusing ability of approximately 40 nm, with a lateral resolution of approximately 700 nm for Raman maps and 9.5 μm for LIBS maps. As a proof experiment, 3D high-resolution Raman-LIBS hybrid spectral distribution maps of meteorite Tisserlitine 001 were obtained. The attainment of high imaging performance and miniaturization in hybrid spectral imaging is crucial for on-site chemical analysis. The proposed instrument enables in-situ spectrum and multispectral imaging with miniaturization, high spatial resolution, and high stability. The instrument is a powerful tool for composition and structural information characterization in the fields of space exploration and geological exploration.

Multi-band microbolometer in CMOS technology

Multi-spectral imaging enhances the information diversity of the object with complex, expensive, and low integrated components. Here, we demonstrated an antenna-coupled microbolometric detector in complementary metal-oxide-semiconductor (CMOS) technology, utilizing SiO2 absorption and L-shaped fractal antenna to achieve multi-band detection from infrared (IR) to terahertz (THz). Experimental results demonstrate that the detector can achieve high sensitivity detection in both THz and IR bands, with the maximum detectivity of 5 (108 cm·Hz1/2/W @305 GHz and 7 (108 cm·Hz1/2/W @8.55 µm, respectively. The presented multi-spectral detector is easily implementable in integrated circuit process, conducive to high-density, low-cost, and high-performance array imaging.

Application of Ultra-High-Field Magnetic Resonance Imaging to the Central Nervous System

The development of high-performance magnetic resonance imaging (MRI) scanners is ongoing. The strength of the magnetic field is the most important factor in the use of this technology. Ultra-high magnetic fields provide many benefits, including high spatial and temporal resolution. In this chapter, we describe the characteristics and images obtained using ultra-high-field MRI.

High-Spike Barrier Photodiodes Based on 2D Te/WS2 Heterostructures.

Two-dimensional (2D) van der Waals (vdWs) heterojunctions have been actively investigated in low-power-consumption and fast-response photodiodes owing to their atomically smooth interfaces and ultrafast interfacial charge transfer. However, achieving ultralow dark current and ultrafast photoresponse in the reported photovoltaic devices remains a challenge as the large built-in electric field in a heterojunction can not only speed up photocarrier transport but also increase the minority-carrier dark current. Here, we propose a high-spike barrier photodiode that can achieve both an ultralow dark current and an ultrafast response. The device is fabricated by the Te/WS2 heterojunction, while the band alignment can transition from type-II to type-I with a high electron barrier and a large hole built-in electronic field. The high electron barrier can greatly reduce the drift current of minority carriers and the generation current of the thermal carriers, while the large built-in electronic field can still speed up the photocarrier transport. The designed Te/WS2 vdWs photodiode yields an ultralow dark current of 8 × 10-14 A and an ultrafast photoresponse of 10/13 μs. Furthermore, a high-performance visible-light imager with a pixel resolution of 100 × 40 is demonstrated using the Te/WS2 vdWs photodiode. This work provides a comprehensive understanding of designing 2D-material-based photovoltaics with excellent overall performance.

Balancing High-performance and Lightweight: HL-UNet for 3D Cardiac Medical Image Segmentation

Cardiac magnetic resonance imaging is a crucial tool for analyzing, diagnosing, and formulating treatment plans for cardiovascular diseases. Currently, there is very little research focused on balancing cardiac segmentation performance with lightweight methods. Despite the existence of numerous efficient image segmentation algorithms, they primarily rely on complex and computationally intensive network models, making it challenging to implement them on resource-constrained medical devices. Furthermore, simplified models designed to meet the requirements of device lightweighting may have limitations in comprehending and utilizing both global and local information for cardiac segmentation. Therefore, we propose a novel 3D high-performance lightweight medical image segmentation network, HL-UNet, for application in cardiac image segmentation. Specifically, in HL-UNet, we propose a novel residual-enhanced Adaptive attention (REAA) module that combines residual-enhanced connectivity with an adaptive attention mechanism to efficiently capture key features of input images and optimize their representation capabilities, and integrates the Visual Mamba (VSS) module to enhance the performance of HL-UNet. Compared with large-scale models such as TransUNet, HL-UNet increased the Dice of the right ventricular cavity (RV), left ventricular myocardia (MYO) and left ventricular cavity (LV), the key indicators of cardiac image segmentation, by 1.61%, 5.03% and 0.19%, respectively. At the same time, the Params and FLOPs of the model decreased by 41.3M and 31.05G, respectively. Compared to lightweight models such as the MISSFormer, the HL-UNet improves the Dice of RV, MYO, and LV by 4.11%, 3.82%, and 4.33%, respectively, when the number of parameters and computational complexity are close to or even lower.

Achromatic and Coma-Corrected Hybrid Meta-Optics for High-Performance Thermal Imaging.

Long-wave infrared (LWIR) imaging, or thermal imaging, is widely applied in night vision and security monitoring. However, the widespread use of LWIR imagers is impeded by their bulky size, considerable weight, and high cost. While flat meta-optics present a potential solution to these limitations, existing pure LWIR meta-optics face constraints such as severe chromatic or coma aberrations. Here, we introduce an approach utilizing large-scale hybrid meta-optics to address these challenges and demonstrate the achromatic, coma-corrected, and polarization-insensitive thermal imaging. The hybrid metalens doublet is composed of a metasurface corrector and a refractive lens, featuring a full field-of-view angle surpassing 20° within the 8-12 μm wavelength range. Employing this hybrid metalens doublet, we showcase high-performance thermal imaging capabilities both indoors and outdoors, effectively capturing ambient thermal radiation. The proposed hybrid metalens doublet holds considerable promise for advancing miniaturized, lightweight, and cost-effective LWIR optical imaging systems.

Image reconstruction for electrostatic tomography with deep convolutional neural network

Electrostatic tomography (EST) has the characteristics of being radiation-free and high real-time imaging performance. However, due to its passive measurement method, EST only provides limited input data equal to the number of electrode plates, which results in more serious ill-posed inverse problem. As a result, the imaging accuracy of traditional algorithms is low. To address this problem, an improved deep learning model is proposed for image reconstruction of EST, which is based on a convolutional neural network (CNN). The proposed network is built upon the LeNet-5 deep network model, which incorporates two convolution layers to extract data features and two maximum pooling layers to perform dimension reduction. Furthermore, the LeakyReLU activation function is employed to solve the gradient vanishing problem and accelerate the training process by introducing the non-zero gradients. By constructing an EST model, 8 representative distributions were simulated and 15,930 samples were generated. After 250 iterations, more accurate reconstructed images were generated. To verify the noise immunity of the network model, Gaussian white noises of 20 dB, 30 dB, and 50 dB were added to the test set, and the proposed model could still accurately reconstruct the positions and shapes of the samples. The network is further compared with the traditional algorithms, which reconstructs better results. In addition, the reconstruction results by the proposed model are still relatively accurate for several simulated random samples of different number, shapes and positions. Finally, a 16-electrode sensor array experimental system is designed. The experimental results show that the improved CNN algorithm has a better imaging effect than the traditional algorithms and the CNN algorithm, which is consistent with the simulation results, proving that the model has good generalization ability.

Defect Mitigation in Lead-Free Cs3Bi2I9 Single Crystals for High Performance X-Ray Detection and Imaging

Defect Mitigation in Lead-Free Cs₃Bi₂I₉ Single Crystals for High Performance X-Ray Detection and Imaging

High-Resolution X-ray Image from Copper-Based Perovskite Hybrid Polymer.

Cs3Cu2I5 nanocrystals (NCs) are considered to be promising materials due to their high photoluminescence efficiency, lack of lead toxicity, and X-ray responsiveness. However, during the crystallization process, NCs are prone to agglomeration and exhibit uneven size distribution, resulting in several light scattering that severely affect their imaging resolution. Herein, we successfully developed a high-resolution scintillator film by growing copper-based perovskite NCs within a hybrid polymer matrix. By leveraging the ingenious integration of polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA), the size and distribution uniformity of Cs3Cu2I5 NCs can be effectively controlled. Consequently, a high spatial resolution of 14.3 lp mm-1 and a low detection limit of 105 nGy s-1 are achieved, and the scintillator film has excellent flexibility and stability. These results highlight the promising application of Cs3Cu2I5 scintillator films in low-cost, flexible, and high-performance medical imaging.