Large-field Imaging Research Articles

Misalignment estimation for active telescopes

The estimation of the misalignment of an active telescope, from aberrations measured in its focal plane, is a tomographic issue. MMSE-based estimation is successfully used in optical tomography issues, like multiconjugate adaptive optics, where the problem is linear, and the phase perturbation spectrum rapidly decreasing. The implementation of MMSE developed in the case of multiconjugate adaptive optics has been applied to the alignment of active telescopes, although the forward problem is not linear, and the aberration spectrum different. Its performance is characterized by numerical modeling in the case of a TMA type large-field imaging space telescope, and compared to the classical Least-Square approach. The MMSE estimation brings a significant gain in terms of robustness and accuracy.

Fast and sub-pixel precision target tracking algorithm for intelligent dual-resolution camera

The intelligent dual-resolution camera can provide large imaging field and high-resolution for the parts in which we are interested simultaneously. It has important applications in visual tracking. Though many trackers show great robustness on recent benchmarks, few of them make high precision and run in real-time, which is harmful to practical applications. In this paper, we propose a fast and sub-pixel precision tracker. It uses the time-shift property of Fourier transform to convert the displacement of target in space domain into the period of the response in Fourier domain. Then an improved Hough transform is introduced to measure this period, so that the displacement with sub-pixel precision can be calculated. Furthermore, a method obtaining benchmarks utilizing the intelligent dual-resolution camera is proposed to verify the high-precision of our tracker. Many experiments have been done to compare the proposed tracker with some state-of-the-art sub-pixel precision trackers, and the results have shown that the proposed tracker outperform the best tracker by 15.4% in average median distance precision, while feasible for real-time tracking with the speed faster than 80 fps. What’s more, the proposed tracker have been evaluated on the dual-resolution camera, the results show that it can make the observation of targets in the high-resolution image more complete.

High-Frame-Rate Contrast-Enhanced Echocardiography Using Diverging Waves: 2-D Motion Estimation and Compensation.

Combining diverging ultrasound waves and microbubbles could improve contrast-enhanced echocardiography (CEE), by providing enhanced temporal resolution for cardiac function assessment over a large imaging field of view. However, current image formation techniques using coherent summation of echoes from multiple steered diverging waves (DWs) are susceptible to tissue and microbubble motion artifacts, resulting in poor image quality. In this study, we used correlation-based 2-D motion estimation to perform motion compensation for CEE using DWs. The accuracy of this motion estimation method was evaluated with Field II simulations. The root-mean-square velocity errors were 5.9% ± 0.2% and 19.5% ± 0.4% in the axial and lateral directions, when normalized to the maximum value of 62.8 cm/s which is comparable to the highest speed of blood flow in the left ventricle (LV). The effects of this method on image contrast ratio (CR) and contrast-to-noise ratio (CNR) were tested in vitro using a tissue mimicking rotating disk with a diameter of 10 cm. Compared against the control without motion compensation, a mean increase of 12 dB in CR and 7 dB in CNR were demonstrated when using this motion compensation method. The motion correction algorithm was tested in vivo on a CEE data set acquired with the Ultrasound Array Research Platform II performing coherent DW imaging. Improvement of the B-mode and contrast-mode image quality with cardiac motion and blood flow-induced microbubble motion was achieved. The results of motion estimation were further processed to interpret blood flow in the LV. This allowed for a triplex cardiac imaging technique, consisting of B mode, contrast mode, and 2-D vector flow imaging with a high frame rate of 250 Hz.

Osteitis pubis or symphysitis pubis

Osteitis pubis is one of the most common causes of chronic groin pain in many professional athletes. Symphysitis pubis with instability of the joint due to softening of the joint capsule and muscular imbalance of the corresponding muscles increases the instability of the sympyseal region, thus, resulting in a vicious cycle. Magnetic resonance imaging (MRI). Optimized MRI sequence protocol with oblique (axial oblique) layers parallel to the linea arcuata of iliac bone together with large image field for depiction of the entire pelvis and high-resolution sequences focused on the symphysis pubis. Recently, the correlation between MRI signs of osteitis pubis and long-term clinical outcome in agroup of professional soccer players was examined. In particular, edema in the peri-osseous tissue and isolated muscle lesions around the symphysis at the onset of symptoms were associated with partial recovery of the athletes. Furthermore, asignificant association of increased normalized signal intensity in the pubic bone on STIR (short-tau inversion recovery) sequences (corresponding presence and signal intensity of bone marrow edema) and apoor complete clinical improvement was observed. An optimized MRI protocol allows the diagnosis of osteitis pubis and provides important prognostic information. In case of clinical suspicion on osteitis pubis, MR imaging with an optimized sequence protocol should be performed.

Field-emission scanning probe lithography tool for 150 mm wafer

The development of next nodes of nano-electronic devices requires mask-less techniques for fast prototyping and analysis of ultimately down-scaled devices or for fabrication of templates for nanoimprint based high-volume manufacturing. Moreover, the atomic force microscopy (AFM) of large surfaces with acceptable speed becomes an issue with the introduction of large-sized wafers. The authors have designed an AFM system which is capable of field-emission scanning probe lithography on 150 mm wafers providing superior stitching accuracy better than 3 nm. The system is also providing noncontact, high-resolution 3D imaging employing active probes (i.e., piezoresistive self-sensing and thermo-mechanically self-actuated probes) and capable to operate with an array of four cantilevers. A high-precision X-Y-θ stage with 10 nm positioning accuracy and with 360° rotation capability enables the highest placement precision and cost effective large scanning field imaging.

Context Semantics for Small Target Detection in Large-Field Images with Two Cascaded Faster R-CNNs

Computer vision and image processing techniques have been widely applied to power transmission line inspection. However, the successful detection of small targets in large scenes is still challenging due to their low resolution and poor feature representation. Existing methods, such as multi-scale image pyramid, multi-scale feature pyramid and multiple heterogeneous feature fusion, etc. can extract more representative features of small objects, but they usually require high computation cost. In this paper, we propose an effective two cascaded Faster R-CNN strategy, which is based on multi-scale features and semantic information between the objects and the background, to address the small target detection in large scenes. Specially, we detect large object candidate proposals that may contain small objects at first and then map them to the original images to detect the small-sized targets on the high resolution regions. Experiments show that our strategy could lead to higher (83.0%) accuracy of small target detection and recognition than the one-stage Faster R-CNN (78.3%) on the dataset of aerial images.

Multi-Cell Multi-Task Convolutional Neural Networks for Diabetic Retinopathy Grading.

Diabetic Retinopathy (DR) is a non-negligible eye disease among patients with Diabetes Mellitus, and automatic retinal image analysis algorithm for the DR screening is in high demand. Considering the resolution of retinal image is very high, where small pathological tissues can be detected only with large resolution image and large local receptive field are required to identify those late stage disease, but directly training a neural network with very deep architecture and high resolution image is both time computational expensive and difficult because of gradient vanishing/exploding problem, we propose a Multi-Cell architecture which gradually increases the depth of deep neural network and the resolution of input image, which both boosts the training time but also improves the classification accuracy. Further, considering the different stages of DR actually progress gradually, which means the labels of different stages are related. To considering the relationships of images with different stages, we propose a Multi-Task learning strategy which predicts the label with both classification and regression. Experimental results on the Kaggle dataset show that our method achieves a Kappa of 0.841 on test set which is the 4th rank of all state-of-the-arts methods. Further, our Multi-Cell Multi-Task Convolutional Neural Networks (M2CNN) solution is a general framework, which can be readily integrated with many other deep neural network architectures.

Large field of view imaging system for remote target capture and trajectory measurement based on cone rotation.

In the remote target trajectory measurement system, because of the size limitation of the image sensor, the angle of view of the current telephoto camera is very small, which cannot meet the requirements of target acquisition. After comparing the current large-field imaging methods, a scheme of a large field of view (FoV) and high frame rate scanning by controlling the camera to perform conical rotation is proposed, and a 3 × 3 external FoV stitching system that includes the scheme is designed. An experimental prototype was constructed to verify the system. In this paper, the mechanical structure of the prototype, the camera exposure control flow, and the image data processing flow are introduced, and the imaging motion feature of the prototype caused by the camera exposure during conical motion is analyzed. In the experiment, the prototype controlled the camera accurately exposed to the sub-fields. Using a camera with an angle of view of 0.78°, a large angle of view system of 2.23° was obtained by FoV stitching. The system we present is less difficult to implement and has obvious advantages in volume and weight compared to multi-camera arrays. It is suitable for engineering applications in remote target measurement system.

RESEARCH ON THE CONSTRUCTION OF REMOTE SENSING AUTOMATIC INTERPRETATION SYMBOL BIG DATA

Abstract. Remote sensing automatic interpretation symbol (RSAIS) is an inexpensive and fast method in providing precise in-situ information for image interpretation and accuracy. This study designed a scientific and precise RSAIS data characterization method, as well as a distributed and cloud architecture massive data storage method. Additionally, it introduced an offline and online data update mode and a dynamic data evaluation mechanism, with the aim to create an efficient approach for RSAIS big data construction. Finally, a national RSAIS database with more than 3 million samples covering 86 land types was constructed during 2013–2015 based on the National Geographic Conditions Monitoring Project of China and then annually updated since the 2016 period. The RSAIS big data has proven to be a good method for large scale image interpretation and field validation. It is also notable that it has the potential to solve image automatic interpretation with the assistance of deep learning technology in the remote sensing big data era.

Long-Term Tracking of Free-Swimming Paramecium caudatum in Viscous Media Using a Curved Sample Chamber.

It is technically difficult to acquire large-field images under the complexity and cost restrictions of a diagnostic and instant field research purpose. The goal of the introduced large-field imaging system is to achieve a tolerable resolution for detecting microscale particles or objects in the entire image field without the field-curvature effect, while maintaining a cost-effective procedure and simple design. To use a single commercial lens for imaging a large field, the design attempts to fabricate a curved microfluidic chamber. This imaging technique improves the field curvature and distortion at an acceptable level of particle detection. This study examines Paramecium caudatum microswimmers to track their motion dynamics in different viscous media with imaging techniques. In addition, the study found that the average speed for P. caudatum was 60 µm/s, with a standard deviation of ±12 µm/s from microscopic imaging of the original medium of the sample, which leads to a variation of 20% from the average measurement. In contrast, from large-field imaging, the average speeds of P. caudatum were 63 µm/s and 68 µm/s in the flat and curved chambers, respectively, with the same medium viscosity. Furthermore, the standard deviations that were observed were ±7 µm/s and ±4 µm/s and the variations from the average speed were calculated as 11% and 5.8% for the flat and curved chambers, respectively. The proposed methodology can be applied to measure the locomotion of the microswimmer at small scales with high precision.

Weak lensing and spectroscopic analysis of the nearby dissociative merging galaxy cluster Abell 3376

The galaxy cluster Abell~3376 is a nearby (z=0.046) dissociative merging cluster surrounded by two prominent radio relics and showing an X-ray comet-like morphology. The merger system is comprised of the subclusters A3376W & A3376E. Based on new deep multi-wavelength large-field images and published redshifts, we bring new insights about the history of this merger. Despite the difficulty of applying the weak lensing technique at such low redshift, we successfully recovered the mass distribution in the cluster field. Moreover, with the application of a two-body model, we have addressed the dynamics of these merging system. We have found the individual masses of M_{200}^{W}=3.0_{-1.7}^{+1.3}x10^{14} M_{\odot} and M_{200}^{E}=0.9_{-0.8}^{+0.5}x10^{14} M_{\odot}. The cometary shaped X-ray distribution shows only one peak spatially coincident with both Eastern BCG and the A3376E mass peak whereas the gas content of A3376W seems to be stripped out. Our data allowed us to confirm the existence of a third subcluster located at the North, 1147+-62 kpc apart from the neighbour subcluster A3376E and having a mass M_{200}^{N}=1.4_{-1.0}^{+0.7}x10^{14} M_{\odot}. From our dynamical analysis, we found the merging is taking place very close to the plane of the sky, with the merger axis just 10 deg +-11 deg from it. The application of a two-body analysis code showed that the merging cluster is seen 0.9_{-0.3}^{+0.2} Gyr after the pericentric passage and it is currently going to the point of maximum separation between the subclusters.

New tools for non-invasive exploration of collagen network in cartilaginous tissue-engineered substitute.

In tissue engineering approaches, the quality of substitutes is a key element to determine its ability to treat cartilage defects. However, in clinical practice, the evaluation of tissue-engineered cartilage substitute quality is not possible due to the invasiveness of the standard procedure, which is to date histology. The aim of this work was to validate a new innovative system performed from two-photon excitation laser adapted to an optical macroscope to evaluate at macroscopic scale the collagen network in cartilage tissue-engineered substitutes in confrontation with gold standard histologic techniques or immunohistochemistry to visualize type II collagen. This system permitted to differentiate the quality of collagen network between ITS and TGF-β1 treatments. Multiscale large field imaging combined to multimodality approaches (SHG-TCSPC) at macroscopical scale represent an innovative and non-invasive technique to monitor the quality of collagen network in cartilage tissue-engineered substitutes before in vivo implantation.

Method for improving line flux and redshift measurements with narrowband filters

High redshift star-forming galaxies are discovered routinely through a flux excess in narrowband filters (NB) caused by an emission line. In most cases, the width of such filters is broad compared to typical line widths, and the throughput of the filters varies substantially within the bandpass. This leads to substantial uncertainties in redshifts and fluxes that are derived from the observations with one specific NB. In this work we demonstrate that the uncertainty in measured line parameters can be sharply reduced by using repeated observations of the same target field with filters that have slightly different transmittance curves. Such data are routinely collected with some large field imaging cameras that use multiple detectors and a separate filter for each of the detectors. An example is the NB118 data from ESO's VISTA InfraRed CAMera (VIRCAM). We carefully developed and characterized this method to determine more accurate redshift and line flux estimates from the ratio of apparent fluxes measured from observations in different narrowband filters and several matching broadband filters. Then, we tested the obtainable quality of parameter estimation both on simulated and actual observations for the example of Ha in the VIRCAM NB118 filters combined with broadband data in Y, J, H. We find that by using this method, the errors in the measured lines fluxes can be reduced up to almost an order of magnitude and that an accuracy in wavelength of better than 1nm can be achieved with the ~13nm wide NB118 filters.

Quasi-plane shear wave propagation induced by acoustic radiation force with a focal line region: a simulation study

Shear wave propagation speed has been regarded as an attractive indicator for quantitatively measuring the intrinsic mechanical properties of soft tissues. While most existing techniques use acoustic radiation force (ARF) excitation with focal spot region based on linear array transducers, we try to employ a special ARF with a focal line region and apply it to viscoelastic materials to create shear waves. First, a two-dimensional capacitive micromachined ultrasonic transducer with 64 × 128 fully controllable elements is realised and simulated to generate this special ARF. Then three-dimensional finite element models are developed to simulate the resulting shear wave propagation through tissue phantom materials. Three different phantoms are explored in our simulation study using: (a) an isotropic viscoelastic medium, (b) within a cylindrical inclusion, and (c) a transverse isotropic viscoelastic medium. For each phantom, the ARF creates a quasi-plane shear wave which has a preferential propagation direction perpendicular to the focal line excitation. The propagation of the quasi-plane shear wave is investigated and then used to reconstruct shear moduli sequentially after the estimation of shear wave speed. In the phantom with a transverse isotropic viscoelastic medium, the anisotropy results in maximum speed parallel to the fiber direction and minimum speed perpendicular to the fiber direction. The simulation results show that the line excitation extends the displacement field to obtain a large imaging field in comparison with spot excitation, and demonstrate its potential usage in measuring the mechanical properties of anisotropic tissues.

Generation of large field SEM image by panorama composition technology for nano-order measurement

Semiconductor manufacturing has a pressing need for a method to accurately evaluate the global shape deformation of a photomask pattern. We thus propose a novel composition technique for a large field panorama image of scanning electron microscopy (SEM). The proposed method optimises the arrangement of segmented imaging regions (SIRs), which are components of a panorama image, on the basis of the design data of the photomask pattern layout. The quantity of the line pattern segment, which is a clue to the connection in an overlapping region between adjoining SIRs and the connectability of any two SIRs, is evaluated. As a result of the optimisation, it is guaranteed that all SIR images can be connected theoretically. For 30 evaluation points, the maximum connection error of the SIR images was 1.5 nm in a simulation using pseudo-SEM images. The maximum total measurement error, which includes the connection error and CD measurement error from the panorama image, is estimated at 2.5 nm. This error was equivalent to about 1.4% of the photomask line width (target: 3%). The experiments using real SEM images demonstrate the effectiveness of the proposed method. It was visually confirmed that a large field, high-resolution and seamless panorama image can be generated.

SPECTRAL FILTRATION OF IMAGES BY MEANS OF DISPERSIVE SYSTEMS

Instruments for spectral filtration of images are an important element of the systems used in remote sensing, medical diagnostics, in-process measurements. The aim of this study is analysis of the functional features and characteristics of the proposed two image monochromator versions which are based on dispersive spectral filtering. The first is based on the use of a dispersive monochromator, where collimating and camera lenses form a telescopic system, the dispersive element of which is within the intermediate image plane. The second version is based on an imaging double monochromator with dispersion subtraction by back propagation. For the telescopic system version, the spectral and spatial resolutions are estimated, the latter being limited by aberrations and diffraction from the entrance slit. The device has been numerically simulated and prototyped. It is shown that for the spectral bandwidth 10 nm (visible spectral range), the aberration-limited spot size is from 10–20 μm at the image center to about 30 μm at the image periphery for the image size 23–27 mm. The monochromator with dispersion subtraction enables one to vary the spectral resolution (up to 1 nm and higher) by changing the intermediate slit width. But the distinctive feature is a significant change in the selected central wavelength over the image field. The considered designs of dispersive image monochromators look very promising due to the particular advantages over the systems based on tunable filters as regards the spectral resolution, fast tuning, and the spectral contrast. The monochromator based on a telescopic system has a simple design and a rather large image field but it also has a limited light throughput due to small aperture size. The monochromator with dispersion subtraction has higher light throughput, can provide high spectral resolution when recording a full data cube in a series of measuring acts for different dispersive element positions.

Quantitative analysis of the field of view for X-ray differential phase contrast imaging

Grating-based X-ray differential phase contrast imaging provides excellent image contrast for low-Z objects that cannot be acquired by conventional X-ray imaging, which has great potential applications in the early diagnosis of cancer and non-destructive detections of low-Z materials and devices. Large field of view imaging is a crucial factor for this technology from the laboratory to practical application. For the objective need of large field of view, on the basis of the Fresnel diffraction theory and the structure characteristics of gratings, we establish a quantitative physical model to analyze the factors that affect the imaging field of view and give a feasible way for large imaging field of view. This work provides a theoretical basis for the large field of view grating-based X-ray differential phase contrast imaging in the future.

Shape from focus for large image fields.

Shape from focus is a method for the accurate measurement of the geometrical shape of objects. The measurement principle is the local focus search. The method is suitable only for objects with a texture (optically rough surface). The longitudinal coordinate of a surface point is determined from the maximum of the focus measure function. The focus measure function expresses the quality of focus in a small image area. The measurement is fast because the focus measure function shows no oscillations. Thus, a large sampling step can be used. We present experimental results that demonstrate the capability of the proposed method.

Large-field electron imaging and X-ray elemental mapping unveil the morphology, structure, and fractal features of a Cretaceous fossil at the centimeter scale.

We used here a scanning electron microscopy approach that detected backscattered electrons (BSEs) and X-rays (from ionization processes) along a large-field (LF) scan, applied on a Cretaceous fossil of a shrimp (area ∼280 mm(2)) from the Araripe Sedimentary Basin. High-definition LF images from BSEs and X-rays were essentially generated by assembling thousands of magnified images that covered the whole area of the fossil, thus unveiling morphological and compositional aspects at length scales from micrometers to centimeters. Morphological features of the shrimp such as pleopods, pereopods, and antennae located at near-surface layers (undetected by photography techniques) were unveiled in detail by LF BSE images and in calcium and phosphorus elemental maps (mineralized as hydroxyapatite). LF elemental maps for zinc and sulfur indicated a rare fossilization event observed for the first time in fossils from the Araripe Sedimentary Basin: the mineralization of zinc sulfide interfacing to hydroxyapatite in the fossil. Finally, a dimensional analysis of the phosphorus map led to an important finding: the existence of a fractal characteristic (D = 1.63) for the hydroxyapatite-matrix interface, a result of physical-geological events occurring with spatial scale invariance on the specimen, over millions of years.

Automated High-Resolution Imaging of Very Large Fields of View (FOV)

Abstract Engineers at IBM’s Watson Research Center are contending with one of the most fundamental limitations of imaging technology: the tradeoff between spatial resolution and field of view. In this article, they explain how they created tool interfaces, control and automation software, and image analysis and stitching algorithms, enabling photon emission and laser scanning microscopes to produce high-resolution mosaic images of advanced processor cores and other large-area ICs. They describe some of the challenges they faced and explain how their technology can be used to create images based on reflected light, induced voltage, photon emission, and laser stimulation signatures. In one of the latest demonstrations, the technology was used to land and focus a SIL more than 4000 times, acquiring some 16,000 images that were composed into stitched mosaics of several hundred images each.