Linear Array Detector Research Articles

Focusing Through Scattering Media Via 1D Speckle Signal Feedback

AbstractLight propagation in complex media results in strong scattering. While wavefront shaping (WFS) enables the focusing of light at depth, its speed is mainly limited by the frame rate of the area‐array detectors. The photodetector has been used to achieve fast focusing, but it cannot record sufficient speckle information, limiting its applications in multi‐point focusing and non‐invasive focusing. Here, a method for invasively or non‐invasively focusing through scattering media is proposed by using 1D speckle signals as feedback for wavefront shaping. Experimentally, not only invasive multi‐point focusing can be realized, but also by maximizing the contrast of linear fluorescent 1D speckle signals, non‐invasive focusing can be achieved, suggesting the effectiveness of the proposed method. This approach can be generalized to the utilization of linear array detectors in WFS and may hold interesting prospects for rapid focusing light within deep biological tissues.

Joint segmentation and image reconstruction with error prediction in photoacoustic imaging using deep learning

Deep learning has been used to improve photoacoustic (PA) image reconstruction. One major challenge is that errors cannot be quantified to validate predictions when ground truth is unknown. Validation is key to quantitative applications, especially using limited-bandwidth ultrasonic linear detector arrays. Here, we propose a hybrid Bayesian convolutional neural network (Hybrid-BCNN) to jointly predict PA image and segmentation with error (uncertainty) predictions. Each output pixel represents a probability distribution where error can be quantified. The Hybrid-BCNN was trained with simulated PA data and applied to both simulations and experiments. Due to the sparsity of PA images, segmentation focuses Hybrid-BCNN on minimizing the loss function in regions with PA signals for better predictions. The results show that accurate PA segmentations and images are obtained, and error predictions are highly statistically correlated to actual errors. To leverage error predictions, confidence processing created PA images above a specific confidence level.

Plasmonic Photovoltaic Effect of an Original 2D Electron Gas System and Application in Mid‐Infrared Imaging

AbstractOwing to their consistently emerging applications in modern photonics, highly sensitive and rapid mid‐infrared (MIR) photodetectors, operating at high temperatures, are of great significance. Herein, a novel PbTe/Ge heterostructure is introduced. Notably, the discovery of a 2D electron gas (2DEG) system on the surface of the PbTe layer is experimentally identified for the first time. A high‐performance PbTe/Ge heterostructure MIR photodetector utilizing a plasmonic photovoltaic effect is developed by employing asymmetric electrodes. The photodetecting device demonstrates an exceptionally high detectivity of 1.1 × 1011 Jones along with a short response time of 15 ns at room temperature. Additionally, the proposed plasmonic photovoltaic mechanism of the device is investigated and mainly ascribed to the propagating plasmons, generated by the coupling of the 2DEG with incident MIR photons. Moreover, a linear detector array (LDA) of PbTe/Ge is demonstrated for a thermal imaging application, which exhibits promising high‐quality real‐time imaging via the 2D photodetector arrays on Ge‐based integrated circuits. This work opens up a new way for the development of next‐generation, advanced MIR photonic devices and integrated photonic systems.

Van der Waals mid-wavelength infrared detector linear array for room temperature passive imaging.

Passive imaging for mid-wave infrared (MWIR) is resistant to atmospheric pollutants, guaranteeing image clarity and accuracy. Arrayed photodetectors can simultaneously perform radiation sensing to improve efficiency. Room temperature van der Waals (vdWs) photodetectors without lattice matching have evolved rapidly with optimized stacking methods, primarily for single-pixel devices. The urgent need to implement arrayed devices aligns with practical demands. Here, we present an 8 by 1 black phosphorus/molybdenum sulfide (BP/MoS2) vdWs photodetector linear array with a fill-factor of ~77%, fabricated using a temperature-assisted sloping transfer method. The flat interface and uniform thickness facilitate carrier transport and minimize pixel nonuniformities, showing an average peak detectivity (D*) of 2.34 × 109 cm·Hz1/2·W-1 in the mid-wave infrared region. Compared to a single pixel, push-broom scanning passive imaging is eight times more efficient and further enhanced through mean filtering and fast Fourier transform filtering for strip noise correction. Our study offers guidance on vdWs arrayed devices for engineering applications.

Dose Reduction in Medical Radiography: Advancing Veterinary Diagnostic Solutions

In this study, we investigated photon attenuation using an anti-scatter lead grid with a flat panel detector (FPD) and aimed to mitigate it by implementing a linear array detector (LAD). We developed a mechanical system that facilitates X-ray scans using the LAD. For comparison, we selected a standard FPD unit. To assess the differences in entrance skin dose (ESD) between the LAD and FPD systems, we initially utilized anthropomorphic phantoms, followed by water phantoms for exposure tests. Results showed that at a water depth of 10 cm, the ESD from the LAD was 22% lower than that from the FPD. At 30 cm this ratio was increased up to 40%. As water thickness increased, the benefits of using LAD became more evident, demonstrated by a lower ESD. This finding highlights the potential utility of implementing this equipment in veterinary radiography, particularly for imaging animals and their anatomical sites with thicker tissues.

Dose Reduction in Medical Radiography: Advancing Veterinary Diagnostic Solutions

In this study, we investigated photon attenuation using an anti-scatter lead grid with a flat panel detector (FPD) and aimed to mitigate it by implementing a linear array detector (LAD). We developed a mechanical system that facilitates X-ray scans using the LAD. For comparison, we selected a standard FPD unit. To assess the differences in entrance skin dose (ESD) between the LAD and FPD systems, we initially utilized anthropomorphic phantoms, followed by water phantoms for exposure tests. Results showed that at a water depth of 10 cm, the ESD from the LAD was 22% lower than that from the FPD. At 30 cm this ratio was increased up to 40%. As water thickness increased, the benefits of using LAD became more evident, demonstrated by a lower ESD. This finding highlights the potential utility of implementing this equipment in veterinary radiography, particularly for imaging animals and their anatomical sites with thicker tissues.

High dynamic range spatial heterodyne one-dimensional imaging spectroscopy based on a digital micromirror device

Spatial heterodyne one-dimensional imaging spectrometer (SHIS) can simultaneously acquire hyperspectral information from different fields of view (FOVs). However, the dynamic range of SHIS is limited by the detector's performance. We propose a high dynamic range spatial heterodyne one-dimensional imaging spectroscopy (HD-SHIS) based on a digital micromirror device (DMD), which can control the exposure time of each FOV signal by adjusting the flip time of micromirrors on an M-bit DMD, realizing the simultaneous detection of strong and weak signals in FOVs with a theoretical improvement of the dynamic range by dB. Meanwhile, HD-SHIS utilizes a DMD to realize the Hadamard modulation of interference data in the spectral dimension, which can be used with the linear array detector to complete the detection of the imaging spectrum. We have built an HD-SHIS principle prototype and carried out dynamic range experiments. The experimental results show that HD-SHIS can achieve 48 dB dynamic range improvement by utilizing an 8-bit display width DMD.

Dose Reduction in Medical Radiography: Advancing Veterinary Diagnostic Solutions

In this study, we investigated photon attenuation using an anti-scatter lead grid with a flat panel detector (FPD) and aimed to mitigate it by implementing a linear array detector (LAD). We developed a mechanical system that facilitates X-ray scans using the LAD. For comparison, we selected a standard FPD unit. To assess the differences in entrance skin dose (ESD) between the LAD and FPD systems, we initially utilized anthropomorphic phantoms, followed by water phantoms for exposure tests. Results showed that at a water depth of 10 cm, the ESD from the LAD was 22% lower than that from the FPD. At 30 cm this ratio was increased up to 40%. As water thickness increased, the benefits of using LAD became more evident, demonstrated by a lower ESD. This finding highlights the potential utility of implementing this equipment in veterinary radiography, particularly for imaging animals and their anatomical sites with thicker tissues.

Terahertz fan-beam computed tomography.

A terahertz (THz) fan-beam computed tomography (CT) system using a 0.3 THz continuous-wave sheet beam is proposed. The diffraction-free sheet beam expands in a fan shape in only one direction and provides propagation-invariant focal lines and extended the depth-of-field. The fan-beam CT based on this beam is the second-generation THz CT. It breaks the conventional 4-f symmetric structure of THz CT using the parallel beam. The fan-beam THz CT allows for use with a linear array detector, which reduces the time required to collect data. To demonstrate its feasibility for three-dimensional (3D) imaging, the 3D structure of a metal rod packed in a carton is reconstructed with the support of the system. The results show that the object's internal structure can be obtained by this new THz CT system while retaining the geometrically magnified features of the cross-sectional structure. The results of our research provide a template for the second-generation THz CT system, which provides an additional method for nondestructive testing.

Optical-pump-terahertz-probe spectroscopy in high magnetic fields with kHz single-shot detection.

We demonstrate optical pump-THz probe (OPTP) spectroscopy with a variable external magnetic field (0-9T), in which the time-dependent THz signal is measured by echelon-based single-shot detection at a repetition rate of 1kHz. The method reduces data acquisition times by more than an order of magnitude compared to conventional electro-optic sampling using a scanning delay stage. The approach illustrates the wide applicability of the single-shot measurement approach to non-equilibrium systems that are studied through OPTP spectroscopy, especially in cases where parameters such as magnetic field strength (B) or other experimental parameters are varied. We demonstrate the capabilities of our measurement by performing cyclotron resonance experiments in bulk silicon, where we observe B-field-dependent carrier relaxation and distinct relaxation rates for different carrier types. We use a pair of economical linear array detectors to measure 500 time points on each shot, offering an equivalent performance to camera-based detection with possibilities for higher repetition rates.

Molecular Design of Layered Hybrid Silver Bismuth Bromine Single Crystal for Ultra-Stable X-Ray Detection With Record Sensitivity.

Nowadays, weak interlayer coupling and unclear mechanism in layered hybrid silver bismuth bromine (LH-AgBiBr) are the main reasons for limiting its further enhanced X-ray detection sensitivity and stability. Herein, the design rules for LH-AgBiBr and its influence on X-ray detection performance are reported for the first time. Although shortening amine size can enhance interlayer coupling, its detection performance is severely hampered by its easier defect formation caused by enlarged micro strain. In contrast, an appropriate divalent amine design endows the material with improved interlayer coupling and released micro strain, which benefits crystal stability and mechanical hardness. Another contribution is to increase material density and dielectric constant; thus, enhancing X-ray absorption and carrier transport. Consequently, the optimized parallel device based on BDA2 AgBiBr8 achieves a record sensitivity of 2638 µC Gyair -1 cm-2 and an ultra-low detection limit of 7.4 nGyair s-1 , outperforming other reported LH-AgBiBr X-ray detectors. Moreover, the unencapsulated device displays remarkable anti-moisture, anti-thermal (>150 °C), and anti-radiation (>1000 Gyair ) endurance. Eventually, high-resolution hard X-ray imaging is demonstrated by linear detector arrays under a benign dose rate (1.63 µGyair s-1 ) and low external bias (5V). Hence, these findings provide guidelines for future materials design and device optimization.

Point spread function modeling for photoacoustic tomography - II: two-dimensional detection geometries.

Point spread function (PSF) modeling is important for the characterization of the imaging performance of a photoacoustic computed tomography (PACT) system. This work aims to study the degradation mechanism of PSF in PACT and investigate the impact of the shape of detection geometry on PSF. PSF modeling of three typical two-dimensional detection geometries, including circular, curved, and linear detector arrays, is presented. Based on the non-ideal detection geometries, the effect of detector bandwidth and detector aperture on PSF is also investigated. Moreover, PSFs of each geometry with typical detector bandwidths and typical detector aperture sizes are presented. Experiments are conducted to validate the results. The proposed PSF modeling approach and corresponding results can help predict and interpret the quality of photoacoustic images produced by a practical PACT system. It is beneficial for the design of detector arrays for enhanced imaging performance.

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.

Design and development of a miniature mid-infrared linear variable filter based spectrometer for environmental sensing.

Miniaturized, energy-efficient and application-specific spectral sensing systems promise to be a highly sought-after technology in the coming years, with potential applications in areas such as: distributed sensor systems, IoT devices, mobile autonomous platforms, and many others. We present in this work the design, construction and measurement results of a compact, mid-infrared spectrometer working in the 3 - 4 µm spectral region, attractive for applications requiring the identification of polymer materials. The spectrometer is based on linear-variable filters (LVF) combined with an uncooled HgCdTe linear-detector array (LDA). The design and architecture of the device is described and discussed in the context of miniaturization challenges and constraints. Measured spectra of thin polyimide and polystyrene foils are presented to prove the applicability of the developed device to polymer materials detection and identification.

PO-1753 Feasibility of a linear diode array detector for commissioning of radiotherapy planning system

PO-1753 Feasibility of a linear diode array detector for commissioning of radiotherapy planning system

Feasibility of a Linear Diode Array Detector for Commissioning of a Radiotherapy Planning System

Feasibility of a Linear Diode Array Detector for Commissioning of a Radiotherapy Planning System

Window-Based Energy Selecting X-ray Imaging and Charge Sharing in Cadmium Zinc Telluride Linear Array Detectors for Contaminant Detection

The spectroscopic and imaging performance of energy-resolved photon counting detectors, based on new sub-millimetre boron oxide encapsulated vertical Bridgman cadmium zinc telluride linear arrays, are presented in this work. The activities are in the framework of the AVATAR X project, planning the development of X-ray scanners for contaminant detection in food industry. The detectors, characterized by high spatial (250 µm) and energy (<3 keV) resolution, allow spectral X-ray imaging with interesting image quality improvements. The effects of charge sharing and energy-resolved techniques on contrast-to-noise ratio (CNR) enhancements are investigated. The benefits of a new energy-resolved X-ray imaging approach, termed window-based energy selecting, in the detection of low- and high-density contaminants are also shown.

Advances in High-Energy-Resolution CdZnTe Linear Array Pixel Detectors with Fast and Low Noise Readout Electronics.

Radiation detectors based on Cadmium Zinc Telluride (CZT) compounds are becoming popular solutions thanks to their high detection efficiency, room temperature operation, and to their reliability in compact detection systems for medical, astrophysical, or industrial applications. However, despite a huge effort to improve the technological process, CZT detectors' full potential has not been completely exploited when both high spatial and energy resolution are required by the application, especially at low energies (<10 keV), limiting their application in energy-resolved photon counting (ERPC) systems. This gap can also be attributed to the lack of dedicated front-end electronics which can bring out the best in terms of detector spectroscopic performances. In this work, we present the latest results achieved in terms of energy resolution using SIRIO, a fast low-noise charge sensitive amplifier, and a linear-array pixel detector, based on boron oxide encapsulated vertical Bridgman-grown B-VB CZT crystals. The detector features a 0.25-mm pitch, a 1-mm thickness and is operated at a -700-V bias voltage. An equivalent noise charge of 39.2 el. r.m.s. (corresponding to 412 eV FWHM) was measured on the test pulser at 32 ns peaking time, leading to a raw resolution of 1.3% (782 eV FWHM) on the 59 keV line at room temperature (+20 °C) using an uncollimated 241Am, largely improving the current state of the art for CZT-based detection systems at such short peaking times, and achieving an optimum resolution of 0.97% (576 eV FWHM) at 1 µs peaking time. The measured energy resolution at the 122 keV line and with 1 µs peaking time of a 57Co raw uncollimated spectrum is 0.96% (1.17 keV). These activities are in the framework of an Italian collaboration on the development of energy-resolved X-ray scanners for material recycling, medical applications, and non-destructive testing in the food industry.

A novel multi-view X-ray digital imaging stitching algorithm.

In fan beam X-ray imaging applications, several X-ray images sometimes need to be stitched together into a panoramic image because of the size limitations of the detector. This study aims to propose a novel multi-view X-ray digital imaging stitching algorithm (MVS) based on the CdZnTe photon counting linear array detectors to solve the problem of fan beam X-ray stitching deformation. The panoramic image is generated in four steps including (1) multi-view projection data acquisition, (2) overlapping positioning, (3) weighted fusion and (4) projected pixel value calculation. Images of a globe and foot are scanned by fan beam X-rays and a CdZnTe detector. The proposed method is applied to stitch together the scanned images of the globe. Three other methods are also used for comparison. Finally, this MVS algorithm is also used in the stitching of scanned images of the foot. Compared with the 50% stitching accuracy of other methods, the new MVS algorithm reached a stitching accuracy of 94.4%. Image distortion on the globe and feet is also eliminated and thus image quality is significantly improved. This study proposes a new multi-view X-ray digital imaging stitching algorithm. Study results demonstrate the superiority of this new algorithm and its feasibility in practical applications.

Comparative Long-Wave Infrared Laser-Induced Breakdown Spectroscopy Employing 1-D and 2-D Focal Plane Array Detectors.

Long-wave infrared (LWIR) emissions of laser-induced plasma on solid potassium chloride and acetaminophen tablet surfaces were studied using both a one-dimensional (1-D) linear array detection system and, for the first time, a two-dimensional (2-D) focal plane array (FPA) detection system. Both atomic and molecular infrared emitters in the vicinity of the plasma were identified by analyzing the detected spectral signatures in the infrared region. Time- and space-resolved long-wave infrared emissions were also studied to assess the temporal and spatial behaviors of atomic and molecular emitters in the plasma. These pioneer temporal and spatial investigations of infrared emissions from laser-induced plasma would be valuable to the modeling of plasma evolutions and the advances of the novel LWIR laser-induced breakdown spectroscopy (LIBS). When integrated both temporally (≥200 µs) and spatially using a 2-D FPA detector, the observed intensities and signal-to-noise-ratio (SNR) of single-shot LWIR LIBS signature emissions from intact molecules were considerably enhanced (e.g., with enhancement factors up to 16 and 3.76, respectively, for a 6.62 µm band of acetaminophen molecules) and, in general, comparable to those from the atomic emitters. Pairing LWIR LIBS with conventional ultraviolet-visible-near infrared (UV/Vis/NIR) LIBS, a simultaneous UV/Vis/NIR + LWIR LIBS detection system promises unprecedented capability of in situ, real-time, and stand-off investigation of both atomic and molecular target compositions to detect and characterize a range of chemistries.