Digital Pixel Research Articles

Characterization results of MAPS digital prototypes for the ALICE ITS3

The three innermost layers of the ALICE Inner Tracking System (ITS2) will be replaced by a truly cylindrical tracker, the ITS3, to be ready for LHC Run 4 (2029-2032). The ITS3 will be composed of three layers, each made by two self-supporting, ultra-thin (≤50μm) flexible Monolithic Active Pixel silicon Sensors (MAPS) of large area (O(10 × 26 cm2)). The final sensor will be realized using the 65 nm CMOS imaging process and stitching technology. Multiple small-scale test structures were included in the first production run (Multiple Layer Reticle 1 - MLR1) to validate the 65 nm CMOS imaging technology. First large-scale stitched MAPS were included in the second production run (Engineering Run 1 - ER1). The pixel cell performance has been qualified on the MLR1 Digital Pixel Test Structures (DPTS) in laboratory and with in-beam measurements. The large-area (1.4 × 25.9 cm2) ER1 MOnolithic Stitched Sensor (MOSS) prototype has been used to prove the stitching principle and evaluate the detection efficiency and spatial resolution. This contribution will give an overview of the most recent results of the digital prototype tests.

A heterogenous integrated neural recording system with elastocapillary self-assembled Au-PDMS-PEG neural probe and customized ASIC

Abstract This study presents the design and implementation of a heterogenous integrated neural recording system consisting of a flexible Au-PDMS-PEG probe and customized complementary metal oxide semiconductor (CMOS) application-specific integrated circuit (ASIC) in a standard 0.18 μm process. The flexible Au-PDMS-PEG probe was prepared by an elastocapillary self-assembled process, achieving an electrode impedance of 250 kΩ (@1 kHz). The customized CMOS ASIC contains 36 modular digital pixels (MDP). It achieves 5.69 μVrms input referred noise, 10.29 effective number of bits, 49.5 μW power consumption, and 0.092 mm2 area for a single MDP unit. Spontaneous spikes were also recorded in the mouse cortex, with a peak-to-peak amplitude of 389.2 μVPP and a signal-to-noise ratio of 19.36. Benchtop and in-vivo experiments were conducted to validate the functionality and performance of the proposed neural recording system.

Comparison of hypospadias phenotype pixel segmentation to GMS score

Hypospadias phenotype assessment determines if the anatomy is favorable for reconstruction. Glans-Urethral Meatus-Shaft (GMS) has been adopted in an effort to standardize hypospadias classification. While extremely subjective, GMS has been widely used to classify the severity of the phenotype to predict surgical outcomes. The use of digital image analysis has proven to be feasible and prior efforts by our team have demonstrated that machine learning algorithms can emulate an expert's assessment of the phenotype. Nonetheless, the creation of these image recognition algorithms is highly subjective. In order to reduce a subjective input in the evaluation of the phenotype, we propose a novel approach to analyze the anatomy using digital image pixel analysis and to compare the results using the GMS score. Our hypothesis is that pixel cluster segmentation can discriminate between favorable and unfavorable anatomy. To evaluate whether image segmentation and digital pixel analysis are able to analyze favorable vs unfavorable hypospadias anatomy in a less subjective manner than GMS score. A total of 148 patients with different types of hypospadias were classified by 1 of 5 independent experts following the GMS score into "favorable" (GG), "moderately favorable" (GM) and "unfavorable" (GP) glans. From there, 592 images were generated using digital image segmentation. 584 were included for final analysis due to certain images being excluded for poor image quality or inadequate capture of target anatomy. For each image, the region of interest was segmented separately by two evaluators into "glans," "urethral plate," "foreskin" and "periurethral plate". The values obtained for each segmented region using machine-learning statistical pixel k-means cluster analysis were analyzed and compared to the GMS score given to that image using an ANOVA analysis. Analysis of image segmentation demonstrated that k-means pixel cluster analysis discriminated "favorable" vs "unfavorable" urethral plates. There was a significant difference between scores when comparing the GG and GM groups (p=0.03) and GG and GP groups (p=0.05). Pixel cluster analysis could not discriminate between "moderately favorable" and "unfavorable" urethral plates. Through our analysis, we found significant pairwise difference for different tissue qualities. Digital image segmentation and statistical k-means cluster analysis can discriminate anatomical features in a similar way to the GMS score. Future research can target discerning between different tissue qualities in an effort to predict surgical outcomes for hypospadias repair.

A 1024-Channel 268 nW/pixel 36×36 μm2/channel Data-Compressive Neural Recording IC for High-Bandwidth Brain-Computer Interfaces.

This paper presents a data-compressive neural recording IC for single-cell resolution high-bandwidth brain-computer interfaces. The IC features wired-OR lossy compression during digitization, thus preventing data deluge and massive data movement. By discarding unwanted baseline samples of the neural signals, the output data rate is reduced by 146× on average while allowing the reconstruction of spike samples. The recording array consists of pulse position modulation-based active digital pixels with a global single-slope analog-to-digital conversion scheme, which enables a low-power and compact pixel design with significantly simple routing and low array readout energy. Fabricated in a 28-nm CMOS process, the neural recording IC features 1024 channels (i.e., 32 × 32 array) with a pixel pitch of 36 μm that can be directly matched to a high-density microelectrode array. The pixel achieves 7.4 μVrms input-referred noise with a -3 dB bandwidth of 300-Hz to 5-kHz while consuming only 268 nW from a single 1-V supply. The IC achieves the smallest area per channel (36 × 36 μm2) and the highest energy efficiency among the state-of-the-art neural recording ICs published to date.

4차산업혁명이 낳은 융합예술 디카시의 메타포에 관한 연구

As the origin theory of Dicash, I place it in the theory of the yin and yang of the East. Therefore, while the philosophical ideas expressed in Dicash are based on the idea of Cheonji, the idea of Cheonji was verified by limiting it to the collection of Dicapoem published within three years. “Dicapoem a combination of the digital camera Digital pixel, picture element and Poem, is an independent genre of competitive fusion art that overtakes Photo Poem and walks the cutting edge of the Fourth Industrial Revolution. It has been listed as a new literary term in the Korean language spring of the National Institute of the Korean Language.” In the digital age, poetry is accepted in various ways from writing art to video language, but it can be said that decasi is unique and representative in writing poetry using digital cameras as a tool. Photographic poetry has a history of about 200 years. Dicapoem an independent genre of convergent art, has a history of over 20 years. The founder of decasi was Professor Lee Sang-ok. In addition, since the publication of the first digital poetry collection Lee Sang-ok's 『Goseonggado (Hall of Literature, 2004』 in 2004, discussions on decasi have spread not only in Korea, but also in Asia and around the world. Conventional photographic poetry is an analog method that combines photography and poetry. On the other hand, decasi is a digital method that combines digital cameras and poetry. The text was a collection of digital poems by three people, Lee Gyeong-soon, Son Gye-guk, and Kim Sun-mi. Each of their decasi collections was made in connection with the Cheon In-ji ideology. I described with an emphasis on the scalability of Dicapoem. As digital literature, Dicapoem can be said to be a gift of God born by the digital revolution, and it can be confirmed that Dicapoem expresses the metaphor of 'the sky', 'people' and 'the land'.

First measurements with monolithic active pixel test structures produced in a 65 nm CMOS process

The Inner Tracking System (ITS) of the ALICE experiment at CERN will undergo an upgrade during the LHC long shutdown 3, in which the three innermost tracking layers will be replaced. This upgrade, named the Inner Tracking System 3 (ITS3), employs stitched wafer-scale Monolithic Active Pixel Sensors fabricated in a 65 nm CMOS process. The sensors are 260 mm in length and thinned to less than 50 μm then bent to form truly half-cylindrical half-barrels. The feasibility of this process for the ITS3 was explored with the first test production run (MLR1) in 2021, whose goal was to evaluate the charged particle detection efficiency and the sensor performance under non-ionising and ionising radiation up to the expected levels for ALICE ITS3 of 1013 1 MeV neq cm-2 (NIEL) and 10 kGy (TID). Three sensor flavours were produced to investigate this process: Analog Pixel Test Structure (APTS), Circuit Exploratoire 65 (CE65) and Digital Pixel Test Structure (DPTS).This contribution gives an overview of the MLR1 submission and test results, describing the different sensor flavours and presenting the results of the performance measurements done with particle beams for various chip variants and irradiation levels.

Ink to Pixel: Wattpad as a Pedagogical Tool for English Literature in India

Digital Humanities is a burgeoning field where traditional ink converges into digital pixels. Descending from the field of computing humanities data, the scholarly activity continues to produce innovative projects. As far as digital pedagogy is considered, the 2012 edition of Debates in the Digital Humanities shed light on the state of pedagogy as a neglected stepchild of Digital Humanities. But with technological innovations, various digital pedagogical tools have emerged in the past decades. Post Covid-19 lot of digital pedagogical tools have been recognized by educators as part of teaching methodologies. In India, teaching methodologies have evolved to a significant degree from traditional teaching to digital classrooms. Lot of innovative methodologies are employed by the faculties to enhance students’ learning and performance. English Literature is one of the most sought out humanities programs offered in Indian Education Institutions. When it comes to Literature teaching, professors employ various teaching methodologies including e- teaching, where digital tools are being employed. The paper aims to establish Wattpad, a digital platform for writing and reading stories, as a pedagogical tool for English Literature in India. This digital storytelling platform provides a space for the students’ literary expression where they can read and write literary pieces and get real time feedback from users which boosts interactivity. By using this digital pedagogical tool English Literature students are encouraged to apply their literary skills by employing what they have learnt during their course to produce literary works.

An Efficient Audio Encryption Scheme Based on Elliptic Curve over Finite Fields

Elliptic curve (EC) based cryptographic systems are more trustworthy than the currently used cryptographic approaches since they require less computational work while providing good security. This paper shows how to use an EC to make a good cryptosystem for encrypting digital audio. As a preliminary step, the system uses an EC of a particular type over a binary extension field to distort the digital audio pixel position. It reduces the inter-correlation between pixels in the original audio, making the system resistant to statistical attacks. In creating confusion in the data, an EC over a binary extension field is used to make a different number of substitution boxes (S-boxes). The suggested design employs a unique curve that relies on efficient EC arithmetic operations in the diffusion module. As a result, it generates high-quality pseudo-random numbers (PRNs) and achieves optimal diffusion in encrypted audio files with less processing work. Audio files of various sizes and kinds can all be encrypted using the provided algorithm. Moreover, the results show that this method effectively protects many kinds of audio recordings and is more resistant to statistical and differential attacks.

Digital pixel test structures implemented in a 65 nm CMOS process

The ALICE ITS3 (Inner Tracking System 3) upgrade project and the CERN EP R&D on monolithic pixel sensors are investigating the feasibility of the Tower Partners Semiconductor Co. 65nm process for use in the next generation of vertex detectors. The ITS3 aims to employ wafer-scale Monolithic Active Pixel Sensors thinned down to 20–40µm and bent to form truly cylindrical half barrels. Among the first critical steps towards the realisation of this detector is to validate the sensor technology through extensive characterisation both in the laboratory and with in-beam measurements. The Digital Pixel Test Structure (DPTS) is one of the prototypes produced in the first sensor submission in this technology and has undergone a systematic measurement campaign whose details are presented in this article.The results confirm the goals of detection efficiency and non-ionising and ionising radiation hardness up to the expected levels for ALICE ITS3 and also demonstrate operation at ＋20°C and a detection efficiency of 99% for a DPTS irradiated with a dose of 10151MeV neq cm-2. Furthermore, spatial, timing and energy resolutions were measured at various settings and irradiation levels.

Comprehensive multidisciplinary phenotyping of patients with hypospadias. A pilot study

Hypospadias is an abnormal formation of the urethra, ventral skin, and corporal bodies. Location of the urethral meatus has historically been the phenotypic landmark that defines hypospadias. Nonetheless, classifications following location of the urethral meatus fail to consistently predict outcomes and have no correlation with the genotype. Description of the urethral plate is very subjective and difficult to reproduce. We hypothesize that the use of digital pixel cluster analysis and correlation to histological analysis can provide a novel method to describe the phenotype of patients with hypospadias. A standardized hypospadias phenotyping protocol was developed. 1. Digital images of the anomaly, 2. Anthropometric assessment of penile dimensions (penile length, urethral plate length and width, glans width, ventral curvature), 3. Classification using the GMS score, 4. Tissue sampling (foreskin, glans, urethral plate, periurethral ventral skin) and H&E analysis by a blinded pathologist. A k-means colorimetric pixel cluster analysis was performed following the same anatomical landmark distribution as the histology samples. Analysis was performed using MATLAB v R2021b 9.11.0.1769968. A total of 24 patients prospectively enrolled with a standard protocol. Mean age at surgery was 16.25 months Urethral meatus was distal shaft in 7 patients, 8 coronal, 4 glanular, 3 midshaft, 2 penoscrotal. Average GMS score was 7.14 (±1.58). Average glans size was 15.71mm (±2.33) and urethral plate width 5.57mm (±2.06). Eleven patients underwent Thiersch-Duplay repair, 7 TIP, 5 MAGPI, and 1 a first stage preputial flap. Mean follow-up was 14.25 months (±3.7 months). Two (8.3%) postoperative complications (1 urethrocutaneous fistula and 1 ventral skin wound dehiscence) were reported in the study period. Eleven (52.3%) patients with histological analysis had an abnormal pathology report. Of those, 6 (54%) had reported abnormal lymphocyte infiltration interpreted as chronic inflammation at the urethral plate. The second most common finding was hyperkeratosis visualized in the urethral plate in 4 (36.3%) and one with reported fibrosis in the urethral plate. K-means pixel analysis demonstrated a k1 mean of 64.2 for reported urethral plate inflammation vs 53.1 for non-reported urethral plate inflammation (p=0.002) CONCLUSIONS: Current phenotyping of hypospadias using only anthropometric variables can be expanded including histological and pixel analysis correlation. Pixel clustering has a potential for a priori prediction of urethral plate quality beyond the current subjective assessment. A larger cohort will allow identification of possible predictive associations that might impact intraoperative decision-making and surgical outcomes.

An expandable 36‐channel neural recording ASIC with modular digital pixel design technique

AbstractThis paper presents the design and implementation of an expandable neural recording ASIC for multiple‐channel neural recording applications. The ASIC consists of 36 modular digital pixels (MDPs) and a global digital controller (GDC) circuit. Each MDP has an analog frontend (AFE) circuit, a 12‐bit successive approximation register ADC (SAR ADC), and a local digital controller (LDC) circuit. It achieves 5.9‐μV input referred noise (IRN), 10.8‐effective number of bits (ENOB), 37.8‐μW power consumption, and 0.095 mm2 area per channel. The ASIC is implemented in commercial SMIC 0.18‐μm CMOS process and validated by in‐vivo experiment on a lab mouse with a 36‐channel silicon‐based neural probe.

Enhancing the Thermal Images of the Upper Scarp of the Poggio Baldi Landslide (Italy) by Physical Modeling and Image Analysis

We present new methods for physical interpretation and mathematical treatment of the imaging contrast observed in thermal images of the rocky upper scarp of the Poggio Baldi landslide (Italy), which is part of a natural laboratory. Exemplar thermal images have been acquired with a high-performance camera at a distance of around 500 m, in a geometry where reflection is expected to dominate over thermal emission. The digital pixel intensities have therefore been considered as wavelength-integrated infrared spectral reflectance, irrespective of the temperature scale loaded into the camera software. Sub-portions of the scarp producing a lower signal have been identified by a multiscale image segmentation algorithm and overlaid on the visible image to provide an interpretation for the different thermal imaging contrast mechanisms that may be exploited for landslide monitoring in the future.

Design and readout architecture of a monolithic binary active pixel sensor in TPSCo 65 nm CMOS imaging technology

The Digital Pixel Test Structure (DPTS) is a monolithic active pixel sensor prototype chip designed to explore the TPSCo 65 nm ISC process in the framework of the CERN-EP R&D on monolithic sensors and the ALICE ITS3 upgrade. It features a 32 × 32 binary pixel matrix at 15 μm pitch with event-driven readout, with GHz range time-encoded digital signals including Time-Over-Threshold. The chip proved fully functional and efficient in testbeam allowing early verification of the complete sensor to readout chain. This paper focuses on the design, in particular the digital readout and its perspectives with some supporting results.

A readout system for monolithic pixel sensor prototypes towards the upgrade of the ALICE Inner Tracking System

The ALICE experiment at CERN is developing an innovative third iteration of the three innermost layers of the Inner Tracking System (ITS3) to be installed during the Long Shutdown 3 of the LHC (2026–28) [1]. Based on a commercial 65 nm CMOS imaging technology by TowerJazz [2], it consists of truly cylindrical wafer-scale sensors that can be installed as close as 18 mm to the interaction point. In order to validate the technology, several test chips were produced in a first submission named Multi-Layer Reticle 1 (MLR1). This contribution will describe the development, features, and performance of a custom test system for some of the prototypes in MLR1, namely Analogue and Digital Pixel Test Structures (APTS and DPTS, respectively) and pixel matrices with rolling shutter readout (CE65).

Collagen content and C-X-C motif chemokine ligand 12 expression in neoplastic breast stroma.

This study aimed to evaluate the expression of C-X-C motif chemokine ligand 12 and its C-X-C chemokine receptor type 4, and the tumor-stroma ratio using collagen stromal content of breast cancer samples, correlating it with clinicopathological data. Through a retrospective cohort study, samples were obtained from female patients, over 18 years of age, with the disease in stages 1-4, who underwent mastectomy or lumpectomy. The biopsies were provided by the Oncology sector of the Hospital das Clínicas of Universidade Federal de Pernambuco, Recife city, in 2011-2014, including samples of invasive ductal carcinoma, ductal carcinoma in situ, or benign changes (fibroadenoma and hypertrophy), which were analyzed between 2020 and 2022 by immunohistochemistry for the expression of stromal cell characteristics. Collagen content was tested by Gomori staining and digital analysis of images. Absence of stromal expression of C-X-C motif chemokine ligand 12 was associated with longer disease-free survival (disease-free survival=0.481), and expression of C-X-C chemokine receptor type 4 was associated with lower disease-free survival. An association was observed between clinicopathological variables and stromal expression of chemokines, that is, an association of stromal C-X-C motif chemokine ligand 12 with histological grade, angiolymphatic invasion, and an association between C-X-C chemokine receptor type 4 expression and histological grade. Analyses of digital pixels images of collagen and tumor cells showed a lower percentage of collagen in the invasive ductal carcinoma samples (39%), unlike samples without neoplasms (78%). Low expression of C-X-C motif chemokine ligand 12 may be associated with a worse prognosis for breast cancer. Collagen staining analyzed using digital images represents an opportunity for clinical application and is indicative of the prognosis of the tumor microenvironment in breast carcinoma.

A configurable area-efficient LCoS chip design with centrosymmetric pixel array

Liquid Crystal on Silicon (LCOS) is a microdisplay technology that combines CMOS tech with integrated circuit design and liquid crystal technology. In this paper, the proposed LCOS backplane can greatly reduce size of the pixel pitch. In order to reduce the size of the pixel pitch, a digital pixel driver scheme and a new layout design are shown. The proposed LCOS with digital pixel driver scheme was fabricated using 0.18 um CMOS process technology and the simulation image have shown the correct results. The pixel size is 3 um× 6 um in this design and the area of pixel array with the resolution of 1632 × 1632 is 10127 um × 5060 um.

Long-distance mid-wave infrared super-resolution compressive imaging

Super-resolution imaging (SRI) for mid-wave infrared (MWIR) has attracted increasing attention in recent years due to the expensive price for a large number of pixels MWIR cameras. Investigation of the compressed sensing method can partially improves the resolution. However, the quality of SRI is highly related to the transfer function matrix of the optical system, which is difficult to be accurately measured because of the noise existed in MWIR detection, especially in long-distance systems. In this work, we propose a transfer function matrix calculation method which overcomes the issues of low imaging contrast and signal-to-noise ratio compared with previous studies. And we further establish a long-distance focal plane array-based compressive imaging system with a resolution of two digital micro-mirror device pixels which just satisfies the system diffraction limit. In addition, we achieve the 4 × 4 times super-resolution high-quality reconstruction of long-distance digital and physical objects with only six measurements.

A Low-Power and Wide Dynamic Range Digital Pixel Sensor for Intrinsic Optical Imaging in Image-Guided Neurosurgery and Neocortical Epilepsy

Purpose: Determining the borders of brain tumors, seizure foci, and their elimination in patients with brain tumors is very important in preventing cancer recurrence. Multispectral Optical Intrinsic Signal Imaging (MS-OISI) image-guided neurosurgery using visible-Near-Infrared (NIR) wavelengths have shown great potential for image-guided neurosurgery. One of the main challenges is the need for low-power consumption, high-speed and above 100dB dynamic range to capture both visible and NIR photons. The overarching goal of this work is to create a Digital Pixel Sensor (DPS) as a Complementary Metal-Oxide-Semiconductor (CMOS) camera for MS-OISI of the brain in image-guided neurosurgery that has a wide dynamic range, low power consumption, and high speed.
 Materials and Methods: The general view of neurosurgical system, DPS, and circuit operation of conventional Pulsed Frequency Modulation (PFM) DPS are given first. The proposed PFM DPS and circuit implementation are shown, as well as simulation results obtained using a circuit simulator. Finally, a comparison with other similar works is given.
 Results: The proposed pixel simulation results show that the performance parameters such as dynamic range and power consumption has improved in comparison to similar works. However, due to its complicated circuitry, it has a low spatial resolution, which can be compensated.
 Conclusion: The image sensor is post-layout simulated in 0.18μm CMOS technology with a 1.3V supply voltage, resulting in 140dB dynamic range and 7.69μW power dissipation with a 11% fill factor. The key novelty for the proposed PFM DPS is: in-pixel Analog-to-Digital Conversion (ADC), using a low voltage and high-speed dynamic comparator. Furthermore, this work uses a self-reset mechanism, which eliminates the need for an external pulse source, as well as variable reference voltage, which eliminates the necessity for a global constant reference voltage. All of these features demonstrate the excellent potential of the proposed pixel for MS-OISI image-guided neurosurgery.

Quality assessment of digital images produced using handheld X-ray equipment

This study aimed at the assessment and monitoring of digital image quality parameters resulting from the use of portable X-ray equipment in clinical examinations. A multicentric study was conducted for quality assessment of images produced using the portable NOMAD® with the DIGORA® ™ Optime UV computed radiography (CR) system. The digital image quality was evaluated in terms of high- and low-contrast spatial resolution, contrast noise ratio (CNR), and signal-to-noise ratio (SNR). The samples comprised six biomaterials: zirconia (Zr), lyophilized bone (LB), photopolymerizable restorative resin (PRR), glass ionomer cement (GIC), GIC photopolymerizable (GICP), and double adhesive resin cement (DARC). The DICOM image (processed pixels) and raw data (without processing) were quantitatively analyzed. The qualitative visual analysis was performed in an adequately illuminated environment and then repeated in an environment equivalent to that of a clinical practice using conventional monitoring equipment. The relative biomaterial contrast was normalized by the high-contrast result of Zr. The Zr image demonstrated no noise because the standard deviation of the digital image biomaterial pixel mean was zero. In contrast, the relative SNR of the biomaterials was normalized by the DARC result. The relative CNR values according to different aluminum thicknesses were 0.11 for LB and 0.3–0.35 for PRR, GIC, and GICP. The spatial resolution was identical for both high-resolution and conventional monitors; however, for a 0.2-s clinical exposure, the resolution produced by the high-quality monitor increased. The quality control tests indicated the compatibility of the CR system-assisted portable X-ray equipment, verifying the status and image quality.

Visual Cryptography Using Computation-Free Bit-Plane Reconstruction

Visual cryptography (VC) using bit-plane decomposition improves the quality of the reconstructed image. The disadvantage of this scheme is that the decoder needs computation in order to reconstruct the secret image from its bit-planes. To solve this problem, we propose a no-computation bit-plane decomposition visual cryptography (NC-BPDVC). In NC-BPDVC, we convert the grayscale secret image into a multitone image by multilevel halftoning. Then, by exploring the difference between a digital pixel and a printed dot, we design different dot patterns to render a digital pixel. By doing so, we abandon the usual assumption that DPI (dots per inch) equals PPI (pixels per inch) during printing. By adopting the more realistic assumption that DPI can be larger than PPI as is supported by most printers, we use different patterns to render different tone levels. These patterns are carefully designed so that no computation is needed when one needs to reconstruct the multitone image from its bit-planes. Our algorithm is tested on a batch of twenty standard grayscale images. The experimental results confirm the correctness and advantages of the proposed scheme. Compared with the ordinary bit-plane decomposition VC, NC-BPDVC does not need computation. The security of the proposed algorithm is also analyzed and verified.