Large-format Images Research Articles

Spatially Resolved Event-Driven 24 × 24 Pixels SPAD Imager With 100% Duty Cycle for Low Optical Power Quantum Entanglement Detection

Quantum microscopy requires efficient detectors able to identify temporal correlations among photons. Photon coincidences are usually detected by postprocessing their timestamps measured by means of time-to-digital converters (TDCs), through a time and power-consuming procedure, which impairs the overall system performance. In this article, we propose an innovative single-photon sensitive imager based on single-photon avalanche diodes (SPADs), able to signal coincident photon pairs along with their position through a TDC-free, event-driven architecture. The result is a highly efficient detector (25.8%) with a 100% duty cycle and minimized data throughput. The modular architecture and the 330 ns readout time, independent of pixel number, pave the way to large format imagers based on the same paradigm. The detector enabled quantum imaging at extremely low, microwatt-level optical pump powers, four orders of magnitude lower than previous experiments with similar optical setups.

Improved High-resolution Fast Imager

The improved High-resolution Fast Imager (HiFI+) is a multiwavelength imaging filtergraph, which was commissioned at the GREGOR solar telescope at Observatorio del Teide, Izaña, Tenerife, Spain, in March 2022 – followed by science verification in April 2022, after which it entered routine observations. Three camera control computers with two synchronized sCMOS and CMOS cameras each provide near diffraction-limited imaging at high cadence in six wavelength bands (Ca ii H at 396.8 nm, G-band at 430.7 nm, blue continuum at 450.6 nm, narrow- and broad-band Hα at 656.3 nm, and TiO bandhead at 705.8 nm). This unique combination of photospheric and chromospheric images provides “tomographic” access to the dynamic Sun and complements spectropolarimetric observations at the GREGOR telescope. High image acquisition rates of 50 and 100 Hz facilitate image restoration, where time series of restored images have a typical cadence of 6 and 12 s, which is sufficient to resolve the dynamics of the solar photosphere and chromosphere. In principle, all imaging channels can be restored individually using the speckle masking technique or multiframe blind deconvolution (MFBD). However, images recorded strictly simultaneously in the narrow-/broad-band Hα and the G-band/blue continuum channels can be pairwise subjected to multiobject multiframe deconvolution (MOMFBD) expanding the science capabilities of HiFI+. For example, the narrow-band (FWHM = 60 nm) Halle Hα Lyot filter isolates the Hα line core, which facilitates matching chromospheric fibrils and filamentary structures to photospheric bright points. Likewise, dividing G-band by blue continuum images enhances small-scale brightenings, which are often related to small-scale magnetic fields so that their evolution can be tracked in time. A detailed description of the improved high-cadence, large-format imaging system is presented and its performance is assessed based on first-light observations.

CPAM: Cross Patch Attention Module for Complex Texture Tile Block Defect Detection

Due to the little variation in defect points, tile block defect detection typically detects subtle defects in large-format images, allowing defective characteristics to be displayed regionally. Traditional convolutional neural network architectures that extract regional features take into account the connection between regional features simply, resulting in the presence of region-specific bias, which makes tile block defect detection still a challenging task. To address this challenge, this paper divides feature information into patches that can represent different regional features. Additionally, the relationship between different patches and tile block defects is studied; as a result, this paper proposes a new attention mechanism called the Cross Patch Attention Module (CPAM). Since the regional performance of patches is consistent with the tile block defect characteristics, CPAM can distinguish various regional features by patches. Then, in order to create reliable one-dimensional patch information, CPAM provides a method to connect patches linearly in two spatial directions. This takes into account the correlation of adjacent patches in various spatial directions. Finally, by extracting the regional characteristics of patches, CPAM can successfully assist the model in distinguishing the importance of different patches. The experimental results demonstrate that CPAM has excellent performance for tile block defect detection, and plugging CPAM into different end-to-end models can have a good gain effect, which can effectively and stably help the model to complete the task of tile block defect detection.

Direct Optical Lithography Enabled Multispectral Colloidal Quantum-Dot Imagers from Ultraviolet to Short-Wave Infrared.

Complementary metal oxide semiconductor (CMOS) silicon sensors play a central role in optoelectronics with widespread applications from small cell phone cameras to large-format imagers for remote sensing. Despite numerous advantages, their sensing ranges are limited within the visible (0.4-0.7 μm) and near-infrared (0.8-1.1 μm) range , defined by their energy gaps (1.1 eV). However, below or above that spectral range, ultraviolet (UV) and short-wave infrared (SWIR) have been demonstrated in numerous applications such as fingerprint identification, night vision, and composition analysis. In this work, we demonstrate the implementation of multispectral broad-band CMOS-compatible imagers with UV-enhanced visible pixels and SWIR pixels by layer-by-layer direct optical lithography of colloidal quantum dots (CQDs). High-resolution single-color images and merged multispectral images were obtained by using one imager. The photoresponse nonuniformity (PRNU) is below 5% with a 0% dead pixel rate and room-temperature responsivities of 0.25 A/W at 300 nm, 0.4 A/W at 750 nm, and 0.25 A/W at 2.0 μm.

Detection of water conservancy facilities in large-format image combining E-YOLO algorithm and NDWI constraint

Detection of water conservancy facilities in large-format image combining E-YOLO algorithm and NDWI constraint

An Ultra-Low-Cost Large-Format Wireless IoT Camera

This paper documents the design, construction, and experimental evaluation of an ultra-low-cost large-format digital camera. Used lenses that cover formats up to 4x5 can be surprisingly inexpensive, but large-format image sensors are not. By combining 3D printing with cheap components developed for use in IoT (Internet of Things) devices, especially the sub-$10 ESP32-CAM, a digital scanning large-format camera capable of over 2GP resolution can be constructed at very low cost. Despite the large image area, Lafodis160 is literally a wireless IoT device, fully remote controllable via Bluetooth and WiFi. This camera was originally intended to serve as a testbed for novel ways to improve capture quality for scenes that are not completely static during the scan interval, and a brief overview is given of methods employing unusual scan orderings that will be evaluated using it.

Deterministic object tracking using Gaussian ringlet and directional edge features

Challenges currently existing for intensity-based histogram feature tracking methods in wide area motion imagery (WAMI) data include object structural information distortions, background variations, and object scale change. These issues are caused by different pavement or ground types and from changing the sensor or altitude. All of these challenges need to be overcome in order to have a robust object tracker, while attaining a computation time appropriate for real-time processing. To achieve this, we present a novel method, Directional Ringlet Intensity Feature Transform (DRIFT), which employs Kirsch kernel filtering for edge features and a ringlet feature mapping for rotational invariance. The method also includes an automatic scale change component to obtain accurate object boundaries and improvements for lowering computation times. We evaluated the DRIFT algorithm on two challenging WAMI datasets, namely Columbus Large Image Format (CLIF) and Large Area Image Recorder (LAIR), to evaluate its robustness and efficiency. Additional evaluations on general tracking video sequences are performed using the Visual Tracker Benchmark and Visual Object Tracking 2014 databases to demonstrate the algorithms ability with additional challenges in long complex sequences including scale change. Experimental results show that the proposed approach yields competitive results compared to state-of-the-art object tracking methods on the testing datasets.

Using flatbed scanners in the undergraduate optics laboratory—An example of frugal science

We describe the use of a low-cost commercial flatbed scanner in the undergraduate teaching laboratory to image large (∼25 cm) interference and diffraction patterns in two dimensions. Such scanners usually have an 8-bit linear photosensor array that can scan large areas (∼28 cm × 22 cm) at very high spatial resolutions (≥100 Megapixels), which makes them versatile large-format imaging devices. We describe how the scanner can be used to image interference and diffraction from rectangular single-slit, double-slit, and circular apertures. The experiments are very simple to setup and require no specialized components besides a small laser and a flatbed scanner. Due to the presence of Automatic Gain Control in the scanner, which we were not able to override, we were unable to get an excellent fit to the data. Interestingly, we found that the less-than-ideal data were actually pedagogically superior as it forced the students to think about the process of data acquisition in much greater detail instead of simply performing the experiment mechanically.

Development and application of spherically curved charge-coupled device imagers.

Operation of a CCD imager on a curved focal surface offers advantages to flat focal planes, especially for lightweight, relatively simple optical systems. The first advantage is that the modulation transfer function can approach diffraction-limited performance for a spherical focal surface employed in large field-of-view or large-format imagers. The second advantage is that a curved focal surface maintains more uniform illumination as a function of radius from the field center. Examples of applications of curved imagers, described here, include a small compact imager and the large curved array used in the Space Surveillance Telescope. The operational characteristics and mechanical limits of an imager deformed to a 15 mm radius are also described.

Sculpting narrowband Fano resonances inherent in the large-area mid-infrared photonic crystal microresonators for spectroscopic imaging.

Fourier transform infrared (FT-IR) imaging spectrometers are almost universally used to record microspectroscopic imaging data in the mid-infrared (mid-IR) spectral region. While the commercial standard, interferometry necessitates collection of large spectral regions, requires a large data handling overhead for microscopic imaging and is slow. Here we demonstrate an approach for mid-IR spectroscopic imaging at selected discrete wavelengths using narrowband resonant filtering of a broadband thermal source, enabled by high-performance guided-mode Fano resonances in one-layer, large-area mid-IR photonic crystals on a glass substrate. The microresonant devices enable discrete frequency IR (DF-IR), in which a limited number of wavelengths that are of interest are recorded using a mechanically robust instrument. This considerably simplifies instrumentation as well as overhead of data acquisition, storage and analysis for large format imaging with array detectors. To demonstrate the approach, we perform DF-IR spectral imaging of a polymer USAF resolution target and human tissue in the C-H stretching region (2600-3300 cm(-1)). DF-IR spectroscopy and imaging can be generalized to other IR spectral regions and can serve as an analytical tool for environmental and biomedical applications.

3. 大判センサ搭載カメラによる高画質動画

3. 大判センサ搭載カメラによる高画質動画

Tracking Vehicles Through Shadows and Occlusions in Wide-Area Aerial Video

We present a new approach for simultaneous tracking and segmentation of multiple targets in low frame rate aerial video. We focus on building an accurate background model that accounts for both global camera motion and moving objects in the scene. We then apply a probabilistic framework for simultaneous tracking and segmentation that incorporates this background model. By using a background model, we are able to track the object through dramatic appearance changes caused by shadows and lighting changes. Furthermore, the incorporation of segmentation into the tracking algorithm reduces the impact of common tracking problems, such as drift and partial occlusion. Results are shown for the Columbus Large Image Format (CLIF) 2007 data set, demonstrating successful tracking under significant occlusions, target appearance changes, and near similar moving objects.

Pixel-Level Charge and Current Injection Circuit for High Accuracy Calibration of the DSSC Chip at the European XFEL

This work presents the experimental results from the characterization of the second prototype of a high accuracy (in terms of linearity, mismatch and noise) injection circuit to be used for in-pixel calibration of a large sensor matrix. The circuit was designed for the calibration of the pixel cell unit of a hybrid pixel device, the DEPFET Sensor with Signal Compression (DSSC) chip, for the large format imager at the European X-ray Free Electron Laser (XFEL), but, in principle, it can be used also for other kinds of detectors, e.g., deep N-well monolithic CMOS sensors. In the case of hybrid pixels, the injection circuit is particularly useful to test the functionality of the readout electronics already at the chip level, when no sensor is connected to the chip. Two injection techniques have been investigated: one for a charge sensitive amplification and the other for a transresistance readout channel. The aim of the paper is to describe the architecture of the calibration circuit, which has been implemented in a 130-nm CMOS technology, and to present the results from the characterization of the second prototype.

SIFT FOR DENSE POINT CLOUD MATCHING AND AERO TRIANGULATION

Abstract. This paper presents a new method for dense point cloud matching and aero triangulation based on the well-known scale invariant feature transform (SIFT) technique. The modern digital cameras can take high resolution aerial images with high end lap between contiguous images in a strip and, if needed, also with high side lap between images on neighboring strips. Therefore, automation on image matching for generation of high density of 3D object points becomes applicable. A new method is thus developed to perform the processing. Moreover, it can do an aero triangulation and automatic tie point measurement without the need on the input data such as block and strip data for providing image overlap information. In order to increase the effectiveness of the method for simultaneously processing a large number of aerial images with large image format in a block area, both schemes of Quality Filtering (QF) and Affine Transformation Prediction (AFTP) are proposed for automatic tie point extraction and measurement with a better and satisfactory efficiency. Tests are done by using aerial images taken with the RMK DX camera in Taiwan. Also, high precision ground check points are adopted to evaluate the quality of the results. They show that a high density of 3D object points are extracted and determined. Furthermore, the automatic tie point selection and measurement is done efficiently even under the circumstance that no priori-knowledge on image overlap is available. Also, ground check points show that the accuracy of photo coordinates is 0.21 pixels, namely it reaches a subpixel level.

RIGOROUS IMAGE FORMATION FROM AIRBORNE AND SPACEBORNE DIGITAL ARRAY SCANNERS

Abstract. Sensor builders in the digital era have design limitations due to the constraint of maximum available digital array size. A straightforward solution exists, for example, when four cameras that each simultaneously captures an image from essentially the same perspective centre; they can be re-sampled to form a virtual large format image that can be exploited using a single (instead of four separate) instantiation of a frame model. The purpose of this paper is to address the less trivial time-dependent cases where the sensor scans the ground and the detector arrays obtain chips of imagery that need to be stitched together to form a single conveniently exploitable image. Many operational techniques warp the imagery to form a mosaic, or ortho-rectify it using an imperfect digital surface model (DSM), thus eliminating the possibility for accurate geolocation and uncertainty estimation. This algorithm, however, forms a single virtual image with associated smooth metadata, which can be exploited using a simple physical sensor model. The algorithm consists of four main steps: 1) automated tie point matching; 2) camera calibration (once per sensor); 3) block adjustment; and 4) pixel re-sampling based on an "idealized" virtual model. The same geometry model used to form the image, or its true replacement, must be used to exploit it. This paper verifies the algorithm using real imagery acquired from the Global Hawk (GH) UAV. Registration of the virtual image to a WorldView1 stereopair using four tie points yielded an RMS below 0.6 meters per horizontal axis.

THE ULTRACAM STORY

Abstract. The UltraCam-project created a novel Large Format Digital Aerial Camera. It was inspired by the ISPRS Congress 2000 in Amsterdam. The search for a promising imaging idea succeeded in May 2001, defining a tiling approach with multiple lenses and multiple area CCD arrays to assemble a seamless and geometrically stable monolithic photogrammetric aerial large format image. First resources were spent on the project in September 2011. The initial UltraCam-D was announced and demonstrated in May 2003. By now the imaging principle has resulted in a 4th generation UltraCam Eagle, increasing the original swath width from 11,500 pixels to beyond 20,000. Inspired by the original imaging principle, alternatives have been investigated, and the UltraCam-G carries the swath width even further, namely to a frame image with nearly 30,000 pixels, however, with a modified tiling concept and optimized for orthophoto production. We explain the advent of digital aerial large format imaging and how it benefits from improvements in computing technology to cope with data flows at a rate of 3 Gigabits per second and a need to deal with Terabytes of imagery within a single aerial sortie. We also address the many benefits of a transition to a fully digital workflow with a paradigm shift away from minimizing a project's number of aerial photographs and towards maximizing the automation of photogrammetric workflows by means of high redundancy imaging strategies. The instant gratification from near-real-time aerial triangulations and dense image matching has led to a reassessment of the value of photogrammetric point clouds to successfully compete with direct point cloud measurements by LiDAR.

Investigation of the secondary electron emission characteristics of alternative dynode materials for imaging photomultipliers

The requirement to accurately detect and image very high speed photon events is a necessity for many applications across a range of disciplines. Photon imaging detectors often make use of the planar geometry of MCPs for high resolution imaging. However, the inherent rate limitations of MCPs provide opportunities for discrete dynode devices where rapid recharge times and high throughput are required.Novel dynode materials and designs offer the possibility to further improve event time resolution and pulse height distribution. Significant performance advantages can be achieved by increasing the gain of each dynode stage by utilizing materials such as CVD diamond. Secondary electron emission (SEE) coefficients for polycrystalline CVD diamond of 84 have been reported for Hydrogen terminated surfaces and similar values for Cs terminated surfaces [1, 2]. These values are far in excess of currently used materials such as AgMgO(Cs) and CuBeO(Cs) which have SEE coefficients < 15 [3].Polycrystalline diamond is a widely available, relatively inexpensive material that can be deposited over large areas, making the manufacture of large format imaging detectors a practical possibility. The application of new dynode designs for imaging photomultipliers requires knowledge of the secondary electron emission characteristics of the material. We describe a facility to measure the relevant characteristics of novel dynode materials and designs with 2D imaging capability, and discuss the challenges and complexities involved with SEE coefficient measurements. We present secondary electron emission measurements for a variety of dynode materials and designs and discuss their application in imaging photon-counting devices.

大面积X射线分幅变像管的设计

大面积X射线分幅变像管的设计

Novel Terahertz Antenna Based on a Silicon Lens Fed by a Leaky Wave Enhanced Waveguide

We introduce a novel antenna concept suitable for future integrated arrays at terahertz frequencies. The antenna consists of an extended hemispherical lens antenna fed by a leaky wave waveguide feed that can be integrated with sensors and detectors such as Schottky diodes. In this antenna architecture, a couple of TE/TM leaky wave modes are excited in a resonant cavity formed by a waveguide opening ground plane and a silicon lens. Due to these modes, the field radiated by the waveguide inside the lens is a very directive pattern that illuminates the upper part of the lens. Having a directive primary field helps to increase the f-number of the lens improving several factors as spill over, off axis distortions and coating layer fabrication. The antenna structure is compatible with modern semiconductor fabrication technology and lends itself nicely for large format imaging arrays. In this contribution, we investigate the important parameters of a single antenna such as reflection coefficient, directivity, Gaussicity, phase center and off-axis displacement tolerances, and we validate our simulations by measuring the far field radiation patterns of a 545 GHz prototype.

Development and Characterization of New 256$\,\times\,$256 Pixel DEPFET Detectors for X-Ray Astronomy

DEPFET detectors are silicon (Si) active pixel sensors designed and manufactured in the Max-Planck-Institut semiconductor lab. Their high spatial resolution and high energy resolution in X-rays make them attractive for particle tracking in colliders and for X-ray astronomy. This technology is foreseen for the Wide Field Imager of the International X-ray Observatory currently in study with ESA, NASA, and JAXA. New DEPFET matrixes with 256 × 256 pixels of 75-μm pitch have been produced, mounted on ceramic boards with dedicated front-end electronics and integrated in a new setup able to acquire large-format images and spectra. Excellent homogeneity has been observed. Energy resolution as low as 127 eV FWHM at 5.9 keV has been obtained including all single events of the matrix back illuminated at -45<;°C and read out at a 300-frames/s rate. This paper presents experimental methods and results.