Flexible Image Research Articles

A Hollow-Core Fiber Based Stand-Alone Multimodal (2-Photon, 3-Photon, SHG, THG) Nonlinear Flexible Imaging Endoscope System

A Hollow-Core Fiber Based Stand-Alone Multimodal (2-Photon, 3-Photon, SHG, THG) Nonlinear Flexible Imaging Endoscope System

Flexible Natural Language-Based Image Data Downlink Prioritization for Nanosatellites

Nanosatellites increasingly produce more data than can be downlinked within a reasonable time due to their limited bandwidth and power. Therefore, an on-board system is required to prioritize scientifically significant data for downlinking, as described by scientists. This paper determines whether natural language processing can be used to prioritize remote sensing images on CubeSats with more flexibility compared to existing methods. Two approaches implementing the same conceptual prioritization pipeline are compared. The first uses YOLOv8 and Llama2 to extract image features and compare them with text descriptions via cosine similarity. The second approach employs CLIP, fine-tuned on remote sensing data, to achieve the same. Both approaches are evaluated on real nanosatellite hardware, the VERTECS Camera Control Board. The CLIP approach, particularly the ResNet50-based model, shows the best performance in prioritizing and sequencing remote sensing images. This paper demonstrates that on-orbit prioritization using natural language descriptions is viable and allows for more flexibility than existing methods.

Enhancing low-energy X-ray excited afterglow in lanthanide-doped fluoride core@shell nanoparticles for autofluorescence-free imaging

Lanthanide-doped fluoride nanoparticles (NPs) exhibit tunable X-ray excited afterglow (XEA), holding great promise for autofluorescence-free flexible X-ray imaging. However, materials with low atomic numbers, while sensitive to low-energy X-ray photons, suffer from weak X-ray absorption coefficients. This poses a significant challenge in achieving high-performance XEA with minimized radiation risk. In this study, we enhance the low-energy XEA of lanthanide activators by engineering the interfacial defect formation energy (Ef) in CaF2-based heterogeneous core/shell nanoarchitectures. Mechanistic investigations demonstrate that a large lattice misfit between the core and shell reduces the interfacial defect Ef, facilitating the formation of Frenkel defects and significantly increasing XEA intensity after low-energy X-ray irradiation. Specifically, the heterogeneous CaF2:Tb@CaLuF5 core/shell NPs, with a misfit of 3.382 %, exhibit approximately ∼ 8.9 times higher XEA intensity compared to the CaF2:Tb@CaF2 homogeneous core/shell NPs at 10 kV. Furthermore, integrating the CaF2:Tb@CaLuF5 NPs into a flexible scintillation screen enables XEA-based delayed imaging with high spatial resolution, up to approximately 14.2 lp mm−1, and an autofluorescence-free background. These findings advance the development of superior low-energy XEA materials and pave the way for autofluorescence-free three-dimensional X-ray imaging.

Flexible X-ray Imaging and Stable Information Storage of SrF2:Eu Based on Radio-Photoluminescence.

X-ray imaging has garnered widespread interest in biomedical diagnosis and nondestructive detection. The exploration of radio-photoluminescence has hastened the advancement of X-ray information storage. However, significant challenges persist in achieving the prolonged imaging of curved objects without attenuation. Here, europium-doped strontium fluoride (SrF2:Eu) is meticulously created to exhibit a linear response to an extensive range of X-ray doses (maximum dose > 5000 Gy), showcasing excellent X-ray information reading/erasing reusability properties (10 cycles). This is accompanied by a red-to-blue emission transition under UV excitation, sustaining for 150 days without attenuation. To elucidate the phenomena of irradiated photoluminescent discoloration and the reversible X-ray storage of SrF2:Eu, we propose an electron-vacancy trap (valence conversion) mechanism, information stably retained by the SrF2:Eu-based device under ambient conditions due to high energy barriers. The time-lapse readout capability is further demonstrated for three-dimensional imaging of curved objects (10 lp mm-1) based on SrF2:Eu embedded within a polydimethylsiloxane (SrF2:Eu@PDMS). The SrF2:Eu demonstrates time-lapse imaging, reversible radio-photoluminescence, and recoverable X-ray storage, offering a promising avenue for optical information encryption and anticounterfeiting applications.

Single activator doped fluoride nanoparticles for X-ray excited high-resolution and delayed flexible nonplanar imaging

Lanthanide doped fluoride nanoparticles (NPs) exhibit adjustable X-ray excited optical/persistent luminescence (XEOL/XEPL) and possessing extensive potential in XEPL-based delay imaging. However, the high-resolution and delayed XEPL-based delay imaging always requires strict introduction of sensitized or heterovalent ions and the construction of complex structures for excellent XEPL performance of lanthanide-doped fluoride NPs, which is attributed to a lack of effective and convenient strategies. Here we show that the intense XEPL strength was obtained by single Tb3+ activated ion doping and simple CsY2F7@NaYF4 core/shell structure for X-ray excited high-resolution and delayed flexible nonplanar imaging. The strict introduction and control of sensitized or heterovalent ions, and the construction of intricate multilayer nanostructure are avoided. In addition, we enable the NPs to achieve high and long-term XEPL performance by simply thermal processing strategy. We successfully mixed minimized amount of the NPs into flexible film to create a scintillation screen which consequently exhibit high surface smoothness, environmental stability, and transparency. Our results demonstrate high resolution delayed imaging of the NPs integrated flexible film for the interior of nonplanar objects. The spatial resolution of 14.3 lp mm−1 is substantially higher than the typical spatial resolutions required for medical CT scans (2 lp mm−1) and X-ray imaging (3.5 lp mm−1). These findings will promote the development of advanced delayed X-ray nonplanar imaging applications.

Flexible Soft X-Ray Image Sensors based on Metal Halide Perovskites With High Quantum Efficiency.

Soft X-ray imaging is a powerful tool to explore the structure of cells, probe material with nanometer resolution, and investigate the energetic phenomena in the universe. Conventional soft X-ray image sensors are by and large Si-based charge coupled devices that suffer from low frame rates, complex fabrication processes, mechanical inflexibility, and required cooling below -60°C. Here, a soft X-ray photodiode is reported based on low-cost metal halide perovskite with comparable performance to commercial Si-based device. Nanothrough network electrodeminimized the optical loss due to the shadowing of insensitive layers, while a multidimensional perovskite heterojunctionis generated to reduce the photo-generated carrier loss. This strategy promoted a record quantum efficiency of 8×103% without cooling, several orders of magnitude greater than the previously achieved. Flexible and curved soft X-ray imaging arrays are fabricated based on this high-performance device structure, demonstrating stable soft X-ray response and sharp imaging capabilities. This work highlights the low-cost and efficient perovskite photodiode as a strong candidate for the next-generation soft X-ray image sensors.

Optical design of a 5× zoom afocal telescope with deformable mirrors

All-reflective zoom afocal telescopes can be integrated with existing imaging systems as foreoptics, enabling flexible imaging with adjustable resolution. This paper proposes an approach to designing a 5× zoom afocal telescope using deformable mirrors. Based on matrix optics, the first-order parameters for a coaxial reflective 5× zoom afocal telescope with a fixed primary mirror and three deformable mirrors are determined. To prevent obscuration, the mirrors are tilted at their vertices, which introduces asymmetric aberrations. To correct these aberrations, XY polynomial surfaces are employed on the primary mirror and an additional flat fold mirror. The final design and image simulations indicate that the system achieves good image quality across all zoom positions, enabling 5× zoom imaging with a maximum root mean square wavefront error of less than 0.125λ (λ = 632.8 nm), thereby validating the efficacy of the proposed design methodology.

Oriented Alignment of CsPbBr3 Single-Crystal Arrays for Flexible X-ray Imaging.

The utilization of perovskite materials in flexible optoelectronics is experiencing distinct diversification including X-ray detection applications. Here, we report the oriented alignment of cesium lead bromide (CsPbBr3) single-crystal arrays on flexible polydimethylsiloxane (PDMS) substrates. By precisely confining the crystallization process within spatially delimited precursor droplets, we achieve a well-oriented crystal alignment through the spontaneous rotation of the CsPbBr3 microcuboids. This approach allows for precise control over the microcuboid morphologies by varying the growth temperature. We design flexible X-ray detector arrays by seamlessly integrating CsPbBr3 microcuboids with electrode arrays. The flexible X-ray detector can output a high sensitivity of 1.97 × 105 μC·Gyair-1·cm-2 and a low detection limit of 89 nGyair·s-1 after the surface passivation process. The excellent mechanical properties, outstanding X-ray detection capabilities, and high pixel uniformity are also demonstrated in conformal X-ray imaging of curved surfaces.

Advancements and Challenges of Vacuum‐Processed Organic Photodiodes: A Comprehensive Review

Organic photodiodes (OPDs) have made remarkable strides and now poised to surpass traditional silicon photodiodes (PDs) in various aspects including linear dynamic range (LDR), detectivity, wavelength selectivity, and versatility.[1] Tunable mechanical and optoelectronic properties of organic semiconductors, coupled with lower process costs, have propelled OPDs into the spotlight across fields such as wearable light fidelity systems, flexible image sensors, and biomedical imaging.[2–5] While most advanced organic imaging systems to date rely on polymer‐based solution processes, challenges such as the use of toxic organic solvents and reproducibility issues hinder their commercialization.[6,7] Vacuum‐processed OPDs offer a promising alternative, boasting eco‐friendliness and compatibility with large‐scale fabrication facilities.[8,9] In this review, recent advancements and challenges in vacuum‐processed OPDs, an area that has received less attention compared to solution‐processed counterparts, are explored. Herein, four primary pathways for development of vacuum‐processed OPDs are outlined: 1) ultraviolet‐selective OPDs, 2) visible‐light‐selective OPDs, 3) near‐infrared or short‐wave‐infrared‐sensitive OPDs, and 4) addressing challenges such as higher noise currents compared to inorganic PDs. In this review, it is aimed to furnish readers with a comprehensive understanding of vacuum‐processed OPDs, spanning from materials design to device engineering.

Time resolved x-ray diffraction using the flexible imaging diffraction diagnostic for laser experiments (FIDDLE) at the National Ignition Facility (NIF): Preliminary assessment of diffraction precision.

The Flexible Imaging Diffraction Diagnostic for Laser Experiments (FIDDLE) is a new diagnostic at the National Ignition Facility (NIF) designed to observe in situ solid-solid phase changes at high pressures using time resolved x-ray diffraction. FIDDLE currently incorporates five Icarus ultrafast x-ray imager sensors that take 2ns snapshots and can be tuned to collect X-rays for tens of ns. The platform utilizes the laser power at NIF for both the laser drive and the generation of 10keV X-rays for ∼10ns using a Ge backlighter foil. We aim to use FIDDLE to observe diffraction at different times during compression to probe the kinetics of phase changes. Pb undergoes two solid-solid phase transitions during ramp compression: from face centered cubic (FCC) to hexagonal close packed (HCP) and HCP to body centered cubic (BCC). Results will be reported on some of the first shots using the FIDDLE diagnostic at NIF on ramp compressed Pb to a peak pressure of ∼110GPa and a single undriven CeO2 calibration shot. A discussion of the uncertainties in the observed diffraction is included.

Developing time-resolved x-ray diffraction diagnostics at the National Ignition Facility (invited).

As part of a program to measure phase transition timescales in materials under dynamic compression, we have designed new x-ray imaging diagnostics to record multiple x-ray diffraction measurements during a single laser-driven experiment. Our design places several ns-gated hybrid CMOS (hCMOS) sensors within a few cm of a laser-driven target. The sensors must be protected from an extremely harsh environment, including debris, electromagnetic pulses, and unconverted laser light. Another key challenge is reducing the x-ray background relative to the faint diffraction signal. Building on the success of our predecessor (Target Diffraction In Situ), we implemented a staged approach to platform development. First, we built a demonstration diagnostic (Gated Diffraction Development Diagnostic) with two hCMOS sensors to confirm we could adequately protect them from the harsh environment and also acquire acceptable diffraction data. This allowed the team to quickly assess the risks and address the most significant challenges. We also collected scientifically useful data during development. Leveraging what we learned, we recently developed a much more ambitious instrument (Flexible Imaging Diffraction Diagnostic for Laser Experiments) that can field up to eight hCMOS sensors in a flexible geometry and participate in back-to-back shots at the National Ignition Facility (NIF). The design also allows for future iterations, such as faster hCMOS sensors and an embedded x-ray streak camera. The enhanced capabilities of the new instrument required a much more complex design, and the unexpected issues encountered on the first few shots at NIF remind us that complexity has consequences. Our progress in addressing these challenges is described herein, as is our current focus on improving data quality by reducing x-ray background and quantifying the uncertainties of our diffraction measurements.

Retina-Inspired Large-Area Solution-Processed flexible Multi-Band organic neuromorphic synaptic transistor arrays

The proliferation of high-efficacy, pliable organic neuromorphic synaptic transistors is quintessential for the integration into wearable artificial intelligence ecosystems. Nevertheless, their development is hindered by substantial energy demands and suboptimal charge carrier mobility. To surmount these obstacles, we exploit solution-processed poly(amic acid) (PAA) dielectrics and organic semiconductors to engineer pliable arrays of organic neuromorphic synaptic transistors atop a polyethylene terephthalate (PET) matrix. The polar group and nanogroove structure of PAA obtain excellent semiconductor crystal structure, and the excellent dielectric properties enable these engineered arrays to show a charge carrier mobility peak of 29.83 cm2 V−1 s−1 an aggregate mean mobility of 15.87 cm2 V−1 s−1 (standard deviation is 6.71) at a voltage of −3 V and the energy expenditure per synaptic transaction was only 0.26 fJ. Additionally, the transistors possess the aptitude for photodetection across ultraviolet–visible to near-infrared spectral bands. The successful execution of flexible imaging, Pavlovian classical conditioning reflex associative learning, coupled with a 93.9 % accuracy in handwritten numeral recognition, corroborates the viability of these high-mobility, low-power organic neuromorphic synaptic transistor arrays.

Image interpretation scaffolds support adolescents’ historical reasoning

BackgroundImage interpretation scaffolds and mind mapping may support students’ historical reasoning. Benefits of such approaches are, until present, not empirically tested. AimsThis quasi-experimental study compared effects of three conditions: a sequenced image interpretation scaffold, a flexible image interpretation scaffold, and mind mapping on students’ historical reasoning about and with images. SampleParticipants were adolescents (secondary school students, N = 145, M age 13.9 years). MethodsHistorical reasoning was assessed with a writing task. Participants interpreted three photographs over three time points. At T1, students had no support. At T2 and T3, students interpreted an image with the randomly assigned condition. Students’ interpretative essays were rated to assess historical reasoning. ResultsImage interpretation scaffolds better supported historical reasoning than mind mapping. Both interpretation scaffolds enhanced historical reasoning. Particularly the flexible image interpretation scaffold appeared to benefit contextualization and the description of the relevance of the image message for the present. However, effects of the flexible scaffold were not stable over time. ConclusionsImage interpretation scaffolds seem beneficial to support students’ interpretation of historical images. Further research needs to investigate how image interpretation scaffolds support historical reasoning for different types of images.

Heating revival of Cs3MnBr5 for anti-counterfeiting and large-area flexible X-ray imaging

Cesium manganese bromide metal halide has great potential in the field of X-ray imaging and anti-counterfeiting due to its excellent optoelectronic properties. Here, Cs3MnBr5 was successfully prepared by a simple method. Uniquely a novel phenomenon based on H2O induced color change was discovered, Cs3MnBr5 can recover from aqueous solution more than 10 times under heating, which can be used in fluorescent anti-counterfeiting applications. Furthermore, Cs3MnBr5@PDMS, prepared by the PDMS composite strategy, has been demonstrated to exhibit a stability that is 20 times greater than that of Cs3MnBr5. Simultaneously, the light yield of Cs3MnBr5 is evaluated to be 21688 photons/MeV. Furthermore, it has been successfully applied in non-destructive detection and biological imaging and the spatial resolution can be restored to 10 lp mm−1.

Visible–infrared person re-identification via patch-mixed cross-modality learning

Visible–infrared person re-identification (VI-ReID) aims to retrieve images of the same pedestrian from different modalities, where the challenges lie in the significant modality discrepancy. To alleviate the modality gap, recent methods generate intermediate images by GANs, grayscaling, or mixup strategies. However, these methods could introduce extra data distribution, and the semantic correspondence between the two modalities is not well learned. In this paper, we propose a Patch-Mixed Cross-Modality framework (PMCM), where two images of the same person from two modalities are split into patches and stitched into a new one for model learning. A part-alignment loss is introduced to regularize representation learning, and a patch-mixed modality learning loss is proposed to align between the modalities. In this way, the model learns to recognize a person through patches of different styles, thereby the modality semantic correspondence can be inferred. In addition, with the flexible image generation strategy, the patch-mixed images freely adjust the ratio of different modality patches, which could further alleviate the modality imbalance problem. On two VI-ReID datasets, we report new state-of-the-art performance with the proposed method.

OOPS: Object-Oriented Polarization Software for analysis of fluorescence polarization microscopy images.

Most essential cellular functions are performed by proteins assembled into larger complexes. Fluorescence Polarization Microscopy (FPM) is a powerful technique that goes beyond traditional imaging methods by allowing researchers to measure not only the localization of proteins within cells, but also their orientation or alignment within complexes or cellular structures. FPM can be easily integrated into standard widefield microscopes with the addition of a polarization modulator. However, the extensive image processing and analysis required to interpret the data have limited its widespread adoption. To overcome these challenges and enhance accessibility, we introduce OOPS (Object-Oriented Polarization Software), a MATLAB package for object-based analysis of FPM data. By combining flexible image segmentation and novel object-based analyses with a high-throughput FPM processing pipeline, OOPS empowers researchers to simultaneously study molecular order and orientation in individual biological structures; conduct population assessments based on morphological features, intensity statistics, and FPM measurements; and create publication-quality visualizations, all within a user-friendly graphical interface. Here, we demonstrate the power and versatility of our approach by applying OOPS to punctate and filamentous structures.

Facile SILAR deposited SnS/NiS vertical heterojunction for high performance flexible broadband photodetector

Low-cost, flexible broadband photodetectors fabricated from two-dimensional transition metal chalcogenides have garnered attention because of their excellent absorption coefficient and photoconductivity. Likewise, vertical heterojunctions fabricated from two two-dimensional (2D) transition metal chalcogenides (TMCs) also have drawn major curiosity lately owing to their superior optical performance. This work reports a p-p type II vertical Van der Waal's heterojunction structure by depositing thin film of NiS over SnS on a flexible paper substrate. Morphological and structural characterization confirms presence of a rhombohedral β-NiS crystal structure along with traces of Ni(OH)2 on orthorhombic SnS nanoparticles. The device fabrication method made use of the inexpensive, clean room free SILAR (Successive Ionic Layer Adsorption and Reaction) technique. A purposeful modification of narrow bandgap property of NiS is done by depositing it in an alkaline environment. The fabricated device records optical responsivity of 0.92 mA/W under UV illumination, 5.32 mA/W under Visible illumination, and 0.8 mA/W under NIR illumination. A maximum EQE of 1.3 % is observed along with superior response times of 0.114 s (UV),0.103 s (Visible) and 1.34 s (NIR). The acquired photo response is due to superior absorption property of NiS in UV region and SnS in the visible and NIR region. The difference in fermi level between two materials causes efficient separation of the charge carriers that results in junctional electric field upon light illumination. The device underwent flexibility testing and shown exceptional resistance to bending force making it suitable for numerous applications like wearable healthcare monitoring, security purposes and flexible image sensors.

Zero-Dimensional Copper(I) Halide Microcrystals as Highly Efficient Scintillators for Flexible X-ray Imaging.

Commercially available rare-earth-doped inorganic oxide materials have been widely applied as X-ray scintillators, but the fragile characteristics, high detection limit, and harsh preparation condition seriously restrict their wide applications. Furthermore, it remains a huge challenge to realize X-ray flexible imaging technology for real-time monitoring of the curving interface of complex devices. To address these issues, we herein report two isostructural cuprous halides of zero-dimensional (0D) [AEPipz]CuX3·X·H2O (AEPipz = N-aminoethylpiperazine, X = Br and I) with controllable size to nanosize crystal as highly efficient scintillators toward flexible X-ray imaging. These cuprous halides exhibit highly efficient cyan photoluminescence and radioluminescence emissions with the highest quantum yield of 92.1% and light yield of 62,400 photons MeV-1, respectively, surpassing most of the commercially available inorganic scintillators. Meanwhile, the ultralow detection limit of 95.7 nGyair s-1 was far below the X-ray dose required for diagnosis (5.5 μGyair s-1). More significantly, the flexible film is facilely assembled with excellent foldability and high crack resistance, which further acts as a scintillation screen achieving a high spatial resolution of 17.4 lp mm-1 in X-ray imaging, demonstrating the potential application in wearable radiation radiography. The combined advantages of high light yield, low detection limit, and excellent flexibility promote these 0D cuprous halides as the most promising X-ray scintillators.

Cascaded-prism multi-mode beam scanning method for three-dimensional imaging lidar

Light detection and ranging (lidar) has emerged as an indispensable approach to three-dimensional (3D) perception, which probably suffers from performance limitations with traditional beam steering devices. In this paper, we investigate a cascaded-prism beam scanning method to enhance the versatility of 3D imaging lidar systems. The cascaded-prism-based 3D lidar architecture is theoretically developed with an emphasis on a rigorous beam scan model. By exploiting the additional flexibility of cascaded prisms, the lidar can achieve beam scanning through prism rotation in either step-motion or constant-speed mode, which exhibits superior agility and adaptability in multi-mode pattern analysis. Moreover, the cascaded-prism beam scanning lidar is demonstrated with a 3D imaging performance evaluation in terms of field of view, angular resolution and sampling density. It proves that the cascaded-prism beam scanner can offer lidar systems with flexible and configurable 3D imaging capability while balancing between a wide field of view and high angular resolution.

Single-shot lensless masked imaging with enhanced self-calibrated phase retrieval.

Single-shot lensless imaging with a binary amplitude mask enables a low-cost and miniaturized configuration for wave field recovery. However, the mask only allows a part of the wave field to be captured, and thus the inverse decoding process becomes a highly ill-posed problem. Here we propose an enhanced self-calibrated phase retrieval (eSCPR) method to realize single-shot joint recovery of mask distribution and the sample's wavefront. In our method, a sparse regularized phase retrieval (SrPR) algorithm is designed to calibrate the mask distribution. Then, a denoising regularized phase retrieval (DrPR) algorithm is constructed to reconstruct the wavefront of the sample. Compared to conventional single-shot methods, our method shows robust and flexible image recovery. Experimental results of different samples are given to demonstrate the superiority of our method.