Miniature Imaging Research Articles

Fiber-integrated hybrid achromatic microlenses by combined femtosecond laser 3D printing

Compact achromats for visible wavelengths are crucial for miniaturized and lightweight full-color endoscopes. Emerging femtosecond laser 3D printing technology offers new possibilities for enhancing the optical performance of miniature imaging lenses on fibers. In this work, we combine refractive and diffractive elements with complementary dispersive properties to create thin, high-performance hybrid achromatic lenses within the visible spectrum, avoiding the use of different optical materials. Using a fiber-integrated hybrid achromatic lens array, clear images are captured across different wavelengths. The fabrication process is carried out using femtosecond laser direct writing (DLW) assisted by femtosecond projection lithography based on a digital micromirror device (DMD). Our work is expected to significantly contribute to the advancement of integrated and miniaturized biomedical imaging devices.

Technologies for depth scanning in miniature optical imaging systems [Invited

Biomedical optical imaging has found numerous clinical and research applications. For achieving 3D imaging, depth scanning presents the most significant challenge, particularly in miniature imaging devices. This paper reviews the state-of-art technologies for depth scanning in miniature optical imaging systems, which include two general approaches: 1) physically shifting part of or the entire imaging device to allow imaging at different depths and 2) optically changing the focus of the imaging optics. We mainly focus on the second group of methods, introducing a wide variety of tunable microlenses, covering the underlying physics, actuation mechanisms, and imaging performance. Representative applications in clinical and neuroscience research are briefly presented. Major challenges and future perspectives of depth/focus scanning technologies for biomedical optical imaging are also discussed.

A Multicircle Planar Electrical Impedance Tomography Sensor for 3-D Miniature Imaging

In this paper, a multi-circle planar electrical impedance tomography (EIT) sensor is proposed for three-dimensional (3D) miniature imaging. There are two problems in 3D miniature EIT imaging: 1) the spatial resolution is low due to the number of electrodes is limited; 2) contact impedance influences image reconstruction quality severely. The proposed EIT sensor made by a printed circuit board (PCB) adopts multi-circle structure and tackles the two problems. Driven electrodes are distributed on the outermost two circles, while measurement electrodes are distributed on the innermost circle. Contact impedance is reduced due to the area of driven electrodes could be larger than traditional ones by using the multi-circle structure, it’s also owning to gold is deposited on the surface of the electrodes. Moreover, a new driven-measurement pattern of the EIT sensor is proposed to improve the spatial resolution as well as image reconstruction quality. The proposed EIT sensor is verified by both simulation and experiment. Average Image correlation coefficient (ICC) is as high as 0.8475 in simulation. Compared with the 16-electrode EIT sensor, ICC is improved 39.16%. In experiment, average ICC of four standard objects is 0.8389. The proposed 3D EIT sensor is good at miniature imaging.

:Souvenirs and the Experience of Empire in Ancient Rome

:<i>Souvenirs and the Experience of Empire in Ancient Rome</i>

Design, fabrication, and preclinical testing of a miniaturized, multispectral, chip-on-tip, imaging probe for intraluminal fluorescence imaging of the gastrointestinal tract.

Gastrointestinal cancers continue to account for a disproportionately large percentage of annual cancer deaths in the US. Advancements in miniature imaging technology combined with a need for precise and thorough tumor detection in gastrointestinal cancer screenings fuel the demand for new, small-scale, and low-cost methods of localization and margin identification with improved accuracy. Here, we report the development of a miniaturized, chip-on-tip, multispectral, fluorescence imaging probe designed to port through a gastroscope working channel with the aim of detecting cancerous lesions in point-of-care endoscopy of the gastrointestinal lumen. Preclinical testing has confirmed fluorescence sensitivity and supports that this miniature probe can locate structures of interest via detection of fluorescence emission from exogenous contrast agents. This work demonstrates the design and preliminary performance evaluation of a miniaturized, single-use, chip-on-tip fluorescence imaging system, capable of detecting multiple fluorochromes, and devised for deployment via the accessory channel of a standard gastroscope.

Deep-learning-augmented computational miniature mesoscope.

Fluorescence microscopy is essential to study biological structures and dynamics. However, existing systems suffer from a trade-off between field of view (FOV), resolution, and system complexity, and thus cannot fulfill the emerging need for miniaturized platforms providing micron-scale resolution across centimeter-scale FOVs. To overcome this challenge, we developed a computational miniature mesoscope (CM2) that exploits a computational imaging strategy to enable single-shot, 3D high-resolution imaging across a wide FOV in a miniaturized platform. Here, we present CM2 V2, which significantly advances both the hardware and computation. We complement the 3 × 3 microlens array with a hybrid emission filter that improves the imaging contrast by 5×, and design a 3D-printed free-form collimator for the LED illuminator that improves the excitation efficiency by 3×. To enable high-resolution reconstruction across a large volume, we develop an accurate and efficient 3D linear shift-variant (LSV) model to characterize spatially varying aberrations. We then train a multimodule deep learning model called CM2Net, using only the 3D-LSV simulator. We quantify the detection performance and localization accuracy of CM2Net to reconstruct fluorescent emitters under different conditions in simulation. We then show that CM2Net generalizes well to experiments and achieves accurate 3D reconstruction across a ~7-mm FOV and 800-μm depth, and provides ~6-μm lateral and ~25-μm axial resolution. This provides an ~8× better axial resolution and ~1400× faster speed compared to the previous model-based algorithm. We anticipate this simple, low-cost computational miniature imaging system will be useful for many large-scale 3D fluorescence imaging applications.

A Cognitive Semantic Analysis of the Preposition at

The present work is a pre-step toward large scale research. It aims at achieving two objectives: First, developing a cognitive diagram that covers the semantic range of the preposition at; second, examining EFL learners' semantic range on the preposition at within three broad categories: sentences, expressions and phrasal verbs. Accordingly, the researchers designed a test that covers the overall usages of the preposition at. Such a test helps examining the different cognitive domains of at and analyzing qualitatively and quantitatively the subjects' answers. The model that is used in the analysis of the first objective is Domain Highlighting by William Croft (1993). The main conclusions arrived at are: First, the cognitive theories can be applied to many language-related studies. The model used for instance managed to provide a miniature image to the different usages of the preposition at. Second, the diagram provided cognitively might help EFL learners recall the various semantic domains of the preposition at. Third, the subjects have a high lack of knowledge regarding the semantics of the preposition at in sentences, expressions and phrasal verbs. Fourth, the subjects' wrong choice of prepositions might be attributed to the semantic overlapping between the correct and incorrect ones; lack of knowledge, or to the limited frequency of usage;

Миниатюрные изделия из глины именьковской культуры VI –VII вв. н.э.

The article deals with miniature clay products of the Imenkovo culture. They are often mentioned in publications of finds both from the Imenkovo hillforts and from the settlements. At the same time, they are not found in the Imenkovo burial grounds. The research was based on a representative collection of miniature items from the Tetyushy-II hillfort in the Tetyushy district of Tatarstan. In addition, published materials from excavations of other Imenkovo settlements both in the Republic of Tatarstan and in the neighboring regions — Ulyanovsk and Samara were used. The author studied 124 miniature objects. They were grouped into four divisions. The first one includes geometrical objects (balls, cones, etc.), accounting for 22.5% of all finds. The second includes jewelry (9.8%). The most numerous (42.7%) is the third section — household items. Most of them are miniature vessels. The last section includes miniature images of animals (25%). All products are made of pure clay. They are well burnt. Moreover, almost all of them are either broken or have the loss of individual parts. Since the crafts were very durable, it is obvious that they were smashed on purpose. By their functional purpose, they were: 1) cult objects related to production activities (miniature figurines of animals); 2) magic crafts; 3) elements of ritual procedures; 4) household items (for example, drinking bowls); 5) shells for weapons (sling). In the latter case, natural nodules were used for the same purpose. The origin of most of the miniature vessels is associated with the Volga region. In the decorations and a number of types of miniature vessels, the connection of these artifacts with the antiquities of the Dyakovo archaeological culture can be traced. There are analogies in the antiquities of the Kiev culture. Miniature vessels with a round bottom are associated with cultures of the 1st millennium AD in Southern Cis-Urals. Some of the items of this complex were formed under the influence of the Sarmatian culture. All considered items are dated to the 6th–7th centuries AD. Thus, for the first time, the systematization of miniature items of the Imenkovo culture, their attribution and dating has been carried out.

Metaform optics: Bridging nanophotonics and freeform optics.

The demand for high-resolution optical systems with a compact form factor, such as augmented reality displays, sensors, and mobile cameras, requires creating new optical component architectures. Advances in the design and fabrication of freeform optics and metasurfaces make them potential solutions to address the previous needs. Here, we introduce the concept of a metaform-an optical surface that integrates the combined benefits of a freeform optic and a metasurface into a single optical component. We experimentally realized a miniature imager using a metaform mirror. The mirror is fabricated via an enhanced electron beam lithography process on a freeform substrate. The design degrees of freedom enabled by a metaform will support a new generation of optical systems.

Single cell plasticity and population coding stability in auditory thalamus upon associative learning

Cortical and limbic brain areas are regarded as centres for learning. However, how thalamic sensory relays participate in plasticity upon associative learning, yet support stable long-term sensory coding remains unknown. Using a miniature microscope imaging approach, we monitor the activity of populations of auditory thalamus (medial geniculate body) neurons in freely moving mice upon fear conditioning. We find that single cells exhibit mixed selectivity and heterogeneous plasticity patterns to auditory and aversive stimuli upon learning, which is conserved in amygdala-projecting medial geniculate body neurons. Activity in auditory thalamus to amygdala-projecting neurons stabilizes single cell plasticity in the total medial geniculate body population and is necessary for fear memory consolidation. In contrast to individual cells, population level encoding of auditory stimuli remained stable across days. Our data identifies auditory thalamus as a site for complex neuronal plasticity in fear learning upstream of the amygdala that is in an ideal position to drive plasticity in cortical and limbic brain areas. These findings suggest that medial geniculate body’s role goes beyond a sole relay function by balancing experience-dependent, diverse single cell plasticity with consistent ensemble level representations of the sensory environment to support stable auditory perception with minimal affective bias.

A MINIATURE LASER SPECKLE CONTRAST IMAGER FOR MONITORING OF THE NEURO-MODULATORY EFFECT OF TRANSCRANIAL FOCUSED ULTRASOUND STIMULATION.

Transcranial focused ultrasound stimulation is a neuromodulation technique that is capable of exciting or suppressing the neural network. Such neuro-modulatory effects enable the treatment of brain diseases non-invasively, such as treating stroke. The neuro-modulatory effect on cerebral hemodynamics has been monitored using laser speckle contrast imaging in animal studies. However, the bulky size and stationary nature of the imaging system constrains the application of this imaging technique on research that requires the animal to have different body positions or to be awake. We present the design of a system that combines a miniature microscope for laser speckle contrast imaging and transcranial focused ultrasound stimulation, as well as, test its capability to monitor cerebral hemodynamics during stimulation and compare the result with a benchtop imaging system.

Miniature image converter streak cameras for measurement of temporal characteristics of optical pulses in nanoand picosecond ranges

Miniature image converter streak cameras for measurement of temporal characteristics of optical pulses in nanoand picosecond ranges

MEMS Ultrasound Transducers for Endoscopic Photoacoustic Imaging Applications.

Photoacoustic imaging (PAI) is drawing extensive attention and gaining rapid development as an emerging biomedical imaging technology because of its high spatial resolution, large imaging depth, and rich optical contrast. PAI has great potential applications in endoscopy, but the progress of endoscopic PAI was hindered by the challenges of manufacturing and assembling miniature imaging components. Over the last decade, microelectromechanical systems (MEMS) technology has greatly facilitated the development of photoacoustic endoscopes and extended the realm of applicability of the PAI. As the key component of photoacoustic endoscopes, micromachined ultrasound transducers (MUTs), including piezoelectric MUTs (pMUTs) and capacitive MUTs (cMUTs), have been developed and explored for endoscopic PAI applications. In this article, the recent progress of pMUTs (thickness extension mode and flexural vibration mode) and cMUTs are reviewed and discussed with their applications in endoscopic PAI. Current PAI endoscopes based on pMUTs and cMUTs are also introduced and compared. Finally, the remaining challenges and future directions of MEMS ultrasound transducers for endoscopic PAI applications are given.

A Customized Two Photon Fluorescence Imaging Probe Based on 2D scanning MEMS Mirror Including Electrothermal Two-Level-Ladder Dual S-Shaped Actuators.

We report the design and characterization of a two-photon fluorescence imaging miniature probe. This customized two-axis scanning probe is dedicated for intraoperative two-photon fluorescence imaging endomicroscopic use and is based on a micro-electro-mechanical system (MEMS) mirror with a high reflectivity plate and two-level-ladder double S-shaped electrothermal bimorph actuators. The fully assembled probe has a total outer diameter of 4 mm including all elements. With a two-lens configuration and a small aperture MEMS mirror, this probe can generate a large optical scan angle of 24° with 4 V drive voltage and can achieve a 450 µm FOV with a 2-fps frame rate. A uniform Pixel Dwell Time and a stable scanning speed along a raster pattern were demonstrated while a 57-fs pulse duration of the excitation beam was measured at the exit of the probe head. This miniature imaging probe will be coupled to a two-photon fluorescence endomicroscope oriented towards clinical use.

Optimizing Requirements for a Compact Spaceborne Adaptive Spectral Imaging System in Subpixel Target Detection Applications

We developed a process to provide design recommendations for compact spaceborne spectral imaging systems with adaptive band selection capabilities. Our focus application was subpixel target detection, and we analyzed a set of mission scenarios to find relationships in detection performance between selected parameters of interest. We used an analytic model to predict performance and generate trade curves, then simulated a scene to analyze potential operational effects on performance for the selected target and background combinations. Using these models, we predicted and assessed each scenario to provide recommendations for mission feasibility and system design. The parameters we selected for analysis were target fill fraction, noise, number of bands, and scene complexity to find critical points in the trade space and reach a set of recommendations. We examined the operational effects by simulating a realistic scenario and ensuring key real-world phenomena were captured within the spectral images. Our results produced recommendations for each mission and provided a proof of concept for a process to analyze designs of miniature spaceborne imaging systems.

A Silicon Photonics Computational Lensless Active-Flat-Optics Imaging System

The need for lightweight, miniature imaging systems is becoming increasingly prevalent in light of the development of wearable electronics, IoT devices, and drones. Computational imaging enables new types of imaging systems that replace standard optical components like lenses with cleverly designed computational processes. Traditionally, many of these types of systems use conventional complementary metal oxide semiconductor (CMOS) or charge coupled device (CCD) sensors for data collection. While this allows for rapid development of large-scale systems, the lack of system-sensor co-design limits the compactness and performance. Here we propose integrated photonics as a candidate platform for the implementation of such co-integrated systems. Using grating couplers and co-designed computational processing in lieu of a lens, we demonstrate the use of silicon photonics as a viable platform for computational imaging with a prototype lensless imaging device. The proof-of-concept device has 20 sensors and a 45-degree field of view, and its optics and sensors are contained within a 2,000 μm × 200 μm × 20 μm volume.

High performance metalenses: numerical aperture, aberrations, chromaticity, and trade-offs

Metalenses consist of nanostructures that locally control the optical phase. They offer many degrees of freedom for manipulating a wavefront, which gives a number of advantages over bulk lenses, such as the straightforward elimination of spherical aberrations and an ultrathin dimension. Here, we compare the phase profiles of metalenses made of different dielectric materials and note the advantage of high refractive index materials. Higher refractive index materials such as silicon afford more degrees of freedom in terms of design and fabrication and are the basis for high-performance metalenses, even in the visible. Nevertheless, the imaging performance of single-element metalenses is still limited by coma and chromatic aberrations. This limitation is exacerbated by high numerical apertures and large areas. We review the challenges and trade-offs between numerical aperture, field of view, coma, chromatic aberration, and size. We also evaluate different phase engineering approaches to address these problems. We believe this review will help guide future developments in high-performance metalenses toward wide-field and high-resolution imaging, enabling scientific high-end miniature imaging systems.

Rachmaninov. “Six choirs for children’s or women’s voices”: specific of interpretation of the genre

Rachmaninov. “Six choirs for children’s or women’s voices”: specific of interpretation of the genre

Optical design of high resolution concave superposition compound eye

A compound eye is a way to reach miniature imaging systems. This paper discusses design and image evaluation of novel high resolution concave superposition compound eyes with a planar or curved detector. In the superposition system, each channel images all of fields of view of the system. This designed system contains three curved micro lens arrays with aspheric surfaces for the concave superposition eye. We have simulated and optimized a high resolution system by using geometrical and diffraction-based methods.

Concept for an X-ray telescope system with an angular resolution booster

ABSTRACT We present a concept for an X-ray imaging system with a high angular resolution and moderate sensitivity. In this concept, a two-dimensional detector, i.e., an imager, is put at a slightly out-of-focus position of the focusing mirror, rather than just at the mirror focus, as in the standard optics, to capture miniature images of objects. In addition, a set of multi-grid masks (or a modulation collimator) is installed in front of the telescope. We find that the masks work as a coded aperture camera and that they boost the angular resolution of the focusing optics. The major advantage of this concept is that a much better angular resolution, having an order of 2–3 or more than in the conventional optics, is achievable, while a high throughput (large effective area) is maintained, which is crucial in photon-limited high-energy astronomy, because any type of mirrors, including lightweight reflective mirrors, can be employed in our concept. If the signal-to-noise ratio is sufficiently high, we estimate that angular resolutions at the diffraction limit of 4″ and 0.″4 at ∼7 keV can be achieved with a pair of masks at distances of 1 m and 100 m, respectively.