Linear Array Scanner Research Articles

Super‐Resolution Reconstruction of Terahertz Image Based on Linear Array Scanning Imaging

Super‐Resolution Reconstruction of Terahertz Image Based on Linear Array Scanning Imaging

Overcoming Periodic Stripe Noise in Infrared Linear Array Images: The Fourier-Assisted Correlative Denoising Method.

Infrared linear array detectors frequently experience vertical, low-frequency, and periodic stripe noise during imaging, stemming from electro-mechanical interference. Unlike conventional periodic disturbances, this interference showcases long periodicities and is uniquely columnar in orientation. Its presence, especially within the low-frequency domain, renders conventional filtering techniques ineffective and, at times, detrimental to image quality. Addressing this challenge, we introduce Fourier-Assisted Correlative Denoising (FACD), a correlation-centric denoising approach tailored for such unique interference patterns. This mechanism begins with the capture of a pure background image, inclusive of periodic noise, during the non-uniform correction phase of the infrared detector. Leveraging the noise's frequency domain attributes, we extract a one-dimensional single-cycle noise signal. The infrared image is subsequently segmented into parts, and using the detected noise periodicity, the one-dimensional signals for each segment are computed. By leveraging the correlation between these signals and the benchmark one-dimensional noise pattern, we ascertain the noise profile within each segment. This profile is then employed for spatial domain denoising across the entire image frame. Empirical assessments confirm that the FACD outperforms contemporary denoising techniques by augmenting the peak signal-to-noise ratio by approximately 2.5 dB, underscoring its superior robustness. Furthermore, in light of its specificity to this noise model, FACD rapidly denoises high-resolution real infrared linear array scans, thus meeting the stringent real-time and resolution imperatives of advanced infrared linear array scanning apparatuses.

Research on linear array scanning lidar and photon signal processing technology based on InGaAs single-photon detector

Research on linear array scanning lidar and photon signal processing technology based on InGaAs single-photon detector

Synchronous monitoring of axial vibration and rotation speed of rotating cylinder by linear array scanning

The axial vibration (AV) and rotation speed (RS) signals of a rotating cylinder contain rich condition information. In order to harness such quantitative information, an effective measurement method for synchronous monitoring of the AV and RS is highly desirable. However, traditional approaches are restricted either by limited test distance or multiple isolated sensors, which makes the approaches impractical to synchronously acquire the AV and RS signals through a single device. In this paper, a generalized visual measurement method for synchronous monitoring of the AV and RS via linear array scanning (LAS) is proposed. The basic idea is to paste a mark containing a printed black continuous bar and a black block (BCBB) on the surface of a rotating cylinder, and use a linear array camera to synchronously sample the bar and blocks. For the extraction of mark edges, we propose a single edge pixel extraction method through gray gradient of row pixels based on the observation of relatively stable gray level distribution. Line scanned signals disturbed by seam error or axial offset are automatically corrected through seam compensation and axial offset correction respectively. Experimental validation of the proposed method is presented for the cylinder under static hammering, variable speed condition and steady speed condition at a scanning distance of 500 mm. Bilinear interpolation is applied to the scanned linear array images before extracting the edge features and helps improve measurement accuracy. Analyses in the time domain and frequency domain verify the effectiveness of the LAS. The average error between the RS signal obtained by LAS and the reference value is 0.1420 rpm. The correlation coefficient between the AV time-domain signal of LAS and the reference signal is up to 0.900 and the resonance frequency error in the frequency spectrum is less than 1 Hz.

A Low-Profile and Beam-tilted Continuous Transverse Stub Array Antenna at W-band

This paper presents a low-profile, high gain, beam-tilted continuous transverse stub (CTS) array antenna at W-band. The antenna compromises 32 radiating slots and is fed by a parallel plate waveguide (PPW) network with a linear source generator. To deflect the outgoing beam, the principle of linear array scanning is adopted to design inverted T-type structure in each stub to introduce wave path difference. PPW network allows the antenna to obtain lower profile compared to other transmission lines. The design procedure, and the antenna characterization are described. The main beam of the antenna is titled 12 degree in H-plane. The simulation and measured results show that this antenna achieves peak gain of 32.4 dB and a 12 degree beam tilt angle at 99GHz. S11 parameters of the antenna is less than -10 dB in a broadband from 96 GHz to 103 GHz. This antenna has an advantage of miniaturization over other high-gain antenna solutions. The promising performance of this proposed CTS antenna reveals the possible candidate for Millimeter wave (MMW) telecommunication applications.

THz linear array scanner in application to the real-time imaging and convolutional neural network recognition

Room temperature linear arrays (up to 160 detectors in array) from silicon metal- oxide-semiconductor field-effect transistors (Si-MOSFETs) have been designed for sub- THz (radiation frequency 140 GHz) close to real-time direct detection operation scanner to be used for detection and recognition of hidden objects. For this scanner, the optical system with aspherical lenses has been designed and manufactured. To estimate the quality of optical system and its resolution, the system modulation transfer function was applied. The scanner can perform real-time imaging with the spatial resolution better than 5 mm at the radiation frequency 140 GHz and contrast 0.5 for the moving object speed up to 200 mm/s and the depth of field 20 mm. The average dynamic range of real time imaging system with 160-detector linear array is close to 35 dB, when the sources with the output radiation power of 23 mW (IMPATT diodes) are used (scan speed 200 mm/s). For the system with 32-detector array, the dynamic range was about 48 dB and for the single-detector system with raster scanning 80 dB with lock-in amplifier. However, in the latter case for obtaining the image with the sizes 20×40 mm and step of 1 mm, the average scanning time close to 15 min is needed. Convolutional neural network was exploited for automatic detection and recognition of hidden items.

GENERIC LINEAR ARRAY SCANNER MODELING OF SPECTRAL IMAGING SYSTEMS CONTAINING LIMITED METADATA

Abstract. The National Geospatial-Intelligence Agency (NGA) designed the Generic Linear Array Scanner (GLAS) model for geopositioning images from both airborne and spaceborne linear array scanning systems, including pushbroom, whiskbroom, and panoramic sensors. Providers of hyperspectral imagery (HSI) historically have not populated products with high fidelity metadata to support downstream photogrammetric processing. To demonstrate recommended metadata population and exploitation using the GLAS model, NGA has generated example HSI products using data collected by NASA’s EO-1 Hyperion sensor and provided courtesy of the U.S. Geological Survey. This paper provides novel techniques for: 1) generating reasonably accurate initial approximations for GLAS metadata as a function of per-image metadata consisting of only timing information and the latitude and longitude values of the four corners of the image; and 2) identifying a vector of adjustable parameters and reasonable values for its a priori error covariance matrix that enable corrections to the metadata during a bundle adjustment. The paper describes applying these techniques to fourteen overlapping Hyperion images of the Alps, running a bundle adjustment as a function of tie points and optional ground control points, and demonstrating superior results to the previous polynomial based approach as quantified by the 3D errors at several ground check points.

Modeling and analyzing point cloud generation in missile-borne LiDAR

The missile-borne LiDAR has an essential prospect in precise guidance. However, the instability of the missile has a significant impact on the precision of LIDAR point cloud, thus modeling and analyzing the influencing factors of point cloud generation is necessary. In this investigation, the authors modeled the point cloud calculation process of missile-borne linear array scanning LiDAR under ideal conditions and analyzed the effect of position change on the field of view (FOV) in the course of platform motion. Subsequently, the authors summarized that the stability concerning the field of view and the target tracking are dependent on three limiting conditions. Finally, the authors derived an error formula and analyzed several typical errors in missile platform flight, including scanner error, POS error, system integration error, and platform vibration error. Based on theoretical analysis and simulation experiments, the model proposed in this paper can provide a theoretical basis for the design of the missile-borne LiDAR system and the selection of related instruments in practice.

Analysis of the Factors Affecting Airborne Digital Sensor Image Quality

Over the past decade, airborne digital sensor series linear array scanners, among the most important imaging sensors in photogrammetry practices, have been used around the world to measure and interpret the terrain. They have attracted much interest from researchers in image quality and data processing and application. This paper analyzes the factors affecting the quality of airborne digital sensor images and proposes suggestions for data acquisition and flight plan design. Factors affecting image geometric quality are first analyzed theoretically, including the velocity and attitude variations of aircraft, and terrain elevation changes and slope, and formulas are given to express the quantitative relationship. Then, a real data set is used to verify the theoretical analysis and evaluate the practical influence, and according to the formulas, advice on image data acquisition control and flight plan design is provided, so as to improve image quality and facilitate subsequent works.

Εφαρμογές της υπερηχοτομογραφίας στα μηρυκαστικά (ΠΙ): μαστός και γεννητικό σύστημα αρσενικών ζώων - Βιβλιογραφική ανασκόπηση

The main advantage of ultrasonography for examination of the udder, the teats and the genital system of male ruminants is the ability for real time observation of the respective anatomical region, with no need of invasive procedures and with the benefit to image superficial and deeper anatomical structures. For the examination of these two systems, one can use linear array and sector scanner probes with frequencies 3.5-12.0 MHz for udder/teats and 5.0-7.5 MHz for the genital system of male ruminants. The method and the direction of the probe differ depending on the organ being examined and the image observed can differ depending on the organ and the presence of abnormalities. Main pathological conditions that can be diagnosed ultrasonographically are in the udder mastitis, haematomas and foreign bodies and in the teats stenosis, inflammatory lesions, milkstones or foreign bodies, haematomas and abscesses. Pathological conditions in the genitalia of male ruminants, including orchitis, testicular cysts, epididymitis, abscesses, haematomas and tumours, can also be diagnosed ultrasonographically.

QUASI-EPIPOLAR RESAMPLING OF HIGH RESOLUTION SATELLITE STEREO IMAGERY FOR SEMI GLOBAL MATCHING

Abstract. Semi-global matching is a well-known stereo matching algorithm in photogrammetric and computer vision society. Epipolar images are supposed as input of this algorithm. Epipolar geometry of linear array scanners is not a straight line as in case of frame camera. Traditional epipolar resampling algorithms demands for rational polynomial coefficients (RPCs), physical sensor model or ground control points. In this paper we propose a new solution for epipolar resampling method which works without the need for these information. In proposed method, automatic feature extraction algorithms are employed to generate corresponding features for registering stereo pairs. Also original images are divided into small tiles. In this way by omitting the need for extra information, the speed of matching algorithm increased and the need for high temporal memory decreased. Our experiments on GeoEye-1 stereo pair captured over Qom city in Iran demonstrates that the epipolar images are generated with sub-pixel accuracy.

Ultrasound imaging of the coefficient of nonlinearity

Cardiac ablation (CA) is increasingly used to treat atrial fibrillation. However, long-term success is relatively low, and the procedure carries serious risks. To this end, we are developing a β (coefficient of nonlinearity) imaging method that may be employed to perform both tissue characterization and real time temperature estimation to respectively plan, monitor, and execute optimal CA. Starting from a one-dimensional generalized form of the Westervelt equation, we derived an analytical procedure for extracting β which is then further adapted to echo-mode. To evaluate the method performances, in-silico and in-vitro experiments were performed. First, one- to three-dimensional simulations including linear array scanning of three-dimensional objects were obtained with the INCS method. Next, the ULA-OP scanner was used with an Esaote LA332 linear-array to image a phantom consisting of 2-layers obtained as a mixture of oil, gelatin and water. Varying the percentage of oil (β similar to fat), different β values were obtained for the two layers. Both in-silico and in-vitro results show the capability of the method to estimate β variations. Compared to existing methods, the proposed approach provides more stable estimations (spatially) and does not require a special transducer or set-up, being more easily applicable in a clinical setting.

REAL TIME PROCESSING FOR EPIPOLAR RESAMPLING OF LINEAR PUSHBROOM IMAGERY BASED ON THE FAST ALGORITHM FOR BEST SCAN LINE SEARCHING

Abstract. The epipolar resampling of linear pushbroom imagery is essential for automatic DEM extraction and feature collection. Due to the special imaging geometry of linear array scanners, the epipolar geometry of linear pushbroom imagery is very complex. In this paper, a fast algorithm for epipolar resampling of linear pushbroom imagery is proposed which can satisfy the real time processing demand of automatic DEM extraction and feature collection. The differential rectification of linear pushbroom imagery based on the rigorous geometric model is the basis for epipolar resampling. The back projection of ground points is essential for the differential rectification of linear pushbroom imagery and its main objective is searching the best scan line. The traditional best scan line searching methodology based on collinearity equation iterations needs a lot of calculation which has little practical use. According to the geometric constraints of the central perspective plane of scan line, the best scan line is determined efficiently within several iterations which just calculating the distance of ground point to the central perspective planar in object space. Based on our fast back projection algorithm, the epipolar resampling processing efficiency of linear pushbroom imagery can be improved greatly. The ADS40 airborne linear pushbroom imagery is tested and experiment results show that our algorithm has the merits of both high accuracy and efficiency which is suitable for real time processing of epipolar resampling.

High-Resolution Sonographic Measurement of Normal Temporomandibular Joint and Masseter Muscle

Objective The purpose of this study was to measure the width of the temporomandibular (TM) joint capsule and the thickness of the masseter muscle (MM), with high resolution ultrasound in patients without TM-joint-associated diseases. Methods From April 8, 2011 to June 10, 2011, 42 patients without TM disorders were recruited and examined with a real-time 12-MHz linear-array scanner. The maximum thickness of capsular width of the TM joint was measured in the closed mouth position. The thickness of MM was also measured at both rest and maximum contraction. Results A total of 84 joints were included. The mean (± standard deviation) TM joint capsular width was 1.9 ± 0.4 mm; MM thickness at rest was 9.0 ± 1.9 mm; and MM thickness during occlusion on maximal force was 11.8 ± 2.8 mm with an increased ratio of 33 ± 25%. No significant differences were found with regard to the laterality in TM joint capsular width, MM thickness at rest and during maximal occlusion, or augmented MM thickness ratio. There was no difference in the increased ratio of MM between sex, however, the MM thickness at rest and during maximal occlusion was greater in male than in female patients. Conclusion High-resolution ultrasound is an alternative noninvasive method for the evaluation of the TM joint. Sex should be considered in clinical judgment for evaluating MM thickness.

Epipolar Resampling and Epipolar Geometry Reconstruction of Linear Array Scanner Scenes Based on RPC Model

In view of the nonexistence of geometric model for epipolar image,this paper,based on the RPC model,puts forward a practical way of building geometric model from epipolar image generated by the projection track method.With the support of across-track stereo image data of SPOT 5 HRG,CBERS 2-03 and along-track stereo image data of SPOT 5 HRS,P5,GeoEye,IKONOS,this paper indicates that the RMS of vertical parallax of the epipolar image is within 0.2 pixel,that the planar RMS calculated from forward intersection by the epipolar model and the original image model is within 1m,and that the altitude RMS is within 0.3 m.

Evaluation of ultrasound as a tool for etiological diagnosis of painful arc syndrome

Abstract To evaluate the role of ultrasonography as a tool for etiological diagnosis of painful arc syndrome. Fifteen consecutive patients of painful arc syndrome were evaluated clinically and by ultrasonography. The patients were scanned using a high resolution linear array scanner with a 7.5-12.5 MHz (ATL HDI 5000, Munich) linear transducer. The patients were managed by open acromioplasty and the pre-operative sonographic findings were correlated with the surgical findings. The age of patients ranged from 32 years to 68 years, with an average age of 50 years. The majority of the patients were females (73.3%). Duration of symptoms ranged from 3 months to 10 years, with average duration being 15.9 months. The ultrasound was able to detect all full thickness tears and partial thickness tears that were identified during surgery with 100% sensitivity and 100% negative predictive value and 66.7% accuracy. The authors feel that ultrasound is an accurate and reliable imaging modality for diagnosis and classification of rotator cuff tears and subacromial impingement.

Quantitative determination of blood flow in the internal jugular vein using ultrasound

The cross-sectional area of the internal jugular vein was measured in 8 normal healthy subjects and in two patients having AV malformations in the internal carotid circulation using a linear-array scanner with facilities for computerised planimetry. Mean blood flow velocity was measured at the same site of the vessel by means of continuous-wave Doppler flowmeter. The product of the two values was considered to indicate volume flow. The mean value for bilateral flow was 656 +/- 113 ml/min in the normal series. In the two patients the values were 1 331 ml/min and 860 ml/min respectively.

Epipolar Resampling of Space-borne Linear Array Scanner Scenes Using Parallel Projection

Epipolar resampling aims at generating normalized images where conjugate points are located along the same row. Such a characteristic makes normalized imagery important for many applications such as automatic image matching, aerial triangulation, DEM and ortho-photo generation, and stereo-viewing. Traditionally, the input media for the normalization process are digital images captured by frame cameras. These images could be either derived by scanning analog photographs or directly captured by digital cameras. Current digital frame cameras provide smaller format imagery compared to those of analog cameras. In this regard, linear array scanners are emerging as a viable substitute to two-dimensional digital frame cameras. However, linear array scanners have more complex imaging geometry than that of frame cameras. In general, the imaging geometry of linear array scanners produces non-straight epipolar lines. Moreover, epipolar resampling of captured scenes according to the rigorous model, which faithfully describes the imaging process, requires the knowledge of the internal and external sensor characteristics as well as a Digital Elevation Model (DEM) of the object space. Recently, parallel projection has emerged as an alternative model approximating the imaging geometry of high altitude scanners with narrow angular field of view. In contrast to the rigorous model, the parallel projection model does not require the internal or the external characteristics of the imaging system and produces straight epipolar lines. In this paper, the parallel projection equations are modified for better modeling of linear array scanners. The modified parallel projection model is then used to resample linear array scanner scenes according to epipolar geometry. Experimental results using Ikonos and SPOT data demonstrate the feasibility of the proposed methodology.

Dodecameric Structure of the Small Heat Shock Protein Acr1 from Mycobacterium tuberculosis

Small heat shock proteins are a ubiquitous and diverse family of stress proteins that have in common an alpha-crystallin domain. Mycobacterium tuberculosis has two small heat shock proteins, Acr1 (alpha-crystallin-related protein 1, or Hsp16.3/16-kDa antigen) and Acr2 (HrpA), both of which are highly expressed under different stress conditions. Small heat shock proteins form large oligomeric assemblies and are commonly polydisperse. Nanoelectrospray mass spectrometry showed that Acr2 formed a range of oligomers composed of dimers and tetramers, whereas Acr1 was a dodecamer. Electron microscopy of Acr2 showed a variety of particle sizes. Using three-dimensional analysis of negative stain electron microscope images, we have shown that Acr1 forms a tetrahedral assembly with 12 polypeptide chains. The atomic structure of a related alpha-crystallin domain dimer was docked into the density to build a molecular structure of the dodecameric Acr1 complex. Along with the differential regulation of these two proteins, the differences in their quaternary structures demonstrated here supports their distinct functional roles.

Analysis of Epipolar Geometry in Linear Array Scanner Scenes

AbstractResampled imagery according to epipolar geometry, usually denoted as normalised imagery, is characterised by having conjugate points along the same row (or column). Such a characteristic makes normalised imagery an important prerequisite for many photogrammetric activities such as image matching, automatic aerial triangulation, automatic digital elevation model and orthophoto generation, and stereo viewing. The normalisation process requires having the input imagery in a digital format, which can be obtained by scanning analogue photographs or by direct use of digital cameras. To reduce the time gap between the data acquisition and product delivery, many small‐scale mapping projects now rely on digital cameras. Digital frame cameras still, in general, provide imagery with geometric resolution and ground coverage inferior to scanned images from analogue cameras. Linear array scanners (line cameras) have therefore emerged as a possible alternative to digital frame cameras, especially for high‐resolution space‐borne imaging, with performance comparable to that of analogue frame cameras.The normalisation process of frame images is a well‐established and straight forward procedure. On the other hand, the normalisation process of linear array scanner scenes is not as straightforward and is sometimes mysterious. For example, providers of space‐borne imagery furnish normalised line scanner imagery while the user community is not aware of the underlying process. This paper presents a comprehensive analysis of the epipolar geometry in linear array scanner scenes. Special emphasis is directed towards scanners moving with constant velocity and attitude since such a trajectory closely resembles the imaging geometry of the majority of current space‐borne scanners. The research presented highlights the factors affecting the shape of the resulting epipolar lines such as the stereo coverage configuration and the geometric specifications of the imaging system. In addition, the paper outlines a comparative analysis of the normalisation process for frame and line cameras. The presented concepts are verified through experimental results with synthetic data.